Pole piece and application thereof

Abstract

The invention relates to the technical field of batteries, in particular to a pole piece and application thereof. The pole piece comprises a pole piece material, the pole piece material contains resin-based oil absorption microspheres, the resin-based oil absorption microspheres are elastomers of porous structures, and the absorption rate of the resin-based microspheres to chloroform is 40-70 g / g. The electrolyte is locked in the oil absorption microspheres through the strong oil absorption capacity of the hollow resin-based oil absorption microspheres, and when the pole piece is slowly extruded by stress, the oil absorption microspheres can inject the electrolyte into gaps of active substance particles, so that the problem of insufficient electrode liquid among the particles in the stress extrusion process of the pole piece is solved, the lithium precipitation phenomenon of the pole piece during high-rate charging is improved, and the service life of the pole piece is prolonged. The rate capability and the cycle performance of the material are improved.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a pole piece and applications thereof. Background Art

[0002] The current pain points of new energy vehicles include battery life, charging efficiency, cost, safety, etc. Batteries have become the key to increasing the penetration rate of new energy vehicles.

[0003] In the power sector, increasing the size of cylindrical batteries can improve energy density, reduce the number of cells used in the vehicle, and reduce the difficulty of managing the battery management system. As the outer diameter increases, the proportion of components that do not contribute to the battery's capacity decreases, production efficiency will be improved, and therefore costs will be reduced. Large cylindrical batteries have relative advantages such as high energy density, strong and fast charging, high safety, and long life. They are more in line with the demand for long-range and ultra-fast charging in mid-to-high-end passenger cars, becoming the optimal solution for future mid-to-high-end electric vehicles. Currently, major companies are actively planning and deploying large cylindrical battery production lines.

[0004] Compared with small cylindrical batteries, existing large cylindrical batteries have higher internal space utilization rates, and the proportion of positive and negative active materials has increased significantly. However, the more compact internal space of the shell will lead to high viscosity of the electrolyte and a significant reduction in the wettability of the electrolyte. In addition, during the use of the cylindrical battery, the internal expansion of the cylindrical battery squeezes the inner wall of the structural parts, causing the electrolyte to be discharged from the electrode and diaphragm, resulting in a reduction in the actual effective contact between the electrode and the electrolyte, which in turn affects the battery's cycle, capacity and fast charging.

[0005] Existing technical information:

[0006] CN113299918B discloses a negative electrode plate. A dispersing aid is added to a negative electrode slurry, stirred evenly, and coated into a plate. Hydrogen bonds are formed by relying on the intermolecular force between the H bonds of the imino groups in the organic dispersant and the oxygen in the negative electrode active material. The organic dispersant is loaded on the surface of the negative electrode active material. The strong binding force between the phenolic base of the organic dispersant and the lipid solvent of the electrolyte is then utilized to improve the wettability of the electrolyte to the plate, thereby improving the cycle performance and high-rate performance of the battery.

[0007] CN115621414 A discloses a lithium-ion battery negative electrode that is conducive to electrolyte infiltration at low temperatures. The electrolyte wettability of the electrode is improved by covering the surface of the graphite active material layer with an electrolyte infiltration layer. The PMDS (polydimethylsiloxane) loaded in the electrolyte infiltration layer has the characteristics of low surface tension, low viscosity at low temperatures, and good affinity with the electrolyte, thereby improving the electrolyte wettability of the electrode and improving the battery's cycle performance at low temperatures. Summary of the Invention

[0008] The inventors of the present invention have found after in-depth research on the prior art:

[0009] CN 113299918 B uses an organic dispersing agent to improve the wettability of the electrode with the electrolyte. However, the dispersing agent molecules are connected to the active material particles through hydrogen bonds. Since hydrogen bonds are weak forces, they are destroyed during the cycle as side reactions of the electrolyte proceed, resulting in poor wettability. Furthermore, this technology only addresses the wettability of the electrolyte on the surface of the active material particles. Stress extrusion during the cycle can result in a small amount of electrolyte remaining inside the battery cell electrode. This phenomenon is more pronounced in large cylindrical cells.

[0010] CN 115621414 A improves the wettability of the electrolyte by covering the surface of the negative electrode active material layer with an electrolyte infiltration layer in parallel. However, the wettability of the electrolyte on the surface of the graphite active material particles inside the electrode is still not improved. The amount of electrolyte retained on the surface of the active material particles and between the particles is low, which has little effect on the cycle and rate improvement of the battery cell.

[0011] In view of this, the present invention is proposed.

[0012] One purpose of the present invention is to provide a pole piece that can improve the problem of insufficient electrolyte between particles during the stress extrusion process of the pole piece, improve the lithium deposition phenomenon of the pole piece during high-rate charging, and improve the rate performance and cycle performance of the material.

[0013] Another object of the present invention is to provide a battery.

[0014] Another object of the present invention is to provide an electrical device.

[0015] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0016] A pole piece includes a pole piece material. The pole piece material contains resin-based oil-absorbing microspheres. The resin-based oil-absorbing microspheres are elastomers with a porous structure. The resin-based microspheres have an absorption rate of 40 to 70 g / g for chloroform.

[0017] In some embodiments, the resin-based microspheres have an absorption rate of chloroform of 55 to 70 g / g.

[0018] In some embodiments, the resin-based oil-absorbing microspheres include polystyrene-polyurethane composite microspheres.

[0019] In some embodiments, the resin-based oil-absorbing microspheres account for 0.3% to 0.8% by mass of the pole piece material.

[0020] In some embodiments, the particle size D of the resin-based oil-absorbing microspheres is v 50 is 0.8~3.5μm.

[0021] In some embodiments, the resin-based oil-absorbing microspheres account for 0.4% to 0.6% by mass of the pole piece material.

[0022] In some embodiments, the particle size D of the resin-based oil-absorbing microspheres is v 50 is 1.5~3μm.

[0023] In some embodiments, the weight average molecular weight of the lipid-based oil-absorbing microspheres is 300,000 to 500,000.

[0024] In some embodiments, the electrode material further includes a negative electrode active material.

[0025] In some embodiments, the negative electrode active material includes composite graphite particles, which include a graphite core, an amorphous carbon layer coated on the surface of the graphite core, and nano-silicon dioxide particles located in the amorphous carbon layer, and the nano-silicon dioxide particles are at least embedded in the amorphous carbon surface.

[0026] In some embodiments, the composite graphite particles have a silicon content of 0.05% to 0.2%.

