WO2023184180A1

WO2023184180A1 - Electrochemical apparatus and electronic apparatus

Info

Publication number: WO2023184180A1
Application number: PCT/CN2022/083831
Authority: WO
Inventors: 关文浩; 陈茂华; 谢远森; 鲁宇浩
Original assignee: 宁德新能源科技有限公司
Priority date: 2022-03-29
Filing date: 2022-03-29
Publication date: 2023-10-05
Also published as: CN117716527A

Abstract

An electrochemical apparatus (200) and an electronic apparatus. The electrochemical apparatus (200) comprises a negative electrode sheet (120), a positive electrode sheet (110) and a separator (130), the negative electrode sheet (120) comprising a dielectric layer (121), the dielectric layer (121) comprising a dielectric material, the separator (130) comprising a base membrane (131) and a functional coating (132), and the functional coating (132) comprising at least one of inorganic substances or of polymers. The arrangement of the dielectric layer (121) may macroscopically provide the surface of the negative electrode sheet (120) with positive charges, forcibly increases a surface potential at the negative electrode sheet (120), makes the surface potential at the negative electrode sheet (120) higher than a nucleation potential of metal cations, and inhibits the negative electrode sheet (120) from separating out metal cations. The functional coating (132) of the separator (130) comprises at least one of inorganic substances or of polymers, and the functional coating (132) may increase the retention amount of an electrolyte, facilitates the continuous intercalation and deintercalation of active metal cations at the positive electrode sheet (110) and the negative electrode sheet (120), and reduces the internal resistance of the electrochemical apparatus (200), thereby effectively reducing the metal cations separated out from the negative electrode sheet (120) and stabilizing the charging and discharging performance of the electrochemical apparatus (200).

Description

Electrochemical devices and electronic devices

Technical field

The present application relates to the field of electrochemistry, and in particular, to an electrochemical device and an electronic device.

Background technique

The fast charging performance of electrochemical devices is becoming more and more popular among users. As one of the main technical points to improve fast charging performance, the negative electrode plate of electrochemical devices plays an important role in the charge and discharge rate performance of electrochemical devices. Taking lithium-ion batteries as an example, during the fast charging process, a large number of lithium ions are quickly released from the positive electrode plate, pass through the isolation membrane through mass transfer through the electrolyte, and are embedded in the material of the negative electrode plate. However, when there are flaws in the design of the electrochemical device, When abnormal conditions such as changes in the structure of the electrochemical device occur, lithium ions from the positive electrode sheet may not be quickly embedded into the material of the negative electrode sheet, and lithium ions precipitate on the surface of the negative electrode sheet, resulting in severe capacity loss and even the risk of short circuit.

Contents of the invention

This application provides an electrochemical device and an electronic device that can solve the problem of metal cation precipitation in the electrochemical device and reduce the internal resistance during the cycle of the electrochemical device.

In a first aspect, the application provides an electrochemical device, including a negative electrode piece, a positive electrode piece, and an isolation film. The negative electrode piece includes a dielectric layer, the dielectric layer includes a dielectric material, and the isolation film It includes a base film and a functional coating, and the functional coating includes at least one of inorganic substances or polymers.

In some exemplary embodiments, when a pressure of 70N to 1000N is applied to both sides of the dielectric layer, the voltage difference on both sides of the dielectric layer ranges from 10mV to 100mV.

In some exemplary embodiments, the dielectric material includes at least one of a dielectric polymer material, a dielectric ceramic material, and a dielectric inorganic compound material.

In some exemplary embodiments, the dielectric polymer material includes a copolymer of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and trifluoroethylene, or a copolymer of polyvinylidene fluoride and tetrafluoroethylene having dielectric properties. At least one of a copolymer, an odd-numbered nylon-based dielectric polymer and an amorphous dielectric polymer, wherein the odd-numbered nylon-based dielectric polymer has a molecular formula of -(HN-(CH2) _x -CO-)n- , x is an even number, n is any positive integer;

The amorphous dielectric polymer includes vinylidene dicyanide/vinyl acetate copolymer, vinylidene dicyanide/vinyl benzoate copolymer, vinylidene dicyanide/vinyl propionate copolymer, vinylidene dicyanide/vinyl propionate copolymer, and vinylidene dicyanide/vinyl benzoate copolymer. /At least one of vinylene pivalate copolymer, vinylidene dicyanide/methyl methacrylate copolymer, and vinylidene dicyanide/isobutylene copolymer;

The dielectric ceramic material includes at least one of unitary dielectric ceramics, binary dielectric ceramics, and ternary dielectric ceramics with dielectric properties; the unitary dielectric ceramics include barium titanate, titanium At least one of lead acid, lithium niobate, and lithium tantalate; the binary system dielectric ceramic includes lead zirconate titanate; the ternary system dielectric ceramic includes lead zirconate titanate-lead magnesium niobate series ceramics , at least one of lead zirconate titanate-lead niobate zincate series ceramics, lead zirconate titanate-lead manganese antimonate series ceramics or ceramic substances represented by formula I;

Pb _1-x M _x (Zr _y Ti _1-y ) _1-(x/4) O _3Formula I

Where 0＜x＜1, 0＜y＜1, M is any one of Mg, Zn, Nb, Mn, Sb or rare earth elements;

The dielectric inorganic compound material includes at least one of metal oxides, nitrides, carbides, intermetallic compounds, and inorganic salts with dielectric properties.

In some exemplary embodiments, the dielectric layer has a thickness of 0.1 μm to 5 μm.

In some exemplary embodiments, the dielectric material has a coercive field strength greater than 0 kV/mm and less than or equal to 100 kV/mm at 25°C.

In some exemplary embodiments, the inorganic substance includes silicon dioxide, magnesium hydroxide, aluminum hydroxide, calcium titanate, barium titanate, lithium phosphate, zinc oxide, aluminum oxide, titanium oxide, magnesium oxide, At least one of hafnium oxide, tin oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, calcium oxide, lithium titanium phosphate, and lithium lanthanum titanate.

In some exemplary embodiments, the polymer includes at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene polymer, styrene-butadiene polymer, and polyacrylic acid.

In some exemplary embodiments, the mass content of the inorganic matter and/or the polymer is 10% to 90% based on the mass of the functional coating.

In some exemplary embodiments, the functional coating further includes a binder, and the mass content of the binder is 10% to 90% based on the mass of the functional coating.

In some exemplary embodiments, the electrochemical device satisfies one of the following conditions:

(a) The voltage difference ranges from 20mV to 80mV;

(b) The thickness of the dielectric layer is 0.1 μm to 3 μm;

(c) The dielectric material has a coercive field strength of 1 kV/mm to 60 kV/mm at 25°C.

