Silicon-based negative electrode material, preparation method thereof and lithium ion battery

Abstract

The application provides a high-performance silicon-based negative electrode material, a preparation method and a lithium ion battery. x The preparation method comprises the following steps: S1, mixing SiO x with a carbon material and a doping source, washing and drying to obtain a mixed precursor; S2, performing pre-magnesium treatment on the mixed precursor obtained in S1 to obtain a silicon-based magnesium compound material; S3, performing grinding on the silicon-based magnesium compound material in S2, and then performing first carbon coating to obtain a silicon-based magnesium compound material coated with carbon for the first time; S4, performing pre-lithiation treatment on the silicon-based magnesium compound material coated with carbon for the first time in S3 to obtain a silicon-based lithium-magnesium negative electrode material; and S5, performing second carbon coating on the silicon-based lithium-magnesium negative electrode material in S4 to obtain a silicon-based lithium-magnesium negative electrode material coated with carbon for the second time, namely the silicon-based negative electrode material. The application can improve the first coulomb efficiency, relieve the problem of rate attenuation and prolong the cycle life by means of two-step pretreatment combined with two-step carbon coating.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material technology, specifically relating to a silicon-based anode material, its preparation method, and a lithium-ion battery. Background Technology

[0002] As a crucial component of lithium-ion batteries, the anode's performance significantly impacts the overall battery specifications, requiring materials with high specific capacity and excellent cycle performance. Although silicon-based materials such as silicon suboxide (SiO2) are used... x Lithium-ion batteries are popular due to their high theoretical specific capacity, abundant reserves, and low cost. However, silicon-based materials have poor conductivity, and the significant volume expansion during charging and discharging generates substantial mechanical stress. This stress causes the active material to pulverize and lose contact with the current collector, leading to a rapid decay of the electrode's reversible capacity. Furthermore, it destabilizes the solid electrolyte interphase (SEI) film, and the continuous formation and destruction of the SEI film further depletes lithium ions. These factors result in a significant decrease in the initial coulombic efficiency and poor cycle stability of lithium-ion batteries, limiting their practical applications.

[0003] To improve the initial coulombic efficiency and cycle stability of silicon suboxide, researchers have pre-magnesiated and pre-lithiated silicon suboxide. Chinese patent CN 111342030 B discloses a multi-element composite lithium-ion battery anode material and its preparation method. The multi-element composite lithium-ion battery anode materials obtained through two different preparation methods improve the initial coulombic efficiency and cycle performance to some extent. However, the direct contact between the pre-lithiated material surface and the electrolyte may lead to a decrease in later cycle performance. Chinese patent CN 116565170 A provides a silicon-based anode material and its preparation method. This material includes a core, a first coating layer, and a second coating layer, wherein the first coating layer is located between the core and the second coating layer; the core includes Si and silicon oxide compounds; the first coating layer has a porous structure and includes Si and magnesium silicon oxide compounds; the second coating layer includes an amorphous carbon layer. Although this scheme has a low lithium intercalation expansion rate, its initial coulombic efficiency is not high. Chinese patent CN116799182 A discloses a process technology for fluoride-modified coated pre-lithium- and pre-magnesium-based silicon-oxygen composite anode materials. The process involves a pre-lithiation and pre-magnesiumization process followed by a carbon one-step composite process, and then a fluorination reaction. Through multiple calcination treatments, a fluoride-modified coated pre-lithium- and pre-magnesium-based silicon-oxygen composite anode material is obtained. Although this effectively improves the initial coulombic efficiency and electronic conductivity, the cycle stability is poor and the subsequent processing is complex.

[0004] Therefore, a new preparation technology is needed to simultaneously improve the first coulombic efficiency and cycle performance of silicon-based anode materials. Summary of the Invention

[0005] To address the problems of low initial coulombic efficiency, rapid rate performance degradation, and poor cycle performance of silicon-based anode materials in existing technologies, this invention provides a high-performance silicon-based anode material, its preparation method, and a lithium-ion battery. By combining a two-step pretreatment with a two-step carbon coating method, the invention aims to improve initial coulombic efficiency, alleviate rate performance degradation, and extend cycle life.

[0006] This invention is achieved through the following technical solution: A method for preparing a silicon-based anode material includes: S1, SiO x The mixture is mixed with carbon materials and dopant sources, and then washed and dried to obtain a mixed precursor. S2, the mixed precursor obtained in S1 is pre-magnesized to obtain silicon-based magnesium compound material; S3, grind the silicon-based magnesium compound material of S2, and then perform the first carbon coating to obtain a silicon-based magnesium compound material with one carbon coating; S4, the silicon-based magnesium compound material with primary carbon coating in S3 is pre-lithiated to obtain silicon-based lithium magnesium anode material; S5, the silicon-based lithium magnesium anode material of S4 is subjected to a second carbon coating to obtain a silicon-based lithium magnesium anode material with secondary carbon coating, namely the silicon-based anode material.

[0007] Preferably, in S1, the doping source includes a metal doping source and / or a non-metal doping source; wherein the doping element in the metal doping source is one or more of Al, Na, Ca, Ti, Mn, Co, Ni, Cu, Zn, Zr, Mo, Ge and Sn; and the doping element in the non-metal doping source is one or more of B, N, P, S, C and Se.

