Yolk-shell structure Fe2O3@C nanocomposite anode material prepared from the leaching solution of iron concentrate for lithium-ion batteries

Yolk-shell structure Fe2O3@C nanocomposite anode material prepared from the leaching solution of iron concentrate for 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 Yolk-shell structure Fe 2 O 3 @C nanocomposite anode material prepared from the leaching solution of iron concentrate for lithium-ion batteries Guimin Zhou, Yin Li, Li Wang, Yaochun Yao, Shaoze Zhang, Keyu Zhang, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7737011/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 18 You are reading this latest preprint version Abstract Yolk-shell structure Fe 2 O 3 @C composite by utilizing the iron concentrate leachate with a selective chemical precipitation method and illustrate its great potential as a high-performance anode material of lithium-ion batteries (LIBs). The Fe 2 O 3 @C composite exhibits superior cyclic performance (723.08 mA h g − 1 over 300 cycles at 1 A g − 1 ) and high-rate capability (322.01 mA h g − 1 even at a high current density of 5 A g − 1 ) in a half cell. The excellent performance of the Fe 2 O 3 @C can be attributed to particles contain abundant internal voids, which facilitates the infiltration of the electrolyte and alleviates the volume change of electrode material, thereby enhancing the electrochemical performance of the material. Due to the unique yolk-shell structure nanostructure, Fe 2 O 3 @C composite shows significant pseudocapacitive behavior during discharge/charge processes, which partially accounts for the excellent lithium-ion storage performance. Fe2O3@C composite Iron concentrate leachate ZIF-8 Lithium-ion battery Anode material Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction With the continuous growth of global energy demand and increasingly prominent environmental issues, the development of efficient, clean and sustainable energy storage technologies has become a crucial direction in contemporary scientific research and industrial applications. Lithium-ion batteries (LIBs), owing to their high energy density, long cycle life and environmental friendliness, have dominated applications in electric vehicles, portable electronic devices, and smart grid systems [ 1 – 5 ]. However, the conventional graphite anode material exhibits a relatively low theoretical specific capacity (372 mAh g − 1 ), making it difficult to meet the requirements for high-energy-density storage [ 6 ]. Consequently, the development of novel high-performance anode materials has emerged as one of the current research priorities. Among various candidate anode materials, transition metal oxides (TMOs), particularly iron oxides (Fe x Oy, including Fe₂O₃ and Fe₃O₄), have been recognized as one of the most promising anode materials for LIBs due to their superior theoretical capacity (~ 1000 mAh g − 1 ), abundant natural resources, low cost and environmental compatibility [ 7 , 8 ]. However, iron oxide materials still suffer from several critical challenges in practical applications. For example, poor electrical conductivity, volume expansion and side reaction issues [ 9 – 10 ]. To address these problems, researchers have proposed various modification strategies, including nanostructure design, carbon coating, conductive polymer compositing, and elemental doping [ 11 , 12 ]. Among these methods, carbon coating has emerged as an effective methodology that simultaneously enhances electrical conductivity and mitigates volume expansion, thereby improving cycling stability. Metal-organic frameworks (MOFs) have been identified as ideal carbon precursors due to their high specific surface area, tunable pore structures and ability to form conductive carbon networks upon pyrolysis. Particularly, zeolitic imidazolate framework-8 (ZIF-8), which can be converted into porous carbon (PC) through thermal treatment, has been extensively employed in the fabrication of high-performance electrode materials owing to its exceptional electrical conductivity and chemical stability [ 13 , 14 ]. Simultaneously, the efficient utilization of resources and sustainable development have emerged as global priorities. Iron concentrate, serving as the primary raw material for steel smelting, generates leachates rich in Fe²⁺/Fe³⁺ ions during hydrometallurgical processing. Conventional treatment methods typically employ neutralization precipitation to recover iron residues, yet this approach demonstrates limited economic value-added potential and may potentially induce secondary pollution. The direct conversion of these leachates into high-value electrodes materials would not only facilitate resource recycling but also significantly reduce the production costs of electrode materials, thereby aligning with the fundamental principles of green chemistry and circular economy development. Hence, iron concentrate leachate was used as the iron source to prepare Fe 2 O 3 . Subsequently, the core-shell Fe 2 O 3 @C anode was prepared via a facile method with ZIF-8 as carbon sources. Benefitting from the hollow framework and carbon layer, the material illustrated excellent electrochemical performance. The initial discharge/charge capacity of the as-prepared Fe 2 O 3 @C electrode can reach 723.08 mAh g − 1 at a current density of 1 A g − 1 . 2. Experimental section 2.1. Raw materials All the reagents (NH 3 ·H 2 O, Co(NO 3 ) 2 ·6H 2 O, PVP, Zn(NO 3 ) 2 and 2-methylimidazole) are all of analytically grade. The leachate of iron concentrate in this study was provided from a company situated in Yunnan, China. The main components of the leachate are shown in Table 1 . Table 1 The main components of the leachate Solutions Constituents and content Al Co Cr Mn Ti K Na Ca Mg Fe After leaching (g/L) 0.007 0.42 0.5 0.38 0.03 0.001 0.004 0.007 0.002 53.367 2.2. Preparation of Fe 2 O 3 and Fe 2 O 3 @C Fe 2 O 3 was prepared at room temperature through a simple chemical precipitation method with iron concentrate leachate as the iron source and ammonia as the precipitant. A mixture of 0.5 g of Fe 2 O 3 and 0.5 g of PVP was stirred in 100 mL methanol solution for 30 minutes. A certain mass of 2-methylimidazole was weighed and dissolved in methanol under ultrasonic treatment for 30 minutes until complete dissolution, which was denoted as Solution A. The pre-prepared Fe 2 O 3 , polyvinylpyrrolidone (PVP) and Zn(NO 3 ) 2 were added to 90 mL of methanol under continuous stirring until fully dissolved. Solution A was then introduced into the mixture and allowed to stand for 6 hours to ensure complete coating of ZIF-8 onto Fe₂O₃. The product was washed with methanol, dried, and collected as the Fe₂O₃/ZIF-8 composite. The obtained composite was subsequently carbonized at 400°C for 2 hours under an argon atmosphere to yield the Fe₂O₃@C composite material. 