In a second aspect, this application provides a method for preparing an electrochemical device, including:

The dielectric material is first coated on the surface of the negative electrode piece and polarized to obtain a dielectric layer; or,

The dielectric layer is first subjected to polarization treatment, and then the polarized dielectric layer is attached to the surface of the negative electrode piece to form a dielectric layer;

In some exemplary embodiments, the method of subjecting the dielectric material to the polarization treatment includes: placing the dielectric material in a parallel electric field to perform the polarization treatment, and the field strength range of the parallel electric field is 1 to 6 times the coercive field strength of the dielectric material at 25°C.

In some exemplary embodiments, when the dielectric material is coated on the surface of the negative electrode sheet, it also includes: mixing the dielectric material and the binding material, coating it on the surface of the negative electrode sheet and drying, The polarization treatment is then performed.

In a third aspect, the present application provides an electronic device, which is characterized in that it includes any one of the electrochemical device as described above and the electrochemical device obtained by using the preparation method as described above.

Based on the electrochemical device and electronic device of the present application, the electrochemical device includes a negative electrode piece, a positive electrode piece and an isolation film. By arranging the negative electrode piece including a dielectric layer, the surface of the negative electrode piece can be macroscopically charged with positive charge, forcing Increase the surface potential of the negative electrode piece so that its surface potential is higher than the nucleation potential of metal cations and inhibit the precipitation of metal cations from the negative electrode piece; the isolation film includes a base film and a functional coating, and the functional coating includes at least one of inorganic substances or polymers. It can increase the retention of electrolyte, facilitate the continuous insertion and extraction of active metal cations in the positive and negative electrodes, maintain better active ion transmission capabilities, reduce the internal resistance of the electrochemical device, thereby effectively reducing the precipitation of metal cations from the negative electrodes. and stabilizing the charge and discharge performance of electrochemical devices.

Description of drawings

In order to explain the embodiments of the present application or the technical solutions in the prior art more clearly, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only These are some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without exerting creative efforts.

Figure 1 is a partial cross-sectional view of an electrochemical device implemented in the present application;

Figure 2 is a cross-sectional view of one layer of functional coating on one side of the base film according to an implementation of the present application;

Figure 3 is a cross-sectional view of an implementation of the present application in which the number of functional coatings on one side of the base film is two layers;

Figure 4 is a cross-sectional view of an implementation of the present application when the number of single-sided functional coatings is one layer and is spaced apart from the negative electrode piece;

Figure 5 is a cross-sectional view of an implementation of the present application when the number of single-sided functional coatings is two layers and is spaced apart from the negative electrode piece.

Reference signs:

100. Battery core;

110. Positive electrode piece;

120. Negative electrode piece; 121. Dielectric layer; 122. Negative active material layer; 123. Negative current collector;

130. Isolation film; 131 base film; 132 functional coating;

200. Electrochemical device;

210. Outer packaging; 210a. Internal space.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present application more clear, the present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

As shown in Figure 1, the present application provides an electrochemical device 200, including a negative electrode piece 120, a positive electrode piece 110, and an isolation film 130. The isolation film 130 is disposed between the positive electrode piece 110 and the negative electrode piece 120. The positive electrode piece 110 and the negative electrode piece 120 are separated, and the isolation film 130 has ion insulation to prevent the positive electrode piece 110 and the negative electrode piece 120 from being short-circuited after contact. The negative electrode plate 120 includes a dielectric layer 121. The dielectric layer 121 includes a dielectric material. The isolation film 130 includes a base film 131 and a functional coating 132. As shown in FIGS. 2 and 3, the functional coating 132 includes inorganic substances or polymers. at least one of the things.

The dielectric layer 121 is provided between the isolation film 130 and the negative electrode piece 120 . As shown in Figures 2 and 4, and as shown in Figures 3 and 5, the dielectric layer 121 can be disposed on the surface of the negative electrode piece 120 and attached to or spaced apart from the isolation film 130; or, the dielectric layer 121 can be disposed on the surface of the negative electrode piece 120. The isolation film 130 faces the surface of the negative electrode piece and is attached to or spaced apart from the negative electrode piece.

The dielectric layer 121 includes a dielectric material having dielectric properties, so that the dielectric layer 121 has dielectric properties. There is a self-built electric field in the dielectric layer 121. The first side of the dielectric layer 121 facing the isolation film 130 is negatively charged, and the second side of the dielectric layer 121 facing the negative electrode plate 120 is positively charged. When the dielectric layer 121 is positively charged, The second side of the charge is in contact with the surface of the negative electrode piece 120, which can macroscopically make the surface of the negative electrode piece 120 positively charged, forcibly increasing the surface potential of the negative electrode piece 120, so that the surface potential of the negative electrode piece 120 is higher than the nucleation potential of metal cations , inhibiting the precipitation of metal cations on the negative electrode piece 120. When the metal cations reach the surface of the dielectric layer 121, the self-built electric field inside the dielectric layer 121 can provide negative feedback to the local concentrated metal cation flow, weaken the local large current, and uniformize the surface current density of the negative electrode plate 120 in advance. , inhibiting the local precipitation of metal cations.

In some exemplary embodiments, when a pressure of 70N to 1000N is applied to both sides of the dielectric layer 121, the voltage difference on both sides of the dielectric layer 121 ranges from 10mV to 100mV. When the dielectric layer 121 meets the above conditions, It indicates that the dielectric layer 121 can be polarized, that is, after the polarization treatment, a built-in electric field can be formed inside the dielectric layer 121 .

In some exemplary embodiments, the dielectric material has a coercive field strength greater than 0 kV/mm and less than or equal to 100 kV/mm at 25°C. By selecting a dielectric material that has a dielectric effect and satisfies the above-mentioned coercive field strength range, and after the dielectric material is polarized, a built-in electric field that can uniformize the surface current of the negative electrode plate 120 can be formed in the dielectric layer 121 . Preferably, the dielectric material has a coercive field strength of 1 kV/mm to 60 kV/mm at 25°C.

In some exemplary embodiments, the dielectric polymer material includes a copolymer of polyvinylidene fluoride having dielectric properties, a copolymer of polyvinylidene fluoride and trifluoroethylene having dielectric properties, a copolymer of polyvinylidene fluoride having dielectric properties, At least one of a copolymer of polyvinylidene fluoride and tetrafluoroethylene, an odd-numbered nylon-based dielectric polymer with dielectric properties, and an amorphous dielectric polymer with dielectric properties, wherein the odd-numbered nylon-based dielectric polymer The molecular formula of the polymer is -(HN-(CH2) _x -CO-)n-, x is an even number, and n is any positive integer.

