Silicon monoxide negative electrode material coated with a mixed conductor layer and method for producing the same
By forming an amorphous carbon layer with uniformly dispersed lithium-ion conductive active sites on the surface of pre-lithiated SiOx materials, the problems of uneven conductivity and gas generation in pre-lithiated SiOx materials are solved, the electrode reaction kinetics and cycle stability are improved, and the battery performance is enhanced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- UNIV OF SCI & TECH BEIJING
- Filing Date
- 2024-09-13
- Publication Date
- 2026-07-07
AI Technical Summary
Existing pre-lithiated SiOx materials exhibit inhomogeneity in improving electronic conductivity and lithium-ion conductivity, resulting in poor electrochemical performance, particularly poor rate and low-temperature performance, while also suffering from severe gas generation problems.
By employing a hybrid conductor layer coating technology, an amorphous carbon layer with uniformly dispersed lithium-ion conductive active sites is formed on the surface of pre-lithium SiOx material. Combined with liquid-phase or solid-phase coating processes, a continuous and uniform conductive coating layer is formed, which improves electronic and lithium-ion conductivity and avoids direct contact with the electrolyte.
The electrode reaction kinetics of the pre-lithiated SiOx material were improved, which enhanced rate performance and cycle stability, reduced gas generation issues, and improved battery energy density and safety.
Smart Images
Figure CN119153651B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of battery technology, specifically to a hybrid conductor layer coated silicon suboxide anode material and its preparation method. Background Technology
[0002] Silicon (Si) anode materials are considered the most promising alternative to traditional graphite anodes due to their high theoretical specific capacity (4200 mAh / g), environmental friendliness, and abundant reserves. However, Si undergoes a significant volume change (approximately 300%) during lithium storage, leading to electrode pulverization, current collector detachment, and unstable SEI, severely limiting its commercialization. SiOx anode materials form inert lithiation products (lithium silicate or lithium oxide) during the initial lithiation reaction, which buffers the volume expansion during charge and discharge, improving cycle stability. Compared to elemental Si, SiOx exhibits significantly improved cycle stability. However, SiOx materials still experience some volume expansion during charge and discharge, resulting in less than ideal cycle performance. Furthermore, the formation of inert materials consumes some of the limited active lithium, leading to a lower initial coulombic efficiency for SiOx materials, affecting the battery's energy density. Pre-lithiation technology can significantly improve the initial coulombic efficiency of SiOx, thereby increasing the overall battery energy density. Commonly used prelithiation techniques include electrochemical prelithiation, chemical prelithiation, direct contact prelithiation with lithium metal, and direct addition of prelithiation reagents.
[0003] Current research on improving the electrode reaction kinetics of pre-lithiated SiOx materials only addresses the electronic conductivity, lacking studies on modifying lithium-ion conductivity. Furthermore, existing studies simultaneously improving both electronic and lithium-ion conductivity of pre-lithiated SiOx materials are not only complex in their processes, but also suffer from uneven dispersion of these components in the mixed electronic / ionic conductive layer, hindering the synergistic improvement of both electronic and ionic conductivity. This results in poor electrochemical performance of current pre-lithiated SiOx materials, particularly in rate capability and low-temperature performance.
[0004] Patent CN113823772A discloses a pre-lithiated SiOx material coated with a double conductive layer, wherein the inner coating layer is an electronically conductive coating layer and the outer coating layer is a lithium-ion conductive coating layer. The double conductive layer not only significantly constrains the expansion of the SiOx material but also improves the electrode reaction kinetics of the pre-lithiated SiOx material to some extent. However, the inner and outer double-layer structure of the electronic and ion conductive layers is not conducive to leveraging the synergistic characteristics of electronic / lithium-ion conductors. The lithium conductivity in the electronically conductive layer is poor, or the electron conductivity in the ion conductive layer is poor, thus limiting the improvement of the performance of the pre-lithiated SiOx material.
