Battery, preparation method thereof and power utilization device

Abstract

The invention relates to a battery and a preparation method thereof and an electric device, the battery comprises a positive plate, a negative plate and a diaphragm arranged between the positive plate and the negative plate, the positive plate comprises a positive current collector and a positive active material layer arranged on the positive current collector, and the positive active material layer comprises a first binder; the negative plate comprises a negative current collector and a negative active material layer arranged on the negative current collector, and the negative active material layer comprises a second binder; the diaphragm comprises a first coating, a porous base material and a second coating which are stacked in sequence, the first coating faces the positive electrode active material layer, the second coating faces the negative electrode active material layer, the first coating comprises a first binder, and the second coating comprises a second binder. In the battery, the binder in the diaphragm coating is consistent with the binder in the active material to which the coating faces, so that the problems of large pole piece deformation and poor pole piece interface flatness in the middle and later periods of battery circulation can be improved, and the cycle performance of the battery can be improved.

Description

Technical Field

[0001] The present application relates to the field of electrochemical energy storage, and particularly relates to a battery, a preparation method thereof, and an electrical device using the same. Background Art

[0002] During the process of cyclic charge and discharge of a secondary battery (such as a lithium-ion battery), due to the insertion and extraction of lithium ions, the volume of the particulate material (such as graphite particles) in the negative electrode expands and contracts, resulting in the deformation of the negative electrode sheet. This easily causes the gap between the positive and negative electrode sheets to widen, increasing the diffusion path of lithium ions and leading to the phenomenon of lithium deposition, seriously affecting the electrochemical performance and safety performance of the secondary battery. Summary of the Invention

[0003] In view of this, the present application provides a battery and a preparation method thereof to solve at least one of the above technical problems.

[0004] To achieve the above object, in a first aspect, the present application provides a battery, including a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. The positive electrode active material layer includes a first binder. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. The negative electrode active material layer includes a second binder. The separator includes a first coating, a porous substrate, and a second coating stacked in sequence. The first coating faces the positive electrode active material layer, and the second coating faces the negative electrode active material layer. The first coating includes a first binder, and the second coating includes a second binder.

[0005] Based on the first aspect, in some possible implementation manners, the positive electrode sheet, the separator, and the negative electrode sheet are stacked and wound.

[0006] Based on the first aspect, in some possible implementation manners, at least one of the first coating and the second coating further includes inorganic ceramic particles.

[0007] Based on the first aspect, in some possible implementation manners, the first coating further includes inorganic ceramic particles, and the content ratio of the first binder to the inorganic ceramic particles is 30 wt% to 50 wt%.

[0008] Based on the first aspect, in some possible implementation manners, the second coating further includes inorganic ceramic particles, and the content ratio of the second binder to the inorganic ceramic particles is 5 wt% to 20 wt%.

[0009] Based on the first aspect, in some possible implementation manners, the first binder includes polyvinylidene fluoride, and the glass transition temperature of the polyvinylidene fluoride is 35°C to 85°C.

[0010] Based on the first aspect, in some possible implementation manners, the second binder includes one or both of carboxymethyl cellulose and polyacrylic acid.

[0011] Based on the first aspect, in some possible implementation manners, the thickness of the first coating is 1 μm to 5 μm, and the thickness of the second coating is 1 μm to 3 μm.

[0012] In a second aspect, the present application provides a method for preparing a battery, including: providing a positive electrode sheet, the positive electrode sheet including a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector, the positive electrode active material layer including a first binder; providing a negative electrode sheet, the negative electrode sheet including a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector, the negative electrode active material layer including a second binder; providing a porous substrate, and respectively coating a first slurry and a second slurry on opposite two surfaces of the porous substrate, the first coating slurry including a first binder, the second slurry including a second binder, and obtaining a separator with a first coating and a second coating after curing; assembling the positive electrode sheet, the negative electrode sheet, and the separator, such that the separator is disposed between the positive electrode sheet and the negative electrode sheet, the first coating of the separator faces the positive electrode active material layer, and the second coating of the separator faces the negative electrode active material layer, to obtain a battery.

[0013] Based on the second aspect, in some possible implementation manners, the first slurry further includes inorganic ceramic particles, and the solid content of the first slurry is 10% to 40%.

[0014] Based on the second aspect, in some possible implementation manners, the first slurry further includes inorganic ceramic particles, and the viscosity of the first slurry is 1000 mPa·s to 4000 mPa·s.

[0015] Based on the second aspect, in some possible implementation manners, the first slurry further includes inorganic ceramic particles, and in the first slurry, the content ratio of the first binder is 3 wt% to 12 wt%.

