Silicon negative electrode material, preparation method thereof and lithium ion battery
By using a combination of carbon skeleton and rare earth oxide coating in silicon anode materials, the problems of volume expansion and poor processing performance of silicon anode materials are solved, and higher cycle stability and safety are achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-16
- Publication Date
- 2026-03-27
AI Technical Summary
Existing silicon anode materials suffer from problems such as high volume expansion, poor processing performance, and poor structural stability in lithium-ion batteries, resulting in poor cycle stability.
Using carbon materials as a framework, silicon is deposited inside and on the surface of the carbon material pores, and a rare earth oxide coating is applied to the outer layer. The carbon framework and rare earth oxide coating are used to mitigate volume expansion and improve the material's processing performance and cycle stability.
It effectively suppresses the volume expansion of the material during charging and discharging, improves processing performance and cycle stability, reduces interface resistance, enhances electronic conduction, and improves the safety and cycle life of the material.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery material technology, specifically relating to a silicon anode material, its preparation method, and a lithium-ion battery. Background Technology
[0002] Currently, graphite is the primary anode material for lithium-ion batteries, with a theoretical specific capacity of 372 mAh / g and limited potential for energy density improvement. Silicon-based materials, with a theoretical specific capacity of 4200 mAh / g, far exceed that of graphite, making them one of the most promising anode materials and attracting widespread attention in the industry. However, the expansion that occurs during charging and discharging leads to two main problems: firstly, the silicon anode material cracks and pulverizes, resulting in irreversible capacity loss and low initial coulombic efficiency; secondly, the expansion during charging and discharging causes capacity decay and poor cycle stability.
[0003] The key to the practical application of silicon anode materials lies in effectively suppressing the volume change of silicon and improving the cycle life and energy density of silicon anode materials. The most common method to suppress the expansion of pure silicon anode materials is to composite silicon and carbon materials. Usually, the high stability of carbon materials is used to coat silicon materials or to embed silicon materials into carbon materials to prepare silicon-carbon composite anode materials.
[0004] The main methods for preparing silicon anode materials are chemical vapor deposition (CVD) and mechanical ball milling. Comparatively, silicon-carbon composite materials obtained by mechanical ball milling are prone to agglomeration, leading to poor battery performance. Currently, the more popular CVD method uses porous carbon as a matrix, embedding silicon within it. The pores of the carbon help mitigate volume expansion, thereby improving the material's electrochemical performance. However, this method uses silane gas, posing significant safety risks. Furthermore, the material has poor processing performance, and the volume expansion during charge and discharge results in poor cycle stability within the battery.
[0005] Therefore, how to further optimize silicon anode materials, improve material processing performance, further reduce volume expansion, and improve their cycle stability in lithium-ion batteries are urgent problems to be solved in this field. Summary of the Invention
[0006] The purpose of this invention is to provide a silicon anode material, its preparation method, and a lithium-ion battery, so as to solve the problems of high volume expansion, poor processing performance, and poor structural stability of silicon anode materials in the prior art, as well as the problem of poor cycle stability of lithium-ion batteries made from them.
[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a silicon anode material.
[0008] The silicon anode material includes a core and an oxide coating layer covering the surface of the core; The core includes a carbon skeleton, silicon-based material deposited inside and on the surface of the carbon skeleton pores, and a carbon coating layer covering the surface of the carbon skeleton. The oxide coating layer is rare earth M. x O y The coating layer, M is selected from one or more rare earth elements La, Y, Ce, Nd and Sm, and x:y=(1~2):(1~3).
[0009] The silicon anode material provided by this invention uses carbon material as a framework, with silicon deposited inside and on the surface of the carbon material pores. The carbon framework and surface carbon layer can alleviate the volume expansion of silicon, and the rare earth oxide coating layer further reduces the volume expansion of silicon-based materials during charging and discharging.
[0010] Furthermore, the specific surface area of the core is 0.5~1000m². 2 / g, pore volume 0.001~0.8cm 3 / g, with a particle size Dv50 of 0.5~50μm.
