Electrode sheet and preparation method and application thereof

Abstract

The present application provides an electrode plate and a preparation method and application thereof. The electrode plate includes a current collector, and one side surface of the current collector includes a tab region and an active material region. The tab region surface is provided with a tab glue layer, and the active material region surface is provided with an active material layer; the tab glue layer includes a phase change material, a binder and an insulating material, and the phase change material includes a polymer phase change material and a non-polymer phase change material. The tab glue layer in the electrode plate can absorb the heat inside the battery, thereby alleviating the problem of a sharp increase in temperature caused by excessive heat generation of the battery. Applying it in a battery can greatly improve the safety performance of the battery.

Description

Technical Field

[0001] The present application relates to the field of secondary batteries, and specifically to electrode plates and preparation methods and applications thereof. Background Art

[0002] With the development of digital terminals such as mobile phones and new energy vehicles, people have put forward higher requirements on the capacity and charging speed of secondary batteries. However, under fast charging conditions, secondary batteries are prone to accumulate a lot of heat during the charging and discharging process, which can cause thermal runaway of the battery cells and even cause the battery to catch fire and explode. In addition, the excessively high temperature inside the battery will also reduce the electrochemical performance and cycle life of the battery. Therefore, it is necessary to control the battery temperature to improve the problem of rapid temperature rise during the charging and discharging process of the secondary battery. Summary of the invention

[0003] In view of this, the present application provides an electrode plate, in which the ear glue layer can absorb the heat inside the battery, thereby alleviating the problem of rapid temperature increase caused by excessive heat generation of the battery. Applying it in the battery can greatly improve the safety performance of the battery.

[0004] In a first aspect, the present application provides an electrode plate, which includes a current collector, and one side surface of the current collector includes a tab region and an active material region, the surface of the tab region is provided with a tab glue layer, and the surface of the active material region is provided with an active material layer; the tab glue layer includes a phase change material, a binder and an insulating material; the phase change material includes a polymer phase change material and a non-polymer phase change material.

[0005] Optionally, in the tab glue layer, the mass ratio of the phase change material, the adhesive and the insulating material is (25-75):(20-50):(0.1-10).

[0006] Optionally, the phase change temperature of the phase change material is 20°C to 75°C.

[0007] Optionally, the phase change temperature of the polymer phase change material is 30°C to 60°C; the phase change temperature of the non-polymer phase change material is 55°C to 70°C.

[0008] Optionally, the mass ratio of the polymer phase change material to the non-polymer phase change material is 1:(0.5-2).

[0009] Optionally, the polymer phase change material includes one or more of polymer polyol, polystyrene, unsaturated polyester, polyurethane, polyphenylene ether, polycarbonate or polyoxymethylene resin and copolymers thereof.

[0010] Optionally, the polymeric polyol includes one or more of polyethylene glycol, polyvinyl alcohol or polypropylene glycol.

[0011] Optionally, the non-polymer phase change material includes one or more of oxides, metal inorganic salts, paraffin, and fatty acids.

[0012] Optionally, the oxide includes one or more of perovskite and vanadium dioxide.

[0013] Optionally, the metal inorganic salt comprises sodium thiosulfate.

[0014] Optionally, the fatty acid comprises one or more of stearic acid or palmitic acid.

[0015] Optionally, the non-polymer phase change material includes perovskite, sodium thiosulfate and fatty acid; the mass ratio of the perovskite, sodium thiosulfate and fatty acid is 1:(0.1-1):(0.1-1).

[0016] Optionally, the insulating material includes one or more of aluminum oxide, magnesium hydroxide, magnesium oxide or zirconium oxide.

[0017] Optionally, the binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene or polyacrylonitrile.

[0018] Optionally, the D50 particle size of the phase change material is 0.5 μm to 8 μm.

[0019] Optionally, the D50 particle size of the insulating material is 0.5 μm to 8 μm.

[0020] Optionally, the thickness ratio of the active material layer to the tab glue layer is 1:(0.95-1.1).

[0021] In a second aspect, the present application provides a method for preparing an electrode sheet, comprising:

[0022] Phase change material, binder, insulating material and solvent are mixed to obtain a tab glue liquid, and the tab glue liquid is coated on the surface of the tab region of the current collector to form a tab glue layer to obtain an electrode plate; the electrode plate includes a current collector, one side surface of the current collector includes a tab region and an active material region, the surface of the tab region is provided with a tab glue layer, the surface of the active material region is provided with an active material layer, and the tab glue layer includes phase change material, binder and insulating material; the phase change material includes a polymer phase change material and a non-polymer phase change material.