[0027] In some embodiments, the pole piece material further includes a binder, and / or a conductive agent, and / or a dispersant.

[0028] A battery comprises the pole piece.

[0029] An electrical device comprises the battery.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The present invention locks the electrolyte in the oil-absorbing microspheres through the strong oil-absorbing ability of the hollow resin-based oil-absorbing microspheres. When the electrode is slowly squeezed by stress, the oil-absorbing microspheres can inject electrolyte into the gaps between the active material particles, thereby improving the problem of insufficient electrolyte between the particles during the stress squeezing process of the electrode, improving the lithium plating phenomenon of the electrode during high-rate charging, and improving the rate performance and cycle performance of the material.

[0032] (2) The battery of the present invention has excellent fast charging performance, good cycle stability and high safety performance. DETAILED DESCRIPTION

[0033] The embodiments of the present invention will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present invention and should not be construed as limiting the scope of the invention. Where specific conditions are not specified in the examples, the methods were performed according to conventional conditions or the conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments are not specified, they are all commercially available conventional products.

[0034] According to one aspect of the present invention, the present invention relates to a pole piece, including a pole piece material, wherein the pole piece material contains resin-based oil-absorbing microspheres, the resin-based oil-absorbing microspheres are elastomers with a porous structure, and the absorption rate of the resin-based microspheres for chloroform is 40 to 70 g / g.

[0035] Resin microspheres are porous elastomers that deform after compression and return to their original shape after stress relief. Similar to a sponge, they are insoluble in electrolyte. This invention leverages the strong oil-absorbing capacity of the hollow resin-based oil-absorbing microspheres to lock the electrolyte within them. When the electrode is slowly squeezed by stress, the microspheres can inject electrolyte into the gaps between the active material particles, alleviating the problem of insufficient electrolyte in the particles during stress compression, improving lithium deposition during high-rate charging, and enhancing the material's rate and cycling performance.

[0036] In some embodiments, the resin-based microspheres have an absorption rate of chloroform of 40 to 70 g / g, such as 40 g / g, 45 g / g, 50 g / g, 55 g / g, 60 g / g, 65 g / g, or 70 g / g, or any range therebetween. In some preferred embodiments, the resin-based microspheres have an absorption rate of chloroform of 55 to 70 g / g. The resin-based microspheres of the present invention have a high absorption rate for chloroform, can improve electrolyte wettability, and have outstanding advantages in enhancing electrode kinetic performance.

[0037] In some embodiments, the resin-based oil-absorbing microspheres include polystyrene-polyurethane composite microspheres (PS-PU composite microspheres).

[0038] In some embodiments, the mass proportion of the resin-based oil-absorbing microspheres in the pole piece material is 0.3% to 0.8%, such as 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, or any range therebetween. In some preferred embodiments, the mass proportion of the resin-based oil-absorbing microspheres in the pole piece material is 0.4% to 0.6%. The resin-based oil-absorbing microspheres of the present invention have an appropriate mass proportion in the pole piece material, which can better function. The density of resin-based oil-absorbing microspheres is small. If the amount is too high, although it can improve the problem of difficulty in retaining the electrolyte in the electrode and reduced ionic conductivity caused by stress extrusion during the expansion of the electrode, resin is a poor conductor of electrons. Excessive addition will reduce the electronic conductivity of the electrode, which will have a certain adverse effect on the improvement of fast charging performance and will lead to low compaction of the electrode; if the content of resin-based oil-absorbing microspheres is too low, there will be few scattered points around the negative active material, and the improvement of the ionic conductivity of the battery cell during high-rate charging will not be obvious, resulting in a large concentration polarization of the battery cell, which is not conducive to high-rate charging.

[0039] In some embodiments, the particle size of the resin-based oil-absorbing microspheres is related to the diameter of the gaps between the electrode particles after the electrode is rolled. Currently, the gap diameter of the electrode after conventional rolling is 0.5 to 3 μm. The particle size of the resin-based oil-absorbing microspheres is slightly larger than the gap diameter of the electrode. Therefore, the particle size D of the resin-based oil-absorbing microspheres is v 50 is 0.8 to 3.5 μm, such as 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, etc., or any range between the two. In some preferred embodiments, the particle size D of the resin-based oil-absorbing microspheres is v 50 is 1.5~3μm.

[0040] In some embodiments, the molecular weight of the resin-based oil-absorbing microspheres primarily affects their rebound resilience, stability in the electrolyte, and oil absorption. The weight-average molecular weight of the lipid-based oil-absorbing microspheres is 250,000 to 600,000, for example, 250,000, 300,000, 350,000, 400,000, 450,000, 500,000, or 600,000, or any range therebetween. In some preferred embodiments, the weight-average molecular weight of the lipid-based oil-absorbing microspheres is 300,000 to 500,000. The lipid-based oil-absorbing microspheres of the present invention possess an appropriate weight-average molecular weight, thereby ensuring suitable rebound resilience, excellent stability in the electrolyte, and suitable oil absorption.

[0041] In some embodiments, the electrode material further comprises a negative electrode active material. The negative electrode active material comprises a composite graphite material. Preferably, the negative electrode active material comprises composite graphite particles, the composite graphite particles comprising a graphite core, an amorphous carbon layer coated on the surface of the graphite core, and nano-silicon dioxide particles located on the amorphous carbon layer, wherein the nano-silicon dioxide particles are at least embedded on the surface of the amorphous carbon. In the composite graphite particles of the present invention, the hydroxyl (-OH) groups on the surface of the SiO2 particles embedded on the surface of the carbon coating layer can form hydrogen bonds with solvent molecules (such as carbonates) in the electrolyte, reduce interfacial tension, and promote the spreading and penetration of the electrolyte on the surface of the active material, thereby improving the affinity between the active material particles and the electrolyte. When stress extrusion causes the particle gap to shrink, the pore volume to decrease, and the electrolyte fluidity to deteriorate, the SiO2 particles can improve the fluidity of the electrolyte in the small pores, promote the rapid migration of lithium ions, reduce polarization, improve the lithium precipitation phenomenon of the electrode during high-rate charging, and improve the rate performance and cycle performance of the material.

[0042] It is understood that, based on definitions such as ISO / TS27687:2008, nanoparticles refer to ultrafine particles with a particle size between 1-100 nm, such as 1 nm, 5 nm, 10 nm, 20 nm, 50 nm, 100 nm, etc., and or any range value therebetween.