[0005] Secondly, the gas generation problem of existing pre-lithiated SiOx materials remains serious and has not been well resolved. This is because it is currently difficult to achieve continuous and uniform coating of pre-lithiated SiOx materials to avoid direct contact with water during slurry preparation. For example, patent CN105932224A discloses a modified silicon-based anode material embedded with lithium ions. The preparation method involves pre-lithiating carbon-coated silicon-based oxide anode materials with a lithium-aromatic hydrocarbon complex solution to improve the initial coulombic efficiency of the anode material. However, the resulting material contains a large amount of residual alkaline substances such as LiOH and Li2CO3 on the exposed surface of the pre-lithiated SiOx material, leading to excessive alkalinity in the slurry during preparation, causing gas generation, resulting in excessively high porosity and resistance of the electrode, and poor electrochemical performance.
[0006] Therefore, there is a need for a pre-lithium SiOx material with a hybrid conductor surface coating that has excellent electronic / ionic conductivity. Summary of the Invention
[0007] This invention provides a hybrid conductor layer coated silicon suboxide anode material, the material including a pre-lithium SiOx material, the surface of the pre-lithium SiOx material having a coating layer, the coating layer structure being an amorphous carbon layer with uniformly dispersed lithium ion conductive active sites inside.
[0008] Furthermore, the lithium-ion conductive active sites include fast lithium-ion conductors or materials with low lithium-ion diffusion barriers, wherein the fast lithium-ion conductor has a lithium-ion conductivity of not less than 10. -7 S / cm, the lithium-ion diffusion barrier of the low lithium-ion diffusion barrier material is not higher than 0.3eV.
[0009] Meanwhile, this invention provides a method for preparing a silicon suboxide anode material coated with a hybrid conductor layer, comprising the following steps:
[0010] Preparation of precursor-coated SiOx material: SiOx / C particles are added to the precursor solution and a coating process is used to obtain precursor-coated SiOx material;
[0011] Prepare chemical pre-lithiation agent solution;
[0012] Lithification reduction: The precursor-coated SiOx material is immersed in a pre-lithiating agent solution and stirred for a period of time under an inert atmosphere. Then it is washed and dried to obtain the lithiated SiOx material.
[0013] Heat treatment: The lithium-ionized SiOx material is calcined and then kept at a certain temperature to obtain a mixed conductor layer coated with pre-lithiated SiOx material.
[0014] Furthermore, regarding the selection of the precursor, based on first-principles calculations, a precursor is selected where the lowest unoccupied molecular orbital potential (LUMO) is lower than the HOMO value of the chemical pre-lithiation agent, and the lithium reduction product contains a lithium compound, wherein the lithium-ion conductivity of the lithium compound is not less than 10. -7 The lithium-ion diffusion barrier of a material with a S / cm or a low lithium-ion diffusion barrier is not higher than 0.3 eV.
[0015] Furthermore, the precursor includes one or more of the following substances:
[0016] a. After a lithium reduction reaction with a chemical pre-lithiation agent, it can generate a product with a lithium-ion conductivity of not less than 10. -7 Ionic conductor with S / cm;
[0017] b. After undergoing a lithiation reduction reaction with a chemical prelithiation agent, it can generate a reduction product with a lithium ion diffusion barrier of no more than 0.3 eV;
[0018] c. After undergoing a lithiation reduction reaction with a chemical prelithiation agent, it can generate a linear polymer;
[0019] d. After undergoing a lithiation reduction reaction with a chemical prelithiation agent, it can simultaneously generate a lithium-ion conductor and a linear polymer.
[0020] Furthermore, the ionic conductor is Li3PO4, Li3BO3, or LiAlO2.
[0021] Furthermore, the reduction product is LiF.
[0022] Furthermore, the coating process is a liquid phase coating process, which is a combination of liquid phase mixing and rotary evaporation or liquid phase mixing and spray drying.
[0023] Alternatively, the coating process is a solid-phase coating process, which is one of sand milling and mixing, VC mixing, hot kneading, and mechanical fusion.
[0024] Furthermore, the chemical pre-lithiation agent solution is prepared using metallic lithium, aromatic hydrocarbons, and solvents.
[0025] Furthermore, the aromatic hydrocarbon is selected from one or more of biphenyl-type aromatic compounds such as biphenyl and 4-methylbiphenyl, polycyclic aromatic hydrocarbons and their derivatives; the solvent is selected from one or more of ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, and tetrahydropyran.
