Silicon anode material, method for manufacturing the same, and use

Abstract

This invention relates to a silicon anode material, a method for manufacturing the same, and its use, and belongs to the technical field of secondary batteries. The silicon anode material comprises a porous γ-phase lithium methaluminate and a carbon coating layer, wherein a carbon layer and a silicon material layer are sequentially deposited in the pores of the porous γ-phase lithium methaluminate, and the carbon coating layer covers the surface of the porous γ-phase lithium methaluminate on which the carbon layer and the silicon material layer are deposited. The silicon anode material effectively prevents the silicon material from coming into direct contact with the electrolyte, suppresses the volume expansion of silicon during the cycle process from the material side, effectively mitigates volume changes, and stabilizes the structure of the electrode material, thereby improving the electrochemical performance of the material.

Description

[[Technical Field]]

[0001] The present invention belongs to the technical field of secondary batteries, and specifically relates to a silicon negative electrode material, a method for producing the same, and use thereof. [[Background Art]]

[0002] Secondary batteries are widely used in portable electronic devices and electric vehicles due to their advantages such as high energy density and long cycle life. Silicon materials have attracted extensive attention because of their high theoretical capacity and abundant resources, and are considered one of the ideal candidate materials for developing a new generation of negative electrode materials for secondary batteries with high specific energy and high power density. However, silicon materials have problems of low electrical conductivity and volume expansion occurring during the lithium deintercalation-intercalation cycle process, which limits the application of silicon materials in secondary battery negative electrodes.

[0003] Patent application CN111525108A discloses a method for synthesizing a carbon-coated silicon negative electrode material, wherein carbon coating improves the conductive performance of the material and suppresses the volume expansion effect of silicon-based materials during the lithium deintercalation-intercalation process. However, at present, a single carbon coating alone cannot effectively suppress volume expansion, nor can it effectively prevent erosion of the silicon material by the electrolyte, and thus cannot effectively improve battery performance.

[0004] Therefore, effectively solving the volume expansion problem of silicon negative electrode materials, avoiding erosion of silicon by the electrolyte, and improving the electrochemical performance of negative electrode materials is a technical issue that needs to be urgently resolved. [[Summary of the Invention]]

[0005] An object of the present invention is to overcome the problems existing in the above-mentioned prior art, and provide a silicon negative electrode material, a method for producing the same, and use thereof.

[0006] The present invention is achieved by the following technical means. The present invention provides a silicon anode material comprising a porous γ-phase lithium methaluminate and a carbon coating layer, wherein a carbon layer and a silicon material layer are sequentially deposited within the pores of the porous γ-phase lithium methaluminate, and the carbon coating layer covers the surface of the porous γ-phase lithium methaluminate on which the carbon layer and the silicon material layer are deposited.

[0007] In the silicon anode material of the present invention, a γ-phase lithium methaluminate having a regularly porous structure is used as the substrate, and a carbon layer and a silicon material layer are sequentially deposited in the pores of the porous γ-phase lithium methaluminate. By depositing the carbon layer first, the conductivity of the silicon anode material is improved, and then the silicon material is deposited. By depositing the silicon material in the pores of the porous γ-phase lithium methaluminate, the volume expansion of the silicon material can be effectively mitigated, and the generation of stress can be reduced. Furthermore, the pores of the porous γ-phase lithium methaluminate can guide the orderly deposition of the silicon material, ensuring the integrity and uniformity of the carbon coating. Compared to other porous materials, the porous γ-phase lithium methaluminate has high ionic conductivity and high mechanical strength, so it can effectively improve ionic conductivity while maintaining the material structure. The present invention improves the electrochemical performance of the material by effectively modifying the nanosilicon material, preventing it from directly contacting the electrolyte to avoid the occurrence of side reactions, suppressing the volume expansion of silicon during the cycle process from the material side, effectively mitigating volume changes, and further stabilizing the structure of the electrode material.

[0008] In a preferred embodiment of the silicon anode material of the present invention, the silicon material includes elemental silicon. In some embodiments, the silicon material layer includes elemental silicon.

