Silicon-carbon anode for improving the cycle expansion of silicon-carbon anode battery and preparation method and application thereof

Abstract

The application provides a silicon-carbon negative electrode for improving cycle expansion of a silicon-carbon negative electrode battery. The silicon-carbon negative electrode material coated with graphene is combined with a graphene-coated copper foil to form a synergistic effect, and the unique properties of graphene are used to improve the cycle expansion of the silicon-carbon negative electrode. Due to the van der Waals force between the graphene coating and the graphene coated outside the silicon-carbon negative electrode and the organosilicon functional group, the adhesion between the silicon-carbon negative electrode and the current collector is greatly enhanced, and the active material of the silicon-carbon negative electrode can be reduced from the current collector to form a gap during the cycle process, thereby effectively improving the overall expansion of the battery. At the same time, due to the excellent conductivity of graphene, the cycle of the battery can also be improved. The results show that the battery with the graphene-coated copper foil and the battery without the coating, the cycle expansion of the silicon-carbon negative electrode battery is obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of silicon-carbon anode battery technology, specifically relating to a silicon-carbon anode that improves the cycle expansion of silicon-carbon anode batteries, as well as its preparation method and application. Background Technology

[0002] Since the 1990s, the successful development and application of lithium-ion batteries have spread to various industries. They have played a particularly significant role in consumer electronics, electric vehicles, and energy storage, promoting rapid societal development. However, as consumer demands continue to rise, the performance requirements for lithium-ion batteries are becoming increasingly stringent, especially regarding energy density. Currently, the vast majority of commercially available lithium-ion battery anode materials are graphite. Its theoretical specific capacity is 372 mAh / g, but in practical applications it reaches around 360 mAh / g, almost reaching its theoretical limit. In contrast, we have found that silicon has a theoretical specific capacity of 4200 mAh / g, far exceeding that of graphite, making it a very promising anode material. However, due to its extremely high capacity, pure silicon undergoes a massive volume expansion (up to 300%) during lithium intercalation, leading to a rapid capacity decay. Currently, various methods are being used to modify silicon, including preparing silicon suboxide (SiO2). x Silicon is then combined with carbon to form a silicon-carbon anode, which has significantly reduced battery expansion, but it still falls short of the requirements for practical applications. Therefore, the expansion of silicon anodes has become an urgent problem to be solved for the application of silicon in lithium-ion batteries.

[0003] By reviewing the literature, it was found that there are also solutions to improve the cycle life of silicon-carbon anodes by using current collectors. One solution is to use laser etching to penetrate copper foil and form a porous structure with micron-scale pores. At the same time, many barbs are formed on the surface of the pores. These barbs are used to fix the active material on the current collector, thereby reducing the expansion of the entire battery.

[0004] Existing porous copper foil structures are prone to leakage through the pores during the coating process if the slurry viscosity is low, leading to uneven areal density. Furthermore, due to the relatively long barbs, when the coating thickness is small, the barbs protrude from the coated electrode surface, forming burrs, which is detrimental to battery safety. Additionally, the presence of micropores increases the impedance of the negative electrode, hindering battery cycle life. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a silicon-carbon anode that improves the cycling expansion of silicon-carbon anode batteries, as well as a preparation method and application. The present invention greatly enhances the adhesion between the silicon-carbon anode and the current collector, and can reduce the loss of active material of silicon-carbon anode from the current collector to form voids during cycling, thereby effectively improving the overall expansion of the battery.

[0006] This invention provides a silicon-carbon anode that improves the cycling expansion of silicon-carbon anode batteries, comprising:

[0007] current collector;

[0008] A graphene coating is applied to the surface of the current collector;

[0009] A negative electrode material layer is composited on the surface of the graphene coating, the negative electrode material layer comprising graphene-coated silicon-carbon negative electrode material.

[0010] Preferably, the current collector is selected from copper foil, copper mesh, or copper foam, and has a thickness of 5–20 μm.

[0011] Preferably, the graphene coating is applied to both sides of the current collector, wherein the coating thickness on each side is 1–20 μm.

[0012] Preferably, the thickness of the negative electrode material layer is 30–100 μm, and the areal density is 5–10 mg / cm³. 2 .