2.3. Material characterization The phase structure of the as-prepared samples was characterized by an X-ray diffractometer (XRD, Austrian Anton Paar XRDynamic500). The morphology of the samples was examined using SEM (German ZEISS Fegma 300) and TEM (US FEI Talos F200x). X-ray photoelectron spectroscopy (XPS) was conducted using a Thermo Scientific K-Alpha analyzer to analyze the surface chemical composition and valence states. Nitrogen adsorption-desorption isotherms were measured using a US Micromeritics ASAP 2460 analyzer to determine the specific surface area of the samples. 2.4. Electrochemical measurements The electrochemical performance of Fe 2 O 3 and Fe 2 O 3 @C were employed using CR2025 coin-type cells and tested at 25°C within a voltage range of 0.01-3 V (vs. Li + /Li) under varying current densities. CR2025 coin cells were assembled within an argon-filled glovebox. And 1 M LiPF 6 dissolved in a 1:1:1 volumetric mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) was used as the electrolyte.Fe 2 O 3 or Fe 2 O 3 @N-C, PVDF, and Super P were mixed in a 7:2:1 mass ratio and dissolved in N-methyl-2-pyrrolidone (NMP) to form a uniform slurry. Subsequently, the slurry was applied to copper foil and vacuum-dried at 80°C for 12 h. Additionally, the electrodes were cut into 14 mm diameter disks with an active material loading of 40.00 ± 0.05 mg/cm 2 . And this electrode is used as the anode. Cyclic voltammetry (CV) analyses were performed using an electrochemical workstation (Chi 760 E, China) within a potential range of 0.01-3 V (vs. Li + /Li) at scan rates of 0.1-1 mV s⁻¹. Electrochemical impedance spectroscopy (EIS) measurements were performed across a frequency range of 10 mHz to 100 kHz. 3. Result and discussion The structure and composition of Fe 2 O 3 and Fe 2 O 3 @C materials were carried out by XRD. As displayed in Fig. 1 a. All synthesized samples exhibit no additional diffraction peaks compared to the reference pattern (PDF#33–0664), indicating the absence of impurity phases [ 15 ]. Furthermore, no detectable diffraction peaks corresponding to carbon were observed in sample Fe 2 O 3 @C, which is primarily due to the amorphous nature of carbon. To directly examine the microstructural morphology of the material, scanning electron microscopy (SEM) analysis was conducted. As shown in Figs. 1 b and c, Fe 2 O 3 consists of rod-shaped particles with lengths ranging from 50 to 200 nm, which are randomly arranged and aggregated. However, Fe 2 O 3 @C is composed of numerous more uniform nanorods, with dimensions around 200 nm, as shown in Fig. 1 d. Notably, a comparison between Figs. 1 e and f reveals that Fe 2 O 3 @C exhibits larger interparticle voids. These voids can accommodate volume expansion during the lithiation and delithiation processes, thereby mitigating excessive electrode swelling and contributing significantly to the stability of electrochemical performance. The TEM micrographs of Fe 2 O 3 and Fe 2 O 3 @C are presented in Fig. 2 . As can be observed from both Figs. 2 a and c, materials Fe 2 O 3 and Fe 2 O 3 @C consist of nanosheet-like particles, which is consistent with the results obtained from the SEM images. A comparison between Fig. 2 b and d reveals that Fe 2 O 3 @C is coated with a uniform carbon layer, which is attributed to the high-temperature pyrolysis of ZIF-8. The thickness of this carbon layer is 5 mm, which significantly enhances the electrical conductivity of Fe 2 O 3 @C, thereby proving beneficial for its electrochemical performance. As shown in Figs. 2 e-j, the distribution of Fe, O, N, Zn and C elements can be clearly observed, indicating that ZIF-8 is uniformly distributed on the surface of Fe 2 O 3 @C after high-temperature pyrolysis. To investigate the specific surface area and pore structure characteristics of the composite material, we conducted N₂ adsorption tests, and the results are shown in Fig. 3 . The specific surface area of the Fe₂O₃@C composite is determined to be 2.8153 m² g − 1 and the pore size is 1.84 nm. Due to the porous nature of ZIF-8, a large number of open pores were formed in the carbon layer after high-temperature treatment. As a result, Fe 2 O 3 @C particles contain abundant internal voids, which facilitates the infiltration of the electrolyte and alleviates the volume change of electrode material, thereby enhancing the electrochemical performance of the material [ 16 , 17 ]. The surface composition and bonding states of the Fe₂O₃@C material were determined by X-ray photoelectron spectroscopy (XPS). Figure 4 a displays the XPS survey spectrum of Fe₂O₃@C, which confirms the presence of Fe, C, N, Zn and O elements in the sample. The high-resolution spectrum of Fe 2p is shown in Fig. 4 b. Two main characteristic peaks are observed at binding energies of 724.1 and 711.0 eV, corresponding to Fe 2p₁/₂ and Fe 2p₃/₂ of Fe³⁺ in Fe₂O₃, respectively [ 18 ]. The high-resolution O 1s spectrum (Fig. 4 c) is deconvoluted into two component peaks. The peaks located at 530.1 and 531.1 eV are attributed to Fe–O and C–O bonds, respectively, indicating that Fe is covalently bonded to O. The high-resolution C 1s spectrum (Fig. 4 d) exhibits three peaks at 284.6 eV, 285.6 eV, and 288.3 eV. The peak at 284.6 eV is assigned to C–C bonds in the carbon layer coated on the surface of Fe₂O₃ nanoparticles. The peak at 285.6 eV is associated with C–O bonds. The peak at 287.8 eV is assigned to C–N bonds and the peak at 288.3 eV corresponds to C = O bonds [ 19 , 20 ]. Figure 5 a shows the cycling performance of materials Fe 2 O 3 and Fe 2 O 3 @C over 300 charge-discharge cycles at a current density of 0.1 A g − 1 . As can be seen from Fig. 5 a, after 300 cycles, the reversible capacity of Fe 2 O 3 @C decreased from 1168.65 to 723.08 mAh/g, while that of Fe 2 O 3 plummeted from 1204.12 to 205.37 mAh g − 1 . The capacity retention rate of Fe 2 O 3 @C was 61.87%, whereas that of Fe 2 O 3 @C was only 17.06%. These results indicate that Fe 2 O 3 @C exhibits superior reversibility and cycling stability. The rate performance of materials under varying current densities is presented in Fig. 5 b. As clearly observed from the figure, Fe 2 O 3 @C demonstrates superior rate performance compared to Fe 2 O 3 . When the current density increases to 5 A g⁻¹, Fe 2 O 3 exhibits poor reversible capacity, merely reaching 3.47 mAh g⁻¹. In contrast, under the same current density, Fe 2 O 3 @C maintains a capacity of 322.01 mAh g⁻¹. This enhancement can be attributed to the uniform coating derived from the high-temperature pyrolysis of ZIF-8 on the surface of Fe 2 O 3 @C, which results in a higher specific surface area, provides additional defects and