[0008] Preferably, in S2, the pre-magnesification treatment is performed using a solid-state method, specifically: the mixed precursor obtained in S1 is mixed with a magnesium source and calcined to obtain a silicon-based magnesium compound material; wherein, based on the mass of magnesium, the magnesium source accounts for a certain percentage of SiO₂. x 1% to 8% of the quality.

[0009] Furthermore, the calcination temperature is 500~1000℃, and the calcination time is 1~12h.

[0010] Preferably, in S3, the first carbon coating method is solid-phase carbon coating, and the carbon coating temperature is 700~1100℃.

[0011] Preferably, in S4, the pre-lithiation treatment is a solid-state method, specifically: the silicon-based magnesium compound material with primary carbon coating in S3 is mixed with a lithium source and calcined to obtain a silicon-based lithium magnesium anode material; wherein, based on the mass of lithium element, the lithium source accounts for a certain percentage of SiO₂. xQuality 1%~12%.

[0012] Furthermore, the calcination temperature is 600~1200℃, and the calcination time is 1~12h.

[0013] Preferably, in S5, the second carbon coating is performed by gas phase coating, and the carbon coating temperature is 700~1200℃.

[0014] This invention provides a silicon-based anode material prepared by the method described above.

[0015] The present invention also provides a lithium-ion battery, wherein the negative electrode of the lithium-ion battery includes the silicon-based negative electrode material as described above.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The pre-magnesification and pre-lithiation techniques in this invention effectively replenish Li and Mg, improving the initial coulombic efficiency of the battery. Simultaneously, the formed inert metal silicate complex (lithium silicate and magnesium silicate) also mitigates volume expansion, improving cycle stability. Furthermore, the first carbon coating in the process forms a buffer carbon layer within the material, providing space for lithium intercalation expansion; the second carbon coating forms a carbon coating layer on the surface of the silicon-based lithium-magnesium anode material, enhancing the material's structural stability and acting as a physical barrier to reduce direct contact between the silicon-based material and the electrolyte, thereby reducing potential side reactions and improving the cycle life of the lithium battery. This invention also creates defects through doping elements, improving the material's electron and ion transport capabilities while reserving space for volume expansion. Therefore, this invention, through two-step pretreatment combined with two layers of carbon coating, not only improves the initial coulombic efficiency and cycle stability of the battery but also enhances the structural stability of the material to a certain extent. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 The image shows the XRD pattern of the silicon-based anode material prepared in Example 1. Detailed Implementation

[0019] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0020] It should be noted that the process equipment or devices not specifically noted in the following embodiments are all conventional equipment or devices in the art.

[0021] It should be noted that the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products, or devices. Moreover, unless otherwise specified, the numbers of each method step are only convenient tools for identifying each method step, rather than limiting the arrangement order of each method step or the scope in which the present invention can be implemented. The change or adjustment of their relative relationship, without substantial change in technical content, should also be regarded as the scope in which the present invention can be implemented.

[0022] The present invention prepares a silicon-based anode material by a method combining two-step pretreatment and two-step carbon coating. The specific preparation method includes the following steps: S1, Mix SiO x with a carbon material and a doping source, wash and dry to obtain a mixed precursor; S2, Perform pre-magnesiation treatment on the mixed precursor obtained in S1 to obtain a silicon-based magnesium compound material; S3, Grind the silicon-based magnesium compound material in S2, and then perform the first carbon coating to obtain a silicon-based magnesium compound material with a first carbon coating; S4, Perform pre-lithiation treatment on the silicon-based magnesium compound material with a first carbon coating in S3 to obtain a silicon-based lithium-magnesium anode material; S5, Perform the second carbon coating on the silicon-based lithium-magnesium anode material in S4 to obtain a silicon-based lithium-magnesium anode material with a second carbon coating, that is, the silicon-based anode material.

[0023] Specifically, S1 of the method of the present invention is as follows: First, perform screening treatment on the crushed SiO x , and the screened SiO x is uniformly mixed with a carbon material, and then the obtained mixture is uniformly mixed with a doping source in a solvent, washed and dried to obtain a mixed precursor. The range of x in the SiO x is 0 < x < 2, preferably 0.6 < x < 1.5; the screened SiO xThe particle size is 1~25 μm, preferably 5~10 μm.

[0024] In this invention, the carbon material can be one or more of hard carbon, graphite, graphene, and carbon fiber; the SiO2... x In mixtures of SiO and carbon materials x The mass content of the dopant is 10%~88%; the doping source includes a metal doping source and / or a non-metal doping source; wherein, the doping element in the metal doping source is one or more of Al, Ca, Ti, Mn, Co, Ni, Cu, Zn, Zr, Mo, Ge and Sn; the doping element in the non-metal doping source is one or more of B, N, P, S, C and Se, and the mass of the doping source accounts for 10%~88% of the mass of the SiO2. x The content is 0.1% to 15% of the mass, preferably 0.5% to 8%.

[0025] The solvent is either ethanol or propanol. The method for uniformly mixing the resulting mixture with the dopant source in the solvent can be mechanical stirring and / or ultrasonic dispersion. Mechanical stirring can be used alone, ultrasonic dispersion can be used alone, or mechanical stirring can be performed first, followed by ultrasonic dispersion. The mechanical stirring speed is 200~1000 r / min, preferably 300~700 r / min; the stirring time is 2~12 h, preferably 3~8 h; and the ultrasonic dispersion time is 1~6 h, preferably 2~4 h.