Amorphous dielectric polymers include vinylidene dicyanide/vinyl acetate copolymer, vinylidene dicyanide/vinyl benzoate copolymer, vinylidene dicyanide/vinyl propionate copolymer, vinylidene dicyanide/new At least one of vinylidene dicyanide/methyl methacrylate copolymer, vinylidene dicyanide/isobutylene copolymer.

In some exemplary embodiments, the dielectric ceramic material includes at least one of a unitary dielectric ceramic, a binary dielectric ceramic, and a ternary dielectric ceramic having dielectric properties; the unitary dielectric ceramic includes At least one of barium titanate, lead titanate, lithium niobate, and lithium tantalate; the binary dielectric ceramic includes lead zirconate titanate (PbZr _x Ti _1-x O ₃ , where 0＜x＜1); Ternary dielectric ceramics include lead _zirconate titanate-lead magnesium niobate series ceramics (PbMg _x Nb _1-x O ₃ , where 0 < Nb _1-x O ₃ , where 0＜x＜1), lead zirconate titanate-lead manganese antimonate series ceramics (PbMn _x Sb _1-x O ₃ , where 0＜x＜1) or ceramic material represented by formula I at least one of them.

Pb _1-x M _x (Zr _y Ti _1-y ) _1-(x/4) O _3Formula I

Among them, 0<x<1, 0<y<1, and M is any one of Mg, Zn, Nb, Mn, Sb or rare earth elements.

In some exemplary embodiments, the molecular formula of the lead titanium zirconate may be PbZr _0.6 Ti _0.4 O ₃ .

In some exemplary embodiments, the thickness of the dielectric layer 121 is 0.1 μm to 5 μm. For example, the thickness of the dielectric layer 121 may be 0.1 μm, 1 μm, 3 μm, 4 μm, or 5 μm. If the thickness of the dielectric layer 121 is too thin, it is difficult to form an effective built-in electric field in the dielectric layer 121 to uniform the current on the surface of the negative electrode plate 120; when the thickness of the dielectric layer 121 is greater than 0.1 μm, the thickness of the dielectric layer 121 is too thick. It is difficult for metal cations to penetrate the dielectric layer 121 and migrate into the negative electrode piece 120. At the same time, if the dielectric layer 121 is too thick, it will occupy more internal space 210a of the electrochemical device 200, resulting in an increase in the proportion of inactive substances in the electrochemical device 200. big. In addition, if the dielectric layer 121 is too thick or too thin, it is not conducive to the bending process of the dielectric layer 121 along with the negative electrode piece 120 or the isolation film 130, and limits the application of the dielectric layer 121 in the electrochemical device 200. Preferably, the thickness of the dielectric layer 121 is 0.1 μm to 3 μm.

In some exemplary embodiments, the dielectric layer 121 further includes an adhesive material, and the weight ratio of the dielectric material to the adhesive material is 0.05˜0.5:1. The binding material includes at least one of N-methylpyrrolidone or glycerin.

The positive electrode sheet 110 includes a positive current collector and a positive active material layer, and the positive active material layer is disposed on at least one surface of the positive current collector. The negative electrode sheet 120 includes a negative electrode current collector 123 and a negative electrode active material layer 122 . The negative electrode active material layer 122 is disposed on at least one surface of the negative electrode current collector 123 . The negative active material layer 122 has pores to form spaces where metal cations are embedded. When the dielectric layer 121 is disposed on the surface of the negative electrode piece 120, the negative active material layer 122 is connected to the dielectric layer 121.

The negative electrode sheet 120 of the present application is not particularly limited. The negative active material layer 122 can be any negative active material layer 122 in the prior art. The negative active material layer 122 includes negative active materials. The negative active materials include natural graphite, artificial graphite, hard graphite, etc. At least one of carbon, soft carbon, silicon, silicon carbon or silicon oxide; the negative electrode current collector 123 can be any negative electrode current collector 123 known in the art, such as copper foil, aluminum foil, aluminum alloy foil or composite current collector, etc. .

The isolation film 130 of the present application includes a base film 131 and a functional coating 132. The functional coating 132 includes at least one of inorganic substances or polymers. The functional coating 132 is provided on at least one surface of the base film 131 . By providing a coating on the base film 131, the porosity of the isolation film can be increased, the amount of electrolyte retained can be increased, which is conducive to the continuous insertion and extraction of active metal cations in the positive and negative electrodes, maintaining better active ion transmission capabilities, and reducing electrochemical The internal resistance of the device 200 can further improve the internal resistance of the device 200 and prevent active metal cations from forming dendrites and puncturing the isolation film 130 to cause battery short circuit, thereby effectively reducing the precipitation of metal cations from the negative electrode plate 120 and stabilizing the charge and discharge performance of the electrochemical device 200 . Safety performance of electrochemical device 200.

In some exemplary embodiments, the base film 131 includes at least one of the following polymers: polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyphenylene. Phenyldiamide, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole , polyethersulfone, polyphenylene ether, polymer film formed of cyclic olefin copolymer, multi-layer polymer film, or non-woven fabric.

In some exemplary embodiments, the inorganics in the functional coating 132 include silicon dioxide, magnesium hydroxide, aluminum hydroxide, calcium titanate, barium titanate, lithium phosphate, zinc oxide, aluminum oxide, titanium oxide, At least one of magnesium oxide, hafnium dioxide, tin oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, calcium oxide, lithium titanium phosphate, and lithium lanthanum titanate. Based on the quality of the functional coating, the mass content of inorganic substances is 10%-90%.

In some exemplary embodiments, the polymer in the functional coating 132 includes at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene polymer, styrene-butadiene polymer, and polyacrylic acid. Based on the quality of the functional coating, the mass content of the polymer is 10%-90%.

In some exemplary embodiments, the functional coating 132 further includes a binder, including polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyacrylonitrile, polyacrylate, Vinyl pyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan , cyanoethylpolyvinyl alcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, sodium carboxymethylcellulose, lithium carboxymethylcellulose, acrylonitrile-styrene-butadiene At least one of copolymer, polyvinyl alcohol, polyvinyl ether, ethyl acetate, styrene polyvinyl ether, ethylene carbonate, glyceryl ether, propylene carbonate, polyvinylidene fluoride, and styrene-acrylic emulsion. Based on the quality of the functional coating, the mass content of the binder is 10-90%.

When the dielectric layer 121 is disposed on the surface of the negative electrode active material layer 122 or the surface of the isolation film 130, the dielectric material in the dielectric layer 121 can be stably connected to the negative electrode active material layer 122 and the isolation film 130 and is not easily peeled off.

