Synthesis and Electrochemical Properties of Oxygen-deficient Crystalline Lithium Silicon Oxide for the Anode of All-Solid-state Lithium-Ion Batteries

Synthesis and Electrochemical Properties of Oxygen-deficient Crystalline Lithium Silicon Oxide for the Anode of All-Solid-state Lithium-Ion Batteries | 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 Synthesis and Electrochemical Properties of Oxygen-deficient Crystalline Lithium Silicon Oxide for the Anode of All-Solid-state Lithium-Ion Batteries SangJun Park, Min-Young Kim, YoungWoong Song, Hyeon-Beom Kim, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7653372/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract Oxygen-deficient crystalline LiSiO 2 − x materials for the anode of all-solid-state lithium batteries (ASLBs) were prepared using a sol-gel and reduction process. The resulting powder had a composition of Li 1.2 Si 1 O 1.86 , with a particle size of approximately 20 µm and good crystallinity. The change in oxygen content on the particle surface was examined by X-ray photoelectron spectroscopy, indicating that oxygen deficiency was optimized when heat-treated at 700°C after silicon addition. The powder was then mixed with graphite (Gr), Li 6.25 Al 0.25 La 3 Zr 2 O 12 (LLZO), polyethylene oxide (PEO), and Super-P in specific ratios to form a composite anode. To investigate the effect of silicon oxide on the anode, the LiSiO 2 − x :graphite ratio was varied across three compositions (10:0, 5:5, and 2:8). ASLBs were fabricated using a half-cell configuration with 2032-coin cells, consisting of a working electrode made of LiSiO 2 − x composite anode, a solid electrolyte composed of LLZO-PEO composite film, and a lithium metal counter electrode. No liquid electrolyte was used, and LiClO 4 salt was incorporated into both the anode and electrolyte. Electrochemical testing revealed that the cell with a Si:Gr ratio of 2:8 exhibited an initial capacity of 360 mAh g − 1 , confirming reduced irreversible capacity loss during cycling. All-solid-state lithium-ion batteries Oxygen-deficient crystalline Lithium silicon oxide Garnet oxide electrolyte Composite solid electrolyte Lithium-metal Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction Recently, research on all-solid-state lithium-ion batteries (ASLBs) has been actively pursued to improve the safety of conventional lithium-ion batteries particularly for medium- to large-scale applications such as electric vehicles and energy storage systems. [ 1 – 3 ]. The characteristics of the ASLBs are being studied based on the types and properties of solid electrolytes. Solid electrolyte layers (SELs) are typically composed of sulfide-based, oxide-based, and polymer-based materials, and are often combined to improve manufacturing efficiency [ 4 – 9 ]. The cathode of ASLBs is also composed of a composite material consisting of active material, solid electrolyte, and conductive additives [ 10 – 13 ], and lithium metal has attracted attention as an anode material for ASLBs due to high capacity and voltage. However, the use of lithium metal as an anode is limited due to the challenges in controlling reactivity at the interface with the solid electrolyte [ 14 – 16 ]. Therefore, there is a growing need to explore high-capacity anode materials that can replace lithium metal, and silicon-based materials are being considered as a promising candidate [ 17 – 20 ]. As an anode material, pure silicon has the highest theoretical capacity of about 3570 mAh g − 1 . However, it undergoes the largest volume changes during charge and discharge [ 21 – 23 ]. To mitigate this issue, various research approaches are being explored, including silicon alloys, silicon nanowires, silicon oxides, and silicon-carbon composites [ 24 – 30 ]. Among silicon-based materials, silicon oxide (SiOₓ) in particular, as it is a combination of silicon and oxygen, has a lower capacity than pure silicon in lithium-ion batteries. However, it has the property of acting as a buffer to mitigate the volume changes of silicon during the charge and discharge process. In the conventional lithium-ion batteries, the discharge capacity of silicon oxide (SiOₓ) anode materials in half-cell evaluations can vary depending on the form of silicon oxide and the synthesis method [ 31 – 34 ]. Generally, the initial discharge capacity of SiOₓ anodes is reported to be in the range of approximately 200 to 700 mAh g − 1 [ 34 ]. However, there are still several drawbacks before the application of SiO x , such as low intrinsic electronic conductivity and high irreversible capacity in the first cycle, which lead to low electrochemical activity and low initial coulombic efficiency [ 35 ]. Although the use of silicon oxide in all-solid-state batteries has not yet been demonstrated, it is expected that the initial capacity would be further reduced in these systems. To improve cycle capacity characteristics of silicon oxide for all-solid state lithium ion batteries, additional research efforts are required on SiO 2 − x via oxygen deficiency, lithium doping, and compositing with graphite and polymers, etc. In this study, the oxygen-deficient structure of silicon oxide is expected to alleviate the volume expansion of silicon, enhance conductivity, and improve the efficiency of lithium ion insertion and extraction. In this study, oxygen-deficient silicon oxide (LiSiO 2 − x ) was synthesized via lithium pre-doping using sol-gel process, and used to fabricate composite working electrodes with a garnet-type oxide solid electrolyte (Al-doped Li 6.25 Al 0.25 La 3 Zr 2 O 12 , LLZO), polyethylene oxide (PEO) polymer, graphite, and conductive materials. The composite solid electrolyte layer composed of LLZO and PEO was used, and a half-cell with lithium metal as the CE was evaluated for the electrochemical behavior of LiSiO 2 − x and its composite anode. 2. Experimental 2.1. Synthesis and characterization of LiSiO 2 − x powders Figure 1 shows the synthesis process of LiSiO 2 − x powder, which follows a sol-gel-like process. First, TEOS (Tetraethyl orthosilicate) solution mixed with ethanol at a certain ratio and a lithium hydroxide solution mixed with distilled water were prepared, respectively. The two solutions were then combined in a weight ratio of 1:0.2 (Si:Li) to produce a mixture. This mixture was stirred at 50°C for 12 h to synthesize an amorphous lithium silicon oxide precursor through a sol-gel reaction. Additionally, the mixture was dried at 80°C for one day, followed by heat treatment in an air atmosphere at 400°C for 3 h. It was then heat-treated in a reductive atmosphere at 700°C for 10 h to produce LiSiO 2 as sample #1 as shown Table I. Table I. Composition condition of lithium silicon oxide and anode slurry for Half-cells. Sample Process condition of lithium silicon oxide Slurry condition of anode (weight ratio) Sample #1 LiSiO 2 was calcined at 700°C for 10 h in a reducing atmosphere Active material (LiSiO 2 ) : PEO : LLZO : S-P = 51 : 30 : 4 : 15 Sample #2 Si was added to LiSiO 2 , ball-milled, and then calcined at 700°C for 10 h in a reducing atmosphere. (LiSiO 2-x = LiSiO 2 + Si) Active material (LiSiO 2-x = LiSiO 2 + Si) : PEO : LLZO : S-P = 51 : 30 : 4 : 15 (LiSiO 2 : Si = 1:1) Sample #3 Si was added to LiSiO 2 , ball-milled, and then calcined at 950°C for 3 h in a reducing atmosphere. (LiSiO 2-x = LiSiO 2 + Si) Active material (LiSiO 2-x = LiSiO 2 + Si) : PEO : LLZO : S-P = 51 : 30 : 4 : 15 (LiSiO 2 : Si= 1:1) Sample #4 Same condition of Sample #2 Active material (LiSiO 2-x + Graphite) : PEO : LLZO : S-P = 51 : 30 : 12 : 7 (LiSiO 2-x : Graphite = 5 : 5) Sample #5 Same condition of Sample #2 Active material (LiSiO 2-x + Graphite) : PEO : LLZO : S-P = 51 : 30 : 12 : 7 (LiSiO 2-x : Graphite = 2 : 8) Secondly, after synthesizing the amorphous LiSiO 2 , pure silicon (Si, 215619, sigma-aldrich) powder was added in a weight ratio of 1:1 with the amorphous LiSiO 2 . The pure Si material used here is a nano powder with a size range of 10–20 nm, and it has a density of 2.2–2.6 g/ml at 25°C. The mixture was then ball-milled and heat-treated in a reductive atmosphere (Ar and 5% H 2 ) at 700°C for 10 h to produce Sample #2 as an oxygen-deficient crystalline LiSiO 2 − x (0 < x < 2). Thirdly, except for the heat treatment at 950°C for 3 h instead of 700°C for 10 h in a reductive atmosphere, the same method as Sample #2 was used to produce oxygen-deficient crystalline LiSiO 2 − x (0 < x < 2) as Sample #3. X-ray diffraction (XRD) patterns of the powders were recorded by X-ray diffraction analysis (X’Pert Pro, PANalytical, Netherlands) using Cu Kα radiation (λ = 1.5406Å) in the 2θ range of 10–90°. The morphology of powders was observed by scanning electron microscopy (SEM, FE-SEM, Hitachi, S-4700, Japan) and elemental analysis was conducted on an energy dispersive spectroscopy (EDS) attached to SEM. The synthesized powders were analyzed using X-ray Photoelectron Spectroscopy (XPS, ThermoFisher, K-ALPHA, USA) to examine the oxygen content and the degree of oxygen deficiency on the particle surface. 