Carbon-coated silicon-oxygen negative electrode material and preparation method thereof

Abstract

The application belongs to the field of electrochemistry and discloses a carbon-coated silicon-oxygen negative electrode material and a preparation method thereof to solve the technical problem of poor stability caused by the anisotropic expansion of the material. Silicon monoxide is carboxylated to obtain a precursor A; the precursor A is added into an aqueous solution of gelatin and potassium chloride to obtain a dispersion B; an aqueous crosslinking agent containing amino groups is dispersed in water with amino carbon nanotubes or amino graphene to obtain a dispersion C; the dispersion C is mixed with the dispersion B, and after heating, stirring, spray drying, high-temperature carbonization and cleaning, the carbon-coated silicon-oxygen negative electrode material is obtained. The hydroxylated modified silicon monoxide and the amino groups are chemically bonded by heating and dehydration, the potassium chloride and the gelatin are physically deposited and coated after spray drying, and the internal interpenetrating carbon tube and the outer porous channel coating layer are formed after high-temperature reaction and cleaning, thereby forming a three-dimensional coating structure. This structure can expand the silicon-carbon negative electrode material, thereby further improving the cycle stability of the material.

Description

Technical Field

[0001] This invention relates to the field of electrochemistry, and more particularly to a method for preparing silicon suboxide anode materials. Background Technology

[0002] Compared to elemental silicon particles, silicon suboxide (SiOx) experiences less volume expansion during lithium intercalation, resulting in significantly improved cycle stability compared to pure silicon anodes. Companies like Shin-Etsu Chemical (Japan), Daewoo (South Korea), Shanshan (China), and BTR (China) can all mass-produce silicon-oxygen anodes. However, silicon suboxide anodes generate inactive substances such as Li₂O during charge and discharge, leading to a low initial efficiency (approximately 70%). The root cause lies in the repeated breakdown of the already formed SEI layer and its repeated contact with the electrolyte, forming new interface layers and consuming active lithium. Therefore, to promote the industrialization of silicon-oxygen anode materials, it is necessary to address the issues of low cycle stability and low initial efficiency by focusing on the uniformity and stability of the carbon coating on the material surface, striving to obtain a uniform and dense carbon coating layer.

[0003] Chinese patent CN113889596A discloses a method for preparing nitrogen-doped hard carbon-coated artificial graphite composite materials. The method involves oxidizing artificial graphite and then oxidizing a hard carbon precursor containing amino resin or amino-containing epoxy resin, followed by a chemical reaction at 100–300°C to achieve hard carbon coating of the graphite. However, this coating strategy suffers from several drawbacks. The large molecular structure of the resin easily leads to the formation of aggregated hard carbon layers on the graphite surface. This steric hindrance is significant and hinders the formation of a thin and uniform coating structure. Furthermore, the high reaction temperature causes premature decomposition of the coated organic matter, affecting the coating structure. Additionally, the internal conductivity of the coated carbon structure is limited, which is detrimental to electron transport and ion migration. Therefore, there is an urgent need to develop a low-temperature reaction process to form the precursor, followed by high-temperature carbonization and coating to create a multi-dimensional carbon coating network, which would significantly improve the electron transport efficiency of the material.

[0004] Chinese patent CN112635734A discloses a method for preparing carbon nanotube-loaded carbon-coated silica materials and their applications. The carbon nanotube-loaded carbon-coated silica material uses carboxylated carbon nanotubes as a framework. Aminated nano-silica is adsorbed onto its surface using electrostatic adsorption. A carbon source liquid phase is used for coating. After the solution penetrates the silica, it undergoes pre-oxidation and carbonization stages, followed by high-temperature reduction treatment in a hydrogen-argon mixed gas for a certain period. Then, most of the silica is etched away, and finally, the powder is washed, dried, and ball-milled to obtain a carbon nanotube-loaded carbon-coated silica powder with a reinforced concrete-like structure. This method utilizes carbon nanotubes as a framework to electrostatically adsorb nano-silica onto the surface, solving the problems of easy agglomeration and difficult dispersion of carbon nanotubes. However, the electrostatic adsorption force is weak, which is still useful for nano-sized silica, but this force has a narrow applicable particle size. Furthermore, the further carbon coating process easily destroys the aforementioned force, leading to the destruction of the adsorbed particle structure and making it difficult to maintain the coating configuration. Summary of the Invention