porosity, and facilitates faster electron and ion transport during charge-discharge processes. Figures 5 c and d present the distinct discharge/charge voltage profiles of electrodes Fe 2 O 3 and Fe 2 O 3 @C under various current densities. As observed, these profiles exhibit similar variation trends, each comprising a rapid decline region (3-0.85 V), a plateau region (0.85 V), and a sloping region (0.75 − 0.01 V). In Fig. 5 c, as the cycle number increases from 1st to 300th, noticeable attenuation occurs in both the plateau and sloping regions. This indicates that electrode Fe 2 O 3 fails to adequately sustain the conversion reaction and surface interfacial processes at elevated current densities. In contrast, electrode Fe 2 O 3 @C maintains a high and stable capacity, with nearly identical plateau regions across different cycle number and a reversible capacity in the sloping region still exceeding 600 mAh g⁻¹, demonstrating its superior interfacial lithium-ion storage capability. To further investigate the kinetic differences between Fe 2 O 3 and Fe 2 O 3 @C during the charging and discharging processes, electrochemical impedance spectroscopy (EIS) was conducted over a frequency range of 0.1 Hz to 100 kHz. The results are presented in Fig. 6 . The Nyquist plots of both electrodes exhibit a similar pattern, consisting of a depressed semicircle in the medium-to-high frequency region and a sloped line in the low-frequency region. The semicircle corresponds to the charge transfer resistance and contact impedance, while the sloped line is associated with ion diffusion between the electrolyte and the electrode surface [ 21 , 22 ]. Notably, the diameter of the depressed semicircle for Fe 2 O 3 @C is significantly smaller than that of Fe 2 O 3 , indicating lower contact and charge transfer resistances. These results suggest that the carbon layer formed on the surface of Fe 2 O 3 after the high-temperature pyrolysis of introduced ZIF-8 can enhance the electrical conductivity and electrochemical activity of the electrode material, which is crucial for electron transfer and performance during lithium-ion cycling. We investigated the electrochemical kinetics of Fe 2 O 3 and Fe 2 O 3 @C by employing cyclic voltammetry (CV) at different scan rates. The results are presented in Figs. 7 a and e. It can be observed that both the oxidation and reduction peaks progressively shift as the scan rate increases. To qualitatively analyze this behavior, the relationship between the current and the scan rate was derived from the CV curves obtained at various scan rates, as described by Equations (1) and (2) below [ 23 ]. i = a v b (1) log( i ) = b log( v ) + log(a) (2) Where, i and v represent the peak current and scan rate, respectively, and a is a constant. The value of b was determined by plotting the fitted line of log( i ) versus log( v ) and calculating its slope. If b value close to 0.5 suggests a process that is primarily diffusion-controlled, while a value approaching 1.0 indicates capacitive behavior [ 24 ]. As illustrated in Figs. 7 b and d, the b-values were determined through curve fitting. The calculated b-values for Fe 2 O 3 and Fe 2 O 3 @C are 0.454 and 0.7866, respectively. These results indicate that the Li⁺ storage process in Fe 2 O 3 is primarily controlled by diffusion behavior, whereas in Fe 2 O 3 @C it is dominated by capacitive behavior. The specific percentage of the pseudocapacitive contribution can be quantified using Eq. (3) [ 25 , 26 ]. i ( V ) = k 1 v + k 2 v 1/2 (3) To elucidate the specific contributions of the electrodes at fixed scan rates, the respective contributions of pseudocapacitive ( k ₁ v ) and diffusion-controlled ( k ₂ v ¹ᐟ²) processes to the total current at a fixed potential ( v ) were deconvoluted. The values of k ₁ and k ₂ can be readily determined by fitting the plot of i ( v )/ v ¹ᐟ² versus v ¹ᐟ² [ 27 , 28 ]. As observed in the CV curves presented in Figs. 7 c and g, at a scan rate of 1 mV s⁻¹, approximately 60.10% and 89.17% of the total capacity for Fe 2 O 3 and Fe 2 O 3 @C, respectively, are attributed to capacitive contributions. Furthermore, the proportion of capacitive contribution increases correspondingly with increasing scan rate (Figs. 7 d and h). The bar charts clearly illustrate that for Fe 2 O 3 , the pseudocapacitive contribution rates at scan rates of 0.2, 0.4, 0.6, 0.8, and 1.0 mV s⁻¹ are 22.87%, 31.16%, 38.59%, 46.48%and 60.10%, respectively, while those for material Fe 2 O 3 @C is 65.17%, 72.48%, 81.18%, 85.86%and 89.17%. These results indicate that at high current densities, the capacity of the electrode materials is predominantly governed by surface-driven pseudocapacitive behavior. 4. Conclusion In conclusion, we have successfully synthesized the Fe 2 O 3 @C nanoparticles through a simple chemical precipitation process, employing iron concentrate leachate as the source of iron. The use of ZIF-8 of Fe 2 O 3 @C sample improved the electrical conductivity and lithium-ion diffusion kinetics by providing porous structures, resulting in improved electrochemical performance. The reversible capacity of Fe 2 O 3 @C decreased from 1168.65 to 723.08 mAh g − 1 after 100 cycles. The capacity still exhibited as high as 322.01 mA h g − 1 even at a high rate of 5 A g − 1 . This work can provide useful guidance for the development of preparation of electrode materials from solid waste. Declarations Author Contribution Guimin Zhou and Yin Li worte the main manuscript text. Li Wang, Yaochun Yao and Shaoze Zhang prepared figures 1-3. Keyu Zhang, Junxian Hu, Zhunqin Dong and Lingling Yuan prepared figures 4-7. All authors reviewed the manuscript Acknowledgements This work is financial supported by National Natural Science Foundation of China (Grant No. 52567025), Yunnan Fundamental Research Projects (Grant NO. 202301BE070001-065, 202301AU070055, 202402AF080003 and 202401AS070069). Declaration of competing interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. References G. Zubi, R. Dufo-Lopez, M. Carvalho, G. 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14:45:53","extension":"html","order_by":20,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":89711,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7737011/v1/bfba311b8cf69a9cf5cfc9dc.html"},{"id":94457324,"identity":"a7832bd6-80df-4a16-bfcf-471099dec83f","added_by":"auto","created_at":"2025-10-27 14:45:43","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":471877,"visible":true,"origin":"","legend":"\u003cp\u003eXRD spectra (a) and SEM images of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C (b-e)\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-7737011/v1/f982a5b890e97238c70559ba.png"},{"id":94457369,"identity":"89c209d3-c1a3-4655-a975-a0406438a0fd","added_by":"auto","created_at":"2025-10-27 14:45:49","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1179627,"visible":true,"origin":"","legend":"\u003cp\u003eTEM images of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e at various magnifications (a-c); TEM images of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@N-C at various magnifications (d-f); Elemental mapping images of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@N-C (g-j).