[0026] The pre-lithiated SiOx material of the present invention has a surface coating structure consisting of an amorphous carbon layer with uniformly dispersed fast lithium-ion conductive active sites. This mixed conductive coating layer facilitates the acceleration of electron and lithium-ion conduction, improves the electrode reaction kinetics of the pre-lithiated SiOx material, and enhances the material's rate performance. On the other hand, the continuous and uniform conductive coating layer not only effectively avoids direct contact between the pre-lithiated SiOx and the electrolyte, improving the material's resistance to electrolyte corrosion, but also helps to homogenize the surface current density and electrode reaction degree of the pre-lithiated SiOx, eliminates structural stress caused by uneven volume expansion, and improves the material's structural and cycling stability. Attached Figure Description
[0027] Figure 1 This is a schematic diagram of the structure of the hybrid conductor layer coated silicon suboxide anode material of the present invention;
[0028] Figure 2 These are the initial charge-discharge curves of the silicon suboxide anode material before and after the mixed conductor layer is coated;
[0029] Figure 3 It is the cycle performance of silicon suboxide anode materials before and after the mixed conductor layer is coated. Detailed Implementation
[0030] See Figure 1 The pre-lithiated SiOx material of the present invention has a surface coating structure consisting of an amorphous carbon layer with fast lithium-ion conductive active sites uniformly dispersed inside. This mixed conductive coating layer facilitates the acceleration of electron and lithium-ion conduction, improves the electrode reaction kinetics of the pre-lithiated SiOx material, and enhances the rate performance of the material. On the other hand, the continuous and uniform conductive coating layer not only effectively avoids direct contact between the pre-lithiated SiOx and the electrolyte, improving the material's resistance to electrolyte corrosion, but also helps to homogenize the surface current density and electrode reaction degree of the pre-lithiated SiOx, eliminates structural stress caused by uneven volume expansion, and improves the structural and cycling stability of the material.
[0031] The lithium-ion conducting active sites include fast lithium-ion conductors or materials with low lithium-ion diffusion barriers, wherein the fast lithium-ion conductor has a lithium-ion conductivity of not less than 10. -7 S / cm, the lithium-ion diffusion barrier of the low lithium-ion diffusion barrier material is not higher than 0.3eV.
[0032] To achieve the above structure, the main idea of this invention is to select a specific precursor to coat the SiOx material to obtain a precursor-coated SiOx material; then, the material is pre-lithiated, during which the precursor is transformed in situ into a coating layer of "fast ion conductor + amorphous carbon", and finally a mixed conductor layer is obtained to continuously coat the pre-lithiated SiOx material.
[0033] Specifically, this invention proposes a method for manufacturing a pre-lithium SiOx material with a surface coating layer of a hybrid conductor (capable of simultaneous rapid electron and lithium-ion conduction) exhibiting excellent electronic and ionic conductivity properties, comprising the following steps:
[0034] S1: Preparation of precursor-coated SiOx material: SiOx / C particles are added to the precursor solution and a coating process is used to obtain precursor-coated SiOx material;
[0035] For the selection of precursors, based on first-principles calculations, lithium compounds with low least unoccupied molecular orbital potentials (LUMO) and low ion migration activation energies in their lithium reduction products were screened. Specifically, the LUMO was lower than the HOMO value of the chemical prelithiation agent, and the lithium compound exhibited a lithium-ion conductivity of not less than 10. -7 S / cm, or the lithium-ion diffusion barrier of its low lithium-ion diffusion barrier material is not higher than 0.3eV.
[0036] Specifically, the precursor includes one or more of the following:
[0037] a. After a lithiation reduction reaction with a chemical prelithiation agent, it can generate substances such as Li3PO4, Li3BO3, or LiAlO2, which have high lithium-ion conductivity (not less than 10). -7 An ionic conductor with a density of S / cm;
[0038] b. After undergoing a lithiation reduction reaction with a chemical prelithiation agent, it can generate reduction products such as LiF, which have a low lithium-ion diffusion barrier (not higher than 0.3 eV).