The thickness direction X of the negative electrode piece 120 is the same as the thickness direction of the dielectric layer 121 . In the thickness direction

The isolation film 130 is disposed between the positive electrode piece 110 and the negative electrode piece 120 . The negative electrode piece 120 , the isolation film 130 and the positive electrode piece 110 can be stacked or wound in sequence along the thickness direction X of the negative electrode piece 120 .

The positive electrode sheet 110 of this application is not particularly limited. The positive active material layer includes positive active materials. The positive active materials include nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum materials, lithium iron phosphate, lithium cobalt oxide, lithium manganate, and manganese phosphate. At least one of lithium iron or lithium titanate; the positive electrode current collector can be any positive electrode current collector known in the art, such as aluminum foil, aluminum alloy foil or composite current collector, etc., and the positive electrode active material layer can be any positive electrode in the prior art. Active material layer.

The electrochemical device 200 also includes an outer package 210 and an electrolyte. The electrolyte, the positive electrode piece 110 , the negative electrode piece 120 and the isolation film 130 are provided in the inner space 210 a of the outer package 210 . The outer packaging 210 in this application is not particularly limited, and any well-known outer packaging 210 in the art can be used. For example, it can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.; it can also be a soft bag, such as a bag-type soft bag. , the material of the soft bag can be aluminum plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS). The electrochemical device 200 further includes a positive electrode tab and a negative electrode tab. The positive electrode tab is electrically connected to the positive current collector, and the negative electrode tab is electrically connected to the negative current collector. The positive electrode tab and the negative electrode tab are used to electrically connect with an external circuit to charge and discharge the electrochemical device 200 and to monitor the internal working status of the electrochemical device 200 .

There is no particular limitation on the electrolyte solution in this application. Any electrolyte solution known in the art can be used. The electrolyte solution can be in any of gel state, solid state and liquid state. When the electrolyte is a liquid electrolyte, the liquid electrolyte includes a lithium salt and a non-aqueous solvent. The lithium salt is not particularly limited. Any lithium salt known in the art can be used as long as the purpose of the present application can be achieved. For example, the lithium salt can include LiTFSI, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiB(C ₆ At least one of H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiN(SO ₂ CF ₃ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , LiPO ₂ F _2, etc. The non-aqueous solvent is not particularly limited as long as it can achieve the purpose of the present application. For example, the non-aqueous solvent may include at least one of carbonate compounds, carboxylate compounds, ether compounds, nitrile compounds or other organic solvents, carbonic acid The ester compound may include diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC) ), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), 1,2-carbonate Difluoroethylene, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoroethylene carbonate 2-Methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methyl carbonate At least one of ethylene carbonate or trifluoromethylethylene carbonate.

The electrochemical device 200 is not particularly limited in this application, and may include, but is not limited to, lithium-ion batteries or sodium-ion batteries.

The present application also provides a method for preparing the electrochemical device 200, which is used to prepare the electrochemical device 200 as described above. Preparation methods include:

The dielectric material is first coated on at least one surface of the isolation film 130 or the negative active material layer, and the dielectric material is polarized to form the dielectric layer 121; or, the dielectric material is polarized first, and then the dielectric material is polarized. The polarized dielectric material is attached to at least one surface of the isolation film 130 or the negative active material layer 122 to form the dielectric layer 121 . The first side of the dielectric layer 121 facing the isolation film 130 is negatively charged, and the second side facing the negative active material layer 122 is positively charged.

In some exemplary embodiments, a method for polarizing a dielectric material includes: placing the dielectric material in a parallel electric field for polarization. The field strength range of the parallel electric field is that of the dielectric material at 25°C. 1 to 6 times the coercive field strength. The time range for placing the dielectric material in a parallel electric field for polarization treatment can be 30 minutes.

The dielectric material can be disposed on at least one surface of the separator 130 or the negative active material layer 122 in an amorphous state or a shaped state, where the amorphous state includes powder or slurry, and the shaped state includes a thin film. , flakes, etc. For example, some of the above-mentioned dielectric polymer materials and dielectric inorganic compounds can be made into thin films, laminated on at least one surface of the separator 130 or the negative active material layer 122 and subjected to polarization treatment; the above-mentioned dielectric polymer materials and dielectric Some of the electroceramic materials can be in powder form and mixed with the binding material, coated on the surface of the isolation film 130 or the negative active material layer 122 and dried, and then subjected to polarization treatment.

After the dielectric material is processed into a shaped state to form the dielectric layer 121, and then placed on the surface of the isolation film 130 or the negative electrode sheet 120, the dielectric layer 121 can be bonded to the surface of the isolation film 130 or the negative electrode active material layer 122. , or, after the dielectric layer 121 is initially connected to the surface of the isolation film 130 or the negative active material layer 122, during the subsequent processing of the electrochemical device 200, for example, in the formation step of the electrochemical device 200, pressure is applied to the medium. At least one of the electrical layer 121 and the heat treatment of the dielectric layer 121 is used to fix the dielectric layer 121 to the isolation film 130 or the negative active material layer 122 .

After the dielectric layer 121 is disposed on the surface of the isolation film 130 or the negative electrode piece 120, the isolation film 130 and the negative electrode piece 120 are laminated so that the dielectric layer 121 is disposed between the isolation film 130 and the negative electrode piece 120, and the positive electrode is The electrode piece 110 is disposed on the side of the isolation film 130 away from the negative electrode piece 120. After repeated stacking, a laminated battery core 100 is obtained, or the stacked positive electrode piece 110, isolation film 130, dielectric layer 121 and negative electrode are obtained. The pole pieces 120 are wound and arranged to obtain the wound battery core 100.

The present application also provides an electronic device, including the electrochemical device 200 as described above. For example, the electronic device may include a car, a mobile phone, an electric motorcycle, etc.

Taking the electrochemical device 200 as a lithium-ion battery as an example, the present application will be described in further detail below with reference to specific embodiments.

Example 1

Preparation of positive electrode piece 110:

Mix the ternary cathode active material (LiNi _0.8 Co _0.1 Mn _0.1 O ₂ ), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) in a weight ratio of 97.5:1.0:1.5, and add N-methylpyrrolidone ( NMP) as the solvent, prepare a slurry with a solid content of 0.75, and stir evenly. The slurry is evenly coated on the positive electrode current collector aluminum foil, and dried at 90°C to obtain a single-sided coated positive electrode sheet 110 with a coating thickness of 70 μm. The single-sided coated positive electrode sheet 110 is cut into (38mm×58mm) specifications are available for use.

