CN112467079A - Silicon-containing negative plate and lithium ion battery comprising same - Google Patents

Silicon-containing negative plate and lithium ion battery comprising same Download PDF

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Publication number
CN112467079A
CN112467079A CN202011401546.XA CN202011401546A CN112467079A CN 112467079 A CN112467079 A CN 112467079A CN 202011401546 A CN202011401546 A CN 202011401546A CN 112467079 A CN112467079 A CN 112467079A
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active layer
electrode sheet
negative electrode
graphite
active
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韦世超
彭冲
陈博
李俊义
徐延铭
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Zhuhai Cosmx Battery Co Ltd
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Zhuhai Cosmx Battery Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention discloses a silicon-containing negative plate and a lithium ion battery comprising the same. The contact angle of the first active layer active material and the non-aqueous solvent is theta 1, the porosity of the first active layer active material is a, and the contact angle of the bottom layer active material and the non-aqueous solvent is theta2The porosity of which is b, then 100<θ1/a<θ2/b<450, through the specific structure, because silicon expands greatly in the charging and discharging process, the porosity of the surface layer pole piece is favorably improved, so that the liquid retention capacity of the battery is improved. Meanwhile, the surface of the silica contains multifunctional groups, and the particles of the silica are smaller than those of graphite particles, so that the energy density, the liquid retention capacity and the cycle life of the battery can be obviously improved.

Description

Silicon-containing negative plate and lithium ion battery comprising same
Technical Field
The invention relates to the field of batteries, in particular to a silicon-containing negative plate and a lithium ion battery comprising the same.
Background
Nowadays, lithium ion batteries have become main energy storage devices of mainstream electronic products, and with the improvement of the performance requirements of people on batteries, a lithium ion battery with excellent performance does not only need to have higher energy density, but also needs to have long cycle life. At present, the thickness of a pole piece is reduced mainly by improving the compactness of the pole piece, so that the energy density of a battery is increased. However, the high compactness can cause low porosity of the pole piece, thereby reducing the liquid retention of the battery.
The silica material can improve the energy density of the battery due to higher gram capacity; meanwhile, the silicon has larger cyclic expansion in the charge-discharge process, so the porosity of the pole piece after the cycle is larger. Therefore, it is widely used in lithium ion batteries. However, the contact angle between simple silica particles and a nonaqueous solvent is too small, and the wettability of an electrolyte solution is too high when the silica particles are applied to the surface of an electrode sheet. Therefore, how to make the electrode plate and the electrolyte have proper wettability and improve the energy density, the liquid retention amount and the cycle life of the battery becomes a technical problem to be solved urgently.
Disclosure of Invention
In order to improve the technical problem, the invention provides a silicon-containing negative plate and a lithium ion battery comprising the same, wherein the negative plate has a double-layer structure, a graphite layer is arranged on a layer close to a current collector, and a silicon-oxygen and graphite mixed layer is arranged on a layer far away from the current collector. The wettability of the electrolyte is improved by mixed coating of silica and graphite, so that the energy density, the liquid retention capacity and the cycle life of the battery are obviously improved.
The invention realizes the technical effects through the following technical scheme:
a lithium ion battery negative plate comprises a current collector, a first active layer and a second active layer, wherein the second active layer is arranged between the current collector and the first active layer; the contact angle of the first active layer and a non-aqueous solvent is theta 1, and the porosity of the first active layer is a; the second active layer has a contact angle with a non-aqueous solvent of theta 2 and a porosity of b, and then the contact angle is 100< (theta 1/a) < (theta 2/b) < 450.
According to an exemplary embodiment of the invention, θ 1/a is 120, 150, 180, 200, 250, 300, 350, or any point value between any two combinations of the above.
Preferably, θ 1/a is 150, 200, 250, 300, 350, or any point between any two combinations of the foregoing; and theta 2/b is 400.
