CN116964854A

CN116964854A - Electrochemical device and electronic device

Info

Publication number: CN116964854A
Application number: CN202280010144.8A
Authority: CN
Inventors: 李学成
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd
Priority date: 2022-09-22
Filing date: 2022-09-22
Publication date: 2023-10-27
Also published as: WO2024060128A1

Abstract

The application provides an electrochemical device and an electronic device. The electrochemical device comprises a positive pole piece, a negative pole piece and a separation film. The isolating film is arranged between the positive pole piece and the negative pole piece. The separator is provided with a first area exceeding the positive pole piece in the width direction of the separator, the first area comprises a first non-hardening area overlapping with the projection of the negative pole piece in the thickness direction of the separator, and a first hardening area exceeding the edge of the negative pole piece in the width direction and provided with a first hardening agent, the hardness of the first hardening area is greater than 1.0H, and the hardness of the first non-hardening area is less than 1.0H. Therefore, the impact resistance of the isolating membrane is enhanced, the electrolyte impact can be resisted, and the safety performance of the electrochemical device in falling is ensured.

Description

Electrochemical device and electronic device

Technical Field

The present application relates to the field of electrochemical energy storage, in particular to electrochemical devices and electronic devices.

Background

With the widespread use of electrochemical devices (e.g., lithium ion batteries) in various electronic products, users have also placed increasing demands on the safety performance of electrochemical devices, such as the possibility of fire explosion after multiple falls. It was found that the cause of voltage drop or fire explosion in dropping is mainly internal short circuit caused by shrinkage of the separator inside the lithium ion battery. In multiple drops of lithium ion batteries, the free electrolyte can repeatedly impact the separator. When the impact force of the electrolyte is greater than the binding force of the isolating film, the isolating film in the lithium ion battery contracts, the positive pole piece and the negative pole piece can be in direct contact with each other, and internal short circuit is caused, so that the voltage is greatly reduced, and the failure is greatly reduced or the direct smoking and the ignition are realized. Thus, the shrinkage of the isolating film can present serious threat to the safety of the lithium ion battery, and needs to be solved urgently.

Disclosure of Invention

An embodiment of the present application provides an electrochemical device including a positive electrode tab, a negative electrode tab, and a separator. The isolating film is arranged between the positive pole piece and the negative pole piece. The separator is provided with a first area exceeding the positive pole piece in the width direction of the separator, the first area comprises a first non-hardening area overlapping with the projection of the negative pole piece in the thickness direction of the separator, and a first hardening area exceeding the edge of the negative pole piece in the width direction and provided with a first hardening agent, the hardness of the first hardening area is greater than 1.0H, and the hardness of the first non-hardening area is less than 1.0H.

In some embodiments, the first hardened region has a hardness of 1.5H to 2.0H. In this range, in the drop test, the separator in each cell hardly contracts, and if it is lower than the lower limit value, the separator of the single cell hardly contracts at several places, and if the hardness of the separator is too high, the hardness is too high, more than 2.0H, the separator is relatively poor in flexibility, relatively large in deformation, irregular in edges, leading to wavy edges, poor filling of electrolyte, easy disconnection of lithium ion diffusion channels, and thus cycle deterioration of lithium precipitation.

In some embodiments, one or both sides of the first region include a first hardened region having a width of 0.2mm to 2.5mm in a width direction, and the first hardening agent of each side has a thickness of 2 μm to 15 μm. In some embodiments, the width of the first stiffening areas in the width direction is 0.2mm to 2mm and the thickness of the first stiffening agent per side is 2 μm to 10 μm. The actual size of the battery, the manufacturing process, etc. restrict the width and thickness of the first hardened region. Particularly, in the width direction, the size of the separator exceeding the edge of the positive electrode and the size of the negative electrode exceeding the edge of the positive electrode affect the width of the first hardened region, and in the process of actually producing and preparing the battery, the performance, the energy density and the like of the battery can be integrated, and various design parameters are controlled, so that the size of the separator exceeding the edge of the positive electrode and the size of the negative electrode exceeding the edge of the positive electrode are generally within the above-mentioned ranges.