\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-7737011/v1/2bd8ff4973682c06ea9144cc.png"},{"id":94457405,"identity":"5fa15386-81ac-4767-b16c-1306f70fda1e","added_by":"auto","created_at":"2025-10-27 14:45:50","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":49236,"visible":true,"origin":"","legend":"\u003cp\u003eThe N\u003csub\u003e2\u003c/sub\u003e adsorption/desorption isotherms (a); Alongside the pore size distribution charts (b) for Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-7737011/v1/7cbe58b9b65f7221a5e78f44.png"},{"id":94457680,"identity":"d94368a3-79f8-4202-8d9a-b37cb83651e1","added_by":"auto","created_at":"2025-10-27 14:46:15","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":55680,"visible":true,"origin":"","legend":"\u003cp\u003e(a) XPS survey spectrum and core-level XPS spectra of (b) Fe 2p (c) O 1s and (d) C 1s for the as-prepared Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C sample.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-7737011/v1/e3b94b03ab7e2e27865e0911.png"},{"id":94457270,"identity":"cb59d19a-9036-430a-b84d-5f51467b690e","added_by":"auto","created_at":"2025-10-27 14:45:37","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":102546,"visible":true,"origin":"","legend":"\u003cp\u003eCycle stabilities (a) and rate capabilities (b) of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C at 0.1 A/g; Galvanostatic charge/discharge profiles of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (c) and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C (d) in the different cycles at a current density of 0.1 A g\u003csup\u003e−1\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-7737011/v1/97edb6e79b4698924ad995f7.png"},{"id":94457566,"identity":"01c4a274-2d66-4eb5-97f9-073808283643","added_by":"auto","created_at":"2025-10-27 14:46:01","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":55745,"visible":true,"origin":"","legend":"\u003cp\u003eThe Nyquist diagrams (a) and the straight-line correlation between Z' and ω⁻¹/² (b) for Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C.\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-7737011/v1/332762bae4e7471a30163fe8.png"},{"id":94457579,"identity":"8cdab6d2-12bc-4520-b147-4dd82ed4f054","added_by":"auto","created_at":"2025-10-27 14:46:02","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":215792,"visible":true,"origin":"","legend":"\u003cp\u003eCV curves of the three samples at various scan rates (a, e); Linear relationship between the log (peak current) and log(scan rate) of the two samples (b,f); The percentage contribution of the pseudo-capacitor pseudocapacitive (1.0 mV s\u003csup\u003e-1\u003c/sup\u003e) (c, g); contribution ratio to the total capacity of the three samples at different scan rates (d, h).\u003c/p\u003e","description":"","filename":"image7.png","url":"https://assets-eu.researchsquare.com/files/rs-7737011/v1/4d7f7fabb5db8b5e01a07d6e.png"},{"id":94469060,"identity":"d69fa5ce-6389-4159-9233-4bab23f3e3d0","added_by":"auto","created_at":"2025-10-27 15:26:38","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2593691,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7737011/v1/82b6401c-b93f-4cb4-a8a7-f495ee91db95.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eYolk-shell structure Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C nanocomposite anode material prepared from the leaching solution of iron concentrate for lithium-ion batteries\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eWith the continuous growth of global energy demand and increasingly prominent environmental issues, the development of efficient, clean and sustainable energy storage technologies has become a crucial direction in contemporary scientific research and industrial applications. Lithium-ion batteries (LIBs), owing to their high energy density, long cycle life and environmental friendliness, have dominated applications in electric vehicles, portable electronic devices, and smart grid systems [\u003cspan additionalcitationids=\"CR2 CR3 CR4\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. However, the conventional graphite anode material exhibits a relatively low theoretical specific capacity (372 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), making it difficult to meet the requirements for high-energy-density storage [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Consequently, the development of novel high-performance anode materials has emerged as one of the current research priorities. Among various candidate anode materials, transition metal oxides (TMOs), particularly iron oxides (Fe\u003csub\u003ex\u003c/sub\u003eOy, including Fe₂O₃ and Fe₃O₄), have been recognized as one of the most promising anode materials for LIBs due to their superior theoretical capacity (~\u0026thinsp;1000 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), abundant natural resources, low cost and environmental compatibility [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. However, iron oxide materials still suffer from several critical challenges in practical applications. For example, poor electrical conductivity, volume expansion and side reaction issues [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. To address these problems, researchers have proposed various modification strategies, including nanostructure design, carbon coating, conductive polymer compositing, and elemental doping [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Among these methods, carbon coating has emerged as an effective methodology that simultaneously enhances electrical conductivity and mitigates volume expansion, thereby improving cycling stability. Metal-organic frameworks (MOFs) have been identified as ideal carbon precursors due to their high specific surface area, tunable pore structures and ability to form conductive carbon networks upon pyrolysis. Particularly, zeolitic imidazolate framework-8 (ZIF-8), which can be converted into porous carbon (PC) through thermal treatment, has been extensively employed in the fabrication of high-performance electrode materials owing to its exceptional electrical conductivity and chemical stability [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eSimultaneously, the efficient utilization of resources and sustainable development have emerged as global priorities. Iron concentrate, serving as the primary raw material for steel smelting, generates leachates rich in Fe\u0026sup2;⁺/Fe\u0026sup3;⁺ ions during hydrometallurgical processing. Conventional treatment methods typically employ neutralization precipitation to recover iron residues, yet this approach demonstrates limited economic value-added potential and may potentially induce secondary pollution. The direct conversion of these leachates into high-value electrodes materials would not only facilitate resource recycling but also significantly reduce the production costs of electrode materials, thereby aligning with the fundamental principles of green chemistry and circular economy development.