According to an embodiment of the invention, in the first active layer, 20 ° < θ 1<60 °, 20% < a < 35%; in the second active layer, 40 ° < θ 2<90 °, 15% < b < 25%. The first active layer is controlled to have a smaller contact angle with a non-aqueous solvent and a larger porosity, so that better infiltration of electrolyte can be ensured, and the liquid retention of the battery can be improved.
According to an embodiment of the present invention, the compacted density of the first active layer of the negative electrode sheet in a state after charging (SOC 50%) is 1.3 to 1.6g/mm3And the compacted density of the second active layer of the negative electrode sheet in a state after charging (SOC is 50%) is 1.5-1.75g/mm3。
According to an embodiment of the present invention, the active material in the first active layer is a silicon oxide material and graphite, and the active material in the second active layer is graphite.
According to an embodiment of the invention, in the first active layer, the percentage of the silicon oxide material to the total weight of the active substances (silicon oxide material and graphite) is 0-40% (not 0); preferably 2-30%; exemplary are 10%, 15%, 20%, 25%, 30%, 35%, 40%.
According to an embodiment of the invention, the silicon oxygen material has the chemical formula SiOXWherein 0.5<X<2。
According to an embodiment of the invention, the silicone material is particles having a particle size D50 ═ 1 to 10 μm.
According to an embodiment of the present invention, the first active layer further contains a binder. For example, the binder comprises 1-5% of the total weight of the first active layer; preferably 3 to 5%.
According to the embodiment of the present invention, the contact angle of the first active layer with the non-aqueous solvent can be controlled by adjusting the amount ratio of the binder in the first active layer; meanwhile, the semi-electric rebound performance of the charged negative plate can be regulated and controlled by regulating and controlling the dosage ratio of the silicon-oxygen material in the first active layer, so that the porosity of the first active layer can be regulated and controlled. Furthermore, the porosity of the first active layer gradually increases with the increase of the silicon oxide content, and when the silicon oxide material is used in an amount of 0-40%, the porosity of the first active layer is ensured to be 15-32%.
According to an embodiment of the present invention, the graphite in the first and second active layers is at least one of natural graphite or artificial graphite.
According to an embodiment of the present invention, the graphite in the first and second active layers is particles having a particle size of D50 ═ 10 to 20 μm.
According to an embodiment of the present invention, the first active layer and the second active layer further contain an auxiliary agent, such as one or more of a conductive agent, a binder, and a dispersant.
According to an embodiment of the present invention, the conductive agent is at least one of conductive carbon black Super P, vapor grown carbon fiber VGCF, graphene, or carbon nanotube CNTs.
According to an embodiment of the present invention, the binder of the first active layer is one, two or more combinations of polyacrylic acid, lithium polyacrylate, or sodium polyacrylate. The adhesive of the second active layer is water-based adhesive; preferably, the aqueous binder is at least one of Styrene Butadiene Rubber (SBR), nitrile rubber, butadiene rubber, modified styrene butadiene rubber, sodium polyacrylate (PAANa), aqueous polyacrylonitrile copolymer and polyacrylate.
According to an embodiment of the present invention, the dispersant is sodium carboxymethyl cellulose (CMC) or a polyether modified silicone polymer; preferably sodium carboxymethylcellulose (CMC).
According to an embodiment of the invention, the current collector is made of copper foil or porous copper foil; for example, the copper foil may be one of a microporous copper foil and a carbon-coated copper foil.
According to an embodiment of the present invention, the first active layer has a thickness after rolling of 10 to 50 μm; preferably 20-40 μm; exemplary are 10 μm, 20 μm, 30 μm, 40 μm, 50 μm.
According to an embodiment of the invention, the thickness of the second active layer is higher than the thickness of the first active layer.
According to an embodiment of the present invention, the second active layer is coated to a thickness of 20 to 70 μm; preferably 40-50 μm; exemplary are 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm.
According to an embodiment of the invention, said two active layers are formed on at least one surface of said current collector; preferably, formed on both surfaces of the current collector.