[0009] In a preferred embodiment of the silicon anode material of the present invention, the particle size Dv50 of the elemental silicon is 1 nm to 300 nm, preferably 1 nm to 100 nm, 1 nm to 80 nm, 1 nm to 70 nm, 1 nm to 60 nm, 1 nm to 50 nm, 1 nm to 40 nm, 1 nm to 30 nm, 1 nm to 20 nm, 1 nm to 10 nm, or 1 nm to 6 nm. In this specification, the particle size Dv50 of the elemental silicon can be directionally controlled by a CVD film deposition method well known to those skilled in the art.

[0010] Preferably, the silicon material layer accounts for 30% to 50% of the mass of the silicon anode material. In a preferred embodiment of the silicon anode material of the present invention, the pore size of the porous γ-phase lithium methaluminate is 1 nm to 500 nm.

[0011] When the pore size of the porous γ-phase lithium methaluminate falls within the above range, it can be matched to the particle size of commercially available general silicon materials, thereby providing good conductivity to the silicon anode material.

[0012] Preferably, the carbon source of the carbon coating layer and the carbon layer each independently contains at least one of alkanes, alkenes, and alkynes. In some embodiments, the alkane is methane.

[0013] Preferably, the deposition thickness of the carbon layer is 3 nm to 4 nm.

[0014] In this invention, the thickness of the carbon coating layer is not limited. It can be adjusted as appropriate, depending on the actual requirements, for example, according to the desired capacity value or other electrochemical performance requirements.

[0015] Another object of the present invention is to provide a method for producing the silicon anode material, which includes the following steps. (1) A lithium salt solution, an organoaluminum solution, and a complexing agent are uniformly mixed and evaporated while stirring to obtain a gel; (2) The gel obtained in step (1) is freeze-dried, a carbon layer is deposited, then a silicon material is deposited, and then it is calcined to perform carbon coating, thereby obtaining the silicon anode material.

[0016] This invention provides a method for producing porous γ-phase lithium methaluminate by sol-gel method and freeze-drying method. Freeze-drying allows for the direct sublimation of the solvent to form a porous structure. The porous γ-phase lithium methaluminate obtained by the production method of this invention has a honeycomb-like structure and has almost no distinct flat, solid structures. Therefore, subsequent carbon layers and silicon materials are deposited within the pores, improving the electrochemical performance of the silicon anode material.

[0017] In a preferred embodiment of the method for producing the silicon anode material of the present invention, the complexing agent in step (1) includes at least one of urea, citrate, and hydrazine.

[0018] The complexing agent has the effect of forming complex aggregates, which facilitate the sublimation of the solvent inside the aggregates during freeze-drying, forming a porous structure. All of the above complexing agents have good complexing effects, and among them, urea is preferred from an economic standpoint because its price is relatively low.

[0019] In a preferred embodiment of the method for manufacturing the silicon anode material of the present invention, the temperature of the stirring evaporation in step (1) is 40°C to 100°C, preferably 50°C to 90°C or 60°C to 80°C.

[0020] In a preferred embodiment of the method for producing the silicon anode material of the present invention, the freeze-drying rate in step (2) is 2°C / min to 10°C / min.

[0021] The freeze-drying rate determines the sublimation rate of the solvent, and the pore size of the γ-phase lithium methaluminate can be adjusted by the freeze-drying rate. If the rate is too high, the formed pore size will be too large, and the silicon material may overlap, affecting the electrochemical performance and the volume expansion suppression effect. If the rate is too low, the formed pore size will be too small, and the amount of silicon material deposited may be insufficient, making it impossible to achieve the volume target and volume buffering effect. When the freeze-drying rate is between 2°C / min and 10°C / min, a porous γ-phase lithium methaluminate with an appropriate pore size can be obtained.

[0022] Preferably, in step (2), the freeze-drying rate is 3°C / min to 7°C / min.

[0023] More preferably, when the freeze-drying rate is 3°C / min to 7°C / min, a porous lithium γ-phase methaluminate with a more appropriate pore size and distribution can be obtained.