[0043] In some embodiments, the composite graphite particles have a silicon content of 0.05% to 0.2%, for example, 0.05%, 0.08%, 0.1%, 0.12%, 0.15%, 0.18%, 0.2%, or any range therebetween. Composite graphite particles with an appropriate silicon content are beneficial for enhancing interfacial stability and SEI film regulation, mitigating volume expansion, improving electron / ion transport kinetics, and optimizing energy density and safety performance.

[0044] In some embodiments, the mass proportion of the negative electrode material in the electrode sheet material is 94% to 97.5%.

[0045] In some embodiments, the electrode material further comprises a binder, and / or a conductive agent, and / or a dispersant. In some embodiments, the binder accounts for 0.5% to 1.5% by weight of the electrode material. The conductive agent accounts for 1.5% to 2.5% by weight of the electrode material. The dispersant accounts for 0.5% to 1.5% by weight of the electrode material.

[0046] According to another aspect of the present invention, the present invention also relates to a method for preparing the above-mentioned pole piece, comprising the following steps:

[0047] A. Obtain resin-based oil-absorbing microspheres.

[0048] B. Obtain negative electrode active material.

[0049] C. Obtain a slurry containing the resin-based oil-absorbing microspheres and the negative electrode active material, and apply the slurry on at least one side of the current collector to obtain a pole piece.

[0050] In some embodiments, the method for preparing resin-based oil-absorbing microspheres comprises the following steps:

[0051] (a) A polystyrene solution and a fluorinated polyurethane prepolymer solution were mixed in a mass ratio of (2-4):(6-8). The polystyrene had a molecular weight of 80,000, and the polystyrene solution was prepared in tetrahydrofuran at a concentration of 10%. The fluorinated polyurethane prepolymer solution was an IPDI-PFPE system with an NCO content of 8%, prepared in tetrahydrofuran at a concentration of 20%. Tetrahydrofuran was added to bring the solid content to 12%. A porogen, sodium chloride (porogen particle size Dv50 = 50 nm), was added at 30% by mass of the slurry, and ultrasonic dispersion was performed for 30 minutes. An oil phase emulsifier, Span 80, was added (content 2% by mass of the oil phase), and magnetic stirring was performed for 1 hour to obtain a first material.

[0052] The preparation of the fluorinated polyurethane prepolymer solution comprises the following steps: 1) heating PFPE (perfluoropolyether polyol, molecular weight 2000) with a water content of 0.01% to 60°C at a rotation speed of 300 r / min under nitrogen protection. 2) adding 40% IPDI (isophorone diisocyanate, purity ≥99%) and 0.02% catalyst DBTDL (dibutyltin dilaurate, purity ≥99%) to the PFPE, raising the temperature to 70°C, and continuing the reaction with stirring for 3 hours. 3) monitoring the NCO content during the reaction. When the NCO content drops to 8% (verified by di-n-butylamine titration), rapidly cooling the temperature to 40°C. 4) slowly adding 4 times the mass of dehydrated THF (tetrahydrofuran, water content ≤50 ppm) to the product, maintaining a stirring speed of 200 r / min until the solution becomes transparent, thereby obtaining the fluorinated polyurethane prepolymer solution.

[0053] (b) Dissolving 1% polyvinyl alcohol and 0.5% ammonium persulfate in deionized water, by mass percentage, and heating to 50° C. to dissolve, thereby obtaining a second material.

[0054] (c) slowly adding the obtained first material to the obtained second material, with the volume ratio of the first material to the second material being 1:(10-20), and adopting high-speed shear emulsification with a shear speed of 10,000-20,000 r / min and a shear time of 10-60 min to obtain a third material.

[0055] (d) The third material was subjected to magnetic stirring at a stirring speed of 500 r / min and a temperature of 50° C., and tetrahydrofuran was continuously volatilized until the residual amount of tetrahydrofuran was 50%, thereby obtaining a concentrated liquid phase material.

[0056] (e) adding triethylamine to the liquid material to catalyze the crosslinking of the fluorinated polyurethane prepolymer, wherein the amount of triethylamine added is 0.1% to 1.0% by mass, and continuing heating and magnetic stirring until the tetrahydrofuran is completely volatilized to obtain a semi-finished resin microsphere product.

[0057] (f) washing the semi-finished resin microspheres with hot water at 60° C. to remove sodium chloride, collecting the microspheres by centrifugation, and vacuum drying for 24 h at a temperature of 30° C. to obtain the target product, resin-based oil-absorbing microspheres.

[0058] In some embodiments, the mass ratio of the polystyrene solution to the fluorinated polyurethane prepolymer solution is 2:8, 2.5:7.5, 3:7, 3.5:6.5, 4:6, etc.

[0059] In some embodiments, the volume ratio of the first material to the second material is 1:(10-20), for example, 1:10, 1:12, 1:15, 1:18, 1:20, etc.

[0060] In some embodiments, the shear rate is 10,000 to 20,000 r / min, such as 10,000 r / min, 12,000 r / min, 15,000 r / min, 18,000 r / min, 20,000 r / min, or any range therebetween. The shear time is 10 to 60 min, such as 10 min, 20 min, 30 min, 40 min, 50 min, or 60 min, or any range therebetween.

[0061] The resin-based oil-absorbing microspheres in the specific embodiment of the present invention are prepared using the above-described preparation method. Using the above-described raw materials, operating steps, and conditions, resin-based oil-absorbing microspheres having a suitable porous structure, suitable chloroform absorption rate, suitable molecular weight, and suitable particle size are obtained. However, the preparation method of the resin-based microspheres of the present invention is not limited thereto.

[0062] In some embodiments, the method for preparing the negative electrode active material comprises the following steps:

[0063] (1) Petroleum coke is crushed to obtain material A having a particle size Dv50 of 4 to 12 μm.

[0064] (2) Material A is mixed with an organic carbon source and granulated to obtain material B. The particle size Dv50 of material B is 8 to 17 μm.

[0065] (3) Material B was graphitized at a temperature of 3000°C for 12 hours in a protective gas atmosphere to obtain material C. The particle size of material C was 7 to 16 μm.

[0066] (4) Material C and polyaryl silicone resin were mixed in a mass ratio of 85-95:5-15, and carbonized at 1500°C for 2h under a protective gas atmosphere to obtain material D, i.e., the negative electrode active material.

[0067] In some embodiments, the modified silane resin includes polyaryl silicone resin high temperature resistant anti-corrosion coating TPSIV3040-70ABK.