In some embodiments, the first hardened zone of the at least two layers of release film is gathered toward the middle or inclined toward the same direction.

In some embodiments, in the width direction of the separator, the separator has a second region beyond the positive electrode tab, the first region and the second region are respectively located at two sides of the separator in the width direction, the second region includes a second non-hardened region overlapping with the projection of the negative electrode tab in the thickness direction of the separator, and a second hardened region beyond the edge of the negative electrode tab in the width direction and provided with a second hardening agent, and the hardness of the second hardened region is greater than that of the second non-hardened region. In some embodiments, the hardness of the second hardened region is 1.5H to 2.0H. In some embodiments, one or both sides of the second region of the release film include a second hardened region having a width in the width direction of 0.2mm to 2.5mm and a thickness of the second hardening agent of each side of 2 μm to 15 μm. In some embodiments, the first hardener and the second hardener each independently comprise a UV glue, siO ₂ With glue or Al ₂ O ₃ At least one of the mixture with glue.

The embodiment of the application also provides an electronic device comprising the electrochemical device.

According to the application, the first area exceeding the positive pole piece is arranged on the isolating film in the width direction of the isolating film, and comprises the first non-hardening area which is overlapped with the projection of the negative pole piece in the thickness direction of the isolating film, and the first hardening area exceeding the edge of the negative pole piece in the width direction and provided with the first hardening agent, so that the hardness of the first hardening area is more than 1.0H, and the hardness of the first non-hardening area is less than 1.0H, the impact resistance of the isolating film is enhanced, the electrolyte impact can be resisted, and the safety performance of the electrochemical device in falling is ensured.

Drawings

Fig. 1 to 5 illustrate schematic cross-sectional views of portions of electrochemical devices according to some embodiments of the present application.

Detailed Description

The following examples will enable those skilled in the art to more fully understand the present application and are not intended to limit the same in any way.

To improve the shrinkage problem of the separator, a winding glue scheme or a low liquid retention scheme is generally adopted. In the glue winding scheme, U-shaped gummed paper is pasted at the head and the tail of the electrode assembly, the width of the gummed paper is 5mm to 30mm, and the electrolyte is prevented from directly impacting the isolating film by bonding part of the isolating film, so that the shrinkage of the isolating film is improved. However, in the solution winding scheme, the requirements of electrolyte infiltration and limited rubberizing capability are considered, the rubberizing area of the head end face and the tail end face of the electrode assembly is less than or equal to 60 percent, the end face of a larger area is not rubberized, and the end face of the electrode assembly is easy to be impacted directly by the electrolyte and becomes a weak point. Under high liquid retention, the barrier film shrinks more severely. In the low-retention solution scheme, the content of free electrolyte in the electrode assembly is reduced, and the impact of the free electrolyte on the separator is reduced, so that the shrinkage of the separator is improved. However, an excessively low amount of the liquid retention may deteriorate the cycle performance of the electrochemical device.

An embodiment of the present application provides an electrochemical device, as shown in fig. 1, including a positive electrode tab 10, a negative electrode tab 11, and a separator 12. In some embodiments, separator 12 is disposed between positive electrode sheet 10 and negative electrode sheet 11. It should be understood that only a portion of positive electrode sheet 10, negative electrode sheet 11, and separator 12 are labeled in fig. 1 for simplicity. In some embodiments, in the width direction of the separator 12, the separator 12 has a first region 121 beyond the positive electrode tab 11, the first region 121 including a first non-hardened region 1211 that projectively overlaps the negative electrode tab 11 in the thickness direction of the separator 12, and a first hardened region 1212 that extends beyond the edge of the negative electrode tab 11 in the width direction and is provided with the first hardener 13. In some embodiments, the hardness of the first hardened region 1212 is greater than 1.0H and the hardness of the first non-hardened region 1211 is less than 1.0H.