[0023] In a third aspect, the present application provides a secondary battery, comprising the electrode plate as described in the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of the structure of a current collector provided in one embodiment of the present application;

[0025] Figure 2 A schematic diagram of the structure of an electrode plate provided in one embodiment of the present application;

[0026] Figure 3 A schematic diagram of the structure of an electrode plate provided in one embodiment of the present application;

[0027] Figure 4 This is a temperature change comparison diagram of Examples 1-3 and Comparative Examples 1-3 of the present application;

[0028] Figure 5 The thermogravimetric characterization diagram of the tab glue layer of Examples 1-3 and Comparative Examples 2-3 of the present application. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0030] During the charging and discharging process, the battery generates a lot of heat, which causes the temperature to rise sharply, which is not conducive to the safety performance of the battery. At present, air cooling and water cooling systems are mostly set outside the battery shell to promote the heat dissipation of the battery, but the above methods can only achieve cooling outside the battery. The heat inside the battery is still difficult to dissipate, and the cooling effect is relatively limited. In order to stabilize the temperature inside the battery and improve the problem of rapid temperature rise of the battery, the present application provides an electrode pole piece, which can effectively improve the problem of excessive temperature rise caused by rapid charging by setting a pole ear glue layer of a specific composition in the pole ear area of ​​the electrode, thereby improving the safety performance of the battery.

[0031] See also Figure 1 , Figure 1 This is a schematic diagram of the structure of the current collector provided in one embodiment of the present application. The surface of the current collector can be divided into a tab area a and an active material area b. The tab area is used to connect the electrode sheet in the battery cell to the external circuit, and the active material area is used to carry the active material. Figure 2 , Figure 2 A schematic diagram of the structure of an electrode plate provided in an embodiment of the present application, wherein an active material layer 20 is provided on the surface of the active material region of the current collector, and a tab glue layer 10 is provided on the surface of the tab region of the current collector in the electrode plate, and a certain blank area (i.e., an area where the tab glue layer is not provided) is reserved on the side of the tab region away from the active material region, and the blank area is used to weld a plurality of tabs together to achieve electrical connection, such as Figure 2 The electrode plate of the structure shown can be used in a laminated battery. Figure 3 , Figure 3A schematic diagram of the structure of an electrode plate provided in one embodiment of the present application, wherein an active material layer 20 is provided on the surface of the active material area of ​​the current collector, a lug glue layer 10 is provided on the surface of the lug area of ​​the current collector in the electrode plate, and a plurality of blank areas (i.e., areas where the lug glue layer is not provided) are reserved on the side of the lug area away from the active material area. The electrode plate of this structure can be used in a wound battery.

[0032] In the embodiment of the present application, the ear glue layer is a blended layer formed by a phase change material, a binder and an insulating material, and the ear glue layer specifically includes 25 to 75 parts by weight of a phase change material, 20 to 50 parts by weight of a binder and 0.1 to 10 parts by weight of an insulating material. The phase change material in the ear glue layer has good heat storage performance and can absorb the heat generated during the battery charging and discharging process, thereby suppressing the rapid increase in battery temperature; the role of the insulating material is to prevent a short circuit between the ear and the aluminum-plastic film that encapsulates the battery cell during packaging; the binder has a certain molding and supporting function that can match the phase change performance of the phase change material, ensuring that the ear glue layer has good structural stability and that the ear glue layer can adhere to the surface of the current collector; controlling the content of each component within a certain range can make the ear glue layer have both the protective function of the ear glue and can effectively suppress the increase in battery temperature to achieve temperature control of the battery, thereby greatly improving the safety performance of the battery.

[0033] In the present application, the ear glue layer is arranged between the welding point of the ear and the active material area. During the battery charging and discharging process, the electrochemical reaction rate and heat generation rate of the electrode plate close to the ear are both high, and with the increase of the charge and discharge rate, this non-uniformity is more significant, so that a large temperature difference is formed inside the battery. The ear glue layer is arranged in the ear area of ​​the current collector. On the one hand, it can effectively suppress the increase of the temperature in the ear area and alleviate the phenomenon of local overheating. On the other hand, the ear glue layer in the ear area has little effect on the electrical properties of the battery cell and electrode system, and will not produce too many negative effects, which can ensure the effective use of the battery capacity. In addition, the ear glue layer can also improve the rolling extension and processability of the current collector, so that the electrode plate can be well bonded with the glue-coated diaphragm, improve the curling and shrinkage of the diaphragm, and construct a battery cell with a stable structure.