[0024] Preferably, the concentration of lithium salt in the lithium salt solution is 1.5 mol / L to 1.7 mol / L, the concentration of organoaluminum in the organoaluminum solution is 0.3 mol / L to 0.5 mol / L, and the amount of complexing agent added is 10% to 11% of the total mass of the lithium salt and the organoaluminum.

[0025] Preferably, the solvent for the lithium salt solution contains ethanol and water. Preferably, the solvent for the lithium salt solution contains anhydrous ethanol and deionized water. Preferably, the solvent for the organoaluminum solution contains ethanol. Preferably, the solvent for the organoaluminum solution contains anhydrous ethanol. Preferably, in the solvent for the lithium salt solution, the volume ratio of ethanol to water is (1-5):1, and more preferably (1-3):1.

[0026] Preferably, the lithium salt is lithium acetate, and the organoaluminum is aluminum isopropoxide.

[0027] As a preferred embodiment of the method for producing a silicon negative electrode material of the present invention, in the step (2), the firing temperature is 300°C to 1000°C, and the firing time is 1h to 3h.

[0028] Preferably, in the step (2), the firing temperature is 700°C to 900°C.

[0029] In the present invention, the firing temperature affects the formation of γ-phase lithium meta-aluminate. If the firing temperature is too low, impurity-phase lithium meta-aluminate will be formed; if the firing temperature is too high, the loss of lithium salt will increase and multiple impurity phases will be formed. Setting the firing temperature to 700°C to 900°C is a more suitable condition for producing porous γ-phase lithium meta-aluminate.

[0030] Preferably, in the step (2), the method for depositing a carbon layer, depositing a silicon material and performing carbon coating is a CVD method. The initial deposition of the carbon layer is used to form a base layer in the pores of the porous γ-phase lithium meta-aluminate, followed by the deposition of the silicon material. The deposition of the silicon material can completely fill the porous structure inside the porous γ-phase lithium meta-aluminate; after removing the silicon material outside the pores, the silicon material is completely encapsulated by carbon coating.

[0031] Still another object of the present invention is to provide a secondary battery comprising the silicon negative electrode material or the silicon negative electrode material produced by the above method for producing the silicon negative electrode material.

[0032] The secondary battery using the silicon negative electrode material of the present invention has higher rate performance and cycle performance.

[0033] The present invention has the following beneficial effects. The silicon anode material of the present invention uses porous γ-phase lithium methaluminate as a base material, and the conductivity of the silicon anode material can be improved by depositing a carbon layer. Porous γ-phase lithium methaluminate effectively mitigates the volume expansion of the silicon material in the pores, reduces the generation of stress, and has high ionic conductivity and high mechanical strength, thereby effectively improving ionic conduction while maintaining the material structure. The silicon anode material of the present invention effectively prevents the silicon material from coming into direct contact with the electrolyte, suppresses the volume expansion of silicon during the cycle process from the material side, effectively mitigates volume changes, and further stabilizes the structure of the electrode material, thereby improving the electrochemical performance of the material. [Brief explanation of the drawing]

[0034] [Figure 1] This is the XRD diffraction pattern of the porous γ-phase lithium methaluminate obtained by step (1) of Example 1. [Modes for carrying out the invention]

[0035] To more clearly explain the object, technical means, and advantages of the present invention, the present invention will be further described below with reference to specific examples. Those skilled in the art should understand that the specific examples described herein are for illustrative purposes only and do not limit the present invention.

[0036] Unless otherwise specified, the test methods used in the examples are all conventional methods. Unless otherwise specified, the materials and reagents used can be obtained commercially.

[0037] Scanning electron microscopy (SEM) was used to measure the particle size Dv50 of elemental silicon and the pore size of porous γ-phase lithium methaluminate.

[0038] The thickness of the carbon layer was measured using a transmission electron microscope (TEM).

[0039] Thermogravimetric analysis (TGA) was used to measure the mass fraction of the silicon material layer relative to the silicon anode material.

