WO2023184179A1 - Electrode assembly, preparation method therefor and electrochemical device - Google Patents

Abstract

Disclosed in the present application are an electrode assembly, a preparation method therefor and an electrochemical device. The electrode assembly comprises a positive electrode sheet, a negative electrode sheet, a separator and a negative electrode dielectric layer, the separator being arranged between the positive electrode sheet and the negative electrode sheet, the negative electrode dielectric layer being arranged on the negative electrode sheet, the negative dielectric layer comprising a dielectric material, the range of the Curie-Weiss constant of the dielectric material at 25℃ being from 10K to 10^⁶K, the dielectric material in the negative electrode dielectric layer within said range being of a disordered-ordered type, and a built-in electric field being capable of being generated in the negative electrode dielectric layer. The negative dielectric layer the Curie-Weiss constant of which ranges from 10k to 10^⁶K can keep stable in the service life cycle of an electrochemical device more easily, more effectively improve the electric potential of the negative electrode sheet, can weaken a local large current, and uniformize a surface current density of the negative electrode sheet in advance, thus remarkably mitigating a metal ion separate-out problem of a negative electrode sheet of an electrochemical device.

Description

Electrode assembly and preparation method thereof, electrochemical device Technical field

The present application relates to the field of electrochemistry technology, and in particular, to an electrode assembly, a preparation method thereof, and an electrochemical device.

Background technique

Electrochemical devices such as lithium-ion batteries have the advantages of large specific energy, high operating voltage, low self-discharge rate, small size, and light weight, and are widely used in the electronic field. With the rapid development of electric vehicles and mobile electronic devices, people have higher and higher demands for battery energy density, safety, cycle performance and other related requirements.

Among them, 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 sheet 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 sheet, pass through the separator through mass transfer through the electrolyte, and are embedded in the material of the negative electrode sheet. However, when there are flaws in the design of the electrochemical device, the electrochemical device When abnormal conditions such as structural changes 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

The present application provides an electrode assembly, a preparation method thereof, and an electrochemical device, which can solve the problem of metal cation precipitation in the electrochemical device.

In a first aspect, the application provides an electrode assembly, including a positive electrode sheet, a negative electrode sheet, a separator and a negative electrode dielectric layer;

The separator is disposed between the positive electrode sheet and the negative electrode sheet;

The negative dielectric layer is disposed on the negative electrode sheet. The negative dielectric layer includes a dielectric material. The Curie-Weiss constant of the dielectric material at 25°C ranges from 10K to 10^ ⁶ K. This The dielectric material in the negative dielectric layer within the range is of a disorder-ordered type, and the negative dielectric layer can be polarized in an electric field to form a built-in electric field. When the negative electrode dielectric layer is disposed on the surface of the separator or negative electrode sheet, the surface of the negative electrode sheet contacts the positive charge side of the negative electrode dielectric layer, which can increase the surface potential of the negative electrode sheet above the metal cation nucleation overpotential, thereby improving the precipitation of metal cations from the negative electrode sheet. question.

In some exemplary embodiments, the value range of the coercive field strength of the dielectric material at 25°C is: 0KV/mm<Ec≤100KV/mm.

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

In some exemplary embodiments, the dielectric ceramic material includes at least one of a unit dielectric ceramic, a binary dielectric ceramic, and a ternary dielectric ceramic having dielectric properties; the unit system The 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); the ternary dielectric ceramics include: lead zirconate titanate (PbZr _x Ti _1-x O ₃ , where 0＜x＜1)-lead magnesium niobate (PbMg _x Nb _{1- x} O ₃ , where 0＜x＜1) is ceramic, lead zirconate titanate (PbMn _x Sb _1-x O ₃ , where 0＜x＜1) - lead niobate zincate (PbZn _x Nb _1-x O ₃ , Where 0＜x＜1) is ceramic, _lead zirconate titanate (PbMn _x Sb _{1-x O 3} , where 0＜x＜ ₁ ) - lead manganese antimonate (PbMn <1) It is at least one of ceramics or ceramic substances represented by formula I;

Pb _1-x M _x (Zr _y Ti _1-y ) _(1-x/4) O _3Formula I

In formula I, M is selected from any rare earth element, 0＜x＜1, 0＜y＜1;

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

The dielectric polymer materials include polyvinylidene fluoride, polyvinylidene fluoride/polytrifluoroethylene copolymer, polyvinylidene fluoride/polytetrafluoroethylene copolymer, odd-numbered nylon dielectric polymers, At least one of the amorphous dielectric polymers; the amorphous dielectric polymer includes: vinylidene dicyanide/vinyl acetate copolymer, vinylidene dicyanide/vinyl benzoate copolymer, vinylidene dicyanide /At least one of vinylidene dicyanide/ethylene pivalate copolymer, vinylidene dicyanide/ethylene pivalate copolymer, vinylidene dicyanide/methyl methacrylate copolymer, and vinylidene dicyanide/isobutylene copolymer.

In some exemplary embodiments, the Curie-Weiss constant of the dielectric material at 25°C ranges from 10^ ⁴ K to 10^ ⁶ K.

In some exemplary embodiments, the thickness of the negative dielectric layer ranges from 0.1 μm to 5 μm.

In some exemplary embodiments, the negative dielectric layer further includes an organic medium, and the weight ratio of the dielectric material to the organic medium is 0.05-0.5:1; preferably, the organic medium includes N-methyl At least one of pyrrolidone, propylene glycol, glycerin or glycol.