[0034] In the present application, the phase change material includes a solid-solid phase change material, which mainly realizes temperature control through crystal transformation, and has the advantages of small volume change, no leakage, and no corrosion. In the embodiment of the present application, the phase change temperature of the phase change material is 20°C to 75°C, and the phase change temperature of the phase change material can be, but not limited to, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C or 75°C. In the embodiment of the present application, the weight percentage of the phase change material in the ear glue layer can be, but not limited to, 25, 30, 40, 50, 55, 60, 70 or 75 parts. In the embodiment of the present application, the phase change material includes a polymer phase change material and a non-polymer phase change material. The polymer phase change material has good stability in the battery, can improve the dispersibility of the non-polymer phase change material in the ear glue layer and the stability of the non-polymer phase change material in the battery, inhibit its side reaction with the electrolyte, and thus ensure that the ear glue layer has good stability, and the ear glue layer has a good temperature control effect. In some embodiments of the present application, the phase change temperature of the polymer phase change material is 30°C to 60°C, and the phase change temperature of the non-polymer phase change material is 55°C to 70°C. The polymer phase change material has a lower phase change temperature, and the non-polymer phase change material has a higher phase change temperature. The phase change material formed by the combination of polymer phase change materials and non-polymer phase change materials in different phase change temperature sections can make the ear glue layer have sensitive high temperature and low temperature dual regulation capabilities, broaden the range of temperature regulation, and thus better control the temperature of the battery.

[0035] In some embodiments of the present application, the mass ratio of the polymer phase change material to the non-polymer phase change material is 1:(0.5-2), and the mass ratio of the polymer phase change material to the non-polymer phase change material can be, but is not limited to, 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5 or 1:2. In some embodiments, the mass ratio of the polymer phase change material to the non-polymer phase change material is 1:(0.8-1.2), and controlling the mass ratio of the polymer phase change material to the non-polymer phase change material is conducive to the polymer phase change material to effectively wrap and protect the non-polymer phase change material and isolate the electrolyte, improve the stability of the ear glue layer, and the ear glue layer can have a good temperature control effect.

[0036] In some embodiments of the present application, the polymer phase change material includes one or more of polymer polyols, polystyrene, unsaturated polyesters, polyurethanes, polyphenylene ethers, polycarbonates or polyoxymethylene resins and copolymers thereof, wherein the polymer polyols include one or more of polyethylene glycol, polyvinyl alcohol or polypropylene glycol. In some embodiments of the present application, the non-polymer phase change material includes one or more of oxides, metal inorganic salts, paraffin wax and fatty acids, wherein the oxides include one or more of perovskite and vanadium dioxide, the metal inorganic salts include sodium thiosulfate, and the fatty acids include one or more of palmitic acid or stearic acid. In some embodiments, the phase change material includes polymer polyols in polymer phase change materials, oxides, metal inorganic salts and fatty acids in non-polymer phase change materials. In some embodiments, the phase change material includes polyethylene glycol, perovskite, sodium thiosulfate and fatty acids, and the mass ratio of perovskite, sodium thiosulfate and fatty acids is 1: (0.1-1): (0.1-1).

[0037] In some embodiments of the present application, the D50 particle size of the phase change material is 0.5 μm to 8 μm, and the D50 particle size of the phase change material can be, but is not limited to, 0.5 μm, 1 μm, 3 μm, 5 μm or 8 μm. Controlling the particle size of the phase change material can promote the phase change material to be more evenly dispersed in the tab glue layer, thereby achieving effective temperature control.

[0038] In some embodiments of the present application, the binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, and polyacrylonitrile. On the one hand, the above-mentioned binder has good and stable bonding force, which can stably compound the phase change material and the insulating material and adhere well to the foil substrate. On the other hand, the above-mentioned binder has good cohesive force, which can promote the formation of a relatively uniform ear glue layer. In the embodiment of the present application, the weight percentage of the binder in the ear glue layer can be specifically but not limited to 20, 30, 40 or 50 parts.

[0039] In some embodiments of the present application, the insulating material includes one or more of aluminum oxide, magnesium hydroxide, magnesium oxide or zirconium oxide. In the embodiments of the present application, the weight percentage of the insulating material in the ear glue layer can be, but is not limited to, 0.1, 1, 3, 5 or 10 parts. In some embodiments of the present application, the D50 particle size of the insulating material is 0.5μm to 8μm, and the D50 particle size of the insulating material can be, but is not limited to, 0.5μm, 1μm, 3μm, 5μm or 8μm. Controlling the particle size of the insulating material can promote the more uniform dispersion of the insulating material in the ear glue layer, achieve a good insulating effect of the ear glue layer, and the ear glue layer can have a certain structural strength, which is beneficial to improve the structural stability of the battery.

[0040] In some embodiments of the present application, the thickness ratio of the active material layer to the tab glue layer is 1:(0.95~1.1). In some embodiments, the thickness ratio of the active material layer to the tab glue layer is 1:(1~1.1). Controlling the thickness of the tab glue layer to be closer to the active material layer can effectively inhibit lithium plating in the battery and improve the safety of the battery.