[0026] In step S2 of the above method of the present invention, the pre-magnesification treatment adopts a solid-state method, specifically: the mixed precursor obtained in S1 is mixed with a magnesium source and calcined to obtain a silicon-based magnesium compound material; the magnesium source is one of metallic magnesium, magnesium alloy, magnesium carbonate, magnesium sulfate, and magnesium hydroxide; based on the mass of magnesium element, the magnesium source accounts for a certain percentage of SiO₂. x The mass is 1% to 8%, preferably 2.8% to 6%; the calcination temperature is 500 to 1000℃, preferably 650 to 800℃, and the calcination time is 1 to 12 hours, preferably 2 to 6 hours.

[0027] In S3 of the above method of the present invention, the grinding includes coarse grinding and ultrafine grinding, mainly physical grinding, but not limited to physical grinding.

[0028] In S3 of the above method of the present invention, the first carbon coating method can be solid phase carbon coating, gas phase carbon coating or liquid phase carbon coating, preferably solid phase carbon coating, the carbon source is one of asphalt and resin, and the carbon coating temperature is 700~1100℃, preferably 850~1000℃.

[0029] In step S4 of the above method of the present invention, the prelithiation treatment is a solid-phase method and a liquid-phase prelithiation, preferably the solid-phase method. Specifically: the silicon-based magnesium compound material with primary carbon coating obtained in S3 is mixed with a lithium source, and then calcined to obtain a silicon-based lithium-magnesium negative electrode material; wherein, the lithium source used can be one of lithium powder, lithium sheet, lithium hydride, lithium hydroxide and lithium carbonate; calculated by the mass of lithium element, the lithium source accounts for 1% to 12% of the mass of SiO x preferably 3% to 10%; the calcination temperature is 600 to 1200 °C, preferably 750 to 900 °C, and the calcination time is 1 to 12 h, preferably 3 to 10 h.

[0030] In step S5 of the above method of the present invention, the second carbon coating method can be gas-phase carbon coating or liquid-phase carbon coating, preferably gas-phase coating, and the carbon source is one or more of methane, acetylene and propane. The temperature of carbon coating is 700 to 1200 °C, preferably 850 to 1100 °C.

[0031] In the silicon-based negative electrode material prepared by the above method of the present invention, the mass of SiO x accounts for 50% to 90% of the total mass of the silicon-based negative electrode material; the mass of the carbon material accounts for 3% to 50% of the total mass of the silicon-based negative electrode material.

[0032] The total mass of the two carbon coating layers accounts for 0.1% to 18% of the total mass of the silicon-based negative electrode material, preferably 1% to 15%.

[0033] Example 1 This example provides a preparation process and performance test of a silicon-based negative electrode material.

[0034] The specific preparation process is as follows: (1) Select SiO with a particle size of about 10 μm x (0 < x < 2). 7 g of SiO x (accounting for about 85.36% of the total mass of SiO x and carbon fiber) and 1.2 g of carbon fiber are uniformly mixed, and then the mixture and 0.2 g of Sn powder (accounting for about 2.86% of the mass of SiO x ) are uniformly mixed in ethanol, washed twice with distilled water, and dried to obtain a mixed precursor; (2) Mix the mixed precursor obtained in step (1) with 0.25 g of magnesium powder, and calcine it in an argon atmosphere. The calcination temperature is 750 °C, the heating rate is 5 °C / min, and the holding time is 4 h to obtain a silicon-based magnesium compound material; (3) After ball milling the silicon-based magnesium compound material from step (2) for 6 hours, it is dissolved in isopropanol with asphalt at a mass ratio of 15:1 and stirred for 3 hours to form a uniform slurry. Then the slurry is directly dried, placed in a tube furnace, heated to 750°C in argon and kept at that temperature for 2 hours. After cooling and discharging, the silicon-based magnesium compound material with carbon coating is obtained. (4) The silicon-based magnesium compound material with carbon coating layer from step (3) is mixed with 0.203g of lithium powder and calcined in an argon atmosphere at a calcination temperature of 750℃, a heating rate of 10℃ / min, and a holding time of 6h to obtain silicon-based lithium magnesium anode material. (5) Place the silicon-based lithium magnesium anode material from step (4) in a tube furnace, heat it to 800°C under argon conditions, introduce argon and acetylene gas in a volume ratio of 1:1 for gas phase coating, keep it at the temperature for 1 hour, turn off the acetylene gas source, and discharge the material after cooling to room temperature to obtain the silicon-based anode material with carbon coating layer.

[0035] The silicon-based anode material prepared in this embodiment was used to prepare a negative electrode sheet, and a coin cell was assembled for testing.

[0036] The preparation and testing methods for coin cell half-cells are as follows: Silicon-based anode material with a carbon coating layer, conductive additive SP, and binder are weighed at a mass ratio of 95%:2%:3%, and a slurry is prepared using a pulping machine. The slurry is then coated, dried, cut into sheets, and assembled into coin cell half-cells in a glove box. Testing is then conducted using a blue-chip testing device. The discharge cutoff voltage is 0.005V, and the charge cutoff voltage is 1.5V. The cells are discharged to 0.005V using constant current at 0.1C, 0.05C, and 0.02C, respectively, and then charged to 1.5V using constant current at 0.1C. This charge-discharge cycle is repeated twice. Discharge tests after the third cycle are all conducted at a current density of 0.1C. The test data are shown in Table 1.