In a second aspect, this application also provides a method for preparing an electrode assembly, including:

The dielectric material is first coated on the surface of the separator and/or the negative electrode sheet, and then polarized to obtain the negative electrode dielectric layer; or,

The dielectric material is first subjected to polarization treatment, and then the polarized dielectric material is attached to the surface of the separator and/or the negative electrode sheet to obtain a negative electrode dielectric layer.

In some exemplary embodiments, the method for polarizing the dielectric material includes: placing the dielectric material in a parallel electric field for polarization, the field strength of the parallel electric field being the dielectric 0.1 times to 6 times the coercive field strength of electrical materials at 25°C.

In a third aspect, the present application also provides an electrochemical device, including an electrode assembly as described above and an electrode assembly obtained by using the preparation method as described above.

Based on the electrode assembly, preparation method and electrochemical device of the embodiment of the present application, a negative electrode dielectric layer is provided on the negative electrode sheet. The negative electrode dielectric layer includes a dielectric material. The dielectric material has a Curie-external temperature at 25°C. The Stiff constant range is from 10K to 10^ ⁶ K. Within this range, the dielectric material in the negative dielectric layer is of disorder-ordered type, and a built-in electric field can be formed in the negative dielectric layer. The negative electrode dielectric layer with a Curie-Weiss constant range of 10K to 10^ ⁶ K is easier to maintain stability during the life cycle of the electrochemical device, is also more effective in increasing the potential of the negative electrode sheet, and can weaken the local large current and advance the Uniform the surface current density of the negative electrode sheet and significantly improve the metal ion precipitation problem of the negative electrode sheet in the electrochemical device.

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 cross-sectional view of a stacked positive electrode sheet and a negative electrode sheet of an electrode assembly according to an embodiment of the present application;

Figure 2 is a partial cross-sectional view of an electrochemical device implemented in the present application;

Figure 3 is a cross-sectional view of a dielectric layer disposed on the surface of a separator according to an implementation of the present application;

Figure 4 is a cross-sectional view of a dielectric layer disposed on the surface of the separator and the surface of the negative electrode sheet in one implementation of the present application;

Figure 5 is a schematic diagram for calculating the Curie-Weiss constant of the dielectric material in the dielectric coating according to an implementation of the present application;

Figure 6 is a cross-sectional view of a dielectric layer disposed on the surface of a negative electrode sheet according to an implementation of the present application;

Figure 7 is a cross-sectional view of an implementation of the present application in which the dielectric layer completely covers the negative electrode sheet;

Figure 8 is a cross-sectional view of the positive electrode sheet and the negative electrode sheet being wound and arranged in an electrode assembly according to an implementation of the present application;

FIG. 9 is a schematic diagram of the direction of the polarization electric field in the dielectric layer according to an implementation of the present application.

Reference signs:

100. Electrode assembly

110. Positive electrode sheet; 111. Positive electrode current collector; 112. Positive electrode active material;

120. Negative electrode sheet; 121. Negative electrode current collector; 122. Negative electrode active material;

130. Diaphragm;

140. Negative dielectric layer;

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 with reference to the 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.

The inventor found that in electrochemical devices, common apparent causes of metal cation precipitation problems in negative electrode sheets include the following categories: a. Improper size design of the negative electrode sheet, resulting in insufficient sites for embedded metal cations; b. Abnormal paths of embedded metal cations , such as the deformation of the electrode assembly during the cycle, and the precipitation of metal cations caused by the destruction of the interface between the positive electrode sheet and the negative electrode sheet; c. Abnormality of the main material, such as the compaction density of the negative active material of the negative electrode sheet is too high, and the precipitation of metal cations caused by the destruction of the surface pore structure ;d. The precipitation of metal cations at specific locations in the electrode assembly, such as the precipitation of metal cations at corners due to complex stress field conditions. Fundamentally, the problem of metal cation precipitation in the negative electrode sheet is rooted in the reduction in potential of the negative electrode sheet caused by insufficient kinetics during the insertion of metal cations. Based on this, this application provides an electrode assembly and a preparation method thereof, an electrochemical device and an electronic device.

As shown in FIG. 1 , it is a schematic structural diagram of an electrode assembly 100 according to an embodiment of the present application. The electrode assembly 100 is installed in an electrochemical device 200 . As shown in FIG. 2 , the electrode assembly 100 is installed in an electrochemical device 200 . A schematic structural diagram of the outer packaging 210. The electrode assembly 100 includes a positive electrode sheet 110, a negative electrode sheet 120 and a separator 130. The separator 130 is disposed between the positive electrode sheet 110 and the negative electrode sheet 120 to separate the positive electrode sheet 110 from the negative electrode sheet 120. The separator 130 has ion insulation and prevents The positive electrode piece 110 and the negative electrode piece 120 are in contact and then short-circuited.

The electrode assembly 100 further includes a negative dielectric layer 140 disposed between the separator 130 and the negative electrode sheet 120 . The number of the negative dielectric layer 140 is at least one layer. As shown in FIGS. 3 and 4 , the dielectric layer can be connected to the surface of at least one of the separator 130 and the negative electrode sheet 120 . For example, the negative dielectric layer 140 can be positioned on the surface of the negative electrode sheet 120 and attached to or spaced apart from the separator 130; or, the negative electrode dielectric layer 140 can be positioned on the surface of the separator 130 facing the negative electrode sheet 120 and attached to the negative electrode sheet 120. or interval settings.