[0011] Furthermore, the thickness of the carbon coating layer is 0.5~80nm.
[0012] Furthermore, the thickness of the oxide coating layer is 0.5~100nm.
[0013] Furthermore, the carbon framework includes one or more of porous carbon, hard carbon, mesophase carbon microspheres, and graphite; Furthermore, the specific surface area of the carbon skeleton is 2~2500 m². 2 / g, pore volume 0.01~1.5cm 3 / g, wherein the particle size Dv50 of the carbon skeleton is 0.3~40μm.
[0014] Furthermore, the silicon-based material comprises one or more of silicon, silicon suboxide, and silicon dioxide; the silicon comprises at least one of crystalline silicon and amorphous silicon.
[0015] Furthermore, the silicon anode material has a particle size Dv50 of 0.5~50 μm, a specific surface area of 0.2~50 m² / g, and a total pore volume of 0.0001~0.2 cm³. 3 / g.
[0016] Furthermore, the silicon anode material has a silicon content of 5-80 wt%, a carbon content of 10-90 wt%, and a rare earth element content of 0.05-5 wt%.
[0017] Secondly, the present invention provides a method for preparing the silicon anode material described in the first aspect.
[0018] The method for preparing the silicon anode material provided by this invention includes the following steps: S1. Place the silicon-based material into the high-temperature sublimation chamber of the vacuum equipment, place the carbon skeleton material in the cooling deposition chamber of the vacuum equipment, and heat the silicon-based material at high temperature to sublimate it and deposit it into the pores and surface of the carbon skeleton material to prepare the core precursor. S2. Place the core precursor prepared in step S1 in a heat treatment device, and perform vapor deposition by introducing a carbon source in a protective atmosphere to prepare the core. S3. Coat the core surface obtained in step S2 with rare earth oxides to prepare the silicon anode material.
[0019] Furthermore, in step S1, the mass ratio of silicon-based material to carbon framework material is 1:(0.2~5).
[0020] Further, in step S1, the heat treatment temperature of the high-temperature sublimation chamber is 800~1600℃; the heat treatment time is 2~30h; and the vacuum pressure of the vacuum equipment is 10~10 -3 Pa.
[0021] Further, in step S2, the carbon source is selected from one or more of acetylene, methane, ethane, propane, butane, ethylene, propylene, butene, methanol, ethanol, propanol, and benzene.
[0022] Furthermore, in step S2, the carbon source deposition temperature is 600~1100℃, the isothermal time is 0.5~20h, and the carbon source introduction rate is 0.5~50L / min.
[0023] Furthermore, in step S3, the rare earth oxide includes at least one of Y2O3, La2O3, CeO2, Nd2O3, and Sm2O3.
[0024] Furthermore, in step S3, the mass ratio of the rare earth oxide to the core is 1:(10~500).
[0025] Furthermore, in step S3, rare earth oxides are coated onto the core surface using a solid-phase coating method; The solid-phase coating method specifically includes the following steps: mixing rare earth oxides with the core solid phase, then placing the mixture in a heat treatment device and sintering it under a protective atmosphere to obtain a silicon anode material with rare earth oxides coated on the core surface.
[0026] Furthermore, in step S3, rare earth oxides are coated onto the core surface using a liquid phase coating method; The liquid phase coating method specifically includes the following steps: uniformly dispersing rare earth oxides in a solvent to obtain a mixed solution; then mixing the core with the mixed solution to obtain a core viscous material uniformly coated with rare earth oxides; finally drying the viscous material and placing it in a heat treatment device for sintering under a protective atmosphere to obtain a silicon anode material with rare earth oxides coated on the surface of the core. The solvent is anhydrous ethanol, ethylene glycol, acetone, industrial alcohol, or deionized water; the mass ratio of the rare earth oxide to the solvent is 1:(10~1000).
[0027] Furthermore, in the solid-phase coating method or liquid-phase coating method, the sintering temperature is 600~1100℃ and the sintering time is 0.5~10h; Furthermore, the protective atmosphere is selected from one or more of nitrogen, argon, helium, neon, and krypton.