[0005] To address the problem of uneven current density on the surface of silicon-oxygen anode materials prepared by existing technologies due to electronic conductivity issues, which further leads to anisotropic expansion and poor stability, this invention proposes a carbon-coated silicon-oxygen anode material and its preparation method. After surface modification of silicon-oxygen, a stable three-dimensional coating structure composed of inner amino small molecule organic matter and carbon nanotubes is formed through covalent bonding. This is then combined with a potassium chloride / gelatin system for an outer layer of two-dimensional conductive electron fast channels, ultimately forming a three-dimensional synergistic coating strategy that integrates an interwoven conductive network and two-dimensional conductive electron channels. This approach prepares an anode material that meets the dual requirements of two-dimensional coating electronic pathways and three-dimensional conductivity.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] A method for preparing a carbon-coated silicon-oxygen anode material, comprising the following steps:

[0008] (1) After dispersing the silane coupling agent and succinic anhydride in N,N-dimethylformamide (DMF), a silica-containing DMF suspension and water are added. The silane coupling agent undergoes hydrolysis. After heating and stirring, the hydrolyzed coupling agent, anhydride and silicon oxide react chemically. After centrifugation and washing with ethanol, the surface carboxylated modified silica-containing material is obtained, namely precursor A.

[0009] (2) Dissolve gelatin and potassium chloride in deionized water, add precursor A to obtain dispersion B; disperse an amino-containing water-soluble crosslinking agent with amino carbon nanotubes or amino graphene in water to obtain dispersion C.

[0010] (3) Dispersion C is added to dispersion B to obtain solution D. After heating and stirring, the crosslinking agent, the amino groups on the carbon nanotubes and the carboxyl groups on the silicon-oxygen surface bond to form a coating. Gelatin and potassium chloride are present in the aqueous solution. After spray drying, potassium chloride and gelatin, as solutes, are instantaneously dried in situ on the coating structure with bonded amino compounds to form a two-dimensional coating structure. After high-temperature carbonization, a three-dimensional coating layer is formed. After further cleaning away the potassium chloride in the outer two-dimensional coating structure, a solid inner coating and a porous three-dimensional carbon coating silicon-oxygen anode material on the outer surface are obtained.

[0011] In step (1) above, the molar ratio of silane coupling agent to succinic anhydride is 1:(1-1.2); the mass ratio of succinic anhydride, water and silica is 1:2:(0.7-1.3).

[0012] Furthermore, in step (1), the silane coupling agent is any one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, and azirethylaminopropyltrimethoxysilane.

[0013] In step (1) above, the heating and stirring temperature is 50-80℃ and the time is 1-5h.

[0014] In step (2) above, the mass ratio of gelatin, potassium chloride and precursor A in dispersion B is 1:10:(1-1.5).

[0015] In step (3) above, the solution D contains an amino-based water-soluble crosslinking agent, precursor A, amino carbon nanotubes or amino graphene in a mass ratio of 1:(10-15):(0.005-0.01).

[0016] Furthermore, the water-soluble crosslinking agent containing amino groups is at least one of ethylene glycolamine, triethanolamine, and hexamethoxymethylmelamine.

[0017] In step (3) above, the heating and stirring temperature is 50-90℃ and the time is 10-24h; the high-temperature carbonization temperature is 700-800℃ and the time is 1-5h.

[0018] In step (3) above, spray drying can be carried out by means of dual-fluid spray drying, centrifugal atomizing disc spray drying or pressure spray drying; high-temperature carbonization is carried out in pure inert gases such as argon and nitrogen.

[0019] Carbon-coated silicon-oxygen anode material prepared using the above-described preparation method.

[0020] The above-mentioned carbon-coated silicon-oxygen anode material is used in lithium-ion batteries.