Preparation of negative electrode piece 120:

Mix artificial graphite, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) at a weight ratio of 97:1.0:2.0, add N-methylpyrrolidone (NMP) as a solvent, and prepare a slurry with a solid content of 0.8 ingredients and stir evenly. The slurry is evenly coated on the two opposite surfaces of the copper foil of the negative electrode current collector 123, and dried at 80°C to obtain a negative electrode sheet 120 coated with a negative active material layer 122 on both sides, in which the negative active material is on one side. The layer thickness is 100 μm;

Lead titanium zirconate (PbZr _0.6 Ti _0.4 O ₃ ) powder. Powdered lead zirconate titanate (PbZr _0.6 Ti _0.4 O ₃ ) is used as the dielectric material and N-methylpyrrolidone (NMP) is used as the binding material. The powdered PbZr0.6Ti0.4O3 dielectric material is coercive at 25°C. The field strength is 0.7KV/mm. Powdered PbZr _0.6 Ti _0.4 O ₃ is dispersed in N-methylpyrrolidone (NMP), and the PVDF is dispersed evenly by stirring to obtain a dielectric slurry, in which PbZr _0.6 Ti _0.4 O ₃ The weight ratio to NMP is 0.12, that is, the solid content of the dielectric slurry is 12%.

Use a scraper to evenly apply the dielectric slurry on the two opposite surfaces of the negative electrode piece 120 prepared above, and place it in a vacuum drying oven to dry at 80° C. to obtain the negative electrode piece 120 with dielectric material attached to both sides. After drying, the thickness of the dielectric material attached to one side of the negative active material layer 122 is 0.1 μm.

Then, the negative electrode piece 120 with dielectric material on both sides is placed in the parallel electric field of the polarization device for polarization. The polarization device includes a positive pressure plate and a negative pressure plate for generating a parallel electric field, between the positive pressure plate and the negative pressure plate. The direction of the parallel electric field is from the positive pressure plate to the negative pressure plate. Place the dielectric material on one side of the negative electrode piece 120 against the positive pressure plate of the polarization device. The parallel electric field strength is 3kV/mm and the polarization time is 30 minutes. Then flip it over. For the negative electrode piece 120, place the dielectric material on the other side of the negative electrode piece 120 against the positive plate of the polarization device. The polarization time is 30 minutes. After the polarization is completed, the two opposite sides of the negative electrode piece 120 are obtained. The dielectric layer 121 formed of PbZr _0.6 Ti _0.4 O ₃ and NMP is used. The negative electrode piece 120 with the dielectric layer 121 on both sides is cut into (40mm×60mm) specifications for use.

In the thickness direction of the dielectric layer 121 , the dielectric layer 121 has a first side facing the negative electrode piece 120 and a second side away from the negative electrode piece 120 . The positive probe of the voltmeter is in contact with the first side of the dielectric layer 121, the negative probe is in contact with the second side of the dielectric layer 121, and a pressure of 100N is applied to the dielectric layer 121 in the thickness direction of the dielectric layer 121. , the measured voltage reading is 17mV.

Preparation of electrolyte:

In a dry argon atmosphere, mix dioxolane (DOL) and dimethyl ether (DME) at a volume ratio of 1:1 to obtain an organic solvent. Add the lithium salt LiTFSI to the organic solvent to dissolve and mix evenly to obtain The concentration of lithium salt is 1M in the electrolyte.

Preparation of isolation film 130:

A polyethylene film (PE) with a thickness of 15 μm is selected as the base film 131, and an inorganic coating is coated on one side of the isolation film 130. The preparation method of the inorganic coating includes: uniformly mixing 30 parts of silica powder, 10 parts of polyvinyl pyrrolidone and 60 parts of polyacrylic acid solvent according to the weight ratio to obtain an inorganic coating slurry, and mixing the inorganic coating slurry. The coating slurry is coated on one surface of the PE base film 131 by dip coating, and dried at 55°C to obtain an inorganic coating. The thickness of the inorganic coating on one side of the base film 131 is 4 μm. Cut the prepared isolation film 130 into specifications of (42mm×62mm) for use.

Preparation of lithium-ion batteries:

The above-mentioned cut negative electrode sheet 120 with dielectric layer 121 on both sides is placed in the middle, and the cut positive electrode sheet 110 is placed on both sides of the negative electrode sheet 120 opposite in the thickness direction X, and between each positive electrode sheet 110 and A polyethylene (PE) isolation film 130 with a thickness of 15 μm is arranged between the negative electrode sheets 120. The negative electrode sheet 120 with a dielectric layer 121 on both sides, the two layers of positive electrode sheets 110 and the two layers of isolation films 130 are arranged along the thickness direction X of the negative electrode sheet 120. Stacked with the inorganic coating side of the separator 130 facing the positive electrode plate. After fixing the four corners of the stacked negative electrode sheet 120, positive electrode sheet 110 and isolation film 130 with tape, place it into the internal space 210a of the aluminum-plastic film outer package 210, and move it toward the inside of the outer package 210 through the opening of the outer package 210. After the electrolyte is injected into the space 210a, the opening of the outer package 210 is sealed to obtain a laminated lithium-ion battery, in which a three-electrode test is performed on the cell 100 and the lowest potential of the negative electrode piece 120 is 28 mV.

Example 2

The differences from Example 1 are:

Preparation of isolation film 130:

A polyethylene film (PE) with a thickness of 15 μm is selected as the base film 131, and an inorganic coating and an organic coating are sequentially laminated and coated on the two opposite sides of the base film 131. Preparation of inorganic coating: Mix 30 parts by weight of silica powder, 10 parts by weight of polyvinyl pyrrolidone and 60 parts by weight of polyacrylic acid solvent to obtain an inorganic coating slurry. The PE base film 131 is surface-coated by dip coating to form a single-sided coating. The inorganic coating slurry is dried at 55°C to obtain an inorganic coating. The thickness of each inorganic coating is 4 μm. Preparation of organic coating: Mix 5 parts by weight of styrene-butadiene polymer powder, 40 parts by weight of polyacrylate and 55 parts by weight of ethyl acetate evenly to obtain an organic coating slurry. The slurry is double-sided coated on the PE base film surface-treated with the inorganic coating using gravure coating. The organic coating slurry is dried at 55°C to obtain an organic coating. The thickness of each organic coating is 4 μm. The side of the separator 130 containing the inorganic coating faces the positive electrode piece.

