Electrode plate, electrochemical device and electronic device

Abstract

The invention discloses an electrode plate, an electrochemical device and an electronic device. The electrode pole piece comprises a current collector and an active substance coating located on the current collector, the active substance coating comprises an insulating layer, the insulating layer is located at the edge of the current collector, and the insulating layer comprises an adhesive; the adhesive is one or more of an ethylene-acrylic acid copolymer, an ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate, ethylene-butyl acrylate and an ethylene-methacrylic acid copolymer. The electrode plate is coated with the insulating layer, and the insulating layer comprises the adhesive, so that the electrode plate can be directly connected with the diaphragm in the battery in an adhesive manner, and an adhesive coating does not need to be arranged on the diaphragm, so that the thickness of the battery in the stacking direction of the positive electrode plate, the diaphragm and the negative electrode plate is reduced, the volume energy density of a battery cell is improved, and the production cost is reduced.

Description

Technical Field

[0001] The present invention specifically relates to an electrode tab, an electrochemical device, and an electronic device. Background Art

[0002] Lithium-ion batteries are widely used in the 3C consumer market and the new energy vehicle field due to their high energy density, high output voltage, long service life, no memory effect, and environmental friendliness. A lithium-ion battery mainly consists of a positive electrode tab, a negative electrode tab, a separator, and an electrolyte.

[0003] In a lithium-ion battery, there is a stacked structure of positive electrode tab - separator - negative electrode tab. In order to accurately position the positive electrode tab and the negative electrode tab during the stacking process, a bonding coating is usually provided on the separator to improve the stability of the stacked structure. However, setting a bonding coating on the separator will reduce the energy density of the battery.

[0004] Therefore, in the design process of lithium-ion batteries, how to improve the volumetric energy density of the battery cell while ensuring the stability of the tab structure and battery performance is an urgent problem to be solved currently. Summary of the Invention

[0005] The technical problem to be solved by the invention is to overcome the defects in the prior art that the bonding coating on the separator of a lithium-ion battery results in high production cost and low volumetric energy density of the battery cell, and to provide an electrode tab, an electrochemical device, and an electronic device. An insulating layer is coated on the electrode tab of the present invention, and the insulating layer includes an adhesive, so that it can be directly adhesively connected to the separator in the battery, without the need to provide a bonding coating on the separator, thereby reducing the thickness of the battery in the stacking direction of the positive electrode tab - separator - negative electrode tab, improving the volumetric energy density of the battery cell, and reducing the production cost.

[0006] In a first aspect, the present invention provides an electrode tab, which includes a current collector and an active material coating located on the current collector. The active material coating includes an insulating layer, the insulating layer is located at the edge of the current collector, and the insulating layer includes an adhesive;

[0007] Wherein, the adhesive is one or more of ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate, ethylene-butyl acrylate, and ethylene-methacrylic acid copolymer.

[0008] In a second aspect, the present invention provides an electrochemical device, which includes the electrode tab and a separator as described above, and the insulating layer on the electrode tab is adhesively connected to the separator. Optionally, the electrochemical device is a lithium-ion secondary battery.

[0009] In a third aspect, the present invention provides an electronic device, which includes the electrochemical device as described above.

[0010] The positive and progressive effects of the present invention are as follows:

[0011] By coating an insulating layer on the electrode plate, the insulating layer includes an adhesive, and thus can be directly adhesively connected to the separator in the battery, without the need to provide an additional bonding coating on the separator, so as to reduce the thickness of the battery in the stacking direction of the positive electrode plate-separator-negative electrode plate, improve the volumetric energy density of the battery cell and reduce the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is the front view of the electrode plate prepared in the embodiment of the present invention in the direction of the width of the electrode plate.

[0013] Figure 2 It is the front view of the electrochemical device prepared in the embodiment of the present invention in the direction of the width of the electrode plate.

[0014] REFERENCE NUMERALS

[0015] Insulating layer 1

[0016] Active material layer 2

[0017] Current collector 3

[0018] Separator 4 DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples. The experimental methods without specific conditions in the following examples are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0020] Electrode plate

[0021] The electrode plate described in the first aspect of the present invention includes a current collector and an active material coating located on the current collector, the active material coating includes an insulating layer, the insulating layer is located at the edge of the current collector, and the insulating layer includes an adhesive;

[0022] Wherein, the adhesive is one or more of ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate, ethylene-butyl acrylate and ethylene-methacrylic acid copolymer.

[0023] In the embodiment of the present invention, the electrode plate includes a tab, and the tab protrudes from one side of the current collector.

[0024] In some embodiments, the insulating layer may cover the edge of the current collector (except for the tab part); in other embodiments, the insulating layer may extend from the current collector to the tab and cover the connection between the current collector and the tab (i.e., the insulating layer covers the root of the tab).

[0025] In the embodiment of the present invention, the insulating layer is close to the tab side, and the active material layer is away from the tab side.

[0026] In some embodiments, when tabs are provided on opposite sides of the electrode tab, the insulating layer may be provided at the edge of the current collector on the side where one tab is located (i.e., the single-sided edge of the current collector), or the insulating layer may be provided on both sides (i.e., the double-sided edge of the current collector).

[0027] In the present invention, according to the convention in the art, the tab is generally provided at the edge position in the length extension direction of the current collector.