[0040] Example 1 A method for manufacturing a silicon anode material includes the following steps. (1) 20 mL of anhydrous ethanol and 10 mL of deionized water were measured out, poured into a beaker, stirred to mix uniformly, and 3.30 g of lithium acetate was added while stirring. Stirring was continued until the lithium acetate was completely dissolved to obtain a colorless, transparent lithium salt solution. 100 mL of anhydrous ethanol was measured out and poured into another beaker. While stirring, 10.12 g of aluminum isopropoxide powder was added to uniformly disperse the aluminum isopropoxide in the ethanol, obtaining a colorless and transparent aluminum isopropoxide solution. The lithium salt solution was added to the aluminum isopropoxide solution, 1.35 g of urea as a complexing agent was added, and the mixture was stirred continuously for 1 hour. The mixed solution was then transferred to a 60°C water bath and evaporated while stirring to obtain a gel. (2) The gel obtained in step (1) was freeze-dried at a freeze-drying rate of 5°C / min; after drying, a carbon layer was deposited by CVD, followed by the deposition of elemental silicon, constant temperature firing at 900°C for 2 hours, and the material after firing was carbon-coated by CVD to obtain the silicon anode material; here, the carbon source for both the carbon layer material and the carbon coating layer material was methane.

[0041] In the silicon anode material of this embodiment, the particle size Dv50 of elemental silicon was 6 nm, the pore size of the porous γ-phase lithium methaluminate was 80 nm to 120 nm, the deposition thickness of the carbon layer was 3 nm to 4 nm, and the silicon material layer accounted for 43% of the mass of the silicon anode material.

[0042] After firing the gel obtained in step (1) at 900°C for 2 hours, the XRD pattern was measured. As shown in Figure 1, the characteristic diffraction peaks of (003), (104), and (110) of the sample were relatively clear and in good agreement with the standard card. The sharp peak shapes and high intensity confirmed good crystallinity.

[0043] Example 2 The main difference between the manufacturing method of the silicon anode material in this embodiment and that of Example 1 is that the firing temperature in step (2) is 800°C. Other manufacturing methods and parameters are the same as in Example 1 to obtain the silicon anode material of this embodiment.

[0044] In the silicon anode material of this embodiment, the particle size Dv50 of elemental silicon was 6 nm, the pore size of the porous γ-phase lithium methaluminate was 80 nm to 120 nm, the deposition thickness of the carbon layer was 3 nm to 4 nm, and the silicon material layer accounted for 43% of the mass of the silicon anode material.

[0045] Example 3 The main difference between the manufacturing method of the silicon anode material in this embodiment and that of Example 1 is that the firing temperature in step (2) is 700°C. Other manufacturing methods and parameters are the same as in Example 1 to obtain the silicon anode material of this embodiment.

[0046] In the silicon anode material of this embodiment, the particle size Dv50 of elemental silicon was 6 nm, the pore size of the porous γ-phase lithium methaluminate was 80 nm to 120 nm, the deposition thickness of the carbon layer was 3 nm to 4 nm, and the silicon material layer accounted for 43% of the mass of the silicon anode material.

[0047] Example 4 The main difference between the manufacturing method of the silicon anode material in this embodiment and that of Example 1 is that the firing time in step (2) is 1 hour. Other manufacturing methods and parameters are the same as in Example 1 to obtain the silicon anode material of this embodiment.

[0048] In the silicon anode material of this embodiment, the particle size Dv50 of elemental silicon was 6 nm, the pore size of the porous γ-phase lithium methaluminate was 80 nm to 120 nm, the deposition thickness of the carbon layer was 3 nm to 4 nm, and the silicon material layer accounted for 43% of the mass of the silicon anode material.

[0049] Example 5 The main difference between the manufacturing method of the silicon anode material in this embodiment and that of Example 1 is that the freeze-drying rate in step (2) is 3°C / min. Other manufacturing methods and parameters are the same as in Example 1 to obtain the silicon anode material of this embodiment.

[0050] In the silicon anode material of this embodiment, the particle size Dv50 of elemental silicon was 6 nm, the pore size of the porous γ-phase lithium methaluminate was 40 nm to 90 nm, the deposition thickness of the carbon layer was 3 nm to 4 nm, and the silicon material layer accounted for 43% of the mass of the silicon anode material.