[0039] Higher lithium-ion conductivity can effectively improve the transport rate of lithium ions inside and between SiOx particles, accelerating the electrode reaction kinetics; while a lower lithium-ion diffusion barrier can effectively prevent the local accumulation of lithium ions on the particle surface and the formation of lithium dendrites, thus improving battery safety performance.
[0040] c. After undergoing a lithiation reduction reaction with a chemical prelithiation agent, it can generate a linear polymer;
[0041] d. After undergoing a lithiation reduction reaction with a chemical prelithiation agent, it can simultaneously generate a lithium-ion conductor and a linear polymer;
[0042] The linear structure of polymer molecules facilitates a closer bond with SiOx materials, and during calcination, a carbon coating layer is formed that tightly encapsulates the pre-lithium SiOx material through a carbonization reaction.
[0043] The coating process can be either liquid-phase coating or solid-phase coating, depending on the specific precursor material. For soluble precursor materials, liquid-phase coating is preferred, such as liquid-phase mixing and stirring + rotary evaporation or liquid-phase mixing and stirring + spray drying. For insoluble precursor materials, solid-phase coating is preferred, such as sand milling, VC mixing, thermal kneading, mechanical fusion, etc.
[0044] S2: Prepare a chemical pre-lithiation agent solution: The half-wave potential of the chemical pre-lithiation agent solution is 0.02 to 1.5V, preferably 0.05 to 0.6V.
[0045] The chemical lithium solution is prepared using metallic lithium, aromatic hydrocarbons, and a solvent. The aromatic hydrocarbons include biphenyl-type aromatic compounds such as biphenyl and 4-methylbiphenyl, as well as fused-ring aromatic hydrocarbons such as naphthalene and anthracene and their derivatives. The solvents include ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, and tetrahydropyran. The molar ratio of metallic lithium to aromatic hydrocarbons is 1:1 to 10, and the concentration of the lithium-aromatic hydrocarbon complex after the complexation reaction in the solvent is 0.2 to 3 mol / L.
[0046] S3: Lithification reduction: The precursor-coated SiOx material is immersed in a pre-lithiating agent solution, stirred for a certain time under an inert atmosphere and at a certain temperature, and then washed and dried to obtain the lithiated SiOx material.
[0047] Utilizing the strong reducing properties of chemical pre-lithiation agents, SiOx materials undergo a lithiation reduction reaction. This step involves the reaction Li-AC + SiOx = Li-SiOx + AC, yielding lithiated SiOx materials. Simultaneously, the lithiation reduction generates a mixed conductive coating layer. Here, AC represents an aromatic hydrocarbon.
[0048] Specifically, the stirring temperature range is 5–80℃, preferably 20–50℃. The stirring time ranges from 1 to 50 hours, preferably 5–25 hours. The washing methods include high-speed centrifugal washing and vacuum filtration washing.
[0049] S4: Heat treatment: The lithium-ionized SiOx material is calcined and then kept at a constant temperature to obtain a mixed conductor layer coated with pre-lithiated SiOx material.
[0050] During calcination, the following reaction occurs: Li-SiOx = Lithium silicate + Si, where lithium silicate includes Li2SiO3, Li2Si2O5, Li4SiO4, Li8SiO6, etc. Simultaneously, the polymer in the mixed conductive coating layer, after reduction in step S3, is converted into carbon. The final material is a pre-lithium SiOx material with a surface coating layer. The surface coating layer structure consists of an amorphous carbon layer with uniformly dispersed fast lithium-ion conductive active sites. This mixed conductive coating layer facilitates accelerated electron and lithium-ion conduction.
[0051] Specifically, during the heat treatment process, the environment is an inert gas atmosphere (e.g., argon) with a flow rate of 0.1–2 L / min; the heating rate is 1–10 °C / min; the temperature is 600–1000 °C; and the holding time is 0.5–10 h.
[0052] Several examples are given below to illustrate the preparation method in detail:
[0053] Example 1:
[0054] Fluoroethylene carbonate was selected as the precursor and dissolved in dimethyl carbonate at a volume ratio of 1:50. SiO₂ was then added. x / C particles, in which fluoroethylene carbonate and SiO x The mass ratio of / C particles was 1:5, and the mixture was stirred for 1 hour. Then, the solvent was removed by rotary evaporation to obtain the precursor-coated SiOx material.