The invention also provides a preparation method of the negative plate, which comprises the following steps: preparing first active layer slurry containing silicon-oxygen material and graphite as active substances and second active layer slurry containing graphite as active substances, and coating the slurry on at least one surface of a current collector to form a second active layer and a first active layer so as to obtain the negative electrode sheet.
According to the embodiment of the invention, the preparation method of the negative plate adopts a double-layer coating machine; the coating is preferably carried out using a twin die head die coater.
According to an embodiment of the invention, the preparation method of the negative electrode sheet comprises the following steps:
1) dispersing a silica material, graphite, a binder and optionally other auxiliary agents in a solvent to obtain first active layer slurry;
2) dispersing graphite and optional other auxiliary agents in a solvent to obtain second active layer slurry;
3) a double-die coating head extrusion type coating machine is adopted to simultaneously coat the second active layer slurry and the first active layer slurry on the same side of the negative current collector to form a double-coating structure; wherein the second active layer is close to the current collector layer and the first active layer is far from the current collector; optionally, to the other side of the current collector.
According to an embodiment of the present invention, the solvent is a non-aqueous solvent; preferably, the nonaqueous solvent is at least one of ethylene carbonate, diethyl carbonate, dimethyl carbonate, and the like.
The invention also provides application of the negative plate in a lithium ion battery.
The invention also provides a lithium ion battery, which comprises the negative plate.
According to an embodiment of the present invention, the lithium ion battery further contains an electrolyte, a separator, and a positive electrode sheet.
According to the embodiment of the invention, the active material of the positive plate is one or more of lithium cobaltate and lithium nickel manganese cobalt oxide.
According to an embodiment of the present invention, the positive electrode sheet further contains one or more of an auxiliary agent, such as a conductive agent, and a binder.
According to the embodiment of the invention, the conductive agent comprises one or more of conductive carbon black super P, nano wires, carbon nano tubes and graphene.
According to an embodiment of the invention, the binder is selected from at least one of polyvinylidene fluoride (PVDF), copolymers of vinylidene fluoride-hexafluoropropylene, polyamides, polyacrylonitrile, polyacrylates, polyacrylic acids, polyacrylates, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, and styrene-butadiene rubber; preferably polytetrafluoroethylene.
According to the embodiment of the invention, the positive plate is a lithium ion battery positive plate, and the current collector of the positive plate is one of an aluminum foil or a microporous aluminum foil.
The invention also provides a preparation method of the lithium ion battery, which comprises the following steps: and (3) matching and winding the negative electrode sheet and the positive electrode sheet → packaging → baking injection → formation → secondary packaging → sorting and the like to obtain the lithium ion battery.
Furthermore, the porosity in the invention refers to the ratio of the volume of the pores of the pole piece after charging and discharging to the total volume of the pole piece, and the unit is one hundred percent (%).
Has the advantages that:
(1) the invention adopts a double-layer coating technology, a graphite layer is coated on the layer of the negative plate close to the current collector, and a silica and graphite mixed layer is coated on the layer far away from the current collector. Because silicon expands greatly in the charging and discharging process, the porosity of the surface pole piece is favorably improved so as to improve the liquid retention of the battery. Meanwhile, the surface of the silica contains polyfunctional groups, the particles of the silica are smaller than those of graphite particles, the contact angle between the silica particles and a non-aqueous solvent is far smaller than that between the graphite and the non-aqueous solvent, and the better hydrophilic performance of the polyacrylic acid adhesive is utilized by optimizing the dosage ratio of the silica material, the graphite and the polyacrylic acid adhesive, so that the hydrophilicity of the pole piece is favorably improved, and the contact angle between the pole piece and the non-aqueous solvent is regulated. In a certain range, the smaller the contact angle of the pole piece to the non-aqueous solvent is, the better the compatibility to the electrolyte is, and lithium ions are easier to transmit in the pole piece, so that the wettability of the electrolyte to the pole piece is improved by coating the mixed layer of silica particles and graphite on the surface layer. Meanwhile, the gram capacity of the silicon-oxygen particles is high, so that the gram capacity of the negative plate can be effectively improved, and the energy density of the battery is improved.