In the embodiment, the region of the separator 12 overlapping with the projection of the negative electrode tab 11 refers to the region of the separator 12 covered with the negative electrode tab 11 or the region where the positive projection of the negative electrode tab 11 onto the separator 12 is located. In some embodiments, the hardener (e.g., the first hardener 13) may be sprayed using an electric spray gun or a spray can, or applied by a spreading machine, brush plate, blade knife coating, or spray coating, among others. The hardener may then be dried in the range of 30 ℃ to 130 ℃ or cured in combination with uv light, such that the hardener-coated release film is hardened. In some embodiments, a film durometer is used to measure the stiffness of the isolation diaphragm 12.

By making the hardness of the first hardened region 1212 greater than the hardness of the first non-hardened region 1211, specifically the hardness of the first hardened region 1212 greater than 1.0H, the hardness of the first non-hardened region 1211 is less than 1.0H, it is possible to improve the shrinkage of the separator 12 of the electrochemical device when dropped, and to enhance the safety performance of the electrochemical device.

In some embodiments, the first hardened region 1212 has a hardness of 1.5H to 2.0H. By increasing the hardness of the first hardened region 1212 of the separator 12, shrinkage of the separator when the electrochemical device is dropped can be improved.

In some embodiments, one or both sides of the first region 121 of the release film 12 include a first hardened zone 1212. Fig. 3 shows a case where both sides of the first region 121 include the first hardened region 1212. In some embodiments, the width w1 of the first hardened region 1212 in the width direction is 0.2mm to 2.5mm. If the width w1 is too small, the effect of the first hardened zone 1212 on improving the shrink of the release film is relatively limited; if the width w1 is too large, the energy density of the electrochemical device may be adversely affected. In some embodiments, the width w1 of the first hardened region 1212 in the width direction is 0.2mm to 2mm. In some embodiments, the width w1 of the first hardened zone 1212 in the width direction is 0.2mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, or other suitable value. In some embodiments, the thickness h1 of the first hardener 13 of each side is 2 to 15 μm. If the thickness h1 is too small, the effect of the first hardener 13 on improving shrinkage of the release film is relatively limited; if the thickness h1 is too large, the energy density of the electrochemical device may be adversely affected. In some embodiments, the thickness h1 of the first hardener 13 of each side is 2 μm to 10 μm. In some embodiments, the thickness h1 is 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, or other suitable values. In some embodiments, the width of the first hardened region 1212 may be measured by electron microscopy and the thickness of the first hardener 13 may be measured by ten-thousandth, the thickness of the first hardener 13 = total thickness-thickness of the release film, which would need to be divided by 2 if both sides of the release film were coated with the first hardener 13. It should be understood that in measuring the thickness of the first hardener 13, the measurement may be taken at a plurality of points and then averaged.

In some embodiments, the first hardened zone 1212 of the at least two layers of release film 12 gathers toward the middle or slopes toward the same direction. Fig. 4 shows a case where the first hardened zone 1212 of the separation film 12 of at least two layers is inclined toward the same direction. Fig. 5 shows the situation in which the first hardened zone 1212 of the at least two layers of release film 12 gathers towards the middle. After this shaping, on the one hand, the encapsulation of the electrochemical device is facilitated, and on the other hand, after shaping, the hardeners of the different layers are bonded in contact with each other, which can further improve the shrinkage of the separator when dropped. In some embodiments, the first hardener is applied while the spacer film 12 in the first region 121 is shaped by a shaping block, so that the spacer film 12 in the region is oriented, regularly gathered from the outer ring to the inner ring, and forms a V-shaped crossing state, or all faces in the same direction. In some embodiments, shaping may be performed before or after the corresponding hardener is dried.

