Low-resistance lithium battery negative electrode sheet and preparation method therefor

Abstract

The present application relates to the technical field of lithium ion battery materials, and discloses a low-resistance lithium battery negative electrode sheet and a preparation method therefor. The raw materials for the preparation of the negative electrode sheet comprise at least one of a negative electrode material, a conductive agent, and a binder; the binder comprises a polyacrylate binder, styrene-butadiene rubber, and carboxymethylcellulose; the structural formula of the polyacrylate binder is as shown in formula (I). The preparation method comprises: mixing raw materials according to the raw material ratio of a formula, adding carboxymethylcellulose into deionized water, stirring and dissolving, then sequentially adding a polyacrylate binder emulsion, a conductive agent, and a negative electrode material, stirring and dispersing uniformly, and after the fineness of a slurry is tested to meet standards, adding a styrene-butadiene emulsion, mixing uniformly, defoaming, and filtering to obtain a negative electrode slurry; and coating a negative electrode current collector with the obtained negative electrode slurry, carrying out vacuum baking, and then carrying out rolling compaction to obtain a low-resistance lithium battery negative electrode sheet. The negative electrode sheet of the present invention can significantly reduce the resistance of the electrode sheet without increasing the amount of conductive agent usage.

Description

A low-resistance lithium battery negative electrode sheet and preparation method thereof

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of the State Intellectual Property Office of China on March 5, 2024, with application number CN202410247591.6 and invention name “A low-resistance lithium battery negative electrode plate and its preparation method”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application belongs to the technical field of lithium-ion battery materials, and specifically relates to a low-resistance lithium battery negative electrode plate and a preparation method thereof. Background Art

[0003] A lithium battery is a type of battery that uses lithium metal or lithium alloys as the positive and negative electrode materials and a non-aqueous electrolyte solution. With the advancement of science and technology, lithium batteries have become mainstream. To improve the rate performance of lithium batteries, the main approach currently is to reduce the electrode resistance. Conventional battery resistance control involves increasing the amount of conductive agents in the positive and negative electrode formulas to improve rate performance. Test data shows that when the conductive agent content exceeds a certain value, the battery resistance no longer decreases. This approach compromises energy density and increases costs.

[0004] During the preparation of lithium battery negative electrode sheets, the negative electrode material and conductive agent are primarily bonded to the current collector surface via a binder through coating and baking. Currently, the most widely used negative electrode binders are carboxymethyl cellulose and styrene-butadiene emulsions. These are economical and widely available, but due to material limitations, they cannot meet market demand for low-addition-dosage, high-bonding strength negative electrode binders. Summary of the Invention

[0005] In view of the shortcomings and deficiencies of the above-mentioned prior art, the primary purpose of this application is to provide a low-resistance negative electrode plate for lithium batteries, which can significantly reduce the resistance of the plate without increasing the amount of conductive agent used.

[0006] Another object of the present application is to provide a method for preparing the above-mentioned low-resistance lithium battery negative electrode sheet.

[0007] The purpose of this application is achieved through the following technical solutions:

[0008] A low-resistance lithium battery negative electrode plate, the raw materials for its preparation include a negative electrode material, a conductive agent and a binder; the binder includes at least one of a polyacrylate binder (PAA), styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC); the structural formula of the polyacrylate binder is shown in the following formula (I):

[0009] Wherein R is selected from C2-C 12 Alkyl, -CN, -NH2, -C(O)NH2, -NC4H6O, -C(O)NHC(CH3)3, -C(O)N(CH3)2, -C(O)NHC(CH3)2(CH2)4CH3; R1, R2, R3 are each independently selected from H or methyl; R4 is selected from C2-C7 alkyl; x, y, z are the number of repeating units of the polymer, and x:y:z=1~2:1:0.1~1.

[0010] Further preferably, the R is selected from -CN, -C(O)NH2 or -C(O)N(CH3)2; and the x:y:z=1~1.2:1:0.5~0.8.