[0016] Based on the second aspect, in some possible implementation manners, the second slurry further includes inorganic ceramic particles, and the solid content of the second slurry is 10% to 40%.

[0017] Based on the second aspect, in some possible implementation manners, the second slurry further includes inorganic ceramic particles, and the viscosity of the second slurry is 1000 mPa·s to 4000 mPa·s.

[0018] Based on the second aspect, in some possible implementation manners, the second slurry further includes inorganic ceramic particles, and in the second slurry, the content ratio of the second binder is 5 wt% to 10 wt%.

[0019] Based on the second aspect, in some possible implementation manners, the first binder includes polyvinylidene fluoride, and the glass transition temperature of the polyvinylidene fluoride is 35°C to 85°C.

[0020] Based on the second aspect, in some possible implementation manners, the second binder includes one or both of carboxymethyl cellulose and polyacrylic acid.

[0021] In a third aspect, the present application further provides an electrical device including the above-mentioned battery.

[0022] In the battery of the present application, the binder in the separator coating is the same as the binder in the active material (positive active material or negative active material) facing the coating, which is beneficial to regulating the adhesion force of the separator to the positive electrode sheet and the negative electrode sheet. Thus, while the positive electrode sheet and the negative electrode sheet can be normally infiltrated with the electrolyte, they can maintain good relative contact with the separator, reducing the delamination and peeling problems during production or use; and when the positive electrode sheet, the separator, and the negative electrode sheet are stacked and wound, it can cause the separator to bond with the negative electrode sheet, achieving the effect of restraining the negative electrode sheet and reducing the deformation amount of the negative electrode sheet during charge and discharge, which is beneficial to improving the problem of large deformation of the electrode sheet and poor flatness of the electrode sheet interface in the later stage of battery cycling, thereby helping to improve the cycling performance of the battery. Description of the Drawings

[0023] Figure 1 It is a schematic structural diagram of a battery provided by an embodiment of the present application.

[0024] Figure 2 It is a schematic structural diagram of an electrode assembly provided by an embodiment of the present application.

[0025] Main Element Symbol Description

[0026] Battery 1

[0027] Outer shell 11

[0028] Electrode assembly 12

[0029] Positive electrode sheet 121

[0030] Positive current collector 1211

[0031] Positive active material layer 1212

[0032] Negative electrode sheet 122

[0033] Negative current collector 1221

[0034] Negative active material layer 1222

[0035] Separator 123

[0036] First coating 1231

[0037] Second coating 1232

[0038] Porous substrate 1233

[0039] The following specific embodiments will further illustrate the present application in conjunction with the above-mentioned drawings. Specific embodiments

[0040] The embodiments of the present application will be described in detail below. The embodiments described below are exemplary and are only used to explain the present application and should not be construed as a limitation of the present application. It should be noted that unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs. Without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other. Many specific details are set forth in the following description to facilitate a thorough understanding of the present application. The described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments.

[0041] To improve the phenomenon that the negative electrode sheet pierces the separator and causes internal short circuit due to lithium deposition during the cycling process, the related art increases the thermal stability and puncture resistance of the separator by coating a ceramic layer on the surface of the separator to prevent lithium dendrites from piercing the separator and contacting the positive electrode sheet. Alternatively, an adhesive layer is coated on the surface of the separator to bond the separator to the positive electrode sheet, counteracting the stress generated during the charge and discharge process of the secondary battery and preventing the electrode sheet from deforming.

[0042] However, during the processing, the adhesive layer needs to be softened under certain temperature and pressure conditions to play a bonding role, which requires preheating and hot pressing treatment of the electrode assembly of the secondary battery, increasing the cost of equipment investment and energy investment. And for wound electrode assemblies, the adhesive layer usually has a strong binding effect on the positive electrode sheet, and the binding of the negative electrode sheet is generally achieved by controlling the winding tension of the electrode sheet and the separator. This method has relatively weak ability to inhibit the deformation of the negative electrode sheet, especially inside the wound electrode assembly.

[0043] When only a ceramic layer is coated on the surface of the separator, this coating does not have the effect of bonding the electrode sheets, and the ceramic particles are micro-nano scale particles. During the charge and discharge process of the battery, with the expansion or contraction of the electrode sheets, weak areas will also appear in the continuously distributed ceramic coating on the separator, affecting the battery safety performance.

[0044] Based on this, the present application provides a battery, which improves the deterioration problems of the electrochemical performance and safety performance of the battery caused by the deformation of the negative electrode sheet by improving the separator.

[0045] Please refer to Figure 1, an embodiment of the present application provides a battery 1, including a housing 11, an electrode assembly 12, and an electrolyte (not shown in the figure). The battery 1 can be a lithium-ion battery, a sodium-ion battery, or a potassium-ion battery. The electrode assembly 12 and the electrolyte are both located inside the housing 11.