In some embodiments, as shown in fig. 2, in the width direction of the separator 12, the separator 12 has a second region 122 beyond the positive electrode tab 10, and the first region 121 and the second region 122 are located on both sides of the separator 12 in the width direction, respectively. It should be appreciated that for simplicity, only portions of the first region 121 and the second region 122 are labeled in fig. 2. In some embodiments, the first region 121 and the second region 122 are edge regions of the release film 12 in the width direction. In some embodiments, the second region 122 includes a second non-hardened region 1221 that projectively overlaps the negative electrode tab 11 in the thickness direction of the separator 12, and a second hardened region 1222 that extends beyond the edge of the negative electrode tab 11 in the width direction and is provided with the second hardener 14. In some embodiments, when testing the hardness of the separator 12, the electrode assembly may be disassembled, and after the positive electrode tab 10 and the negative electrode tab 11 are peeled off, the respective areas (e.g., the first hardened region 1212, the first non-hardened region 1211, the second hardened region 1222, the second non-hardened region 1221) of the separator 12 are measured. In some embodiments, the hardness of the second hardened region 1222 is greater than the hardness of the second non-hardened region 1221. Also, by making the hardness of the second hardened region 1222 greater than that of the second non-hardened region 1221, shrinkage of the separator 12 when the electrochemical device is dropped can be improved, and safety performance of the electrochemical device can be improved.

In some embodiments, the hardness of the second hardened region 1222 is greater than 1.0H, while the hardness of the second non-hardened region 1221 is less than 1.0H. The second hardened region 1222 has a hardness of 1.5H to 2.0H. In some embodiments, one or both sides of the second region 122 of the release film 12 include a second hardened region 1222. Fig. 3 shows a case where both sides of the second region 122 include the second hardened region 1222.

In some embodiments, the width w2 of the second stiffening region 1222 in the width direction is 0.2mm to 2.5mm. If the width w2 is too small, the effect of the second hardened region 1222 to improve the shrinkage of the insulation film is relatively limited; if the width w2 is too large, the energy density of the electrochemical device may be adversely affected. In some embodiments, the width w2 of the second hardened region 1222 in the width direction is 0.2mm to 2mm. In some embodiments, the width w2 of the second stiffening region 1222 in the width direction is 0.2mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, or other suitable value. In some embodiments, the thickness h2 of the second hardener 14 of each side is 2 to 15 μm. If the thickness h2 is too small, the effect of the second hardener 14 to improve the shrinkage of the release film is relatively limited; if the thickness h2 is too large, the energy density of the electrochemical device may be adversely affected. In some embodiments, the thickness h2 of the second hardener 114 of each side is 2 μm to 10 μm. In some embodiments, the thickness h2 is 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, or other suitable value. The measurement of the width of the second hardening region 1222 and the thickness of the second hardening agent 14 may be performed in the same manner as the first hardening region 1212 and the first hardening agent 13, and will not be described again.

In some embodiments, the first hardener 13 and the second hardener 14 are both non-ester agents. Generally, the non-ester reagent is more resistant to the electrolyte, thereby ensuring stability of the first hardener 13 and the second hardener 14 from dissolution in the electrolyte. In some embodiments, the first hardener 13 and the second hardener 14 do not contain unsaturated functional groups, and the oxidation potential is higher, whereby the structural stability of the first hardener 13 and the second hardener 14 in the electrolyte can be further improved. In some embodiments, both the first hardener 13 and the second hardener 14 are resistant to electrolyte corrosion and insoluble in electrolyte, resistant to 4.8V high voltage and high temperature oxidative decomposition and aging at 110 ℃, and do not undergo swelling phenomenon, thereby being capable of maintaining hardness and adhesive effect. In some embodiments, the first hardener 13 and the second hardener 14 each independently comprise a UV glue, a SiO ₂ With glue or Al ₂ O ₃ At least one of the mixture with glue. In some embodiments, the first hardener 13 and the second hardener 14 may be any suitable hardener commercially available, such as, for example, commercially available UV glues, commercially available SiO-containing ₂ Or commercially available glue containing Al ₂ O ₃ These glues can each be used as a hardener to increase the stiffness of the corresponding areas of the barrier film 12. In some embodiments, for a coiled electrode assembly, the application of the corresponding hardener may be performed before or before coiling.

