Stabilizing Interfacial Structure of LiCoO2 with Ultrahigh Capacity and Prolonged Cyclability at 4.6V

Stabilizing Interfacial Structure of LiCoO2 with Ultrahigh Capacity and Prolonged Cyclability at 4.6V | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Stabilizing Interfacial Structure of LiCoO 2 with Ultrahigh Capacity and Prolonged Cyclability at 4.6V Keying Wu, Haiwen Tang, Yao Liu, Dan Wang, Sujun Wang, Jinjin Jiang, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7435444/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 10 You are reading this latest preprint version Abstract LiCoO₂ (LCO) cathodes face severe interfacial degradation ( Co/O loss and structural collapse) at high voltages (>4.6 V), limiting their practical deployment. To address this, we propose a heterojunction engineering strategy via surface coating with lithium zirconium phosphate (Li₂Zr(PO₄)₂, LGPO). The optimized LCO@LGPO cathode achieves an ultrahigh initial discharge capacity of 178.1 mAh·g⁻¹ at 1C (3.0–4.6 V) and retains 86.3% capacity after 200 cycles, outperforming bare LCO (76.0%). It also exhibits enhanced rate capability (108.7 mAh·g⁻¹ at 10C) and near-full capacity recovery (99.7%) when returning to 0.1C. Mechanistic studies reveal that the LGPO coating stabilizes lattice oxygen via robust Zr–O/P–O bonds, suppresses electrolyte decomposition to form a thin inorganic-rich CEI layer, and accelerates Li⁺ diffusion kinetics (DLi⁺ = 8.51 × 10⁻¹² cm²·s⁻¹, 2.4× higher than bare LCO). DFT calculations further confirm that the LCO/LGPO heterojunction reduces oxygen charge compensation and creates an internal electric field to facilitate ion transport while blocking electron leakage. This work provides a scalable surface-modification approach to enable high-energy-density LCO cathodes for next-generation batteries. LiCoO2 Surface coating Heterojunction Structural stability High voltage Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction Currently, LiCoO 2 (LCO) cathode materials are widely used for Li + ion storage due to their typical layered structure [ 1 ], high energy density [ 2 ], and long cycle life [ 3 ]. To achieve higher energy density, researchers have attempted to raise the charging cut off voltage beyond 4.6 V (vs Li/Li + ) to unlock additional capacity [ 4 ]. However, operating at voltages above 4.6 V during cycling causes severe surface Co/O loss and structural degradation [ 5 ], which hinders practical applications. Surface degradation originates from detrimental inter-facial reactions. For instance, during electrolyte charging, solvents like ethylene carbonate (EC) undergo dehydrogenation/oxidation at the LCO/electrolyte interface [ 6 ], generating H + /H 2 O ions that catalyze the hydrolysis of PF 6 − anions into corrosive substances such as HF, HPO 2 , and F 2 , leading to Co dissolution and O loss [ 7 – 10 ]. Additionally, solvent decomposition forms a porous, poorly protective cathode/electrolyte interface (CEI) rich in organic matter. Simultaneously, surface lattice oxygen at voltages above 4.6V in LCO significantly oxidizes and releases as O 2 , exacerbating interfacial side reactions [ 11 ]. The combined effects of O 2 release and Co dissolution cause surface degradation, thereby hindering Li + transport. To address the issue, it is essential to regulate the interfacial reactions between LCO and electrolyte. Strategies include electrolyte tuning and/or surface modification of LCO. In terms of electrolytes, applying fluorinated solvents, high-concentration electrolytes, or additives can optimize CEC performance, resulting in CECs enriched with inorganic species [ 12 ]. For surface modification, reducing direct contact between Co 4+ /O n− (0 < n < 2) on the surface and electrolyte, as well as replacing lattice-Co/O to lower surface oxidation activity, are primary approaches [ 13 , 14 ]. More attention has been focused on interface reactions caused by surface structures, such as using spinel layers or metal oxide coatings [ 15 , 16 ]. However, increased surface impedance and uneven distribution of metal oxides limit cathode performance. Therefore, regulating interface reactions is crucial for achieving excellent cycling stability of LCO under harsh conditions. To address the aforementioned issues and improve the interfacial reaction between LCO and electrolyte, optimizing morphology to enhance the actual lithium-ion diffusion rate in two-dimensional cathode structures has proven most effective through surface coating and bulk doping [ 17 ]. These preparation methods are simple and practical for real-world applications without complicating battery manufacturing. Commonly used coating materials include oxides (e.g., Al 2 O 3 , TiO 2 , ZnO, BaTiO 3 , Li 4 Ti 5 O 12 ) [ 18 – 20 ], phosphates (e.g., Li 3 PO 4 , AlPO 4 , Li 1 + x AlₓTi 2 − x (PO 4 ) 3 ) [ 21 – 23 ], fluorides (e.g., AlF 3 [ 24 ], CeF 3 [ 25 ]), and polymers (e.g., polypyrrole, polyphenylene) [ 26 – 29 ]. However, most metal oxides and fluorides exhibit poor ionic conductivity under low-temperature conditions, leading to reduced ion transport performance. Lithium zirconium phosphate maintains an amorphous state at 800℃, enabling stable and uniform coating formation [ 30 , 31 ]. This study employs surface coating to optimize cathode material morphology, aiming to develop high-energy-density, high-capacity, structurally stable, and cost-effective cathode materials for high-voltage applications. Such innovations will extend the service life of lithium cobalt oxide batteries, enhance capacity, and improve safety, ultimately providing a simple, economical, and effective solution for their adoption in new energy vehicle power batteries. 2. Experimental methods 2.1. Material Synthesis The LCO composition was prepared with a Li:Co ratio of 1.05:1. First, Li 2 CO 3 (99.0%) and Co 3 O 4 (99.9%) were weighed according to the specified ratio. The powders were then mixed with ethanol and subjected to ball milling for 12 hours at a weight-to-ball ratio of 8:1. The resulting slurry was dried in an oven at 60°C for 12 hours, the powder underwent grinding and sieving. Finally, the material was reheated to 900°C in the muffle furnace for another 10 hours to obtain the LCO sample. In this project, we developed a simplified coprecipitation method for preparing Lithium cobalt oxide material coated with lithium zirconium phosphate (LCO@LGPO). First, we mixed bare LCO with an aqueous solution containing LiCl, ZrOCl 2 ·8H 2 O, and triethylamine (TEA). The mixture was then stirred at 120℃ for 12 hour in a pressure vessel lined with Teflon, followed by calcination in an air atmosphere at 700℃ for six hours, yielding the lithium cobalt oxide particle product coated with lithium zirconium phosphate (Li 2 Zr(PO4)₂, LGPO) on its surface as shown in Fig. 1 . To confirm the elemental composition accuracy, ICP-MS measurements were performed on the LCO@LGPO samples (Table S1 , Supporting Information). The test data closely matched our experimental expectations. Atomic occupancy is crucial when investigating the mechanism of element interactions. 2.2. Material Characterization To investigate crystal structures, a Bruker D8 X-ray diffraction (XRD) instrument was employed with a scanning range of 10–80° and a speed of 0.02 o /s. Rietveld refinement was performed using the General Structure Analysis System (GSAS). Microscopic morphology was analyzed through Scanning Electron Microscopy (ZEISS Sigma 360) and Transmission Electron Microscopy (JEOL JEM-F200). The morphology of prepared materials and cross-sectional sections of cathode sheets were observed via Field Emission Scanning Electron Microscopy (SEM; Hitachi REGULUS8230). Cross-sectional sections were obtained by polishing cathode sheets for 40 minutes under 6 kV acceleration voltage using an Ar + milling system (Hitachi IM4000 Plus). Inductively Coupled Plasma Mass Spectrometry (NexION 350D) was used to detect actual chemical compositions. X-ray Photoelectron Spectroscopy (XPS, ESCALAB Xi + ) was employed to analyze surface components. All XPS data were processed using Avantage software. To gain deeper insights into post-cycling phase transition mechanisms and microstructural changes in battery materials, electron backscatter diffraction (EBSD) was utilized to examine surface microstructures and elemental distribution on cathode electrodes. 2.3. Electrochemical Characterization The active materials, polyvinylidene fluoride (PVDF) and acetylene black, were uniformly mixed in a 8:1:1 ratio to form a slurry. The slurry was then evenly coated onto the aluminum foil and collected on aluminum foil. The aluminum foil was cut into thin sheets using a slicing machine. Lithium foil served as the anode electrode. The battery case was made of CR 2025 material, with a separator of polypropylene film (Celgard 2400). The electrolyte was 1 M LiPF 6 composed of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) (EC/DMC/DEC = 1:1:1 volume ratio). The battery underwent approximately 750 Pa pressure treatment. Additionally, the battery was left undisturbed for over 12 hours prior to testing. The active material loading was 2.5–3.5 mg/cm². Electrochemical performance was measured using the Neware testing system. Cyclic capacity tests were conducted with 5 cycles at 0.1 C followed by n cycles at 1.0 C. Rate capability tests included five charge-discharge cycles at different current densities. Constant-current intermittent titration (GITT) was employed. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) scans were performed using the CHI660E electrochemical workstation. 