[0028] In the present invention, the electrode tab can be a positive electrode tab or a negative electrode tab.

[0029] In the embodiment of the present invention, the adhesive preferably includes one or more of ethylene-acrylic copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate, and ethylene-butyl acrylate.

[0030] In the embodiment of the present invention, when the adhesive includes one or more of ethylene-acrylic copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate, and ethylene-butyl acrylate, not only the volume energy density of the battery cell is improved, but also the peel strength between the electrode tab and the separator is relatively high.

[0031] In the embodiment of the present invention, the initial melting point of the adhesive is preferably 80-105 °C, such as 86 °C, 90 °C, or 105 °C, and more preferably 80-95 °C.

[0032] Among them, the initial melting point generally refers to drying the sample (adhesive) in an oven at 60 °C, measuring it with a differential scanning calorimeter (DSC), and raising the temperature of the sample from room temperature to 250 °C at a heating rate of 10 °C / min. The initial peak point of the sample is the initial melting point.

[0033] In the embodiment of the present invention, when the initial melting point of the adhesive is 80-105 °C, not only the volume energy density of the battery cell is improved, but also the peel strength between the electrode tab and the separator is relatively high; when the initial melting point of the adhesive is 80-95 °C, the peel strength between the electrode tab and the separator is even higher.

[0034] The test conditions for the initial melting point of the adhesive are generally as follows: drying the sample (adhesive) in an oven at 60 °C, measuring it with a differential scanning calorimeter (DSC), and raising the temperature of the sample from room temperature to 250 °C at a heating rate of 10 °C / min. The initial peak point of the sample is the initial melting point.

[0035] It should be noted that the battery will heat up during use. If the "initial melting point" is lower than 80°C, the adhesive will melt during battery use, which is not conducive to the connection stability between the separator and the positive and negative electrode plates. During the preparation of the insulating layer, if the "initial melting point" is higher than 105°C, it is not conducive to battery production.

[0036] In an embodiment of the present invention, the weight-average molecular weight of the adhesive is preferably 10,000 to 1,000,000 g / mol, more preferably 50,000 to 1,000,000 g / mol.

[0037] In an embodiment of the present invention, the molecular weight of the ethylene-acrylic acid copolymer is preferably 50,000 to 1,000,000 g / mol.

[0038] In an embodiment of the present invention, the molecular weight of the ethylene-vinyl acetate copolymer is preferably 50,000 to 1,000,000 g / mol.

[0039] In an embodiment of the present invention, the molecular weight of the ethylene-ethyl acrylate is preferably 50,000 to 1,000,000 g / mol.

[0040] In an embodiment of the present invention, the molecular weight of the ethylene-butyl acrylate is preferably 50,000 to 1,000,000 g / mol.

[0041] In an embodiment of the present invention, the substitution degree of the polar side chain of the adhesive is preferably 5% to 40%. The substitution degree of the polar side chain of the adhesive refers to the ratio of the molecular weight of the polar functional group in the adhesive to the total molecular weight of the adhesive. The polar functional group can be conventional in the art, generally referring to polar functional groups containing oxygen and / or nitrogen, such as carboxyl, hydroxyl or amide groups. The test method for the substitution degree of the polar side chain of the adhesive can be the conventional technology in the art. For example, the content of oxygen and nitrogen is measured using an energy dispersive X-ray spectrometer (EDS), or the functional group is measured using an infrared spectrometer, and the substitution degree is calculated by dividing the molecular weight of the polar functional group by the total molecular weight.

[0042] In an embodiment of the present invention, the substitution degree of the ethylene-acrylic acid copolymer is preferably 5-35%.

[0043] In an embodiment of the present invention, the substitution degree of the ethylene-vinyl acetate copolymer is preferably 7-40%.

[0044] In an embodiment of the present invention, the substitution degree of the ethylene-ethyl acrylate is preferably 7-40%.

[0045] In an embodiment of the present invention, the substitution degree of the ethylene-butyl acrylate is preferably 10-40%.

[0046] In the embodiments of the present invention, the various adhesives, such as ethylene-butyl acrylate, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate, etc., can be adhesives prepared according to actual performance requirements, and their preparation processes are prior art and will not be elaborated here; or they can be materials purchased from the market, such as ethylene-butyl acrylate with the model number 33331 sold by ExxonMobil, ethylene-acrylic acid copolymer with the model number 3440 sold by Dow Chemical, ethylene-vinyl acetate copolymer with the model number S45075 sold by Shanghai Yuanye, ethylene-ethyl acrylate with the model number 30707 sold by DuPont, etc.

[0047] In the embodiments of the present invention, the active material coating further includes an active material layer, and the insulating layer and the active material layer are arranged side by side.

[0048] In a specific embodiment of the present invention, along the width direction of the current collector, the insulating layer and the active material layer are arranged side by side.

[0049] Wherein, the width direction of the current collector refers to the direction perpendicular to the length extension direction of the current collector where the tab is located.

[0050] In the present invention, the side-by-side arrangement includes various situations such as there being a gap between the insulating layer and the active material layer, partial overlap at the adjacent part of the insulating layer and the active material layer, and no overlap and complete connection between the insulating layer and the active material layer. All kinds of setting schemes of the insulating layer and the active material layer are within the protection scope of the technical solution of the present invention. The insulating layer covers the edge of the surface of the current collector to improve the safety of the electrode sheet.