\u003c/p\u003e\u003cp\u003eHence, iron concentrate leachate was used as the iron source to prepare Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e. Subsequently, the core-shell Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C anode was prepared via a facile method with ZIF-8 as carbon sources. Benefitting from the hollow framework and carbon layer, the material illustrated excellent electrochemical performance. The initial discharge/charge capacity of the as-prepared Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C electrode can reach 723.08 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at a current density of 1 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.\u003c/p\u003e"},{"header":"2. Experimental section","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Raw materials\u003c/h2\u003e\u003cp\u003eAll the reagents (NH\u003csub\u003e3\u003c/sub\u003e\u0026middot;H\u003csub\u003e2\u003c/sub\u003eO, Co(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO, PVP, Zn(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and 2-methylimidazole) are all of analytically grade. The leachate of iron concentrate in this study was provided from a company situated in Yunnan, China. The main components of the leachate are shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eThe main components of the leachate\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"11\"\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\u003cdiv align=\"left\" 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\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eSolutions\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"10\" nameend=\"c11\" namest=\"c2\"\u003e\u003cp\u003eConstituents and content\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAl\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eCo\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eCr\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eMn\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eTi\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eK\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNa\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e\u003cp\u003eCa\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c10\"\u003e\u003cp\u003eMg\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c11\"\u003e\u003cp\u003eFe\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAfter leaching (g/L)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.007\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.38\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e0.004\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e0.007\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e53.367\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Preparation of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C\u003c/h2\u003e\u003cp\u003eFe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e was prepared at room temperature through a simple chemical precipitation method with iron concentrate leachate as the iron source and ammonia as the precipitant. A mixture of 0.5 g of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and 0.5 g of PVP was stirred in 100 mL methanol solution for 30 minutes. A certain mass of 2-methylimidazole was weighed and dissolved in methanol under ultrasonic treatment for 30 minutes until complete dissolution, which was denoted as Solution A. The pre-prepared Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, polyvinylpyrrolidone (PVP) and Zn(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e were added to 90 mL of methanol under continuous stirring until fully dissolved. Solution A was then introduced into the mixture and allowed to stand for 6 hours to ensure complete coating of ZIF-8 onto Fe₂O₃. The product was washed with methanol, dried, and collected as the Fe₂O₃/ZIF-8 composite. The obtained composite was subsequently carbonized at 400\u0026deg;C for 2 hours under an argon atmosphere to yield the Fe₂O₃@C composite material.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Material characterization\u003c/h2\u003e\u003cp\u003eThe phase structure of the as-prepared samples was characterized by an X-ray diffractometer (XRD, Austrian Anton Paar XRDynamic500). The morphology of the samples was examined using SEM (German ZEISS Fegma 300) and TEM (US FEI Talos F200x). X-ray photoelectron spectroscopy (XPS) was conducted using a Thermo Scientific K-Alpha analyzer to analyze the surface chemical composition and valence states. Nitrogen adsorption-desorption isotherms were measured using a US Micromeritics ASAP 2460 analyzer to determine the specific surface area of the samples.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Electrochemical measurements\u003c/h2\u003e\u003cp\u003eThe electrochemical performance of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C were employed using CR2025 coin-type cells and tested at 25\u0026deg;C within a voltage range of 0.01-3 V (vs. Li\u003csup\u003e+\u003c/sup\u003e/Li) under varying current densities. CR2025 coin cells were assembled within an argon-filled glovebox. And 1 M LiPF\u003csub\u003e6\u003c/sub\u003e dissolved in a 1:1:1 volumetric mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) was used as the electrolyte.Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e or Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@N-C, PVDF, and Super P were mixed in a 7:2:1 mass ratio and dissolved in N-methyl-2-pyrrolidone (NMP) to form a uniform slurry. Subsequently, the slurry was applied to copper foil and vacuum-dried at 80\u0026deg;C for 12 h. Additionally, the electrodes were cut into 14 mm diameter disks with an active material loading of 40.00\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05 mg/cm\u003csup\u003e2\u003c/sup\u003e. And this electrode is used as the anode. Cyclic voltammetry (CV) analyses were performed using an electrochemical workstation (Chi 760 E, China) within a potential range of 0.01-3 V (vs. Li\u003csup\u003e+\u003c/sup\u003e/Li) at scan rates of 0.1-1 mV s⁻\u0026sup1;. Electrochemical impedance spectroscopy (EIS) measurements were performed across a frequency range of 10 mHz to 100 kHz.