[0021] The beneficial effects of this invention are:

[0022] (1) This invention utilizes the principle of chemical bonding between amino carbon nanotubes or amino graphene and small-molecule amino crosslinking agents and carboxylated silicon oxide materials. Through heating, the crosslinking agent and carbon nanotubes / graphene are chemically bonded in situ on the silicon oxide surface, forming a precursor with a firmly coated surface. Furthermore, a high-concentration potassium chloride and gelatin are instant-deposited onto the precursor surface using a spray-drying method. After high-temperature reaction and cleaning, a three-dimensional coating structure is formed with internally interwoven carbon nanotubes and an outer porous channel coating layer. Firstly, the porous outer layer of this structure facilitates electrolyte wetting, increases electrode electrolyte retention, facilitates shortening carrier transport distance, improves surface charge transfer efficiency, and reduces expansion caused by uneven ion reactions. Secondly, this outer layer structure buffers internal expansion stress, offsets expansion space, and further reduces macroscopic expansion. Additionally, the inner stabilizing coating layer prevents further side reactions in the electrolyte, improving the structural stability of the negative electrode material and the uniformity of surface current density, thereby enhancing charge-discharge cycle stability and reducing the expansion of the silicon-carbon negative electrode material.

[0023] (2) The carbon-coated silicon-oxygen anode material prepared by the present invention has a stable capacity of 1550mAh / g at a current density of 1000mA / g, and after 100 cycles, the capacity retention rate of the battery is as low as 96%, and the expansion rate of the electrode can be as low as 112%. Attached Figure Description

[0024] 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 The image shows the structure of the carbon-coated silicon-oxygen anode material prepared in Example 1 of this invention, as shown in the electron microscope image.

[0026] Figure 2 The image shows the structure of the carbon-coated silicon-oxygen anode material prepared in Comparative Example 3 of this invention, as shown in the electron microscope image.

[0027] Figure 3 The diagram shows the discharge specific capacity cycle performance of the materials in Example 1 and Comparative Examples 1 and 2 of this invention. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] The preparation method of the carbon-coated silicon-oxygen anode material in this embodiment includes the following steps:

[0031] (1) 5 mmol γ-aminopropyltriethoxysilane and 5 mmol succinic anhydride were uniformly dispersed in 50 mL DMF and stirred at 70 °C for 1 h. Then, 5 g of DMF dispersion containing 10% silica was added. After adding 1 g of water, the mixture was heated and stirred at 50 °C for 5 h and then centrifuged. After washing with ethanol three times, the mixture was dried to obtain surface carboxylated modified silica material, namely precursor A.

[0032] (2) Dissolve 5g of gelatin and 50g of potassium chloride in 500mL of deionized water, heat to 50℃ and stir. Then add 5g of surface carboxylated modified silica material to the above solution and stir continuously at 50℃ to obtain a dispersion. Take 0.5g of ethylene glycolamine and 0.005g of amino carbon nanotubes, disperse them in water by ultrasonication, and then add them to the above dispersion. Stir, heat to 50℃ and stir for 24h, and then spray dry to obtain the precursor.

[0033] (3) The precursor is transferred to a sintering furnace and sintered at 700°C for 5 hours under Ar atmosphere protection. After washing with water three times to remove potassium chloride, carbon-coated silicon-oxygen anode material is obtained.

[0034] The microstructure of the samples prepared in this example was determined using a Hitachi S-3400N scanning electron microscope, and the results are as follows: Figure 1 As shown, the material surface exhibits an irregular, multi-pore structure with alternating light and dark areas, sharp edges, fine and rough particles, and occasional carbon nanotubes. This indicates that after washing to remove soluble potassium chloride, pores were created to form a porous surface. The alternating light and dark areas may represent carbon layers and carbon particles with better conductivity.

[0035] Example 2

[0036] The preparation method of the carbon-coated silicon-oxygen anode material in this embodiment includes the following steps:

[0037] (1) 10 mmol γ-aminopropyltriethoxysilane and 12 mmol succinic anhydride were uniformly dispersed in 100 mL DMF and stirred at 50 °C for 5 h. Then, a DMF dispersion containing 8.4 g of silica (mass fraction 10%) was added, followed by the addition of 2.4 g of water. The mixture was heated and stirred at 50 °C for 5 h, then centrifuged. After washing with ethanol three times, the mixture was dried to obtain surface carboxylated modified silica material, i.e., precursor A.