2.2. Preparation of LiSiO 2 − x composite anode with solid electrolyte Table I shows the detailed condition for the synthesis of lithium silicon oxide for each sample, as well as the composition conditions of the anode slurry for the half-cell using it. Firstly, the three types (Sample #1∼Sample #3) of LiSiO 2 and LiSiO 2 − x were mixed with solid electrolyte compositions of PEO, LLZO, and Super-P in a weight ratio of 51:30:4:15 to prepare a composite anode for solid-state batteries. In this process, LLZO was synthesized in-house, while PEO (MW = 200,000, USA) and Super-P (IMERYS Graphite & Carbon, Japan) were purchased commercially. ACN (Aldrich Co., Ltd.) was used as the solvent to prepare the slurry. That is, to fabricate the slurry mixture, the active material, Super-P, Al-LLZO powder were weighed in proportion with the anode composition, and the respective materials were mixed and pulverized uniformly for 20–30 min in a mortar. PEO binder solution with LiClO 4 salt was then added to the dry mixture and stirred in a Planetary Centrifugal Mixer (ARE-310, Thinky, Tapan) at 2,000 rpm for about 20 min, then coated onto a Cu foil with a thickness of 20 to 40 µm. Afterward, the electrode fabrication was completed by vacuum drying at a temperature of 50 to 70°C. In this process, the PEO binder was prepared such that the weight ratio of PEO (MW = 200,000) to LiClO 4 was [PEO]:[LiClO 4 ] = 15:1. The second attempt involved preparing electrodes by replacing part of the LiSiO 2 − x content in the optimal composition as Sample #2 with graphite (Sigma Aldrich, USA). Specifically, the weight ratios of LiSiO 2 − x to graphite were set to 5:5 and 2:8 as Sample #4 and Sample #5. 2.3. Preparation of flexible SE layer with LLZO/PEO Al-doped LLZO (Al-LLZO, Li 6.25 La 3 Zr 2 Al 0.25 O 12 ), PEO (Mw = 200,000, Sigma Aldrich, USA), LiClO 4 (JUNSEI, Japan) were used as starting materials. Al-LLZO powder was synthesized in house. Then, PEO and the lithium salt with an [EO]:[Li] molar ratio of 15:1 were mixed and stirred for 24 h to prepare a PEO binder solution. Next, the weight ratio of Al-LLZO powder in the SE sheet was fixed at 70 wt%, and the slurry mixture was prepared by mixing Al-LLZO powder and PEO/salts in a mixer for 20 min. Finally, the slurry was cast onto a PET film and dried at room temperature for 24 h. As a result, it was fabricated in the form of a thin film with a thickness of 150 µm. 2.4. Fabrication of half-cells for ASLBs Half-cells for ASLBs were designed and assembled with the type of 2032-coin cells. As for the design of the cell, lithium silicon-oxide composite materials (LiSiO 2 − x /Graphite/Super-P/LLZO/PEO) were used as the WE, oxide-based materials (LLZO/PEO/Salt) were applied to the SE layer, and lithium metal was applied to the CE, respectively. Charging/discharging experiments were conducted at 70°C through an automatic battery cycler system (WBCS3000, Wonatech, Korea). Charging of the half-cell was performed in CC-CV mode with a current of 0.05-0.02C, and the discharging was carried out at 0.05C, with a cut-off at 1.5V. 3. Results and Discussion Figure 2 shows the XRD peak patterns of the amorphous LiSiO x precursor heat-treated at 400°C in the synthesis process of Fig. 1 , LiSiO 2 calcined at 700°C in a reducing atmosphere, and LiSiO 2 − x after adding Si and calcining at 700°C and 950°C in a reducing atmosphere. Figure 2 (a) shows the typical XRD peak pattern of amorphous LiSiOx, exhibiting a broad peak in the 15–30° range, which corresponds to the characteristic pattern of amorphous LiSiO₂. In the case of the peak for the amorphous LiSiO x after heat treatment at 700°C in a reducing atmosphere in Fig. 2 (b), it can be observed that the peak of LiSiO 2 of Sample #1 appears as a distinct crystallization peak along with some impurities. Additionally, in the case of Sample #2, which was subjected to calcination under the same conditions with the addition of pure Si, the intensity of the LiSiO 2 peak was relatively weaker than that of Sample #1, and a new Si peak was clearly observed. Furthermore, in the case of Sample #3, where the calcination temperature was increased to 950°C, there was a tendency for the intensities of the main LiSiO 2 and Si peaks to decrease, which indicates changes in the crystal structure and particle morphology. Table II. Rietveld refinement of XRD analysis for crystalline LiSiO 2 powder, and Si added to LiSiO 2 − x powder with calcination temperature. Sample a(Å) b(Å) c(Å) Crystallite Size (Å) Crystal structure Sample #1 5.82956 14.6214 4.78096 484 Monoclinic Sample #2 5.82822 14.6184 4.77956 740.1 Monoclinic Sample #3 5.83843 14.6236 4.78178 558.3 Orthorhombic Table II shows the results of the rietveld analysis for Samples #1–#3, including the lattice constants, lattice sizes, and crystal structures, based on the XRD peaks related to Fig. 2 of the synthesized materials. Compared to Sample #1, Sample #2, which was treated with Si addition at 700°C in a reducing atmosphere, shows a decrease in lattice constant. However, for Sample #3, where the reduction treatment temperature was increased to 950°C, the lattice constant increases again, and the crystallite size exhibits the largest value in Sample #2. In other words, Sample #1 and #2 exhibit a monoclinic structure, while Sample #3 shows an orthorhombic structure. This indicates that as the reduction temperature increases, the crystal structure changes. Figure 3 shows the SEM images of Sample #1, Sample #2 calcined at 700°C in a reducing atmosphere, and Sample #3 with Si addition, all produced according to the process in Fig. 1 . Specifically, Figs. 3 (a) and 3(b) present the SEM images of Sample #1 at 1,000× and 10,000× magnification, respectively; Figs. 3 (c) and 3(d) correspond to Sample #2 under the same magnifications; and Figs. 3 (e) and 3(f) show the 1,000× and 10,000× magnified images of Sample #3. In the case of Sample #1 with the amorphous LiSiO x , fine primary particles of about 1–2 µm were observed. However, Sample #2 was heat-treated at 700°C, a phenomenon of aggregation into secondary particles of about 10 µm was observed. Additionally, Sample #3 was mixed with pure Si nanopowder, ball-milled, and then calcined. It was found to consist of finer primary particles compared to Sample #1. Figure 4 shows XPS spectra of Si2p, O1s and Li1p for amorphous LiSiO x calcined at 400 ℃, LiSiO 2 powder calcined at 700 ℃, and Si added to LiSiO 2 powder (LiSiO 2 − x ) calcined at 700 ℃ and atomic ratio of O1s/Si2p with Samples. The precursor, lithium-doped silicon oxide(LiSiO x ), and LiSiO 2 − x exhibits a different trend in its spectra compared to the conventional SiO x material [ 36 – 38 ]. Figure 4 (a) shows that only Si 3+ is detected at 102.5–103 eV, which is different from the main phase of Si 4+ in the conventional