[0055] A 1 mol / L solution of 4-methylbiphenyl-2-methyltetrahydrofuran was prepared, and lithium metal sheets were added to it. The molar ratio of lithium sheets to 4-methylbiphenyl was 4:1. After stirring thoroughly for 2 hours, a chemical pre-lithiation agent solution was obtained.
[0056] According to SiO x The precursor-coated SiOx material was added to the chemical pre-lithiation agent at a mass ratio of / C particles to lithium metal of 10:1 and stirred in a water bath at 45°C for 15 hours. The solution was then removed by centrifugation and washing, and the material was dried at 60°C. Finally, the dried material was placed in a tube furnace for calcination at 600°C for 4 hours.
[0057] Fluoroethylene carbonate undergoes a reduction reaction under the action of a chemical pre-lithiation agent solution, forming LiF and a polymer layer. The former is uniformly dispersed in the polymer layer in the form of nanocrystals. During the subsequent heat treatment, it is carbonized to form a mixed conductive coating layer containing LiF and C. This coating layer not only effectively prevents direct contact between the pre-lithiated SiOx / C material and the electrolyte, thus avoiding electrode side reactions, but its excellent electronic and lithium-ion conductivity also effectively improves the electrode reaction kinetics of the material, thereby improving the rate performance of the material.
[0058] Example 2
[0059] Lithium difluorophosphate and vinylene carbonate were selected as precursors and dissolved in dimethyl carbonate at a volume ratio of 1:50. SiO₂ was then added. x / C particles, in which lithium difluorophosphate and vinylene carbonate and SiO x The mass ratio of / C particles was 1:5, and the mixture was stirred for 1 hour. Then, the solvent was removed by spray drying to obtain the precursor-coated SiOx material.
[0060] A 1 mol / L biphenyl-tetrahydrofuran solution was prepared, and lithium metal sheets were added to it. The molar ratio of lithium sheets to 4-methylbiphenyl was 4:1. After stirring thoroughly for 2 hours, a chemical pre-lithiation agent solution was obtained.
[0061] According to SiO x The precursor-coated SiOx material was added to a chemical pre-lithiation agent at a mass ratio of / C particles to lithium metal of 10:1 and stirred in a water bath at 45°C for 15 hours. The solution was then removed by centrifugation and washing, and the material was dried at 60°C. Finally, the dried material was placed in a tube furnace for calcination at 700°C for 6 hours.
[0062] Example 3
[0063] Ethylene carbonate and vinylene carbonate were selected as precursors and dissolved in dimethyl carbonate at a volume ratio of 1:50. SiO₂ was then added. x / C particles, in which ethylene carbonate and ethylene carbonate and SiO x The mass ratio of / C particles was 1:5, and the mixture was stirred for 1 hour. Then, the solvent was removed by spray drying to obtain the precursor-coated SiOx material.
[0064] A 1 mol / L solution of 4-methylbiphenyl-tetrahydrofuran was prepared, and lithium metal sheets were added to it. The molar ratio of lithium sheets to 4-methylbiphenyl was 4:1. After stirring thoroughly for 2 hours, a chemical pre-lithiation agent solution was obtained.
[0065] According to SiO x The precursor-coated SiOx material was added to the chemical pre-lithiation agent at a mass ratio of / C particles to lithium metal of 10:1 and stirred in a water bath at 45°C for 15 hours. The solution was then removed by centrifugation and washing, and the material was dried at 60°C. Finally, the dried material was placed in a tube furnace for calcination at 600°C for 6 hours.
[0066] Example 4
[0067] Vinylene carbonate was selected as the precursor and dissolved in dimethyl carbonate at a volume ratio of 1:50. SiO₂ was then added. x / C particles, in which tris(pentafluorophenyl)borane and vinylene carbonate and SiO x The mass ratio of / C particles was 1:5, and the mixture was stirred for 1 hour. Then, the solvent was removed by rotary evaporation to obtain the precursor-coated SiOx material.