[0068] In some embodiments, the organosilicon resin has a coking value of 5% to 50%.

[0069] In some embodiments, the protective gas includes nitrogen, argon, etc.

[0070] The present invention's method for preparing negative electrode active materials, through the combined use of the aforementioned steps, results in a negative electrode active material with an appropriate structural composition and silicon content. This, in combination with resin-based oil-absorbing microspheres, further improves the mechanical and electrochemical properties of the electrode layer, thereby enhancing the battery's fast-charging performance.

[0071] According to another aspect of the present invention, the present invention also relates to a battery, comprising the pole piece described above.

[0072] The electrode sheet of the present invention is suitable for cylindrical cells (such as 4680 cylindrical cells), square cells, and blade cells, especially single cells with high volumetric energy density, and is particularly suitable for cylindrical cells. For single cells, there are two ways to achieve high volumetric energy density: 1) increase the compaction density of the electrode sheet; 2) improve the space utilization of the cell. High space utilization will cause the electrode sheets and particles to squeeze each other during the expansion process, which will deteriorate the electrolyte retention performance in the electrode sheet. The mainstream technical route for high volumetric energy density cells is high compaction and high space utilization.

[0073] The battery of the present invention has excellent fast charging performance, good cycle stability and high safety performance.

[0074] According to another aspect of the present invention, the present invention also relates to an electric device comprising the battery. The electric device of the present invention includes electric vehicles, laptop computers, tablet computers, medical equipment, electric equipment, outdoor equipment, etc.

[0075] The following is further explained with reference to specific embodiments and comparative examples.

[0076] Example 1

[0077] A method for preparing a negative electrode sheet comprises the following steps:

[0078] 1. Preparation of resin-based oil-absorbing microspheres

[0079] (a) A polystyrene solution (molecular weight 80,000, solvent: tetrahydrofuran, concentration 10%) and a fluorinated polyurethane prepolymer solution (IPDI-PFPE system, NCO content 8%, solvent: tetrahydrofuran, concentration 20%) were mixed in a solution mass ratio of 3:7, tetrahydrofuran was added to adjust the solid content to 12%, sodium chloride porogen (50 nm sodium chloride accounting for 30% of the total solid content) was added, and ultrasonic dispersion was performed for 30 minutes. An oil phase emulsifier, Span 80, was added (Span 80 accounting for 2% of the oil phase mass), and magnetic stirring was performed for 1 hour to obtain a first material.

[0080] The preparation of the fluorinated polyurethane prepolymer solution comprises the following steps: 1) heating PFPE (perfluoropolyether polyol, molecular weight 2000) with a water content of 0.01% to 60°C at a rotation speed of 300 r / min under nitrogen protection. 2) adding 40% IPDI (isophorone diisocyanate, purity ≥99%) and 0.02% catalyst DBTDL (dibutyltin dilaurate, purity ≥99%) to the PFPE, raising the temperature to 70°C, and continuing the reaction with stirring for 3 hours. 3) monitoring the NCO content during the reaction. When the NCO content drops to 8% (verified by di-n-butylamine titration), rapidly cooling the temperature to 40°C. 4) slowly adding 4 times the mass of dehydrated THF (tetrahydrofuran, water content ≤50 ppm) to the product, maintaining a stirring speed of 200 r / min until the solution becomes transparent, thereby obtaining the fluorinated polyurethane prepolymer solution.

[0081] (b) Dissolve 1% polyvinyl alcohol and 0.5% ammonium persulfate in deionized water, and heat to 50° C. to dissolve to obtain a second material.

[0082] (c) The first material obtained above was slowly added to the second material, with a volume ratio of the first material to the second material of 1:15, and high-speed shear emulsification was adopted with a shear rate of 15000 r / min and a shear time of 30 min to obtain a third material.

[0083] (d) The third material was magnetically stirred at a stirring speed of 500 r / min and a temperature of 50° C., and tetrahydrofuran was continuously volatilized until the residual amount of tetrahydrofuran was 50%, thereby obtaining a concentrated liquid material.

[0084] (e) adding 0.5% (mass percentage) of triethylamine to the liquid phase material to catalyze the crosslinking of the fluorinated polyurethane prepolymer, and continuing heating with magnetic stirring until the tetrahydrofuran is completely volatilized to obtain a semi-finished resin microsphere product.

[0085] (f) The semi-finished resin microspheres were washed with hot water at 60° C. to remove sodium chloride, and the microspheres were collected by centrifugation and dried under vacuum for 24 h, while maintaining the temperature at 30° C. to obtain the target product, resin-based oil-absorbing microspheres, having a particle size Dv50 = 2 μm, a weight-average molecular weight of 400,000, and a chloroform absorption rate of 60 g / g.

[0086] 2. Preparation of negative electrode active materials

[0087] (1) Conventional pulverization of petroleum coke to obtain material A, the particle size of material A is Dv50 = 10 μm.

[0088] (2) Material A is mixed with coal tar and granulated to obtain material B. The particle size Dv50 of material B is 16 μm.

[0089] (3) Material B was graphitized at 3000°C for 12 hours in an argon atmosphere to obtain material C. The particle size of material C was 15 μm.

[0090] (4) Material C and polyaryl silicone resin high temperature resistant anticorrosive coating TPSIV 3040-70ABK were carbonized at 1500°C for 2h under nitrogen atmosphere to obtain material D, i.e., the negative electrode active material.

[0091] 3. Preparation of negative electrode sheet

[0092] The negative electrode active material, conductive agent SP, binder SBR, dispersant CMC and resin-based oil-absorbing microspheres are homogenized in a mass ratio of 95.7:2:1:1:0.3 to obtain a negative electrode slurry, which is then coated into a pole piece.

[0093] Example 2

[0094] A method for preparing a negative electrode sheet comprises the following steps:

[0095] 1. Preparation of resin-based oil-absorbing microspheres

[0096] Resin-based oil-absorbing microspheres were prepared according to the method of Example 1.

[0097] 2. Preparation of negative electrode active materials

[0098] Except that the mass ratio of material C to polyaryl silicone resin high temperature resistant anticorrosive coating TPSIV 3040-70A BK is 90:10, other conditions are the same as those in Example 1.

[0099] 3. Preparation of negative electrode sheet

[0100] The negative electrode active material, conductive agent SP, binder SBR, dispersant CMC and resin-based oil-absorbing microspheres are homogenized in a mass ratio of 95.7:2:1:1:0.3 to obtain a negative electrode slurry, which is then coated into a pole piece.