2.4. Computational Details The Vienne ab initio simulation package (VASP) 10 − 13 and the projector-enhanced wave (PAW) scheme were used, and Density Functional Theory (DFT) calculations were performed using DFT's periodic plane wave realization ( the plane wave cut-off energy is 450 eV ). The Perdew- Burke-Ernzerhof (PBE) exchange-correlation function and the vdW-DFT exchange- correlation function are used as the generalized gradient approximation (GGA). 3×3×1k point sampling and integration for Brillouin zone in the Monkhurst-Bag scheme. The convergence criteria for all calculated total energies and interatomic forces are 10 − 6 eV and 0.01 eV Å −1 per unit cell, respectively. 3. Results and discussion 3.1. Structural characterization Through scanning electron microscopy (SEM) analysis, we conducted a detailed examination of the particle morphology characteristics (Figs. 2 a, S1, Supporting Information). The original lithium cobalt oxide (LCO) exhibits an irregular shape with a surface roughness of approximately 5–10 µm (Fig. S1 -2, Supporting Information), which facilitates coating. As depicted in Figs. 2 b-f, its surface is indeed coated by various substances, with visible lithium zirconium phosphate (Li 2 Zr(PO4)₂, LGPO) deposits forming a layered structure that uniformly envelops the lithium cobalt oxide. The Energy dispersive spectroscopy (EDS) scanning reveals a relatively uniform distribution of elements, showing no significant particle aggregation. Compared the degree of lithium-ion and cobalt-ion mixing in pure LCO and LCO@LGPO, it can be observed that the mixing degree decreases from 2.71–1.68%. This is because Zr 4+ lack unpaired electrons, which suppresses lithium-cobalt mixing and effectively enhances ion diffusion rates[ 32 ]. The chemical composition ratio of Zr:Co is determined to be 0.24:61.16 through inductively coupled plasma optical emission spectrometry (ICP-OES). The results confirmed that the content of Li4SiO4 in LiCoO2@Li4SiO4 is 0.95 wt.%. 3.2. Electrochemical properties The cyclic tests were conducted in a constant temperature chamber at 25°C with a voltage range of 3.0-4.6V. Figure 4 a shows the initial capacities of three modified materials containing 1%, 2% and 3% Lithium zirconium phosphate (LGPO). The discharge specific capacities were measured at 162.7, 178.1, and 171.3 mAh·g − 1 respectively, with capacity retention rates reaching 76.0%, 86.3% and 85.6% after 200 cycles. This indicates that the 2% LGPO-coating material demonstrates superior effectiveness in suppressing adverse phase transitions and enhancing long-term cycling stability, confirming the crucial role of lithium zirconium phosphate coating in maintaining structural integrity and capacity retention. Subsequent experiments adopted a 2% LGPO-coated LCO for further testing. To further analyze the cycling stability performance, Fig. 4 b demonstrate the discharge capacities of LCO and LCO@LGPO at 1C after 300 cycles. The bare LCO cathode showed an initial capacity of 149.1 mAh·g − 1 , which dropped to 114 mAh·g − 1 after 200 cycles. In contrast, LCO@LGPO maintained an initial capacity of up to 178.1 mAh·g − 1 with a 74.6% capacity retention rate after 300 cycles. This indicates that during charge-discharge cycles, the structural collapse caused by harmful phase transitions in LCO cathodes leads to capacity degradation, whereas LCO@LGPO demonstrates enhanced reversible capacity and mitigated voltage fade, thereby improving cathode energy density. The cyclic voltammetry (CV) curves (Fig. 4 c) were employed to investigate the effects of different sweep rates (0.1-2 mV/s) on the redox mechanism of the LGPO coating. The CV curves revealed a decrease in lattice oxygen oxidation activity during the initial scan and a weakening of the reduction peak near 3.35 V, indicating it has a passivating effect on the interfacesuppressed lattice oxygen activity. This was attributed to the passivation effect of Zr and P on the interfacial structure, further confirming that the LGPO coating stabilizes the interface structure and provides durable reversible redox reactions. Using the Randles-Sevcik equation, the lithium-ion diffusion coefficients (D Li + ) of the two cathode materials were measured at 3.49×10 − 12 cm 2 ·s − 1 and 8.51×10 − 12 cm 2 ·s − 1 respectively. After normalized analysis of current peak variations under different sweep rates, Fig. 4 f showed that LCO@LGPO exhibited higher D Li + values than pure LCO across all sweep rates. This improvement primarily resulted from the coating's effective encapsulation of lithium zirconium phosphate (LGPO) on its surface [ 33 – 35 ], which significantly enhanced Li-ion transport efficiency at the interface, thereby achieving substantial performance enhancement. The differential capacitance curves across different charge cycles are presented in Fig. 4 d. Comparative analysis reveals that LCO@LGPO exhibits greater overlap than LCO, with its peak position showing significant cycle-dependent shift, indicating structural instability and increased impedance. In contrast, LCO@LGPO maintains nearly complete overlap throughout 300 cycles, demonstrating that the LGPO-coated layer stabilizes interfacial structures, enhances ion diffusion, and improves cathode kinetics. The strong Zr-O and P-O bonds maintain the integrity and orderliness of the layered structure [ 36 ], effectively suppressing irreversible structural degradation while creating favorable conditions for lithium-ion transport. To investigate rapid charge-discharge performance, two cathode materials were tested under different current densities (0.1C, 0.5C, 1C, 2C, 5C, 10C) for rate capability, with results recorded in Fig. 4 e. At 0.1C rate, LCO@LGPO demonstrated a discharge capacity of 183.5 mAh·g − 1 . Under high-rate conditions at 10 C, the material achieved 108.7 mAh·g − 1 , showing significantly better performance than LCO. This improvement likely stems from Zr ions expanding lattice spacing and reducing energy barriers for Li + transport. The enhanced rate capability became more pronounced at higher rates, indicating synergistic effects of coating modification on rate performance. When the charge-discharge rate was restored to 0.1C, LCO@LGPO maintained 99.7% capacity retention, confirming its structural reversibility and stability during cycling. 3.3. Analysis of cathode interface film composition The rate of lithium-ion diffusion is a critical factor affecting battery performance. To better evaluate the kinetic characteristics of LCO and LCO@LGPO materials, comprehensive studies were conducted using electrochemical impedance spectroscopy (EIS), galvanostatic current intercalation titration (GITT), and distributed relaxation time (DRT) methods. Figures 5 (a-d) show EIS spectra, Nyquist plots (Fig. S3), and corresponding RCEI and Rct values [ 39 ] for LCO and LCO@LGPO after 50, 100, 150, 200 and 250 charge cycles. Compared with LCO, LCO@LGPO samples exhibited lower impedance values after 250 cycles, indicating faster reaction kinetics while maintaining high lithium-ion conductivity. However, harmful reactions between electrodes and electrolyte during continuous cycling lead to surface material accumulation, ultimately causing a sharp decline in lithium-ion diffusion performance. The Li + diffusion coefficient (D Li + ) is a standard parameter for material kinetics, calculated via GITT. Figures 5 (e-f) present D Li + values derived from GITT data. As shown in Fig. 5 (b), the lithium-ion diffusion coefficient stabilizes above 3.9 V. Specifically, LCO@LGPO's DLi + is approximately 10 − 11.75 , an order of magnitude higher than LCO's 10 − 13 , demonstrating faster lithium-ion diffusion kinetics in LCO@LGPO. After 200 cycles under 1C conditions, we employed high-resolution transmission electron microscopy (HRTEM) images to characterize the relationship between cathode microstructure and performance post-cycling. Figures 6 (a, b) show that the LGPO@LCO composite exhibits a thinner Cathode Electrolyte Interphase (CEI) and wider lattice spacing than the LCO surface layer. This discrepancy arises from intense side reactions between the cathode and electrolyte, where organic deposits impede Li + transport (Figs. S4, Supporting Information). Electron backscattering diffraction (EBSD) analysis of cross-sectional microstructures of electrode slices reveals that the cathode material maintains LGPO intact crystallographic integrity after 200 cycles, with no observable microcracks at the grain boundaries (Fig. 6 d, f and S5). This contrasts sharply with the severe crack propagation typically reported in bare LCO under identical cycling conditions. While microcrack formation in bare LCO is widely linked to oxygen release-induced phase transformation [ 37 , 38 ] and intergranular fracture[ 39 ], the absence of such defects here confirms the effectiveness of coating lithium zirconium phosphate strategy in decoupling electrochemical cycling from mechanical degradation. Since XPS typically has a detection depth of approximately 10 nm, we utilized XPS to investigate the cathode electrolyte interphase (CEI) of bare LCO and LCO@LGPO after 200 cycling. The CEI formed on both electrodes after 200 cycles exhibited similar chemical compositions, primarily consisting of organic carbonate substances and inorganic components (LiF and LiPOF). Fig. S6 displays the whole spectra of LCO and LCO@LGPO probed by XPS depth profile after 300 cycles. The C1s spectrum mainly consists of conductive carbon black, binder PVDF, and decomposition products from the electrolyte. The C-C bond at 284.8eV corresponds to carbon black, while the 286.5 eV C-O bond and 288.8 eV C = O bond originate from lithium carbonate and alkyl components decomposed in the electrolyte. These organic compounds constitute the main constituents of the CEI layer. The higher peak areas of C-O and C = O peaks in bare LCO's C1s spectrum may be attributed to organic decomposition components, indicating thick CEI layers formed by severe side reactions caused by highly active O and Co species at the cathode surface under high voltage. Compared with LCO and LCO@LGPO, LCO@LGPO shows smaller C-O peaks, suggesting its its advantage in inhibiting the side reactions at the electrolyte interface. Furthermore, the O 1s spectrum confirmed the presence of C-O (530.5 eV) and C = O (532.0 eV) bonds, with a distinct Co-O peak observed in Fig. 7 (e, f), which further validates the protected CEI layer. For the P 2p spectrum (Fig. 7 c, d), the result shows that The peak of phosphate radical migrated from 133.64 eV to 133.70 eV, indicating that surface modification reduced interfacial side reactions. The coating material in LCO@LGPO reduces byproduct formation, makes the electrochemical interfacial layer thinner, and enhances lithium-ion diffusion kinetics. Quantitative XPS analysis (Fig. 7 g) revealed that LCO@LGPO exhibited a higher ratio of lattice oxygen to inorganic components compared to post-cycling bare LCO, ensuring high chemical stability at elevated voltages, which indicates a critical factor for LCO's stable cycling performance at 4.6V. Consequently, the LGPO-coated strategy effectively inhibits Co dissolution and oxygen release during cycling, enhances surface structural stability, and stabilizes the structural integrity of the LCO cathode. 