In some embodiments, the positive electrode tab 10 includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. In some embodiments, the positive electrode active material layer is provided on one or both sides of the positive electrode current collector. In some embodiments, the positive electrode active material layer includes a positive electrode active material. In some embodiments, the positive electrode active material includes at least one of lithium cobaltate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, or lithium manganate. In some embodiments, the positive electrode active material layer may further include a conductive agent. In some embodiments, the conductive agent in the positive electrode active material layer may include at least one of conductive carbon black, ketjen black, sheet graphite, graphene, carbon nanotubes, or carbon fibers. In some embodiments, the positive electrode active material layer may further include a binder, and the binder in the positive electrode active material layer may include at least one of carboxymethyl cellulose (CMC), polyacrylic acid, polyvinylpyrrolidone, polyaniline, polyimide, polyamideimide, polysiloxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin, or polyfluorene. In some embodiments, the mass ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode active material layer may be (80 to 99): (0.1-10): (0.1-10). In some embodiments, the thickness of the positive electrode active material layer may be 10 μm to 200 μm. It should be understood that the above is merely an example, and that any other suitable material, thickness, and mass ratio may be used for the positive electrode active material layer of the positive electrode.

In some embodiments, the positive current collector may be an Al foil, although other current collectors commonly used in the art may be used. In some embodiments, the thickness of the positive electrode current collector may be 1 μm to 100 μm. In some embodiments, the positive electrode active material layer may be coated on only a partial region of the current collector of the positive electrode.

In some embodiments, negative electrode tab 11 includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. In some embodiments, the anode active material layer is provided on one or both sides of the anode current collector. In some embodiments, the anode active material layer includes an anode active material, which may include at least one of graphite, hard carbon, silicon oxide, or silicone. In some embodiments, a conductive agent and a binder may be further included in the anode active material layer. In some embodiments, the conductive agent in the anode active material layer may include at least one of conductive carbon black, ketjen black, sheet graphite, graphene, carbon nanotubes, or carbon fibers. In some embodiments, the binder in the anode active material layer may include at least one of carboxymethyl cellulose (CMC), polyacrylic acid, polyvinylpyrrolidone, polyaniline, polyimide, polyamideimide, polysiloxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin, or polyfluorene. In some embodiments, the mass ratio of the anode active material, the conductive agent, and the binder in the anode active material layer may be (80 to 98): (0.1-10): (0.1-10). It should be appreciated that the above is merely an example, and that any other suitable materials and mass ratios may be employed. In some embodiments, the negative electrode current collector may employ at least one of a copper foil, a nickel foil, or a carbon-based current collector.

In some embodiments, the release film 12 comprises at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, the polyethylene includes at least one selected from high density polyethylene, low density polyethylene, or ultra high molecular weight polyethylene. In particular polyethylene and polypropylene, which have a good effect on preventing short circuits and can improve the stability of the battery through a shutdown effect. In some embodiments, the thickness of the release film is in the range of about 5 μm to 50 μm.

In some embodiments, the release film surface may further include a porous layer disposed on at least one surface of the substrate of the release film, the porous layer including inorganic particles selected from alumina (Al ₂ O ₃ ) Silicon oxide (SiO) ₂ ) Magnesium oxide (MgO), titanium oxide (TiO) ₂ ) Hafnium oxide (HfO) ₂ ) Tin oxide (SnO) ₂ ) Cerium oxide (CeO) ₂ ) Nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO) ₂ ) Yttria (Y) ₂ O ₃ ) At least one of silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. In some embodiments, the pores of the barrier film have a diameter in the range of about 0.01 μm to 1 μm. The binder of the porous layer is selected from polyvinylidene fluoride, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoroAt least one of propylene. The porous layer on the surface of the isolating film can improve the heat resistance, oxidation resistance and electrolyte infiltration performance of the isolating film, and enhance the cohesiveness between the isolating film and the pole piece.

In some embodiments of the present application, the electrode assembly of the electrochemical device is a rolled electrode assembly, a stacked electrode assembly, or a folded electrode assembly. In some embodiments, the positive electrode sheet and/or the negative electrode sheet of the electrochemical device may be a multi-layer structure formed by winding or stacking, or may be a single-layer structure in which a single-layer positive electrode sheet, a separator film, and a single-layer negative electrode sheet are stacked.