[0041] In the present application, the electrode plate can be a positive electrode plate or a negative electrode plate. When the electrode plate is a positive electrode plate, the active material in the active material layer is a material that can reversibly release and embed active ions, and the active ions can be one or more of lithium ions, potassium ions, sodium ions, magnesium ions, aluminum ions, and zinc ions. When the electrode plate is a negative electrode plate, the active material in the active material layer can be one or more of carbon-based materials, silicon-based materials, and tin-based materials.

[0042] The electrode pole piece provided in the present application can effectively alleviate the problem of rapid temperature rise caused by excessive heat generation of the battery, and the pole ear glue layer has good stability and insulation, is not easy to deform, can ensure the flatness of the pole piece surface, and inhibit short circuit and lithium deposition at the pole ear. Applying it in the battery can greatly improve the safety performance of the battery.

[0043] The present application also provides a method for preparing the above-mentioned electrode sheet, comprising:

[0044] The phase change material, the binder, the insulating material and the solvent are mixed to obtain the tab glue solution, and the tab glue solution is coated on the tab area surface of the current collector to form a tab glue layer to obtain the electrode plate.

[0045] In some embodiments of the present application, the preparation of the ear glue includes: dispersing a binder in a solvent to form a binder solution, wherein the binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene or polyacrylonitrile, and the solvent includes N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethylacetamide (DMAC), tetrahydrofuran (THF); adding phase change material and insulating material to the binder solution to obtain the ear glue.

[0046] In some embodiments of the present application, the phase change material includes a non-polymer phase change material, and the non-polymer phase change material includes an oxide, a metal inorganic salt and a fatty acid. In the process of preparing the ear glue solution, the non-polymer phase change material is pretreated, and the pretreatment includes: adding the oxide and the metal inorganic salt to an organic solvent and stirring and mixing them evenly, then adding the fatty acid to the above solution, slowly stirring for 0.5h to 3h, and then raising the solution temperature to 50°C to 100°C until the solvent is evaporated to obtain the pretreated non-polymer phase change material. Pretreatment of the non-polymer phase change material can improve the stability of the non-polymer phase change material in the battery.

[0047] In some embodiments of the present application, the solid content of the tab glue is 20%-50%, and the viscosity of the tab glue is 1000cp-4000cp. In some embodiments of the present application, the tab glue is applied to the tab region of the current collector by extrusion coating equipment to obtain an electrode sheet.

[0048] The present application also provides a secondary battery. In some embodiments of the present application, the secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator between the positive electrode and the negative electrode, wherein the positive electrode or the negative electrode includes an electrode plate provided in the present application. In some embodiments of the present application, the secondary battery includes a positive electrode, a negative electrode, and a solid electrolyte or a semi-solid electrolyte between the positive electrode and the negative electrode. In the present application, the secondary battery may be any one of a lithium ion battery, a sodium ion battery, a potassium ion battery, an aluminum ion battery, a zinc ion battery, or a magnesium ion battery. In the present application, the separator of the secondary battery may be any separator known to those skilled in the art, for example, the separator may be one or more of a polyolefin microporous membrane, polyethylene terephthalate, polyethylene felt, glass fiber felt, or ultrafine glass fiber paper.

[0049] In the present application, the electrolyte of the secondary battery includes a solution of an electrolyte lithium salt in a non-aqueous solvent. In the embodiment of the present application, the electrolyte lithium salt includes lithium hexafluorophosphate (LiPF 6 ), lithium perchlorate (LiClO 4 ), lithium tetrafluoroborate (LiBF 4 ) lithium hexafluoroarsenate (LiAsF 6 ), lithium hexafluorosilicate (Li 2 SiF 6 ), lithium tetraphenylborate (LiB(C 6 H5) 4 ), lithium chloride (LiCl), lithium bromide (LiBr), lithium chloroaluminate (LiAlCl 4 ), lithium fluorocarbon sulfonate (LiC(SO 2 CF 3 ) 3 )、LiCH 3 SO 3 、LiN(SO 2 CF 3 ) 2 and LiN(SO 2 C 2 F 5 ) 2In some embodiments of the present application, the non-aqueous solvent includes one or more of chain acid esters and cyclic acid esters. In some embodiments of the present application, the chain acid ester includes one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC) and dipropyl carbonate (DPC). In some embodiments of the present application, the chain acid ester includes chain organic esters containing fluorine, sulfur or unsaturated bonds. In some embodiments of the present application, the cyclic acid ester includes one or more of ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), γ-butyrolactone (γ-BL) and sultone. In some embodiments of the present application, the cyclic acid ester includes cyclic organic esters containing fluorine, sulfur or unsaturated bonds. In some embodiments of the present application, the non-aqueous solvent includes one or more of chain ether and cyclic ether solution. In some embodiments of the present application, the cyclic ether includes one or more of tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), 1,3-dioxolane (DOL) and 4-methyl-1,3-dioxolane (4-MeDOL). In some embodiments of the present application, the cyclic ether includes a cyclic organic ether containing fluorine, sulfur or unsaturated bonds. In some embodiments of the present application, the chain ether includes one or more of dimethoxymethane (DMM), 1,2-dimethoxyethane (DME), 1,2-dimethoxypropane (DMP) and diethylene glycol dimethyl ether (DG). In some embodiments of the present application, the chain ether includes a chain organic ether containing fluorine, sulfur or unsaturated bonds. In an embodiment of the present application, the concentration of the electrolyte lithium salt in the electrolyte is 0.1mol / L-15mol / L. In some embodiments of the present application, the concentration of the electrolyte lithium salt is 1mol / L-10mol / L.