3.4. Theoretical calculation To further demonstrate the enhance interface stability mechanism of the LiCoO 2 /Li 2 Zr(PO4)₂ heterojunction surfaces, a DFT analysis was performed in this study. Figures 8 a-c reveal the work functions of LCO, LGPO, and LCO/LGPO. The work function indicates the minimum energy required for electrons to escape from material surfaces. LCO exhibits a work function of 5.318 eV, while LGPO reaches 7.215 eV. Electrons flow from LCO (with lower work function) to LGPO (higher work function) until Fermi level equilibrium is achieved. The heterojunction LCO/LGPO demonstrates a work function of 5.154 eV, where the yellow portion represents electron accumulation and the blue portion indicates electron depletion [ 33 , 34 ]. Notably, the band gap between the valence band top and conduction band bottom of Co 3d and O 2p orbitals in LCO@LGPO is significantly narrower than that in LCO. This reduced band gap enhances electronic conductivity and accelerates charge transfer rates [ 40 ]. Such orbital changes help suppress oxygen's charge compensation effect and strengthen the stability of the oxygen framework. In Figs. 8 d-f, the (104) surface crystal structure of LCO (Fig. S7, Supporting Information) consists of truncated LiO 6 (blue) and CoO 6 (green) octahedra, exposing a large amount of unbound interfacial lattice oxygen. Notably, within the LiCoO 2 bulk region, lattice oxygen coordinates with four lithium atoms and two cobalt atoms, forming the characteristic Li-O-Li configuration.This explains the instability of the lattice oxygen structures in LCO, particularly the irreversible alteration of interfacial lattice oxygen into oxygen. At the interface between the LiCoO 2 (104) surface and the LGPO (202) composite coating (Fig. 8 f), Zr and P atoms prefer to bond with the oxygen atoms in the interfacial lattice through lattice distortion. This occurs because Zr-O and P-O bonds are more stable, which stabilizes the octahedral structure at the interface. The oxygen atoms at the interface have a coordination number of 5, binding exclusively to Zr or P. Consequently, we calculated the density of states (DOS) of LCO@LGPO under Co-O, Zr-O, and P-O bonding conditions (Fig. 6 g). The 2p orbital of oxygen near the Fermi level is nearly zero or shifts downwards compared to similar studies (indicating reduced charge compensation capability), with significantly fewer high-energy 2p states. This suggests weaker hybridization between Co 3d and O 2p, resulting in more high-energy O 2p states near the Fermi level – a mechanism that greatly enhances the stability of interfacial lattice oxygen.These findings demonstrate that zirconium-oxygen and phosphorus-oxygen bonds are more stable, and passivating interfacial lattice oxygen can improve the interfacial stability of LCO. This also indicates that charge compensation is primarily provided by Co [ 33 – 36 ] (with a particularly high peak near the Fermi level, suggesting Co's enhanced capacity for charge compensation, which may be related to its rate performance). The orbital hybridization between the Co 3d orbital and O 2p orbital stabilizes the interface lattice oxygen [ 31 , 37 ]. Lithium zirconium phosphate as the coating layer, situated above the Fermi level, is less likely to donate electrons during charge/discharge cycles, indicating its stable existence without corrosion during cycling. The interface exhibits electron regulation (controlled by O and Co) while maintaining physical isolation from the amorphous lithium zirconium phosphate phase, preventing decomposition. Furthermore, we calculated the differential charge of LCO@LGPO in the de-lithiated state, as shown in Fig. 8 h-i. Under deep de-lithiation conditions, LGPO creates an internal electric field that prevents electron leakage from LCO while providing ion channels. This configuration significantly enhances ion migration rates, thereby improving the battery's rate performance. Additionally, LGPO itself acts as a protective coating to isolate LCO from direct contact with the electrolyte, substantially reducing side decomposition reactions. These theoretical findings align with experimental observations and provide compelling evidence for enhanced structural stability during cycling processes. 4. Conclusions In this study, we achieve stable 4.6 V operation of LiCoO₂ cathodes through Li₂Zr(PO₄)₂ (LGPO) coating. The optimized 2 wt.% LGPO-coated LCO demonstrates enhanced electrochemical performance, delivering an initial capacity of 178.1 mAh·g⁻¹ at 1C with 86.3% capacity retention after 200 cycles (compared to 76.0% for pristine LCO). The modified cathode exhibits superior rate capability (108.7 mAh·g⁻¹ at 10C) and exceptional structural reversibility (99.7% capacity recovery at 0.1C). Through comprehensive characterization, we confirm the LGPO coating effectively reduces Li⁺/Co²⁺ cation mixing from 2.71–1.68%, facilitates Li⁺ diffusion through expanded interlayer spacing, and effectively mitigates kinetic constraints under high-voltage operation. The LGPO coating critically suppresses interfacial degradation mechanisms through dual protection: 1) Formation of an inorganic-rich CEI layer (LiF, LiPOF) with 30% reduction in organic components (XPS quantification); 2) Enhanced oxygen lattice stabilization via robust Zr–O/P–O bonding. First-principles calculations reveal the LCO/LGPO heterointerface exhibits reduced work function (5.154 eV) and stabilized oxygen framework through d-p orbital hybridization, while generating an internal electric field that simultaneously blocks electron leakage and promotes Li⁺ conduction. This integrated modification strategy successfully decouples electrochemical cycling from mechanical degradation, providing a scalable solution for developing high-voltage LCO cathodes in next-generation lithium-ion batteries. Declarations Author Contribution Wu KY and Yu LS, Tang K, Wang SJ wrote the main manuscript text and Tang HW prepared figures 1-3, Wang D prepared figures 4,5, Liu Y prepared figure6, Jiang JJ prepared figures 7,8. All authors reviewed the manuscript. Acknowledgements The authors express gratitude for the technical services provided by the Meishan vocation & Technical College. This work was financially supported by the Startup Foundation for Introducing Talent of Meishan Vocation & Technical College (No. 2024RC06), the Key Laboratories of Fine Chemicals and Surfactants in Sichuan Provincial Universities (No. 2024JXY07), and the Meishan Science and Technology Bureau project (No. 2024KJZD085). The authors extend their gratitude to Ms. Xiuyu Yin from Scientific Compass (www.shiyanjia.com) for providing invaluable assistance with the XPS analysis and HRTEM tests. References Y Zhou (2022) Transition towards carbon-neutral districts based on storage techniques and spatiotemporal energy sharing with electrification and hydrogenation. Renew Sust Energ Rev 162:112444. https://doi.org/10.1016/j.rser.2022.112444 Lin C, Li J, Yin, Z, Huang, W, Zhao, Q, Weng, Q, Liu, Q, Sun, J, Chen, G, Pan, F (2024) Structural Understanding for High-Voltage Stabilization of Lithium Cobalt Oxide. 