[0046] The housing 11 can be a steel shell battery, an aluminum shell battery, etc. In some other embodiments, the housing 11 can also be a packaging bag obtained by encapsulating with a packaging film (such as an aluminum-plastic film), and at this time the battery 1 is a soft-pack battery.

[0047] The electrode assembly 12 can be a wound structure. For example, it is formed by winding a positive electrode sheet 121, a separator 123, and a negative electrode sheet 122 stacked in sequence. In some other embodiments, the electrode assembly 12 can be a laminated structure. For example, it is formed by alternately laminating a positive electrode sheet 121, a separator 123, and a negative electrode sheet 122 in sequence.

[0048] Please refer to Figure 2 , the electrode assembly 12 includes a positive electrode sheet 121, a negative electrode sheet 122, and a separator 123. The separator 123 is disposed between the positive electrode sheet 121 and the negative electrode sheet 122 to reduce the risk of short circuit caused by direct contact between the positive electrode sheet 121 and the negative electrode sheet 122.

[0049] The positive electrode sheet 121 includes a positive electrode current collector 1211 and a positive electrode active material layer 1212 disposed on at least one surface of the positive electrode current collector 1211. The positive electrode current collector 1211 can use aluminum foil, nickel foil, etc., and can also be a composite current collector disclosed in any prior art, such as but not limited to the current collector formed by combining the aforementioned conductive foil and a polymer substrate.

[0050] The positive electrode active material layer 1212 includes a positive electrode material. The positive electrode material includes a compound that can reversibly intercalate and deintercalate lithium ions (i.e., a lithiated intercalation compound). In some embodiments, the positive electrode material can include a lithium transition metal composite oxide. The lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese, and nickel. In some embodiments, the positive electrode material can include but not limited to lithium cobalt oxide (LiCoO 2 ), lithium nickel cobalt manganese ternary material (NCM), lithium manganese oxide (LiMn 2 O 4 ), lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O 4 ), or lithium iron phosphate (LiFePO 4 ) at least one of them.

[0051] The positive electrode active material layer 1212 may further include a first binder for binding the positive electrode active material particles to facilitate the formation of a film layer, and at the same time, it can also improve the bonding force between the positive electrode active material layer 1212 and the positive electrode current collector 1211. In some embodiments, the first binder may include, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon, etc.

[0052] The positive electrode active material layer 1212 may further include a conductive material, and the conductive material includes, but is not limited to, carbon-based materials, metal-based materials, conductive polymers, or any combination thereof. In some embodiments, the carbon-based materials may include, but are not limited to, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based materials may include, but are not limited to, metal powder or metal fiber, such as copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer may be a polyphenylene derivative.

[0053] The negative electrode sheet 122 includes a negative electrode current collector 1221 and a negative electrode active material layer 1222 provided on at least one surface of the negative electrode current collector 1221. The negative electrode current collector 1221 may use at least one of copper foil, nickel foil, stainless steel foil, titanium foil, or a carbon-based current collector, etc., and may also be a composite current collector disclosed in any prior art, such as, but not limited to, the current collector formed by combining the aforementioned conductive foil and a polymer substrate.

[0054] The negative electrode active material layer 1222 includes a negative electrode material, and the negative electrode material includes at least one of graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiOx (0.5 < x < 1.6), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO 2 、spinel-structured lithium titanate, lithiated TiO 2 -Li 4 Ti 5 O 12 、Li-Al alloy, and metallic lithium.

[0055] The negative electrode active material layer 1222 further includes a second binder for binding the negative electrode active material particles to facilitate the formation of a film layer, and at the same time, it can also improve the bonding force between the negative electrode active material layer 1222 and the negative electrode current collector 1221. In some embodiments, the second binder may include, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon, etc.

[0056] The negative electrode active material layer 1222 may further include a conductive material, and the conductive material includes, but is not limited to, carbon-based materials, metal-based materials, conductive polymers, or any combination thereof. In some embodiments, the carbon-based materials may include, but are not limited to, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based materials may include, but are not limited to, metal powder or metal fiber, such as copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer may be a polyphenylene derivative.

[0057] The separator 123 includes a first coating 1231, a porous substrate 1233, and a second coating 1232 that are sequentially laminated. The first coating 1231 is disposed facing the positive electrode active material layer 1212, the second coating 1232 is disposed facing the negative electrode active material layer 1222, the first coating 1231 includes a first binder, and the second coating 1232 includes a second binder.