[0050] In the embodiment of the present application, the secondary battery can be prepared by using either a lamination process or a winding process.

[0051] The present application also provides an electronic device, which includes the secondary battery provided by the present application, and the secondary battery supplies power to the electronic device.

[0052] The technical solution of the present application is further described below with reference to a number of embodiments.

[0053] Example 1

[0054] A method for preparing an electrode sheet, comprising:

[0055] Graphite, binder (styrene-butadiene rubber SBR, carboxymethyl cellulose CMC), and conductive carbon black (SP) are mixed in a mass ratio of 9.7:0.2:0.1, and water is added to mix well to obtain a negative electrode slurry. The negative electrode slurry is applied on a copper foil with a scraper, and then dried and rolled to form an active material layer;

[0056] High voltage lithium cobalt oxide, binder (PVDF), and conductive agent (SP, CNT) are mixed in a mass ratio of 9.8:0.1:0.1, and water is added to mix well to obtain a positive electrode slurry. The positive electrode slurry is applied on an aluminum foil with a scraper, and then dried and rolled to form an active material layer;

[0057] The method for preparing the ear glue solution comprises:

[0058] Add 5 parts of perovskite and 3 parts of sodium thiosulfate pentahydrate into 10 parts of ethanol and stir to mix evenly. Add 2 parts of stearic acid into the above solution, stir slowly for 1 hour, and then heat the solution to 80° C. until the solvent is evaporated to obtain a composite non-polymer phase change material powder.

[0059] Disperse and dissolve 25 parts of binder in a solvent to form a binder solution, add 20 parts of polyethylene glycol (polymer phase change material), 30 parts of composite non-polymer phase change material powder and 5 parts of alumina (insulating filling powder) to the binder solution to obtain a tab glue solution, wherein the D50 particle size of the polymer phase change material and alumina is 5 μm, the phase change temperature of polyethylene glycol is 30°C to 60°C, and the phase change temperature of the non-polymer phase change material is 55°C to 70°C. Apply the tab glue solution to the tabs of copper foil and aluminum foil through an extrusion coating device to obtain positive and negative pole pieces, respectively.

[0060] Preparation of the battery: Using a 9 μm thick polypropylene (PP) as a separator, the positive electrode sheet, the negative electrode sheet and the separator stack are made into a battery cell, which is packaged and injected with 1 mol / L lithium hexafluorophosphate electrolyte (the solvent is a mixed solution of EC:PC:PP:EP with a volume ratio of 2:1:4:2, which contains 5% by mass of electrolyte additives, and the electrolyte additives are VC, FEC and cyanide) to obtain a battery. The battery of Example 1 is named S1.

[0061] Example 2

[0062] The difference between Example 2 and Example 1 is that the ratio of the polymer phase change material and the composite non-polymer phase change material in the ear glue solution of Example 2 is different, specifically including:

[0063] Disperse and dissolve 25 parts of a binder in a solvent to form a binder solution, add 25 parts of polyethylene glycol, 25 parts of a composite non-polymer phase change material powder and 5 parts of alumina to the binder solution to obtain a tab glue solution, and apply the tab glue solution on a current collector to obtain a positive electrode sheet and a negative electrode sheet, respectively.

[0064] A battery was prepared by the same method as in Example 1. The battery of Example 2 was named S2.

[0065] Example 3

[0066] The difference between Example 3 and Example 1 is that the ratio of the polymer phase change material and the composite non-polymer phase change material in the ear glue solution of Example 3 is different, specifically including:

[0067] Disperse and dissolve 25 parts of a binder in a solvent to form a binder solution, add 30 parts of polyethylene glycol, 20 parts of a composite non-polymer phase change material powder and 5 parts of alumina to the binder solution to obtain a tab glue solution, and apply the tab glue solution on a current collector to obtain a positive electrode sheet and a negative electrode sheet, respectively.

[0068] A battery was prepared by the same method as in Example 1. The battery of Example 2 was named S3.

