A composite negative electrode material, a preparation method thereof, and a product thereof

Abstract

The present invention belongs to the field of lithium-ion batteries and discloses a composite negative electrode material, which is mainly obtained by compounding a silicon negative electrode, a graphite negative electrode, and a silicon oxide aerogel in a mass ratio of 8-10:86-90:2-4. Also disclosed are a preparation method of the composite negative electrode material, a negative electrode sheet, and a lithium battery product. The present invention forms a composite negative electrode material with an aerogel framework by loading the active substance in the negative electrode material into the aerogel voids through a solvent reaction. The high-strength structural characteristics of the aerogel are utilized to ensure that the aerogel framework supports the lithium ion extraction and embedding process during the cycle, i.e., the lithium ion extraction and embedding process, thereby reducing structural strain, thereby ensuring the structural stability of the negative electrode and improving the cycle performance of lithium-ion batteries, especially silicon negative electrode lithium batteries; the aerogel has a high porosity, which can significantly improve the liquid retention capacity of the lithium battery electrode sheet, thereby improving the cycle performance; the aerogel technology has thermal insulation and high strength, which can significantly improve the safety performance of the lithium battery.

Description

Technical Field

[0001] The present invention belongs to the field of lithium-ion batteries, and in particular relates to a composite negative electrode material, a preparation method thereof, a negative electrode sheet thereof, and a lithium battery product. Background Art

[0002] Lithium-ion batteries are a new generation of green, high-energy batteries with superior performance and have become a key focus of high-tech development. They offer advantages such as high voltage, high capacity, low power consumption, no memory effect, no pollution, small size, low internal resistance, low self-discharge, and excellent cycle stability. Consequently, they are widely used in digital products such as mobile phones, laptops, camcorders, and digital cameras, as well as in new energy vehicles. As the application of lithium-ion batteries expands, so too are the requirements for their energy density, cycle stability, and safety.

[0003] The materials currently used in the negative electrode of lithium-ion batteries are divided into the following categories:

[0004] 1) Graphite negative electrode material + conductive agent + binder;

[0005] 2) Hard carbon negative electrode material + conductive agent + binder;

[0006] 3) Silicon-carbon mixed negative electrode material + conductive agent + binder.

[0007] Generally, in the lithium battery slurrying process, the above formula is evenly dispersed in water, and after thorough stirring, a suspension containing the negative electrode material, a conductive agent, and a binder is prepared. This suspension is then evenly coated on the current collector copper foil to produce the lithium battery negative electrode sheet. The lithium-ion battery is then assembled through the assembly process. In the prior art, because the negative electrode material expands during lithium ion extraction and insertion, especially silicon negative electrodes, which expand by up to 400% in volume during lithium ion extraction and insertion, and other types of negative electrode materials expand by up to 30% in volume during lithium ion extraction and insertion, the lithium-ion battery will suffer structural damage due to the expansion of the negative electrode structure during cycling, resulting in severe cycle attenuation. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology and provide a composite negative electrode and a preparation method thereof, a negative electrode sheet and a lithium battery product.

[0009] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0010] A composite negative electrode material is mainly obtained by compounding a silicon negative electrode, a graphite negative electrode and a silicon oxide aerogel, wherein the mass ratio of the silicon negative electrode, the graphite negative electrode and the silicon oxide aerogel is 8-10:86-90:2-4.

[0011] The gram capacity of graphite anodes is only 340mAh / g, while that of silicon anodes is 3200mAh / g. Using a hybrid anode with these two can significantly increase the gram capacity. However, because the silicon anode's lattice expands significantly during lithium ion insertion and extraction, it can easily cause structural damage and lead to poor cycling performance. Therefore, silicon anodes are generally mixed with graphite anodes. This patented method combines the two and then fills them into an aerogel framework, maintaining the structure during the cycle without structural damage, thereby significantly improving cycling performance.

[0012] In the above-mentioned composite negative electrode material, preferably, the mass ratio of the silicon negative electrode, the graphite negative electrode and the silicon oxide aerogel is 9:88:3.