SiO x . This indicates the presence of the LiSiO x phase, as shown in the XRD pattern. Figure 4 (b) shows the O1s pattern, where all three binding energy peaks are observed in the 529–534 eV range, with the main peaks at 532.2 eV and 531 eV, respectively. In this process, The peak at 531.2 eV is known to correspond to Si-O-Li bonding. Figure 4 (c) shows the Li1s pattern with the main peak at 55 eV, which indicates unreacted impurities, such as typical lithium compounds like LiOH. This is consistent with the results from the XRD peak pattern. Figure 4 (d) shows the atomic ratio of O1s/Si2p for each sample, indicating that Sample #2 has a higher oxygen deficiency compared to Sample #1. In other words, when pure Si nanoparticles were added, ball-milled, and then subjected to calcination during the synthesis process, the composition of the particles was confirmed to be Li 1.2 Si 1 O 1.86 . Figure 5 shows the initial charge-discharge curves of Sample #1, Sample #2, and Sample #3, respectively. From this, it can be seen that the discharge capacity varies depending on the addition of Si and the calcination temperature during synthesis of the materials. In the first cycle, discharge capacity, Sample #1, Sample #2, and Sample #3 shows 70, 460, 290 mAhg − 1 , respectively, indicating that Sample #2 has a relatively higher capacity compared to the other samples. Sample #1 not only shows a low initial capacity but also exhibits almost no change in capacity over cycling. Samples #2 and #3 exhibited significantly higher initial capacities due to Si addition, yet both showed rapid capacity fading during cycling. As shown in Fig. 5 (d), the increase in the initial capacity is not due to the behavior of LiSiO x , but rather attributed to the characteristics of pure Si in the composition of LiSiO 2 − x . Furthermore, the higher initial capacity of Sample #2 compared to Sample #3 is presumed to be due to the lower calcination temperature, which likely resulted in a finer powder particle size in the anode. The reduced particle size is presumed to increase the reaction surface area, thereby enhancing lithium-ion accessibility and contributing to the higher initial capacity. Therefore, based on the characteristics of Sample #2, additional experiments were conducted involving its mixture with graphite to further optimize the conditions of the anode active material as shown in the Table I. Figure 6 shows the initial capacity and cycling characteristics of Sample #4 and Sample #5, which are based on Si and include graphite as an additive, compared to the active material of Sample #2. Specifically, LiSiO 2 − x and graphite were mixed in weight ratios of 2:8 for Sample #4 and 5:5 for Sample #5. Compared to the charge-discharge curve of Sample #2 based on LiSiO 2 − x , the addition of graphite to LiSiO 2 − x results in noticeable changes in the charge-discharge behavior. Specifically, as the graphite content increases, the irreversible capacity during charging decreases, and the discharge voltage plateau characteristic of graphite becomes more pronounced. As a result, the initial discharge capacity decreases with increasing graphite content, but the cycling capacity improves relatively. Figure 7 (a–c) presents the differential charge–discharge curves (dQ/dV) for the first cycle of Samples #2, #4, and #5, corresponding to the charge–discharge profiles shown in Fig. 6 . Figure 7 (d) compares the 1st and 2nd cycles of Sample #4. That is, Sample #1 exhibits the typical oxidation (0.42 V) and reduction (0.15 V) peaks characteristic of LiSiO 2 − x . In contrast, Sample #2 that contains 50 wt% graphite shows additional peaks corresponding to both Si and graphite. In this process, as the graphite content increases as in Sample #4 and Sample #5, the original Si-related peaks decrease. In particular, Fig. 7 (d) presents the differential curves for the 1st and 2nd charge-discharge cycles of Sample #4, showing a significant difference between the two cycles. Specifically, most of the Si-related peaks disappear in the 2nd cycle, and the curve is dominated by graphite-related peaks. Furthermore, as the graphite content increases, the irreversible charge capacity in the first cycle decreases, and the capacity difference in the second cycle also shows a decreasing trend. These results confirm that when LiSiO 2 − x is composited with graphite, and as the proportion of graphite increases, the charge–discharge capacity improves significantly by more than twofold in some cases. 4. Conclusions This study investigated the structural and electrochemical characteristics of LiSiO 2 − x -based composite anodes synthesized through sol-gel-derived precursors, with variations in calcination temperature and additive composition. XRD and Rietveld refinement results demonstrated that the initial amorphous LiSiO x transformed into a monoclinic LiSiO 2 phase after calcination at 700°C (Sample #1), and further evolved into an orthorhombic LiSiO 2 − x structure at 950°C (Sample #3) when combined with Si nanopowders. XPS analysis confirmed the presence of oxygen-deficient Li 1.2 Si 1 O 1.86 composition and Si 3+ oxidation states, supporting the structural deviation from conventional SiO x systems. Electrochemical evaluation revealed that Sample #2, synthesized by incorporating nano-sized Si and calcining at 700°C, achieved the highest initial discharge capacity of 460 mAh g⁻¹. However, this came at the expense of rapid capacity fading due to intrinsic Si instability. To address this, LiSiO 2 − x was composited with graphite to form Sample #4 and Sample #5. These samples exhibited improved cycling performance, with Sample #5 (graphite-rich, 2:8 ratio) retaining over twice the capacity of Sample #2 after multiple cycles. Differential capacity analysis confirmed that graphite effectively buffered the volume expansion of Si and stabilized the electrochemical interface. Overall, this work provides a promising direction for the design of high-capacity and stable anode materials by tailoring oxygen-deficient LiSiO 2 − x and optimizing composite ratios with graphite. The combination of controlled structural transformation, oxygen deficiency, and carbon compositing enables enhanced electrochemical performance, making the developed LiSiO 2 − x /graphite composites suitable for future ASLB applications. Further work will focus on interface engineering and long-term durability testing to advance the practical viability of these composite anodes. Declarations Author Contribution S.J.P. performed the synthesis of LiSiO₂₋ₓ materials, carried out electrochemical measurements, and drafted the initial manuscript.M.-Y.K. contributed to the preparation of solid electrolyte composites and assisted in electrochemical testing.Y.W.S. carried out structural characterization including XRD and XPS analysis and contributed to data interpretation.H.-B.K. assisted in material preparation, SEM measurements, and analysis of particle morphology.W.J.K. supported data curation, figure preparation, and validation of experimental results.B.-S.K. supervised the project design, provided critical revisions to the manuscript, and guided the discussion on materials chemistry.H.-S.K. conceived the overall research idea, coordinated the project, and finalized the manuscript.All authors reviewed and approved the final version of the manuscript. 