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J Energy Chem 105:814-822. https://doi.org/10.1016/j.jechem.2025.01.025 Ding Q, Jiang Z, Chen K, Li H, Shi J, Ai X, Xia D (2024) Superior stable high‐voltage LiCoO 2 enabled by modification with a layer of lithiated polyvinylidene fluoride‐derived LiF. Carbon Energy 6:e602. https://doi.org/10.1002/cey2.602 Khalid R, Shah A, Javed M, Hussain H (2025) Progress and obstacles in electrode materials for lithium-ion batteries: a journey towards enhanced energy storage efficiency. RSC adv 15:15951-15998. https://doi.org/10.1039/D5RA02042E Li J, Wang J, Huang H, Gao M, Wang X, Dong Q, Hu W (2024) Stabilization of LiCoO 2 Cathodes in High Voltage Lithium Metal Batteries Through 2‐(Trifluoromethyl) Benzamide (2‐TFMBA) Electrolyte Additives. Small 20:2400087. https://doi.org/10.1002/smll.202400087 Gou X, Wang J, Zhu F, Meng Y (2024) High-voltage stability and electrochemical performance of polyacrylic acid–xanthan gum copolymer-reinforced LiCoO 2 cathode material. New J Chem 48:19441-19451. https://doi.org/10.1039/D4NJ02889A Li X, Zhu X, Zhang Y, Han L, Gao J, Liu D, Zhou W (2025) Ternary Inert Element Co‐Doping: a New Approach to Stable 4.7 V LiCoO 2 . Adv Mater 2506228. https://doi.org/10.1002/adma.202506228 Li S, Wu F, Chen T, Kang K, Guo R, Liu C, Wu C (2025) Progress and Challenges for Energy-Dense and Cost-Effective Anode-Free Lithium Metal Batteries. Energy Mater Adv 6:0168. https://doi.org/10.34133/energymatadv.0168 Lee J, Han YK (2025) Unveiling the mechanism of dense cathode‒electrolyte interphase formation in lithium-ion batteries using cyclophosphamide additive. Electrochimica Acta 513:145628. https://doi.org/10.1016/j.electacta.2024.145628 Meng T, Hu X (2025) Thermal-durable electrolytes towards ultrawide-temperature lithium-ion batteries with high-voltage layered oxide cathodes: failure mechanisms and stability countermeasures. Energy Storage Mater 104126. https://doi.org/10.1016/j.ensm.2025.104126 You H, Jiang J, Chen L, Li C (2024) Weakened Solvation Structure Electrolytes Enable High-Voltage Graphite|| LiCoO 2 Batteries. ACS Appl. Energy Mater 7:6696-6703. https://doi.org/10.1021/acsaem.4c01296 Wei X, Zhang Q, Shen M, Shi X, Wu D, Zhen C, Gu MD (2025) Cathode-Electrolyte Interphase Engineering through Artificial Surface Coating in 4.55 V High-Voltage LiCoO 2 Cathodes. ACS Appl. Mater. Interfaces, https://doi.org/10.1021/acsami.4c20331 Zhao Y, Zeng W, Qin S, Su S, Wu J, Ke J, Sun Y, Liu K, Lin X (2024) A “three-in-one” strategy via La2O3-ZrO2 coating to effectively enhance the electrochemical performance of LiCoO2. Journal of Alloys and Compounds 989:174377. https://doi.org/10.1016/j.jallcom.2024.174377 Wei X, Zhang Q, Shen M, et al (2025) Cathode-Electrolyte Interphase Engineering through Artificial Surface Coating in 4.55 V High-Voltage LiCoO2 Cathodes. ACS Applied Materials & Interfaces. https://doi.org/10.1021/acsami.4c20331 Hu C, Dai L, Huang F, Yang Y, Liang S, Fang G, Zhang Q (2025) Carboxylate‐Based Electrolyte with Bilateral Functions Enable Working Sodium‐Metal Batteries at −60°C. Angewandte Chemie International Edition. https://doi.org/10.1002/anie.202508584 Li M, Amzil S, Peng C, Wu XT, Feng J, Liu X, Gao J, Müller-Buschbaum P, Cheng YJ, Xia Y (2025) Interfacial regulation of a 4.5 v LICOO2-Based battery via advanced slurry additive modification. ACS Applied Materials & Interfaces. https://doi.org/10.1021/acsami.5c03789 Li T, Zou J, Xiao Y, Li Y, Wang W, Zhang T (2024) Constructing stable electrode–electrolyte interfaces by sulfone-based additive to improve the high-voltage performance of LiCoO2. Journal of Alloys and Compounds 999:175060 https://doi.org/10.1016/j.jallcom.2024.175060 Li Y, Mao G, Yang H, Yao T, Shen L (2025) Advanced dynamic sintering and surface engineering synergistically enhance the structural and electrochemical stability of single-crystal cathodes. Journal of Power Sources 650:237460 https://doi.org/10.1016/j.jpowsour.2025.237460 Li X, Wang K, Tian M, et al (2025) Epitaxially grown Lattice‐Coherent surface enabling superior mechanical integrity for High‐Voltage LICOO2 Cathode. Angewandte Chemie International Edition. https://doi.org/10.1002/anie.202504221 Yang X, Lin M, Zheng G, et al (2020) Enabling stable High‐Voltage LICOO2 operation by using synergetic interfacial modification strategy. Advanced Functional Materials. https://doi.org/10.1002/adfm.202004664 Additional Declarations No competing interests reported. Supplementary Files SupportingInformation.docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 29 Sep, 2025 Reviews received at journal 21 Sep, 2025 Reviews received at journal 18 Sep, 2025 Reviewers agreed at journal 14 Sep, 2025 Reviewers agreed at journal 13 Sep, 2025 Reviewers agreed at journal 13 Sep, 2025 Reviewers invited by journal 11 Sep, 2025 Editor assigned by journal 24 Aug, 2025 Submission checks completed at journal 24 Aug, 2025 First submitted to journal 22 Aug, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7435444","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":515658775,"identity":"0f6f7046-d811-4fc6-a221-26d90231916b","order_by":0,"name":"Keying Wu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA30lEQVRIiWNgGAWjYBACNvbGxgcJPDZy9s3MBx8kVNQQ1sLHc/iwwQeZNGMDdrZkgwdnjhHWIieRliY5w+Zw4gZ+HjPJhy3MRDiM54yxMU/OYWNzZh6zisQGNgb+9u4EAn7pMXzMcyZdzrKZrexG4g4ZBokzZzcQtoW3x9qY4TDzthuJZ9gYDCRyCWiRyDGT5v3HnNhwmMGsILGNmRgtIO/zOCduOMxixkCcFnAg86QZSzazJUsknDnGQ9Av8u3QqOTnP3zw44+KGjn+9l78WjAAD2nKR8EoGAWjYBRgBQCZt0gdfA7vnQAAAABJRU5ErkJggg==","orcid":"","institution":"Meishan Vocational \u0026 Technical College","correspondingAuthor":true,"prefix":"","firstName":"Keying","middleName":"","lastName":"Wu","suffix":""},{"id":515658776,"identity":"1678d1bb-3c33-49a0-b91d-5b3f792e3bd8","order_by":1,"name":"Haiwen Tang","email":"","orcid":"","institution":"Meishan Vocational \u0026 Technical College","correspondingAuthor":false,"prefix":"","firstName":"Haiwen","middleName":"","lastName":"Tang","suffix":""},{"id":515658777,"identity":"d7aaf3f2-4d20-4f43-92ed-c2216f61c531","order_by":2,"name":"Yao Liu","email":"","orcid":"","institution":"Meishan Vocational \u0026 Technical College","correspondingAuthor":false,"prefix":"","firstName":"Yao","middleName":"","lastName":"Liu","suffix":""},{"id":515658781,"identity":"4eae2b41-f2d1-4cd2-9aa6-e6036a33ae1f","order_by":3,"name":"Dan Wang","email":"","orcid":"","institution":"Meishan Vocational \u0026 Technical College","correspondingAuthor":false,"prefix":"","firstName":"Dan","middleName":"","lastName":"Wang","suffix":""},{"id":515658783,"identity":"c1343689-3728-4e9a-bcc6-2b99f21c3485","order_by":4,"name":"Sujun Wang","email":"","orcid":"","institution":"Meishan Vocational \u0026 Technical College","correspondingAuthor":false,"prefix":"","firstName":"Sujun","middleName":"","lastName":"Wang","suffix":""},{"id":515658784,"identity":"116eb370-243f-4122-b95b-e46c9b492529","order_by":5,"name":"Jinjin Jiang","email":"","orcid":"","institution":"Meishan Vocational \u0026 Technical College","correspondingAuthor":false,"prefix":"","firstName":"Jinjin","middleName":"","lastName":"Jiang","suffix":""},{"id":515658785,"identity":"ebd00f03-31ad-4076-9de8-b60f16bc6d59","order_by":6,"name":"Liusi Yu","email":"","orcid":"","institution":"Meishan Vocational \u0026 Technical College","correspondingAuthor":false,"prefix":"","firstName":"Liusi","middleName":"","lastName":"Yu","suffix":""},{"id":515658786,"identity":"41cdce27-7629-4422-9f90-3b705ec4f1fd","order_by":7,"name":"Kai Tang","email":"","orcid":"","institution":"Key Laboratories of Fine Chemicals and Surfactants in Sichuan Provincial Universities","correspondingAuthor":false,"prefix":"","firstName":"Kai","middleName":"","lastName":"Tang","suffix":""}],"badges":[],"createdAt":"2025-08-22 14:38:18","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7435444/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7435444/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":91641877,"identity":"aede2225-8489-4ae8-a7e0-61047b7cca2d","added_by":"auto","created_at":"2025-09-18 15:05:35","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":637954,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of a single-step wet chemical reaction pathway and near-surface atomic configuration\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7435444/v1/98413a816d4c051e26dba491.png"},{"id":91641684,"identity":"76097f55-bf12-4212-be48-95c0beaa80f1","added_by":"auto","created_at":"2025-09-18 14:57:35","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":545208,"visible":true,"origin":"","legend":"\u003cp\u003e(a) SEM of LCO@LGPO. (b-f) EDS line scanning and the corresponding EDX mappings of LCO@LGPO\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7435444/v1/1f9cb819bd2c45e1f73b522c.png"},{"id":91641683,"identity":"27fbbc2a-b9e1-499f-b4bc-cb751db3ad9d","added_by":"auto","created_at":"2025-09-18 14:57:35","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":91442,"visible":true,"origin":"","legend":"\u003cp\u003eThe XRD and Rietveld refinement of (a) LCO and (b) LCO@LGPO\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7435444/v1/9c0fc9fb74fcfdf4aa38a543.png"},{"id":91641689,"identity":"3c4af9f2-ce38-49e8-9630-e484142f6815","added_by":"auto","created_at":"2025-09-18 14:57:35","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":398821,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Cyclic performance of LCO and LCO@LGPO with different LGPO coating amounts at 1C under 3-4.6V voltage range. (b-e) Discharge curves, dQ/dV curves, CV curves, and rate curves of LCO and LCO@LGPO. (f) Lithium-ion diffusion coefficient (D\u003csub\u003eLi+\u003c/sub\u003e) versus current peak variation curves of LCO and LCO@LGPO at different sweep rates\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7435444/v1/1294d84debf6dfcb8cd8908f.png"},{"id":91641688,"identity":"00bfca95-92d5-465c-a6a2-92364f022309","added_by":"auto","created_at":"2025-09-18 14:57:35","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":355658,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Niquist diagram and (b) DRT spectrum of LCO@LGPO and LCO after 50,100,150,200, and 250 cycles; (c) R\u003csub\u003ect\u003c/sub\u003e and (d) R\u003csub\u003eSEI\u003c/sub\u003e values of LCO@LGPO and LCO; GITT curves of (e) LCO@LGPO and (f) LCO and their corresponding lithium ion diffusion coefficients\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7435444/v1/845103e6305deef8ddbe19de.png"},{"id":91641879,"identity":"b63eac6d-4ad9-4bf4-a786-f6d080c19573","added_by":"auto","created_at":"2025-09-18 15:05:35","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":985920,"visible":true,"origin":"","legend":"\u003cp\u003e(a) High-resolution transmission electron microscopy (HRTEM) images of LCO@LGPO and (b) LCO with their corresponding FFT inverse transform images; Electron