[0058] The binder in the coating of the separator 123 is the same as the binder in the active material (positive electrode active material or negative electrode active material) facing the coating, which is beneficial to regulating the bonding force of the separator 123 to the positive electrode sheet 121 and the negative electrode sheet 122. Thus, while the positive electrode sheet 121 and the negative electrode sheet 122 can be normally wetted by the electrolyte, they can maintain good relative contact with the separator 123, reducing the problems of delamination and peeling during production or use.

[0059] In some embodiments, the positive electrode sheet 121, the separator 123, and the negative electrode sheet 122 are laminated and wound. When the positive electrode sheet 121, the separator 123, and the negative electrode sheet 122 are laminated and wound, the setting of the binder of the separator 123 coating can cause the separator 123 to have a bonding effect with the negative electrode sheet 122, achieving the binding of the negative electrode sheet 122 and reducing the deformation amount of the negative electrode sheet 122 during charge and discharge. Thus, it is beneficial to improve the problems of large deformation of the electrode sheet and poor flatness of the electrode sheet interface in the middle and late stages of the cycle of the battery 1, thereby contributing to improving the cycle performance of the battery 1.

[0060] In some embodiments, at least one of the first coating 1231 and the second coating 1232 further includes inorganic ceramic particles. For example, in some embodiments, both the first coating 1231 and the second coating 1232 include inorganic ceramic particles. Adding inorganic ceramic particles to the coating of the separator 123 is beneficial to improving the puncture resistance of the battery 1, reducing the risk of the battery 1 being pierced by lithium dendrites, enhancing the battery 1's resistance to short circuit and thermal runaway, so that the battery 1 can be charged and discharged more safely. Among them, the inorganic ceramic particles may include at least one of hafnium dioxide, strontium titanate, tin dioxide, cesium oxide, magnesium oxide, nickel oxide, calcium oxide, barium oxide, zinc oxide, zirconium oxide, yttrium oxide, aluminum oxide, titanium oxide, silicon dioxide, boehmite, magnesium hydroxide or aluminum hydroxide.

[0061] In some embodiments, the first coating 1231 further includes inorganic ceramic particles, and the content ratio of the first binder to the inorganic ceramic particles is 30 wt% to 50 wt%. For example, the content ratio of the first binder to the inorganic ceramic particles may be 30 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt%, 40 wt%, 42 wt%, 44 wt%, 46 wt%, 48 wt%, 50 wt% or any value within the range formed by any two of the above values. It is found in this application that when the content ratio of the first binder to the inorganic ceramic particles is controlled within the above range, it is beneficial to improve the function of the first binder and enable the separator 123 to have good puncture resistance. When the obtained separator 123 is applied to the battery 1, it can reduce the phenomenon that the positive electrode sheet 121 falls off due to insufficient adhesion between the positive electrode sheet 121 and the separator 123 during the cycling process of the battery 1, and reduce the risk of the separator 123 being pierced, so that the positive electrode sheet 121 maintains good flatness during the cycling process of the battery 1.

[0062] In some embodiments, the second coating 1232 further includes inorganic ceramic particles, and the content ratio of the second binder to the inorganic ceramic particles is 5 wt% to 20 wt%. For example, the content ratio of the second binder to the inorganic ceramic particles may be 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt% or any value within the range formed by any two of the above values. It is found in this application that when the content ratio of the second binder to the inorganic ceramic particles is controlled within the above range, it is beneficial to improve the function of the second binder and enable the separator 123 to have good puncture resistance. When the obtained separator 123 is applied to the battery 1, it can reduce the phenomenon that the negative electrode sheet 122 falls off due to insufficient adhesion between the negative electrode sheet 122 and the separator 123 during the cycling process of the battery 1, and reduce the risk of the separator 123 being pierced, so that the negative electrode sheet 122 maintains good flatness during the cycling process of the battery 1.

[0063] In some embodiments, the first binder includes polyvinylidene fluoride, and the glass transition temperature (Tg value) of polyvinylidene fluoride is 35°C to 85°C. For example, the Tg value of polyvinylidene fluoride can be 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or any value within the range formed by any two of the above values. The above glass transition temperature refers to the glass transition temperature of polyvinylidene fluoride powder. The glass transition temperature of conventional polyvinylidene fluoride powder usually exceeds 100°C. In this application, polyvinylidene fluoride with a lower glass transition temperature is selected as the raw material of the first binder. After being cold-pressed into a film, it can produce a good bonding effect with the electrode sheet, which is beneficial to controlling the binding effect on the positive electrode sheet 121, thereby helping to improve the problems of large deformation of the electrode sheet and poor flatness of the electrode sheet interface in the middle and late stages of the cycle of the battery 1, and thus contributing to improving the cycle performance of the battery 1.