[0069] Example 4

[0070] The difference between Example 4 and Example 1 is that the polymer phase change material in the ear glue of Example 4 is polyethylene oxide, specifically comprising:

[0071] Disperse and dissolve 25 parts of a binder in a solvent to form a binder solution, add 50 parts of polyethylene oxide and 5 parts of aluminum oxide to the binder solution to obtain a tab glue solution, and apply the tab glue solution on a current collector to obtain a positive electrode sheet and a negative electrode sheet, respectively.

[0072] The positive electrode sheet, the negative electrode sheet and the battery were prepared by the same method as in Example 1. The battery of Example 4 was named S4.

[0073] Example 5

[0074] The difference between Example 5 and Example 1 is that the non-polymer phase change material in the tab glue of Example 5 is perovskite. The preparation method of the tab glue comprises:

[0075] Disperse and dissolve 25 parts of binder in a solvent to form a binder solution, add 20 parts of polyethylene glycol (polymer phase change material), 30 parts of perovskite (non-polymer phase change material powder) and 5 parts of alumina (insulating filler powder) to the binder solution to obtain a tab glue solution. Apply the tab glue solution to the tabs of copper foil and aluminum foil through an extrusion coating device to obtain a positive electrode sheet and a negative electrode sheet, respectively.

[0076] The positive electrode sheet, the negative electrode sheet and the battery were prepared by the same method as in Example 1. The battery of Example 5 was named S5.

[0077] Example 6

[0078] The difference between Example 6 and Example 1 is that the non-polymer phase change material in the tab glue of Example 6 is sodium thiosulfate pentahydrate. The preparation method of the tab glue comprises:

[0079] Disperse and dissolve 25 parts of binder in a solvent to form a binder solution, add 20 parts of polyethylene glycol (polymer phase change material), 30 parts of sodium thiosulfate pentahydrate (non-polymer phase change material powder) and 5 parts of aluminum oxide (insulating filler powder) to the binder solution to obtain a tab glue solution. Apply the tab glue solution to the tabs of copper foil and aluminum foil through an extrusion coating device to obtain positive and negative pole pieces, respectively.

[0080] The positive electrode sheet, the negative electrode sheet and the battery were prepared by the same method as in Example 1. The battery of Example 6 was named S6.

[0081] Example 7

[0082] The difference between Example 7 and Example 1 is that the non-polymer phase change material in the tab glue of Example 7 is stearic acid. The preparation method of the tab glue comprises:

[0083] 25 parts of binder are dispersed and dissolved in a solvent to form a binder solution, and 20 parts of polyethylene glycol (polymer phase change material), 30 parts of stearic acid (non-polymer phase change material) and 5 parts of aluminum oxide (insulating filling powder) are added to the binder solution to obtain a tab glue solution. The tab glue solution is applied to the tabs of copper foil and aluminum foil through an extrusion coating device to obtain a positive electrode sheet and a negative electrode sheet, respectively.

[0084] The positive electrode sheet, the negative electrode sheet and the battery were prepared by the same method as in Example 1. The battery of Example 7 was named S7.

[0085] Comparative Example 1

[0086] The difference between Comparative Example 1 and Example 1 is that after the active material layer is prepared on the surface of the current collector, the positive electrode sheet, the negative electrode sheet and the separator are directly assembled into a battery, that is, the electrode sheet does not contain a lug glue layer.

[0087] A battery was prepared by the same method as in Example 1, and the battery of Comparative Example 1 was named D1.

[0088] Comparative Example 2

[0089] The difference between Comparative Example 2 and Example 1 is that the ear glue solution of Comparative Example 2 does not contain a polymer phase change material, specifically comprising:

[0090] Disperse and dissolve 25 parts of a binder in a solvent to form a binder solution, add 50 parts of a composite non-polymer phase change material and 5 parts of alumina to the binder solution to obtain a tab glue solution, and apply the tab glue solution on a current collector to obtain a positive electrode sheet and a negative electrode sheet, respectively.

[0091] A battery was prepared by the same method as in Example 1, and the battery of Comparative Example 2 was named D2.

[0092] Comparative Example 3

[0093] The difference between Comparative Example 3 and Example 1 is that the tab glue in Comparative Example 3 does not contain non-polymer phase change material, specifically comprising:

[0094] Disperse and dissolve 25 parts of a binder in a solvent to form a binder solution, add 50 parts of polyethylene glycol and 5 parts of aluminum oxide to the binder solution to obtain a tab glue solution, and apply the tab glue solution on a current collector to obtain a positive electrode sheet and a negative electrode sheet, respectively.

[0095] A battery was prepared by the same method as in Example 1, and the battery of Comparative Example 3 was named D3.