[0037] Figure 1 This is the XRD pattern of the silicon-based anode material prepared in Example 1. Figure 1 As can be seen, the main components of the silicon-based anode material include Li₂SiO₃, Li₂Si₂O₅, MgSiO₃, Mg₂SiO₄, and Si. The diffraction peaks for Li₂SiO₃ are approximately at 18.5°, 26.8°, 32.8°, 38.4°, and 51.5°. The diffraction peaks for Li₂Si₂O₅ are approximately at 23.4° and 24.6°. The diffraction peaks for MgSiO₃ are approximately at 36.5° and 64.6°. The diffraction peaks for Mg₂SiO₄ are approximately at 31.0°, 33.9°, and 55.6°. The diffraction peaks for Si are approximately at 28.4° and 47.3°.

[0038] Example 2 This embodiment provides a preparation process and performance test of a silicon-based anode material.

[0039] The specific preparation process is as follows: (1)Select SiO with a particle size of about 10 μm x (0 < x < 2), mix 7 g of SiO x (accounting for about 73.68% of the total mass of SiO x and carbon fiber)and 2.5 g of carbon fiber evenly, then mix the mixture and 0.2 g of Se powder (accounting for about 2.86% of the mass of SiO) evenly in ethanol, wash it twice with distilled water, and dry it to obtain a mixed precursor; (2)Mix the mixed precursor obtained in step (1) with 0.25 g of magnesium powder, and calcine it in an argon atmosphere at a calcination temperature of 750 °C, a heating rate of 5 °C / min, and hold for 4 h to obtain a silicon-based magnesium compound material; (3)After ball-milling the silicon-based magnesium compound material in step (2) for 6 h, dissolve it in isopropanol with asphalt in a mass ratio of 15:1, stir for 3 hours to form a uniform slurry; then directly dry the slurry, place it in a tube furnace, heat it to 750 °C in argon and hold for 2 hours, and after cooling and discharging, a silicon-based magnesium compound material with a carbon coating layer is obtained; (4)Mix the silicon-based magnesium compound material with a carbon coating layer in step (3) with 0.203 g of lithium powder, and calcine it in an argon atmosphere at a calcination temperature of 750 °C, a heating rate of 10 °C / min, and hold for 6 h to obtain a silicon-based lithium-magnesium anode material; (5)Place the silicon-based lithium-magnesium anode material in step (4) in a tube furnace, heat it to 800 °C under argon conditions, introduce argon and acetylene gas in a volume ratio of 1:1 for gas-phase coating, close the acetylene gas source after holding for 1 hour, and discharge it after cooling to room temperature, thus obtaining a silicon-based anode material with a carbon coating layer.

[0040] Use the silicon-based anode material prepared in this embodiment to prepare a negative electrode sheet, and assemble a button-type half-cell and a full-cell for testing. The testing method is the same as that in Example 1. The test data is shown in Table 1.

[0041] Example 3 This embodiment provides a preparation process and performance test of a silicon-based anode material.

[0042] The specific preparation process is as follows: (1)Select SiO with a particle size of about 10 μm x (0 < x < 2), mix 7 g of SiO x (accounting for about xand 85.36% of the total mass of carbon fiber) and 1.2 g of carbon fiber were uniformly mixed, and then the mixture and 0.3 g of Sn powder (about 4.28% of the mass of SiO x were uniformly mixed in ethanol, washed twice with distilled water, and dried to obtain a mixed precursor; (2) The mixed precursor obtained in step (1) was mixed with 0.68 g of magnesium carbonate and calcined in an argon atmosphere at a calcination temperature of 750 °C, a heating rate of 5 °C / min, and held for 4 h to obtain a silicon-based magnesium compound material; (3) After ball-milling the silicon-based magnesium compound material in step (2) for 6 h, it was dissolved in isopropanol with asphalt in a mass ratio of 15:1, and stirred for 3 h to form a uniform slurry; then the slurry was directly dried, placed in a tubular furnace, heated to 750 °C in argon and held for 2 h, and after cooling and discharging, a silicon-based magnesium compound material with a carbon coating layer was obtained; (4) The silicon-based magnesium compound material with a carbon coating layer in step (3) was mixed with 0.203 g of lithium powder and calcined in an argon atmosphere at a calcination temperature of 750 °C, a heating rate of 10 °C / min, and held for 6 h to obtain a silicon-based lithium-magnesium negative electrode material; (5) The silicon-based lithium-magnesium negative electrode material in step (4) was placed in a tubular furnace, heated to 800 °C under argon conditions, and argon and acetylene gases were introduced in a volume ratio of 1:1 for gas-phase coating. After holding for 1 h, the acetylene gas source was closed, and after cooling to room temperature, the material was discharged to obtain a silicon-based negative electrode material with a carbon coating layer.

[0043] The negative electrode sheet was prepared using the silicon-based negative electrode material prepared in this example, and a button-type half-cell and a full-cell were assembled for testing. The testing method was the same as in Example 1. The test data are shown in Table 1.

[0044] Example 4 This example provides a preparation process and performance test of a silicon-based negative electrode material.