[0051] Wherein, the ratio of the thickness of the insulating layer to the thickness of the active material layer is preferably 0.85 ≤ H1 / H2 ≤ 1, such as 0.85, 0.9 or 0.99, and more preferably 0.9 ≤ H1 / H2 < 1, where H1 is the thickness of the insulating layer in the direction perpendicular to the current collector, and H2 is the thickness of the active material layer in the direction perpendicular to the current collector. Both H1 and H2 are the thicknesses after rolling, and the pressure of the rolling can be 30 - 50 tons.

[0052] In the embodiments of the present invention, when the ratio of the thickness of the insulating layer to the thickness of the active material layer is 0.85 ≤ H1 / H2 ≤ 1, not only the volume energy density of the battery cell is improved, but also the peel force between the electrode sheet and the separator is relatively high; when the ratio of the thickness of the insulating layer to the thickness of the active material layer is 0.9 ≤ H1 / H2 < 1, the peel force between the electrode sheet and the separator is even higher.

[0053] Wherein, the difference in thickness between the active material layer and the insulating layer is 0 ≤ H2 - H1 < 15 μm, where H1 is the thickness of the insulating layer in the direction perpendicular to the current collector, and H2 is the thickness of the active material layer in the direction perpendicular to the current collector.

[0054] In the embodiment of the present invention, the width W of the insulating layer is preferably 1.5 mm ≤ W ≤ 10 mm, such as 3 mm, 5 mm or 10 mm, more preferably 2 mm ≤ W ≤ 6 mm, and W is the width of the insulating layer in the width direction parallel to the current collector.

[0055] In the embodiment of the present invention, when the width W of the insulating layer is 1.5 mm ≤ W ≤ 10 mm, not only the volumetric energy density of the battery cell is improved, but also the peeling force between the electrode sheet and the separator is relatively high; when the width W is 2 mm ≤ W ≤ 6 mm, not only the peeling force between the electrode sheet and the separator is relatively high, but also the volumetric energy density of the battery cell is higher. When the width is relatively large, since the proportion of the active material layer is relatively less, the volumetric energy density of the battery cell is reduced; when the width is relatively small, since the proportion of the insulating layer is relatively less, the peeling force between the electrode sheet and the separator is reduced.

[0056] In the embodiment of the present invention, the insulating layer further includes a ceramic material.

[0057] Among them, the ceramic material can be conventional in the art, such as alumina ceramic, boehmite ceramic, etc.

[0058] Among them, in the insulating layer, the weight percentage of the ceramic material is preferably 65 wt% - 85 wt%.

[0059] In the embodiment of the present invention, in the insulating layer, the weight percentage of the adhesive is preferably 15 wt% - 35 wt%.

[0060] In the present invention, the insulating layer is applicable to both the positive electrode sheet and the negative electrode sheet.

[0061] In the present invention, when the electrode sheet is a positive electrode sheet, the active material layer is prepared by coating a positive electrode active material including a positive electrode active material on a positive electrode current collector, and according to needs, a conductive agent, a binder, a solvent and a thickener can be further added.

[0062] Among them, the positive electrode active material can be a conventional positive electrode active material of a lithium ion battery in the art or a conventional positive electrode active material of a sodium ion battery in the art. The positive electrode active material of the lithium ion battery can be a lithium ion material such as a ternary material, lithium cobaltate, lithium iron phosphate, lithium manganate, etc., such as nickel cobalt manganese ternary material (NCM811), which is not limited herein.

[0063] For the conductive agent in the positive active material, it can be a conductive agent conventionally used in the positive electrode in the art. For example, specifically, it can use: graphite, such as natural graphite or artificial graphite; carbon-based materials, such as conductive carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal carbon black and carbon fiber; metal powder or metal fiber, such as copper, nickel, aluminum and silver; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium dioxide; or conductive polymers, such as polyphenylene derivatives, etc. Preferably, the conductive agent is one or more of conductive carbon black, carbon nanotubes and graphene, and more preferably conductive carbon black.

[0064] For the binder in the positive active material, it can be a binder conventionally used in the positive electrode in the art. For example, it can include polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber or various copolymers thereof, and any one or a mixture of two or more thereof can be used.

[0065] For the solvent in the positive active material, it can be a solvent conventionally used in the positive electrode in the art, such as N-methylpyrrolidone (NMP).

[0066] In the embodiments of the present invention, there is no particular limitation on the thickener for the positive electrode. The addition of the thickener can increase the system viscosity of each component in the positive active material layer. Generally, sodium carboxymethyl cellulose (CMC) solution can be selected.

[0067] In a specific embodiment of the present invention, the active material layer of the positive electrode plate includes: NCM811, conductive carbon black and polyvinylidene fluoride (PVDF).

[0068] In some specific embodiments of the present invention, the mass ratio of NCM811, conductive agent and binder in the active material layer of the negative electrode plate can be (90-100):(1-2):(1-2), for example, 96.5:1.5:2.