The negative electrode dielectric layer 140 includes a dielectric material. The Curie-Weiss constant of the dielectric material in this application ranges from 10K to 10^ ⁶ K at 25°C. Within this range, the dielectric material is a disorder-ordered type. The negative electrode The dielectric layer 140 can be polarized in an electric field to form a built-in electric field. The negative dielectric layer 140 with the built-in electric field is more likely to remain stable during the life cycle of the electrochemical device 200 and is more effective in increasing the potential of the negative electrode sheet 120 . When the negative dielectric layer 140 is disposed on the surface of the separator 130 or the negative electrode sheet 120, the surface of the negative electrode sheet 120 contacts the positive charge side of the negative electrode dielectric layer 140, which can increase the surface potential of the negative electrode sheet 120 to above the metal cation nucleation overpotential, thereby Improve the metal cation precipitation problem of negative electrode sheet 120. When the metal cations reach the surface of the negative electrode dielectric layer 140, the built-in electric field inside the negative electrode dielectric layer 140 performs negative feedback on the local concentrated metal cation flow, weakening the local large current and uniformizing the surface current density of the negative electrode sheet 120 in advance. , significantly improving the problem of metal ion precipitation from the negative electrode sheet in electrochemical devices.

Further, the Curie-Weiss constant of dielectric materials at 25°C ranges from 10^ ³ K to 10^ ⁵ K.

In some exemplary embodiments, the value range of the coercive field strength of the dielectric material at 25°C is: 0KV/mm<Ec≤100KV/mm. Dielectric materials that meet the above coercive field strength range have dielectric properties. The negative dielectric layer 140 including the above dielectric material will be placed in a parallel electric field for polarization, changing the direction of the dipole moment of the dielectric material, so that The dielectric material in the negative dielectric layer 140 is of a disorder-ordered type, which can form a built-in electric field in the negative dielectric layer 140 . After the polarization is completed, the dielectric coefficient of the dielectric material in the negative dielectric layer 140 is obtained, and the Curie-Weiss law and the dielectric coefficient can be used to obtain the Curie-Weiss coefficient of the dielectric material in the negative dielectric layer 140 constant. The dielectric coefficient of dielectric materials satisfies the Curie-Weiss law, which is:

Among them, ε is the dielectric coefficient, T is the absolute temperature, Tc is the Curie temperature of the material, and c is the Curie-Weiss constant. As shown in Figure 5, the Curie-Weiss constant c can be obtained by obtaining the absolute temperature (i.e., the current ambient temperature, such as room temperature 25°C), the Curie temperature of the material, and the dielectric coefficient of the dielectric material, and fitting the dielectric temperature curve The reciprocal measure of slope.

It should be noted that the number of dielectric material molecules in the negative dielectric layer 140 is huge, and it is difficult to completely unify the electric dipole moment directions of each dielectric material with coercive field strength. The direction of the electric dipole moment of each dielectric material may be different. For example, in the negative dielectric layer 140, the direction of the electric dipole moment of all dielectric materials is from the negative electrode sheet 120 to the positive electrode sheet 110; or, as shown in FIG. 6, The direction of the electric dipole moment of part of the dielectric material is from the negative electrode sheet 120 to the positive electrode sheet 110, and the direction of the electric dipole moment of the other part of the dielectric material is from the positive electrode sheet 110 to the negative electrode sheet 120. In Figure 6, the arrow in the negative electrode dielectric layer 140 The direction indicated is the direction of the electric dipole moment of the dielectric material. In the above two cases, the angles between the electric dipole moment direction of each dielectric material and the thickness direction X of the negative electrode sheet 120 may be the same or different.

In some exemplary embodiments, the dielectric material is selected from at least one of a dielectric ceramic material, a dielectric inorganic compound material, or a dielectric polymer material.

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 ( _{PbZr x} Ti _1-x O ₃ , where 0＜x＜ ₁ ) - lead magnesium niobate (PbMg ＜1) Ceramics _, lead zirconate titanate (PbMn _x Sb _{1-x O 3} , where 0＜x＜ ₁ ) - lead niobate zincate (PbZn Ceramics, lead zirconate titanate (PbMn _{x Sb 1-x O 3} , where 0＜x＜ ₁ )-lead manganese antimonate (PbMn at least one of the ceramic substances shown;

Pb _1-x M _x (Zr _y Ti _1-y ) _(1-x/4) O _3Formula I

In formula I, M is selected from any rare earth element, 0<x<1, 0<y<1.

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

Dielectric polymer materials include polyvinylidene fluoride, polyvinylidene fluoride/polytrifluoroethylene copolymer, polyvinylidene fluoride/polytetrafluoroethylene copolymer, odd-numbered nylon dielectric polymer-(HN -(CH2) _x -CO-)n- (where x is an even number and n is any positive integer), at least one of amorphous dielectric polymers; amorphous dielectric polymers include: Cyanide/vinyl acetate copolymer, vinylidene dicyanide/vinyl benzoate copolymer, vinylidene dicyanide/vinyl propionate copolymer, vinylidene dicyanide/vinyl pivalate copolymer, vinylidene dicyanide/ At least one of methyl methacrylate copolymer and vinylidene cyanide/isobutylene copolymer.