[0045] The specific preparation process is as follows: (1) Select SiO with a particle size of about 10 μm x (0 < x < 2), 7 g of SiO x (about 73.68% of the total mass of SiO x and carbon fiber) and 2.5 g of carbon fiber were uniformly mixed, and then the mixture and 0.15 g of Ge powder (about 2.14% of the mass of SiO x were uniformly mixed in ethanol, washed twice with distilled water, and dried to obtain a mixed precursor; (2) Mix the mixed precursor obtained in step (1) with 0.68 g of magnesium carbonate, and perform calcination in an argon atmosphere at a calcination temperature of 750 °C, a heating rate of 5 °C / min, and hold for 4 h to obtain a silicon-based magnesium compound material; (3) After ball-milling the silicon-based magnesium compound material in step (2) for 6 h, dissolve it in isopropanol with asphalt at a mass ratio of 15:1, and stir for 3 hours to form a uniform slurry; then directly dry the slurry, place it in a tube furnace, heat it to 750 °C in argon and hold for 2 hours, and after cooling and discharging, a silicon-based magnesium compound material with a carbon coating layer is obtained; (4) Mix the silicon-based magnesium compound material with a carbon coating layer in step (3) with 0.405 g of lithium powder, and perform calcination in an argon atmosphere at a calcination temperature of 750 °C, a heating rate of 10 °C / min, and hold for 6 h to obtain a silicon-based lithium-magnesium anode material; (5) Place the silicon-based lithium-magnesium anode material in step (4) in a tube furnace, heat it to 800 °C under argon conditions, introduce argon and acetylene gas in a volume ratio of 1:1 for gas-phase coating, close the acetylene gas source after holding for 1 hour, and discharge after cooling to room temperature to obtain a silicon-based anode material with a carbon coating layer.

[0046] Use the silicon-based anode material prepared in this example to prepare an anode electrode sheet, and assemble a button-type half-cell and a full-cell for testing. The testing method is the same as that in Example 1. The test data is shown in Table 1.

[0047] Example 5 This example provides a preparation process and performance test of a silicon-based anode material.

[0048] The specific preparation process is as follows: (1) Select SiO with a particle size of about 10 μm x (0 < x < 2), mix 7 g of SiO x (accounting for about 73.68% of the total mass of SiO x and carbon fiber) and 2.5 g of carbon fiber evenly, and then evenly mix the mixture with 0.2 g of Sn powder (accounting for about 2.86% of the mass of SiO x ), wash it twice with distilled water, and dry it to obtain a mixed precursor; (2) Mix the mixed precursor obtained in step (1) with 0.68 g of magnesium carbonate, and perform calcination in an argon atmosphere at a calcination temperature of 750 °C, a heating rate of 5 °C / min, and hold for 4 h to obtain a silicon-based magnesium compound material; (3) After ball-milling the silicon-based magnesium compound material in step (2) for 6 h, it is dissolved in isopropanol with asphalt at a mass ratio of 15:1, and stirred for 3 hours to form a homogeneous slurry; then the slurry is directly dried, placed in a tubular furnace, heated to 750 °C in argon and held for 2 hours, and after cooling and discharging, a silicon-based magnesium compound material with a carbon coating layer is obtained; (4) Mix the silicon-based magnesium compound material with a carbon coating layer in step (3) and 0.203 g of lithium powder, and calcine it in an argon atmosphere at a calcination temperature of 750 °C, a heating rate of 10 °C / min, and hold for 6 h to obtain a silicon-based lithium-magnesium anode material; (5) Place the silicon-based lithium-magnesium anode material in step (4) in a tubular furnace, heat it to 800 °C under argon conditions, introduce argon and acetylene gas at a volume ratio of 1:1 for gas-phase coating, close the acetylene gas source after holding for 1 hour, cool to room temperature and discharge to obtain a silicon-based anode material with a carbon coating layer.

[0049] Use the silicon-based anode material prepared in this example to prepare an anode electrode sheet, and assemble a coin-type half-cell and a full-cell for testing. The testing method is the same as that in Example 1. The test data are shown in Table 1.

[0050] Example 6 This example provides a preparation process and performance test of a silicon-based anode material.

[0051] The specific preparation process is as follows: (1) Select SiO with a particle size of about 10 μm x (0 < x < 2), uniformly mix 7 g of SiO x (accounting for about 73.68% of the total mass of SiO x and carbon fiber) and 2.5 g of carbon fiber, and then uniformly mix it with 0.2 g of Sn powder (accounting for about 2.86% of the mass of SiO x ) in ethanol, wash it twice with distilled water, and dry it to obtain a mixed precursor; (2) Mix the mixed precursor obtained in step (1) with 0.42 g of magnesium powder, and calcine it in an argon atmosphere at a calcination temperature of 750 °C, a heating rate of 5 °C / min, and hold for 4 h to obtain a silicon-based magnesium compound material; (3) After ball-milling the silicon-based magnesium compound material in step (2) for 6 h, dissolve 7 g of the silicon-based magnesium compound material and asphalt in isopropanol at a mass ratio of 15:1, and stir for 3 hours to form a homogeneous slurry; then the slurry is directly dried, placed in a tubular furnace, heated to 750 °C in argon and held for 2 hours, and after cooling and discharging, a silicon-based magnesium compound material with a carbon coating layer is obtained; (4) Mix the silicon-based magnesium compound material with a carbon coating layer obtained in step (3) and 0.706 g of lithium powder, and conduct calcination in an argon atmosphere at a calcination temperature of 750 °C, a heating rate of 10 °C / min, and hold for 6 h to obtain a silicon-based lithium magnesium anode material; (5) Place the silicon-based lithium magnesium anode material in step (4) in a tube furnace, heat it to 800 °C under argon conditions, introduce argon and acetylene gases in a volume ratio of 1:1 for gas-phase coating, close the acetylene gas source after holding for 1 hour, and discharge the material after cooling to room temperature to obtain a silicon-based anode material with a carbon coating layer.