[0011] Furthermore, the weight average molecular weight of the polyacrylate binder is 150,000 g / mol to 3,000,000 g / mol.

[0012] The polyacrylate adhesive of the present application can be obtained by conventional emulsion polymerization reaction using various polymerization monomers in proportion.

[0013] Furthermore, the negative electrode material is selected from one or more of graphite, graphene, silicon carbon, silicon monoxide, and metal oxides.

[0014] Furthermore, the conductive agent is selected from one or more of conductive carbon black (SP), carbon nanotubes, graphene, nanocarbon fibers, acetylene black, and conductive graphite.

[0015] Furthermore, the mass percentage ratio of the raw materials for preparation is as follows:

[0016] Conductive agent: 1% to 1.5%;

[0017] Polyacrylate binder: 0.8% to 2.5%;

[0018] Styrene-butadiene rubber: 0.2% to 0.5%;

[0019] Carboxymethyl cellulose: 0-0.5%;

[0020] Negative electrode material: 96%~98%.

[0021] Further preferably, the mass percentage ratio of the preparation raw materials is as follows:

[0022] Conductive agent: 1% to 1.5%;

[0023] Polyacrylate binder: 0.8% to 2%;

[0024] Styrene-butadiene rubber: 0.2% to 0.5%;

[0025] Negative electrode material: 96%~98%.

[0026] In the present application, the mass percentage of the polyacrylate binder refers to the mass percentage of the solid matter in the polyacrylate binder emulsion based on the total mass of the solids in the negative electrode slurry; the mass of the solid matter in the polyacrylate binder emulsion is calculated from the solid content of the polyacrylate binder emulsion.

[0027] In the present application, the mass percentage of the styrene-butadiene rubber refers to the mass percentage of the solid matter in the styrene-butadiene emulsion based on the total mass of the solids in the negative electrode slurry; the mass of the solid matter in the styrene-butadiene emulsion is calculated from the solid content of the styrene-butadiene emulsion.

[0028] The method for preparing the low-resistance lithium battery negative electrode sheet comprises the following steps:

[0029] (1) Preparation of negative electrode slurry: The ingredients are prepared according to the ratio of raw materials in the formula, carboxymethyl cellulose is added to deionized water and stirred to dissolve, and then polyacrylate binder emulsion and conductive agent are added and stirred to mix evenly, and then the negative electrode material is added and continued to be stirred and dispersed evenly. After the slurry fineness is tested and qualified, styrene-butadiene emulsion is added and mixed evenly, defoamed, and filtered to obtain the negative electrode slurry;

[0030] (2) Preparation of negative electrode sheet: The negative electrode slurry obtained in step (1) is coated on the negative electrode current collector, vacuum baked and then rolled to obtain a low-resistance lithium battery negative electrode sheet.

[0031] Furthermore, the qualified fineness of the slurry tested in step (1) means that D50 is less than 25 μm.

[0032] Furthermore, the negative electrode current collector in step (2) is made of copper foil; the coating controls the negative electrode single surface density to be 110 to 125 g / m 2 .

[0033] Furthermore, the vacuum baking in step (2) refers to using a vacuum oven at 85-95°C, circulating nitrogen and vacuuming, and baking for 6-10 hours; the roller compaction refers to rolling to a compaction density of 1.55-1.6 g / cm 3 .

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] (1) The negative electrode slurry of the present application uses a specific PAA as the main binder to improve the peeling force and reduce the total amount of binder in the formula to achieve the effect of reducing resistance. At the same time, the PAA binder uses monomers containing polar functional groups such as acrylic acid and acrylonitrile. Its polar functional group has the effect of "absorbing" electrons, which can improve the transmission of lithium ions. At the same time, it can establish a good conductive network in the negative electrode sheet, and ultimately achieve the improvement of conductivity without increasing the amount of conductive agent.