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Result and discussion","content":"\u003cp\u003eThe structure and composition of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C materials were carried out by XRD. As displayed in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea. All synthesized samples exhibit no additional diffraction peaks compared to the reference pattern (PDF#33\u0026ndash;0664), indicating the absence of impurity phases [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Furthermore, no detectable diffraction peaks corresponding to carbon were observed in sample Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C, which is primarily due to the amorphous nature of carbon. To directly examine the microstructural morphology of the material, scanning electron microscopy (SEM) analysis was conducted. As shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb and c, Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e consists of rod-shaped particles with lengths ranging from 50 to 200 nm, which are randomly arranged and aggregated. However, Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C is composed of numerous more uniform nanorods, with dimensions around 200 nm, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed. Notably, a comparison between Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ee and f reveals that Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C exhibits larger interparticle voids. These voids can accommodate volume expansion during the lithiation and delithiation processes, thereby mitigating excessive electrode swelling and contributing significantly to the stability of electrochemical performance.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe TEM micrographs of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. As can be observed from both Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea and c, materials Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C consist of nanosheet-like particles, which is consistent with the results obtained from the SEM images. A comparison between Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb and d reveals that Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C is coated with a uniform carbon layer, which is attributed to the high-temperature pyrolysis of ZIF-8. The thickness of this carbon layer is 5 mm, which significantly enhances the electrical conductivity of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C, thereby proving beneficial for its electrochemical performance. As shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee-j, the distribution of Fe, O, N, Zn and C elements can be clearly observed, indicating that ZIF-8 is uniformly distributed on the surface of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C after high-temperature pyrolysis.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTo investigate the specific surface area and pore structure characteristics of the composite material, we conducted N₂ adsorption tests, and the results are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The specific surface area of the Fe₂O₃@C composite is determined to be 2.8153 m\u0026sup2; g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and the pore size is 1.84 nm. Due to the porous nature of ZIF-8, a large number of open pores were formed in the carbon layer after high-temperature treatment. As a result, Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C particles contain abundant internal voids, which facilitates the infiltration of the electrolyte and alleviates the volume change of electrode material, thereby enhancing the electrochemical performance of the material [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe surface composition and bonding states of the Fe₂O₃@C material were determined by X-ray photoelectron spectroscopy (XPS). Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea displays the XPS survey spectrum of Fe₂O₃@C, which confirms the presence of Fe, C, N, Zn and O elements in the sample. The high-resolution spectrum of Fe 2p is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb. Two main characteristic peaks are observed at binding energies of 724.1 and 711.0 eV, corresponding to Fe 2p₁/₂ and Fe 2p₃/₂ of Fe\u0026sup3;⁺ in Fe₂O₃, respectively [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. The high-resolution O 1s spectrum (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec) is deconvoluted into two component peaks. The peaks located at 530.1 and 531.1 eV are attributed to Fe\u0026ndash;O and C\u0026ndash;O bonds, respectively, indicating that Fe is covalently bonded to O. The high-resolution C 1s spectrum (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed) exhibits three peaks at 284.6 eV, 285.6 eV, and 288.3 eV. The peak at 284.6 eV is assigned to C\u0026ndash;C bonds in the carbon layer coated on the surface of Fe₂O₃ nanoparticles. The peak at 285.6 eV is associated with C\u0026ndash;O bonds. The peak at 287.8 eV is assigned to C\u0026ndash;N bonds and the peak at 288.3 eV corresponds to C\u0026thinsp;=\u0026thinsp;O bonds [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea shows the cycling performance of materials Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C over 300 charge-discharge cycles at a current density of 0.1 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. As can be seen from Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea, after 300 cycles, the reversible capacity of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C decreased from 1168.65 to 723.08 mAh/g, while that of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e plummeted from 1204.12 to 205.37 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The capacity retention rate of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C was 61.87%, whereas that of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C was only 17.06%. These results indicate that Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C exhibits superior reversibility and cycling stability. The rate performance of materials under varying current densities is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb. As clearly observed from the figure, Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C demonstrates superior rate performance compared to Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e. When the current density increases to 5 A g⁻\u0026sup1;, Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e exhibits poor reversible capacity, merely reaching 3.47 mAh g⁻\u0026sup1;. In contrast, under