backscattering diffraction (EBSD) analysis of cross-sectional microstructures of electrode slices of LCO@LGPO (d, f) and LCO (c, e) after 200 cycles\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7435444/v1/e7ec9293296c513bb48d7e41.png"},{"id":91641695,"identity":"d264cb88-748e-4b1c-aa1a-3420e5e14ab4","added_by":"auto","created_at":"2025-09-18 14:57:35","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":373996,"visible":true,"origin":"","legend":"\u003cp\u003e(a) High-resolution transmission electron microscopy (HRTEM) images of LCO@LGPO and (b) LCO with their corresponding FFT inverse transform images; (a, b) Cobalt 1s, (c, d) Oxygen 1s and (e, f) P 2p XPS spectra of LCO and LCO@LGPO after 200 charge cycles; (g) Composition distribution of CEI films obtained through XPS analysis of LCO@LGPO and LCO after 200 charge cycles under 1C conditions\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-7435444/v1/cf3ee6082555a99fd8c5d720.png"},{"id":91642891,"identity":"822a384b-502e-44e5-aaef-e8bb91dc45e2","added_by":"auto","created_at":"2025-09-18 15:13:35","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":382736,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Work function and (d) crystal structure of LGPO; (b) work function and (e) crystal structure of LCO; (c) work function and (f) crystal structure of LCO@LGPO; (g) State density (DOS) of LCO@LGPO; (h) Crystal structure of LCO@LGPO; (i) Charge difference diagram of LCO@LGPO in the de-lithium state\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-7435444/v1/f835950992297e1c07a191ac.png"},{"id":91644235,"identity":"70f42e7b-2d12-42bd-92d1-9c4083542956","added_by":"auto","created_at":"2025-09-18 15:29:37","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4220649,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7435444/v1/5efcb6a1-c18b-4266-8a59-274da3d958d2.pdf"},{"id":91641707,"identity":"06bc0662-27cb-4dd4-948b-b7cc23d91a38","added_by":"auto","created_at":"2025-09-18 14:57:36","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":5726800,"visible":true,"origin":"","legend":"","description":"","filename":"SupportingInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-7435444/v1/78c9cb735020a2b16e92319b.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003e\u003cstrong\u003eStabilizing Interfacial Structure of LiCoO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e with Ultrahigh Capacity and Prolonged Cyclability at 4.6V\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eCurrently, LiCoO\u003csub\u003e2\u003c/sub\u003e (LCO) cathode materials are widely used for Li\u003csup\u003e+\u003c/sup\u003e ion storage due to their typical layered structure [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e], high energy density [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], and long cycle life [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. To achieve higher energy density, researchers have attempted to raise the charging cut off voltage beyond 4.6 V (vs Li/Li\u003csup\u003e+\u003c/sup\u003e) to unlock additional capacity [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. However, operating at voltages above 4.6 V during cycling causes severe surface Co/O loss and structural degradation [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], which hinders practical applications.\u003c/p\u003e\u003cp\u003eSurface degradation originates from detrimental inter-facial reactions. For instance, during electrolyte charging, solvents like ethylene carbonate (EC) undergo dehydrogenation/oxidation at the LCO/electrolyte interface [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], generating H\u003csup\u003e+\u003c/sup\u003e/H\u003csub\u003e2\u003c/sub\u003eO ions that catalyze the hydrolysis of PF\u003csub\u003e6\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e anions into corrosive substances such as HF, HPO\u003csub\u003e2\u003c/sub\u003e, and F\u003csub\u003e2\u003c/sub\u003e, leading to Co dissolution and O loss [\u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Additionally, solvent decomposition forms a porous, poorly protective cathode/electrolyte interface (CEI) rich in organic matter. Simultaneously, surface lattice oxygen at voltages above 4.6V in LCO significantly oxidizes and releases as O\u003csub\u003e2\u003c/sub\u003e, exacerbating interfacial side reactions [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. The combined effects of O\u003csub\u003e2\u003c/sub\u003e release and Co dissolution cause surface degradation, thereby hindering Li\u003csup\u003e+\u003c/sup\u003e transport.\u003c/p\u003e\u003cp\u003eTo address the issue, it is essential to regulate the interfacial reactions between LCO and electrolyte. Strategies include electrolyte tuning and/or surface modification of LCO. In terms of electrolytes, applying fluorinated solvents, high-concentration electrolytes, or additives can optimize CEC performance, resulting in CECs enriched with inorganic species [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. For surface modification, reducing direct contact between Co\u003csup\u003e4+\u003c/sup\u003e/O\u003csup\u003en\u0026minus;\u003c/sup\u003e (0\u0026thinsp;\u0026lt;\u0026thinsp;n\u0026thinsp;\u0026lt;\u0026thinsp;2) on the surface and electrolyte, as well as replacing lattice-Co/O to lower surface oxidation activity, are primary approaches [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. More attention has been focused on interface reactions caused by surface structures, such as using spinel layers or metal oxide coatings [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. However, increased surface impedance and uneven distribution of metal oxides limit cathode performance. Therefore, regulating interface reactions is crucial for achieving excellent cycling stability of LCO under harsh conditions.\u003c/p\u003e\u003cp\u003eTo address the aforementioned issues and improve the interfacial reaction between LCO and electrolyte, optimizing morphology to enhance the actual lithium-ion diffusion rate in two-dimensional cathode structures has proven most effective through surface coating and bulk doping [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. These preparation methods are simple and practical for real-world applications without complicating battery manufacturing. Commonly used coating materials include oxides (e.g., Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, TiO\u003csub\u003e2\u003c/sub\u003e, ZnO, BaTiO\u003csub\u003e3\u003c/sub\u003e, Li\u003csub\u003e4\u003c/sub\u003eTi\u003csub\u003e5\u003c/sub\u003eO\u003csub\u003e12\u003c/sub\u003e) [\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], phosphates (e.g., Li\u003csub\u003e3\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e, AlPO\u003csub\u003e4\u003c/sub\u003e, Li\u003csub\u003e1\u0026thinsp;+\u0026thinsp;x\u003c/sub\u003eAlₓTi\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e) [\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], fluorides (e.g., AlF\u003csub\u003e3\u003c/sub\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], CeF\u003csub\u003e3\u003c/sub\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]), and polymers (e.g., polypyrrole, polyphenylene) [\u003cspan additionalcitationids=\"CR27 CR28\" citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. However, most metal oxides and fluorides exhibit poor ionic conductivity under low-temperature conditions, leading to reduced ion transport performance. Lithium zirconium phosphate maintains an amorphous state at 800℃, enabling stable and uniform coating formation [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. This study employs surface coating to optimize cathode material morphology, aiming to develop high-energy-density, high-capacity, structurally stable, and cost-effective cathode materials for high-voltage applications. Such innovations will extend the service life of lithium cobalt oxide batteries, enhance capacity, and improve safety, ultimately providing a simple, economical, and effective solution for their adoption in new energy vehicle power batteries.\u003c/p\u003e"},{"header":"2. Experimental methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Material Synthesis\u003c/h2\u003e\u003cp\u003eThe LCO composition was prepared with a Li:Co ratio of 1.05:1. First, Li\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e (99.0%) and Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e (99.9%) were weighed according to the specified ratio. The powders were then mixed with ethanol and subjected to ball milling for 12 hours at a weight-to-ball ratio of 8:1. The resulting slurry was dried in an oven at 60\u0026deg;C for 12 hours, the powder underwent grinding and sieving. Finally, the material was reheated to 900\u0026deg;C in the muffle furnace for another 10 hours to obtain the LCO sample.\u003c/p\u003e\u003cp\u003eIn this project, we developed a simplified coprecipitation method for preparing Lithium cobalt oxide material coated with lithium zirconium phosphate (LCO@LGPO). First, we mixed bare LCO with an aqueous solution containing LiCl, ZrOCl\u003csub\u003e2\u003c/sub\u003e\u0026middot;8H\u003csub\u003e2\u003c/sub\u003eO, and triethylamine (TEA). The mixture was then stirred at 120℃ for 12 hour in a pressure vessel lined with Teflon, followed by calcination in an air atmosphere at 700℃ for six hours, yielding the lithium cobalt oxide particle product coated with lithium zirconium phosphate (Li\u003csub\u003e2\u003c/sub\u003eZr(PO4)₂, LGPO) on its surface as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. To confirm the elemental composition accuracy, ICP-MS measurements were performed on the LCO@LGPO samples (Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e, Supporting Information). The test data closely matched our experimental expectations. Atomic occupancy is crucial when investigating the mechanism of element interactions.