(2) The lithium ion battery negative electrode sheet has a double-layer structure, the contact angle of the first active layer active substance and a non-aqueous solvent is theta 1, the porosity of the first active layer active substance is a, and the contact angle of the second active layer active substance and the non-aqueous solvent is theta2The porosity of which is b, then 100<θ1/a<θ2/b<450, by the specific structure, the energy density, the liquid retention capacity and the cycle life of the battery can be obviously improved.
(3) The compacted density of the first active layer of the negative electrode sheet of the present invention in a charged state (SOC ═ 50%) is 1.3 to 1.6g/mm3And a compacted density of the second active layer in a state after charging (SOC ═ 50%) of 1.5 to 1.75g/mm3. Further, in the first active layer, 20 °<θ1<60°，20％<a<35 percent; in the second active layer, 40 °<θ2<90°，15％<b<25 percent. The first active layer is controlled to have a smaller contact angle with a non-aqueous solvent and a larger porosity, so that better infiltration of electrolyte can be ensured, and the liquid retention of the battery can be improved.
Drawings
FIG. 1 is a schematic structural diagram of a silicon-containing double-layer negative plate of a lithium ion battery according to the present invention.
In the figure: 1. a first active layer; 2. a second active layer; 3. and (4) a current collector.
Detailed Description
The technical solution of the present invention will be further described in detail with reference to specific embodiments. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.
Unless otherwise indicated, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.
In the contact angle property test of the following examples and comparative examples according to the present invention, a non-aqueous solvent of ethylene carbonate was used, and the contact angle thereof was measured in degrees by using a contact angle tester. Specifically, the contact angle of a droplet of a nonaqueous solvent at 25 ℃ in contact with the electrode sheet for 2 seconds is defined as the contact angle used in the present invention.
Further, the contact angle tester is a LSA200 model tester from LAUDA Scientific, germany.
Further, by testing the cross section of the negative plate by using an SEM (scanning electron microscope), the boundary of the double-layer structure of the negative plate can be observed, the thicknesses of the first active layers 1 are respectively obtained, and then the first active layers 1 are removed by using a pole piece cutting device, so that the thickness of the pole piece which only contains the second active layer 2 can be obtained.
Further, the contact angle of the first active layer 1 (surface layer) can be directly measured by using a contact angle tester, and the second active layer 2 (bottom layer) can also obtain a pole piece simply containing the second active layer 2 by using a mode of removing the active layer 1, and the corresponding contact angle of the second active layer 2 can be obtained by using the same mode.
Further, the porosity is measured by a vacuum densitometer, specifically, a ten-thousandth ruler is used to measure the apparent volume of the pole piece, the apparent volume is the thickness of the sample and the length of the sample and the width of the sample, and the porosity is (apparent volume-true volume)/apparent volume when the true volume of the sample is measured by the vacuum densitometer.
Example 1
As shown in fig. 1, the present embodiment provides a negative electrode sheet, including a current collector 3, a first active layer 1, and a second active layer 2, where the second active layer 2 is disposed between the current collector 3 and the first active layer 1, and the second active layer 2 is formed on two surfaces of the current collector 3.
The active material in the first active layer is graphite and silica material, the active material in the second active layer is graphite, and the current collector is formed by carbon-coated copper foil.
Preparing a lithium ion battery negative plate:
the active material, a conductive agent, a dispersing agent and a binding agent are mixed according to the mass ratio of 93%: 1.1%: 0.9%: 5 percent of the mixture is uniformly mixed and then dispersed in a hydrosolvent to prepare first active layer slurry; wherein the active substance consists of 60 percent of graphite and 40 percent of silica material by weight percentage;
the graphite, a conductive agent, a dispersing agent and a binder are mixed according to the mass ratio of 95.5%: 1.1%: 0.9%: 2.5 percent of the mixture is uniformly mixed and then dispersed in a water solvent to prepare second active layer slurry;
the conductive agent is composed of carbon black and a carbon nanotube in a ratio of 9:1, the binder in the first active layer slurry is lithium polyacrylate, and the dispersant is sodium carboxymethyl cellulose (CMC); the binder in the second active layer slurry is Styrene Butadiene Rubber (SBR), and the dispersant is sodium carboxymethylcellulose (CMC).