the same current density, Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C maintains a capacity of 322.01 mAh g⁻\u0026sup1;. This enhancement can be attributed to the uniform coating derived from the high-temperature pyrolysis of ZIF-8 on the surface of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C, which results in a higher specific surface area, provides additional defects and porosity, and facilitates faster electron and ion transport during charge-discharge processes. Figures\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec and d present the distinct discharge/charge voltage profiles of electrodes Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C under various current densities. As observed, these profiles exhibit similar variation trends, each comprising a rapid decline region (3-0.85 V), a plateau region (0.85 V), and a sloping region (0.75\u0026thinsp;\u0026minus;\u0026thinsp;0.01 V). In Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec, as the cycle number increases from 1st to 300th, noticeable attenuation occurs in both the plateau and sloping regions. This indicates that electrode Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e fails to adequately sustain the conversion reaction and surface interfacial processes at elevated current densities. In contrast, electrode Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C maintains a high and stable capacity, with nearly identical plateau regions across different cycle number and a reversible capacity in the sloping region still exceeding 600 mAh g⁻\u0026sup1;, demonstrating its superior interfacial lithium-ion storage capability.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTo further investigate the kinetic differences between Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C during the charging and discharging processes, electrochemical impedance spectroscopy (EIS) was conducted over a frequency range of 0.1 Hz to 100 kHz. The results are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. The Nyquist plots of both electrodes exhibit a similar pattern, consisting of a depressed semicircle in the medium-to-high frequency region and a sloped line in the low-frequency region. The semicircle corresponds to the charge transfer resistance and contact impedance, while the sloped line is associated with ion diffusion between the electrolyte and the electrode surface [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Notably, the diameter of the depressed semicircle for Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C is significantly smaller than that of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, indicating lower contact and charge transfer resistances. These results suggest that the carbon layer formed on the surface of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e after the high-temperature pyrolysis of introduced ZIF-8 can enhance the electrical conductivity and electrochemical activity of the electrode material, which is crucial for electron transfer and performance during lithium-ion cycling.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eWe investigated the electrochemical kinetics of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C by employing cyclic voltammetry (CV) at different scan rates. The results are presented in Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea and e. It can be observed that both the oxidation and reduction peaks progressively shift as the scan rate increases. To qualitatively analyze this behavior, the relationship between the current and the scan rate was derived from the CV curves obtained at various scan rates, as described by Equations (1) and (2) below [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003ei\u003c/em\u003e\u0026thinsp;=\u0026thinsp;a \u003cem\u003ev\u003c/em\u003e\u003csup\u003eb\u003c/sup\u003e (1)\u003c/p\u003e\u003cp\u003elog(\u003cem\u003ei\u003c/em\u003e)\u0026thinsp;=\u0026thinsp;b log(\u003cem\u003ev\u003c/em\u003e)\u0026thinsp;+\u0026thinsp;log(a) (2)\u003c/p\u003e\u003cp\u003eWhere, \u003cem\u003ei\u003c/em\u003e and \u003cem\u003ev\u003c/em\u003e represent the peak current and scan rate, respectively, and a is a constant. The value of b was determined by plotting the fitted line of log(\u003cem\u003ei\u003c/em\u003e) versus log(\u003cem\u003ev\u003c/em\u003e) and calculating its slope. If b value close to 0.5 suggests a process that is primarily diffusion-controlled, while a value approaching 1.0 indicates capacitive behavior [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAs illustrated in Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eb and d, the b-values were determined through curve fitting. The calculated b-values for Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C are 0.454 and 0.7866, respectively. These results indicate that the Li⁺ storage process in Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e is primarily controlled by diffusion behavior, whereas in Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C it is dominated by capacitive behavior. The specific percentage of the pseudocapacitive contribution can be quantified using Eq.\u0026nbsp;(3) [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cem\u003ei\u003c/em\u003e(\u003cem\u003eV\u003c/em\u003e)\u0026thinsp;=\u0026thinsp;\u003cem\u003ek\u003c/em\u003e\u003csub\u003e1\u003c/sub\u003ev\u0026thinsp;+\u0026thinsp;\u003cem\u003ek\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e\u003cem\u003ev\u003c/em\u003e\u003csup\u003e1/2\u003c/sup\u003e (3)\u003c/p\u003e\u003cp\u003eTo elucidate the specific contributions of the electrodes at fixed scan rates, the respective contributions of pseudocapacitive (\u003cem\u003ek\u003c/em\u003e₁\u003cem\u003ev\u003c/em\u003e) and diffusion-controlled (\u003cem\u003ek\u003c/em\u003e₂\u003cem\u003ev\u003c/em\u003e\u0026sup1;ᐟ\u0026sup2;) processes to the total current at a fixed potential (\u003cem\u003ev\u003c/em\u003e) were deconvoluted. The values of \u003cem\u003ek\u003c/em\u003e₁ and \u003cem\u003ek\u003c/em\u003e₂ can be readily determined by fitting the plot of \u003cem\u003ei\u003c/em\u003e(\u003cem\u003ev\u003c/em\u003e)/\u003cem\u003ev\u003c/em\u003e\u0026sup1;ᐟ\u0026sup2; versus \u003cem\u003ev\u003c/em\u003e\u0026sup1;ᐟ\u0026sup2; [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. As observed in the CV curves presented in Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ec and g, at a scan rate of 1 mV s⁻\u0026sup1;, approximately 60.10% and 89.17% of the total capacity for Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C, respectively, are attributed to capacitive contributions. Furthermore, the proportion of capacitive contribution increases correspondingly with increasing scan rate (Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ed and h). The bar charts clearly illustrate that for Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, the pseudocapacitive contribution rates at scan rates of 0.2, 0.4, 0.6, 0.8, and 1.0 mV s⁻\u0026sup1; are 22.87%, 31.16%, 38.59%, 46.48%and 60.10%, respectively, while those for material Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C is 65.17%, 72.48%, 81.18%, 85.86%and 89.17%. These results indicate that at high current densities, the capacity of the electrode materials is predominantly governed by surface-driven pseudocapacitive behavior.