In some exemplary embodiments, the thickness of the negative dielectric layer 140 ranges from 0.1 μm to 5 μm. For example, the thickness of the negative dielectric layer 140 may be 0.1 μm, 1 μm, 3 μm, 4 μm, or 5 μm. When the thickness of the negative electrode dielectric layer 140 is less than 0.1 μm, the thickness of the negative electrode dielectric layer 140 is too thin to form an effective built-in electric field in the negative electrode dielectric layer 140 to uniform the current on the surface of the negative electrode sheet 120; when the negative electrode dielectric layer 140 When the thickness is greater than 0.1 μm, the thickness of the negative electrode dielectric layer 140 is too thick, and it is difficult for metal cations to penetrate the negative electrode dielectric layer 140 and migrate into the negative electrode sheet 120. At the same time, the negative electrode dielectric layer 140 is too thick and will occupy more electrochemical device 200. The internal space 210a causes the proportion of inactive materials in the electrochemical device 200 to increase. In addition, if the negative electrode dielectric layer 140 is too thick or too thin, it is not conducive to the bending process of the negative electrode dielectric layer 140 with the negative electrode sheet 120 or the separator 130 , and limits the application of the negative electrode dielectric layer 140 in the electrochemical device 200 .

The negative dielectric layer also includes an organic medium, and the weight ratio of the dielectric material to the organic medium is 0.05 to 0.5:1. The organic medium includes at least one of N-methylpyrrolidone, propylene glycol, glycerol or glycol.

The positive electrode sheet 110 includes a positive electrode current collector 111 and a positive electrode active material 112. The positive electrode active material 112 is provided on at least one surface of the positive electrode current collector 111. The negative electrode sheet 120 includes a negative electrode current collector 121 and a negative electrode active material 122. The negative electrode active material 122 is provided on on at least one surface of the negative electrode current collector 121 . The negative active material 122 forms a pore structure to form spaces in which metal cations are embedded. When the negative electrode dielectric layer 140 is disposed on the surface of the negative electrode sheet 120, the negative electrode active material 122 is connected to the negative electrode dielectric layer 140.

The negative electrode sheet 120 of the present application is not particularly limited. The negative active material 122 can be any negative active material 122 in the prior art. The negative active material 122 includes graphite, hard carbon, soft carbon, silicon, silicon carbon or silicon oxide, etc. At least one; the negative electrode current collector 121 can be any negative electrode current collector 121 known in the art, such as copper foil, aluminum foil, aluminum alloy foil or composite current collector.

The separator 130 of the present application is not particularly limited. For example, the separator 130 may be made of materials that are stable to the electrolyte of the present application, so that the ions in the electrolyte can pass through the separator 130, so that the ions in the electrolyte can pass through the positive electrode. There is movement between the sheet 110 and the negative electrode sheet 120. For example, the separator 130 may include polyethylene (PE) or the like.

When the negative dielectric layer 140 is disposed on the surface of the negative active material 122 or the separator 130, the dielectric material in the negative dielectric layer 140 can be stably connected to the negative active material 122 and the separator 130 and is not easily peeled off.

As shown in FIG. 7 , in the thickness direction X of the negative electrode sheet 120 , the negative electrode dielectric layer 140 completely covers the negative electrode active material 122 . The electric field direction of the built-in electric field in the negative dielectric layer 140 and the thickness direction 120 surface current density.

The separator 130 is disposed between the positive electrode sheet 110 and the negative electrode sheet 120. The negative electrode sheet 120, the separator 130 and the positive electrode sheet 110 can be stacked or wound in sequence along the thickness direction X of the negative electrode sheet 120. As shown in Figure 8, it is a negative electrode The structure schematic diagram of the sheet 120, the separator 130 and the positive electrode sheet 110 being wound and arranged. The direction pointed by the arrow in the negative electrode dielectric layer 140 in Figure 9 is the direction of the built-in electric field.

The positive electrode sheet 110 of the present application is not particularly limited. The positive active material 112 includes at least one of nickel cobalt manganese ternary materials, nickel cobalt aluminum materials, lithium iron phosphate, lithium cobalt oxide, lithium manganate, lithium iron manganese phosphate or lithium titanate. One; the positive electrode current collector 111 can be any positive electrode current collector 111 known in the art, such as aluminum foil, aluminum alloy foil or composite current collector, etc., and the positive electrode active material 112 can be any positive electrode active material 112 in the prior art.

The electrode assembly 100 also 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. When the electrode assembly 100 is disposed in the electrochemical device 200, the positive electrode tab and the negative electrode tab are used to electrically connect with the external circuit to charge and discharge the electrochemical device 200, and to monitor the internal working status of the electrochemical device 200.

The present application also provides a method for preparing the electrode assembly 100, which is used to prepare the electrode assembly 100 as described above. Preparation methods include:

The dielectric material is first provided on the surface of the separator 130 and/or the negative electrode sheet 120, and then is subjected to polarization treatment to obtain the negative electrode dielectric layer 140. Alternatively, the dielectric material is first subjected to polarization treatment, and then the polarized dielectric material is attached to the surface of the separator 130 and/or the negative electrode sheet 120 to obtain the negative electrode dielectric layer 140 . Among them, the Curie-Weiss constant of dielectric materials at 25°C ranges from 10K to 10^ ⁶ K.

The built-in electric field in the negative dielectric layer 140 can be formed during the polarization process. For example, a polarization device can be used to perform polarization processing on the dielectric material in the negative dielectric layer 140. The polarization medium can be air, through The controlled polarization device generates a parallel electric field, and the negative dielectric layer 140 is placed in the parallel electric field. The parallel electric field acts on the dielectric material of the negative dielectric layer 140 and adjusts the direction of the electric dipole moment of the dielectric material so that the negative dielectric layer A built-in electric field is formed within 140°C. By adjusting the direction of the parallel electric field relative to the dielectric material in the negative dielectric layer 140, the direction of the electric dipole moment of the dielectric material in the dielectric layer can be adjusted, thereby adjusting the direction of the built-in electric field in the negative dielectric layer 140.