Placing the first active layer slurry and the second active layer slurry in a double-layer coating machine, adopting a double-die coating head extrusion type coating machine, simultaneously coating the 2 slurries on one surface of a negative current collector, forming a double-coating structure on the same side of the negative current collector, and preparing a double-layer coated negative plate with a silicon-containing first active layer on the top layer and a silicon-free pure graphite layer (second active layer) on the bottom layer; after one surface of the current collector is coated, the other surface is coated repeatedly according to the method.
Wherein the thickness of the first active layer 1 is 30 μm, and the thickness of the second active layer 2 is 50 μm.
The contact angle of the first active layer and a non-aqueous solvent is theta 1, and the porosity of the first active layer is a; the contact angle of the second active layer and the non-aqueous solvent is theta 2, and the porosity of the second active layer is b; in the present embodiment, θ 1/a is 150, and θ 2/b is 400.
Preparing a lithium ion battery:
preparing a lithium ion battery positive plate according to a conventional method in the field; the positive plate is composed of an active substance, a conductive agent and a binder according to the mass ratio of 97.8%: 1%: 1.2 percent of the mixture is uniformly mixed to prepare anode slurry, and the anode slurry is coated by an extrusion coating machine, rolled and cut to obtain a corresponding anode sheet;
the current collector of the positive plate is made of aluminum foil; the active substance is lithium cobaltate; the conductive agent is formed by mixing conductive carbon black super P and nanotubes in a mass ratio of 4:1, and the binder is polytetrafluoroethylene.
And (3) matching and winding the negative electrode sheet and the positive electrode sheet → packaging → baking injection → formation → secondary packaging → sorting and the like to obtain the lithium ion battery.
Example 2
The differences between the negative electrode sheet, the preparation method thereof and the lithium ion battery provided in this embodiment and embodiment 1 are: the active material in the first active layer consists of graphite with the weight percentage of 70% and silica with the weight percentage of 30%, and the active material in the first active layer 1, the conductive agent, the dispersing agent and the binding agent are 94% by mass: 1.1%: 0.9%: 4%, the ratio theta 1/a is 250, and the ratio theta 2/b is 400.
Other conditions were the same as in example 1.
Example 3
The difference between the negative electrode sheet, the preparation method thereof, and the lithium ion battery provided in this example and example 1 is that the active material in the first active layer is composed of 80 wt% of graphite and 20 wt% of silica, and the mass ratio of the active material in the first active layer 1 to the conductive agent, the dispersant, and the binder is 94.5%: 1.1%: 0.9%: 3.5%, the ratio theta 1/a is 300, and the ratio theta 2/b is 400.
Other conditions were the same as in example 1.
Example 4
The difference between the negative electrode sheet, the preparation method thereof, and the lithium ion battery provided in this embodiment and embodiment 1 is that the active material in the first active layer is composed of 90% graphite and 10% silicon oxygen by weight, and the mass ratio of the active material in the active layer 1 to the conductive agent, the dispersant, and the binder is 95%: 1.1%: 0.9%: 3%, the ratio theta 1/a is 350, and the ratio theta 2/b is 400.
Other conditions were the same as in example 1.
Comparative example 1
The negative electrode sheet, the method for preparing the same, and the lithium ion battery provided in this example are different from those of example 1 in that the negative electrode sheet is coated with only the second active layer slurry to a coating thickness of 80 μm.
Other conditions were the same as in example 1.
Examples 1-4, comparative example 1 lithium ion battery performance test.
The results of the measurement of the amount of residual liquid and the test of the 45 ℃ 1.5C/0.7C cycle of the above examples are shown in the following table, wherein the amount of residual liquid is measured by measuring the weight of the battery before the injection and after the secondary sealing, and the 1.5C/0.7C cycle method is specifically as follows: at 45 ℃, the lithium ion battery is charged to rated voltage by 1.5 ℃ and then discharged by 0.7 ℃, and the charging and discharging are both stopped by 0.05 ℃.