[0101] Example 3

[0102] A method for preparing a negative electrode sheet comprises the following steps:

[0103] 1. Preparation of resin-based oil-absorbing microspheres

[0104] Resin-based oil-absorbing microspheres were prepared according to the method of Example 1.

[0105] 2. Preparation of negative electrode active materials

[0106] Except that the mass ratio of material C to polyaryl silicone resin high temperature resistant anticorrosive coating TPSIV 3040-70A BK is 95:5, other conditions are the same as those in Example 1.

[0107] 3. Preparation of negative electrode sheet

[0108] The negative electrode active material, conductive agent SP, binder SBR, dispersant CMC and resin-based oil-absorbing microspheres are homogenized in a mass ratio of 95.7:2:1:1:0.3 to obtain a negative electrode slurry, which is then coated into a pole piece.

[0109] Example 4

[0110] A method for preparing a negative electrode sheet comprises the following steps:

[0111] 1. Preparation of resin-based oil-absorbing microspheres

[0112] Resin-based oil-absorbing microspheres were prepared according to the method of Example 1.

[0113] 2. Preparation of negative electrode active materials

[0114] The negative electrode active material was prepared according to the method of Example 2.

[0115] 3. Preparation of negative electrode sheet

[0116] The negative electrode active material, conductive agent SP, binder SBR, dispersant CMC and resin-based oil-absorbing microspheres are homogenized in a mass ratio of 95.5:2:1:1:0.5 to obtain a negative electrode slurry, which is then coated into a pole piece.

[0117] Example 5

[0118] A method for preparing a negative electrode sheet differs from Example 4 in that:

[0119] 3. Preparation of negative electrode sheet

[0120] The negative electrode active material, conductive agent SP, binder SBR, dispersant CMC and resin-based oil-absorbing microspheres are homogenized in a mass ratio of 95.2:2:1:1:0.8 to obtain a negative electrode slurry, which is then coated into a pole piece.

[0121] Example 6

[0122] A method for preparing a negative electrode sheet differs from Example 4 in that:

[0123] 1. Preparation of resin-based oil-absorbing microspheres

[0124] (a) A polystyrene solution (molecular weight 80,000, solvent: tetrahydrofuran, concentration 10%) and a fluorinated polyurethane prepolymer solution (IPDI-PFPE system, NCO content 8%, solvent: tetrahydrofuran, concentration 20%, prepared as in Example 1) were mixed in a solution mass ratio of 4:6, tetrahydrofuran was added to adjust the solid content to 12%, sodium chloride porogen (50 nm sodium chloride accounting for 30% of the total solid content) was added, and ultrasonic dispersion was performed for 30 min. Span 80, an oil phase emulsifier (Span 80 accounting for 2% of the oil phase mass) was added, and magnetic stirring was performed for 1 h to obtain a first material.

[0125] (b) Dissolve 1% polyvinyl alcohol and 0.5% ammonium persulfate in deionized water, and heat to 50° C. to dissolve to obtain a second material.

[0126] (c) The first material obtained above was slowly added to the second material, with a volume ratio of the first material to the second material of 1:20, and high-speed shear emulsification was adopted with a shear rate of 20,000 r / min and a shear time of 60 min to obtain a third material.

[0127] (d) The third material was magnetically stirred at a stirring speed of 500 r / min and a temperature of 50° C., and tetrahydrofuran was continuously volatilized until the residual amount of tetrahydrofuran was 50%, thereby obtaining a concentrated liquid material.

[0128] (e) adding 0.1% (mass percentage) of triethylamine to the liquid phase material to catalyze the crosslinking of the fluorinated polyurethane prepolymer, and continuing heating with magnetic stirring until the tetrahydrofuran is completely volatilized to obtain a semi-finished resin microsphere product.

[0129] (f) The semi-finished resin microspheres were washed with hot water at 60° C. to remove sodium chloride, and the microspheres were collected by centrifugation and dried under vacuum for 24 h, and kept at 30° C. to obtain the target product, resin-based oil-absorbing microspheres, having a particle size Dv50 = 0.8 μm, a weight-average molecular weight of 250,000, and a chloroform absorption rate of 70 g / g.

[0130] Example 7

[0131] A method for preparing a negative electrode sheet differs from Example 4 in that:

[0132] 1. Preparation of resin-based oil-absorbing microspheres

[0133] (a) A polystyrene solution (molecular weight 80,000, solvent: tetrahydrofuran, concentration 10%) and a fluorinated polyurethane prepolymer solution (IPDI-PFPE system, NCO content 8%, solvent: tetrahydrofuran, concentration 20%, prepared as in Example 1) were mixed in a solution mass ratio of 2:8, tetrahydrofuran was added to adjust the solid content to 12%, sodium chloride porogen (50 nm sodium chloride accounting for 30% of the total solid content) was added, and ultrasonic dispersion was performed for 30 min. An oil phase emulsifier, Span 80, was added (Span 80 accounting for 2% of the oil phase mass), and magnetic stirring was performed for 1 h to obtain a first material.

[0134] (b) Dissolve 1% polyvinyl alcohol and 0.5% ammonium persulfate in deionized water, and heat to 50° C. to dissolve to obtain a second material.

[0135] (c) The first material obtained above was slowly added to the second material, with the volume ratio of the first material to the second material being 1:10, and high-speed shear emulsification was adopted with a shear rate of 10,000 r / min and a shear time of 10 min to obtain a third material.

[0136] (d) The third material was magnetically stirred at a stirring speed of 500 r / min and a temperature of 50° C., and tetrahydrofuran was continuously volatilized until the residual amount of tetrahydrofuran was 50%, thereby obtaining a concentrated liquid material.

[0137] (e) adding 1.0% (mass percentage) of triethylamine to the liquid phase material to catalyze the crosslinking of the fluorinated polyurethane prepolymer, and continuing heating with magnetic stirring until the tetrahydrofuran is completely volatilized to obtain a semi-finished resin microsphere product.

[0138] (f) The semi-finished resin microspheres were washed with hot water at 60° C. to remove sodium chloride, and the microspheres were collected by centrifugation and dried under vacuum for 24 h, while maintaining the temperature at 30° C. to obtain the target product, resin-based oil-absorbing microspheres, having a particle size Dv50 of 3.5 μm, a weight-average molecular weight of 600,000, and a chloroform absorption rate of 40 g / g.