[0036] (2) The introduction of acrylate segments can reduce the viscosity of the slurry, increase the surface density of the electrode, improve the defect of brittle electrode, and enhance the bonding strength. However, an excessively high proportion of acrylate segments will lead to a decrease in the hydrophilicity and polarity of the adhesive, resulting in a decrease in bonding strength and conductivity. By controlling the ratio of polar functional group segments, acrylic acid segments and acrylate segments within the range of 1 to 2:1:0.1 to 1, especially within the range of 1 to 1.2:1:0.5 to 0.8, it is possible to maintain good viscosity, bonding strength and conductivity at the same time, making the adhesive easy to apply and maintain a high bonding strength, and having the characteristics of low resistance. DETAILED DESCRIPTION

[0037] The following examples and comparative examples are provided to more specifically illustrate the embodiments of the present invention. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0038] Test methods and equipment:

[0039] The negative electrode slurry and negative electrode sheet performance test methods in the following examples are as follows:

[0040] Viscosity test method: Use a viscometer (Model: Brookfield DV2T) with a rotor of RV04 and a rotation speed of 20 RPM to test the slurry for 1 minute. After the viscosity reading stabilizes, record the viscosity.

[0041] Weight average molecular weight was determined by gel permeation chromatography (GPC) using a Tosoh HLC-8420GPC instrument.

[0042] Peel force test method: A universal tensile tester (model: TY8000, Shanghai Rongjida Instrument Technology Co., Ltd.) was used to test the 180° peel force of the negative electrode sheets of the embodiment and the comparative example. The peel force test was performed using a sample made of 2 cm wide and 5 cm long. The pulling speed was 2 mm / s, and the unit of peel force was N / cm.

[0043] Electrode resistivity test method: Use a pressure resistance meter (model: Yuanneng Technology (Xiamen) Co., Ltd. BER2500) to test the electrode resistance. The humidity environment is 25-75% rh, the test pressure is 25MPa, the pressure holding time is 10s, and the test area is 153.94mm 2 , test the electrode resistance three times and take the average value.

[0044] The maximum surface density test method of the electrode: weigh the mass of the copper foil with an area of ​​10 square centimeters, record it as m1. Use a coating machine to adjust the coating thickness of the negative electrode to adjust the surface density and obtain a single-sided coated electrode. Use a cutter to cut out an area of ​​10 square centimeters of electrode, weigh the electrode weight m2 using an electronic balance, deduct the weight of the copper foil, and calculate the single-sided surface density of the electrode. Make a single-sided coating, the coated single-sided surface density is 90-130g / m 2 For a pole piece with a gradient of 5, fold the pole piece 180 degrees and visually check if there is no obvious crack in the pole piece and no break in the copper foil. The pole piece is qualified. The value with the largest single-sided surface density among the qualified pole pieces is the maximum surface density of the pole piece, and the unit is g / m 2 .

[0045] Pole sheet ultimate compaction density test method: Prepare a double-sided negative electrode sheet. The single-sided density of the negative electrode sheet is the maximum surface density of the electrode sheet. Observe the thickness of the negative electrode slurry coating on one side using a scanning electron microscope. The unit is μm.

[0046] The negative electrode sheet is rolled using a roller press with a pressure of 30 tons. The compaction density is: single-side density / single-side thickness, unit: g / cm 3 After rolling, the electrode is qualified if the copper foil does not break when folded three times, the electrode is smooth and has no obvious cracks. The maximum compaction density of the qualified electrode after rolling is the ultimate compaction density of the electrode.

[0047] Solids content test method: Take a small amount of sample and spread it flat on aluminum foil of mass m. Record the total mass of the foil and sample as M1. Bake the foil containing the sample in a 120°C oven for 30 minutes to completely evaporate the solvent. Record the total mass of the foil and sample as M2. Calculate the solids content of the sample as (M2-m) / (M1-m) × 100%.