[0052] Prepare an anode electrode sheet using the silicon-based anode material prepared in this example, and assemble a button half-cell and a full-cell for testing. The testing method is the same as that in Example 1. The test data are shown in Table 1.

[0053] Comparative Example 1 (without pre-magnesium treatment) This comparative example provides a preparation process and performance test of a silicon-based anode material.

[0054] The specific preparation process is as follows: (1) Select SiO with a particle size of about 10 μm x (0 < x < 2), uniformly mix 7 g of SiO x (accounting for about 85.36% of the total mass of SiO x and carbon fiber) and 1.2 g of carbon fiber, then uniformly mix the mixture and 0.2 g of Sn powder (accounting for about 2.86% of the mass of SiO x ), wash it twice with distilled water, and dry it to obtain a mixed precursor; (2) After ball-milling the mixed precursor material in step (1) for 6 h, dissolve it in isopropanol with asphalt in a mass ratio of 15:1, stir for 3 h to form a uniform slurry; then directly dry the slurry, place it in a tube furnace, heat it to 750 °C in argon and hold for 2 h, and discharge the material after cooling to obtain a mixed precursor with a carbon coating layer; (3) Mix the mixed precursor with a carbon coating layer obtained in step (2) and 0.203 g of lithium powder, and conduct calcination in an argon atmosphere at a calcination temperature of 750 °C, a heating rate of 10 °C / min, and hold for 6 h to obtain a pre-lithiated silicon-based anode material; (3) Place the pre-lithiated silicon-based anode material in step (3) in a tube furnace, heat it to 800 °C under argon conditions, introduce argon and acetylene gases in a volume ratio of 1:1 for gas-phase coating, close the acetylene gas source after holding for 1 hour, and discharge the material after cooling to room temperature to obtain a silicon-based anode material with a carbon coating layer.

[0055] The negative electrode sheet was prepared using the silicon-based negative electrode material prepared in this comparative example, and a button-type half-cell and a full cell were assembled for testing. The testing method was the same as that in Example 1. The test data are shown in Table 1.

[0056] Comparative Example 2 (without the first carbon coating) This comparative example provides a preparation process and performance test of a silicon-based negative electrode material.

[0057] The specific preparation process is as follows: (1) SiO with a particle size of about 10 μm was selected x (0 < x < 2), and 7 g of SiO x (accounting for about 85.36% of the total mass of SiO x and carbon fiber) and 1.2 g of carbon fiber were uniformly mixed. Then, the mixture and 0.2 g of Sn powder (accounting for about 2.86% of the mass of SiO x ) were uniformly mixed in ethanol, washed twice with distilled water, and dried to obtain a mixed precursor; (2) The mixed precursor obtained in step (1) was mixed with 0.25 g of magnesium powder and calcined in an argon atmosphere at a calcination temperature of 750 °C, a heating rate of 5 °C / min, and held for 4 h to obtain a silicon-based magnesium compound material; (3) The silicon-based magnesium compound material in step (2) was mixed with 0.203 g of lithium powder and calcined in an argon atmosphere at a calcination temperature of 750 °C, a heating rate of 10 °C / min, and held for 6 h to obtain a silicon-based lithium magnesium negative electrode material; (4) The silicon-based lithium magnesium negative electrode material in step (3) was placed in a tube furnace, heated to 800 °C under argon conditions, and argon and acetylene gases were introduced in a volume ratio of 1:1 for gas-phase coating. After holding for 1 hour, the acetylene gas source was closed, and the material was discharged after cooling to room temperature to obtain a silicon-based negative electrode material with a carbon coating layer.

[0058] The negative electrode sheet was prepared using the silicon-based negative electrode material prepared in this comparative example, and a button-type half-cell and a full cell were assembled for testing. The testing method was the same as that in Example 1. The test data are shown in Table 1.

[0059] Comparative Example 3 (without prelithiation treatment) This comparative example provides a preparation process and performance test of a silicon-based negative electrode material.