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Popovich, “Atomic layer deposition of lithium–nickel–silicon oxide cathode material for thin-film lithium-ion batteries.” Energies , 13, 2345 (2020). H. Wu, L. Zheng, J. Zhan, N. Du, W. Liu, J. Ma, L. Su, L. Wang, “Recycling silicon-based industrial waste as sustainable sources of Si/SiO₂ composites for high-performance Li-ion battery anodes.” J. Power Sources , 449, 227513 (2020). N. Kim, W. Lee, J. Kim, D. Kim, B. Jang, “Synthesis of passively prelithiated SiOₓ nanoparticles for Li-ion battery anode.” J. Am. Ceram. Soc. , 106, 4554–4566 (2023) Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 03 Nov, 2025 Reviews received at journal 31 Oct, 2025 Reviews received at journal 25 Oct, 2025 Reviewers agreed at journal 14 Oct, 2025 Reviewers agreed at journal 14 Oct, 2025 Reviewers invited by journal 13 Oct, 2025 Editor assigned by journal 24 Sep, 2025 Submission checks completed at journal 24 Sep, 2025 First submitted to journal 18 Sep, 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-7653372","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":534108837,"identity":"dfc5f152-62cb-43da-9e76-da3e4f5ad2cc","order_by":0,"name":"SangJun Park","email":"","orcid":"","institution":"Korea Institute of Industrial Technology (KITECH)","correspondingAuthor":false,"prefix":"","firstName":"SangJun","middleName":"","lastName":"Park","suffix":""},{"id":534108838,"identity":"ce92153e-c2db-4847-a98a-921a944c1b8a","order_by":1,"name":"Min-Young Kim","email":"","orcid":"","institution":"Korea Institute of Industrial Technology 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14:45:41","extension":"html","order_by":18,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":115124,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7653372/v1/f3bb3aaee81bd3a29fef0884.html"},{"id":94456960,"identity":"f3f40b2b-722b-429e-a894-bb32bce7c8c6","added_by":"auto","created_at":"2025-10-27 14:45:18","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":225469,"visible":true,"origin":"","legend":"\u003cp\u003eSynthesis process of oxygen-deficient crystalline LiSiO\u003csub\u003e2-x\u003c/sub\u003e powder.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7653372/v1/e7bbe5f94a695b0cd6078d0e.png"},{"id":94457227,"identity":"a92120b0-621b-4500-9f23-04d3737996cc","added_by":"auto","created_at":"2025-10-27 14:45:31","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":267865,"visible":true,"origin":"","legend":"\u003cp\u003eXRD pattern of LiSiOx precursor (a), crystalline LiSiO\u003csub\u003e2\u003c/sub\u003e powder\u0026nbsp; and Si added to LiSiO\u003csub\u003e2-x\u003c/sub\u003e powder with calcination temperature (b).\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7653372/v1/73397fc380761306688e542c.png"},{"id":94457363,"identity":"0dff0830-5fe1-478f-9f64-a08c66c00b8a","added_by":"auto","created_at":"2025-10-27 14:45:47","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":479019,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of amorphous LiSiO\u003csub\u003ex\u003c/sub\u003e calcined at 400 ℃ (a, b), LiSiO\u003csub\u003e2\u003c/sub\u003e powder calcined at 700 ℃ (c, d), and Si added to LiSiO\u003csub\u003e2-x\u003c/sub\u003e powder calcined at 700 ℃ (e, f).\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7653372/v1/1f502e51f6116371ee729d25.png"},{"id":94456708,"identity":"c93ce01a-5f10-4171-8f59-0d0ec9b8cc3f","added_by":"auto","created_at":"2025-10-27 14:45:02","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":372071,"visible":true,"origin":"","legend":"\u003cp\u003eXPS spectra of (a) Si 2p, (b) O 1s, and (c) Li 1s for the amorphous LiSiO\u003csub\u003ex\u003c/sub\u003e precursor calcined at 400 °C (black), LiSiO\u003csub\u003e2\u003c/sub\u003e powder calcined at 700 °C (Sample #2, red), and Si-added LiSiO\u003csub\u003e2-x\u003c/sub\u003e powder calcined at 700 °C (Sample #3, blue). (d) Atomic ratio of O 1s to Si 2p for each sample.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7653372/v1/732ce07cd5cbf05c767a6f10.png"},{"id":94456173,"identity":"6b889b32-6e34-4e0b-afc6-71c3c79f0934","added_by":"auto","created_at":"2025-10-27 14:44:20","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":283233,"visible":true,"origin":"","legend":"\u003cp\u003eInitial charge/discharge profiles of (a) Sample #1, (b) Sample #2, and (c) Sample #3, and (d) cycling characteristics of the samples.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7653372/v1/c2f95b0169f9c0f1386f84e6.png"},{"id":94457272,"identity":"d5a8c34c-5428-4063-a685-a67ee1cf8d63","added_by":"auto","created_at":"2025-10-27 14:45:37","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":282823,"visible":true,"origin":"","legend":"\u003cp\u003eInitial charge–discharge curves of Sample #2 (a), Sample #4 (b), and Sample #5 (c), and cycling characteristics of the three samples (d).\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-7653372/v1/dcbf4c4ff963308dd9cfa785.png"},{"id":94457229,"identity":"8305b60e-27d2-484f-b3ee-84a6c7314020","added_by":"auto","created_at":"2025-10-27 14:45:32","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":272347,"visible":true,"origin":"","legend":"\u003cp\u003eDifferential charge–discharge curves (dQ/dV) for the first cycle of (a) Sample #2, (b) Sample #4, and (c) Sample #5. (d) Comparison of the 1st and 2nd cycles of Sample #4.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-7653372/v1/29a5bafed2ab32eb8442ad6b.png"},{"id":94491151,"identity":"1ee80587-38ff-4d68-bde8-b4a0a47e0b11","added_by":"auto","created_at":"2025-10-27 17:23:28","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2929217,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7653372/v1/439a7eb2-cd9a-4888-bed6-5710f6f2efc4.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Synthesis and Electrochemical Properties of Oxygen-deficient Crystalline Lithium Silicon Oxide for the Anode of All-Solid-state Lithium-Ion Batteries","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eRecently, research on all-solid-state lithium-ion batteries (ASLBs) has been actively pursued to improve the safety of conventional lithium-ion batteries particularly for medium- to large-scale applications such as electric vehicles and energy storage systems. [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. The characteristics of the ASLBs are being studied based on the types and properties of solid electrolytes. Solid electrolyte layers (SELs) are typically composed of sulfide-based, oxide-based, and polymer-based materials, and are often combined to improve manufacturing efficiency [\u003cspan additionalcitationids=\"CR5 CR6 CR7 CR8\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The cathode of ASLBs is also composed of a composite material consisting of active material, solid electrolyte, and conductive additives [\u003cspan additionalcitationids=\"CR11 CR12\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], and lithium metal has attracted attention as an anode material for ASLBs due to high capacity and voltage. However, the use of lithium metal as an anode is limited due to the challenges in controlling reactivity at the interface with the solid electrolyte [\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Therefore, there is a growing need to explore high-capacity anode materials that can replace lithium metal, and silicon-based materials are being considered as a promising candidate [\u003cspan additionalcitationids=\"CR18 CR19\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. As an anode material, pure silicon has the highest theoretical capacity of about 3570 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. However, it undergoes the largest volume changes during charge and discharge [\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. To mitigate this issue, various research approaches are being explored, including silicon alloys, silicon nanowires, silicon oxides, and silicon-carbon composites [\u003cspan additionalcitationids=\"CR25 CR26 CR27 CR28 CR29\" citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Among silicon-based materials, silicon oxide (SiOₓ) in particular, as it is a combination of silicon and oxygen, has a lower capacity than pure silicon in lithium-ion batteries. However, it has the property of acting as a buffer to mitigate the volume changes of silicon during the charge and discharge process. In the conventional lithium-ion batteries, the discharge capacity of silicon oxide (SiOₓ) anode materials in half-cell