[0013] The present invention also provides a method for preparing the above-mentioned silicon-carbon anode, comprising the following steps:

[0014] A) Graphene slurry is coated onto the surface of the current collector to obtain a current collector with a graphene coating.

[0015] B) The negative electrode material slurry is coated onto the surface of the graphene coating to obtain a silicon-carbon negative electrode;

[0016] The negative electrode material slurry includes graphene-coated silicon-carbon negative electrode material.

[0017] Preferably, the graphene slurry comprises:

[0018] 4 to 8 parts by mass of graphene;

[0019] 1 to 2 parts by weight of conductive material;

[0020] 6-7 parts by weight of adhesive;

[0021] 80-85 parts by weight of solvent.

[0022] Preferably, the negative electrode material slurry comprises:

[0023] 15-25 parts by weight of graphene-coated silicon-carbon anode material;

[0024] 75-85 parts by weight of graphite anode material;

[0025] 0.01 to 1 part by weight of conductive material;

[0026] 3 to 6 parts by weight of adhesive;

[0027] 150 to 250 parts by weight of solvent.

[0028] Preferably, in step A), the coating method is one or more of the following: doctor blade coating, roller transfer coating, slot extrusion coating, and gravure printing.

[0029] Preferably, in step B), the coating method is one or more of the following: blade coating, roller transfer coating, and slot extrusion coating.

[0030] The present invention also provides a silicon-carbon anode battery, comprising the aforementioned silicon-carbon anode.

[0031] Compared with the prior art, the present invention provides a silicon-carbon anode that improves the cycle expansion of silicon-carbon anode batteries, comprising: a current collector; a graphene coating composited on the surface of the current collector; and an anode material layer composited on the surface of the graphene coating, wherein the anode material layer comprises graphene-coated silicon-carbon anode material.

[0032] This invention combines graphene-coated silicon-carbon anode material with graphene-coated copper foil to create a synergistic effect, leveraging the unique properties of graphene to improve the cycling expansion of the silicon-carbon anode. Due to the van der Waals forces and functional groups between the graphene coating and the graphene coating on the silicon-carbon anode, the adhesion between the silicon-carbon anode and the current collector is greatly enhanced. During cycling, this reduces the amount of active material from the silicon-carbon anode detaching from the current collector, thus reducing voids and effectively improving the overall battery expansion. Simultaneously, the excellent conductivity of graphene also improves battery cycling. Results show that the cycling expansion of silicon-carbon anode batteries is significantly improved in batteries with graphene-coated copper foil compared to uncoated batteries. Attached Figure Description

[0033] Figure 1 A process flow diagram for the fabrication of silicon-carbon anode batteries provided by the present invention;

[0034] Figure 2 A photograph of the current collector with a graphene coating prepared in Example 1;

[0035] Figure 3 The results are from the electrode peeling force test. Detailed Implementation

[0036] This invention provides a silicon-carbon anode that improves the cycling expansion of silicon-carbon anode batteries, comprising:

[0037] current collector;

[0038] A graphene coating is applied to the surface of the current collector;

[0039] A negative electrode material layer is composited on the surface of the graphene coating, the negative electrode material layer comprising graphene-coated silicon-carbon negative electrode material.

[0040] The silicon-carbon anode provided by the present invention includes a current collector, wherein the current collector is selected from copper foil, copper mesh, or copper foam, and has a thickness of 5 to 20 μm, preferably 5, 10, 15, or 20 μm, or any value between 5 and 20 μm.

[0041] A graphene coating is laminated on the surface of the current collector. In this invention, the graphene coating is laminated on both sides of the current collector, wherein the coating thickness on each side is 1 to 20 μm, preferably 1, 3, 5, 7, 10, 12, 15, 18, 20, or any value between 1 and 20 μm.

[0042] The silicon-carbon anode provided by this invention further includes an anode material layer. The anode material layer comprises graphene-coated silicon-carbon anode material. The thickness of the anode material layer is 30–100 μm, preferably 30, 40, 50, 60, 70, 80, 90, or 100 μm, or any value between 30 and 100 μm, and the areal density is 5–10 mg / cm³. 2 Preferably, the concentrations are 5, 6, 7, 8, 9, or 10, or 5–10 mg / cm³. 2 Any value between.