[0060] The specific preparation process is as follows: (1) SiO with a particle size of about 10 μm was selected x (0 < x < 2), and 7 g of SiO x (accounting for about xand 1.2 g of carbon fiber were uniformly mixed (about 85.36% of the total mass of silicon oxide and carbon fiber), and then the mixture and 0.2 g of Sn powder (about 2.86% of the mass of silicon oxide) were uniformly mixed in ethanol, washed twice with distilled water, and dried to obtain a mixed precursor; x The mixture was uniformly mixed with 0.2 g of Sn powder (about 2.86% of the mass of SiO x ) in ethanol, washed twice with distilled water, and dried to obtain a mixed precursor; (2) Mix the mixed precursor obtained in step (1) with 0.25 g of magnesium powder, and calcine it in an argon atmosphere at a calcination temperature of 750 °C, a heating rate of 5 °C / min, and hold for 4 h to obtain a silicon-based magnesium compound material; (3) After ball-milling the silicon-based magnesium compound material obtained in step (2) for 6 h, dissolve it in isopropanol with asphalt at a mass ratio of 15:1, and stir for 3 hours to form a uniform slurry; then directly dry the slurry, place it in a tube furnace, heat it to 750 °C in argon and hold for 2 hours, and after cooling and discharging, a silicon-based magnesium compound material with a carbon coating layer is obtained; (4) Place the silicon-based magnesium compound material with a carbon coating layer obtained in step (3) in a tube furnace, heat it to 800 °C under argon conditions, introduce argon and acetylene gas at a volume ratio of 1:1 for gas-phase coating, close the acetylene gas source after holding for 1 hour, and discharge after cooling to room temperature to obtain a silicon-based negative electrode material with a carbon coating layer.

[0061] The negative electrode sheet was prepared using the silicon-based negative electrode material prepared in this comparative example, and a button-type half-cell and a full-cell were assembled for testing. The testing method was the same as that in Example 1. The test data are shown in Table 1.

[0062] Comparative Example 4 (without the second carbon coating) This comparative example provides a preparation process and performance test of a silicon-based negative electrode material.

[0063] The specific preparation process is as follows: (1) Select SiO with a particle size of about 10 μm x (0 < x < 2), mix 7 g of SiO x (about 85.36% of the total mass of SiO x and carbon fiber) and 1.2 g of carbon fiber uniformly, and then mix the mixture and 0.2 g of Sn powder (about 2.86% of the mass of SiO x in ethanol, wash twice with distilled water, and dry to obtain a mixed precursor; (2) Mix the mixed precursor obtained in step (1) with 0.25 g of magnesium powder, and calcine it in an argon atmosphere at a calcination temperature of 750 °C, a heating rate of 5 °C / min, and hold for 4 h to obtain a silicon-based magnesium compound material; (3) After ball-milling the silicon-based magnesium compound material in step (2) for 6 h, it is dissolved in isopropanol with asphalt in a mass ratio of 15:1, and stirred for 3 h to form a uniform slurry; then the slurry is directly dried, placed in a tubular furnace, heated to 750 °C in argon and kept warm for 2 h, and after cooling and discharging, a silicon-based magnesium compound material with a carbon coating layer is obtained; (4) Mix the silicon-based magnesium compound material with a carbon coating layer in step (3) and 0.203 g of lithium powder, and calcine it in an argon atmosphere. The calcination temperature is 750 °C, the heating rate is 10 °C / min, and keep warm for 6 h to obtain a silicon-based lithium-magnesium negative electrode material, that is, a silicon-based negative electrode material.

[0064] Use the silicon-based negative electrode material prepared in this comparative example to prepare a negative electrode sheet, and assemble a button-type half-cell and a full-cell for testing. The testing method is the same as that in Example 1. The test data are shown in Table 1.

[0065] Comparative Example 5 (without doping) This example provides a preparation process and performance test of a silicon-based negative electrode material.

[0066] The specific preparation process is as follows: (1) Select SiO with a particle size of about 10 μm x (0 < x < 2), mix 7 g of SiO x (accounting for about 85.36% of the total mass of SiO x and carbon fiber) and 1.2 g of carbon fiber uniformly to obtain a mixed precursor; (2) Mix the mixed precursor obtained in step (1) and 0.25 g of magnesium powder, and calcine it in an argon atmosphere. The calcination temperature is 750 °C, the heating rate is 5 °C / min, and keep warm for 4 h to obtain a silicon-based magnesium compound material; (3) After ball-milling the silicon-based magnesium compound material in step (2) for 6 h, it is dissolved in isopropanol with asphalt in a mass ratio of 15:1, and stirred for 3 h to form a uniform slurry; then the slurry is directly dried, placed in a tubular furnace, heated to 750 °C in argon and kept warm for 2 h, and after cooling and discharging, a silicon-based magnesium compound material with a carbon coating layer is obtained; (4) Mix the silicon-based magnesium compound material with a carbon coating layer in step (3) and 0.203 g of lithium powder, and calcine it in an argon atmosphere. The calcination temperature is 750 °C, the heating rate is 10 °C / min, and keep warm for 6 h to obtain a silicon-based lithium-magnesium negative electrode material; (5) Place the silicon-based lithium-magnesium negative electrode material in step (4) in a tubular furnace, heat it to 800 °C under argon conditions, and introduce argon and acetylene gases in a volume ratio of 1:1 for gas-phase coating. After keeping warm for 1 h, close the acetylene gas source, cool to room temperature and then discharge to obtain a silicon-based negative electrode material with a carbon coating layer.

[0067] The silicon-based anode material prepared in this comparative example was used to fabricate anode sheets, and coin cell half-cells and full cells were assembled for testing. The testing methods were the same as in Example 1. The test data are shown in Table 1.

[0068] The battery performance data for each of the above embodiments and comparative examples are shown in Table 1 below.