[0013] Preferably, the silicon negative electrode is silicon oxide or elemental nano-silicon, and the graphite negative electrode is an artificial graphite negative electrode.

[0014] Preferably, the particle size of the composite negative electrode material is 1 μm-15 μm.

[0015] Based on a general inventive concept, the present invention also provides a method for preparing a composite negative electrode material, comprising the following steps:

[0016] (1) preparing a silicon oxide aerogel base liquid;

[0017] (2) uniformly mixing a trimethylsilyl chloride / n-hexane mixed solution, a silicon negative electrode, and graphite negative electrode particles to obtain a suspension containing a negative electrode active material, adding the suspension to the silica aerogel base liquid, stirring thoroughly and allowing the suspension to react, drying once and then allowing the suspension to react with acetone to extract the n-hexane, followed by secondary drying to obtain a hydrophobic silica aerogel composited with the negative electrode material, i.e., a composite negative electrode aerogel; wherein the n-hexane is the reaction medium, and the trimethylsilyl chloride mainly plays a pore-forming role; and the purpose of the soaking reaction is to disperse the various substances more evenly;

[0018] (3) The composite negative electrode aerogel is subjected to nanomolecular grinding treatment to obtain micron-scale powder particles, which are the composite negative electrode material.

[0019] In the above-mentioned preparation method, preferably, in step (1), the preparation method of the silica aerogel base liquid is as follows: ethyl orthosilicate, acetone, anhydrous ethanol and water are mixed evenly, the pH value is adjusted to 3-4 and then reacted, and then the pH value is adjusted to 6-7 and then allowed to stand for aging, and then soaked in anhydrous ethanol and heated for aging to obtain the silica aerogel base liquid.

[0020] Preferably, in step (1), the mass ratio of tetraethyl orthosilicate, acetone, anhydrous ethanol and water is 1-2:4-5:4-5:4-6; the pH value is adjusted to 3-4 with hydrochloric acid solution, and the reaction time is 10-20 hours; the pH value is adjusted to 6-7 with ammonia water, and the static aging time is 2-3 days; the heating aging temperature is 50°C, and the aging time is 1 day.

[0021] Preferably, in step (2), the mass concentration of the trimethylchlorosilane / n-hexane mixed solution is 10-15%; the mass ratio of the trimethylchlorosilane / n-hexane mixed solution, silicon negative electrode, and graphite negative electrode particles is 70-85:1-6:13-24; the mass ratio of the suspension to the silica aerogel is 100:2-4; the soaking reaction time is 2-3 days; the temperature of the primary drying and secondary drying is 50-60°C; the acetone soaking time is 1-2 days; and the secondary drying time is 5-7 days.

[0022] Based on a general inventive concept, the present invention further provides a negative electrode sheet, comprising a current collector and a negative electrode slurry coated on a surface of the current collector, wherein the negative electrode slurry comprises the composite negative electrode material.

[0023] The negative electrode sheet mentioned above is preferably composed of the following components in percentage by mass: 96.2-98% of composite negative electrode material, 0.1% of dispersant, 0.8-1.2% of binder, 0-1% of conductive agent, and 0.5-1.5% of thickener.

[0024] Preferably, the dispersant is at least one of sodium lauryl sulfate, sodium polypropylene sulfonate, and sodium lauryl sulfate; the binder is at least one of polyacrylic acid, lithium polyacrylate, styrene-butadiene rubber, sodium alginate, etc.; the thickener is at least one of CMC, polyacrylamide, and hydroxyethyl cellulose; and the conductive agent is at least one of acetylene black, graphene, and carbon nanotubes.

[0025] Based on a general inventive concept, the present invention also provides a lithium battery, comprising the aforementioned negative electrode sheet, positive electrode sheet, separator and electrolyte.

[0026] For the above-mentioned lithium battery, preferably, the preparation method of the positive electrode sheet is as follows: 98% of the active material, 1% of the binder, and 1% of the conductive agent are uniformly dispersed in NMP by mass percentage, and evenly coated on the current collector aluminum foil by coating, and dried to obtain the lithium battery positive electrode sheet.