[0068] A 1 mol / L solution of 4-methylbiphenyl-tetrahydrofuran was prepared, and lithium metal sheets were added to it. The molar ratio of lithium sheets to 4-methylbiphenyl was 4:1. After stirring thoroughly for 2 hours, a chemical pre-lithiation agent solution was obtained.
[0069] According to SiO x The precursor-coated SiOx material was added to a chemical pre-lithiation agent at a mass ratio of / C particles to lithium metal of 10:1 and stirred in a water bath at 45°C for 15 hours. The solution was then removed by centrifugation and washing, and the material was dried at 60°C. Finally, the dried material was placed in a tube furnace for calcination at 800°C for 4 hours.
[0070] Comparative Example 1
[0071] In this invention, SiOx material is coated with a precursor, followed by a pre-lithiation operation. During the pre-lithiation process, the precursor is transformed in situ into a coating layer of "fast ion conductor + amorphous carbon," ultimately resulting in a continuous coating of pre-lithiated SiOx material with a mixed conductor layer. In contrast, SiOx / C material is directly reacted with a chemical pre-lithiation agent without precursor material coating treatment, for comparison.
[0072] A 1 mol / L solution of 4-methylbiphenyl-2-methyltetrahydrofuran was prepared, and lithium metal sheets were added to it. The molar ratio of lithium sheets to 4-methylbiphenyl was 4:1. After stirring thoroughly for 2 hours, a chemical pre-lithiation agent solution was obtained.
[0073] SiOx / C particles were added to a chemical pre-lithiation agent at a mass ratio of 10:1 to lithium metal, and stirred in a water bath at 45°C for 15 hours. The solution was then removed by centrifugation and washing, and the material was dried at 60°C. Finally, the dried material was placed in a tube furnace for calcination at 600°C for 4 hours.
[0074] Comparative Example 2
[0075] The calcination process is crucial for the formation of the hybrid conductive coating. During calcination, the polymer undergoes an in-situ transformation to form carbon, ensuring the excellent electronic conductivity of the hybrid conductive coating. In this comparative example, the battery was directly assembled after washing and drying the lithiation reaction products, without powder calcination.
[0076] Fluoroethylene carbonate was selected as the precursor and dissolved in dimethyl carbonate at a volume ratio of 1:50. SiO₂ was then added. x / C particles, in which fluoroethylene carbonate and SiO x The mass ratio of / C particles was 1:5, and the mixture was stirred for 1 hour. Then, the solvent was removed by rotary evaporation to obtain the precursor-coated SiOx material.
[0077] A 1 mol / L solution of 4-methylbiphenyl-2-methyltetrahydrofuran was prepared, and lithium metal sheets were added to it. The molar ratio of lithium sheets to 4-methylbiphenyl was 4:1. After stirring thoroughly for 2 hours, a chemical pre-lithiation agent solution was obtained.
[0078] The precursor-coated SiOx material was added to the chemical pre-lithiation agent at a mass ratio of SiOx / C particles to lithium metal of 10:1, and stirred in a water bath at 45°C for 15 hours. The solution was then removed by centrifugation and washing, and dried at 60°C.
[0079] The negative electrode material, conductive agent SP, carbon nanotubes, and binder (mass ratio CMC:SBR = 3:8) provided in Examples 1-4 and Comparative Examples 1 and 2 were mixed at a mass ratio of 85:4.8:0.2:10. The mixed slurry was uniformly coated on the surface of Cu foil and vacuum dried for 2 hours. The electrode sheet was then rolled to a compaction density of 1.2 g / cm3 to obtain the negative electrode sheet. Using lithium foil as the counter electrode, 1 mol / L LiPF6 / DMC+DEC+EC (volume ratio 1:1:1) as the electrolyte, 10% FEC as the electrolyte additive, and a glass fiber membrane as the separator, a coin cell was assembled in an argon-atmospheric glove box.
[0080] Electrochemical analysis and testing were performed on the coin cells assembled from Examples 1-4 and Comparative Examples 1-2. The charge-discharge range was 0.005-1.5V. The first week's charge-discharge test was conducted at a current density of 0.05C, and the discharge tests in the second week and thereafter were all conducted at a current density of 0.5C. The electrochemical performance is shown in Table 1.