[0069] For the positive current collector, it can be a current collector conventionally used for the positive electrode in the art, and can be a common current collector or a composite current collector. The positive current collector can use, without limitation, a material that does not cause chemical changes and has high electrical conductivity according to the actual needs of the electrochemical device. For example, stainless steel, aluminum, nickel, titanium, or calcined carbon can usually be used, or aluminum or stainless steel materials surface-treated with carbon, nickel, titanium, silver, etc. To enhance the adhesion of the positive electrode active material, micro-embossing can be formed on the surface of the positive current collector. The positive current collector can be used in various forms, such as a film, sheet, foil, mesh, or porous body.

[0070] Among them, the thickness of the positive current collector is, for example, 13 μm or 16 μm.

[0071] In the present invention, the positive electrode sheet can be prepared by a conventional method in the art. For example, the following method can be adopted: NCM811, a conductive agent, and a binder are mixed in a certain weight ratio, and then a solvent is added and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on the positive current collector; and then through processes such as drying, cold pressing, and slitting, the positive electrode sheet is prepared.

[0072] In the present invention, when the electrode sheet is a negative electrode sheet, the active material layer is prepared by coating a negative electrode active material including a negative electrode active material on the negative current collector, and according to needs, a conductive agent, a binder, and a thickening agent can be further added.

[0073] Among them, the negative electrode active material can be a carbon-based material, a silicon-based material, a tin-based material, etc., and will not be limited herein.

[0074] For the conductive agent in the negative electrode active material, it can be a conductive agent conventionally used for the negative electrode in the art. For example, specifically, graphite such as natural graphite or artificial graphite can be used; carbon-based materials such as conductive carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal carbon black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides such as titanium dioxide; or conductive polymers such as polyphenylene derivatives, etc. Preferably, the conductive agent is one or more of conductive carbon black, carbon nanotubes, and graphene, and more preferably conductive carbon black.

[0075] For the binder in the negative electrode active material, it can be a binder conventionally used in the negative electrode in the art. For example, the following materials can be used as the binder: polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), polyvinylidene fluoride - hexafluoropropylene copolymer (PVDF - co - HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene - propylene - diene monomer (EPDM), sulfonated EPDM, styrene - butadiene rubber (SBR), fluororubber or various copolymers thereof, and any one of them or a mixture of two or more of them can be used.

[0076] In the embodiments of the present invention, the thickener is not particularly limited. The addition of the thickener can increase the system viscosity of each component in the negative electrode active material layer. Generally, sodium carboxymethyl cellulose (CMC) solution can be selected.

[0077] In a specific embodiment of the present invention, the active material layer of the negative electrode plate includes: artificial graphite, conductive carbon black, sodium carboxymethyl cellulose, and styrene - butadiene rubber (SBR).

[0078] In some specific embodiments of the present invention, the mass ratio of artificial graphite, conductive agent, thickener, and binder in the active material layer of the negative electrode plate can be (90 - 100):1:(1 - 1.5):(1 - 2), for example, 96.4:1:1.2:1.4.

[0079] In the present invention, the negative electrode current collector can be a current collector conventionally used in the negative electrode in the art, and can be a common current collector or a composite current collector. The current collector can be used without limitation according to the actual needs of the electrochemical device with a material that does not cause chemical changes and has conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum - cadmium alloy can be used, or copper, stainless steel material, or aluminum - cadmium alloy surface - treated with carbon, nickel, titanium, or silver. In addition, in order to enhance the adhesion of the negative electrode active material, micro - embossing can be formed on the surface of the negative electrode current collector. The negative electrode current collector can be used in various forms, such as film, sheet, foil, mesh, or porous body, etc.

[0080] Among them, the thickness of the negative electrode current collector is, for example, 6 μm.

[0081] In the present invention, the negative electrode plate can be prepared by a conventional method in the art. For example, the following method can be adopted: amorphous carbon, conductive agent, thickener, and binder are mixed in a certain weight ratio, and then a solvent is added and mixed evenly to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on the current collector; and then through processes such as drying, cold pressing, and slitting, the negative electrode plate is prepared.

[0082] Electrochemical device

[0083] The electrochemical device described in the second aspect of the present invention includes the electrode tab and the separator as described above, and the insulating layer on the electrode tab is adhesively connected to the separator. Optionally, the electrochemical device is a lithium-ion secondary battery.

[0084] In the present invention, through the adhesive in the insulating layer, the insulating layer and the separator are directly adhered, so that the electrode tab and the separator are tightly connected, thereby improving the energy density of the lithium-ion battery.

[0085] In some embodiments, the electrolyte can be a conventional electrolyte for lithium-ion secondary batteries in the art, generally including a non-aqueous solvent and a lithium salt.

[0086] Among them, the non-aqueous solvent can be a conventional non-aqueous solvent in the art, preferably an ester solvent, more preferably a carbonate solvent. The carbonate solvent can be selected from one or more of ethylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).

[0087] In the present invention, the electrolyte may further include additives.

[0088] Among them, the additives can be selected from one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene vinylene carbonate (VEC), divinyl sulfite (DTD), vinylene sulfite, 1,3-propane sultone (PS), allyl sulfonic acid lactone, and 1,4-butane sultone.

[0089] Among them, the lithium salt can be a conventional lithium salt in the art, such as LiPF6 and / or LiODFB.

[0090] When the lithium salt includes LiPF6 and LiODFB, the molar ratio of LiPF6 to LiODFB can be (90-97):(3-10), such as 96:4.