[0064] In some embodiments, the second binder includes one or both of carboxymethyl cellulose and polyacrylic acid, which is beneficial to strengthening the bonding effect between the negative electrode sheet 122 and the separator 123.

[0065] In some embodiments, the thickness of the first coating 1231 is 1 μm to 5 μm, and the thickness of the second coating 1232 is 1 μm to 3 μm. For example, the thickness of the first coating 1231 can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or any value within the range formed by any two of the above values, and the thickness of the second coating 1232 can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm or any value within the range formed by any two of the above values.

[0066] In some embodiments, the material of the porous substrate 1233 includes one or more of PE, PP, and a composite material of PE and PP.

[0067] The electrolyte (not shown in the figure) functions to conduct ions between the positive electrode sheet 121 and the negative electrode sheet 122. In some embodiments, the electrolyte includes a lithium salt and an organic solvent. The lithium salt can be selected from but not limited to lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium perchlorate (LiClO 4 ), lithium tetraphenylborate (LiB(C 6 H 5 ) 4 ), lithium methanesulfonate (LiCH 3 SO 3 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiCF3 SO 3 )、 lithium bis(trifluoromethanesulfonyl)imide (LiN(SO 2 CF 3 ) 2 、 lithium tris(trifluoromethanesulfonyl)methide (LiC(SO 2 CF 3 ) 3 )、 lithium bis(oxalato)borate (LiBOB) and lithium difluorophosphate (LiPO 2 F 2 ) or one or more of them. For example, the lithium salt is selected as LiPF 6 , because it can give a high ionic conductivity and improve the cycling performance. The organic solvent can be a carbonate compound, a carboxylate compound, an ether compound, a nitrile compound, other organic solvents or a combination thereof. Examples of the carbonate compound include but are not limited to diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene ethylene carbonate (VEC), fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethyl ethylene carbonate or a combination thereof.

[0068] One embodiment of the present application further provides a method for preparing the battery 1, including:

[0069] Step 1: Provide a positive electrode sheet 121, the positive electrode sheet 121 includes a positive electrode current collector 1211 and a positive electrode active material layer 1212 provided on the positive electrode current collector 1211, and the positive electrode active material layer 1212 includes a first binder.

[0070] In some embodiments, the first binder includes polyvinylidene fluoride, and the glass transition temperature of the polyvinylidene fluoride is 35 °C to 85 °C. For example, the Tg value of the polyvinylidene fluoride can be 35 °C, 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C or any value within the range composed of any two of the above values.

[0071] Step 2: Provide a negative electrode sheet 122, the negative electrode sheet 122 includes a negative electrode current collector 1221 and a negative electrode active material layer 1222 provided on the negative electrode current collector 1221, and the negative electrode active material layer 1222 includes a second binder.

[0072] In some embodiments, the second binder includes one or both of carboxymethyl cellulose and polyacrylic acid.

[0073] Step 3: Provide a porous substrate 1233, and coat a first slurry and a second slurry on two opposite surfaces of the porous substrate 1233 respectively. The first coating slurry includes a first binder, and the second slurry includes a second binder. After curing, a first coating 1231 and a second coating 1232 are obtained, and a separator 123 is obtained.

[0074] In some embodiments, the first slurry further includes inorganic ceramic particles, and the solid content of the first slurry is 10% to 40%. For example, the solid content of the first slurry is 10%, 15%, 20%, 25%, 30%, 35%, 40% or any value within the range formed by any two of the above values. Controlling the solid content of the first slurry within the above range is beneficial to controlling the content of inorganic ceramic particles (such as ceramic particles) in the first slurry within a suitable range, thereby being beneficial to improving the protective effect of the inorganic ceramic particles, being beneficial to reducing the risk of lithium dendrite piercing of the battery 1, and enhancing the anti-short circuit and thermal runaway prevention capabilities of the battery 1, so that the battery 1 can be charged and discharged more safely.

[0075] In some embodiments, the viscosity of the first slurry is 1000 mPa·s to 4000 mPa·s. For example, the viscosity of the first slurry is 1000 mPa·s, 1500 mPa·s, 2000 mPa·s, 2500 mPa·s, 3000 mPa·s, 3500 mPa·s, 4000 mPa·s or any value within the range formed by any two of the above values. In some embodiments, the dynamic viscosity of the first slurry is measured by the rotation method to obtain the viscosity of the first slurry. Controlling the viscosity of the first slurry within the above range is beneficial to uniform coating.

[0076] In some embodiments, in the first slurry, the content ratio of the first binder is 3 wt% to 12 wt%. For example, in the first slurry, the content ratio of the first binder can be 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt% or any value within the range formed by any two of the above values. Controlling the content ratio of the first binder within the above range is beneficial to controlling the content ratio of the first binder and the inorganic ceramic particles in the first coating 1231 to fall within a preset range.