evaluations can vary depending on the form of silicon oxide and the synthesis method [\u003cspan additionalcitationids=\"CR32 CR33\" citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Generally, the initial discharge capacity of SiOₓ anodes is reported to be in the range of approximately 200 to 700 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. However, there are still several drawbacks before the application of SiO\u003csub\u003ex\u003c/sub\u003e, such as low intrinsic electronic conductivity and high irreversible capacity in the first cycle, which lead to low electrochemical activity and low initial coulombic efficiency [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAlthough the use of silicon oxide in all-solid-state batteries has not yet been demonstrated, it is expected that the initial capacity would be further reduced in these systems. To improve cycle capacity characteristics of silicon oxide for all-solid state lithium ion batteries, additional research efforts are required on SiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e via oxygen deficiency, lithium doping, and compositing with graphite and polymers, etc. In this study, the oxygen-deficient structure of silicon oxide is expected to alleviate the volume expansion of silicon, enhance conductivity, and improve the efficiency of lithium ion insertion and extraction.\u003c/p\u003e\u003cp\u003eIn this study, oxygen-deficient silicon oxide (LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e) was synthesized via lithium pre-doping using sol-gel process, and used to fabricate composite working electrodes with a garnet-type oxide solid electrolyte (Al-doped Li\u003csub\u003e6.25\u003c/sub\u003eAl\u003csub\u003e0.25\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003eZr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e12\u003c/sub\u003e, LLZO), polyethylene oxide (PEO) polymer, graphite, and conductive materials. The composite solid electrolyte layer composed of LLZO and PEO was used, and a half-cell with lithium metal as the CE was evaluated for the electrochemical behavior of LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e and its composite anode.\u003c/p\u003e"},{"header":"2. Experimental","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Synthesis and characterization of LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e powders\u003c/h2\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows the synthesis process of LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e powder, which follows a sol-gel-like process. First, TEOS (Tetraethyl orthosilicate) solution mixed with ethanol at a certain ratio and a lithium hydroxide solution mixed with distilled water were prepared, respectively. The two solutions were then combined in a weight ratio of 1:0.2 (Si:Li) to produce a mixture. This mixture was stirred at 50\u0026deg;C for 12 h to synthesize an amorphous lithium silicon oxide precursor through a sol-gel reaction. Additionally, the mixture was dried at 80\u0026deg;C for one day, followed by heat treatment in an air atmosphere at 400\u0026deg;C for 3 h. It was then heat-treated in a reductive atmosphere at 700\u0026deg;C for 10 h to produce LiSiO\u003csub\u003e2\u003c/sub\u003e as sample #1 as shown Table I.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eTable I. Composition condition of lithium silicon oxide and anode slurry for Half-cells.\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eProcess condition of\u003c/p\u003e\u003cp\u003elithium silicon oxide\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSlurry condition of anode\u003c/p\u003e\u003cp\u003e(weight ratio)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample #1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eLiSiO\u003csub\u003e2\u003c/sub\u003e was calcined at 700\u0026deg;C for 10 h in a reducing atmosphere\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eActive material (LiSiO\u003csub\u003e2\u003c/sub\u003e) : PEO : LLZO : S-P\u0026thinsp;=\u0026thinsp;51 : 30 : 4 : 15\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample #2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSi was added to LiSiO\u003csub\u003e2\u003c/sub\u003e, ball-milled, and then calcined at 700\u0026deg;C for 10 h in a reducing atmosphere. (LiSiO\u003csub\u003e2-x\u003c/sub\u003e = LiSiO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;Si)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eActive material (LiSiO\u003csub\u003e2-x\u003c/sub\u003e = LiSiO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;Si)\u003c/p\u003e\u003cp\u003e: PEO : LLZO : S-P = 51 : 30 : 4 : 15 (LiSiO\u003csub\u003e2\u003c/sub\u003e : Si\u0026thinsp;=\u0026thinsp;1:1)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample #3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSi was added to LiSiO\u003csub\u003e2\u003c/sub\u003e, ball-milled, and then calcined at 950\u0026deg;C for 3 h in a reducing atmosphere. (LiSiO\u003csub\u003e2-x\u003c/sub\u003e = LiSiO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;Si)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eActive material (LiSiO\u003csub\u003e2-x\u003c/sub\u003e = LiSiO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;Si)\u003c/p\u003e\u003cp\u003e: PEO : LLZO : S-P\u003c/p\u003e\u003cp\u003e=\u0026thinsp;51 : 30 : 4 : 15 (LiSiO\u003csub\u003e2\u003c/sub\u003e : Si= 1:1)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample #4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSame condition of Sample #2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eActive material (LiSiO\u003csub\u003e2-x\u003c/sub\u003e + Graphite) : PEO : LLZO : S-P\u0026thinsp;=\u0026thinsp;51 : 30 : 12 : 7 (LiSiO\u003csub\u003e2-x\u003c/sub\u003e : Graphite = 5 : 5)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample #5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSame condition of Sample #2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eActive material (LiSiO\u003csub\u003e2-x\u003c/sub\u003e + Graphite) : PEO : LLZO : S-P\u0026thinsp;=\u0026thinsp;51 : 30 : 12 : 7 (LiSiO\u003csub\u003e2-x\u003c/sub\u003e : Graphite = 2 : 8)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eSecondly, after synthesizing the amorphous LiSiO\u003csub\u003e2\u003c/sub\u003e, pure silicon (Si, 215619, sigma-aldrich) powder was added in a weight ratio of 1:1 with the amorphous LiSiO\u003csub\u003e2\u003c/sub\u003e. The pure Si material used here is a nano powder with a size range of 10\u0026ndash;20 nm, and it has a density of 2.2\u0026ndash;2.6 g/ml at 25\u0026deg;C. The mixture was then ball-milled and heat-treated in a reductive atmosphere (Ar and 5% H\u003csub\u003e2\u003c/sub\u003e) at 700\u0026deg;C for 10 h to produce Sample #2 as an oxygen-deficient crystalline LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e (0\u0026thinsp;\u0026lt;\u0026thinsp;x\u0026thinsp;\u0026lt;\u0026thinsp;2).\u003c/p\u003e\u003cp\u003eThirdly, except for the heat treatment at 950\u0026deg;C for 3 h instead of 700\u0026deg;C for 10 h in a reductive atmosphere, the same method as Sample #2 was used to produce oxygen-deficient crystalline LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e (0\u0026thinsp;\u0026lt;\u0026thinsp;x\u0026thinsp;\u0026lt;\u0026thinsp;2) as Sample #3.\u003c/p\u003e\u003cp\u003eX-ray diffraction (XRD) patterns of the powders were recorded by X-ray diffraction analysis (X\u0026rsquo;Pert Pro, PANalytical, Netherlands) using Cu Kα radiation (λ\u0026thinsp;=\u0026thinsp;1.5406\u0026Aring;) in the 2θ range of 10\u0026ndash;90\u0026deg;. The morphology of powders was observed by scanning electron microscopy (SEM, FE-SEM, Hitachi, S-4700, Japan) and elemental analysis was conducted on an energy dispersive spectroscopy (EDS) attached to SEM.\u003c/p\u003e\u003cp\u003eThe synthesized powders were analyzed using X-ray Photoelectron Spectroscopy (XPS, ThermoFisher, K-ALPHA, USA) to examine the oxygen content and the degree of oxygen deficiency on the particle surface.