[0091] Among them, the concentration of the lithium salt can be conventional in the art, generally 1-2 mol / L.

[0092] In some embodiments of the present invention, the electrolyte includes EPC, EMC, EC, PC, and FEC. The volume ratio of PEC, EMC, EC, PC, and FEC can be (30-50):(10-30):(15-35):(1-10):(1-15), such as 40:20:25:5:10.

[0093] In a specific embodiment of the present invention, the concentration of the electrolyte is 1 mol / L.

[0094] In the present invention, the preparation method of the electrolyte can be conventional in the art, generally by mixing the non-aqueous solvent and the lithium salt, for example, adding the lithium salt to the non-aqueous solvent.

[0095] In some embodiments, the separator can be a polypropylene separator or a polyethylene separator.

[0096] Among them, the thickness of the separator can be 9 - 18 μm, for example, 11 μm.

[0097] Among them, the gas permeability of the separator can be 180 - 380 s / 100 mL.

[0098] Among them, the porosity of the separator can be 30% - 50%.

[0099] In the present invention, the preparation method of the lithium-ion battery can be a conventional preparation method in the art. It can be winding the positive electrode sheet, the negative electrode sheet and the separator to obtain an electrode core, and then performing packaging with a packaging shell and injecting the electrolyte; or stacking the positive electrode sheet, the separator and the negative electrode sheet in sequence to obtain an electrode core, and then performing packaging with a packaging shell and injecting the electrolyte.

[0100] Electronic device

[0101] The electronic device described in the third aspect of the present invention includes the electrochemical device as described above.

[0102] In the present invention, the electronic device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, a video recorder, a portable printer / copier, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, a backup power supply, etc.

[0103] Examples and Comparative Examples

[0104] In the following examples and comparative examples, the sources of the adhesives used are shown in Table 1. The separator was purchased from Shenzhen Xingyuan Materials Technology Co., Ltd., with the model SH311J22A.

[0105] Table 1

[0106]

[0107]

[0108] Preparation of Lithium-Ion Secondary Battery

[0109] It should be noted that in a lithium-ion battery, there is a stacked structure of a positive electrode sheet - separator - negative electrode sheet. In the conventional design process of a lithium-ion battery, a bonding coating is generally provided between the positive electrode sheet and the separator, and between the negative electrode sheet and the separator to improve the stability of the stacked structure. In Table 2 below, "yes" for the positive electrode separator bonding coating means that a bonding coating is provided between the positive electrode sheet and the separator, and "no" for the positive electrode separator bonding coating means that no bonding coating is provided between the positive electrode sheet and the separator; "yes" for the negative electrode separator bonding coating means that a bonding coating is provided between the negative electrode sheet and the separator, and "no" for the negative electrode separator bonding coating means that no bonding coating is provided between the negative electrode sheet and the separator.

[0110] In the examples and comparative examples of the present invention, the bonding coating used between the electrode sheet and the separator is the electrode binder PVDF purchased from Arkema LBG in France, with a single-sided thickness of 2 μm.

[0111] Example A1

[0112] (1) Preparation of the positive electrode sheet:

[0113] Weigh and mix the adhesive EAA, ceramic, and N-methylpyrrolidone according to the effective weight ratio of 20:80:138. First, mix the adhesive with the solvent and disperse it at a high speed of 1500 rpm / min for 1 h. Then add the ceramic particles and disperse them at a speed of 2000 rpm / min for 90 min to obtain the insulating layer coating.

[0114] Mix NCM811, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) in a weight ratio of 96.5:1.5:2 (the mass of NCM811 is 200 kg), add the solvent N-methylpyrrolidone (NMP), and stir and mix well to obtain the positive electrode active material layer slurry. Coat the positive electrode active material layer slurry on a positive electrode current collector aluminum foil with a thickness of 13 μm, and perform processes such as drying, cold pressing, and slitting to obtain the active material layer. Coat the above-prepared insulating layer coating on both sides of the active material layer. The positive electrode sheet is prepared.

[0115] (2) Preparation of the negative electrode sheet

[0116] Weigh and mix the adhesive SBR, ceramic, and water according to the effective weight ratio of 20:80:138. First, mix the adhesive with the solvent and disperse it at a high speed of 1500 rpm / min for 1 h. Then add the ceramic particles and disperse them at a speed of 2000 rpm / min for 90 min to obtain the insulating layer coating.

[0117] Mix artificial graphite, conductive agent acetylene black, thickening agent CMC, and binder SBR in a mass ratio of 96.4:1:1.2:1.4 (the mass of artificial graphite is 201 kg), add solvent deionized water, and stir well to obtain the negative electrode slurry; evenly coat the negative electrode slurry on a negative electrode current collector copper foil with a thickness of 6 μm, and obtain the active material layer through processes such as drying, cold pressing, and slitting; coat the prepared insulating layer coating on both sides of the active material layer; prepare the negative electrode plate.

[0118] (3) Preparation of electrolyte

[0119] Mix epichlorohydrin (EPC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and fluoroethylene carbonate (FEC) in a volume ratio of 40:20:25:5:10 to obtain an organic solvent, and then dissolve the fully dried lithium salts (LiPF6 and LiODFB with a molar ratio of 96:4) in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0120] (4) Separator

[0121] Use a porous membrane of PE with a thickness of 11 μm as the separator, the base film is 7 μm, 2 μm of ceramic on both sides, and the porosity is 40%; the air permeability value is 200 s / 100 mL.