[0048] Slurry fineness test method: The particle size of the particulate matter in the slurry was measured using a laser particle size analyzer (LS-POP(9) model, Zhuhai OMEC). The particle size distribution was calculated using Mie theory. The average value of three parallel samples was taken as the final test result. Among them, D50 indicates the particle size smaller than 50% of the total number of particles.

[0049] In the following examples, a polyacrylate binder is prepared as follows: 1 mol of monomer 1, monomer 2, and monomer 3 are weighed in sequence at a molar ratio of x:y:z. 2 g of sodium lauryl sulfate is weighed as an emulsifier. Deionized water is added and stirred to emulsify the emulsion. The solids content of the emulsion is controlled to approximately 20%. Under nitrogen protection, the temperature is raised to 70-80°C at a rate of 5°C / min. 0.15 g of sodium persulfate is added as an initiator. The reaction is maintained at this temperature for 2 hours to obtain a polyacrylate binder (PAA) emulsion. The solids content of the polyacrylate binder (PAA) emulsion is adjusted to 10% by adjusting the amount of deionized water added.

[0050] The polymerizable monomers include polymerizable monomer 1, polymerizable monomer 2, and polymerizable monomer 3. The types of the polymerizable monomers are selected based on the types of R, R1, R2, R3, and R4. For example, the polymerizable monomer 1 is selected from at least one of acrylonitrile, acrylamide, methacrylonitrile, methacrylamide, dimethylaminomethyl acrylate, N-tert-butyl-N-n-pentyl acrylamide, and N-tert-butyl acrylamide; the polymerizable monomer 2 is selected from at least one of acrylic acid and methacrylic acid; and the polymerizable monomer 3 is selected from at least one of ethyl acrylate, propyl acrylate, butyl acrylate, n-pentyl acrylate, hexyl acrylate, isooctyl acrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, n-pentyl methacrylate, hexyl methacrylate, and isooctyl methacrylate.

[0051] Example 1

[0052] The negative electrode slurry of a lithium-ion battery of this embodiment has the following raw materials: conductive carbon black SP 1.5%, polyacrylate binder PAA1 emulsion 1.5% (based on solid content), styrene-butadiene emulsion SBR 0.5% (based on solid content), carboxymethyl cellulose CMC 0.5%, and negative electrode material graphite 96%.

[0053] The negative electrode sheet of the lithium-ion battery of this embodiment is prepared by the following method:

[0054] In a 5L planetary stirred tank, 1288g of deionized water was added, 7.5g of CMC was dissolved, and then 225g of PAA1 emulsion (solid content 10%) and 22.5g of SP were added. The mixture was dispersed at 1000rpm and 50rpm for 2h. Then, 1440g of graphite was added and the high-speed dispersion was continued for 2h. The fineness of the negative electrode slurry was tested to be <25μm. 15g of SBR emulsion (solid content 50%) was added, the stirring was adjusted to 15rpm, the dispersion was closed, and the foaming was defoamed for 30min. The negative electrode slurry was filtered through a 180-mesh filter to obtain the negative electrode slurry. The obtained negative electrode slurry was coated on copper foil and baked in a vacuum oven at 90°C with nitrogen circulating and vacuuming for 8h. It was then roller-compacted to obtain a negative electrode sheet for a lithium-ion battery.

[0055] The structural formula of PAA1 used in this embodiment is as follows:

[0056] Wherein R is -CN; R1, R2, and R3 are all H; R4 is pentyl; x:y:z=1.2:1:0.6, and the weight average molecular weight of PAA1 is 400,000 g / mol.

[0057] In this embodiment, R4 can be selected from C2-C7 alkyl groups, and the performance of the resulting polyacrylate adhesive is not much different from that of PAA1.

[0058] Example 2

[0059] In the lithium ion battery negative electrode sheet of this embodiment, compared with embodiment 1, the amount of carboxymethyl cellulose (CMC) added is 0, the amount of graphite added as the negative electrode material is increased to 96.5%, and the rest are the same.