[0027] Preferably, the electrolyte includes a non-aqueous organic solution, an electrolyte and an additive, wherein the non-aqueous organic solution contains at least one of EC, PC, EMC, DMC, and DEC; the electrolyte contains at least one of lithium hexafluorophosphate, LIBOB, FSI, and lithium hexafluoroborate; and the additive contains at least one of VC, PS, LIODFB, FB, and FEC.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention loads the active substance in the negative electrode material into the voids of the aerogel through a solvent reaction to form a composite negative electrode material with an aerogel frame. The high-strength structural characteristics of the aerogel are utilized to ensure that the aerogel frame process exists during the cycle process, i.e., the lithium ion extraction and embedding process, thereby reducing structural strain, thereby ensuring the structural stability of the negative electrode and improving the cycle performance of lithium-ion batteries, especially silicon negative electrode lithium batteries. At the same time, the aerogel has a high porosity, which can greatly improve the liquid retention capacity of the lithium battery electrode, thereby improving the cycle performance. Furthermore, the aerogel technology has thermal insulation and very high strength, which can greatly improve the safety performance of the lithium battery. DETAILED DESCRIPTION

[0030] To facilitate understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0031] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0032] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0033] Example 1:

[0034] A method for preparing a lithium battery composed of a composite negative electrode material comprises the following steps:

[0035] (1) Preparation of composite negative electrode materials:

[0036] Tetraethyl orthosilicate, acetone, anhydrous ethanol, and water were weighed in a ratio of 1:4:4:4, and thoroughly stirred and mixed. The pH value was adjusted to 3 with 18% hydrochloric acid solution, and the mixture was reacted for 10 hours. The pH value was then adjusted to 6 with aqueous ammonia, and the mixture was allowed to stand for aging for 3 days. The mixture was then soaked in anhydrous ethanol and aged at 50° C. for 1 day to obtain a silica aerogel base liquid for later use.

[0037] Then, a 15% trimethylsilyl chloride / n-hexane solution, a silicon negative electrode, and graphite negative electrode particles are fully stirred and mixed in a mass ratio of 80:2:18 to obtain a suspension containing a negative electrode active material. The suspension is added to a silica aerogel base liquid (the mass ratio of the suspension to the silica aerogel is 100:2.15), fully stirred and soaked for 2 days, dried at 55°C, soaked in acetone for 1 day to extract the n-hexane, and then dried at 55°C for 7 days to obtain a hydrophobic silica aerogel composited with a negative electrode material, i.e., a composite negative electrode aerogel; wherein the silicon negative electrode is silicon oxide or elemental nanosilicon, and the graphite negative electrode particles are artificial graphite negative electrodes;

[0038] The prepared composite negative electrode aerogel is treated under nanomolecular grinding to obtain composite negative electrode aerogel powder particles with a particle size of 8 μm-10 μm. This material is the composite negative electrode material of the present invention.

[0039] (2) Negative electrode preparation:

[0040] By weight percentage, 96.9% of composite negative electrode aerogel powder particles, 0.1% of dispersant, 1% of binder, 1% of conductive agent, and 1% of thickener are uniformly dispersed in water to prepare a negative electrode slurry, and then the negative electrode slurry is evenly coated on a current collector copper foil using a coater, and dried to remove moisture to prepare a negative electrode sheet for a lithium battery;

[0041] The dispersant is sodium polypropylene sulfonate; the binder is polyacrylic acid; the thickener is CMC; and the conductive agent is graphene.

[0042] (3) Preparation of positive electrode:

[0043] By mass percentage, 98% of active material, 1% of binder and 1% of conductive agent are uniformly dispersed in NMP, and then evenly coated on the current collector aluminum foil by coating. After drying, a lithium battery positive electrode sheet is obtained.

[0044] (4) Preparation of electrolyte:

[0045] The non-aqueous organic solution contains: EC / PC / EMC / DMC=30 / 5 / 45 / 20, and the mass percentage of this component is 83.5%;

[0046] Electrolyte: LiPF6 accounts for 14% by mass;

[0047] Additives: VC accounts for 1% by mass, PS accounts for 1% by mass, and LIODFB accounts for 0.5% by mass.