[0043] In this invention, the graphene-coated silicon-carbon anode material is prepared according to the following method:

[0044] SiO x Bulk materials are processed into coarse and fine powders to obtain D50 1~5μm SiO2. x Powdered materials yield SiO x Precursor body;

[0045] Then SiO x The precursor, dispersant, additives, and graphene slurry are uniformly dispersed and mixed, dried, and granulated to obtain SiO2. x -G precursor;

[0046] SiO x The -G precursor is placed under an inert atmosphere and heated to 700-1000℃ per minute for carbonization. After sieving and iron removal, graphene-coated silicon-carbon anode material is obtained.

[0047] The dispersant is selected from one or more of polyethylene glycol, polyacryl alcohol, Tween-60, Tween-80, sodium dodecyl sulfonate, and sodium dodecyl sulfate.

[0048] The additive is selected from one or more of polyacrylamide, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, melamine-formaldehyde resin, acetic acid, and lithium acetate;

[0049] The SiO x The mass ratio of the precursor to the dispersant, additives, and graphene slurry is 6–40:0.1–0.3:0.5–1:100;

[0050] The inert atmosphere is selected from one or more of nitrogen, argon, and helium.

[0051] This invention involves coating a thin layer of graphene onto the surface of copper foil, resulting in a smooth surface that avoids issues such as material leakage and burrs. Furthermore, the van der Waals forces between graphene atoms, as well as the organic functional groups, create a strong bond between the graphene-coated silicon-carbon and the graphene-coated copper foil, thereby enhancing conductivity. This synergistic effect significantly improves the cycle life of silicon-carbon batteries.

[0052] The present invention also provides a method for preparing the above-mentioned silicon-carbon anode, comprising the following steps:

[0053] A) Graphene slurry is coated onto the surface of the current collector to obtain a current collector with a graphene coating.

[0054] B) The negative electrode material slurry is coated onto the surface of the graphene coating to obtain a silicon-carbon negative electrode;

[0055] The negative electrode material slurry includes graphene-coated silicon-carbon negative electrode material.

[0056] The present invention first coats the surface of the current collector with graphene slurry to obtain a current collector with a graphene coating.

[0057] The graphene slurry includes:

[0058] 4 to 8 parts by mass of graphene;

[0059] 1 to 2 parts by weight of conductive material;

[0060] 6-7 parts by weight of adhesive;

[0061] 80-85 parts by mass of solvent.

[0062] The graphene slurry provided by the present invention comprises 4 to 8 parts by weight of graphene, preferably 4, 5, 6, 7, or 8 parts by weight, or any value between 4 and 8 parts by weight.

[0063] The graphene slurry provided by this invention further includes 1 to 2 parts by weight of a conductive material, preferably 1, 1.5, 2, or any value between 1 and 2 parts by weight. The conductive material is selected from activated carbon.

[0064] The graphene slurry provided by this invention further includes 6 to 7 parts by weight of a binder, preferably 6, 6.5, 7, or any value between 6 and 7 parts by weight. The binder is selected from one or more of polyacrylic acid (PAA) and styrene-butadiene rubber (SBR).

[0065] The graphene slurry provided by this invention further includes 80-85 parts by weight of solvent, preferably 80, 81, 82, 83, 84, or 85 parts by weight, or any value between 80 and 85 parts by weight. The solvent is selected from deionized water.

[0066] The present invention mixes graphene, conductive material, binder and solvent to obtain graphene slurry, wherein the solid content of the graphene slurry is 13-15%.

[0067] After obtaining the graphene slurry, it is coated onto both sides of the current collector using a coating method. After drying, a current collector with a graphene coating is obtained. The coating methods include blade coating, roller coating, slot extrusion coating, and gravure printing.

[0068] The present invention does not impose any special restrictions on the drying method; any drying method known to those skilled in the art is acceptable.

[0069] Next, the negative electrode material slurry is coated onto the surface of the graphene coating to obtain a silicon-carbon negative electrode.

[0070] The negative electrode material slurry includes:

[0071] 15-25 parts by weight of graphene-coated silicon-carbon anode material;

[0072] 75-85 parts by weight of graphite anode material;

[0073] 0.01 to 1 part by weight of conductive material;

[0074] 3 to 6 parts by weight of adhesive;

[0075] 150 to 250 parts by weight of solvent.