[0060] Example 3

[0061] This embodiment provides a lithium-ion battery negative electrode sheet, similar to Example 1, except that PAA2 replaces PAA1. In the PAA2 structural formula, R is -CN; R1, R2, and R3 are all methyl groups; R4 is a pentyl group; x:y:z = 1.2:1:0.6; and PAA2 has a weight-average molecular weight of 500,000 g / mol.

[0062] Example 4 to Example 8

[0063] Compared with Example 1, Examples 4 to 8 respectively use PAA3 to PAA7 instead of PAA1, and the rest are the same.

[0064] In the structural formulas of PAA3 to PAA7, R is respectively a C6 alkyl, -C(O)NH2, -NC4H6O, -C(O)NHC(CH3)3 and -C(O)N(CH3)2; R1, R2 and R3 are all H; R4 is a pentyl group; x:y:z=1.2:1:0.6.

[0065] Among them, the weight average molecular weights of PAA3, PAA4, PAA5, PAA6 and PAA7 are 500,000 g / mol, 600,000 g / mol, 740,000 g / mol, 870,000 g / mol and 780,000 g / mol, respectively.

[0066] Example 9 to Example 16

[0067] Compared with Example 2, Examples 9 to 16 respectively use PAA8 to PAA 15 Replaces PAA1, all other functions are the same.

[0068] PAA8~PAA 15 In the structural formula, x:y:z are 2:1:0.6, 1.5:1:0.6, 1:1:0.6, 1.2:1:0.1, 1.2:1:0.3, 1.2:1:0.5, 1.2:1:0.8 and 1.2:1:1, respectively, and the rest are the same as PAA1.

[0069] Among them, PAA8, PAA9, PAA 10 、PAA 11 、PAA 12 、PAA 13 、PAA 14 、PAA 15 The weight average molecular weights are 1,280,000 g / mol, 1,620,000 g / mol, 1,520,000 g / mol, 1,230,000 g / mol, 1,180,000 g / mol, 1,830,000 g / mol, 2,130,000 g / mol and 2,690,000 g / mol respectively.

[0070] Example 17

[0071] Compared with Example 2, the weight percentage ratio of raw materials for preparing the negative electrode slurry in this embodiment is: conductive agent SP 1%, polyacrylate binder PAA 10.8%, styrene-butadiene rubber SBR 0.2%, and negative electrode material graphite 98%, and the rest are the same.

[0072] Example 18

[0073] Compared with Example 2, the weight percentage ratio of raw materials for preparing the negative electrode slurry in this embodiment is: conductive agent SP 1.5%, polyacrylate binder PAA 12%, styrene-butadiene rubber SBR 0.5%, and negative electrode material graphite 96%, and the rest are the same.

[0074] Comparative Example 1

[0075] Compared with Example 1, this comparative example adopts PAA16 Replaces PAA1, all other functions are the same.

[0076] The PAA 16 In the structural formula, x:y:z=1.2:0:0.6, PAA 16 The weight average molecular weight is 1450000 g / mol, and the rest is the same as PAA1.

[0077] Comparative Example 2

[0078] Compared with Example 2, this comparative example adopts PAA 16 Replaces PAA1, all other functions are the same.

[0079] Comparative Example 3

[0080] Compared with Example 1, this comparative example adopts PAA 17 Replaces PAA1, all other functions are the same.

[0081] The PAA 17 In the structural formula, x:y:z=1.2:1:0, PAA 17 The weight average molecular weight is 1320000 g / mol, and the rest is the same as PAA1.

[0082] Comparative Example 4

[0083] Compared with Example 2, this comparative example adopts PAA 17 Replaces PAA1, all other functions are the same.

[0084] Comparative Example 5

[0085] Compared with Example 1, this comparative example adopts PAA 18 Replaces PAA1, all other functions are the same.

[0086] The PAA 18 In the structural formula, x:y:z=0:1:0.6, PAA 18 The weight average molecular weight is 390,000 g / mol, and the rest is the same as PAA1.