[0051] Example 6 The main difference between the manufacturing method of the silicon anode material in this embodiment and that of Example 1 is that the freeze-drying rate in step (2) is 7°C / min. Other manufacturing methods and parameters are the same as in Example 1 to obtain the silicon anode material of this embodiment.

[0052] In the silicon anode material of this embodiment, the particle size Dv50 of elemental silicon was 6 nm, the pore size of the porous γ-phase lithium methaluminate was 110 nm to 160 nm, the deposition thickness of the carbon layer was 3 nm to 4 nm, and the silicon material layer accounted for 43% of the mass of the silicon anode material.

[0053] Example 7 The main difference between the manufacturing method of the silicon anode material in this embodiment and that of Example 1 is that the firing temperature in step (2) is 300°C. Other manufacturing methods and parameters are the same as in Example 1 to obtain the silicon anode material of this embodiment.

[0054] In the silicon anode material of this embodiment, the particle size Dv50 of elemental silicon was 6 nm, the pore size of the porous γ-phase lithium methaluminate was 80 nm to 120 nm, the deposition thickness of the carbon layer was 3 nm to 4 nm, and the silicon material layer accounted for 43% of the mass of the silicon anode material.

[0055] Example 8 The main difference between the manufacturing method of the silicon anode material in this embodiment and that of Example 1 is that the firing temperature in step (2) is 1000°C. Other manufacturing methods and parameters are the same as in Example 1 to obtain the silicon anode material of this embodiment.

[0056] In the silicon anode material of this embodiment, the particle size Dv50 of elemental silicon was 6 nm, the pore size of the porous γ-phase lithium methaluminate was 80 nm to 120 nm, the deposition thickness of the carbon layer was 3 nm to 4 nm, and the silicon material layer accounted for 43% of the mass of the silicon anode material.

[0057] Example 9 The main difference between the manufacturing method of the silicon anode material in this embodiment and that of Example 1 is that the freeze-drying rate in step (2) is 10°C / min. Other manufacturing methods and parameters are the same as in Example 1 to obtain the silicon anode material of this embodiment.

[0058] In the silicon anode material of this embodiment, the particle size Dv50 of elemental silicon was 6 nm, the pore size of the porous γ-phase lithium methaluminate was 150 nm to 190 nm, the deposition thickness of the carbon layer was 3 nm to 4 nm, and the silicon material layer accounted for 43% of the mass of the silicon anode material.

[0059] Example 10 The main difference between the manufacturing method of the silicon anode material in this embodiment and that of Example 1 is that the freeze-drying rate in step (2) is 2°C / min. Other manufacturing methods and parameters are the same as in Example 1 to obtain the silicon anode material of this embodiment.

[0060] In the silicon anode material of this embodiment, the particle size Dv50 of elemental silicon was 6 nm, the pore size of the porous γ-phase lithium methaluminate was 35 nm to 70 nm, the deposition thickness of the carbon layer was 3 nm to 4 nm, and the silicon material layer accounted for 43% of the mass of the silicon anode material.

[0061] Example 11 The main difference between the manufacturing method of the silicon anode material in this example and Example 1 is that the film deposition conditions of the CVD method for depositing elemental silicon were changed, thereby obtaining the silicon anode material of this example.

[0062] In the silicon anode material of this embodiment, the particle size Dv50 of the elemental silicon was 70 nm, the pore size of the porous γ-phase lithium methaluminate was 80 nm to 120 nm, the deposition thickness of the carbon layer was 3 nm to 4 nm, and the silicon material layer accounted for 43% of the mass of the silicon anode material.

[0063] Comparative Example 1 A method for manufacturing a silicon anode material, comprising the following steps: (1) Measure out 20 mL of anhydrous ethanol and 10 mL of deionized water, pour them into a beaker, stir to mix uniformly, add 3.30 g of lithium acetate while stirring, and continue stirring until completely dissolved to obtain a colorless, transparent lithium salt solution; 100 mL of anhydrous ethanol was measured out and poured into another beaker. While stirring, 10.22 g of aluminum isopropoxide powder was added to uniformly disperse the aluminum isopropoxide in the ethanol, obtaining a colorless, transparent aluminum isopropoxide solution. The lithium salt solution was added to the aluminum isopropoxide solution, 1.35 g of urea as a complexing agent was added, and the mixture was stirred continuously for 1 hour. The mixed solution was then transferred to a 60°C water bath and evaporated while stirring to obtain a gel. (2) The gel obtained in step (1) was fired at 900°C for 2 hours, then a carbon layer was deposited by CVD, followed by the deposition of elemental silicon, and finally the material after firing was coated with carbon by CVD to obtain the silicon anode material.