In some exemplary embodiments, the dielectric material is placed in a parallel electric field for polarization treatment, and the field strength of the parallel electric field is 0.1 to 6 times the coercive field strength of the dielectric material at 25°C. The time range for placing the dielectric material in a parallel electric field for polarization treatment is 30 minutes.

The dielectric material can be disposed on the surface of the separator 130 or the negative electrode sheet 120 in an amorphous state or a shaped state, where the amorphous state includes powder or slurry, etc., and the shaped state includes film, sheet, etc. For example, the dielectric polymer material and dielectric ceramic material among the above dielectric materials can be in powder form and mixed in a solvent and placed on the surface of the separator 130 or the negative electrode sheet 120, and then undergo polarization treatment and other processes to form the negative electrode dielectric layer 140. ; The dielectric inorganic compound can be made into a thin film, and is polarized to form the negative dielectric layer 140, which is then laminated on the surface of the separator 130 or the negative electrode sheet 120.

When the dielectric material is processed into a shaped state to form the negative dielectric layer 140 and then placed on the surface of the separator 130 or the negative electrode sheet 120, the negative dielectric layer 140 can be bonded to the surface of the separator 130 or the negative electrode sheet 120, or, After the negative electrode dielectric layer 140 is initially connected to the surface of the separator 130 or the negative electrode sheet 120, 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 negative electrode dielectric layer 140 and heat treatment is performed. At least one processing method of the negative dielectric layer 140 fixes the negative dielectric layer 140 to the separator 130 or the negative electrode sheet 120 .

Please refer to Figure 2 again. This application also provides an electrochemical device 200. The electrochemical device 200 includes an outer package 210, an electrolyte, and the electrode assembly 100 as described above. The electrode assembly 100 adopts the method of the electrode assembly 100 as described above. Preparation method obtained. The electrode assembly 100 is disposed in the inner space 210a of the outer package 210, and the electrolyte is filled in the inner space 210a of the outer package 210. This application has no particular limitation on electrochemical devices, which may include, but are not limited to, lithium-ion batteries or sodium-ion batteries.

The outer packaging 210 in this application is not particularly limited, and any well-known outer packaging 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 soft bag may be made of aluminum plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

The electrolyte solution in this application is not particularly limited, any electrolyte solution known in the art can be used, and 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 present application also provides an electronic device, including the above electrochemical device 200. For example, the electronic device may include a notebook computer, a mobile phone, a car, a motorcycle, a power-assisted bicycle, 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 negative dielectric layer 140:

(1) Provide powdered BaTiO ₃ as a dielectric material. The coercive field strength of the powdered BaTiO ₃ dielectric material is 1KV/mm at 25°C. Disperse the powdered BaTiO ₃ dielectric material in N-methylpyrrolidone. (NMP), stir to disperse BaTiO ₃ evenly to obtain a dielectric slurry, in which the weight ratio of BaTiO ₃ to NMP is 0.12, that is, the solid content of the dielectric slurry is 12%.

(2) Use a scraper to evenly apply the dielectric slurry on the surface of the polyethylene (PE) separator 130 with a thickness of 15 μm, and place it in a vacuum drying oven to dry at 80°C to obtain a separator 130 with dielectric material attached to the surface. After drying, the thickness of the dielectric material attached to the surface of the separator 130 is 1 μm (that is, the thickness of the subsequently obtained negative dielectric layer 140 attached to the surface of the separator 130 is 1 μm).

(3) Place the diaphragm 130 with the dielectric material attached to the surface in the parallel electric field of the polarization device for polarization. The polarization medium is air. The polarization device includes a positive pressure plate and a negative pressure plate for generating a parallel electric field. The positive pressure plate The direction of the parallel electric field between the positive pressure plate and the negative pressure plate is from the positive pressure plate to the negative pressure plate. The dielectric material is placed close to the negative pressure plate. The parallel electric field strength is 0.1kV/mm and the polarization time is 30 minutes. After the polarization is completed, the surface is adhered to The separator 130 of the negative dielectric layer 140 is cut into a specification of (42mm×62mm) for use. Among them, the thickness of the negative dielectric layer 140 is 1 μm. After polarization, the Curie-Weiss constant of the dielectric material in the negative dielectric layer 140 was measured using the Sanqi Electronics 1200HTDE-LTC high temperature dielectric measurement system to be 1.51×10 ^5K .

Preparation of positive electrode sheet 110:

Mix the ternary cathode active material 112 (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-methyl Pyrrolidone (NMP) was used as the solvent to prepare a slurry with a solid content of 0.75, and stirred evenly. The slurry is evenly coated on the positive electrode current collector 111 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 sheet 120:

Mix the negative active material 122 (graphite), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) in a weight ratio of 97:1.0:2.0, add N-methylpyrrolidone (NMP) as the solvent, and prepare A slurry with a solid content of 0.8 and stir evenly. The slurry is evenly coated on the two opposite surfaces of the copper foil of the negative electrode current collector 121, and dried at 80°C to obtain a double-sided coated negative electrode sheet 120. The coating thickness on one side is 100 μm, and the coating thickness on both sides is 100 μm. The coated negative electrode sheet 120 is cut into specifications (40mm×60mm) for use.

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 lithium-ion batteries:

The above-mentioned cut negative electrode sheet 120 is placed in the middle, and the above-mentioned cut positive electrode sheet 110 is arranged on two opposite sides in the thickness direction Finally, the separator 130 with the negative dielectric layer 140 attached, and the negative dielectric layer 140 faces the negative electrode sheet 120, place the negative electrode sheet 120, two layers of positive electrode sheets 110 and two layers of separator 130 with the negative electrode dielectric layer 140 attached along the negative electrode sheet. 120 thickness direction X stacking. After fixing the four corners of the laminated negative electrode sheet 120, positive electrode sheet 110 and separator 130 with tape, place it into the inner space 210a of the aluminum plastic film outer package 210, and move it toward the inner space of the outer package 210 through the opening of the outer package 210. After injecting the electrolyte in step 210a, the opening of the outer package 210 is sealed to obtain a laminated lithium-ion battery.