Preparation of dielectric layer 121:

The thickness of the dielectric layer 121 provided on the surface of the negative active material layer is 0.1 μm;

In the thickness direction of the dielectric layer 121 , the dielectric layer 121 has a first side facing the negative electrode piece 120 and a second side away from the negative electrode piece 120 . The positive probe of the voltmeter is in contact with the first side of the dielectric layer 121, the negative probe is in contact with the second side of the dielectric layer 121, and a pressure of 100N is applied to the dielectric layer 121 in the thickness direction of the dielectric layer 121. , the measured voltage reading is 15mV.

Among them, the lowest potential of the negative electrode piece 120 is 28mV when performing a three-electrode test on the battery core 100 .

Example 3

The differences from Example 1 are:

The thickness of the dielectric layer 121 provided on the surface of the negative active material layer is 3 μm;

In the thickness direction of the dielectric layer 121 , the dielectric layer 121 has a first side facing the negative electrode piece 120 and a second side away from the negative electrode piece 120 . The positive probe of the voltmeter is in contact with the first side of the dielectric layer 121, the negative probe is in contact with the second side of the dielectric layer 121, and a pressure of 100N is applied to the dielectric layer 121 in the thickness direction of the dielectric layer 121. , the measured voltage reading is 14mV.

Among them, the lowest potential of the negative electrode piece 120 is 29mV when performing a three-electrode test on the battery core 100 .

Example 4

The differences from Example 1 are:

The thickness of the dielectric layer 121 provided on the surface of the negative active material layer 122 is 5 μm;

In the thickness direction of the dielectric layer 121 , the dielectric layer 121 has a first side facing the negative electrode piece 120 and a second side away from the negative electrode piece 120 . The positive probe of the voltmeter is in contact with the first side of the dielectric layer 121, the negative probe is in contact with the second side of the dielectric layer 121, and a pressure of 100N is applied to the dielectric layer 121 in the thickness direction of the dielectric layer 121. , the measured voltage reading is 13mV.

Among them, the lowest potential of the negative electrode piece 120 is 30mV when performing three-electrode detection on the battery core 100 .

Example 5

The differences from Example 1 are:

Preparation of isolation film 130:

A polyethylene film (PE) with a thickness of 15 μm is selected as the base film 131, and an inorganic coating and an organic coating are sequentially laminated and coated on the two opposite sides of the base film 131. Preparation of inorganic coating: Mix 30 parts by weight of silica powder, 10 parts by weight of polyvinyl pyrrolidone and 60 parts by weight of polyacrylic acid solvent to obtain an inorganic coating slurry. The PE base film 131 is surface-coated by dip coating to form a single-sided coating. The inorganic coating slurry is dried at 55°C to obtain an inorganic coating. The thickness of each inorganic coating is 4 μm. Preparation of organic coating: Mix 5 parts by weight of styrene-butadiene polymer powder, 40 parts by weight of polyacrylate and 55 parts by weight of ethyl acetate evenly to obtain an organic coating slurry. The slurry is double-sided coated on the PE base film surface-treated with the inorganic coating using gravure coating. The organic coating slurry is dried at 55°C to obtain an organic coating. The thickness of each organic coating is 4 μm. The side of the isolation film 130 containing the inorganic coating faces the positive electrode piece

Preparation of negative electrode piece 120:

In this embodiment, the dielectric layer 121 of the negative electrode plate 120 is coated on the surface of the isolation film 130, that is, the dielectric layer 121 is provided on the surface of the organic coating, that is, the dielectric layer is located on the PE base film side that does not contain the inorganic coating. Organic coated surface.

Specifically, artificial graphite, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed according to a weight ratio of 97:1.0:2.0, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a solid content of 0.8 slurry and stir evenly. The slurry is evenly coated on the two opposite surfaces of the copper foil of the negative electrode current collector 123, and dried at 80°C to obtain a double-sided coated negative electrode piece 120, in which the coating thickness on one side is 100 μm. The double-sided coated negative electrode sheet 120 is cut into a specification of (40mm×60mm) for use.

Preparation of the dielectric layer 121: Provide powdered lead zirconate titanate (PbZr _0.6 Ti _0.4 O ₃ ) as a dielectric material, N-methylpyrrolidone (NMP) as a binding material, and powdered PbZr _0.6 Ti _0.4 O ₃ The coercive field strength of the dielectric material is 0.7KV/mm at 25°C. Disperse the powdered PbZr _0.6 Ti _0.4 O ₃ in N-methylpyrrolidone and stir to make the PVDF disperse evenly to obtain a dielectric slurry, in which PbZr The weight ratio of _0.6 Ti _0.4 O ₃ to NMP is 0.12, that is, the solid content of the dielectric slurry is 12%.

Use a scraper to evenly apply the dielectric slurry on the organic coating surface of the isolation film 130, and place it in a vacuum drying oven to dry at 80° C. to obtain an isolation film 130 with dielectric material attached to the surface. After drying, the thickness of the dielectric material attached to the surface of the isolation film 130 is 1 μm (that is, the thickness of the dielectric layer 121 subsequently obtained is 1 μm).

The isolation film 130 with the dielectric material attached to the surface is placed in a parallel electric field of a polarization device for polarization. The polarization device includes a positive pressure plate and a negative pressure plate for generating a parallel electric field, and a parallel electric field between the positive pressure plate and the negative pressure plate. The direction is from the positive pressure plate to the negative pressure plate. The dielectric material is placed against the negative pressure plate. The parallel electric field strength is 3kV/mm and the polarization time is 30 minutes. After the polarization is completed, PbZr _0.6 Ti _0.4 O ₃ and NMP form an isolation film. 130 surface dielectric layer 121, the isolation film 130 including the dielectric layer 121 is cut into (42mm×62mm) specifications for use.

The positive probe of the voltmeter is in contact with the first side of the dielectric layer 121 facing away from the organic coating in the isolation film 130, and the negative probe is in contact with the other side of the dielectric layer 121 facing the organic coating in the isolation film 130. The dielectric layer 121 exerts a pressure of 100 N perpendicular to the thickness direction of the dielectric layer 121, and the measured voltage is 15 mV.