[0081] Table 1 Electrochemical performance test results
[0082]
[0083]
[0084] like Figure 2 As shown in Figure 3, when comparing Example 1 with Comparative Example 1, the initial coulombic efficiency was slightly reduced due to the introduction of inactive materials such as LiF, but the capacity retention was significantly improved. This is because a coating layer of "fast ion conductor + amorphous carbon" was constructed, which improved its conductivity and electrochemical performance.
[0085] Comparing Example 1 with Comparative Example 2, Comparative Example 2 was not subjected to calcination stabilization treatment, resulting in a higher content of active lithium. During the subsequent coating process, the active lithium reacted with air or water, causing its electrochemical performance to deteriorate.
[0086] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing a silicon suboxide anode material coated with a hybrid conductor layer, characterized in that, Includes the following steps: Preparation of precursor-coated SiOx material: SiOx / C particles are added to the precursor solution and a coating process is used to obtain precursor-coated SiOx material; Prepare chemical pre-lithiation agent solution; Lithification reduction: The precursor-coated SiOx material is immersed in a pre-lithiating agent solution and stirred for a period of time under an inert atmosphere. Then it is washed and dried to obtain the lithiated SiOx material. Heat treatment: The lithium-ionized SiOx material is calcined and then kept at a certain temperature to obtain a mixed conductor layer coated with pre-lithiated SiOx material; The precursor includes one or more of the following substances: a. After a lithiation reduction reaction with a chemical prelithiation agent, it can generate a product with a lithium-ion conductivity of not less than 10. -7 Ionic conductor with S / cm; b. After undergoing a lithiation reduction reaction with a chemical prelithiation agent, it can generate a reduction product with a lithium-ion diffusion barrier of no more than 0.3 eV; c. After undergoing a lithiation reduction reaction with a chemical prelithiation agent, it can generate a linear polymer; d. After undergoing a lithiation reduction reaction with a chemical prelithiation agent, it can simultaneously generate a lithium-ion conductor and a linear polymer; The lithium-ion conductor is Li3PO4, Li3BO3 or LiAlO2; The reduction product is LiF; The chemical prelithiation agent solution is prepared from metallic lithium, aromatic hydrocarbons and solvents; The aromatic hydrocarbon is selected from one or more of biphenyl, 4-methylbiphenyl, polycyclic aromatic hydrocarbons and their derivatives; the solvent is selected from one or more of ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, and tetrahydropyran.
2. The preparation method according to claim 1, characterized in that, For the selection of the precursor, based on first-principles calculations, the precursor is selected where the lowest unoccupied molecular orbital potential (LUMO) is lower than the HOMO value of the chemical prelithiation agent, and the lithium reduction product contains a lithium compound, wherein the lithium-ion conductivity of the lithium compound is not less than 10. -7 The lithium-ion diffusion barrier of a material with a S / cm or a low lithium-ion diffusion barrier is not higher than 0.3 eV.
3. The preparation method according to claim 1 or 2, characterized in that, The coating process is a liquid phase coating process, which is a combination of liquid phase mixing and rotary evaporation or liquid phase mixing and spray drying. Alternatively, the coating process is a solid-phase coating process, which is one of sand milling and mixing, VC mixing, hot kneading, and mechanical fusion.
4. A hybrid conductor layer coated silicon suboxide anode material, characterized in that, The material is prepared by any one of claims 1-3, and the material includes a pre-lithium SiOx material. The surface of the pre-lithium SiOx material has a coating layer, and the coating layer structure is an amorphous carbon layer with uniformly dispersed lithium-ion conductive active sites inside.
5. The hybrid conductor layer coated silicon suboxide anode material according to claim 4, characterized in that, The lithium-ion conductive active sites include fast lithium-ion conductors or materials with low lithium-ion diffusion barriers, wherein the fast lithium-ion conductor has a lithium-ion conductivity of not less than 10. -7 S / cm, the lithium-ion diffusion barrier of the low lithium-ion diffusion barrier material is not higher than 0.3 eV.