[0139] Comparative Example 1

[0140] A method for preparing a negative electrode sheet comprises the following steps:

[0141] The negative electrode active material was prepared according to the method of Example 4.

[0142] The negative electrode active material, conductive agent SP, binder SBR and dispersant CMC were homogenized in a mass ratio of 96:2:1:1 to obtain a negative electrode slurry, which was then coated into a pole piece.

[0143] Comparative Example 2

[0144] A method for preparing a negative electrode sheet differs from Example 4 in that:

[0145] 3. Preparation of negative electrode sheet

[0146] The negative electrode active material, conductive agent SP, binder SBR, dispersant CMC and resin-based oil-absorbing microspheres are homogenized in a mass ratio of 95.8:2:1:1:0.2 to obtain a negative electrode slurry, which is then coated into a pole piece.

[0147] Comparative Example 3

[0148] A method for preparing a negative electrode sheet differs from Example 4 in that:

[0149] 3. Preparation of negative electrode sheet

[0150] The negative electrode active material, conductive agent SP, binder SBR, dispersant CMC and resin-based oil-absorbing microspheres are homogenized in a mass ratio of 95:2:1:1:1 to obtain a negative electrode slurry, and the negative electrode slurry is coated into a pole piece.

[0151] Comparative Example 4

[0152] A method for preparing a negative electrode sheet differs from Example 4 in that:

[0153] 1. Preparation of resin-based oil-absorbing microspheres

[0154] (a) A polystyrene solution (molecular weight 80,000, solvent: tetrahydrofuran, concentration 10%) and a fluorinated polyurethane prepolymer solution (IPDI-PFPE system, NCO content 8%, solvent: tetrahydrofuran, concentration 20%) were mixed in a solution mass ratio of 5:5, tetrahydrofuran was added to adjust the solid content to 12%, sodium chloride porogen (50 nm sodium chloride accounting for 30% of the total solid content) was added, and ultrasonic dispersion was performed for 30 minutes. An oil phase emulsifier, Span 80, was added (Span 80 accounting for 2% of the oil phase mass), and magnetic stirring was performed for 1 hour to obtain a first material.

[0155] (b) Dissolve 1% polyvinyl alcohol and 0.5% ammonium persulfate in deionized water, and heat to 50° C. to dissolve to obtain a second material.

[0156] (c) The first material obtained above was slowly added to the second material, with a volume ratio of the first material to the second material of 1:25, and high-speed shear emulsification was adopted with a shear rate of 25000 r / min and a shear time of 70 min to obtain a third material.

[0157] (d) The third material was magnetically stirred at a stirring speed of 500 r / min and a temperature of 50° C., and tetrahydrofuran was continuously volatilized until the residual amount of tetrahydrofuran was 50%, thereby obtaining a concentrated liquid material.

[0158] (e) adding 0.08% (mass percentage) of triethylamine to the liquid phase material to catalyze the crosslinking of the fluorinated polyurethane prepolymer, and continuing heating with magnetic stirring until the tetrahydrofuran is completely volatilized to obtain a semi-finished resin microsphere product.

[0159] (f) The semi-finished resin microspheres were washed with hot water at 60° C. to remove sodium chloride, and the microspheres were collected by centrifugation and dried under vacuum for 24 h, while maintaining the temperature at 30° C. to obtain the target product, resin-based oil-absorbing microspheres, having a particle size Dv50 of 0.7 μm, a weight-average molecular weight of 200,000, and a chloroform absorption rate of 75 g / g.

[0160] Comparative Example 5

[0161] A method for preparing a negative electrode sheet differs from Example 4 in that:

[0162] 1. Preparation of resin-based oil-absorbing microspheres

[0163] (a) A polystyrene solution (molecular weight 80,000, solvent: tetrahydrofuran, concentration 10%) and a fluorinated polyurethane prepolymer solution (IPDI-PFPE system, NCO content 8%, solvent: tetrahydrofuran, concentration 20%) were mixed in a solution mass ratio of 1:9, tetrahydrofuran was added to adjust the solid content to 12%, sodium chloride porogen (50 nm sodium chloride accounting for 30% of the total solid content) was added, and ultrasonic dispersion was performed for 30 minutes. An oil phase emulsifier, Span 80, was added (Span 80 accounting for 2% of the oil phase mass), and magnetic stirring was performed for 1 hour to obtain a first material.

[0164] (b) Dissolve 1% polyvinyl alcohol and 0.5% ammonium persulfate in deionized water, and heat to 50° C. to dissolve to obtain a second material.

[0165] (c) The first material obtained above was slowly added to the second material, with a volume ratio of the first material to the second material of 1:5, and high-speed shear emulsification was adopted with a shear speed of 8000 r / min and a shear time of 8 min to obtain a third material.

[0166] (d) The third material was magnetically stirred at a stirring speed of 500 r / min and a temperature of 50° C., and tetrahydrofuran was continuously volatilized until the residual amount of tetrahydrofuran was 50%, thereby obtaining a concentrated liquid material.

[0167] (e) adding 1.1% (mass percentage) of triethylamine to the liquid phase material to catalyze the crosslinking of the fluorinated polyurethane prepolymer, and continuing heating with magnetic stirring until the tetrahydrofuran is completely volatilized to obtain a semi-finished resin microsphere product.

[0168] (f) The semi-finished resin microspheres were washed with hot water at 60° C. to remove sodium chloride, and the microspheres were collected by centrifugation and dried under vacuum for 24 h, while maintaining the temperature at 30° C. to obtain the target product, resin-based oil-absorbing microspheres, having a particle size Dv50 of 3.6 μm, a weight-average molecular weight of 650,000, and a chloroform absorption rate of 35 g / g.

[0169] Comparative Example 6

[0170] A method for preparing a negative electrode sheet differs from Example 4 in that:

[0171] 2. Preparation of negative electrode active materials

[0172] Except that the mass ratio of material C to polyaryl silicone resin high temperature resistant anticorrosive coating TPSIV 3040-70A BK is 80:20, other conditions are the same as those in Example 4.

[0173] Comparative Example 7

[0174] A method for preparing a negative electrode sheet differs from Example 4 in that:

[0175] 2. Preparation of negative electrode active materials

[0176] Except that the mass ratio of material C to polyaryl silicone resin high temperature resistant anticorrosive coating TPSIV 3040-70ABK is 98:2, other conditions are the same as those in Example 4.