[0048] (5) Lithium battery preparation:

[0049] The sample was made by taking the soft-pack polymer lithium-ion battery 503450 as an example. The positive electrode sheet, negative electrode sheet and separator were wound into a polymer lithium-ion battery by a winding method. The lithium-ion battery was then made by pouring electrolyte, forming, evacuating and sealing.

[0050] Example 2:

[0051] A method for preparing a lithium battery composed of a composite negative electrode material comprises the following steps:

[0052] (1) Preparation of composite negative electrode materials:

[0053] Tetraethyl orthosilicate, acetone, anhydrous ethanol, and water were weighed in a ratio of 1:4:4:4, and thoroughly stirred and mixed. The pH value was adjusted to 4 with 18% hydrochloric acid solution, and the mixture was reacted for 15 hours. The pH value was then adjusted to 7 with aqueous ammonia, and the mixture was allowed to stand for aging for 3 days. The mixture was then soaked in anhydrous ethanol and aged at 50° C. for 1 day to obtain a silica aerogel base liquid for later use.

[0054] Then, a 15% trimethylsilyl chloride / n-hexane solution, a silicon negative electrode, and graphite negative electrode particles are fully stirred and mixed in a mass ratio of 80:4:16 to obtain a suspension containing a negative electrode active material. The suspension is added to a silica aerogel base liquid (the mass ratio of the suspension to the silica aerogel is 100:2.15), fully stirred and soaked for 2 days, dried at 55°C, soaked in acetone for 1 day, the n-hexane is extracted, and then dried at 55°C for 7 days to obtain a hydrophobic silica aerogel composited with a negative electrode material, i.e., a composite negative electrode aerogel; wherein the silicon negative electrode is silicon oxide or elemental nanosilicon, and the graphite negative electrode particles are artificial graphite negative electrodes;

[0055] The prepared composite negative electrode aerogel is treated under nanomolecular grinding to obtain composite negative electrode aerogel powder particles with a particle size of 8 μm-10 μm. This material is the composite negative electrode material of the present invention.

[0056] (2) Negative electrode preparation:

[0057] 96.9% of composite negative electrode aerogel powder particles, 0.1% of dispersant, 1% of binder, 1% of conductive agent, and 1% of thickener are uniformly dispersed in water to prepare a negative electrode slurry, and then the negative electrode slurry is evenly coated on the current collector copper foil using a coater, and dried to remove moisture to obtain a negative electrode sheet for a lithium battery;

[0058] The dispersant is sodium polypropylene sulfonate; the binder is polyacrylic acid; the thickener is CMC; and the conductive agent is graphene.

[0059] (3) Lithium battery preparation:

[0060] The preparation of the positive electrode sheet and electrolyte was the same as in Example 1. A sample was prepared using the soft-pack polymer lithium-ion battery 503450. The positive electrode sheet, negative electrode sheet, and separator were wound into a polymer lithium-ion battery using a winding method. The electrolyte was then poured, and the battery was prepared through steps such as formation, vacuuming, and sealing.

[0061] Example 3:

[0062] A method for preparing a lithium battery composed of a composite negative electrode material comprises the following steps:

[0063] (1) Preparation of composite negative electrode materials:

[0064] Tetraethyl orthosilicate, acetone, anhydrous ethanol, and water were weighed in a ratio of 1:4:4:4, and thoroughly stirred and mixed. The pH value was adjusted to 3 with 18% hydrochloric acid solution, and the mixture was reacted for 10 hours. The pH value was then adjusted to 6 with aqueous ammonia, and the mixture was allowed to stand for aging for 3 days. The mixture was then soaked in anhydrous ethanol and aged at 50° C. for 1 day to obtain a silica aerogel base liquid for later use.