[0064] The main difference between this comparative example and Example 1 is that the gel obtained in step (1) was not freeze-dried, and the resulting γ-phase lithium methaluminate does not have a porous structure.

[0065] Comparative Example 2 A method for manufacturing a silicon anode material, comprising the following steps: using aluminum oxide, a commercially available porous ceramic material, as a substrate, first depositing a carbon layer by CVD, then depositing silicon particles, performing a constant temperature firing treatment at 900°C for 2 hours, and then carbon coating the fired material by CVD to obtain the silicon anode material.

[0066] In the silicon anode material of this comparative example, the particle size Dv50 of the elemental silicon was 6 nm, the pore size of the porous ceramic material, aluminum oxide, was 80 nm to 120 nm, the deposition thickness of the carbon layer was 3 nm to 4 nm, and the silicon material layer accounted for 43% of the mass of the silicon anode material.

[0067] Comparative Example 3 The main difference between the manufacturing method of the silicon anode material in this comparative example and that of Example 1 is that carbon layer deposition and carbon coating are not performed in step (2). Other manufacturing methods and parameters are the same as those of Example 1 to obtain the silicon anode material of this comparative example.

[0068] In the silicon anode material of this comparative example, the particle size Dv50 of the elemental silicon was 6 nm, the pore size of the porous γ-phase lithium methaluminate was 80 nm to 120 nm, and the silicon material layer accounted for 43% of the mass of the silicon anode material.

[0069] Battery manufacturing A silicon anode piece was fabricated using the silicon anode materials of the above examples and comparative examples, and a secondary battery was then constructed.

[0070] Specifically, the steps for preparing the silicon anode pieces are as follows: The silicon anode materials, polyacrylic acid (PAA), carbon black (SP), and single-walled carbon nanotubes from the above examples and comparative examples were weighed in a mass percentage ratio of 0.95:0.4:0.95:0.05, mixed, stirred in a beaker for 30 minutes, then coated onto the copper foil surface, vacuum-dried at 60°C for 2 hours, and cut into circular pieces with a diameter of 14 mm.

[0071] Specifically, the steps for fabricating the secondary battery are as follows: The silicon negative electrode piece fabricated above was used as the working electrode, the lithium piece as the counter electrode, and LiPF6 / EC + DMC + DEC (volume ratio 1:1:1) was used as the electrolyte to assemble a CR2016 type coin cell.

[0072] Electrochemical performance test Rate test: Current density 0.1A / g to 1.6A / g to 0.1A / g, voltage range 0.01V to 3.0V. Rate performance is the ratio of the capacity at 0.1A / g after 1.6A / g to the capacity at the initial 0.1A / g.

[0073] Cycle test: The battery capacity retention rate was evaluated after 300 cycles with a current density of 0.1 A / g and a voltage range of 0.01 V to 3.0 V.

[0074] The results of the electrochemical performance tests described above are shown in Table 1.

[0075] Table 1: Performance test results of batteries obtained from the examples and comparative examples. [Table 1]

[0076] From the data in Table 1, it can be seen that when the silicon anode material obtained by the embodiment of the present invention is applied to a battery, a significant improvement in performance is observed compared to Comparative Examples 1 to 3. From the data results of Example 1 and Comparative Example 1, it can be seen that because the γ-phase lithium methaluminate of Comparative Example 1 has a non-porous structure, the deposited silicon particles are exposed to the outside and react violently with the electrolyte, resulting in a significant deterioration of rate performance and cycle performance. From the data results of Example 1 and Comparative Example 2, it can be seen that conventional porous high-speed ion conductive materials have inferior ion conductivity and expansion suppression effect compared to the porous γ-phase lithium methaluminate of the present invention. From the data results of Example 1 and Comparative Example 3, it can be seen that when a carbon layer is not deposited in the pores of the γ-phase lithium methaluminate prepared by the present invention and carbon coating is not performed, the conductivity of the silicon anode material decreases, and as a result, both the rate performance and cycle performance of the fabricated secondary battery are significantly reduced.