The observation that the capacity retention rate of the double-layer coated pole piece is excellent when the double-layer coated pole piece is used at the temperature of 45 ℃ and 200T in circulation shows that the energy density and the residual liquid amount of the battery can be effectively improved by using the special double-layer structure, and meanwhile, the high-temperature circulation performance of the battery is improved.
Figure BDA0002817101310000101
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. The negative plate of the lithium ion battery is characterized by comprising a current collector, a first active layer and a second active layer, wherein the second active layer is arranged between the current collector and the first active layer; the contact angle of the first active layer and a non-aqueous solvent is theta 1, and the porosity of the first active layer is a; the second active layer has a contact angle with a non-aqueous solvent of theta 2 and a porosity of b, and then the contact angle is 100< (theta 1/a) < (theta 2/b) < 450.
2. A negative electrode sheet according to claim 1, wherein, in the first active layer, 20 ° < θ 1<60 °, 20% < a < 35%; in the second active layer, 40 ° < θ 2<90 °, 15% < b < 25%.
3. The negative electrode sheet according to claim 1 or 2, wherein the compacted density of the first active layer of the negative electrode sheet in a state after charging (SOC-50%) is 1.3 to 1.6g/mm3And the compacted density of the second active layer of the negative electrode sheet in a state after charging (SOC is 50%) is 1.5-1.75g/mm3。
4. A negative electrode sheet according to any one of claims 1 to 3, wherein the active material in the first active layer is a silicon-oxygen material and graphite, and the active material in the second active layer is graphite;
in the first active layer, the silicon-oxygen material accounts for 0-40% (not 0) of the total weight of the silicon-oxygen material and the graphite; preferably 2-30%; the chemical formula of the silicon oxygen material is SiOXWherein 0.5<X<2；
Preferably, the silicone material is in the form of particles having a particle size of D50 ═ 1 to 10 μm.
5. The negative electrode sheet according to any one of claims 1 to 4, wherein the first active layer further comprises a binder, the binder comprising 1 to 5% by weight of the total weight of the first active layer;
the graphite in the first active layer and the second active layer is at least one of natural graphite or artificial graphite;
preferably, the graphite in the first and second active layers is in the form of particles having a particle size D50 ═ 10 to 20 μm.
6. The negative electrode sheet according to any one of claims 1 to 5, wherein the first active layer and the second active layer further comprise an auxiliary agent comprising one or more of a conductive agent, a binder, and a dispersant.
7. The negative electrode sheet of claim 6, wherein the conductive agent is at least one of conductive carbon black Super P, vapor grown carbon fiber VGCF, graphene, or carbon nanotube CNTs;
the binder of the first active layer is one or a combination of two or more of polyacrylic acid, lithium polyacrylate or sodium polyacrylate; the adhesive of the second active layer is water-based adhesive; for example, the aqueous binder is at least one of Styrene Butadiene Rubber (SBR), nitrile butadiene rubber, modified styrene butadiene rubber, sodium polyacrylate (PAANa), aqueous polyacrylonitrile copolymer and polyacrylate;
the dispersing agent is sodium carboxymethylcellulose (CMC) or polyether modified organic silicon polymer;
the current collector is composed of a copper foil or a porous copper foil.
8. The negative electrode sheet according to any one of claims 1 to 7, wherein the rolled thickness of the first active layer is 10 to 50 μm; the coating thickness of the second active layer is 20-70 μm.
9. The negative electrode sheet according to any one of claims 1 to 8, wherein the two active layers are formed on at least one surface of the current collector; preferably, formed on both surfaces of the current collector.