In some embodiments, the electrochemical device includes a lithium ion battery, but the present application is not limited thereto. In some embodiments, the electrochemical device may further include an electrolyte. The electrolyte may be one or more of a gel electrolyte, a solid electrolyte, and an electrolyte solution including a lithium salt and a nonaqueous solvent. The lithium salt is selected from LiPF ₆ 、LiBF ₄ 、LiAsF ₆ 、LiClO ₄ 、LiB(C ₆ H ₅ ) ₄ 、LiCH ₃ SO ₃ 、LiCF ₃ SO ₃ 、LiN(SO ₂ CF ₃ ) ₂ 、LiC(SO ₂ CF ₃ ) ₃ 、LiSiF ₆ One or more of LiBOB or lithium difluoroborate. For example, the lithium salt is LiPF ₆ Because it has high ionic conductivity and can improve cycle characteristics.

The nonaqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or a combination thereof.

The carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound, or a combination thereof.

Examples of chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), and combinations thereof. Examples of the cyclic carbonate compound are Ethylene Carbonate (EC), propylene Carbonate (PC), butylene Carbonate (BC), vinyl Ethylene Carbonate (VEC), or a combination thereof. Examples of the fluorocarbonate compound are fluoroethylene carbonate (FEC), 1, 2-difluoroethylene carbonate, 1, 2-trifluoroethylene carbonate, 1, 2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1, 2-difluoro-1-methylethylene carbonate, 1, 2-trifluoro-2-methylethylene carbonate, trifluoromethyl ethylene carbonate, or a combination thereof.

Examples of carboxylate compounds are methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, gamma-butyrolactone, decalactone, valerolactone, mevalonic acid lactone, caprolactone, methyl formate, or combinations thereof.

Examples of ether compounds are dibutyl ether, tetraglyme, diglyme, 1, 2-dimethoxyethane, 1, 2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, or combinations thereof.

Examples of other organic solvents are dimethyl sulfoxide, 1, 2-dioxolane, sulfolane, methyl sulfolane, 1, 3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphoric acid esters or combinations thereof.

In some embodiments of the present application, taking a lithium ion battery as an example, a positive electrode, a separator and a negative electrode are sequentially wound or stacked into an electrode member, and then the electrode member is packaged in an aluminum plastic film, for example, and then electrolyte is injected, formed and packaged to obtain the lithium ion battery. Then, performance test was performed on the prepared lithium ion battery.

Those skilled in the art will appreciate that the above-described methods of preparing an electrochemical device (e.g., a lithium ion battery) are merely examples. Other methods commonly used in the art may be employed without departing from the present disclosure.

Embodiments of the present application also provide an electronic device including the above electrochemical device. The electronic device of the embodiment of the present application is not particularly limited, and may be any electronic device known in the art. In some embodiments, the electronic device may include, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile machine, a portable copier, a portable printer, a headset, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini-compact disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable audio recorder, a radio, a backup power source, a motor, an automobile, a motorcycle, a power assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a household large-sized battery, a lithium ion capacitor, and the like.

The following examples and comparative examples are set forth to better illustrate the application, with lithium ion batteries being used as an example.

Example 1

Preparing a positive electrode plate: an aluminum layer is adopted as a positive electrode current collector, and a positive electrode active material lithium cobaltate, conductive carbon black of a conductive agent and polyvinylidene fluoride as a binder are mixed according to the weight ratio of 96:2.2:1.2 in an N-methylpyrrolidone (NMP) solution to form a positive electrode active material layer slurry, and coating the positive electrode active material layer slurry on a positive electrode current collector with a coating thickness of 80 μm to obtain a positive electrode active material layer. And then drying, cold pressing and cutting to obtain the positive electrode.

Preparing a negative electrode plate: artificial graphite, acetylene black, sodium carboxymethyl cellulose (CMC) and a binder styrene-butadiene rubber are mixed according to the weight ratio of 96:1:1.5:1.5 in deionized water to form a negative electrode slurry. And (3) adopting a copper foil with the thickness of 10 mu m as a negative current collector, coating the negative slurry on the negative current collector, wherein the coating thickness is 120 mu m, drying and cutting to obtain the negative electrode plate.