[0096] Effect Example

[0097] In order to verify the performance of the electrode plates and batteries prepared in this application, this application also provides an effect embodiment.

[0098] 1. Perform temperature tests on the batteries of Examples 1-7 and Comparative Example 1, specifically testing the temperature rise curve of the battery during charging. The specific test conditions are: the capacity of the test cell system is 4.45V, 2300mAh, the cell structure is a single-pole ear center structure, the cell charging strategy is 6C constant current and constant voltage to 4.25V, 2C constant current and constant voltage to 4.45V 0.02C cut-off, and a temperature sensor is used to collect the temperature at the positive ear, negative ear and cell surface of the cell. The evaluation standard is to take the three curves with the highest temperature for comparison, and record the highest temperature of the battery. Please refer to Table 1 for the test results.

[0099] Table 1 Temperature table of the batteries of Examples 1-7 and Comparative Example 1

[0100] Experimental Group Maximum temperature(℃) Comparative Example 1 60 Comparative Example 2 58 Comparative Example 3 57 Example 1 50 Example 2 46 Example 3 51 Example 4 54 Example 5 55 Example 6 54 Example 7 54

[0101] See also Figure 4 , Figure 4It is a temperature change comparison diagram of Examples 1-3 of the present application and Comparative Examples 1-3, wherein the temperature of the battery from high to low is Comparative Example 1, Comparative Example 2, Comparative Example 3, Example 3, Example 1 and Example 2. It can be seen from Table 1 that the temperature of the battery in Comparative Example 1 rises to 58 degrees at the highest when charging, while the battery in the embodiment of the present application has a pole piece containing a pole ear glue layer, and the maximum temperature of the battery cell is significantly reduced during charging, and the heating rate of the battery cell is slowed down. Comparative Examples 2 and 3 are batteries made of a single phase change material. In contrast, the temperature control effect of the composite phase change material used in Examples 1-3 of the present application is more significant. The pole ear glue layer of different compositions also shows different temperature control effects. The polymer phase change material of Examples 1-3 is polyethylene glycol, which has better performance than Example 4 using polyethylene oxide as the polymer phase change material. It can be seen from this that the application of the electrode pole piece in the battery can effectively improve the problem of excessive temperature rise during battery charging and improve the safety performance of the battery.

[0102] 2. The battery of Examples 1-7 and Comparative Examples 1-3 was subjected to a cycle performance test. The specific test conditions were as follows: the battery cell was charged to 4.25V at 6C constant current and constant voltage, and to 4.45V at 2C constant current and constant voltage, with a cut-off of 0.02C. After charging, the battery was allowed to stand for 5 minutes. The test environment temperatures of the battery were 25 degrees Celsius at room temperature and 45 degrees Celsius at high temperature, respectively. The room temperature cycle test was performed for 1000 cycles, and the high temperature cycle test was performed for 800 cycles. For the test results, please refer to Table 2.

[0103] Table 2 Cyclic performance of batteries of Examples 1-7 and Comparative Examples 1-3

[0104]

[0105] It can be seen from Table 2 that the capacity retention rate of the batteries of Comparative Examples 1-3 after 1000 cycles of 6C step charging at room temperature is less than 82.5%, and the capacity retention rate after 800 cycles of high temperature cycling at 45 degrees is less than 73%. Among them, the phase change material in the ear glue layer of Comparative Example 2 is a single non-polymer phase change material, and the capacity retention rate of the battery is low. The reason may be that there are certain side reactions between the non-polymer phase change material and the electrolyte, which causes the material to dissociate and the metal ions to dissolve, thereby reducing the capacity retention rate of the battery; the phase change material in the ear glue layer of Comparative Example 3 is a single polymer phase change material, and the battery capacity retention rate is slightly higher than that of Comparative Example 2, but its performance is still poor. In the battery of the embodiment of the present application, since the pole piece has a pole ear glue layer with a special composition, the pole ear glue layer can suppress the increase of the battery cell temperature during the battery charge and discharge cycle, slow down the degradation of battery performance caused by high temperature, and thus improve the long cycle performance of the battery cell. Embodiments 1-7 are composites of polymer phase change materials and non-polymer phase change materials. The polymer phase change material not only serves as a supporting skeleton to disperse the non-polymer phase change material, but also plays a role in isolating the electrolyte and protecting the non-polymer phase change material. Example 4 uses polyethylene oxide (PEO) as the polymer material, and the capacity retention rate is slightly worse than that of Examples 1-3, which shows that Example 1-3 uses polymer polyols as polymer phase change materials to make the battery have better cycle performance; Example 5, Example 6 and Example 7 respectively use single oxides, salts or fatty acids as non-polymer materials, and their battery performance is slightly worse than that of Examples 1-3. The reason is that the non-polymer materials composed of oxides, salts and fatty acids in Examples 1-3 have better stability, and oxides and salts are not easy to dissolve, which is beneficial to reduce the side reactions of the pole pieces and ensure that the pole ear glue layer has a good temperature control effect.