10. A lithium ion battery comprising the negative electrode sheet according to any one of claims 1 to 9.
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CN114005958A (en) * 2021-10-15 2022-02-01 珠海冠宇电池股份有限公司 Silicon-carbon composite structure's negative pole piece reaches battery including this negative pole piece
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CN114068867A (en) * 2021-11-24 2022-02-18 蜂巢能源科技有限公司 Lithium-supplementing negative plate and lithium ion battery
CN114335521A (en) * 2021-11-22 2022-04-12 惠州市豪鹏科技有限公司 Negative plate material, negative plate, battery preparation method and battery
CN114447271A (en) * 2021-12-30 2022-05-06 深圳市贝特瑞新能源技术研究院有限公司 Preparation method of electrode plate, electrode plate and lithium ion battery
CN114628634A (en) * 2022-04-11 2022-06-14 蜂巢能源科技(无锡)有限公司 Positive plate, preparation method and all-solid-state battery
CN114927688A (en) * 2022-04-20 2022-08-19 重庆市紫建新能源有限公司 Negative pole piece containing composite binder and preparation method thereof
CN114975860A (en) * 2022-06-28 2022-08-30 重庆冠宇电池有限公司 Negative plate and battery
CN115000407A (en) * 2022-06-13 2022-09-02 万向一二三股份公司 Silicon-based negative electrode plate and preparation method and application thereof
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EP4064383A1 (en) * 2021-03-25 2022-09-28 SK Innovation Co., Ltd. Anode for secondary battery and lithium secondary battery including the same
EP4220752A3 (en) * 2021-03-25 2023-08-09 SK On Co., Ltd. Anode for secondary battery and lithium secondary battery including the same
CN113346043A (en) * 2021-06-04 2021-09-03 江西安驰新能源科技有限公司 Low-temperature lithium ion battery positive pole piece and preparation method thereof, and lithium ion battery
CN113991063A (en) * 2021-10-08 2022-01-28 苏州清陶新能源科技有限公司 Preparation method of battery cathode and lithium battery
CN114005958A (en) * 2021-10-15 2022-02-01 珠海冠宇电池股份有限公司 Silicon-carbon composite structure's negative pole piece reaches battery including this negative pole piece
WO2023082039A1 (en) * 2021-11-09 2023-05-19 宁德时代新能源科技股份有限公司 Negative electrode sheet, secondary battery, battery module, battery pack, and electric device
CN114050234A (en) * 2021-11-15 2022-02-15 珠海冠宇电池股份有限公司 Negative plate and lithium ion battery comprising same
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CN114335521A (en) * 2021-11-22 2022-04-12 惠州市豪鹏科技有限公司 Negative plate material, negative plate, battery preparation method and battery
CN114068867A (en) * 2021-11-24 2022-02-18 蜂巢能源科技有限公司 Lithium-supplementing negative plate and lithium ion battery
CN114447271A (en) * 2021-12-30 2022-05-06 深圳市贝特瑞新能源技术研究院有限公司 Preparation method of electrode plate, electrode plate and lithium ion battery
CN114447271B (en) * 2021-12-30 2024-04-26 深圳市贝特瑞新能源技术研究院有限公司 Electrode slice preparation method, electrode slice and lithium ion battery
WO2023151667A1 (en) * 2022-02-10 2023-08-17 珠海冠宇电池股份有限公司 Negative electrode pole and lithium ion battery
CN114628634A (en) * 2022-04-11 2022-06-14 蜂巢能源科技(无锡)有限公司 Positive plate, preparation method and all-solid-state battery
CN114628634B (en) * 2022-04-11 2023-09-15 蜂巢能源科技(无锡)有限公司 Positive plate, preparation method and all-solid-state battery
CN114927688A (en) * 2022-04-20 2022-08-19 重庆市紫建新能源有限公司 Negative pole piece containing composite binder and preparation method thereof
CN115000407A (en) * 2022-06-13 2022-09-02 万向一二三股份公司 Silicon-based negative electrode plate and preparation method and application thereof
CN114975860A (en) * 2022-06-28 2022-08-30 重庆冠宇电池有限公司 Negative plate and battery
CN115911511A (en) * 2022-12-13 2023-04-04 江苏正力新能电池技术有限公司 Lithium ion battery
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