[0028] Thirdly, the present invention provides a lithium-ion battery.
[0029] The lithium-ion battery provided by the present invention includes the silicon anode material described in the first aspect or the silicon anode material prepared by the method described in the second aspect.
[0030] Compared with the prior art, the present invention has the following beneficial effects: The silicon anode material provided by this invention uses carbon material as a framework, with silicon deposited inside and on the surface of the carbon material's pores. The rare earth coating layer acts as a physical barrier, suppressing gas generation during the slurry coating process and improving the material's processing performance. It also prevents direct contact between the electrode and the electrolyte, avoiding repeated SEI film formation during charge and discharge, significantly reducing capacity decay. Simultaneously, the rare earth oxides exhibit corrosion resistance, effectively resisting the erosion of acidic substances in the electrolyte, improving electrolyte decomposition, and enhancing the material's cycle stability in lithium-ion batteries. Furthermore, the rare earth oxide coating layer effectively reduces interfacial resistance and enhances electron conduction; it may also form a fast ion conductor interface, improving rate performance. Moreover, the silicon anode material provided by this invention does not use silane gas, offering higher safety, a simpler process, and ease of mass production. Attached Figure Description
[0031] Figure 1 A schematic diagram of the structure of the silicon anode material provided by the present invention; 1. Carbon material; 2. Silicon material; 3. Carbon coating layer; 4. Rare earth oxide coating layer. Detailed Implementation
[0032] The present invention will be further described in detail below. The described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are also within the scope of protection of the present invention. This invention provides a silicon anode material, comprising a core and an oxide coating layer covering the surface of the core; the core includes a carbon skeleton, a silicon-based material deposited inside and on the surface of the carbon skeleton channels, and a carbon coating layer covering the surface of the carbon skeleton; the oxide coating layer is a rare earth M... x O y The coating layer, M is one or more of rare earth elements La, Y, Ce, Nd and Sm, x:y=(1~2):(1~3), preferably x:y=1:2 or 2:3.
[0033] In some embodiments, the specific surface area of the core is 0.5~1000m². 2 / g. Preferably, the specific surface area of the kernel is 0.6–100 m². 2 / g, or 1-50m 2 / g, or 1.5~20m 2 / g. Specifically, the specific surface area of the kernel can be 1m². 2 / g、3m 2 / g、5m 2 / g, 10m 2 / g or 20m 2 / g.
[0034] In some embodiments, the pore volume of the kernel is 0.001~0.8 cm³. 3 / g. Preferably, the pore volume of the kernel is 0.002~0.2cm³. 3 / g, for example 0.005cm 3 / g, 0.01cm 3 / g, 0.02cm 3 / g or 0.05cm 3 / g.
[0035] In some embodiments, the particle size Dv50 of the core is 0.5~50 μm. Preferably, the Dv50 of the silicon anode material is 3~30 μm, or 5~20 μm, or 5~15 μm. Specifically, the Dv50 of the core can be 3 μm, 5 μm, 6 μm, 8 μm, or 10 μm.
[0036] In some embodiments, the thickness of the oxide coating layer is 0.5~100 nm. Preferably, the thickness of the oxide coating layer is 1~80 nm, or 5~50 nm, or 10~50 nm. Specifically, the thickness of the oxide coating layer can be 5 nm, 10 nm, 15 nm, 20 nm, or 50 nm.
[0037] In some embodiments, the rare earth element content in the silicon anode material is 0.05~5wt%. For example, the rare earth element content can be 0.1wt%, 0.2wt%, 0.5wt%, 0.6wt%, 0.7wt%, 1wt%, or 2wt%.
[0038] In some embodiments, the carbon framework includes one or more of porous carbon, hard carbon, mesophase carbon microspheres, and graphite.