[0087] Comparative Example 6

[0088] Compared with Example 2, this comparative example adopts PAA 18 Replaces PAA1, all other functions are the same.

[0089] Comparative Example 7

[0090] Compared with Example 1, this comparative example adopts PAA 19 Replaces PAA1, all other functions are the same.

[0091] The PAA 19In the structural formula, x:y:z=0.8:1:0.6, PAA 19 The weight average molecular weight is 170,000 g / mol, and the rest is the same as PAA1.

[0092] Comparative Example 8

[0093] Compared with Example 1, this comparative example adopts PAA 20 Replaces PAA1, all other functions are the same.

[0094] The PAA 20 In the structural formula, x:y:z=2.2:1:0.6, PAA 20 The weight average molecular weight is 1830000 g / mol, and the rest is the same as PAA1.

[0095] Comparative Example 9

[0096] Compared with Example 1, this comparative example adopts PAA 21 Replaces PAA1, all other functions are the same.

[0097] The PAA 21 In the structural formula, x:y:z=1.2:1:1.2, PAA 21 The weight average molecular weight is 730,000 g / mol, and the rest is the same as PAA1.

[0098] The performance test results of the negative electrode slurries and negative electrode sheets obtained in the above examples and comparative examples are shown in Table 1 below.

[0099] Table 1

[0100] Comparing the results of Examples 1 and 2, it can be seen that the addition of CMC is detrimental to the peel strength and conductivity of the electrode. This is because CMC's Tg is too high, which causes the electrode to become brittle and the adhesion to decrease when the binder addition level is low. In contrast, in the absence of CMC and with a reduced binder addition level, the conductivity of Example 2 improves, which is due to the combination of the electron-withdrawing polar groups of PAA and the reduced amount of binder. The results of Example 3 show that R1, R2, and R3 selected from methyl or hydrogen have little effect on the performance of the electrode. The results of Examples 4 to 8 show that R selected from alkyl, cyano, -C(O)NH2, -NC4H6O, -C(O)NHC(CH3)3, -C(O)N(CH3)2, etc. can all achieve good electrode performance, but the use of highly polar -CN, -C(O)NH2, or -C(O)N(CH3)2 can achieve better conductivity and adhesion than other substituents. It can be seen from the results of Examples 9 to 16 that, within the range of x:y:z=1~2:1:0.1~1, as the ratio of the R group segment decreases, its viscosity tends to increase, and the adhesion and conductivity tend to increase. As the ratio of the acrylate segment increases, its viscosity tends to decrease, and the adhesion and conductivity tend to increase first and then decrease. Within the range of x:y:z=1~1.2:1:0.5~0.8, good viscosity, adhesion and conductivity can be maintained at the same time. It can be seen from the results of Examples 17 to 18 that the present application can maintain high adhesion and conductivity properties while using less adhesive and conductive agent.

[0101] From the results of Comparative Examples 1 and 2, it can be seen that after the polyacrylate adhesive does not contain acrylic acid segments, the slurry viscosity decreases significantly, and the peeling force and conductivity decrease significantly. From the results of Comparative Examples 3 and 4, it can be seen that the polyacrylate adhesive does not contain acrylic acid segments, the slurry viscosity increases, the adhesive is significantly more hydrophilic, the surface density of the electrode decreases, the electrode becomes brittle, and the peeling force also deteriorates. From the results of Comparative Examples 5 and 6, it can be seen that the polyacrylate adhesive does not contain R group segments, the electrode ultimate compaction density decreases, the mechanical properties of the adhesive deteriorate, it cannot withstand pressure, and the conductivity deteriorates significantly. From the results of Comparative Examples 7, 8 and 9, it can be seen that the proportions of functional group segments, acrylic acid segments and acrylate segments in the polyacrylate adhesive exceed the scope of this application, and the electrode peeling force and conductivity are low.