[0076] The negative electrode material slurry provided by the present invention comprises 15 to 25 parts by weight of graphene-coated silicon-carbon negative electrode material, preferably 15, 17, 20, 22, 25, or any value between 15 and 25 parts by weight.

[0077] The graphene-coated silicon-carbon anode material is a graphene composite silicon-carbon anode material, which is obtained by drying and granulating graphene and silicon particles in a certain proportion and a certain particle size ratio, and then carbonizing them under inert gas conditions.

[0078] The negative electrode material slurry provided by the present invention further includes 75 to 85 parts by weight of graphite negative electrode material, preferably 75, 78, 80, 82, 85, or any value between 75 and 85 parts by weight.

[0079] The negative electrode material slurry provided by the present invention further includes 0.01 to 1 part by weight of conductive material, preferably 0.01, 0.05, 0.1, 0.2, 0.5, 0.8, 1, or any value between 0.01 and 1 part by weight. The conductive material is selected from one or more of graphite, conductive carbon black, and single-walled carbon nanotubes.

[0080] The negative electrode material slurry provided by the present invention further includes 3 to 6 parts by weight of a binder, preferably 3, 4, 5, or 6 parts by weight, or any value between 3 and 6 parts by weight. The binder is selected from one or more of polyacrylic acid (PAA), sodium carboxymethyl cellulose (CMC), polyvinyl chloride (PVP), styrene-butadiene rubber (SBR), and polyacrylonitrile.

[0081] The negative electrode material slurry provided by the present invention further includes 150 to 250 parts by weight of solvent, preferably 150, 180, 200, 220, 250, or any value between 150 and 250 parts by weight. The solvent is selected from deionized water and an ethanol solution of water.

[0082] The graphene-coated silicon-carbon anode material, conductive material, binder, and solvent are mixed to obtain an anode material slurry.

[0083] Then, the negative electrode material slurry is coated onto the surface of the graphene coating, and after drying, a silicon-carbon negative electrode is obtained.

[0084] The coating method is one or more of the following: blade coating, roller transfer coating, and slot extrusion coating.

[0085] The present invention does not impose any special restrictions on the drying method; any drying method known to those skilled in the art is acceptable.

[0086] The present invention also provides a silicon-carbon anode battery, comprising the aforementioned silicon-carbon anode.

[0087] This invention does not impose any special restrictions on the structure of the silicon-carbon anode battery other than the silicon-carbon anode; any structure known to those skilled in the art can be used.

[0088] The present invention does not impose any special limitations on the preparation method of the silicon-carbon anode battery; any method known to those skilled in the art is acceptable.

[0089] See Figure 1 , Figure 1 A process flow diagram for the fabrication of silicon-carbon anode batteries provided by this invention.

[0090] The van der Waals forces and organic functional groups between graphene atoms can increase the bonding force between them, thus tightly binding the graphene-coated silicon-carbon anode to the graphene-coated current collector. This prevents the silicon-carbon anode from detaching from the current collector due to excessive volume changes during cycling, ensuring good electrical contact and reducing battery expansion. Simultaneously, graphene's excellent conductivity also benefits battery cycling.

[0091] In this invention, the combination of graphene-coated copper foil and graphene-coated silicon carbon, through the van der Waals forces between graphene and the interaction of organic functional groups, suppresses the cyclic expansion of the silicon carbon anode, thereby improving the cycle life of the silicon carbon anode battery.

[0092] To further understand the present invention, the following description, in conjunction with embodiments, illustrates the silicon-carbon anode for improving the cycle expansion of silicon-carbon anode batteries, its preparation method, and its application. The scope of protection of the present invention is not limited by the following embodiments.

[0093] In the following embodiments, the preparation method of graphene-coated silicon-carbon anode material is as follows:

[0094] SiO x Bulk materials are processed into coarse and fine powders to obtain D50 2μm SiO₂. x Powdered materials yield SiO x Precursor body;

[0095] Then SiO x The precursor was uniformly dispersed and mixed with polyethylene glycol, sodium carboxymethyl cellulose, and graphene slurry at a mass ratio of 30:0.2:0.6:100, dried, and granulated to obtain SiO₂. x -G precursor;

[0096] SiO x The -G precursor is placed under nitrogen protection and heated to 700-1000℃ per minute for carbonization. After sieving and iron removal, graphene-coated silicon-carbon anode material is obtained.