[0039] In some embodiments, the specific surface area of the carbon skeleton is 2~2500 m². 2 / g. Preferably, the specific surface area is 10–2500 m². 2 / g, or 100~2000m 2 / g, or 300~1800m 2 / g, specifically, the specific surface area can be 500m². 2 / g, 1000m 2 / g, 1500m 2 / g、2000m 2 / g or 2200m 2 / g.
[0040] In some embodiments, the pore volume of the carbon framework is 0.01~1.5 cm³. 3 / g. Preferably, the pore volume is 0.05~1.0cm³. 3 / g, for example 0.05cm 3 / g, 0.1cm 3 / g, 0.5cm 3 / g or 0.8cm 3 / g.
[0041] In some embodiments, the particle size Dv50 of the carbon skeleton is 0.3~40 μm. Preferably, the particle size Dv50 of the carbon skeleton is 3~30 μm, or 5~20 μm, or 5~15 μm. Specifically, Dv50 can be 3 μm, 5 μm, 6 μm, 8 μm, or 10 μm.
[0042] In some embodiments, the silicon-based material comprises one or more of silicon, silicon suboxide, and silicon dioxide; the silicon includes at least one of crystalline silicon and amorphous silicon.
[0043] In some embodiments, the thickness of the carbon coating layer is 0.5~80 nm; preferably, the thickness of the carbon coating layer is 1~60 nm, or 5~50 nm, or 10~40 nm. Specifically, the thickness of the carbon coating layer can be 5 nm, 10 nm, 15 nm, 20 nm, or 50 nm.
[0044] In some embodiments, the particle size Dv50 of the silicon anode material is 0.5~50 μm, for example 3 μm, 5 μm, 6 μm, 8 μm, 10 μm or 12 μm; the specific surface area of the silicon anode material is 0.2~50 m² / g, for example 0.5 m² / g. 2 / g、1m 2 / g、3m 2 / g、5m 2 / g or 10m 2 / g; the total pore volume of the silicon anode material is 0.0001~0.2cm³. 3 / g, for example, 0.001cm 3 / g, 0.002cm 3 / g, 0.005cm 3 / g or 0.01cm 3 / g.
[0045] In some embodiments, the silicon anode material contains 5-80 wt% silicon and 10-90 wt% carbon. For example, the silicon content can be 10 wt%, 20 wt%, 40 wt%, 50 wt%, or 60 wt%; the carbon content can be 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, or 70 wt%.
[0046] Another aspect of the present invention provides a method for preparing the above-mentioned silicon anode material, comprising the following steps: S1. Place the silicon-based material into the high-temperature sublimation chamber of the vacuum equipment, and place the carbon framework material into the cooling deposition chamber of the vacuum equipment. The silicon-based material is sublimated by high-temperature heating and deposited into the pores and surface of the carbon framework to prepare the core precursor. S2. Place the core precursor prepared in step S1 in a heat treatment device, and perform vapor deposition by introducing a carbon source in a protective atmosphere to prepare the core. S3. Coat the core surface of the step S2 with rare earth oxides to prepare the silicon anode material.
[0047] In some embodiments, the mass ratio of silicon-based material to carbon framework material in step S1 is 1:(0.2~5). Specifically, it can be 1:0.5, 1:1, 1:1.2, 1:1.5, or 1:2.
[0048] In some embodiments, the heat treatment temperature of the high-temperature sublimation chamber in step S1 is 800~1600℃; the heat treatment time is 2~30h. Specifically, the heat treatment temperature can be 900℃, 1000℃, 1100℃, 1200℃, 1250℃, 1300℃, 1400℃ or 1450℃; the heat treatment time can be 3h, 5h, 8h, 10h, 12h, 15h or 20h.
[0049] In some embodiments, the vacuum pressure of the vacuum device is 10~10 -3 Pa. Specifically, the vacuum levels are 3 Pa, 1 Pa, 0.5 Pa, and 10 Pa. -1 Pa or 10 -2 Pa.
[0050] In some embodiments, the carbon source in step S2 is selected from one or more of the group consisting of acetylene, methane, ethane, propane, butane, ethylene, propylene, butene, methanol, ethanol, propanol, and benzene.