[0065] Then, a 15% trimethylsilyl chloride / n-hexane solution, a silicon negative electrode, and graphite negative electrode particles are fully stirred and mixed in a mass ratio of 70:6:24 to obtain a suspension containing a negative electrode active material. The suspension is added to a silica aerogel base liquid (the mass ratio of the suspension to the silica aerogel is 100:2.15), fully stirred and soaked for 2 days, dried at 55°C, soaked in acetone for 1 day to extract the n-hexane, and then dried at 55°C for 7 days to obtain a hydrophobic silica aerogel composited with a negative electrode material, i.e., a composite negative electrode aerogel; wherein the silicon negative electrode is silicon dioxide or elemental nanosilicon, and the graphite negative electrode particles are artificial graphite negative electrodes;

[0066] The prepared composite negative electrode aerogel is treated under nanomolecular grinding to obtain composite negative electrode aerogel powder particles with a particle size of 8 μm-10 μm. This material is the composite negative electrode material of the present invention.

[0067] (2) Negative electrode preparation:

[0068] 96.9% of composite negative electrode aerogel powder particles, 0.1% of dispersant, 1% of binder, 1% of conductive agent, and 1% of thickener are uniformly dispersed in water to prepare a negative electrode slurry, and then the negative electrode slurry is evenly coated on the current collector copper foil using a coater, and dried to remove moisture to obtain a negative electrode sheet for a lithium battery;

[0069] The dispersant is sodium polypropylene sulfonate; the binder is polyacrylic acid; the thickener is CMC; and the conductive agent is graphene.

[0070] (3) Lithium battery preparation:

[0071] The preparation of the positive electrode sheet and electrolyte was the same as in Example 1. A sample was prepared using the soft-pack polymer lithium-ion battery 503450. The positive electrode sheet, negative electrode sheet, and separator were wound into a polymer lithium-ion battery using a winding method. The electrolyte was then poured, and the battery was prepared through steps such as formation, vacuuming, and sealing.

[0072] Example 4:

[0073] A method for preparing a lithium battery composed of a composite negative electrode material comprises the following steps:

[0074] (1) Preparation of composite negative electrode materials:

[0075] Tetraethyl orthosilicate, acetone, anhydrous ethanol, and water were weighed in a ratio of 1:4:4:4, and thoroughly stirred and mixed. The pH value was adjusted to 4 with 18% hydrochloric acid solution, and the mixture was reacted for 15 hours. The pH value was then adjusted to 7 with aqueous ammonia, and the mixture was allowed to stand for aging for 3 days. The mixture was then soaked in anhydrous ethanol and aged at 50° C. for 1 day to obtain a silica aerogel base liquid for later use.

[0076] Then, a 15% trimethylsilyl chloride / n-hexane solution, a silicon negative electrode, and graphite negative electrode particles are fully stirred and mixed in a mass ratio of 75:4:21 to obtain a suspension containing a negative electrode active material. The suspension is added to a silica aerogel base liquid (the mass ratio of the suspension to the silica aerogel is 100:2.15), fully stirred and soaked for 2 days, dried at 55°C, soaked in acetone for 1 day, the n-hexane is extracted, and then dried at 55°C for 7 days to obtain a hydrophobic silica aerogel composited with a negative electrode material, i.e., a composite negative electrode aerogel; wherein the silicon negative electrode is silicon dioxide or elemental nanosilicon, and the graphite negative electrode particles are artificial graphite negative electrodes;

[0077] The prepared composite negative electrode aerogel is treated under nanomolecular grinding to obtain composite negative electrode aerogel powder particles with a particle size of 8 μm-10 μm. This material is the composite negative electrode material of the present invention.

[0078] (2) Negative electrode preparation:

[0079] 96.9% of composite negative electrode aerogel powder particles, 0.1% of dispersant, 1% of binder, 1% of conductive agent, and 1% of thickener are uniformly dispersed in water to prepare a negative electrode slurry, and then the negative electrode slurry is evenly coated on the current collector copper foil using a coater, and dried to remove moisture to obtain a negative electrode sheet for a lithium battery;

[0080] The dispersant is sodium polypropylene sulfonate; the binder is polyacrylic acid; the thickener is CMC; and the conductive agent is graphene.