\u003c/p\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eIn conclusion, we have successfully synthesized the Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C nanoparticles through a simple chemical precipitation process, employing iron concentrate leachate as the source of iron. The use of ZIF-8 of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C sample improved the electrical conductivity and lithium-ion diffusion kinetics by providing porous structures, resulting in improved electrochemical performance. The reversible capacity of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C decreased from 1168.65 to 723.08 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e after 100 cycles. The capacity still exhibited as high as 322.01 mA h g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e even at a high rate of 5 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. This work can provide useful guidance for the development of preparation of electrode materials from solid waste.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eGuimin Zhou and Yin Li worte the main manuscript text. Li Wang, Yaochun Yao and Shaoze Zhang prepared figures 1-3. Keyu Zhang, Junxian Hu, Zhunqin Dong and Lingling Yuan prepared figures 4-7. All authors reviewed the manuscript\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e\u003cp\u003eThis work is financial supported by National Natural Science Foundation of China (Grant No. 52567025), Yunnan Fundamental Research Projects (Grant NO. 202301BE070001-065, 202301AU070055, 202402AF080003 and 202401AS070069).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of competing interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eG. Zubi, R. Dufo-Lopez, M. Carvalho, G. Pasaoglu, The lithium-ion battery: state of the art and future perspectives, Renew Sust Energ Rev. 89 (2018) 292-308.\u003c/li\u003e\n\u003cli\u003eA. Eftekhari, Lithium batteries for electric vehicles: from economy to research strategy, ACS Sustain. 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Zhou, et al., Graphene-based composites for electrochemical energy storage, Energy Storage Mater. 24 (2020) 22-51.\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":"Fe2O3@C composite, Iron concentrate leachate, ZIF-8, Lithium-ion battery, Anode material","lastPublishedDoi":"10.21203/rs.3.rs-7737011/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7737011/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eYolk-shell structure Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C composite by utilizing the iron concentrate leachate with a selective chemical precipitation method and illustrate its great potential as a high-performance anode material of lithium-ion batteries (LIBs). The Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C composite exhibits superior cyclic performance (723.08 mA h g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e over 300 cycles at 1 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and high-rate capability (322.01 mA h g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e even at a high current density of 5 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) in a half cell. The excellent performance of the Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C can be attributed to particles contain abundant internal voids, which facilitates the infiltration of the electrolyte and alleviates the volume change of electrode material, thereby enhancing the electrochemical performance of the material. Due to the unique yolk-shell structure nanostructure, Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@C composite shows significant pseudocapacitive behavior during discharge/charge processes, which partially accounts for the excellent lithium-ion storage performance.\u003c/p\u003e","manuscriptTitle":"Yolk-shell structure Fe2O3@C nanocomposite anode material prepared from the leaching solution of iron concentrate for lithium-ion batteries","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-27 11:43:40","doi":"10.21203/rs.3.rs-7737011/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-11-01T20:22:46+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-27T02:18:15+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-26T06:19:13+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-24T08:49:37+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-23T12:12:21+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-21T05:07:01+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"214384088078989388731216042785931056872","date":"2025-10-20T13:45:07+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-16T03:27:22+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"264870409681203091444815243251475059515","date":"2025-10-14T09:54:44+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"252433144966193795883218821723275827027","date":"2025-10-14T07:38:34+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"74902929193517528384560682899213948481","date":"2025-10-14T02:23:14+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"286205264261145989168075558725700575984","date":"2025-10-14T01:05:43+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"143251539391500163435765807516385940853","date":"2025-10-13T23:39:31+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"221192198070923001098673809827826454929","date":"2025-10-13T22:47:14+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-10-13T21:28:01+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-10-13T00:37:28+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-10-13T00:36:40+00:00","index":"","fulltext":""},{"type":"submitted","content":"Ionics","date":"2025-09-29T01:41:23+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":"77089c13-11bc-4435-9247-589ddffce926","owner":[],"postedDate":"October 27th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-12-07T12:08:37+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-27 11:43:40","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7737011","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7737011","identity":"rs-7737011","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}