[0122] (5) Preparation of lithium-ion secondary battery

[0123] Stack the prepared positive electrode plate, separator, and negative electrode plate in sequence, with the separator in the middle of the positive and negative electrode plates to play an isolation role. Then wrap it with an aluminum-plastic film, inject the above-prepared electrolyte after drying, and finally prepare a soft-pack battery (i.e., a lithium-ion secondary battery) with a capacity of 1 Ah through processes such as encapsulation, standing, and formation; cancel the adhesive coating between the positive electrode plate and the separator, and retain the adhesive coating between the negative electrode plate and the separator;

[0124] In Example A1, the type of adhesive, the thickness ratio (H1 / H2) of the insulating layer to the active material layer, and the width of the insulating layer are shown in Table 2.

[0125] Examples A2 - D3

[0126] Except for using the type of adhesive, the thickness ratio (H1 / H2) of the insulating layer to the active material layer, and the width of the insulating layer listed in Table 2, the rest of the operations and conditions are the same as those in Example A1.

[0127] Example E1

[0128] Except for canceling the bonding coatings between the positive electrode sheet and the separator, canceling the bonding coatings between the negative electrode sheet and the separator, using the types of adhesives listed in Table 2, the thickness ratio (H1 / H2) of the insulating layer to the active material layer, the width of the insulating layer, and using the following preparation methods for the positive electrode sheet and the negative electrode sheet, the remaining operations and conditions are the same as those in Example A1.

[0129] (1) Preparation of the positive electrode sheet:

[0130] Weigh and mix the adhesive EAA, ceramic, and N-methylpyrrolidone according to the effective weight ratio of 20:80:138. First, mix the adhesive with the solvent and disperse it at a high speed of 1500 rpm / min for 1 h. Then add the ceramic particles and disperse them at a speed of 2000 rpm / min for 90 min to obtain the insulating layer coating;

[0131] Mix NCM811, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) according to the weight ratio of 96.5:1.5:2, add the solvent N-methylpyrrolidone (NMP), and stir and mix well to obtain the positive electrode active material layer slurry; coat the positive electrode active material layer slurry on the positive electrode current collector aluminum foil, and perform processes such as drying, cold pressing, and slitting to obtain the active material layer; coat the above-prepared insulating layer coating on both sides of the active material layer; prepare the positive electrode sheet.

[0132] (2) Preparation of the negative electrode sheet

[0133] Weigh and mix the adhesive EAA, ceramic, and water according to the effective weight ratio of 20:80:138. First, mix the adhesive with the solvent and disperse it at a high speed of 1500 rpm / min for 1 h. Then add the ceramic particles and disperse them at a speed of 2000 rpm / min for 90 min to obtain the insulating layer coating;

[0134] Mix artificial graphite, conductive agent acetylene black, thickening agent CMC, and binder SBR according to the mass ratio of 96.4:1:1.2:1.4, then add the solvent deionized water, and stir and mix well to obtain the negative electrode active material layer slurry; uniformly coat the negative electrode active material layer slurry on the negative electrode current collector copper foil, and perform processes such as drying, cold pressing, and slitting to obtain the active material layer; coat the above-prepared insulating layer coating on both sides of the active material layer; prepare the negative electrode sheet;

[0135] In Example E1, the width and thickness of the insulating layer in the positive electrode sheet are the same as those of the insulating layer in the negative electrode sheet.

[0136] Example E2

[0137] Except for using the types of adhesives listed in Table 2, the thickness ratio of the insulating layer to the active material layer (H1 / H2), and the width of the insulating layer, the remaining operations and conditions are the same as those in Example E1.

[0138] Comparative Example 1

[0139] Except for retaining the adhesive coating between the positive electrode plate and the separator, retaining the adhesive coating between the negative electrode plate and the separator, and using the types of adhesives listed in Table 2, the thickness ratio of the insulating layer to the active material layer (H1 / H2), and the width of the insulating layer, the remaining operations and conditions are the same as those in Example A1.

[0140] Comparative Example 2

[0141] Except for canceling the adhesive coating between the positive electrode plate and the separator, canceling the adhesive coating between the negative electrode plate and the separator, and using the types of adhesives listed in Table 2, the thickness ratio of the insulating layer to the active material layer (H1 / H2), and the width of the insulating layer, the remaining operations and conditions are the same as those in Example A1.

[0142] Comparative Example 3

[0143] Except for canceling the adhesive coating between the positive electrode plate and the separator, canceling the adhesive coating between the negative electrode plate and the separator, using the types of adhesives listed in Table 2, the thickness ratio of the insulating layer to the active material layer (H1 / H2), the width of the insulating layer, and using the following preparation methods for the positive electrode plate and the negative electrode plate, the remaining operations and conditions are the same as those in Example A1.

[0144] (1) Preparation of the positive electrode plate:

[0145] Weigh and mix the adhesive PVDF, ceramic, and N-methylpyrrolidone according to the effective weight ratio of 20:80:138. First, mix the adhesive with the solvent and disperse it at a high speed of 1500 rpm / min for 1 h. Then add ceramic particles and disperse them at a speed of 2000 rpm / min for 90 min to obtain the insulating layer coating.