[0077] The data results from Examples 1 and 7 show that if the calcination temperature is too low, impurity phases are generated, reducing the synthesis quality of γ-type lithium metaaluminate and negatively impacting rate performance and cycle performance. The data results from Examples 1 and 8 show that if the calcination temperature is too high, lithium salts volatilize excessively during the synthesis process, generating multiple impurity phases, which is also negatively impacting rate performance and cycle performance. The data results from Examples 1 and 9 show that if the drying rate is too high, the pore size becomes excessively large, uniformity decreases, ion conduction resistance increases, and rate performance deteriorates. The data results from Examples 1 and 10 show that if the drying rate is too low, the step time increases, the pore size becomes too small, which is unfavorable for particle deposition, and particles may be exposed to the outside, resulting in reduced cycle performance.

[0078] The data results from Examples 1 and 11 show that when the particle size Dv50 of the individual silicon is large, both rate performance and cycle performance decrease. However, the rate performance of the battery made using the silicon anode material of Example 11 is still much higher than that of the batteries of Comparative Examples 1 to 3.

[0079] Based on the above, the silicon anode material of the present invention can effectively improve the electrochemical performance of a battery. When a battery using the silicon anode material provided by the present invention is subjected to charge-discharge tests in the voltage range of 0.01 to 3.0 V with current densities of 0.1 A / g to 1.6 A / g to 0.1 A / g, the ratio of the capacity at 0.1 A / g after 1.6 A / g to the initial capacity at 0.1 A / g can reach 98.4%. Furthermore, the capacity retention rate after 300 cycles at 0.1 A / g can reach 98.2%.

[0080] In conclusion, the above embodiments are for illustrative purposes only and do not limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical means of the present invention, none of which will depart from the technical spirit and scope of the present invention.

Claims

1. A silicon anode material comprising a porous γ-phase lithium methaluminate and a carbon coating layer, A silicon anode material characterized in that a carbon layer and a silicon material layer are sequentially deposited in the pores of the porous γ-phase lithium metaaluminate, and the carbon coating layer covers the surface of the porous γ-phase lithium metaaluminate on which the carbon layer and the silicon material layer are deposited.

2. The silicon anode material according to claim 1, characterized in that the silicon material layer includes elemental silicon.

3. The silicon anode material according to claim 2, characterized in that the particle size Dv50 of the elemental silicon is 1 nm to 300 nm.

4. The silicon anode material according to claim 1, characterized in that the pore size of the porous γ-phase lithium methaluminate is 1 nm to 500 nm.

5. The silicon anode material according to claim 1, characterized in that the carbon coating layer and the carbon source of the carbon layer each independently contain at least one of alkanes, alkenes, and alkynes.

6. A method for manufacturing a silicon anode material according to any one of claims 1 to 5, Step (1) involves uniformly mixing a lithium salt solution, an organoaluminum solution, and a complexing agent, and evaporating them while stirring to obtain a gel. Step (2) involves freeze-drying the gel obtained in step (1), depositing a carbon layer, then depositing a silicon material, firing, and carbon coating to obtain the silicon anode material. A manufacturing method characterized by including the following.

7. The manufacturing method according to claim 6, characterized in that the complexing agent in step (1) comprises at least one of urea, citrate, and hydrazine.

8. The manufacturing method according to claim 6, characterized in that in step (2), the freeze-drying rate is 2°C / min to 10°C / min.

9. The manufacturing method according to claim 6, characterized in that in step (2), the firing temperature is 300°C to 1000°C and the firing time is 1 hour to 3 hours.

10. A secondary battery characterized by comprising a silicon anode material according to any one of claims 1 to 5, or a silicon anode material manufactured by a manufacturing method according to any one of claims 6 to 9.

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