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Material Characterization\u003c/h2\u003e\u003cp\u003eTo investigate crystal structures, a Bruker D8 X-ray diffraction (XRD) instrument was employed with a scanning range of 10\u0026ndash;80\u0026deg; and a speed of 0.02\u003csup\u003eo\u003c/sup\u003e/s. Rietveld refinement was performed using the General Structure Analysis System (GSAS). Microscopic morphology was analyzed through Scanning Electron Microscopy (ZEISS Sigma 360) and Transmission Electron Microscopy (JEOL JEM-F200). The morphology of prepared materials and cross-sectional sections of cathode sheets were observed via Field Emission Scanning Electron Microscopy (SEM; Hitachi REGULUS8230). Cross-sectional sections were obtained by polishing cathode sheets for 40 minutes under 6 kV acceleration voltage using an Ar\u003csup\u003e+\u003c/sup\u003e milling system (Hitachi IM4000 Plus). Inductively Coupled Plasma Mass Spectrometry (NexION 350D) was used to detect actual chemical compositions. X-ray Photoelectron Spectroscopy (XPS, ESCALAB Xi\u003csup\u003e+\u003c/sup\u003e) was employed to analyze surface components. All XPS data were processed using Avantage software. To gain deeper insights into post-cycling phase transition mechanisms and microstructural changes in battery materials, electron backscatter diffraction (EBSD) was utilized to examine surface microstructures and elemental distribution on cathode electrodes.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Electrochemical Characterization\u003c/h2\u003e\u003cp\u003eThe active materials, polyvinylidene fluoride (PVDF) and acetylene black, were uniformly mixed in a 8:1:1 ratio to form a slurry. The slurry was then evenly coated onto the aluminum foil and collected on aluminum foil. The aluminum foil was cut into thin sheets using a slicing machine. Lithium foil served as the anode electrode. The battery case was made of CR 2025 material, with a separator of polypropylene film (Celgard 2400). The electrolyte was 1 M LiPF\u003csub\u003e6\u003c/sub\u003e composed of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) (EC/DMC/DEC\u0026thinsp;=\u0026thinsp;1:1:1 volume ratio). The battery underwent approximately 750 Pa pressure treatment. Additionally, the battery was left undisturbed for over 12 hours prior to testing. The active material loading was 2.5\u0026ndash;3.5 mg/cm\u0026sup2;. Electrochemical performance was measured using the Neware testing system. Cyclic capacity tests were conducted with 5 cycles at 0.1 C followed by n cycles at 1.0 C. Rate capability tests included five charge-discharge cycles at different current densities. Constant-current intermittent titration (GITT) was employed. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) scans were performed using the CHI660E electrochemical workstation.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Computational Details\u003c/h2\u003e\u003cp\u003eThe Vienne ab initio simulation package (VASP) 10\u003csup\u003e\u0026minus;\u0026thinsp;13\u003c/sup\u003e and the projector-enhanced wave (PAW) scheme were used, and Density Functional Theory (DFT) calculations were performed using DFT's periodic plane wave realization ( the plane wave cut-off energy is 450 eV ). The Perdew- Burke-Ernzerhof (PBE) exchange-correlation function and the vdW-DFT exchange- correlation function are used as the generalized gradient approximation (GGA). 3\u0026times;3\u0026times;1k point sampling and integration for Brillouin zone in the Monkhurst-Bag scheme. The convergence criteria for all calculated total energies and interatomic forces are 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e eV and 0.01 eV \u0026Aring;\u003csup\u003e\u0026minus;1\u003c/sup\u003e per unit cell, respectively.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Structural characterization\u003c/h2\u003e\u003cp\u003eThrough scanning electron microscopy (SEM) analysis, we conducted a detailed examination of the particle morphology characteristics (Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea, S1, Supporting Information). The original lithium cobalt oxide (LCO) exhibits an irregular shape with a surface roughness of approximately 5\u0026ndash;10 \u0026micro;m (Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e-2, Supporting Information), which facilitates coating. As depicted in Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb-f, its surface is indeed coated by various substances, with visible lithium zirconium phosphate (Li\u003csub\u003e2\u003c/sub\u003eZr(PO4)₂, LGPO) deposits forming a layered structure that uniformly envelops the lithium cobalt oxide. The Energy dispersive spectroscopy (EDS) scanning reveals a relatively uniform distribution of elements, showing no significant particle aggregation.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eCompared the degree of lithium-ion and cobalt-ion mixing in pure LCO and LCO@LGPO, it can be observed that the mixing degree decreases from 2.71\u0026ndash;1.68%. This is because Zr\u003csup\u003e4+\u003c/sup\u003e lack unpaired electrons, which suppresses lithium-cobalt mixing and effectively enhances ion diffusion rates[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. The chemical composition ratio of Zr:Co is determined to be 0.24:61.16 through inductively coupled plasma optical emission spectrometry (ICP-OES). The results confirmed that the content of Li4SiO4 in LiCoO2@Li4SiO4 is 0.95 wt.%.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Electrochemical properties\u003c/h2\u003e\u003cp\u003eThe cyclic tests were conducted in a constant temperature chamber at 25\u0026deg;C with a voltage range of 3.0-4.6V. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea shows the initial capacities of three modified materials containing 1%, 2% and 3% Lithium zirconium phosphate (LGPO). The discharge specific capacities were measured at 162.7, 178.1, and 171.3 mAh\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e respectively, with capacity retention rates reaching 76.0%, 86.3% and 85.6% after 200 cycles. This indicates that the 2% LGPO-coating material demonstrates superior effectiveness in suppressing adverse phase transitions and enhancing long-term cycling stability, confirming the crucial role of lithium zirconium phosphate coating in maintaining structural integrity and capacity retention. Subsequent experiments adopted a 2% LGPO-coated LCO for further testing.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTo further analyze the cycling stability performance, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb demonstrate the discharge capacities of LCO and LCO@LGPO at 1C after 300 cycles. The bare LCO cathode showed an initial capacity of 149.1 mAh\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which dropped to 114 mAh\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e after 200 cycles. In contrast, LCO@LGPO maintained an initial capacity of up to 178.1 mAh\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e with a 74.6% capacity retention rate after 300 cycles. This indicates that during charge-discharge cycles, the structural collapse caused by harmful phase transitions in LCO cathodes leads to capacity degradation, whereas LCO@LGPO demonstrates enhanced reversible capacity and mitigated voltage fade, thereby improving cathode energy density.\u003c/p\u003e\u003cp\u003eThe cyclic voltammetry (CV) curves (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec) were employed to investigate the effects of different sweep rates (0.1-2 mV/s) on the redox mechanism of the LGPO coating. The CV curves revealed a decrease in lattice oxygen oxidation activity during the initial scan and a weakening of the reduction peak near 3.35 V, indicating it has a passivating effect on the interfacesuppressed lattice oxygen activity. This was attributed to the passivation effect of Zr and P on the interfacial structure, further confirming that the LGPO coating stabilizes the interface structure and provides durable reversible redox reactions. Using the Randles-Sevcik equation, the lithium-ion diffusion coefficients (D\u003csub\u003eLi\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e) of the two cathode materials were measured at 3.49\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;12\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e\u0026middot;s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 8.51\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;12\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e\u0026middot;s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e respectively. After normalized analysis of current peak variations under different sweep rates, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef showed that LCO@LGPO exhibited higher D\u003csub\u003eLi\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e values than pure LCO across all sweep rates. This improvement primarily resulted from the coating's effective encapsulation of lithium zirconium phosphate (LGPO) on its surface [\u003cspan additionalcitationids=\"CR34\" citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e], which significantly enhanced Li-ion transport efficiency at the interface, thereby achieving substantial performance enhancement.