[0097] Example 1

[0098] The graphene slurry comprises: 8% graphene (solid content), 1% CNTs, 7% binder, and 84% NMP solvent.

[0099] The silicon-carbon anode slurry comprises: 30 parts by weight of graphene-coated silicon-carbon anode material, 64 parts by weight of graphite, 1.5 parts by weight of conductive carbon black, 0.05 parts by weight of single-walled carbon nanotubes, 3 parts by weight of PAA, 1 part by weight of SBR, 1.45 parts by weight of sodium carboxymethyl cellulose (CMC), and 160 parts by weight of deionized water.

[0100] A graphene coating with a double-sided thickness of 3 μm was coated onto an 8 μm thick copper foil to obtain a current collector with a composite graphene coating. See also Figure 2 , Figure 2 This is a photograph of the current collector with a graphene coating prepared in Example 1.

[0101] Then, the silicon-carbon anode slurry is coated onto the current collector, with a coating surface density of 7.5 mg / cm³. 2 The coating thickness is 60μm. The negative electrode sheet is then obtained by roll forming and slitting.

[0102] Calculate the required weight of lithium cobalt oxide positive electrode active material for the corresponding positive electrode based on a 5% excess capacity of the negative electrode, and set the areal density of the positive electrode coating to 20 mg / cm³. 2 The positive electrode slurry was coated onto 9μm aluminum foil using a coating machine, dried, and then rolled and slit to obtain positive electrode sheets. After baking, the positive and negative electrode sheets were die-cut, stacked, and had tabs welded. They were then encapsulated in an aluminum-plastic shell, injected with LiPF6 / EC-DMC-EMC (volume ratio 1:1:1) electrolyte, formed, aged, and sealed by degassing. After the battery was fabricated, it was cycled at room temperature at a 0.5C charge / 0.5C discharge rate. The thickness of the battery in its initial fully charged state was measured, and the thickness was measured again after cycling. The battery thickness expansion rate during cycling was calculated based on the initial thickness, and the results are shown in Table 1. Table 1 shows that the thickness expansion rates of the graphene-coated current collector and the uncoated current collector were 12.8% and 14.7% respectively during the first fully charged cycle, a reduction of 13%; after 300 cycles, the thickness expansion rates were 10.4% and 12.2% respectively, a reduction of 15%. It is evident that graphene-coated current collectors can effectively improve the cyclic expansion of silicon-carbon anode batteries.

[0103] Example 2

[0104] The graphene slurry comprises: 8% graphene (solid content), 1% CNTs, 7% binder, and 84% NMP solvent.

[0105] The silicon-carbon anode slurry comprises: 25% graphene-coated silicon-carbon anode material, 69% graphite, 1.5% conductive carbon black, 0.05% single-walled carbon nanotubes, 3% PAA, 1% SBR, 1.45% sodium carboxymethyl cellulose (CMC), and 170% deionized water.

[0106] A 3μm thick double-sided graphene coating is applied to an 8μm thick copper foil. Then, a silicon-carbon anode is coated onto the current collector, resulting in a coating surface density of 7.5 mg / cm³. 2 The coating thickness is 60μm. The negative electrode sheet is then obtained by roll forming and slitting.

[0107] The battery was prepared in the same manner as in Example 1.

[0108] After fabrication, the batteries were cycled at room temperature using a 0.5C charge / 0.5C discharge rate. The thickness of the battery in its initial fully charged state was measured, and the thickness was measured again after each cycle. The battery thickness expansion rate during the cycle was calculated based on the initial thickness, and the results are shown in Table 1. We can see that the thickness expansion rates of the graphene-coated current collector and the uncoated current collector were 11.2% and 14.7% respectively during the first fully charged cycle, a reduction of 24%. After 300 cycles, the thickness expansion rates were 9.8% and 12.2% respectively, a reduction of 20%.

[0109] Example 3

[0110] The graphene slurry comprises: 8% graphene (solid content), 1% CNTs, 7% binder, and 84% NMP solvent.