[0038] (2) Dissolve 7g of gelatin and 70g of potassium chloride in 700mL of deionized water, heat to 50℃ and stir. Then add 10.5g of surface carboxylated modified silica material to the above solution and stir continuously at 50℃ to obtain a dispersion. Take 0.7g of ethylene glycolamine and 0.0035g of amino carbon nanotubes, disperse them in water by ultrasonication, and then add them to the above dispersion. Stir, heat to 90℃ and stir for 10h, and then spray dry to obtain the precursor.

[0039] (3) The precursor is transferred to a sintering furnace and sintered at 800°C for 1 hour under Ar atmosphere protection. After washing with water three times to remove potassium chloride, carbon-coated silicon-oxygen anode material is obtained.

[0040] Example 3

[0041] The preparation method of the carbon-coated silicon-oxygen anode material in this embodiment includes the following steps:

[0042] (1) 7 mmol γ-aminopropyltrimethoxysilane and 7 mmol succinic anhydride were uniformly dispersed in 70 mL DMF and stirred at 60 °C for 4 h. Then, a DMF dispersion containing 6 g of silica (mass fraction of 10%) was added, followed by the addition of 1.4 g of water. The mixture was heated and stirred at 60 °C for 3 h, then centrifuged. After washing with ethanol three times, the mixture was dried to obtain surface carboxylated modified silica material, i.e., precursor A.

[0043] (2) Dissolve 6g of gelatin and 60g of potassium chloride in 600mL of deionized water, heat to 50℃ and stir. Then add 6g of surface carboxylated modified silica material to the above solution and stir continuously at 50℃ to obtain a dispersion. Take 0.6g of ethylene glycolamine and 0.0045g of amino carbon nanotubes, disperse them in water by ultrasonication, and then add them to the above dispersion. Stir, heat to 80℃ and stir for 12h, and then spray dry to obtain the precursor.

[0044] (3) The precursor is transferred to a sintering furnace and sintered at 750°C for 2 hours under Ar atmosphere protection. After washing with water three times to remove potassium chloride, the carbon-coated silicon-oxygen anode material is obtained.

[0045] Example 4

[0046] The preparation method of the carbon-coated silicon-oxygen anode material in this embodiment includes the following steps:

[0047] (1) 8 mmol γ-aminopropyltrimethoxysilane and 8 mmol succinic anhydride were uniformly dispersed in 80 mL DMF and stirred at 60 °C for 2 h. Then, a DMF dispersion containing 9 g of silica (mass fraction of 10%) was added, followed by the addition of 1.6 g of water. The mixture was heated and stirred at 60 °C for 3 h, then centrifuged. After washing with ethanol three times, the mixture was dried to obtain surface carboxylated modified silica material, i.e., precursor A.

[0048] (2) Dissolve 9g of gelatin and 90g of potassium chloride in 900mL of deionized water, heat to 50℃ and stir. Then add 11.7g of surface carboxylated modified silica material to the above solution and stir continuously at 50℃ to obtain a dispersion. Take 0.9g of hexamethoxymethyl melamine and 0.0075g of amino carbon nanotubes, disperse them in water by ultrasonication, and then add them to the above dispersion. Stir, heat to 70℃ and stir for 18h, and then spray dry to obtain the precursor.

[0049] (3) The precursor is transferred to a sintering furnace and sintered at 750°C for 2 hours under N2 atmosphere protection. After washing with water three times to remove potassium chloride, carbon-coated silicon-oxygen anode material is obtained.

[0050] Example 5

[0051] The preparation method of the carbon-coated silicon-oxygen anode material in this embodiment includes the following steps:

[0052] (1) 6 mmol of N-ethylaminopropyltrimethoxysilane and 6 mmol of succinic anhydride were uniformly dispersed in 60 mL of DMF and stirred at 70 °C for 2 h. Then, a DMF dispersion containing 7 g of silica (mass fraction of 10%) was added to it. After adding 1.2 g of water, the mixture was heated and stirred at 70 °C for 2 h and then centrifuged. After washing with ethanol three times, the mixture was dried to obtain surface carboxylated modified silica material, i.e., precursor A.