Example 2

The difference from Embodiment 1 is that the diaphragm 130 with the dielectric material attached to the surface is placed in a parallel electric field for polarization treatment, and the parallel electric field field strength is 1 kV/mm. After polarization, the Curie-Weiss constant of the dielectric material in the negative dielectric layer 140 is 1.53×10 ⁵ K.

Example 3

The difference from Embodiment 1 is that the diaphragm 130 with the dielectric material attached to the surface is placed in a parallel electric field for polarization treatment, and the parallel electric field field strength is 3 kV/mm. After polarization, the Curie-Weiss constant of the dielectric material in the negative dielectric layer 140 is 1.65×10 ⁵ K.

Example 4

The difference from Embodiment 1 is that the diaphragm 130 with the dielectric material attached to the surface is placed in a parallel electric field for polarization treatment, and the parallel electric field field strength is 5 kV/mm. After polarization, the Curie-Weiss constant of the dielectric material in the negative dielectric layer 140 is 1.56×10 ⁵ K.

Example 5

The difference from Embodiment 1 is that the diaphragm 130 with the dielectric material attached to the surface is placed in a parallel electric field for polarization treatment, and the parallel electric field field strength is 3 kV/mm. After polarization, the thickness of the dielectric layer provided on the surface of the separator 130 is 0.1 μm. After polarization, the Curie-Weiss constant of the dielectric material in the negative dielectric layer 140 is 1.56×10 ⁵ K.

Example 6

The difference from Embodiment 5 is that the thickness of the dielectric layer provided on the surface of the separator 130 is 3 μm. After polarization, the Curie-Weiss constant of the dielectric material in the negative dielectric layer 140 is 1.67×10 ⁵ K.

Example 7

The difference from Embodiment 5 is that the thickness of the dielectric layer provided on the surface of the separator 130 is 5 μm. After polarization, the Curie-Weiss constant of the dielectric material in the negative dielectric layer 140 is 1.75×10 ⁵ K.

Example 8

The difference from Example 1 is:

Preparation of dielectric layer:

(1) Provide powdered BaTiO ₃ as a dielectric material. The coercive field strength of the powdered BaTiO ₃ dielectric material is 1KV/mm at 25°C. Disperse the powdered BaTiO ₃ dielectric material in N-methylpyrrolidone. (NMP), stir to disperse BaTiO ₃ evenly to obtain dielectric slurry. Use a scraper to evenly apply the dielectric slurry on the two opposite surfaces of the negative electrode sheet 120. After drying in a vacuum drying oven at 80°C, the thickness of each layer of dielectric material attached to the surface of the negative electrode sheet 120 is 0.1 μm ( That is, the thickness of each negative electrode dielectric layer 140 subsequently obtained and attached to the surface of the negative electrode sheet 120 is 0.1 μm). After polarization, the Curie-Weiss constant of the dielectric material in the negative electrode dielectric layer 140 was measured using the Sanqi Electronics 1200HTDE-LTC high-temperature dielectric measurement system to be 1.51×10 ⁵ K.

(2) Place the negative electrode sheet 120 with dielectric material on both sides in the parallel electric field of the polarization device for polarization. Place the dielectric material on one side of the negative electrode sheet 120 against the positive plate of the polarization device and place it in parallel. The electric field strength is 3kV/mm, and the polarization time is 30 minutes. Then flip the negative electrode piece 120, and 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, and the polarization is completed. Finally, the negative electrode sheet 120 with dielectric layers on both sides is obtained.

Preparation of lithium-ion batteries:

The above-mentioned cut negative electrode sheet 120 with the negative electrode dielectric layer 140 on both sides is placed in the middle, and the cut positive electrode sheets 110 are respectively placed on both sides of the negative electrode sheet 120 in the thickness direction X, and between each positive electrode sheet 110 and A polyethylene (PE) separator 130 with a thickness of 15 μm is arranged between the negative electrode sheets 120. The negative electrode sheet 120 with a negative electrode dielectric layer 140 on both sides, two layers of positive electrode sheets 110 and two layers of separators 130 are stacked along the thickness direction X of the negative electrode sheet 120. . After fixing the four corners of the laminated negative electrode sheet 120, positive electrode sheet 110 and separator 130 with tape, place it into the inner space 210a of the aluminum plastic film outer package 210, and move it toward the inner space of the outer package 210 through the opening of the outer package 210. After injecting the electrolyte in step 210a, the opening of the outer package 210 is sealed to obtain a laminated lithium-ion battery.

Example 9

The difference from Embodiment 8 is that the thickness of each negative dielectric layer 140 provided on the surface of the negative electrode sheet 120 is 1 μm. After polarization, the Curie-Weiss constant of the dielectric material in the negative dielectric layer 140 is 1.53×10 ⁵ K.

Example 10

The difference from Embodiment 8 is that the thickness of each negative electrode dielectric layer 140 provided on the surface of the negative electrode sheet 120 is 3 μm. After polarization, the Curie-Weiss constant of the dielectric material in the negative dielectric layer 140 is 1.58×10 ⁵ K.