[0177] Comparative Example 8

[0178] A method for preparing a negative electrode sheet differs from Example 4 in that:

[0179] 2. Preparation of negative electrode active materials

[0180] (1) Conventional pulverization of petroleum coke to obtain material A, the particle size of material A is Dv50 = 10 μm.

[0181] (2) Material A is mixed with coal tar and granulated to obtain material B. The particle size Dv50 of material B is 16 μm.

[0182] (3) Material B was graphitized at 3000°C for 12 hours in an argon atmosphere to obtain material C. The particle size of material C was 15 μm.

[0183] (4) The mass ratio of material C to coal tar pitch is 90:10. Carbonization is carried out at 1500°C for 2 h under nitrogen atmosphere to obtain material D, which is the negative electrode active material.

[0184] Experimental example

[0185] 1. Performance Characterization of Resin-Based Microspheres

[0186] Test of the absorption rate of chloroform by resin-based microspheres: Place the resin-based oil-absorbing microspheres in a 50°C oven and dry them to constant weight to remove surface moisture and impurities. Accurately weigh the dried microspheres (e.g., 1.00 g) and place them in a container. Slowly add chloroform with a dropper while stirring with a glass rod until the microspheres are completely wetted. Record the initial chloroform mass. Place the mixed system in a constant temperature oscillator (25°C) and oscillate at 150 r / min for 24 hours to adsorption equilibrium. Separate the adsorbed microspheres through a filter or centrifuge, remove unadsorbed chloroform, measure the mass of the adsorbed microspheres, and calculate the adsorption rate. Oil absorption rate (g / g) = (mass of microspheres after adsorption - initial mass of microspheres) / initial mass of microspheres.

[0187] Table 1 Performance characterization of resin-based microspheres

[0188] Group Weight average molecular weight <![CDATA[Particle size D v 50 (μm)]]> Oil absorption rate (g / g) Example 1 400,000 2.0 60 Example 2 400,000 2.0 60 Example 3 400,000 2.0 60 Example 4 400,000 2.0 60 Example 5 400,000 2.0 60 Example 6 250,000 0.8 70 Example 7 600,000 3.5 40 Comparative Example 4 200,000 0.7 75 Comparative Example 5 650,000 3.6 35

[0189] 2. Silicon content test of composite graphite particles

[0190] Inductively coupled plasma optical emission spectrometry (ICP-OES) was used. The powder was treated with a mixed acid system of nitric acid and hydrofluoric acid (4:1 ratio). Microwave digestion was performed at 180°C for 20 minutes. Boric acid was added after digestion to complex the free fluoride ions. ICP radio frequency power was 1.2 kW, nebulizer gas flow rate was 0.5-1.0 L / min, auxiliary gas flow rate was 1.5 L / min, and the observation height was 10 mm.

[0191] Detection wavelength: Select the silicon characteristic spectrum line 251.611nm. Use 1000mg / L silicon standard solution as the mother solution, dilute it step by step with 1% nitric acid to a concentration gradient of 0-100mg / L, and simultaneously prepare matrix matching solution (such as containing coexisting elements such as aluminum and iron) to eliminate the matrix effect. Use the instrument software to automatically fit the calibration curve (R 2 ≥0.999), the silicon concentration was calculated based on the sample signal intensity and converted into mass percentage based on the dilution factor and sample mass.

[0192] Table 2 Test of silicon content of composite graphite particles

[0193]

[0194]

[0195] 3. Battery performance test

[0196] The negative electrode sheets obtained in each embodiment and comparative example were used to prepare 4680 cylindrical battery cells.

[0197] The battery cells are subjected to the following performance tests:

[0198] 1.50% SOC charging DCR

[0199] The battery cell was charged to 50% SOC at a current of 0.5C and allowed to stand at 25°C for 60 minutes to eliminate the battery polarization effect. After adjusting to 50% SOC, the battery cell was short-term charged for 30 seconds using a constant current of 4C. The charge start voltage V1 and end voltage V2 were recorded. The charge DCR = |V2-V1| / I, where I is the charging current value.

[0200] 2.4C rate charging lithium deposition SOC point

[0201] Select battery cells with good consistency, activate them for 3 weeks and fix the capacity; use 4C current to charge to different SOC, and then let it stand. During the standing period, the lithium precipitated on the surface of the active material will enter the active material, and a small reaction platform will exist; record the voltage change during the standing process, record the voltage change curve and dV / dT curve, and then judge the lithium deposition characteristics of the negative electrode.

[0202] Table 3 Battery performance test results

[0203]

[0204]

[0205] From the above, it can be seen that in Examples 1 to 3 of the present invention, the particle size of the resin-based oil-absorbing microspheres is 2 μm and the content is 0.3%. As the content of silicon nanoparticles in the active material decreases (0.2 to 0.05%), the fast charging performance of the electrode first increases and then decreases. Although an excessively high content of silicon nanoparticles can improve the wettability of the electrolyte, it will lead to a decrease in the electronic conductivity of the active material particles.

[0206] It can be seen from Examples 2 and 4 to 5 of the present invention that when the silicon content of the active material particles is maintained at 0.1% and the particle size of the resin-based oil-absorbing microspheres is 2 μm, as the content of the resin-based oil-absorbing microspheres in the electrode increases (0.3 to 0.8%), the 4C rate charging lithium deposition SOC point of the battery cell first increases and then decreases. Increasing the content of resin-based oil-absorbing microspheres within a certain range can improve the ionic conductivity of the electrode, but when the content of resin-based oil-absorbing microspheres is too high, the electronic conductivity of the electrode will decrease, which is not conducive to the fast charging performance of the battery cell.

[0207] It can be seen from Examples 2 and 6 to 7 of the present invention that when the silicon nanoparticle content in the active material particles is maintained at 0.1% and the resin-based oil-absorbing microsphere content is maintained at 0.5%, as the particle size of the resin-based oil-absorbing microsphere particles increases (0.8 to 3.5 μm), the 4C rate charging lithium deposition SOC point of the battery cell first increases and then decreases. Although small-particle resin microspheres can absorb a large amount of electrolyte and increase the uniformity of dispersion of the resin-based oil-absorbing microspheres around the active material, too small resin-based oil-absorbing microsphere particles will be suspended between the active material particles, which is not conducive to the release of electrolyte during the squeezing of the resin-based oil-absorbing microspheres by the active material particles when the electrode expands, and the ionic conductivity will decrease instead. Excessively large particles will lead to insufficient number of resin-based oil-absorbing microspheres per unit mass, and the resin-based oil-absorbing microspheres are not evenly distributed around the active material, which is not conducive to improving the ionic conductivity of the electrode, resulting in an unclear improvement in the fast charging performance of the battery cell.