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Preparation of LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e composite anode with solid electrolyte\u003c/h2\u003e\u003cp\u003eTable I shows the detailed condition for the synthesis of lithium silicon oxide for each sample, as well as the composition conditions of the anode slurry for the half-cell using it. Firstly, the three types (Sample #1\u0026sim;Sample #3) of LiSiO\u003csub\u003e2\u003c/sub\u003e and LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e were mixed with solid electrolyte compositions of PEO, LLZO, and Super-P in a weight ratio of 51:30:4:15 to prepare a composite anode for solid-state batteries. In this process, LLZO was synthesized in-house, while PEO (MW\u0026thinsp;=\u0026thinsp;200,000, USA) and Super-P (IMERYS Graphite \u0026amp; Carbon, Japan) were purchased commercially. ACN (Aldrich Co., Ltd.) was used as the solvent to prepare the slurry. That is, to fabricate the slurry mixture, the active material, Super-P, Al-LLZO powder were weighed in proportion with the anode composition, and the respective materials were mixed and pulverized uniformly for 20\u0026ndash;30 min in a mortar. PEO binder solution with LiClO\u003csub\u003e4\u003c/sub\u003e salt was then added to the dry mixture and stirred in a Planetary Centrifugal Mixer (ARE-310, Thinky, Tapan) at 2,000 rpm for about 20 min, then coated onto a Cu foil with a thickness of 20 to 40 \u0026micro;m. Afterward, the electrode fabrication was completed by vacuum drying at a temperature of 50 to 70\u0026deg;C. In this process, the PEO binder was prepared such that the weight ratio of PEO (MW\u0026thinsp;=\u0026thinsp;200,000) to LiClO\u003csub\u003e4\u003c/sub\u003e was [PEO]:[LiClO\u003csub\u003e4\u003c/sub\u003e]\u0026thinsp;=\u0026thinsp;15:1. The second attempt involved preparing electrodes by replacing part of the LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e content in the optimal composition as Sample #2 with graphite (Sigma Aldrich, USA). Specifically, the weight ratios of LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e to graphite were set to 5:5 and 2:8 as Sample #4 and Sample #5.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Preparation of flexible SE layer with LLZO/PEO\u003c/h2\u003e\u003cp\u003eAl-doped LLZO (Al-LLZO, Li\u003csub\u003e6.25\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003eZr\u003csub\u003e2\u003c/sub\u003eAl\u003csub\u003e0.25\u003c/sub\u003eO\u003csub\u003e12\u003c/sub\u003e), PEO (Mw\u0026thinsp;=\u0026thinsp;200,000, Sigma Aldrich, USA), LiClO\u003csub\u003e4\u003c/sub\u003e (JUNSEI, Japan) were used as starting materials. Al-LLZO powder was synthesized in house. Then, PEO and the lithium salt with an [EO]:[Li] molar ratio of 15:1 were mixed and stirred for 24 h to prepare a PEO binder solution. Next, the weight ratio of Al-LLZO powder in the SE sheet was fixed at 70 wt%, and the slurry mixture was prepared by mixing Al-LLZO powder and PEO/salts in a mixer for 20 min. Finally, the slurry was cast onto a PET film and dried at room temperature for 24 h. As a result, it was fabricated in the form of a thin film with a thickness of 150 \u0026micro;m.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Fabrication of half-cells for ASLBs\u003c/h2\u003e\u003cp\u003eHalf-cells for ASLBs were designed and assembled with the type of 2032-coin cells. As for the design of the cell, lithium silicon-oxide composite materials (LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e/Graphite/Super-P/LLZO/PEO) were used as the WE, oxide-based materials (LLZO/PEO/Salt) were applied to the SE layer, and lithium metal was applied to the CE, respectively. Charging/discharging experiments were conducted at 70\u0026deg;C through an automatic battery cycler system (WBCS3000, Wonatech, Korea). Charging of the half-cell was performed in CC-CV mode with a current of 0.05-0.02C, and the discharging was carried out at 0.05C, with a cut-off at 1.5V.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the XRD peak patterns of the amorphous LiSiO\u003csub\u003ex\u003c/sub\u003e precursor heat-treated at 400\u0026deg;C in the synthesis process of Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, LiSiO\u003csub\u003e2\u003c/sub\u003e calcined at 700\u0026deg;C in a reducing atmosphere, and LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e after adding Si and calcining at 700\u0026deg;C and 950\u0026deg;C in a reducing atmosphere. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(a) shows the typical XRD peak pattern of amorphous LiSiOx, exhibiting a broad peak in the 15\u0026ndash;30\u0026deg; range, which corresponds to the characteristic pattern of amorphous LiSiO₂. In the case of the peak for the amorphous LiSiO\u003csub\u003ex\u003c/sub\u003e after heat treatment at 700\u0026deg;C in a reducing atmosphere in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(b), it can be observed that the peak of LiSiO\u003csub\u003e2\u003c/sub\u003e of Sample #1 appears as a distinct crystallization peak along with some impurities. Additionally, in the case of Sample #2, which was subjected to calcination under the same conditions with the addition of pure Si, the intensity of the LiSiO\u003csub\u003e2\u003c/sub\u003e peak was relatively weaker than that of Sample #1, and a new Si peak was clearly observed. Furthermore, in the case of Sample #3, where the calcination temperature was increased to 950\u0026deg;C, there was a tendency for the intensities of the main LiSiO\u003csub\u003e2\u003c/sub\u003e and Si peaks to decrease, which indicates changes in the crystal structure and particle morphology.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eTable II. Rietveld refinement of XRD analysis for crystalline LiSiO\u003c/b\u003e\u003csub\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sub\u003e \u003cb\u003epowder, and Si added to LiSiO\u003c/b\u003e\u003csub\u003e\u003cb\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/b\u003e\u003c/sub\u003e \u003cb\u003epowder with calcination temperature.\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabb\" border=\"1\"\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ea(\u0026Aring;)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eb(\u0026Aring;)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003ec(\u0026Aring;)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eCrystallite\u003c/p\u003e\u003cp\u003eSize (\u0026Aring;)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eCrystal structure\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample #1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e5.82956\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e14.6214\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4.78096\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e484\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eMonoclinic\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample #2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e5.82822\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e14.6184\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4.77956\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e740.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eMonoclinic\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample #3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e5.83843\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e14.6236\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4.78178\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e558.