[0106] In order to further study the mechanism of improving the temperature control effect of the tab glue layer formed by the combination of polymer phase change material and non-polymer phase change material, the present application tests the temperature control effect of the tab glue layer of Examples 1-3 and Comparative Examples 2-3, and the testing method is as follows: the tab glue solutions of Examples 1-3 and Comparative Examples 2-3 are respectively coated on the surface of the aluminum foil to form tab glue layers of the same area, and the temperature control performance of the tab glue layer is tested by differential scanning calorimetry (DSC). The test temperature range is 10-100°C, and the heating rate is 2 degrees per minute. For the test results, please refer to Table 3, which is a table of the temperature control effects of the tab glue layers of Examples 1-3 and Comparative Examples 2-3.

[0107] Table 3 Temperature control effect of the ear glue layer of Examples 1-3 and Comparative Examples 2-3

[0108] Experimental Group Phase change temperature range (℃) Example 1 45-60 (peak 55) Example 2 50-68 (peak 58) Example 3 54-71 (peak 64) Comparative Example 2 40-55 (peak 47) Comparative Example 3 54-70 (peak 63)

[0109] See also Figure 5 , Figure 5The thermogravimetric characterization diagram of the tab glue layer of Examples 1-3 and Comparative Examples 2-3 of the present application is shown in FIG. Figure 5 It can be seen that changing the composition of the phase change material in the ear glue can adjust the temperature control range. Specifically, Example 2 uses a single non-polymer phase change material, and the ear glue layer has a phase change peak below 50 degrees. Example 3 uses a single polymer phase change material, and the ear glue layer has a phase change peak above 60 degrees. Examples 1-3 use a composite phase change material, and the phase change peak range of the ear glue layer shifts back to 50-70 degrees. At the same time, the endothermic peak area is significantly increased, which shows that the composite phase change material can absorb more heat and has a better temperature control effect.

[0110] The above is a preferred embodiment of the present application, but it should not be understood as limiting the scope of the present application. It should be noted that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application, and these improvements and modifications are also considered to be within the scope of protection of the present application.

Claims

1. An electrode plate, characterized in that: The electrode plate includes a current collector, and one side surface of the current collector includes a tab area and an active material area, the surface of the tab area is provided with a tab glue layer, and the surface of the active material area is provided with an active material layer; the tab glue layer includes a blended phase change material, a binder and an insulating material; the phase change material includes a polymer phase change material and a non-polymer phase change material; the phase change temperature of the polymer phase change material is 30°C~60°C; the phase change temperature of the non-polymer phase change material is 55°C~70°C; the non-polymer phase change material includes one or more of oxides, metal inorganic salts, paraffin, and fatty acids; the mass ratio of the polymer phase change material to the non-polymer phase change material is 1:(0.5~2).

2. The electrode plate according to claim 1, characterized in that: In the tab glue layer, the mass ratio of the phase change material, the adhesive and the insulating material is (25~75): (20~50): (0.1~10).

3. The electrode plate according to claim 1, characterized in that: The polymer phase change material includes one or more of polymer polyol, polystyrene, polyethylene oxide, unsaturated polyester, polyurethane, polyphenylene ether, polycarbonate or polyoxymethylene resin and copolymers thereof.

4. The electrode plate according to claim 1, characterized in that: The non-polymer phase change material includes perovskite, sodium thiosulfate and fatty acid; the mass ratio of the perovskite, sodium thiosulfate and fatty acid is 1:(0.1~1):(0.1~1).

5. The electrode plate according to claim 1, characterized in that: The insulating material includes one or more of aluminum oxide, magnesium hydroxide, magnesium oxide or zirconium oxide; and / or the binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene or polyacrylonitrile.

6. The electrode plate according to claim 1, characterized in that: The thickness ratio of the active material layer to the ear glue layer is 1:(0.95~1.1).

7. A method for preparing an electrode sheet according to any one of claims 1 to 6, characterized in that: include: Phase change material, binder, insulating material and solvent are mixed to obtain a tab glue liquid, and the tab glue liquid is coated on the surface of the tab region of the current collector to form a tab glue layer to obtain an electrode plate; the electrode plate includes a current collector, one side surface of the current collector includes a tab region and an active material region, the surface of the tab region is provided with a tab glue layer, the surface of the active material region is provided with an active material layer, and the tab glue layer includes phase change material, binder and insulating material; the phase change material includes a polymer phase change material and a non-polymer phase change material.

8. A secondary battery, characterized in that: Comprising the electrode plate as described in any one of claims 1-6.

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