[0051] In some embodiments, the carbon source deposition temperature in step S2 is 600~1100℃, the isothermal time is 0.5~20h, and the carbon source introduction rate is 0.5~50L / min. Specifically, the carbon deposition temperature can be 600℃, 700℃, 800℃, 850℃, or 900℃; the carbon deposition treatment time can be 0.5h, 1h, 2h, 3h, 5h, or 6h; and the carbon source introduction rate can be 1L / min, 2L / min, 3L / min, 5L / min, 10L / min, or 20L / min.
[0052] In some embodiments, the rare earth oxide in step S3 includes at least one of Y2O3, La2O3, CeO2, Nd2O3, and Sm2O3.
[0053] In some embodiments, the mass ratio of the rare earth oxide to the core is 1:(10~500), specifically, the mass ratio of the rare earth oxide to the core is 1:10, 1:20, 1:25, 1:50, 1:100 or 1:200.
[0054] In some embodiments, the rare earth oxide coating on the core surface in step S3 includes a solid-phase coating method; the solid-phase coating includes: mixing rare earth oxides with the core solid phase, placing the mixture in a heat treatment device, and sintering it under a protective atmosphere to obtain a silicon anode material with rare earth oxides coated on the core surface.
[0055] In some embodiments, the mixing of the core and rare earth oxides in step S3 further includes a liquid phase coating method; the liquid phase coating includes: uniformly dispersing the rare earth oxides in a solvent to obtain a mixed solution; adding the core to the mixed solution and mixing uniformly to obtain a core viscous material uniformly coated with rare earth oxides; drying the viscous material and placing it in a heat treatment device for sintering under a protective atmosphere to obtain a silicon anode material with rare earth oxides coated on the surface of the core.
[0056] In some embodiments, the solvent is anhydrous ethanol, ethylene glycol, acetone, industrial alcohol, or deionized water; the mass ratio of the rare earth oxide to the solvent is 1:(10~1000). Specifically, the mass ratio of the rare earth oxide to the solvent is 1:50, 1:100, 1:200, 1:500, or 1:1000.
[0057] In some embodiments, the sintering temperature is 600~1100℃, and the sintering time is 0.5~10h. Specifically, the sintering temperature can be 600℃, 650℃, 700℃, 800℃ or 900℃; the sintering time can be 0.5h, 1h, 2h, 3h, 5h or 6h.
[0058] In some embodiments, the protective atmosphere is selected from one or more of the group consisting of nitrogen, argon, helium, neon, and krypton.
[0059] In another aspect, the present invention provides a lithium-ion battery comprising the silicon anode material described above or the silicon anode material prepared by the above preparation method.
[0060] The present invention will be further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods, performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Unless otherwise specified, the materials, reagents, etc., used in the following embodiments are commercially available.
[0061] Example 1 Step S1: Place 1.2 kg of silicon powder into the high-temperature sublimation chamber of the vacuum furnace, and add 1 kg of porous carbon material with a particle size Dv50 of 7 μm (specific surface area 1873 m²). 2 / g, pore volume is 0.79cm 3 / g) is placed in the cooling deposition chamber of a vacuum device and evacuated to 10. -1 Pa then begins to heat up to 1450℃ and holds the temperature for 10 hours, causing the silicon-based material to sublimate into silicon vapor, which is then deposited into the pores and surface of the porous carbon to prepare the core precursor. Step S2: 2 kg of the core precursor prepared in step S1 was placed in a rotary kiln and heated to 850 °C under nitrogen protection. Acetylene was introduced (at a rate of 3 L / min) for vapor deposition for 2 h. After cooling, the core was obtained (core particle size Dv50 was 7.6 μm, specific surface area was 5.1 μm). 2 / g, pore volume is 0.009cm 3 / g); Step S3: Mix 2kg of core and 20g of rare earth oxide Y2O3 evenly in a mixer, place in a box furnace, and sinter at 800℃ for 2 hours under nitrogen protection. After cooling, the silicon anode material coated with Y2O3 is obtained.