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eOrthorhombic\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eTable II shows the results of the rietveld analysis for Samples #1\u0026ndash;#3, including the lattice constants, lattice sizes, and crystal structures, based on the XRD peaks related to Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e of the synthesized materials. Compared to Sample #1, Sample #2, which was treated with Si addition at 700\u0026deg;C in a reducing atmosphere, shows a decrease in lattice constant. However, for Sample #3, where the reduction treatment temperature was increased to 950\u0026deg;C, the lattice constant increases again, and the crystallite size exhibits the largest value in Sample #2. In other words, Sample #1 and #2 exhibit a monoclinic structure, while Sample #3 shows an orthorhombic structure. This indicates that as the reduction temperature increases, the crystal structure changes.\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the SEM images of Sample #1, Sample #2 calcined at 700\u0026deg;C in a reducing atmosphere, and Sample #3 with Si addition, all produced according to the process in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Specifically, Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(a) and 3(b) present the SEM images of Sample #1 at 1,000\u0026times; and 10,000\u0026times; magnification, respectively; Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(c) and 3(d) correspond to Sample #2 under the same magnifications; and Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(e) and 3(f) show the 1,000\u0026times; and 10,000\u0026times; magnified images of Sample #3. In the case of Sample #1 with the amorphous LiSiO\u003csub\u003ex\u003c/sub\u003e, fine primary particles of about 1\u0026ndash;2 \u0026micro;m were observed. However, Sample #2 was heat-treated at 700\u0026deg;C, a phenomenon of aggregation into secondary particles of about 10 \u0026micro;m was observed. Additionally, Sample #3 was mixed with pure Si nanopowder, ball-milled, and then calcined. It was found to consist of finer primary particles compared to Sample #1.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows XPS spectra of Si2p, O1s and Li1p for amorphous LiSiO\u003csub\u003ex\u003c/sub\u003e calcined at 400 ℃, LiSiO\u003csub\u003e2\u003c/sub\u003e powder calcined at 700 ℃, and Si added to LiSiO\u003csub\u003e2\u003c/sub\u003e powder (LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e) calcined at 700 ℃ and atomic ratio of O1s/Si2p with Samples. The precursor, lithium-doped silicon oxide(LiSiO\u003csub\u003ex\u003c/sub\u003e), and LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e exhibits a different trend in its spectra compared to the conventional SiO\u003csub\u003ex\u003c/sub\u003e material [\u003cspan additionalcitationids=\"CR37\" citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(a) shows that only Si\u003csup\u003e3+\u003c/sup\u003e is detected at 102.5\u0026ndash;103 eV, which is different from the main phase of Si\u003csup\u003e4+\u003c/sup\u003e in the conventional SiO\u003csub\u003ex\u003c/sub\u003e. This indicates the presence of the LiSiO\u003csub\u003ex\u003c/sub\u003e phase, as shown in the XRD pattern. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(b) shows the O1s pattern, where all three binding energy peaks are observed in the 529\u0026ndash;534 eV range, with the main peaks at 532.2 eV and 531 eV, respectively. In this process, The peak at 531.2 eV is known to correspond to Si-O-Li bonding. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(c) shows the Li1s pattern with the main peak at 55 eV, which indicates unreacted impurities, such as typical lithium compounds like LiOH. This is consistent with the results from the XRD peak pattern. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(d) shows the atomic ratio of O1s/Si2p for each sample, indicating that Sample #2 has a higher oxygen deficiency compared to Sample #1. In other words, when pure Si nanoparticles were added, ball-milled, and then subjected to calcination during the synthesis process, the composition of the particles was confirmed to be Li\u003csub\u003e1.2\u003c/sub\u003eSi\u003csub\u003e1\u003c/sub\u003eO\u003csub\u003e1.86\u003c/sub\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e shows the initial charge-discharge curves of Sample #1, Sample #2, and Sample #3, respectively. From this, it can be seen that the discharge capacity varies depending on the addition of Si and the calcination temperature during synthesis of the materials. In the first cycle, discharge capacity, Sample #1, Sample #2, and Sample #3 shows 70, 460, 290 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively, indicating that Sample #2 has a relatively higher capacity compared to the other samples. Sample #1 not only shows a low initial capacity but also exhibits almost no change in capacity over cycling. Samples #2 and #3 exhibited significantly higher initial capacities due to Si addition, yet both showed rapid capacity fading during cycling. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(d), the increase in the initial capacity is not due to the behavior of LiSiO\u003csub\u003ex\u003c/sub\u003e, but rather attributed to the characteristics of pure Si in the composition of LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e. Furthermore, the higher initial capacity of Sample #2 compared to Sample #3 is presumed to be due to the lower calcination temperature, which likely resulted in a finer powder particle size in the anode. The reduced particle size is presumed to increase the reaction surface area, thereby enhancing lithium-ion accessibility and contributing to the higher initial capacity.\u003c/p\u003e\u003cp\u003eTherefore, based on the characteristics of Sample #2, additional experiments were conducted involving its mixture with graphite to further optimize the conditions of the anode active material as shown in the Table I.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e shows the initial capacity and cycling characteristics of Sample #4 and Sample #5, which are based on Si and include graphite as an additive, compared to the active material of Sample #2.\u003c/p\u003e\u003cp\u003eSpecifically, LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e and graphite were mixed in weight ratios of 2:8 for Sample #4 and 5:5 for Sample #5. Compared to the charge-discharge curve of Sample #2 based on LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e, the addition of graphite to LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e results in noticeable changes in the charge-discharge behavior. Specifically, as the graphite content increases, the irreversible capacity during charging decreases, and the discharge voltage plateau characteristic of graphite becomes more pronounced. As a result, the initial discharge capacity decreases with increasing graphite content, but the cycling capacity improves relatively.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(a\u0026ndash;c) presents the differential charge\u0026ndash;discharge curves (dQ/dV) for the first cycle of Samples #2, #4, and #5, corresponding to the charge\u0026ndash;discharge profiles shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(d) compares the 1st and 2nd cycles of Sample #4. That is, Sample #1 exhibits the typical oxidation (0.42 V) and reduction (0.15 V) peaks characteristic of LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e. In contrast, Sample #2 that contains 50 wt% graphite shows additional peaks corresponding to both Si and graphite. In this process, as the graphite content increases as in Sample #4 and Sample #5, the original Si-related peaks decrease. In particular, Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(d) presents the differential curves for the 1st and 2nd charge-discharge cycles of Sample #4, showing a significant difference between the two cycles. Specifically, most of the Si-related peaks disappear in the 2nd cycle, and the curve is dominated by graphite-related peaks. Furthermore, as the graphite content increases, the irreversible charge capacity in the first cycle decreases, and the capacity difference in the second cycle also shows a decreasing trend. These results confirm that when LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e is composited with graphite, and as the proportion of graphite increases, the charge\u0026ndash;discharge capacity improves significantly by more than twofold in some cases.