[0208] Comparative Example 1 does not contain resin-based oil-absorbing microspheres. During the 4C charging process, as the stress of the electrode increases, the porosity between the electrode and the particles decreases, the electrolyte is squeezed to the end of the battery cell, and the electrolyte around the active material is scarce, resulting in an increase in the 50% SOC charging DCR of the battery cell. When the polarization increases, lithium is deposited prematurely on the surface of the negative electrode, which manifests as the lithium deposition SOC of the battery cell being too low.

[0209] Comparative Example 2 contains resin-based oil-absorbing microspheres, but the content is too low (0.2%). The resin-based microspheres are scattered at few points around the negative electrode active material, and the improvement of the ionic conductivity of the battery cell during high-rate charging is not obvious, resulting in a large concentration polarization of the battery cell, which is not conducive to high-rate charging.

[0210] Comparative Example 3 contains resin-based oil-absorbing microspheres, but the content is too high (1%). Although a large amount of oil-absorbing resin microspheres are added, which improves the problem of difficulty in retaining the electrolyte in the electrode and reduced ion conductivity caused by stress extrusion during the expansion of the electrode, resin is a poor conductor of electrons. Excessive addition will reduce the electronic conductivity of the electrode and will have a certain adverse effect on the improvement of fast charging performance.

[0211] In comparative example 4, an appropriate amount of resin-based oil-absorbing microspheres was added, but the particle size of the microspheres was too small (0.7 μm). At this time, most of the microspheres were distributed between the active material particles and were suspended in space. They were not in close contact with the active particles and were not squeezed by the particles. During the high-rate charging of the battery cell, most of the electrolyte in the resin-based oil-absorbing microspheres could not be released, and the improvement in the effective liquid retention performance of the electrode was not obvious, resulting in little improvement in the ionic conductivity of the electrode, no obvious reduction in concentration polarization, and no obvious improvement in fast charging performance.

[0212] Comparative Example 5 adds an appropriate amount of resin-based oil-absorbing microspheres, but the particle size of the microspheres is too large (3.6 μm) and the volume of the microspheres is too large, which will result in a small number of microspheres per unit mass and a reduced number of microsphere points distributed in the electrode, reducing the improvement of the resin-based oil-absorbing microspheres on the electrode liquid retention performance. However, large-sized microspheres will be in close contact with adjacent particles during the electrode rolling process. During the high-rate charging process of the battery cell, as the expansion stress of the electrode and active material particles increases, the microspheres release electrode liquid into the electrode or on the surface of the active material particles, thereby improving the ionic conductivity of the electrode and reducing the polarization of the battery cell.

[0213] The negative electrode active material of Comparative Example 6 contains a large amount of nano-silicon particles (0.23%), which greatly improves the wettability of the electrolyte on the surface of the active material particles. However, nano-silicon is a poor conductor of electrons, which leads to a decrease in the electronic conductivity of the electrode, which is not conducive to the fast charging performance of the battery cell.

[0214] The negative electrode active material of Comparative Example 7 contains a small amount of nano-silicon particles (0.02%), and the electrode liquid has insufficient wettability on the surface of the active material particles. After the electrode is squeezed, the electrolyte released from the resin-based oil-absorbing microspheres cannot quickly diffuse to the surface of the active material particles, which is not conducive to improving the ionic conductivity of the electrode, and the fast charging performance of the battery cell is adversely affected.

[0215] The negative electrode active material of Comparative Example 8 does not contain nano-silicon particles. The diffusion and extension resistance of the electrolyte on the surface of the active material particles is relatively large. The surface of the negative electrode active material is smooth, the polarity is relatively low, and the affinity with the polar electrolyte is relatively poor, which is not conducive to the rapid diffusion of the electrolyte on the surface of the active material, hindering the improvement of the fast charging performance of the battery cell, and the DCR is relatively increased, and the 4C fast charging performance is reduced.

[0216] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pole piece, characterized in that: The invention comprises a pole piece material, wherein the pole piece material contains resin-based oil-absorbing microspheres, the resin-based oil-absorbing microspheres are elastic bodies with a porous structure, and the absorption rate of the resin-based microspheres to chloroform is 40-70 g / g.

2. The pole piece according to claim 1, characterized in that: The resin-based microspheres have an absorption rate of chloroform of 55 to 70 g / g.

3. The pole piece according to claim 1, characterized in that: Contains at least one of the following features (1) to (4): (1) The resin-based oil-absorbing microspheres include polystyrene-polyurethane composite microspheres; (2) The mass proportion of the resin-based oil-absorbing microspheres in the electrode material is 0.3% to 0.8%; (3) The particle size D of the resin-based oil-absorbing microspheres v 50 is 0.8~3.5μm; (4) The weight average molecular weight of the lipid-based oil-absorbing microspheres is 250,000 to 600,000.

4. The pole piece according to claim 3, characterized in that: Contains at least one of the following features (1) to (3): (1) The mass proportion of the resin-based oil-absorbing microspheres in the electrode material is 0.4% to 0.6%; (2) The particle size D of the resin-based oil-absorbing microspheres v 50 is 1.5~3μm; (3) The weight average molecular weight of the lipid-based oil-absorbing microspheres is 300,000 to 500,000.

5. The pole piece according to any one of claims 1 to 4, characterized in that: The electrode material also includes negative electrode active material.

6. The pole piece according to claim 5, characterized in that: The negative electrode active material includes composite graphite particles; preferably, the composite graphite particles include a graphite core, an amorphous carbon layer coated on the surface of the graphite core, and nano-silicon dioxide particles located in the amorphous carbon layer, and the nano-silicon dioxide particles are at least embedded in the amorphous carbon surface.

7. The pole piece according to claim 6, characterized in that: The silicon content of the composite graphite particles is 0.05% to 0.2%.

8. The pole piece according to claim 5, characterized in that: The pole piece material further includes a binder, and / or a conductive agent, and / or a dispersant.

9. A battery, characterized in that: The invention comprises the pole piece according to any one of claims 1 to 8.

10. An electrical device, characterized in that: A battery comprising the battery of claim 9.

Images