Preparation of lithium-ion batteries:

The above-mentioned cut negative electrode piece 120 is placed in the middle, and the above-mentioned cut positive electrode piece 110 is placed on both sides opposite to the thickness direction X of the negative electrode piece 120, and between each positive electrode piece 110 and negative electrode piece 120 The above-mentioned isolation film 130 with the dielectric layer 140 attached is arranged in between, with the dielectric layer 121 facing the negative electrode piece 120, and the positive electrode piece 110 facing the organic coating side of the isolation film 130. The negative electrode piece 120 and the two layers of positive electrode are stacked. The pole piece 110 and two layers of isolation film 130 with dielectric layer 121 attached are stacked along the thickness direction Finally, the negative electrode piece 120 is electrically connected to the negative electrode lug, and the positive electrode piece 110 is electrically connected to the positive electrode lug to obtain the battery core 100. The battery core 100 is placed in the aluminum-plastic film outer package 210, and is inserted into the outer package 210 through the opening of the outer package 210. After the electrolyte is injected into the inner space 210a of the outer package 210, the opening of the outer package 210 is sealed to obtain a lithium ion battery. Among them, the lowest potential of the negative electrode piece 120 is 28mV when performing a three-electrode test on the battery core 100 .

Example 6

The differences from Example 2 are:

Powdered lead zirconate titanate (PbZr _0.6 Ti _0.4 O ₃ ) is replaced with powdered polyvinylidene fluoride (PVDF) as the dielectric material. The coercive field strength of the powdered PVDF dielectric material at 25°C is 50KV/ mm, where, during the process of preparing the dielectric layer 121, the parallel electric field strength when polarizing the dielectric material is 100kV/mm;

Preparation of the isolation film 130: A polyethylene film (PE) with a thickness of 15 μm is selected as the base film 131, and organic coatings are coated on both sides of the isolation film 130. Preparation of organic coating: 5 parts by weight of styrene-butadiene polymer powder, 40 parts by weight of polyacrylate and 55 parts by weight of ethyl acetate are mixed evenly to obtain an organic coating slurry, and the organic coating slurry is The material is double-sided coated on the surface of the PE base film 131 by dip coating, and the organic coating slurry is dried at 55°C to obtain an organic coating. The thickness of each organic coating is 4 μm.

Among them, the lowest potential of the negative electrode piece 120 is 26.5mV when performing a three-electrode test on the battery core 100 .

Example 7

The differences from Example 2 are:

Lead zirconate titanate (PbZr _0.6 Ti _0.4 O ₃ ) is replaced with nylon 7 as the dielectric material. The coercive field strength of the nylon 7 dielectric material is 97KV/mm at 25°C. In the process of preparing the dielectric layer 121, the parallel electric field strength when polarizing the dielectric material is 280kV/mm, and the thickness of the dielectric layer 121 is 5 μm;

In the thickness direction of the dielectric layer 121 , the dielectric layer 121 has a first side facing the negative electrode piece 120 and a second side away from the negative electrode piece 120 . The positive probe of the voltmeter is in contact with the first side of the dielectric layer 121, the negative probe is in contact with the second side of the dielectric layer 121, and a pressure of 100N is applied to the dielectric layer 121 in the thickness direction of the dielectric layer 121. , the measured voltage reading is 18mV.

Among them, the lowest potential of the negative electrode piece 120 is 37mV when performing three-electrode detection on the battery core 100 .

Example 8

The differences from Example 2 are:

Lead zirconate titanate (PbZr _0.6 Ti _0.4 O ₃ ) is replaced with tellurium oxide crystal as the dielectric material. The coercive field strength of the tellurium oxide crystal is 1.2KV/mm at 25°C. In the process of preparing the dielectric layer 121, the parallel electric field strength when polarizing the dielectric material is 3kV/mm, and the thickness of the dielectric layer 121 is 5 μm;

In the thickness direction of the dielectric layer 121 , the dielectric layer 121 has a first side facing the negative electrode piece 120 and a second side away from the negative electrode piece 120 . The positive probe of the voltmeter is in contact with the first side of the dielectric layer 121, the negative probe is in contact with the second side of the dielectric layer 121, and a pressure of 100N is applied to the dielectric layer 121 in the thickness direction of the dielectric layer 121. , the measured voltage reading is 16mV.

Preparation of the isolation film 130: A polyethylene film (PE) with a thickness of 15 μm is selected as the base film 131, and organic coatings are coated on both sides of the isolation film 130. Preparation of organic coating: 5 parts by weight of styrene-butadiene polymer powder, 40 parts by weight of polyacrylate and 55 parts by weight of ethyl acetate are mixed evenly to obtain an organic coating slurry, and the organic coating slurry is The PE base film 131 is coated on both sides by dip coating, and the organic coating slurry is dried at 55°C to obtain an organic coating. The thickness of each organic coating is 4 μm;

Among them, the lowest potential of the negative electrode piece 120 is 27.5mV when performing a three-electrode test on the battery core 100 .

Example 9

The difference from Embodiment 2 is:

Lead zirconate titanate (PbZr _0.6 Ti _0.4 O ₃ ) is replaced with barium titanate (BaTiO ₃ ) as the dielectric material. The coercive field strength of the powdered BaTiO ₃ dielectric material is 1KV/mm at 25°C. In the process of preparing the dielectric layer 121, the parallel electric field strength when polarizing the dielectric material is 4kV/mm;

Among them, the lowest potential of the negative electrode piece 120 is 26mV when performing a three-electrode test on the battery core 100 .

Comparative example 1

The difference from Embodiment 1 is that the dielectric layer 121 is not provided between the isolation film 130 and the negative electrode piece 120 . Among them, the lowest potential of the negative electrode piece 120 is 0 mV when performing three-electrode detection on the battery core 100 .

The electrochemical device 200 in each embodiment and comparative example was tested using the following method:

Negative electrode piece 120 lithium precipitation rate:

Under the condition that the test temperature is 25℃, charge to 4.3V with a constant current at a certain rate, the rate is not less than 3C, then charge with a constant voltage to 0.05C, let it stand for 5 minutes and then discharge to 2.8V at 1C. The capacity obtained in the above steps is the initial capacity of the lithium-ion battery. Charge and discharge the lithium-ion battery at the same rate as the previous step for a cycle test. After 10 cycles, disassemble the battery and observe whether lithium is precipitated from the negative electrode plate 120. The rate at which the negative electrode piece 120 begins to evolve lithium is the rate at which the negative electrode piece 120 begins to evolve lithium.

The lowest potential of the negative electrode piece under three-electrode monitoring is 120/mV:

Make a three-electrode lithium-ion battery: Disassemble the lithium-ion battery after it is fully charged, keep the battery core, and then weld a thin copper wire on the negative electrode current collector 123 on the side near the negative electrode isolation film, and use a small piece of isolation film to connect the copper wire Cover it so that it will not come into contact with the negative electrode to obtain the electrode assembly; place the electrode assembly in the aluminum plastic film, inject the electrolyte prepared above into the packaged battery, and undergo vacuum packaging, standing, formation, shaping, etc. process to complete the preparation of the three-electrode battery.