[0081] (3) Lithium battery preparation:

[0082] The preparation of the positive electrode sheet and electrolyte was the same as in Example 1. A sample was prepared using the soft-pack polymer lithium-ion battery 503450. The positive electrode sheet, negative electrode sheet, and separator were wound into a polymer lithium-ion battery using a winding method. The electrolyte was then poured, and the battery was prepared through steps such as formation, vacuuming, and sealing.

[0083] Example 5:

[0084] A method for preparing a lithium battery composed of a composite negative electrode material comprises the following steps:

[0085] (1) Preparation of composite negative electrode materials:

[0086] Tetraethyl orthosilicate, acetone, anhydrous ethanol, and water were weighed in a ratio of 1:4:4:4, and thoroughly stirred and mixed. The pH value was adjusted to 3 with 18% hydrochloric acid solution, and the mixture was reacted for 10 hours. The pH value was then adjusted to 6 with aqueous ammonia, and the mixture was allowed to stand for aging for 3 days. The mixture was then soaked in anhydrous ethanol and aged at 50° C. for 1 day to obtain a silica aerogel base liquid for later use.

[0087] Then, a 15% trimethylsilyl chloride / n-hexane solution, a silicon negative electrode, and graphite negative electrode particles are fully stirred and mixed in a mass ratio of 85:1:14 to obtain a suspension containing a negative electrode active material. The suspension is added to a silica aerogel base liquid (the mass ratio of the suspension to the silica aerogel is 100:2.15), fully stirred and soaked for 2 days, dried at 55°C, and then soaked in acetone for 1 day to extract the n-hexane. The hydrophobic silica aerogel composited with the negative electrode material, i.e., a composite negative electrode aerogel, is obtained; wherein the silicon negative electrode is silicon oxide or elemental nanosilicon, and the graphite negative electrode particles are artificial graphite negative electrodes;

[0088] The prepared composite negative electrode aerogel is treated under nanomolecular grinding to obtain composite negative electrode aerogel powder particles with a particle size of 8 μm-10 μm. This material is the composite negative electrode material of the present invention.

[0089] (2) Negative electrode preparation:

[0090] 96.9% of composite negative electrode aerogel powder particles, 0.1% of dispersant, 1% of binder, 1% of conductive agent, and 1% of thickener are uniformly dispersed in water to prepare a negative electrode slurry, and then the negative electrode slurry is evenly coated on the current collector copper foil using a coater, and dried to remove moisture to obtain a negative electrode sheet for a lithium battery;

[0091] The dispersant is sodium polypropylene sulfonate; the binder is polyacrylic acid; the thickener is CMC; and the conductive agent is graphene.

[0092] (3) Lithium battery preparation:

[0093] The preparation of the positive electrode sheet and electrolyte was the same as in Example 1. A sample was prepared using the soft-pack polymer lithium-ion battery 503450. The positive electrode sheet, negative electrode sheet, and separator were wound into a polymer lithium-ion battery using a winding method. The electrolyte was then poured, and the battery was prepared through steps such as formation, vacuuming, and sealing.

[0094] Example 6:

[0095] A method for preparing a lithium battery composed of a composite negative electrode material comprises the following steps:

[0096] (1) Preparation of composite negative electrode materials:

[0097] Tetraethyl orthosilicate, acetone, anhydrous ethanol, and water were weighed in a ratio of 1:4:4:4, and thoroughly stirred and mixed. The pH value was adjusted to 4 with 18% hydrochloric acid solution, and the mixture was reacted for 15 hours. The pH value was then adjusted to 7 with aqueous ammonia, and the mixture was allowed to stand for aging for 3 days. The mixture was then soaked in anhydrous ethanol and aged at 50° C. for 1 day to obtain a silica aerogel base liquid for later use.