[0077] In some embodiments, the second slurry further includes inorganic ceramic particles, and the solid content of the second slurry is 10% to 40%. For example, the solid content of the second slurry is 10%, 15%, 20%, 25%, 30%, 35%, 40%, or any value within the range formed by any two of the above values. Controlling the solid content of the second slurry within the above range is beneficial to controlling the content of inorganic ceramic particles (such as ceramic particles) in the second slurry within a suitable range, thereby facilitating improving the protective effect of the inorganic ceramic particles, reducing the risk of lithium dendrite piercing in Battery 1, enhancing the short-circuit resistance and thermal runaway prevention capabilities of Battery 1, and thus making the charging and discharging of Battery 1 safer.

[0078] In some embodiments, the viscosity of the second slurry is 1000 mPa·s to 4000 mPa·s. For example, the viscosity of the second slurry is 1000 mPa·s, 1500 mPa·s, 2000 mPa·s, 2500 mPa·s, 3000 mPa·s, 3500 mPa·s, 4000 mPa·s, or any value within the range formed by any two of the above values. In some embodiments, the kinematic viscosity of the second slurry is measured by the rotation method to obtain the viscosity of the second slurry. Controlling the viscosity of the second slurry within the above range is beneficial to uniform coating.

[0079] In some embodiments, in the second slurry, the content ratio of the second binder is 5 wt% to 10 wt%. For example, in the second slurry, the content ratio of the second binder is 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or any value within the range formed by any two of the above values. Controlling the content ratio of the second binder within the above range is beneficial to controlling the content ratio of the second binder to the inorganic ceramic particles in the second coating 1232 to fall within a preset range.

[0080] Step Four: Assemble the positive electrode sheet 121, the negative electrode sheet 122, and the separator 123, such that the separator 123 is disposed between the positive electrode sheet 121 and the negative electrode sheet 122, the first coating 1231 of the separator 123 faces the positive electrode active material layer 1212, and the second coating 1232 of the separator 123 faces the negative electrode active material layer 1222 to obtain Battery 1.

[0081] The binder in the separator 123 coating is consistent with the binder in the active material (positive electrode active material or negative electrode active material) facing the coating, which is beneficial to regulating the adhesion force of the separator 123 to the positive electrode sheet 121 and the negative electrode sheet 122. Thus, while the positive electrode sheet 121 and the negative electrode sheet 122 can be normally wetted by the electrolyte, they can maintain good relative contact with the separator 123, reducing the problems of delamination and shedding during production or use. Moreover, when the positive electrode sheet 121, the separator 123, and the negative electrode sheet 122 are stacked and wound, it is also beneficial to improving the problems of large deformation of the electrode sheet and poor flatness of the electrode sheet interface in the middle and late stages of the cycle of the battery 1, thereby contributing to improving the cycle performance of the battery 1.

[0082] Another embodiment of the present application further provides an electrical device including the above-mentioned battery 1. In some embodiments, the battery 1 of the present application can be used in but not limited to the following electrical devices: laptop computers, pen-input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, liquid crystal televisions, hand-held cleaners, portable CD players, mini-discs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, motorized bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household storage batteries or lithium-ion capacitors, etc.

[0083] The solutions of the present application will be explained below in conjunction with embodiments. Those skilled in the art will understand that the following examples are only for explaining the present application and cannot be construed as a limitation to the present application. Unless otherwise stated, the reagents, software, and instruments involved in the following embodiments that are not specifically stated are all commercially available products or open-source.

[0084] Example 1:

[0085] A battery, the preparation method of which includes:

[0086] In the first step, prepare the positive electrode sheet: Put PVDF with a Tg value of 45 °C and a methyl solvent into a blender, stir at 3000 r / min for self-rotation and 30 r / min for revolution for 60 min to obtain the first adhesive solution. Put lithium iron phosphate and carbon black into the blender, and mix them in a dry mixing manner, stir at 3000 r / min for self-rotation and 30 r / min for revolution for 30 min, add 30% of the first adhesive solution, and knead for 100 min; then add 70% of the first adhesive solution, stir and disperse for 60 min; adjust the viscosity of the slurry with a solvent to obtain the first slurry. Transfer the first slurry to the positive electrode coating equipment, control the feeding speed, coating speed, dressing width, and oven temperature to obtain the positive electrode sheet with the required surface density, and roll and die-cut the battery positive electrode sheet according to the set compaction density, rolling thickness, electrode sheet length, tab number, and tab spacing.