Example 11

The difference from Embodiment 8 is that the thickness of each negative dielectric layer 140 provided on the surface of the negative electrode sheet 120 is 5 μm. After polarization, the Curie-Weiss constant of the dielectric material in the negative dielectric layer 140 is 1.59×10 ⁵ K.

Example 12

The difference from Embodiment 8 is that the negative electrode sheet 120 with dielectric material on both sides is placed in a parallel electric field for polarization, and the parallel electric field field strength is 0.1 kV/mm. After polarization, the Curie-Weiss constant of the dielectric material in the negative electrode dielectric layer 140 is 1.72×10 ⁵ K.

Example 13

The difference from Embodiment 8 is that the negative electrode sheet 120 with dielectric material on both sides is placed in a parallel electric field for polarization, and the parallel electric field field strength is 1 kV/mm. After polarization, the Curie-Weiss constant of the dielectric material in the negative dielectric layer 140 is 1.52×10 ⁵ K.

Example 14

The difference from Embodiment 8 is that the negative electrode sheet 120 with dielectric material on both sides is placed in a parallel electric field for polarization, and the parallel electric field field strength is 5 kV/mm. After polarization, the Curie-Weiss constant of the dielectric material in the negative dielectric layer 140 is 1.66×10 ⁵ K.

Example 15

The difference from Example 1 is that the dielectric material is powdered triglycine sulfate (TGS), and the coercive field strength of the powdered TGS dielectric material is 0.8KV/mm at 25°C. Powdered TGS dielectric material is dispersed in N-methylpyrrolidone (NMP), and the TGS is dispersed evenly by stirring to obtain a dielectric slurry. The dielectric slurry is evenly coated on the surface of the polyethylene (PE) separator 130 with a thickness of 15 μm using a scraper. After drying in a vacuum drying oven at 80° C., the thickness of the dielectric material attached to the surface of the separator 130 is 1 μm. The diaphragm 130 with TGS dielectric material on the surface is placed in a parallel electric field for polarization. The dielectric material is placed against the negative plate of the polarization device. The parallel electric field strength is 3kV/mm and the polarization time is 30 minutes. After completion, the separator 130 with the negative dielectric layer 140 attached to the surface is obtained. The thickness of the negative dielectric layer 140 provided on the surface of the separator 130 is 1 μm. The negative dielectric layer is measured using the Sanqi Electronics 1200HTDE-LTC high temperature dielectric measurement system. The Curie-Weiss constant of dielectric materials within 140 is 3.25×10 ⁵ K.

Example 16

The difference from Example 1 is that the dielectric material is powdered NaNO ₂ , and the coercive field strength of the powdered NaNO ₂ dielectric material is 1.2KV/mm at 25°C. Powdered NaNO ₂ dielectric material is dispersed in N-methylpyrrolidone (NMP), and the NaNO ₂ is dispersed evenly by stirring to obtain a dielectric slurry. The dielectric slurry is evenly coated on the surface of the polyethylene (PE) separator 130 with a thickness of 15 μm using a scraper. After drying in a vacuum drying oven at 80° C., the thickness of the dielectric material attached to the surface of the separator 130 is 1 μm. The diaphragm 130 with NaNO ₂ dielectric material on the surface is placed in a parallel electric field for polarization. The dielectric material is placed close to the negative plate of the polarization device. The parallel electric field field strength is 3kV/mm, and the polarization time is 30 minutes. After the formation is completed, the separator 130 with the negative dielectric layer 140 attached to the surface is obtained. The thickness of the negative dielectric layer 140 provided on the surface of the separator 130 is 1 μm. The negative dielectric is measured using the Sanqi Electronics 1200HTDE-LTC high temperature dielectric measurement system. The Curie-Weiss constant of the dielectric material within layer 140 is 1.01×10 ⁴ K.

Example 17

The difference from Example 8 is that the dielectric material is nylon 7, and the coercive field strength of the nylon 7 dielectric material is 97KV/mm at 25°C. Nylon 7 dielectric material was prepared into a nylon 7 film with a thickness of 5 μm (molecular formula is -(HN-(CH ₂ ) ₆ -CO-)n-, brand: Taiwan Chemical Fiber Co., Ltd., brand: NP4000), and the nylon The 7 film is placed in a parallel electric field for polarization. The parallel electric field strength is 280kV/mm and the polarization time is 30 minutes. The built-in electric field direction is parallel to the thickness direction X of the nylon 7 film and remains constant. After the polarization is completed, the negative electrode dielectric is obtained. Layer 140, attach the negative dielectric layer 140 to the surface of the negative electrode sheet 120 in the positively charged direction. Among them, the negative electrode dielectric layer 140 obtained after polarization was measured using the Sanqi Electronics 1200HTDE-LTC high temperature dielectric measurement system and the Curie-Weiss constant of the dielectric material in the negative electrode dielectric layer 140 was 10 ⁴ K-10 ⁵ K. In this embodiment, the negative electrode dielectric layer 140 can be directly attached to the surface of the negative electrode sheet 120, and in the subsequent formation process of lithium-ion battery preparation, the adhesive force between the negative electrode dielectric layer 140 and the negative electrode sheet 120 can be further increased.

Comparative example 1

The difference from Embodiment 1 is that the negative dielectric layer 140 is not provided between the separator 130 and the negative electrode sheet 120 .

The electrode assembly 100 and the electrochemical device 200 in each embodiment and comparative example were tested using the following methods:

Negative plate 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. Perform a cycle test on the lithium-ion battery by charging at the same rate/1C discharge as the previous step. After 10 cycles, disassemble the battery and observe whether lithium is precipitated from the negative electrode sheet. The rate at which lithium deposition begins on the negative electrode sheet is the rate at which lithium deposition occurs on the negative electrode sheet.