[0053] (2) Dissolve 7g of gelatin and 70g of potassium chloride in 700mL of deionized water, heat to 50℃ and stir. Then add 7g of surface carboxylated modified silica material to the above solution and stir continuously at 50℃ to obtain a dispersion. Take 0.7g of triethanolamine and 0.0045g of amino carbon nanotubes, disperse them in water by ultrasonication, and then add them to the above dispersion. Stir, heat to 50℃ and stir for 12h, and then spray dry to obtain the precursor.

[0054] (3) The precursor is transferred to a sintering furnace and sintered at 720°C for 2 hours under N2 atmosphere protection. After washing with water three times to remove potassium chloride, carbon-coated silicon-oxygen anode material is obtained.

[0055] Example 6

[0056] The preparation method of the carbon-coated silicon-oxygen anode material in this embodiment includes the following steps:

[0057] (1) 7 mmol of N-ethylaminopropyltrimethoxysilane and 7.7 mmol of succinic anhydride were uniformly dispersed in 70 mL of DMF and stirred at 80 °C for 4 h. Then, a DMF dispersion containing 6 g of silica (mass fraction of 10%) was added, followed by the addition of 1.54 g of water. The mixture was heated and stirred at 80 °C for 3 h, then centrifuged, washed three times with ethanol, and dried to obtain surface carboxylated modified silica material, i.e., precursor A.

[0058] (2) Dissolve 6g of gelatin and 60g of potassium chloride in 600mL of deionized water, heat to 50℃ and stir. Then add 6g of surface carboxylated modified silica material to the above solution and stir continuously at 50℃ to obtain a dispersion. Take 0.6g of hexamethoxymethyl melamine and 0.0055g of amino carbon nanotubes, disperse them in water by ultrasonication, and then add them to the above dispersion. Stir, heat to 70℃ and stir for 16h, and then spray dry to obtain the precursor.

[0059] (3) The precursor is transferred to a sintering furnace and sintered at 700°C for 2 hours under Ar atmosphere protection. After washing with water three times to remove potassium chloride, the carbon-coated silicon-oxygen anode material is obtained.

[0060] Example 7

[0061] The preparation method of the carbon-coated silicon-oxygen anode material in this embodiment includes the following steps:

[0062] (1) 5 mmol of N-ethylaminopropyltrimethoxysilane and 5 mmol of succinic anhydride were uniformly dispersed in 50 mL of DMF and stirred at 80 °C for 1 h. Then, a DMF dispersion containing 6 g of silica (mass fraction of 10%) was added. After adding 1 g of water, the mixture was heated and stirred at 80 °C for 3 h and then centrifuged. After washing with ethanol three times, the mixture was dried to obtain surface carboxylated modified silica material, i.e., precursor A.

[0063] (2) Dissolve 6g of gelatin and 60g of potassium chloride in 600mL of deionized water, heat to 50℃ and stir. Then add 6g of surface carboxylated modified silica material to the above solution and stir continuously at 50℃ to obtain a dispersion. Take 0.6g of ethylene glycolamine and 0.005g of amino carbon nanotubes, disperse them in water by ultrasonication, and then add them to the above dispersion. Stir, heat to 70℃ and stir for 12h, and then spray dry to obtain the precursor.

[0064] (3) The precursor is transferred to a sintering furnace and sintered at 750°C for 2 hours under Ar atmosphere protection. After washing with water three times to remove potassium chloride, the carbon-coated silicon-oxygen anode material is obtained.

[0065] Comparative Example 1

[0066] The preparation method of the carbon-coated silicon-oxygen anode material in this comparative example differs from that in Example 1 in that the silicon suboxide is not modified by carboxylation. The steps are as follows:

[0067] (1) Dissolve 5g of gelatin and 50g of potassium chloride in 500mL of deionized water, heat to 50℃ and stir. Then add 5g of silica raw material to the above solution and stir continuously at 50℃ to obtain a dispersion. Take 0.5g of ethylene glycolamine and 0.005g of amino carbon nanotubes, disperse them in water by ultrasonication, and then add them to the above dispersion. Stir, heat to 50℃ and stir for 24h, and then spray dry to obtain the precursor.