\u003c/p\u003e\u003cp\u003eThe differential capacitance curves across different charge cycles are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed. Comparative analysis reveals that LCO@LGPO exhibits greater overlap than LCO, with its peak position showing significant cycle-dependent shift, indicating structural instability and increased impedance. In contrast, LCO@LGPO maintains nearly complete overlap throughout 300 cycles, demonstrating that the LGPO-coated layer stabilizes interfacial structures, enhances ion diffusion, and improves cathode kinetics. The strong Zr-O and P-O bonds maintain the integrity and orderliness of the layered structure [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e], effectively suppressing irreversible structural degradation while creating favorable conditions for lithium-ion transport.\u003c/p\u003e\u003cp\u003eTo investigate rapid charge-discharge performance, two cathode materials were tested under different current densities (0.1C, 0.5C, 1C, 2C, 5C, 10C) for rate capability, with results recorded in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee. At 0.1C rate, LCO@LGPO demonstrated a discharge capacity of 183.5 mAh\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Under high-rate conditions at 10 C, the material achieved 108.7 mAh\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, showing significantly better performance than LCO. This improvement likely stems from Zr ions expanding lattice spacing and reducing energy barriers for Li\u003csup\u003e+\u003c/sup\u003e transport. The enhanced rate capability became more pronounced at higher rates, indicating synergistic effects of coating modification on rate performance. When the charge-discharge rate was restored to 0.1C, LCO@LGPO maintained 99.7% capacity retention, confirming its structural reversibility and stability during cycling.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e3.3. Analysis of cathode interface film composition\u003c/h2\u003e\u003cp\u003eThe rate of lithium-ion diffusion is a critical factor affecting battery performance. To better evaluate the kinetic characteristics of LCO and LCO@LGPO materials, comprehensive studies were conducted using electrochemical impedance spectroscopy (EIS), galvanostatic current intercalation titration (GITT), and distributed relaxation time (DRT) methods. Figures\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(a-d) show EIS spectra, Nyquist plots (Fig. S3), and corresponding RCEI and Rct values [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e] for LCO and LCO@LGPO after 50, 100, 150, 200 and 250 charge cycles. Compared with LCO, LCO@LGPO samples exhibited lower impedance values after 250 cycles, indicating faster reaction kinetics while maintaining high lithium-ion conductivity. However, harmful reactions between electrodes and electrolyte during continuous cycling lead to surface material accumulation, ultimately causing a sharp decline in lithium-ion diffusion performance. The Li\u003csup\u003e+\u003c/sup\u003e diffusion coefficient (D\u003csub\u003eLi\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e) is a standard parameter for material kinetics, calculated via GITT. Figures\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(e-f) present D\u003csub\u003eLi\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e values derived from GITT data. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(b), the lithium-ion diffusion coefficient stabilizes above 3.9 V. Specifically, LCO@LGPO's DLi\u0026thinsp;+\u0026thinsp;is approximately 10\u003csup\u003e\u0026minus;\u0026thinsp;11.75\u003c/sup\u003e, an order of magnitude higher than LCO's 10\u003csup\u003e\u0026minus;\u0026thinsp;13\u003c/sup\u003e, demonstrating faster lithium-ion diffusion kinetics in LCO@LGPO.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAfter 200 cycles under 1C conditions, we employed high-resolution transmission electron microscopy (HRTEM) images to characterize the relationship between cathode microstructure and performance post-cycling. Figures\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e(a, b) show that the LGPO@LCO composite exhibits a thinner Cathode Electrolyte Interphase (CEI) and wider lattice spacing than the LCO surface layer. This discrepancy arises from intense side reactions between the cathode and electrolyte, where organic deposits impede Li\u003csup\u003e+\u003c/sup\u003e transport (Figs. S4, Supporting Information). Electron backscattering diffraction (EBSD) analysis of cross-sectional microstructures of electrode slices reveals that the cathode material maintains LGPO intact crystallographic integrity after 200 cycles, with no observable microcracks at the grain boundaries (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ed, f and S5). This contrasts sharply with the severe crack propagation typically reported in bare LCO under identical cycling conditions. While microcrack formation in bare LCO is widely linked to oxygen release-induced phase transformation [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e] and intergranular fracture[\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e], the absence of such defects here confirms the effectiveness of coating lithium zirconium phosphate strategy in decoupling electrochemical cycling from mechanical degradation.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eSince XPS typically has a detection depth of approximately 10 nm, we utilized XPS to investigate the cathode electrolyte interphase (CEI) of bare LCO and LCO@LGPO after 200 cycling. The CEI formed on both electrodes after 200 cycles exhibited similar chemical compositions, primarily consisting of organic carbonate substances and inorganic components (LiF and LiPOF). Fig. S6 displays the whole spectra of LCO and LCO@LGPO probed by XPS depth profile after 300 cycles. The C1s spectrum mainly consists of conductive carbon black, binder PVDF, and decomposition products from the electrolyte. The C-C bond at 284.8eV corresponds to carbon black, while the 286.5 eV C-O bond and 288.8 eV C\u0026thinsp;=\u0026thinsp;O bond originate from lithium carbonate and alkyl components decomposed in the electrolyte. These organic compounds constitute the main constituents of the CEI layer. The higher peak areas of C-O and C\u0026thinsp;=\u0026thinsp;O peaks in bare LCO's C1s spectrum may be attributed to organic decomposition components, indicating thick CEI layers formed by severe side reactions caused by highly active O and Co species at the cathode surface under high voltage. Compared with LCO and LCO@LGPO, LCO@LGPO shows smaller C-O peaks, suggesting its its advantage in inhibiting the side reactions at the electrolyte interface.\u003c/p\u003e\u003cp\u003eFurthermore, the O 1s spectrum confirmed the presence of C-O (530.5 eV) and C\u0026thinsp;=\u0026thinsp;O (532.0 eV) bonds, with a distinct Co-O peak observed in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(e, f), which further validates the protected CEI layer. For the P 2p spectrum (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ec, d), the result shows that The peak of phosphate radical migrated from 133.64 eV to 133.70 eV, indicating that surface modification reduced interfacial side reactions. The coating material in LCO@LGPO reduces byproduct formation, makes the electrochemical interfacial layer thinner, and enhances lithium-ion diffusion kinetics. Quantitative XPS analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eg) revealed that LCO@LGPO exhibited a higher ratio of lattice oxygen to inorganic components compared to post-cycling bare LCO, ensuring high chemical stability at elevated voltages, which indicates a critical factor for LCO's stable cycling performance at 4.6V. Consequently, the LGPO-coated strategy effectively inhibits Co dissolution and oxygen release during cycling, enhances surface structural stability, and stabilizes the structural integrity of the LCO cathode.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.4. Theoretical calculation\u003c/h2\u003e\u003cp\u003eTo further demonstrate the enhance interface stability mechanism of the LiCoO\u003csub\u003e2\u003c/sub\u003e/Li\u003csub\u003e2\u003c/sub\u003eZr(PO4)₂ heterojunction surfaces, a DFT analysis was performed in this study. Figures\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ea-c reveal the work functions of LCO, LGPO, and LCO/LGPO. The work function indicates the minimum energy required for electrons to escape from material surfaces. LCO exhibits a work function of 5.318 eV, while LGPO reaches 7.215 eV. Electrons flow from LCO (with lower work function) to LGPO (higher work function) until Fermi level equilibrium is achieved. The heterojunction LCO/LGPO demonstrates a work function of 5.154 eV, where the yellow portion represents electron accumulation and the blue portion indicates electron depletion [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Notably, the band gap between the valence band top and conduction band bottom of Co 3d and O 2p orbitals in LCO@LGPO is significantly narrower than that in LCO. This reduced band gap enhances electronic conductivity and accelerates charge transfer rates [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. Such orbital changes help suppress oxygen's charge compensation effect and strengthen the stability of the oxygen framework.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn Figs.