[0098] Then, a 15% trimethylsilyl chloride / n-hexane solution, a silicon negative electrode, and graphite negative electrode particles are fully stirred and mixed in a mass ratio of 85:2:13 to obtain a suspension containing a negative electrode active material. The suspension is added to a silica aerogel base liquid (the mass ratio of the suspension to the silica aerogel is 100:2.15), fully stirred and soaked for 2 days, dried at 55°C, and then soaked in acetone for 1 day to extract the n-hexane. The hydrophobic silica aerogel composited with the negative electrode material, i.e., a composite negative electrode aerogel, is obtained; wherein the silicon negative electrode is silicon oxide or elemental nanosilicon, and the graphite negative electrode particles are artificial graphite negative electrodes;

[0099] The prepared composite negative electrode aerogel is treated under nanomolecular grinding to obtain composite negative electrode aerogel powder particles with a particle size of 8 μm-10 μm. This material is the composite negative electrode material of the present invention.

[0100] (2) Negative electrode preparation:

[0101] 96.9% of composite negative electrode aerogel powder particles, 0.1% of dispersant, 1% of binder, 1% of conductive agent, and 1% of thickener are uniformly dispersed in water to prepare a negative electrode slurry, and then the negative electrode slurry is evenly coated on the current collector copper foil using a coater, and dried to remove moisture to obtain a negative electrode sheet for a lithium battery;

[0102] The dispersant is sodium polypropylene sulfonate; the binder is polyacrylic acid; the thickener is CMC; and the conductive agent is graphene.

[0103] (3) Lithium battery preparation:

[0104] The preparation of the positive electrode sheet and electrolyte was the same as in Example 1. A sample was prepared using the soft-pack polymer lithium-ion battery 503450. The positive electrode sheet, negative electrode sheet, and separator were wound into a polymer lithium-ion battery using a winding method. The electrolyte was then poured, and the battery was prepared through steps such as formation, vacuuming, and sealing.

[0105] The only difference between the traditional scheme and the present invention is that the negative electrode material used is prepared by the following method: 97% of the active material graphite negative electrode, 1% of the conductive agent, 1% of the binder, and 1% of the thickener are uniformly dispersed in water by double planetary stirring to prepare a negative electrode slurry suspension; the active material is graphite; the conductive agent is graphene; the binder is polyacrylic acid; and the thickener is CMC.

[0106] The performance characteristics of the lithium batteries prepared in Examples 1-6 are shown in Table 1.

[0107] Table 1: Performance characteristics of lithium batteries prepared in Examples 1-6

[0108] sample Negative electrode capacity in grams First efficiency Fluid retention rate Battery internal resistance cycle Traditional solution 405mAh / g 90.2％ 0.18％ 21.2mΩ 83.0%@1000CL Example 1 411mAh / g 92.3％ 0.25％ 18.9mΩ 90.2%@1000CL Example 2 425mAh / g 91.3％ 0.28％ 17.8mΩ 88.3%@1000CL Example 3 423mAh / g 91.6％ 0.29％ 18.6mΩ 87.2%@1000CL Example 4 416mAh / g 92.1％ 0.26％ 19.2mΩ 89.5%@1000CL Example 5 418mAh / g 92.4％ 0.29％ 19.5mΩ 89.9%@1000CL Example 6 420mAh / g 91.9％ 0.22％ 19.9mΩ 86.8%@1000CL

[0109] As can be seen from Table 1, the present invention embeds the negative electrode material into the aerogel frame to prepare the lithium battery negative electrode active material, negative electrode sheet and lithium battery. Such aerogel composite negative electrode technology can increase the liquid retention capacity of the lithium battery, alleviate the structural damage caused by structural expansion, and enhance the cycle performance of the lithium battery.