[0087] Step 2: Prepare the negative electrode sheet: Put polyacrylic acid and deionized water into a blender, stir at a self-rotation speed of 3000 r / min and a revolution speed of 30 r / min for 60 min to obtain the second adhesive solution. Put 70% of the second adhesive solution into the blender, add carbon black, first stir slowly at a revolution speed of 10 r / min for 10 min, then stir at a self-rotation speed of 2000 r / min and a revolution speed of 30 r / min for 20 min; put in artificial graphite, and stir at a self-rotation speed of 2000 r / min and a revolution speed of 30 r / min for 120 min; then add 30% of the second adhesive solution and deionized water to adjust the viscosity of the slurry; finally add styrene-butadiene rubber, and disperse to obtain the second slurry. Transfer the second slurry to the negative electrode coating equipment, control the feeding speed, coating speed, dressing width and oven temperature to obtain the negative electrode sheet with the required surface density, and roll and die-cut the battery negative electrode sheet according to the set compaction density, rolling thickness, electrode sheet length, number of tabs and tab spacing.

[0088] Step 3: Prepare the separator: Provide a first mixture of PVDF with a Tg value of 45 °C, inorganic ceramic particles and deionized water, and make the content ratio of PVDF in the first mixture 8 wt%, and put the first mixture into a blender rotating at 3000 r / min and revolving at 30 r / min and stir for 60 min to obtain the first slurry; provide a second mixture of polyacrylic acid, inorganic ceramic particles and deionized water, and make the content ratio of polyacrylic acid in the second mixture 6 wt%, and put the second mixture into a blender rotating at 3000 r / min and revolving at 30 r / min and stir for 60 min to obtain the second slurry; coat the first slurry on one side of the PE separator by spraying, and dry to form a first coating with a thickness of 2 μm; coat the second slurry on the other side of the PE separator by spraying, and dry to form a second coating of the separator with a thickness of 1.5 μm.

[0089] Step 4: Assembly: Place the first coating side of the separator facing the positive electrode sheet and the second coating side of the separator facing the negative electrode sheet, and wind the positive electrode sheet, negative electrode sheet and separator into a core by winding. After the core is formed at 85 °C and 0.6 MPa, the double cores are assembled into the shell, vacuum baked, injected with electrolyte, and chemically formed and capacitanced to assemble the battery.

[0090] Example 2:

[0091] The difference from Example 1 is that in the preparation of the separator in Step 3, inorganic ceramic particles are not added to both the first mixture and the second mixture.

[0092] Example 3:

[0093] The difference from Example 1 is that the Tg value of PVDF is 120 °C.

[0094] Comparative Example 1:

[0095] The difference from Example 1 is that in the third step of preparing the separator, the first slurry is coated only on one side of the PE separator, and this side faces the positive electrode sheet in the fourth step.

[0096] Comparative Example 2:

[0097] The difference from Example 1 is that in the third step of preparing the separator, both the first mixture and the second mixture are inorganic ceramic particles and deionized water.

[0098] The batteries of Examples 1-3 and Comparative Examples 1-2 of the present application were tested, including:

[0099] 1. Capacity test of the battery: At 25 °C, after discharging the newly prepared battery, the initial discharge capacity of the battery was tested according to the constant power charge-discharge mode of 0.5P / 0.5P.

[0100] 2. Capacity retention rate test of the battery: At 25 °C, according to the constant power charge-discharge mode of 0.5P / 0.5P, 100 cycles were performed, and the discharge capacity of the battery at the 100th cycle was tested.

[0101] 3. Observe the state of the electrode sheet after charge and discharge of the battery: The newly prepared battery and the battery after 100 cycles were disassembled after being fully charged to observe the battery state and the state of the negative electrode sheet.

[0102] Please refer to Table 1 for the above test results.

[0103] Table 1. Test results of capacity retention rate and negative electrode sheet state of batteries of Examples 1-3 and Comparative Examples 1-2 of the present application

[0104]

[0105] In the batteries of Examples 1-3 of the present application, the binder in the separator coating is consistent with the binder in the active material (positive electrode active material or negative electrode active material) facing the coating. In a wound battery, it can cause the separator to bond with the negative electrode sheet, achieving the effect of binding the negative electrode sheet and reducing the deformation amount of the negative electrode sheet during charge and discharge, thereby facilitating the improvement of the problems of large deformation of the electrode sheet and poor flatness of the electrode sheet interface in the later stage of the existing battery cycle. Therefore, the batteries of Examples 1-3 of the present application have higher capacity and capacity retention rate, and the negative electrode sheet is relatively flat after charge and discharge cycles.

[0106] Among them, compared with Example 2, the separator coating of Example 1 further includes inorganic ceramic particles, which is beneficial to improving the puncture resistance of the battery, reducing the risk of the battery being pierced by lithium dendrites, enhancing the battery's anti-short circuit and thermal runaway prevention capabilities, and thus making the battery charge and discharge safer.