[0102] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of this application should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A low-resistance lithium battery negative electrode plate, characterized in that: The raw materials for preparing the negative electrode plate include a negative electrode material, a conductive agent and a binder; the binder includes at least one of a polyacrylate binder, styrene-butadiene rubber and carboxymethyl cellulose; the structural formula of the polyacrylate binder is shown in the following formula (I): Wherein R is selected from C2-C 12 Alkyl, -CN, -NH2, -C(O)NH2, -NC4H6O, -C(O)NHC(CH3)3, -C(O)N(CH3)2, -C(O)NHC(CH3)2(CH2)4CH3; R1, R2, R3 are each independently selected from H or methyl; R4 is selected from C2-C7 alkyl; x, y, z are the number of repeating units of the polymer, and x:y:z=1~2:1:0.1~1.

2. The low-resistance lithium battery negative electrode according to claim 1, characterized in that: The R is selected from -CN, -C(O)NH2 or -C(O)N(CH3)2; the x:y:z=1~1.2:1:0.5~0.

8.

3. The low-resistance lithium battery negative electrode according to claim 1, characterized in that: The weight average molecular weight of the polyacrylate binder is 150,000 g / mol to 3,000,000 g / mol.

4. The low-resistance lithium battery negative electrode according to claim 1, characterized in that: The negative electrode material is selected from one or more of graphite, graphene, silicon carbon, silicon monoxide, and metal oxides.

5. The low-resistance lithium battery negative electrode according to claim 1, characterized in that: The conductive agent is selected from one or more of conductive carbon black, carbon nanotubes, graphene, nanocarbon fibers, acetylene black, and conductive graphite.

6. The low-resistance lithium battery negative electrode according to claim 1, characterized in that: The mass percentage ratio of the raw materials for preparation is as follows: Conductive agent: 1% to 1.5%; Polyacrylate binder: 0.8% to 2.5%; Styrene-butadiene rubber: 0.2% to 0.5%; Carboxymethyl cellulose: 0-0.5%; Negative electrode material: 96%~98%.

7. The low-resistance lithium battery negative electrode according to claim 6, characterized in that: The mass percentage ratio of the raw materials for preparation is as follows: Conductive agent: 1% to 1.5%; Polyacrylate binder: 0.8% to 2%; Styrene-butadiene rubber: 0.2% to 0.5%; Negative electrode material: 96%~98%.

8. The method for preparing a low-resistance lithium battery negative electrode sheet according to any one of claims 1 to 7, characterized in that: The method comprises the following preparation steps: (1) Preparation of negative electrode slurry: The ingredients are prepared according to the ratio of raw materials in the formula, carboxymethyl cellulose is added to deionized water and stirred to dissolve, and then polyacrylate binder emulsion and conductive agent are added and stirred to mix evenly, and then the negative electrode material is added and continued to be stirred and dispersed evenly. After the slurry fineness is tested and qualified, styrene-butadiene emulsion is added and mixed evenly, defoamed, and filtered to obtain the negative electrode slurry; (2) Preparation of negative electrode sheet: The negative electrode slurry obtained in step (1) is coated on the negative electrode current collector, vacuum baked and then rolled to obtain a low-resistance lithium battery negative electrode sheet.

9. The method for preparing a low-resistance lithium battery negative electrode sheet according to claim 8, characterized in that: The qualified fineness of the slurry tested in step (1) means D50 < 25 μm.

10. The method for preparing a low-resistance lithium battery negative electrode sheet according to claim 8, characterized in that: The negative electrode current collector in step (2) is made of copper foil; the coating controls the negative electrode single surface density to be 110-125 g / m 2 .

11. The method for preparing a low-resistance lithium battery negative electrode sheet according to claim 8, characterized in that: The vacuum baking in step (2) refers to using a vacuum oven at 85-95°C, circulating nitrogen and vacuuming, and baking for 6-10 hours; the roller compaction refers to rolling to a compaction density of 1.55-1.6 g / cm 3 .

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