Claims

1. A composite negative electrode material, characterized in that It is mainly composed of a silicon negative electrode, a graphite negative electrode and a silicon oxide aerogel, wherein the mass ratio of the silicon negative electrode, the graphite negative electrode and the silicon oxide aerogel is 8-10:86-90:2-4, and the particle size of the composite negative electrode material is 1μm-15μm; The composite negative electrode material is prepared by the following method: (1) Preparing a silica aerogel base liquid; the preparation method of the silica aerogel base liquid is as follows: ethyl orthosilicate, acetone, anhydrous ethanol, and water are uniformly mixed in a mass ratio of 1-2:4-5:4-5:4-6, the pH value is adjusted to 3-4, and the reaction is carried out for 10-20 hours, and then the pH value is adjusted to 6-7 with ammonia water, and then the reaction is allowed to stand for 2-3 days, and then the reaction is soaked in anhydrous ethanol and heated at 45-55°C for 1-2 days to obtain a silica aerogel base liquid; (2) a trimethylchlorosilane / n-hexane mixed solution, a silicon negative electrode, and graphite negative electrode particles are uniformly mixed to prepare a suspension containing a negative electrode active material, the suspension is added to the silica aerogel base liquid, fully stirred and soaked for reaction, dried once and then soaked in acetone to extract the n-hexane, and then dried twice to obtain a hydrophobic silica aerogel composited with the negative electrode material, i.e., a composite negative electrode aerogel; the mass concentration of the trimethylchlorosilane / n-hexane mixed solution is 10-15%; the mass ratio of the trimethylchlorosilane / n-hexane mixed solution, the silicon negative electrode, and the graphite negative electrode particles is 70-85:1-6:13-24; the mass ratio of the suspension to the silica aerogel is 100:2-4; (3) The composite negative electrode aerogel is subjected to nanomolecular grinding treatment to obtain micron-scale powder particles, which are the composite negative electrode material.

2. The composite negative electrode material according to claim 1, characterized in that The mass ratio of the silicon negative electrode, the graphite negative electrode and the silicon oxide aerogel is 9:88:

3.

3. The composite negative electrode material according to claim 1, characterized in that The silicon negative electrode is silicon oxide or elemental nano-silicon, and the graphite negative electrode is an artificial graphite negative electrode.

4. A method for preparing a composite negative electrode material, characterized in that: The steps include: (1) Preparing a silica aerogel base liquid; the preparation method of the silica aerogel base liquid is as follows: ethyl orthosilicate, acetone, anhydrous ethanol, and water are uniformly mixed in a mass ratio of 1-2:4-5:4-5:4-6, the pH value is adjusted to 3-4, and the reaction is carried out for 10-20 hours, and then the pH value is adjusted to 6-7 with ammonia water, and then the reaction is allowed to stand for 2-3 days, and then the reaction is soaked in anhydrous ethanol and heated at 45-55°C for 1-2 days to obtain a silica aerogel base liquid; (2) a trimethylchlorosilane / n-hexane mixed solution, a silicon negative electrode, and graphite negative electrode particles are uniformly mixed to prepare a suspension containing a negative electrode active material, the suspension is added to the silica aerogel base liquid, fully stirred and soaked for reaction, dried once and then soaked in acetone to extract the n-hexane, and then dried twice to obtain a hydrophobic silica aerogel composited with the negative electrode material, i.e., a composite negative electrode aerogel; the mass concentration of the trimethylchlorosilane / n-hexane mixed solution is 10-15%; the mass ratio of the trimethylchlorosilane / n-hexane mixed solution, the silicon negative electrode, and the graphite negative electrode particles is 70-85:1-6:13-24; the mass ratio of the suspension to the silica aerogel is 100:2-4; (3) The composite negative electrode aerogel is subjected to nanomolecular grinding treatment to obtain micron-scale powder particles, which are the composite negative electrode material.

5. The preparation method according to claim 4, characterized in that In step (2), the soaking reaction time is 2-3 days; the temperature of the primary drying and secondary drying is 50-60° C.; the acetone soaking time is 1-2 days; and the secondary drying time is 5-7 days.

6. A negative electrode sheet comprising a current collector and a negative electrode slurry coated on the surface of the current collector, characterized in that: The negative electrode slurry comprises the composite negative electrode material according to any one of claims 1 to 3 or the composite negative electrode material prepared by the preparation method according to claim 4 or 5.

7. A lithium battery, characterized in that: The invention comprises the negative electrode sheet, the positive electrode sheet, the separator and the electrolyte as claimed in claim 6.