[0107] Compared with Example 3, in the separator coating of Example 1, the Tg value of the PVDF used further meets the preset range. In this application, polyvinylidene fluoride with a lower glass transition temperature is selected as the raw material of the first binder. After it is cold-pressed to form a separator, it can produce a good bonding effect with the electrode sheet, which is beneficial to controlling the binding effect on the positive electrode sheet, thereby facilitating the improvement of the problems of large deformation of the electrode sheet and poor flatness of the electrode interface in the middle and late stages of battery cycling, and thus contributing to improving the cycling performance of the battery. Therefore, the battery of Example 1 has a relatively higher capacity retention rate.

[0108] Compared with Examples 1-3 of this application, in Comparative Example 1, only the first slurry is coated on one side of the PE separator, and no binder is used in the separator coating of Comparative Example 2. Under the same core forming process, the flatness of the interface of the negative electrode sheet in Comparative Example 1 and Comparative Example 2 is relatively worse when fully charged, which easily leads to difficulties in lithium ion deintercalation-insertion and the accumulation of side reaction gases during the charge and discharge process, resulting in a decrease in battery capacity, lithium dendrite growth, and the formation of purple / black spots / dead lithium due to local over-insertion, etc., affecting the electrical performance and safety performance of the battery.

[0109] The above embodiments are only used to illustrate the technical solutions of this application and not to limit them. Although this application has been described in detail with reference to the above preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of this application can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of this application.

Claims

1. A battery comprising a positive electrode sheet, a negative electrode sheet and a separator disposed between the positive electrode sheet and the negative electrode sheet, characterized in that: The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, wherein the positive electrode active material layer comprises a first binder; The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, wherein the negative electrode active material layer comprises a second binder; The separator includes a first coating layer, a porous substrate, and a second coating layer stacked in sequence, wherein the first coating layer is arranged facing the positive electrode active material layer, the second coating layer is arranged facing the negative electrode active material layer, the first coating layer includes the first binder, and the second coating layer includes the second binder.

2. The battery according to claim 1, characterized in that The positive electrode sheet, the separator and the negative electrode sheet are stacked and wound.

3. The battery according to claim 1, characterized in that At least one of the first coating layer and the second coating layer further includes inorganic ceramic particles.

4. The battery according to claim 3, characterized in that The battery satisfies at least one of the following conditions: (1) The first coating layer further includes inorganic ceramic particles, and the content ratio of the first binder to the inorganic ceramic particles is 30 wt % to 50 wt %; (2) The second coating layer further includes inorganic ceramic particles, and the content ratio of the second binder to the inorganic ceramic particles is 5 wt % to 20 wt %.

5. The battery according to claim 1, characterized in that The first binder includes polyvinylidene fluoride, and the glass transition temperature of the polyvinylidene fluoride is 35°C to 85°C.

6. The battery according to claim 1, characterized in that The second binder includes one or both of carboxymethyl cellulose and polyacrylic acid.

7. The battery according to claim 1, characterized in that The thickness of the first coating layer is 1 μm to 5 μm, and the thickness of the second coating layer is 1 μm to 3 μm.

8. A method for preparing a battery as claimed in claim 1, characterized in that: include: Providing a positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, the positive electrode active material layer comprising a first binder; Providing a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, the negative electrode active material layer comprising a second binder; Providing a porous substrate, and coating a first slurry and a second slurry on two opposite surfaces of the porous substrate, respectively, wherein the first slurry includes the first binder, and the second slurry includes the second binder, and after curing, a diaphragm having a first coating and a second coating is obtained; The positive electrode sheet, the negative electrode sheet and the separator are assembled so that the separator is disposed between the positive electrode sheet and the negative electrode sheet, the first coating of the separator is disposed facing the positive electrode active material layer, and the second coating of the separator is disposed facing the negative electrode active material layer, to obtain the battery.

9. The preparation method according to claim 8, characterized in that: At least one of the first slurry and the second slurry further comprises inorganic ceramic particles, and the preparation method satisfies at least one of the following conditions: (1) The solid content of the first slurry is 10% to 40%; (2) The viscosity of the first slurry is 1000 mPa·s to 4000 mPa·s; (3) In the first slurry, the content of the first binder is 3wt% to 12wt%; (4) the solid content of the second slurry is 10% to 40%; (5) The viscosity of the second slurry is 1000 mPa·s to 4000 mPa·s; (6) In the second slurry, the content of the second binder is 5wt% to 10wt%.

10. An electrical device, characterized in that: The electrical device comprises the battery according to any one of claims 1 to 7.

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