[0069] Table 1 Battery performance data

[0070] As can be seen from Table 1, the silicon-based anode materials prepared in Examples 1 to 6 of the present invention all have an initial coulombic efficiency of over 90%, a capacity retention rate of over 92% after 100 cycles, and a capacity retention rate of over 85% after 300 cycles, indicating that the silicon-based anode materials prepared in the present invention have high initial coulombic efficiency and cycle stability.

[0071] Compared with Example 1, Comparative Example 1 was not pre-magnesized. The first coulombic efficiency of the silicon-based anode material obtained in Comparative Example 1 was lower than that in Example 1. This is because pre-magnesization can compensate for the irreversible lithium loss caused by the formation of the SEI film and other side reactions during the first charge, and can improve the first coulombic efficiency of the battery.

[0072] The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 did not undergo a first carbon coating. The initial coulombic efficiency of the silicon-based anode material in Comparative Example 2 was significantly lower than that in Example 1. This is because the presence of the carbon coating layer can form a buffer carbon layer in the material, providing space for lithium intercalation expansion. Compared with Example 1, Comparative Example 3 did not undergo pre-lithiation treatment. The results showed that the initial coulombic efficiency and cycle stability of the silicon-based anode material obtained in Comparative Example 3 were significantly lower than those in Example 1. This is because pre-lithiation can compensate for the lithium lost during the first charge and discharge process, thereby improving the initial coulombic efficiency of the battery. The partially formed lithium silicate structure formed by pre-lithiation has good water resistance, thus improving the cycle stability of the battery.

[0073] Compared with Example 1, Comparative Example 4 did not undergo a second carbon coating. The results showed that the cycle stability of the silicon-based anode material obtained in Comparative Example 4 was significantly lower than that in Example 1. This is because the second carbon coating can form a carbon coating layer on the surface of the silicon-based lithium magnesium anode material, which can enhance the structural stability of the material. It can also act as a physical barrier, reducing the direct contact between the silicon-based material and the electrolyte, thereby reducing possible side reactions and improving the cycle life of the lithium battery.

[0074] Compared with Example 1, Comparative Example 5 did not involve elemental doping. The results showed that the silicon-based anode material obtained in Example 1 had slightly higher cycle stability than that in Comparative Example 5. This is because doping creates some defects, improving the material's electron and ion transport capabilities, while also reserving space for volume expansion, which can improve the battery's cycle performance.

Claims

1. A method for preparing a silicon-based anode material, characterized in that, Includes the following steps: S1. Mix SiO x , carbon material and doping source in a solvent, wash and dry to obtain a mixed precursor; the range of x in the SiO x is 0 < x < 2; the carbon material is one or more of hard carbon, graphite, graphene and carbon fiber; in the mixture of SiO x and carbon material, the mass content of SiO x is 10% - 88%; the doping source includes a metal doping source and / or a non-metal doping source; wherein, the doping element in the metal doping source is one or more of Al, Ca, Ti, Mn, Co, Ni, Cu, Zn, Zr, Mo, Ge and Sn; the doping element in the non-metal doping source is one or more of B, N, P, S and Se, and the mass of the doping source accounts for 0.1% - 15% of the mass of SiO x . S2, the mixed precursor obtained in S1 is pre-magnesized to obtain silicon-based magnesium compound material; S3, grind the silicon-based magnesium compound material of S2, and then perform the first carbon coating to obtain a silicon-based magnesium compound material with one carbon coating; the first carbon coating method is solid-phase carbon coating, and the carbon coating temperature is 700~1100℃; S4, the silicon-based magnesium compound material with primary carbon coating in S3 is pre-lithiated to obtain silicon-based lithium magnesium anode material; S5, the silicon-based lithium magnesium anode material of S4 is subjected to a second carbon coating to obtain a silicon-based lithium magnesium anode material with secondary carbon coating, namely the silicon-based anode material; the second carbon coating is carried out by gas phase coating, and the carbon coating temperature is 700~1200℃.

2. The method for preparing the silicon-based anode material according to claim 1, characterized in that, In S1, the doping source includes a metal doping source; wherein the doping element in the metal doping source is Ge.

3. The method for preparing the silicon-based anode material according to claim 1, characterized in that, In S2, the pre-magnesification treatment employs a solid-state method, specifically: the mixed precursor obtained in S1 is mixed with a magnesium source and calcined to obtain a silicon-based magnesium compound material; wherein, based on the mass of magnesium element, the magnesium source accounts for a certain percentage of SiO₂. x 1% to 8% of the quality.

4. The method for preparing the silicon-based anode material according to claim 3, characterized in that, The calcination temperature is 500~1000℃, and the calcination time is 1~12h.

5. The method for preparing the silicon-based anode material according to claim 1, characterized in that, In S4, the pre-lithiation treatment is a solid-state method, specifically: the silicon-based magnesium compound material with primary carbon coating in S3 is mixed with a lithium source and calcined to obtain a silicon-based lithium-magnesium anode material; wherein, based on the mass of lithium element, the lithium source accounts for a certain percentage of SiO₂. x Quality 1%~12%.

6. The method for preparing the silicon-based anode material according to claim 5, characterized in that, The calcination temperature is 600~1200℃, and the calcination time is 1~12h.

7. A silicon-based anode material obtained by the preparation method according to any one of claims 1 to 6.

8. A lithium-ion battery, characterized in that, The negative electrode of the lithium-ion battery includes the silicon-based negative electrode material as described in claim 7.

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