[0111] The silicon-carbon anode slurry comprises: 20 parts by weight of graphene-coated silicon-carbon anode material, 74 parts by weight of graphite, 1.5 parts by weight of conductive carbon black, 0.05 parts by weight of single-walled carbon nanotubes, 2 parts by weight of PAA, 1 part by weight of SBR, 1.45 parts by weight of sodium carboxymethyl cellulose (CMC), and 180 parts by weight of deionized water.

[0112] A 3μm thick double-sided graphene coating is applied to an 8μm thick copper foil. Then, a silicon-carbon anode is coated onto the current collector, with a coating surface density of 8 mg / cm³. 2 The coating thickness is 65μm. The negative electrode sheet is then obtained by roll forming and slitting.

[0113] The battery was prepared in the same manner as in Example 1.

[0114] After being fabricated into batteries, they were cycled at room temperature using a 0.5C charge / 0.5C discharge rate. The thickness of the battery in its initial fully charged state was measured, and the thickness was measured again after each cycle. The battery thickness expansion rate during the cycle was calculated based on the initial thickness, and the results are shown in Table 1. From this, we can see that the thickness expansion rates of the batteries with graphene-coated current collectors and those without are 9.8% and 14.7% respectively during the first fully charged cycle, representing a 33% reduction in thickness expansion. After 300 cycles, the thickness expansion rates are 9.3% and 12.2% respectively, representing a 24% reduction in thickness expansion.

[0115] Example 4

[0116] The graphene slurry comprises: 8% graphene (solid content), 1% CNTs, 7% binder, and 84% NMP solvent.

[0117] The silicon-carbon anode slurry comprises: 20 parts by weight of graphene-coated silicon-carbon anode material, 74 parts by weight of graphite, 1.5 parts by weight of conductive carbon black, 0.05 parts by weight of single-walled carbon nanotubes, 2 parts by weight of PAA, 1 part by weight of SBR, 1.45 parts by weight of sodium carboxymethyl cellulose (CMC), and 200 parts by weight of deionized water.

[0118] A graphene coating with a double-sided thickness of 4 μm was applied to an 8 μm thick copper foil. Then, a silicon-carbon anode was coated onto the current collector, with a coating surface density of 8 mg / cm³. 2 The coating thickness is 65μm. The negative electrode sheet is then obtained by roll forming and slitting.

[0119] The battery was prepared in the same manner as in Example 1.

[0120] After being fabricated into batteries, they were cycled at room temperature using a 0.5C charge / 0.5C discharge rate. The thickness of the battery in its initial fully charged state was measured, and the thickness was measured again after each cycle. The battery thickness expansion rate during the cycle was calculated based on the initial thickness, and the results are shown in Table 1. From this, we can see that the thickness expansion rates of the batteries with graphene-coated current collectors and those without are 9.4% and 14.7% respectively during the first fully charged cycle, representing a 36% reduction in thickness expansion. After 300 cycles, the thickness expansion rates are 9.2% and 12.2% respectively, representing a 25% reduction in thickness expansion.

[0121] Example 5

[0122] The graphene slurry comprises: 8% graphene (solid content), 1% CNTs, 7% binder, and 84% NMP solvent.

[0123] The silicon-carbon anode slurry comprises: 20 parts by mass of graphene-coated silicon-carbon anode material, 74 parts by mass of graphite, 1.5 parts by mass of conductive carbon black, 0.05 parts by mass of single-walled carbon nanotubes, 2 parts by mass of PAA, 1 part by mass of SBR, 1.45 parts by mass of sodium carboxymethyl cellulose (CMC), and 160 parts by mass of deionized water.

[0124] A graphene coating with a double-sided coating thickness of 5 μm was applied to an 8 μm thick copper foil. Then, a silicon-carbon anode was coated onto the current collector, with a coating surface density of 8 mg / cm³. 2 The coating thickness is 65μm. The negative electrode sheet is then obtained by roll forming and slitting.

[0125] The battery was prepared in the same manner as in Example 1.

[0126] After being fabricated, the batteries were cycled at room temperature using a 0.5C charge / 0.5C discharge rate. The thickness of the battery in its initial fully charged state was measured, and the thickness was measured again after each cycle. The battery thickness expansion rate during the cycle was calculated based on the initial thickness, and the results are shown in Table 1. We can see that the thickness expansion rates of the graphene-coated current collector and the uncoated current collector were 9.1% and 14.7% respectively during the first fully charged cycle, representing a 38% reduction in thickness expansion. After 300 cycles, the thickness expansion rates were 9.2% and 12.2% respectively, representing a 24% reduction in thickness expansion.