Preparation of a separation film: the base material of the isolating film is Polyethylene (PE) with the thickness of 8 mu m, two sides of the base material of the isolating film are respectively coated with 2 mu m alumina ceramic layers, and finally two sides coated with the ceramic layers are respectively coated with 2.5mg/cm ² Polyvinylidene fluoride (PVDF), oven dried.

Preparation of electrolyte: liPF is treated in an environment with a water content of less than 10ppm ₆ Adding non-additivesAqueous organic solvent (ethylene carbonate (EC): diethyl carbonate (DEC): propylene Carbonate (PC): propyl Propionate (PP): ethylene carbonate (VC) =20; 30;20;28;2, weight ratio), liPF ₆ The concentration of (2) is 1.15mol/L, and the electrolyte is obtained after uniform mixing.

Preparation of a lithium ion battery: sequentially stacking the positive pole piece, the isolating film and the negative pole piece, enabling the isolating film to be positioned between the positive pole piece and the negative pole piece to play a role of isolation, and winding to obtain the electrode assembly. Coating a hardening agent (Japanese Kogyo Co.) on both sides of the first and second regions of the separator to form a first hardening region and a second hardening region beyond the negative electrode sheet, wherein the hardening agent comprises SiO ₂ And glue. The first hard zone and the second hard zone had a width of 0.5mm, a thickness of 5 μm, and a hardness of 1.0H, respectively. The separator coated with the hardener is shaped in a V-shape (i.e., gathered toward the middle). And placing the electrode assembly in an aluminum plastic film, dehydrating at 80 ℃, injecting the electrolyte, packaging, and performing the technological processes of formation, degassing, trimming and the like to obtain the lithium ion battery. Wherein the length of the electrode assembly is 91mm, the width is 66mm, and the thickness is 61mm.

Comparative example 1

According to example 1, the difference is that: instead of coating the hardener, a conventional tape winding scheme is adopted, namely, after the electrode assembly is wound, 10mm tapes are attached to the head of the connecting tab, two 10mm tapes are attached to the tail of the other side, and then the two 10mm tapes are packaged in an aluminum plastic film.

Example 2

According to example 1, the difference is that: and coating a hardening agent on one side of the first area and the second area of the isolating film to form a first hardening area and a second hardening area which exceed the negative electrode plate. The first hard zone and the second hard zone had a width of 1.5mm, a thickness of 10 μm, and a hardness of 1.4H, respectively. The electrode assembly was 85mm in length, 63mm in width and 49mm in thickness.

Example 3

According to example 1, the difference is that: the first hard zone and the second hard zone had a width of 2.5mm, a thickness of 15 μm, and a hardness of 1.58H, respectively. The electrode assembly had a length of 90mm, a width of 63mm and a thickness of 48mm.

Examples 4 to 7

According to example 2, the difference is that: the first hardened region and the second hardened region have different hardness.

The test method of each parameter of the present application is described below.

The drop test method comprises the following steps:

1) Putting the lithium ion battery into a falling clamp of a corresponding model;

2) 1.5m 8 drops, 10 times per drop;

3) Leakage and ignition of the lithium ion battery are stopped and the lithium ion battery falls; before the drop, 24H voltage is measured and recorded; the voltage drop across the standard is: the voltage after dropping is 24H-the voltage before dropping is less than 30mV;

4) And disassembling the lithium ion battery, and counting the shrinkage ratio of the isolating film. In the embodiment of the application, in general, in the width direction of the isolation film, the width of the isolation film is larger than the width of the negative electrode plate and larger than the width of the positive electrode plate, if the isolation film is contracted to be within the positive electrode plate in the width direction after the lithium ion battery is disassembled, that is, the width of the isolation film is smaller than or equal to the width of the positive electrode plate at the moment, the lithium ion battery is considered as the lithium ion battery with contracted isolation film.