[0146] Mix NCM811, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) in a weight ratio of 96.5:1.5:2, add the solvent N-methylpyrrolidone (NMP), and stir and mix well to obtain the positive active material layer slurry. Coat the positive active material layer slurry on the positive current collector aluminum foil, and perform processes such as drying, cold pressing, and slitting to obtain the active material layer. Coat the above-prepared insulating layer coating on both sides of the active material layer. The positive electrode plate is prepared.

[0147] (2) Preparation of the negative electrode plate

[0148] Weigh and mix the adhesive SBR, ceramic, and water according to the effective weight ratio of 20:80:138. First, mix the adhesive with the solvent and disperse it at a high speed of 1500 rpm for 1 hour. Then add the ceramic particles and disperse them at a speed of 2000 rpm for 90 minutes to obtain the insulating layer coating.

[0149] Mix artificial graphite, conductive agent acetylene black, thickening agent CMC, and binder SBR in a mass ratio of 96.4:1:1.2:1.4, then add deionized water as the solvent and stir well to obtain the slurry for the negative active material layer. Uniformly coat the slurry of the negative active material layer on the negative current collector copper foil, and perform processes such as drying, cold pressing, and slitting to obtain the active material layer. Coat the prepared insulating layer coating on both sides of the active material layer. The negative electrode plate is prepared.

[0150] Comparative Example 4

[0151] Except for using the types of adhesives listed in Table 2, the thickness ratio (H1 / H2) of the insulating layer to the active material layer, the width of the insulating layer, and using the following preparation methods for the positive electrode plate and the negative electrode plate, the rest of the operations and conditions are the same as those in Comparative Example 3.

[0152] Table 2

[0153]

[0154]

[0155] Note: In Examples A1 - E2 and Comparative Examples 1 - 4, the thickness of the positive active material layer is 85 μm; the thickness of the negative active material layer is 80 μm; in Comparative Examples 1 - 2 and Examples A1 - D3, the adhesive used for the insulating layer of the negative electrode plate is SBR, the thickness ratio of the insulating layer to the active material layer of the negative electrode plate is 0.9, and the width of the insulating layer of the negative electrode plate is 3 mm; in Comparative Examples 3 - 4, the adhesive used for the insulating layer of the positive electrode plate is PVDF, the thickness ratio of the insulating layer to the active material layer of the positive electrode plate is 0.9, and the width of the insulating layer of the positive electrode plate is 3 mm.

[0156] In addition, it is worth noting that in each of the above examples, commercially available binders such as EVA and EAA are used as examples of the binders for the insulating layer. In actual use, self - made or modified EVA, EAA, etc. binders can also be used, and the source of the binder does not limit the protection scope of the invention application.

[0157] Effect Example

[0158] (1) Structure diagram of the electrode plate

[0159] Figure 1The front view of the electrode sheet prepared in the embodiment of the present invention in the direction of the electrode sheet width. Figure 2 The front view of the electrochemical device prepared in the embodiment of the present invention in the direction of the electrode sheet width. The insulating layer 1 and the active material layer 2 are located on the current collector 3. Along the width direction of the current collector 3, the insulating layer 1, the active material layer 2, and the insulating layer 1 are arranged in parallel. The separator 4 is located above the insulating layer 1 and the active material layer 2.

[0160] (2) Peel force test

[0161] Coat the insulating slurry on the aluminum foil. After drying, hot press the electrode sheet and the separator at 100 °C and 8T for 1 min. Cut the hot-pressed sample into a strip with a size of 15 mm * 200 mm. Use a Vantage tensile machine, test rate: 10 mm / min; gauge length: 50 mm; perform 180° peeling to obtain the peeling strength of the coating.

[0162] Peel force (N) = (measured peel force / 15) * width of the insulating layer.

[0163] (3) Energy density test

[0164] Take a fixed-size soft-pack battery cell with length, width, and height of 15 cm: 12 cm: 1.5 cm (the electrode sheet length and width are 15 cm and 12 cm) as an example:

[0165] For the battery cell prepared above, under the condition of constant temperature at 25 °C, first discharge it at a constant current of 0.33C rate to 2.8V. Charge it at a constant current and constant voltage of 0.5C rate CC to 4.25V (the constant voltage cut-off current is 0.02C), and finally discharge it at a constant current of 0.33C rate to 2.8V. This is the discharge capacity of the battery cell. The ratio of the 0.33C discharge energy to the volume of the battery cell is the volume energy density.

[0166] (4) Cycle performance test

[0167] For the above-mentioned lithium-ion secondary battery to be tested, in a constant temperature environment at 25 °C, charge it at a constant current and constant voltage of 0.33C rate to 4.2V (the constant voltage cut-off current is 0.05C), and then discharge it at a constant current of 0.33C rate to 2.8V. Cycle 3 times with this charge-discharge regime, and record the last discharge capacity as the 0.33C capacity. Charge it at a constant current and constant voltage of 0.33C rate to 4.2V (the constant voltage cut-off current is 0.05C), and then discharge it at a constant current of 2C rate to 2.8V. Cycle 3 times with this charge-discharge regime, and record the last discharge capacity as the 2C capacity. Record the ratio of the 2C capacity to the 0.33C capacity as the capacity retention rate.