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ed-f, the (104) surface crystal structure of LCO (Fig. S7, Supporting Information) consists of truncated LiO\u003csub\u003e6\u003c/sub\u003e (blue) and CoO\u003csub\u003e6\u003c/sub\u003e (green) octahedra, exposing a large amount of unbound interfacial lattice oxygen. Notably, within the LiCoO\u003csub\u003e2\u003c/sub\u003e bulk region, lattice oxygen coordinates with four lithium atoms and two cobalt atoms, forming the characteristic Li-O-Li configuration.This explains the instability of the lattice oxygen structures in LCO, particularly the irreversible alteration of interfacial lattice oxygen into oxygen. At the interface between the LiCoO\u003csub\u003e2\u003c/sub\u003e (104) surface and the LGPO (202) composite coating (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ef), Zr and P atoms prefer to bond with the oxygen atoms in the interfacial lattice through lattice distortion. This occurs because Zr-O and P-O bonds are more stable, which stabilizes the octahedral structure at the interface. The oxygen atoms at the interface have a coordination number of 5, binding exclusively to Zr or P. Consequently, we calculated the density of states (DOS) of LCO@LGPO under Co-O, Zr-O, and P-O bonding conditions (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eg). The 2p orbital of oxygen near the Fermi level is nearly zero or shifts downwards compared to similar studies (indicating reduced charge compensation capability), with significantly fewer high-energy 2p states. This suggests weaker hybridization between Co 3d and O 2p, resulting in more high-energy O 2p states near the Fermi level \u0026ndash; a mechanism that greatly enhances the stability of interfacial lattice oxygen.These findings demonstrate that zirconium-oxygen and phosphorus-oxygen bonds are more stable, and passivating interfacial lattice oxygen can improve the interfacial stability of LCO. This also indicates that charge compensation is primarily provided by Co [\u003cspan additionalcitationids=\"CR34 CR35\" citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e] (with a particularly high peak near the Fermi level, suggesting Co's enhanced capacity for charge compensation, which may be related to its rate performance). The orbital hybridization between the Co 3d orbital and O 2p orbital stabilizes the interface lattice oxygen [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. Lithium zirconium phosphate as the coating layer, situated above the Fermi level, is less likely to donate electrons during charge/discharge cycles, indicating its stable existence without corrosion during cycling. The interface exhibits electron regulation (controlled by O and Co) while maintaining physical isolation from the amorphous lithium zirconium phosphate phase, preventing decomposition.\u003c/p\u003e\u003cp\u003eFurthermore, we calculated the differential charge of LCO@LGPO in the de-lithiated state, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eh-i. Under deep de-lithiation conditions, LGPO creates an internal electric field that prevents electron leakage from LCO while providing ion channels. This configuration significantly enhances ion migration rates, thereby improving the battery's rate performance. Additionally, LGPO itself acts as a protective coating to isolate LCO from direct contact with the electrolyte, substantially reducing side decomposition reactions. These theoretical findings align with experimental observations and provide compelling evidence for enhanced structural stability during cycling processes.\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eIn this study, we achieve stable 4.6 V operation of LiCoO₂ cathodes through Li₂Zr(PO₄)₂ (LGPO) coating. The optimized 2 wt.% LGPO-coated LCO demonstrates enhanced electrochemical performance, delivering an initial capacity of 178.1 mAh\u0026middot;g⁻\u0026sup1; at 1C with 86.3% capacity retention after 200 cycles (compared to 76.0% for pristine LCO). The modified cathode exhibits superior rate capability (108.7 mAh\u0026middot;g⁻\u0026sup1; at 10C) and exceptional structural reversibility (99.7% capacity recovery at 0.1C). Through comprehensive characterization, we confirm the LGPO coating effectively reduces Li⁺/Co\u0026sup2;⁺ cation mixing from 2.71\u0026ndash;1.68%, facilitates Li⁺ diffusion through expanded interlayer spacing, and effectively mitigates kinetic constraints under high-voltage operation.\u003c/p\u003e\u003cp\u003eThe LGPO coating critically suppresses interfacial degradation mechanisms through dual protection: 1) Formation of an inorganic-rich CEI layer (LiF, LiPOF) with 30% reduction in organic components (XPS quantification); 2) Enhanced oxygen lattice stabilization via robust Zr\u0026ndash;O/P\u0026ndash;O bonding. First-principles calculations reveal the LCO/LGPO heterointerface exhibits reduced work function (5.154 eV) and stabilized oxygen framework through d-p orbital hybridization, while generating an internal electric field that simultaneously blocks electron leakage and promotes Li⁺ conduction. This integrated modification strategy successfully decouples electrochemical cycling from mechanical degradation, providing a scalable solution for developing high-voltage LCO cathodes in next-generation lithium-ion batteries.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eWu KY and Yu LS, Tang K, Wang SJ wrote the main manuscript text and Tang HW prepared figures 1-3, Wang D prepared figures 4,5, Liu Y prepared figure6, Jiang JJ prepared figures 7,8. All authors reviewed the manuscript.\u003c/p\u003e\n\u003ch2\u003eAcknowledgements\u003c/h2\u003e\n\u003cp\u003eThe authors express gratitude for the technical services provided by the Meishan vocation \u0026amp; Technical College. This work was financially supported by the Startup Foundation for Introducing Talent of Meishan Vocation \u0026amp; Technical College (No. 2024RC06), the Key Laboratories of Fine Chemicals and Surfactants in Sichuan Provincial Universities (No. 2024JXY07), and the Meishan Science and Technology Bureau project (No. 2024KJZD085). The authors extend their gratitude to Ms. Xiuyu Yin from Scientific Compass (www.shiyanjia.com) for providing invaluable assistance with the XPS analysis and HRTEM tests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eY Zhou (2022) Transition towards carbon-neutral districts based on storage techniques and spatiotemporal energy sharing with electrification and hydrogenation. 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Advanced Functional Materials. https://doi.org/10.1002/adfm.202004664\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"ionics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":" Learn more about [Ionics](https://www.springer.com/journal/11581) ","snPcode":"11581","submissionUrl":"https://mc.manuscriptcentral.com/ionics","title":"Ionics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"LiCoO2, Surface coating, Heterojunction, Structural stability, High voltage","lastPublishedDoi":"10.21203/rs.3.rs-7435444/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7435444/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eLiCoO₂ (LCO) cathodes face severe interfacial degradation ( Co/O loss and structural collapse) at high voltages (\u0026gt;4.6 V), limiting their practical deployment. To address this, we propose a heterojunction engineering strategy via surface coating with lithium zirconium phosphate (Li₂Zr(PO₄)₂, LGPO). The optimized LCO@LGPO cathode achieves an ultrahigh initial discharge capacity of 178.1 mAh·g⁻¹ at 1C (3.0–4.6 V) and retains 86.3% capacity after 200 cycles, outperforming bare LCO (76.0%). It also exhibits enhanced rate capability (108.7 mAh·g⁻¹ at 10C) and near-full capacity recovery (99.7%) when returning to 0.1C. Mechanistic studies reveal that the LGPO coating stabilizes lattice oxygen via robust Zr–O/P–O bonds, suppresses electrolyte decomposition to form a thin inorganic-rich CEI layer, and accelerates Li⁺ diffusion kinetics (DLi⁺ = 8.51 × 10⁻¹² cm²·s⁻¹, 2.4× higher than bare LCO). DFT calculations further confirm that the LCO/LGPO heterojunction reduces oxygen charge compensation and creates an internal electric field to facilitate ion transport while blocking electron leakage. This work provides a scalable surface-modification approach to enable high-energy-density LCO cathodes for next-generation batteries.\u003c/p\u003e","manuscriptTitle":"Stabilizing Interfacial Structure of LiCoO2 with Ultrahigh Capacity and Prolonged Cyclability at 4.6V","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-18 14:57:30","doi":"10.21203/rs.3.rs-7435444/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-09-29T16:19:00+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-21T05:03:24+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-18T11:56:08+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"191027368761334605104216067446501094235","date":"2025-09-14T10:42:03+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"286559976636939838809509637800646461937","date":"2025-09-13T22:49:22+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"68926721929787587585292928245870626055","date":"2025-09-13T16:09:06+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-09-11T15:34:09+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-08-25T00:14:42+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-08-25T00:14:04+00:00","index":"","fulltext":""},{"type":"submitted","content":"Ionics","date":"2025-08-22T14:25:58+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"ionics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":" Learn more about [Ionics](https://www.springer.com/journal/11581) ","snPcode":"11581","submissionUrl":"https://mc.manuscriptcentral.com/ionics","title":"Ionics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"35b70f84-5c67-480d-b746-20f0a3394b7a","owner":[],"postedDate":"September 18th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-01-24T20:53:11+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-18 14:57:30","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7435444","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7435444","identity":"rs-7435444","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}