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThis study investigated the structural and electrochemical characteristics of LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e-based composite anodes synthesized through sol-gel-derived precursors, with variations in calcination temperature and additive composition. XRD and Rietveld refinement results demonstrated that the initial amorphous LiSiO\u003csub\u003ex\u003c/sub\u003e transformed into a monoclinic LiSiO\u003csub\u003e2\u003c/sub\u003e phase after calcination at 700\u0026deg;C (Sample #1), and further evolved into an orthorhombic LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e structure at 950\u0026deg;C (Sample #3) when combined with Si nanopowders. XPS analysis confirmed the presence of oxygen-deficient Li\u003csub\u003e1.2\u003c/sub\u003eSi\u003csub\u003e1\u003c/sub\u003eO\u003csub\u003e1.86\u003c/sub\u003e composition and Si\u003csup\u003e3+\u003c/sup\u003e oxidation states, supporting the structural deviation from conventional SiO\u003csub\u003ex\u003c/sub\u003e systems.\u003c/p\u003e\u003cp\u003eElectrochemical evaluation revealed that Sample #2, synthesized by incorporating nano-sized Si and calcining at 700\u0026deg;C, achieved the highest initial discharge capacity of 460 mAh g⁻\u0026sup1;. However, this came at the expense of rapid capacity fading due to intrinsic Si instability. To address this, LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e was composited with graphite to form Sample #4 and Sample #5. These samples exhibited improved cycling performance, with Sample #5 (graphite-rich, 2:8 ratio) retaining over twice the capacity of Sample #2 after multiple cycles. Differential capacity analysis confirmed that graphite effectively buffered the volume expansion of Si and stabilized the electrochemical interface.\u003c/p\u003e\u003cp\u003eOverall, this work provides a promising direction for the design of high-capacity and stable anode materials by tailoring oxygen-deficient LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e and optimizing composite ratios with graphite. The combination of controlled structural transformation, oxygen deficiency, and carbon compositing enables enhanced electrochemical performance, making the developed LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e/graphite composites suitable for future ASLB applications. Further work will focus on interface engineering and long-term durability testing to advance the practical viability of these composite anodes.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eS.J.P. performed the synthesis of LiSiO₂₋ₓ materials, carried out electrochemical measurements, and drafted the initial manuscript.M.-Y.K. contributed to the preparation of solid electrolyte composites and assisted in electrochemical testing.Y.W.S. carried out structural characterization including XRD and XPS analysis and contributed to data interpretation.H.-B.K. assisted in material preparation, SEM measurements, and analysis of particle morphology.W.J.K. supported data curation, figure preparation, and validation of experimental results.B.-S.K. supervised the project design, provided critical revisions to the manuscript, and guided the discussion on materials chemistry.H.-S.K. conceived the overall research idea, coordinated the project, and finalized the manuscript.All authors reviewed and approved the final version of the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThis work was supported by the Korea Ministry of Trade, Industry, and Energy (MOTIE) through \u0026ldquo;Development of Power Components and System Control Technology for the Transition to New Power Architecture (48V)\u0026rdquo; under Grant RS-2024-00409108.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eY.-K. 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Soc.\u003c/em\u003e, 106, 4554\u0026ndash;4566 (2023)\u003c/span\u003e\u003c/li\u003e\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":"All-solid-state lithium-ion batteries, Oxygen-deficient crystalline, Lithium silicon oxide, Garnet oxide electrolyte, Composite solid electrolyte, Lithium-metal","lastPublishedDoi":"10.21203/rs.3.rs-7653372/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7653372/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eOxygen-deficient crystalline LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e materials for the anode of all-solid-state lithium batteries (ASLBs) were prepared using a sol-gel and reduction process. The resulting powder had a composition of Li\u003csub\u003e1.2\u003c/sub\u003eSi\u003csub\u003e1\u003c/sub\u003eO\u003csub\u003e1.86\u003c/sub\u003e, with a particle size of approximately 20 \u0026micro;m and good crystallinity. The change in oxygen content on the particle surface was examined by X-ray photoelectron spectroscopy, indicating that oxygen deficiency was optimized when heat-treated at 700\u0026deg;C after silicon addition. The powder was then mixed with graphite (Gr), Li\u003csub\u003e6.25\u003c/sub\u003eAl\u003csub\u003e0.25\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003eZr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e12\u003c/sub\u003e (LLZO), polyethylene oxide (PEO), and Super-P in specific ratios to form a composite anode. To investigate the effect of silicon oxide on the anode, the LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e:graphite ratio was varied across three compositions (10:0, 5:5, and 2:8). ASLBs were fabricated using a half-cell configuration with 2032-coin cells, consisting of a working electrode made of LiSiO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e composite anode, a solid electrolyte composed of LLZO-PEO composite film, and a lithium metal counter electrode. No liquid electrolyte was used, and LiClO\u003csub\u003e4\u003c/sub\u003e salt was incorporated into both the anode and electrolyte. Electrochemical testing revealed that the cell with a Si:Gr ratio of 2:8 exhibited an initial capacity of 360 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, confirming reduced irreversible capacity loss during cycling.\u003c/p\u003e","manuscriptTitle":"Synthesis and Electrochemical Properties of Oxygen-deficient Crystalline Lithium Silicon Oxide for the Anode of All-Solid-state Lithium-Ion Batteries","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-27 11:42:17","doi":"10.21203/rs.3.rs-7653372/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-11-03T14:49:22+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-31T12:22:03+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-25T20:47:11+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"138116213468505276213332612470344315241","date":"2025-10-14T20:48:28+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"42037803108045543154648625777400751551","date":"2025-10-14T10:22:09+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-10-13T17:24:45+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-09-24T06:12:34+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-09-24T06:09:42+00:00","index":"","fulltext":""},{"type":"submitted","content":"Ionics","date":"2025-09-19T01:14:13+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":"072d8f67-aece-4f10-965d-86f03986a858","owner":[],"postedDate":"October 27th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-02-19T20:38:58+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-27 11:42:17","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7653372","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7653372","identity":"rs-7653372","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}