[0168] The relevant effect data are shown in Table 3.

[0169] Table 3

[0170]

[0171] Note: In Table 3, the improvement of the energy density is compared based on Comparative Example 1.

[0172] According to the results of Examples A1 - E2 and Comparative Example 1, when the insulating layer contains the adhesive defined in the present invention, even if the bonding coating provided between the positive electrode sheet and the separator is cancelled, or the bonding coating provided between the positive electrode sheet and the separator and the bonding coating provided between the negative electrode sheet and the separator are cancelled simultaneously, it is still possible to make the positive electrode sheet or the negative electrode sheet and the separator bond better, the stability of the battery cell is stronger, the battery cell operates stably, and the cycle capacity retention rate is higher.

[0173] In the embodiments of the present invention, through the adhesive in the insulating layer, the insulating layer and the separator are directly bonded, and there is no need to provide a bonding coating on the separator, thereby improving the energy density of the lithium-ion battery and reducing the cost of coating the bonding coating on the separator during the production process.

[0174] According to the results of Example A1 and Comparative Examples 2 - 4, when PVDF (polyvinylidene fluoride), SBR (styrene-butadiene rubber) and PAA (polyacrylic acid) are used as adhesives in the insulating layer, the peel force test shows that the electrode sheet and the separator cannot be bonded together.

[0175] According to the results of Examples A1 - A4 and Examples B1 - B2, when ethylene-acrylic copolymer, ethylene-vinyl acetate copolymer, ethyl acrylate-ethylene or butyl acrylate-ethylene is used as the adhesive, the bonding force of the insulating layer is strong, which can make the positive electrode sheet and the separator bond better, and the cycle capacity retention rate of the battery cell is high, and the stability of the battery cell is strong.

[0176] According to the results of Example A1 and Examples C1 - C3, when the width of the insulating layer is 1.5 mm to 10 mm, the bonding force of the insulating layer is strong, which can make the positive electrode sheet and the separator bond better, and the stability of the battery cell is good.

[0177] According to the results of Example A1 and Examples D1 - D3, when the thickness ratio of the insulating layer to the active material layer is 0.85 ≤ H1 / H2 ≤ 1, the bonding force between the insulating layer and the separator is still strong, which can make the positive electrode sheet and the separator bond better, and the stability of the battery cell is good.

[0178] According to the results of Examples E1 - E2, when the insulating layer is applied to both the positive electrode sheet and the negative electrode sheet at the same time, the effect that the negative electrode sheet and the separator can be bonded better and the stability of the battery cell is good can still be achieved.

[0179] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that this is only an example, and the protection scope of the present invention is defined by the appended claims. Without departing from the principles and essence of the present invention, those skilled in the art can make various changes or modifications to these embodiments, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. An electrode sheet, characterized in that, It includes a current collector and an active material coating located on the current collector. The active material coating includes an insulating layer located at the edge of the current collector, and the insulating layer includes an adhesive. Among them, the adhesive is one or more of ethylene-acrylic copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate, ethylene-butyl acrylate, and ethylene-methacrylic acid copolymer.

2. The electrode sheet according to claim 1, wherein, The initial melting point of the adhesive is 80-105 °C.

3. The electrode sheet according to claim 1, wherein The active material coating further includes an active material layer, and the insulating layer and the active material layer are arranged side by side. Among them, the thickness ratio of the insulating layer to the active material layer is 0.85 ≤ H1 / H2 ≤ 1, where H1 is the thickness of the insulating layer in the direction perpendicular to the current collector, and H2 is the thickness of the active material layer in the direction perpendicular to the current collector. And / or, the thickness difference between the active material layer and the insulating layer is 0 ≤ H2 - H1 < 15 μm, where H1 is the thickness of the insulating layer in the direction perpendicular to the current collector, and H2 is the thickness of the active material layer in the direction perpendicular to the current collector.

4. The electrode sheet according to claim 1, characterized in that, The width W of the insulating layer is 1.5 mm ≤ W ≤ 10 mm, where W is the width of the insulating layer in the direction parallel to the width of the current collector.

5. The electrode sheet according to claim 3, characterized in that, The thickness ratio of the insulating layer to the active material layer is 0.9 ≤ H1 / H2 < 1, where H1 is the thickness of the insulating layer in the direction perpendicular to the current collector, and H2 is the thickness of the active material layer in the direction perpendicular to the current collector. And / or, the width W of the insulating layer is 2 mm ≤ W ≤ 6 mm, where W is the width of the insulating layer in the direction parallel to the width of the current collector.

6. The electrode tab according to claim 1, wherein, The insulating layer further includes a ceramic material. The weight percentage of the ceramic material is 65 wt% - 85 wt%.

7. The electrode tab according to claim 1, wherein, In the insulating layer, the weight percentage of the adhesive is 15 wt% - 35 wt%.

8. The electrode tab according to claim 3, characterized in that, The electrode tab also includes a tab protruding from one side of the current collector; the insulating layer is close to the tab side, and the active material layer is far from the tab side.

9. An electrochemical device, characterized in that, It includes the electrode tab as described in any one of claims 1-8 and a separator, and the insulating layer on the electrode tab is adhesively connected to the separator.

10. An electronic device, characterized in that, It includes the electrochemical device as described in claim 9.

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