[0062] Example 2 The difference from Example 1 is that in step S1, 1 kg of silicon powder and 1 kg of silicon dioxide are placed in the high-temperature sublimation chamber of the vacuum furnace, and 1 kg of porous carbon material with a particle size Dv50 of 7 μm is placed in the cooling deposition chamber of the vacuum equipment, and the vacuum is evacuated to 10 °C. -1 Pa then begins to heat up to 1250°C and holds the temperature for 10 hours, causing the silicon-based material to sublimate into silicon vapor and deposit into the pores and surface of the carbon framework, thus preparing the core precursor; the remaining steps are the same as in Example 1.
[0063] Example 3 The difference from Example 1 is that in step S1, 1 kg of silicon powder is placed into the high-temperature sublimation chamber of the vacuum furnace, and the remaining steps are the same as in Example 1.
[0064] Example 4 The difference from Example 1 is that in step S1, the temperature is raised to 1450°C and held at that temperature for 15 hours, while the remaining steps are the same as in Example 1.
[0065] Example 5 The difference from Example 1 is that in step S3, 2 kg of core and 20 g of rare earth oxide La2O3 are mixed evenly, placed in a box furnace, heated to 800°C for 2 h under nitrogen protection, and then cooled to obtain La2O3-coated silicon anode material. The remaining steps are the same as in Example 1.
[0066] Example 6 The difference from Example 1 is that in step S3, 2 kg of kernels are mixed with 30 g of rare earth oxide Y2O3 until homogeneous, and the remaining steps are the same as in Example 1.
[0067] Example 7 The difference from Example 1 is as follows: In step S3, 20g of rare earth oxide La2O3 is uniformly dispersed in 1000g of ethanol solution and stirred to obtain a mixed solution; 500g of core is added to the mixed solution and mixed evenly to obtain a core viscous material uniformly coated with rare earth oxide; the viscous material is dried and placed in an oven for drying; the dried mixture is placed in a box furnace and sintered at 800℃ for 2 hours under nitrogen protection; after cooling, a silicon anode material coated with La2O3 is obtained; the remaining steps are the same as in Example 1.
[0068] Comparative Example 1 The difference from Example 1 is that step S3 was not performed.
[0069] Comparative Example 2 The difference from Example 1 is that step S2 was not performed.
[0070] Table 1 Performance test results of materials prepared in different embodiments and comparative examples
[0071] As can be seen from the data in Table 1, compared with Comparative Example 1, the silicon anode materials prepared in Examples 1-7 have smaller specific surface area, pore volume, and lower resistivity. This indicates that the rare earth coating layer can reduce the specific surface area and resistance of the material, which is beneficial to improving the conductivity of the material, reducing the side reactions generated on the surface of the material during cycling, and improving the cycling performance of the material.
[0072] Comparing the data of Example 1 and Comparative Example 1, it can be seen that the silicon anode material without rare earth coating has a higher specific surface area and resistivity, indicating that the rare earth coating layer can reduce the specific surface area and resistivity, reduce the interface resistance, and improve the electronic conduction, which is conducive to improving the conductivity of the material.
[0073] Comparing the data from Example 1 and Comparative Example 2, it can be seen that the specific surface area and resistivity of the uncoated silicon anode material are slightly higher, but lower than those of Comparative Example 1, indicating that the carbon coating layer has the effect of reducing the specific surface area and improving conductivity.
[0074] Performance testing: (1) The pore volume, pore size and specific surface area of the carbon skeleton and core, as well as the specific surface area of the silicon anode material, were measured by using a fully automatic specific surface area and pore size analyzer (Autosorb-iQ, USA) and fitting analysis by DFT model.
[0075] (2) The particle size Dv50 of the carbon skeleton and silicon anode material was measured using a laser particle size analyzer (Malvin Panaco, 3000).
[0076] (3) The resistivity of silicon anode material was measured by using a resistivity tester (model) and the four-probe method to test the resistivity of powder at a pressure point of 8MPa.