The prepared three-electrode battery was tested according to the following process: first use the positive electrode and the negative electrode to plate lithium on the thin copper wire for 6 hours each, that is, first charge the positive electrode with 20 μA for 6 hours, and then charge the negative electrode with 20 μA for 6 hours; then charge the three-electrode battery with 1C constant current to 4.3v, charge with constant voltage to 0.05C, leave for 3 minutes, discharge with constant current of 0.5C to 3V, leave for 3 minutes, repeat the above charge and discharge process 2 times; use multiple thermometer channels to monitor the three electrodes during the charge and discharge process Potential, draw the curve of time and negative electrode potential to obtain the lowest potential at the end of negative electrode charging.

Internal resistance (mΩ):

The DC discharge method is used to test the internal resistance of lithium-ion batteries. A large current of 40A is used to instantly discharge the lithium-ion battery for 3 seconds. The voltage drop U at this time is measured. The internal resistance value of the battery core can be obtained through U/40A.

The parameter settings and test results of the above-mentioned Examples 1 to 9 and Comparative Example 1 are shown in Table 1.

Table 1

From Example 1 to Example 9 and Comparative Example 1, it can be seen that the lithium ion battery including the dielectric layer 121 and the isolation film 130 of the present application can significantly increase the negative electrode potential, and the lithium deposition rate of the negative electrode plate 120 is significantly better than that of the conventional battery. A lithium ion battery with a dielectric layer 121 has a lower internal resistance than a lithium ion battery without a dielectric layer 121 . By arranging the dielectric layer 121 on the surface of the negative electrode piece 120, the surface of the negative electrode piece 120 can be macroscopically positively charged, thereby increasing the surface potential of the negative electrode piece 120, making its surface potential higher than the lithium ion nucleation potential, and inhibiting the negative electrode electrode. The sheet 120 precipitates lithium ions, and the isolation membrane 130 includes at least one of inorganic substances or polymers, which increases the porosity of the isolation membrane, increases the retention of the electrolyte, maintains good lithium ion transmission capabilities, and is beneficial to the lithium ion in the The continuous insertion and extraction of the positive and negative electrodes reduces the internal resistance of the lithium-ion battery and stabilizes the charge and discharge performance of the lithium-ion battery. It can also be seen from the table that disposing the dielectric layer 121 on the surface of the isolation film 130 can also achieve the effect of inhibiting the precipitation of lithium ions from the negative electrode plate 120 and improving the charge and discharge performance of the lithium ion battery.

In the drawings of this embodiment, the same or similar numbers correspond to the same or similar components; in the description of this application, it should be understood that if there are terms such as "upper", "lower", "left", "right", etc. The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description. It does not indicate or imply that the device or element referred to must have a specific orientation or a specific orientation. Construction and operation, therefore the terms describing the positional relationships in the drawings are only for illustrative purposes and cannot be understood as limitations of the patent. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the protection of the present application. within the range.

Claims

An electrochemical device, characterized in that it includes a negative electrode piece, a positive electrode piece and an isolation film. The negative electrode piece includes a dielectric layer, the dielectric layer includes a dielectric material, and the isolation film includes a base film and a Functional coating, the functional coating includes at least one of inorganic substances or polymers.
The electrochemical device according to claim 1, wherein when a pressure of 70N to 1000N is applied to both sides of the dielectric layer, the voltage difference on both sides of the dielectric layer ranges from 10mV to 100mV.
The electrochemical device according to claim 1, wherein the dielectric material includes at least one of a dielectric polymer material, a dielectric ceramic material, and a dielectric inorganic compound material.
The electrochemical device according to claim 2, characterized in that

The dielectric polymer materials include copolymers of polyvinylidene fluoride with dielectric properties, copolymers of polyvinylidene fluoride and trifluoroethylene, copolymers of polyvinylidene fluoride and tetrafluoroethylene, and odd-numbered nylon dielectrics. At least one of polymers and amorphous dielectric polymers, wherein the odd-numbered nylon dielectric polymer molecular formula is -(HN-(CH2) x -CO-)n-, x is an even number, and n is any positive number. integer;

The amorphous dielectric polymer includes vinylidene dicyanide/vinyl acetate copolymer, vinylidene dicyanide/vinyl benzoate copolymer, vinylidene dicyanide/vinyl propionate copolymer, vinylidene dicyanide/vinyl propionate copolymer, and vinylidene dicyanide/vinyl benzoate copolymer. /At least one of vinylene pivalate copolymer, vinylidene dicyanide/methyl methacrylate copolymer, and vinylidene dicyanide/isobutylene copolymer;

The dielectric ceramic material includes at least one of unitary dielectric ceramics, binary dielectric ceramics, and ternary dielectric ceramics with dielectric properties; the unitary dielectric ceramics include barium titanate, titanium At least one of lead acid, lithium niobate, and lithium tantalate; the binary system dielectric ceramic includes lead zirconate titanate; the ternary system dielectric ceramic includes lead zirconate titanate-lead magnesium niobate series ceramics , at least one of lead zirconate titanate-lead niobate zincate series ceramics, lead zirconate titanate-lead manganese antimonate series ceramics or ceramic substances represented by formula I;

Pb 1-x M x (Zr y Ti 1-y ) 1-(x/4) O 3Formula I

Where 0＜x＜1, 0＜y＜1, M is any one of Mg, Zn, Nb, Mn, Sb or rare earth elements;

The dielectric inorganic compound material includes at least one of metal oxides, nitrides, carbides, intermetallic compounds, and inorganic salts with dielectric properties.
The electrochemical device according to claim 1, characterized in that the electrochemical device satisfies at least one of the following conditions:

(1) The thickness of the dielectric layer is 0.1 μm to 5 μm.

(2) The coercive field strength of the dielectric material at 25°C is higher than 0kV/mm and less than or equal to 100kV/mm.
The electrochemical device according to claim 1, characterized in that

The inorganic particles include silicon dioxide, magnesium hydroxide, aluminum hydroxide, calcium titanate, barium titanate, lithium phosphate, zinc oxide, aluminum oxide, titanium oxide, magnesium oxide, hafnium dioxide, tin oxide, oxide At least one of zirconium, yttrium oxide, silicon carbide, boehmite, calcium oxide, lithium titanium phosphate, and lithium lanthanum titanate.
The electrochemical device according to claim 1, characterized in that

The polymer includes at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene polymer, styrene-butadiene polymer, and polyacrylic acid.
The electrochemical device according to claim 1, characterized in that

The mass content of the inorganic matter and/or the polymer is 10% to 90% based on the mass of the functional coating.
An electronic device, characterized by comprising the electrochemical device according to any one of claims 1-8.