[0068] (2) The precursor is transferred to a sintering furnace and sintered at 700°C for 5 hours under Ar atmosphere protection. After washing with water three times to remove potassium chloride, carbon-coated silicon-oxygen anode material is obtained.

[0069] Comparative Example 2

[0070] The preparation method of the carbon-coated silicon-oxygen anode material in this comparative example differs from that in Example 1 in that step (2) does not involve a heating operation. The steps are as follows:

[0071] (1) 5 mmol γ-aminopropyltriethoxysilane and 5 mmol succinic anhydride were uniformly dispersed in 50 mL DMF and stirred at 70 °C for 1 h. Then, 5 g of DMF dispersion containing 10% silica was added. After adding 1 g of water, the mixture was heated and stirred at 50 °C for 5 h and then centrifuged. After washing with ethanol three times, the mixture was dried to obtain surface carboxylated modified silica material, namely precursor A.

[0072] (2) Dissolve 5g of gelatin and 50g of potassium chloride in 500mL of deionized water. After stirring, add 5g of surface carboxylated modified silica material to the above solution and stir continuously to obtain a dispersion. Take 0.5g of ethylene glycolamine and 0.005g of amino carbon nanotubes, disperse them in water by ultrasonication, and then add them to the above dispersion. Stir for 24h and then spray dry to obtain the precursor.

[0073] (3) The precursor is transferred to a sintering furnace and sintered at 700°C for 5 hours under Ar atmosphere protection. After washing with water three times to remove potassium chloride, carbon-coated silicon-oxygen anode material is obtained.

[0074] Comparative Example 3

[0075] The preparation method of the carbon-coated silicon-oxygen anode material in this comparative example differs from that in Example 1 in that gelatin and potassium chloride are not added in step (2). The steps are as follows:

[0076] (1) 5 mmol γ-aminopropyltriethoxysilane and 5 mmol succinic anhydride were uniformly dispersed in 50 mL DMF and stirred at 70 °C for 1 h. Then, 5 g of DMF dispersion containing 10% silica was added. After adding 1 g of water, the mixture was heated and stirred at 50 °C for 5 h and then centrifuged. After washing with ethanol three times, the mixture was dried to obtain surface carboxylated modified silica material, namely precursor A.

[0077] (2) Take 5g of surface carboxylated modified silica material and add it to deionized water. Stir continuously at 50°C to obtain a dispersion. Take 0.5g of ethylene glycolamine and 0.005g of amino carbon nanotubes and disperse them in water by ultrasonication. Then add them to the above dispersion and stir. Heat at 50°C and stir for 24h. Then spray dry to obtain the precursor.

[0078] (3) The precursor is transferred to a sintering furnace and sintered at 700°C for 5 hours under Ar atmosphere protection. Finally, carbon-coated silicon oxide powder is obtained, and carbon-coated silicon oxide anode material is obtained after three water washings. Figure 2 The SEM image of the carbon-coated silicon-oxygen anode material prepared in this comparative example clearly shows the composite structure of amorphous carbon layer and carbon nanotubes, indicating that the surface is coated with a three-dimensional carbon layer with uniform amorphous carbon and intersecting carbon nanotubes.

[0079] Application examples

[0080] The negative electrode materials prepared according to the embodiments and comparative examples of the present invention were applied to lithium-ion batteries. The battery assembly process and electrochemical performance test results are as follows:

[0081] Coin cell battery: The silicon-oxygen anode material prepared in this invention is mixed with a conductive agent and a binder in a mass ratio of 8:1:1 to form a slurry, which is then uniformly coated onto copper foil and dried to obtain an electrode sheet. The binder is polyacrylic acid (PAA). A 1.0 mol / L LiPF6 electrolyte is used, wherein the volume ratio of the solvent components ethylene carbonate (EC): diethyl carbonate (DEC): dimethyl carbonate (DMC) is 1:1:1, and 10% fluoroethylene carbonate (FEC) is added. A microporous polypropylene separator is selected, and a lithium sheet is used as the counter electrode to assemble a CR2025 coin cell. Comparative Examples 1-2: Batteries are assembled according to the above method, and the battery performance is tested using a LANHE CT2001A battery testing system manufactured by Wuhan Landian Electronics Co., Ltd.