[0077] (4) The silicon anode material slices were tested using a focused ion beam scanning electron microscope (FIB-SEM, Thermo Fisher Scientific, Scois2) to measure the thickness of the carbon coating layer and the rare earth oxide coating layer.
[0078] (5) The rare earth element content in the silicon anode material was measured by an inductively coupled plasma optical emission spectrometer (Agilent, 5800 ICP-OES), and the carbon element content in the silicon anode material was measured by a carbon-sulfur analyzer (Record, CS844, USA). The silicon content was tested by thermogravimetric analysis. The temperature was raised to 1100℃ in an air atmosphere, and the content was calculated according to the formula Si (wt%)=100*[M1100*[28 / (28+(16*2)] / M0]. M1100 is the mass at 1100℃, and M0 is the initial mass.
[0079] (6) Electrochemical testing: Silicon anode material, conductive carbon black, and binder LA133 were mixed in a ratio of 8:1:1 to form a slurry, which was then uniformly coated onto copper foil. After drying, the slurry was prepared into a negative electrode sheet, which was then assembled with the counter electrode lithium sheet, separator, and electrolyte to form a coin cell. Its electrochemical performance was tested on the Xinwei Battery Test Cabinet. The charge-discharge regime was as follows: the battery was left to stand for 10 hours, discharged at 0.1C to 0.005V, then discharged at 0.05C to 0.005V, and then charged at 0.1C to 1.5V.
[0080] (7) Processing performance: The gas production was tested for 7 days at 60℃. 40 mL of the slurry in (6) was sealed with aluminum-plastic film and the gas production was tested every 24 hours using the Archimedes water displacement method.
[0081] Table 2. Application effect test of materials prepared in different embodiments and comparative examples
[0082] As can be seen from the data in Table 2, compared with Comparative Example 1, the silicon anode materials prepared in Examples 1-7 have higher initial stock efficiency and capacity retention, and no gas is generated after 7 days. This indicates that the rare earth coating layer is beneficial to improve the initial efficiency, improve the material processing performance, reduce material expansion, and improve the material cycle stability.
[0083] Comparing the data of Example 1 and Comparative Example 1, it can be seen that the material without rare earth coating has a lower initial coulombic efficiency, a lower cycle retention rate, and poorer processing performance. This indicates that the rare earth coating is beneficial to improving the stability of the slurry during the mixing process, reducing expansion, and improving the cycle.
[0084] Comparing the data of Example 1 and Comparative Example 2, it can be seen that the material without carbon coating has a lower initial coulombic efficiency and a slightly lower cycle retention rate, but its processing performance is similar to that of Example 1 and is improved compared to Comparative Example 1. This indicates that carbon coating can improve initial efficiency and cycle performance, but rare earth coating can effectively improve processing performance and increase conductivity.
[0085] The present invention has been described in detail above. For those skilled in the art, the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. Although specific embodiments have been given, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein. Some of the essential features can be applied within the scope of the following appended claims.
Claims
1. A silicon anode material, comprising a core and an oxide coating layer covering the surface of the core; in, The core includes a carbon skeleton, silicon-based material deposited inside and on the surface of the carbon skeleton channels, and a carbon coating layer covering the surface of the carbon skeleton. The oxide coating layer is rare earth M. x O y The coating layer, M is selected from one or more rare earth elements La, Y, Ce, Nd and Sm, and x:y=(1~2):(1~3).
2. The silicon anode material according to claim 1, characterized in that: The specific surface area of the core is 0.5~1000m². 2 / g, pore volume 0.001~0.8cm 3 / g, with a particle size Dv50 of 0.5~50μm; And / or, the thickness of the carbon coating layer is 0.5~80 nm; And / or, the thickness of the oxide coating layer is 0.5~100nm.