[0127] Comparative Example 1

[0128] The silicon-carbon anode slurry comprises: 20 parts by mass of graphene-coated silicon-carbon anode material, 74 parts by mass of graphite, 1.5 parts by mass of conductive carbon black, 0.05 parts by mass of single-walled carbon nanotubes, 2 parts by mass of PAA, 1 part by mass of SBR, 1.45 parts by mass of sodium carboxymethyl cellulose (CMC), and 190 parts by mass of deionized water.

[0129] Then, the silicon-carbon anode is coated onto the current collector, with a coating surface density of 8 mg / cm². 2 The coating thickness is 65μm. The negative electrode sheet is then obtained by roll forming and slitting.

[0130] The battery was prepared in the same manner as in Example 1.

[0131] After rolling the negative electrode sheets obtained in Comparative Example 1 and Example 5, a peel force test was performed to compare the adhesion between the two groups of negative electrode active materials and current collectors. The test results are shown in the appendix. Figure 3 The results show that the graphene-coated current collector has a larger negative electrode peel force, indicating that its adhesion is significantly better than that of the conventional copper foil current collector, providing a basis for subsequent experiments.

[0132] Table 1

[0133]

[0134] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A silicon-carbon anode for improving the cycle expansion of silicon-carbon anode batteries, characterized in that, include: current collector; A graphene coating is applied to the surface of the current collector, wherein the graphene coating is applied to both sides of the current collector, and the coating thickness on each side is 1~20μm; A negative electrode material layer composited on the surface of the graphene coating, the negative electrode material layer comprising graphene-coated silicon-carbon negative electrode material, the thickness of the negative electrode material layer being 30~100μm; The graphene-coated silicon-carbon anode material is prepared according to the following method: SiO x Bulk materials are processed into coarse and fine powders to obtain D50 1~5μm SiO₂. x Powdered materials yield SiO x Precursor body; Then SiO x The precursor, dispersant, additives, and graphene slurry are uniformly dispersed and mixed, dried, and granulated to obtain SiO2. x -G precursor; SiO x The -G precursor is placed under an inert atmosphere and heated to 700-1000℃ per minute for carbonization. After sieving and iron removal, graphene-coated silicon-carbon anode material is obtained.

2. The silicon-carbon anode according to claim 1, characterized in that, The current collector is selected from copper foil, copper mesh or copper foam, and has a thickness of 5~20μm.

3. The silicon-carbon anode according to claim 1, characterized in that, The areal density of the negative electrode material layer is 5~10 mg / cm³. 2 .

4. A method for preparing a silicon-carbon anode as described in any one of claims 1 to 3, characterized in that, Includes the following steps: A) Graphene slurry is coated onto the surface of the current collector to obtain a current collector with a graphene coating. B) The negative electrode material slurry is coated onto the surface of the graphene coating to obtain a silicon-carbon negative electrode; The negative electrode material slurry includes graphene-coated silicon-carbon negative electrode material.

5. The preparation method according to claim 4, characterized in that, The graphene slurry includes: 4-8 parts by weight of graphene; 1-2 parts by weight of conductive material; 6-7 parts by weight of adhesive; 80-85 parts by weight of solvent.

6. The preparation method according to claim 4, characterized in that, The negative electrode material slurry includes: 15-25 parts by weight of graphene-coated silicon-carbon anode material; 75-85 parts by weight of graphite anode material; 0.01~1 parts by weight of conductive material; 3-6 parts by weight of adhesive; 150-250 parts by weight of solvent.

7. The preparation method according to claim 4, characterized in that, In step A), the coating method is one or more of the following: doctor blade coating, roller transfer coating, slot extrusion coating, and gravure printing.

8. The preparation method according to claim 4, characterized in that, In step B), the coating method is one or more of the following: blade coating, roller transfer coating, and slot extrusion coating.

9. A silicon-carbon negative electrode battery, characterized in that, Includes the silicon-carbon anode as described in any one of claims 1 to 3.

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