[0082] The initial test used a current density of 100 mA / g and a voltage range of 0.005–2.0 V. Constant current cycling performance testing was conducted at 25°C with a current density of 1000 mA / g and a voltage range of 0.005–2 V. Figure 3 The retention rate (96%) of Example 1 after 100 cycles is significantly better than that of Comparative Example 1 (6%) and Comparative Example 2 (4%). This is because a uniform coating layer is formed on the surface of the silicon oxide particles, which improves the conductivity of the material, accelerates the transport of charge carriers, and improves the charging and discharging efficiency of the material.

[0083] Full-cell electrode expansion test: The silicon-oxygen anode material prepared in this invention was mixed with a conductive agent and a binder at a mass ratio of 96:1:3, uniformly coated on copper foil, and dried to obtain the anode sheet. The binder was polyacrylic acid (PAA). A 1.0 mol / L LiPF6 electrolyte was used, in which the volume ratio of ethylene carbonate (EC): diethyl carbonate (DEC): dimethyl carbonate (DMC) was 1:1:1, and 10% fluoroethylene carbonate (FEC) was added. The positive electrode was NCM811, and a microporous polypropylene membrane was used. The room temperature cycling current was 0.5C, the rated capacity was 3.7 Ah, the voltage range was 2.8–4.2 V, and the depth of discharge was 100% DOD. The thickness of the silicon anode sheet after 100 cycles was measured with a micrometer, and the measurement results are shown in Table 1.

[0084] Table 1

[0085]

[0086] Wherein, the initial thickness is the designed electrode thickness, the FCC thickness is the silicon anode electrode thickness after cycling, and the expansion rate is calculated as (FCC thickness / initial thickness - 1) × 100%. As can be seen from the table, the FCC thickness of the electrode in Example 1 is 205.64 μm, with an expansion rate of 112%, while the FCC thickness of Comparative Example 1 is 222.36 μm, with an expansion rate of 129.24%. The cyclic expansion rate of the electrode in Example 1 is reduced by 17.24%.

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a carbon-coated silicon-oxygen anode material, characterized in that, The steps are as follows: (1) After dispersing the silane coupling agent and succinic anhydride in N,N-dimethylformamide, add silica-containing DMF suspension and water, and obtain precursor A after heating, stirring, centrifugation and washing; wherein, the molar ratio of silane coupling agent to succinic anhydride is 1:(1-1.2); the mass ratio of succinic anhydride, water and silica-containing oxide is 1:2:(0.7-1.3); (2) Dissolve gelatin and potassium chloride in deionized water, add precursor A to obtain dispersion B; disperse an amino-containing water-soluble crosslinking agent and amino carbon nanotubes in water to obtain dispersion C; wherein, the mass ratio of gelatin, potassium chloride and precursor A in dispersion B is 1:10:(1-1.5); wherein, the amino-containing water-soluble crosslinking agent is at least one of ethylene glycolamine, triethanolamine and hexamethoxymethylmelamine; (3) Dispersion C is added to dispersion B to obtain solution D. After heating and stirring, spray drying, high-temperature carbonization and washing, carbon-coated silicon-oxygen anode material is obtained. The mass ratio of amino water-soluble crosslinking agent, precursor A and amino carbon nanotubes in solution D is 1:(10-15):(0.005-0.01). The heating and stirring temperature is 50-90℃ and the time is 10-24h. The high-temperature carbonization temperature is 700-800℃ and the time is 1-5h.

2. The method for preparing carbon-coated silicon-oxygen anode material according to claim 1, characterized in that, In step (1), the silane coupling agent is any one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, and NAethylaminopropyltrimethoxysilane.

3. The method for preparing carbon-coated silicon-oxygen anode material according to claim 2, characterized in that, The heating and stirring temperature in step (1) is 50-80℃, and the time is 1-5h.

4. A carbon-coated silicon-oxygen anode material prepared by the preparation method according to any one of claims 1-3.

5. The application of the carbon-coated silicon-oxygen anode material according to claim 4 in lithium-ion batteries.

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