The parameter settings and test results of the above-mentioned Examples 1-17 and Comparative Example 1 are shown in Table 1.

Table 1

(Note: In Table 1, the negative side of the separator is the side of the separator 130 facing the negative electrode sheet 120)

It can be seen from Examples 1-17 and Comparative Example 1 that the lithium evolution rate of the lithium ion battery including the negative electrode dielectric layer 140 provided by the present application is significantly improved, which is significantly better than that of the lithium battery without the negative electrode dielectric layer 140 ion battery. When the Curie-Weiss constant of the dielectric material in the negative dielectric layer 140 ranges from 10K to 10^ ⁶ K, the dielectric material in the negative dielectric layer 140 is a disorder-ordered type, and the negative dielectric layer 140 The built-in electric field can be formed after polarization in the electric field, which is easier to maintain stability during the life cycle of the electrochemical device. It can effectively increase the potential of the negative electrode sheet and weaken the large current that occurs locally, improve the lithium deposition of the negative electrode sheet, and increase the battery capacity. Chemical plant performance.

It can be seen from Embodiments 1-7 and 12-14 that no matter whether the negative dielectric layer 140 is located on the anode side of the separator or on the surface of the negative electrode sheet 120, the parallel electric field intensity and direction within the scope of the present application are used to control the negative dielectric layer 140. After polarization, the lithium deposition rate of the negative electrode sheet 120 of the lithium ion stack battery can be effectively increased.

The thickness of the negative electrode dielectric layer 140 usually also affects the lithium deposition rate of the negative electrode sheet 120 of the lithium ion battery. It can be seen from Example 3, Examples 5-7, and Examples 8-11 that by optimizing the thickness of the negative electrode dielectric layer 140 within the scope of the present application, a lithium ion battery with a further improved lithium deposition rate of the negative electrode sheet 120 can be obtained.

It can be seen from Example 3 and Examples 15-17 that the coercive field strength of the dielectric layer obtained by using different types of dielectric materials is within the scope of the present application, and the analysis of the negative electrode sheet 120 of the lithium ion stack battery is Lithium rates were improved.

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 (10)

1. An electrode assembly, characterized by including:

   Positive electrode sheet, negative electrode sheet, separator and negative electrode dielectric layer;

   The separator is disposed between the positive electrode sheet and the negative electrode sheet;

   The negative dielectric layer is disposed on the negative electrode sheet. The negative dielectric layer includes a dielectric material, and the Curie-Weiss constant of the dielectric material at 25° C. ranges from 10K to 10^ ⁶ K.
2. The electrode assembly according to claim 1, wherein the coercive field strength of the dielectric material at 25° C. ranges from: 0KV/mm<Ec≤100KV/mm.
3. The electrode assembly according to claim 1, wherein the dielectric material includes at least one of a dielectric ceramic material, a dielectric inorganic compound material, or a dielectric polymer material.
4. The electrode assembly according to claim 3, characterized in that:

   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, At least one of lead titanate, lithium niobate, and lithium tantalate; the binary dielectric ceramic includes: lead zirconate titanate; the ternary dielectric ceramic includes: lead zirconate titanate-magnesium niobate At least one of lead-based ceramics, lead zirconate titanate-lead niobate zincate-based ceramics, lead zirconate titanate-lead manganese antimonate-based ceramics, or ceramic substances represented by Formula I;

   Pb _1-x M _x (Zr _y Ti _1-y ) _(1-x/4) O _3Formula I

   In formula I, M is selected from any rare earth element, 0＜x＜1, 0＜y＜1;

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

   The dielectric polymer materials include polyvinylidene fluoride, polyvinylidene fluoride/polytrifluoroethylene copolymer, polyvinylidene fluoride/polytetrafluoroethylene copolymer, odd-numbered nylon dielectric polymers, at least one amorphous dielectric polymer;

   Amorphous dielectric polymers include: vinylidene dicyanide/vinyl acetate copolymer, vinylidene dicyanide/vinyl benzoate copolymer, vinylidene dicyanide/vinyl propionate copolymer, vinylidene dicyanide/ At least one of vinylene pivalate copolymer, vinylidene dicyano/methyl methacrylate copolymer, and vinylidene dicyano/isobutylene copolymer.
5. The electrode assembly according to claim 1, wherein the Curie-Weiss constant of the dielectric material at 25°C ranges from 10^ ⁴ K to 10^ ⁶ K.
6. The electrode assembly according to claim 1, wherein the thickness of the negative dielectric layer ranges from 0.1 μm to 5 μm.
7. The electrode assembly according to claim 1, wherein the negative dielectric layer further includes an organic medium, and the weight ratio of the dielectric material to the organic medium is 0.05 to 0.5:1;

   The organic medium includes at least one of N-methylpyrrolidone, propylene glycol, glycerol or glycol.
8. A method of preparing the electrode assembly according to claim 1, comprising:

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

   The dielectric material is first subjected to polarization treatment, and then the polarized dielectric material is attached to the surface of the negative electrode sheet to obtain a negative electrode dielectric layer.
9. The method for preparing an electrode assembly according to claim 8, wherein the method of polarizing the dielectric material includes: placing the dielectric material in a parallel electric field for polarization, and the parallel electric field is polarized. The field strength of the electric field is 0.1 to 6 times the coercive field strength of the dielectric material at 25°C.
10. An electrochemical device, characterized by comprising the electrode assembly according to any one of claims 1 to 7 or the electrode assembly prepared by the method according to any one of claims 8 to 9.

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