5) Counting the number of positions of diaphragm shrinkage: after the drop test is completed, several positions of all battery diaphragms, which are independent and discontinuous, are counted. The above test takes 20 samples for drop testing and then performs statistics.

Table 1 shows the respective parameters and evaluation results of examples 1 to 7 and comparative example 1.

TABLE 1

Compared with the conventional winding scheme, the method has the advantages that the isolation film is hardened by coating the hardening agent, so that the shrinkage of the isolation film can be basically and thoroughly inhibited, the voltage drop failure and the shrinkage of the battery diaphragm in the falling process are improved, the hardness of the isolation film is improved, and the safety performance of the lithium ion battery is remarkably improved. But the hardness of the diaphragm is too large, the performance of the battery can be influenced, if the hardness of the diaphragm is larger than 2.0H, the flexibility of the diaphragm is relatively poor, the diaphragm is relatively large in deformation when the battery is assembled, the edge is irregular, the wavy edge is caused, the electrolyte is not filled well, a lithium ion diffusion channel is easily disconnected, and the lithium separation is caused to be cyclically deteriorated, so that the significance of drop test is not great.

In addition, compared with the conventional winding scheme, the winding glue in the conventional winding scheme can be omitted by coating the hardening agent to harden the isolating film, so that the cost is effectively reduced, and the energy density of the lithium ion battery can be further improved after the winding glue is saved.

The above description is only illustrative of the preferred embodiments of the present application and of the principles of the technology employed. It should be understood by those skilled in the art that the scope of the disclosure of the present application is not limited to the specific combination of the above technical features, but also encompasses other technical features formed by any combination of the above technical features or their equivalents. Such as the technical proposal formed by the mutual replacement of the above characteristics and the technical characteristics with similar functions disclosed in the application.

Claims

1. An electrochemical device, comprising:

a positive electrode sheet;

a negative electrode plate;

the isolating film is arranged between the positive pole piece and the negative pole piece;

the separator is provided with a first area exceeding the positive electrode plate in the width direction of the separator, the first area comprises a first non-hardening area which is overlapped with the projection of the negative electrode plate in the thickness direction of the separator, and a first hardening area exceeding the edge of the negative electrode plate in the width direction and provided with a first hardening agent, the hardness of the first hardening area is greater than 1.0H, and the hardness of the first non-hardening area is less than 1.0H.

2. The electrochemical device of claim 1, wherein the hardness of the first hardened region is 1.5H to 2.0H.

3. The electrochemical device according to claim 1, wherein one or both sides of the first region include the first hardened region, a width of the first hardened region in the width direction is 0.2mm to 2.5mm, and a thickness of the first hardening agent per side is 2 μm to 15 μm.

4. An electrochemical device according to claim 3, wherein the width of said first hardened zone in said width direction is 0.2mm to 2mm, and the thickness of said first hardening agent on each side is 2 μm to 10 μm.

5. The electrochemical device of claim 1, wherein the first hardened regions of at least two layers of the separator film are gathered toward the middle or inclined toward the same direction.

6. The electrochemical device according to claim 1, wherein in a width direction of the separator, the separator has a second region beyond the positive electrode sheet, the first region and the second region being located on both sides of the separator in the width direction, respectively, the second region including a second non-hardened region overlapping with the projection of the negative electrode sheet in a thickness direction of the separator, and a second hardened region beyond an edge of the negative electrode sheet in the width direction and provided with a second hardening agent, the second hardened region having a hardness greater than that of the second non-hardened region.

7. The electrochemical device of claim 6, wherein the hardness of the second hardened region is 1.5H to 2.0H.

8. The electrochemical device according to claim 6, wherein one or both sides of the second region include the second hardened region, a width of the second hardened region in the width direction is 0.2mm to 2.5mm, and a thickness of the second hardening agent per side is 2 μm to 15 μm.

9. The electrochemical device of claim 8, wherein the first hardener and the second hardener each independently comprise UV glue, siO ₂ With glue or Al ₂ O ₃ At least one of the mixture with glue.

10. An electronic device characterized by comprising the electrochemical device according to any one of claims 1 to 9.