3. The silicon anode material according to claim 1 or 2, characterized in that: The carbon framework is selected from one or more of porous carbon, hard carbon, mesophase carbon microspheres, and graphite; And / or, the specific surface area of the carbon skeleton is 2~2500 m². 2 / g, pore volume 0.01~1.5cm 3 / g, wherein the particle size Dv50 of the carbon skeleton is 0.3~40μm; And / or, the silicon-based material is selected from one or more of silicon, silicon suboxide, and silicon dioxide, wherein the silicon includes at least one of crystalline silicon and amorphous silicon.
4. The silicon anode material according to claim 1, characterized in that: The silicon anode material has a particle size Dv50 of 0.5~50 μm, a specific surface area of 0.2~50 m² / g, and a total pore volume of 0.0001~0.2 cm³. 3 / g; And / or, the silicon anode material contains 5-80 wt% silicon, 10-90 wt% carbon, and 0.05-5 wt% rare earth elements.
5. The method for preparing the silicon anode material according to any one of claims 1-4, characterized in that: Includes the following steps: S1. Place the silicon-based material into the high-temperature sublimation chamber of the vacuum equipment, place the carbon skeleton material in the cooling deposition chamber of the vacuum equipment, and heat the silicon-based material at high temperature to sublimate it and deposit it into the pores and surface of the carbon skeleton material to prepare the core precursor. S2. Place the core precursor prepared in step S1 in a heat treatment device, and perform vapor deposition by introducing a carbon source in a protective atmosphere to prepare the core. S3. Coat the core surface obtained in step S2 with rare earth oxides to prepare the silicon anode material.
6. The preparation method according to claim 5, characterized in that: In step S1, the mass ratio of the silicon-based material to the carbon framework material is 1:(0.2~5); And / or, in step S1, the heat treatment temperature of the high-temperature sublimation chamber is 800~1600℃; the heat treatment time is 2~30h; and the vacuum pressure of the vacuum equipment is 10~10 -3 Pa.
7. The preparation method according to claim 5, characterized in that: In step S2, the carbon source is selected from one or more of acetylene, methane, ethane, propane, butane, ethylene, propylene, butene, methanol, ethanol, propanol, and benzene. And / or, in step S2, the carbon source is introduced at a rate of 0.5~50 L / min; And / or, in step S2, the temperature of the carbon source deposition is 600~1100℃, and the isothermal time is 0.5~20h.
8. The preparation method according to claim 5, characterized in that: In step S3, the rare earth oxide is selected from at least one of Y2O3, La2O3, CeO2, Nd2O3, and Sm2O3; And / or, in step S3, the mass ratio of the rare earth oxide to the core is 1:(10~500).
9. The preparation method according to claim 5, characterized in that: In step S3, rare earth oxides are coated onto the core surface using a solid-phase coating method. The solid-phase coating method specifically includes the following steps: mixing rare earth oxides with the core solid phase, then placing the mixture in a heat treatment device and sintering it under a protective atmosphere to obtain a silicon anode material with rare earth oxides coated on the core surface.
10. The preparation method according to claim 5, characterized in that: In step S3, rare earth oxides are coated onto the core surface using a liquid phase coating method. The liquid phase coating method specifically includes the following steps: uniformly dispersing rare earth oxides in a solvent to obtain a mixed solution; then mixing the core with the mixed solution to obtain a core viscous material uniformly coated with rare earth oxides; finally drying the viscous material and placing it in a heat treatment device for sintering under a protective atmosphere to obtain a silicon anode material with rare earth oxides coated on the surface of the core. The solvent is anhydrous ethanol, ethylene glycol, acetone, industrial alcohol, or deionized water; the mass ratio of the rare earth oxide to the solvent is 1:(10~1000).
11. The preparation method according to claim 9 or 10, characterized in that: The sintering temperature is 600~1100℃, and the sintering time is 0.5~10h; And / or, the protective atmosphere is selected from one or more of nitrogen, argon, helium, neon and krypton.
12. A lithium-ion battery, characterized in that, The silicon anode material includes any one of claims 1 to 4 or the silicon anode material prepared by the method described in any one of claims 5 to 11.