Battery cell and lithium-ion battery

Abstract

The application provides an electric core and a lithium ion battery. The electric core comprises a diaphragm, a positive electrode sheet and a negative electrode sheet. The diaphragm can separate the positive electrode sheet and the negative electrode sheet, and can help avoid short circuit caused by contact between the positive electrode sheet and the negative electrode sheet. The diaphragm comprises a base film, a roller coating layer and a spray coating layer. The base film has a first surface and a second surface opposite to each other. The roller coating layer is roller coated on the first surface, and the positive electrode sheet is bonded to the roller coating layer. The surface of the roller coating layer is relatively smooth, which can increase the contact area between the roller coating layer and the positive electrode sheet, help increase the bonding force between the diaphragm and the positive electrode sheet, and avoid displacement of the positive electrode sheet. The spray coating layer is sprayed on the second surface, and the negative electrode sheet is bonded to the spray coating layer. The spray coating layer can make the connection between the diaphragm and the negative electrode sheet have a porous structure, help the electrolyte fully infiltrate between the diaphragm and the electrode sheet, thereby increasing the conductivity of the diaphragm, the positive electrode sheet and the negative electrode sheet, and improving the capacity and charge-discharge performance of the lithium ion battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a battery cell and a lithium ion battery. BACKGROUND

[0002] With the rapid development of new energy vehicles, the technical requirements for power lithium ion batteries that power new energy vehicles are also increasing, mainly in high output, high capacity, and fast charging. Further, the requirements for the coating technology and process of the separator of the power lithium ion battery will also be more diversified. SUMMARY

[0003] The purpose of the present application is to provide a battery cell or a lithium ion battery to improve at least one of the above technical problems. The present application achieves the above purpose through the following technical solutions.

[0004] In a first aspect, the embodiments of the present application provide a battery cell, which comprises a separator, a positive electrode sheet and a negative electrode sheet. The separator comprises a base film, a roller coating layer and a spray coating layer. The base film has a first surface and a second surface opposite to each other. The roller coating layer is roller coated on the first surface, and the spray coating layer is sprayed on the second surface. The positive electrode sheet is bonded to the roller coating layer. The negative electrode sheet is bonded to the spray coating layer.

[0005] In an embodiment, the surface coverage of the spray coating layer on the second surface is 20% to 30%.

[0006] In an embodiment, the spray coating layer is distributed in an island structure on the second surface.

[0007] In an embodiment, the thickness of the spray coating layer is 2 μm to 4 μm.

[0008] In an embodiment, the surface coverage of the roller coating layer on the first surface is 60% to 70%.

[0009] In an embodiment, the thickness of the roller coating layer is 2 μm to 4 μm.

[0010] In an embodiment, the bonding force between the roller coating layer and the positive electrode sheet is greater than 15 N / m.

[0011] In an embodiment, the spray coating layer and the roller coating layer are both formed by a coating slurry. The coating slurry comprises ceramic particles, a bonding agent, a solvent and an additive. The mass ratio of the ceramic particles is 10% to 30%, the mass ratio of the bonding agent is 5% to 40%, the mass ratio of the solvent is 50% to 80%, and the mass ratio of the additive is less than 5%.

[0012] In an embodiment, the particle size of the ceramic particles is 0.3 μm to 2.5 μm.

[0013] In a second aspect, the embodiments of the present application further provide a lithium ion battery, which comprises a shell and the battery cell in any of the above embodiments, and the battery cell is assembled in the shell.

[0014] In the battery cell and the lithium ion battery provided by the embodiments of the present application, the battery cell comprises a separator, a positive electrode sheet and a negative electrode sheet. The separator can separate the positive electrode sheet and the negative electrode sheet, which helps to avoid short circuit caused by contact between the positive electrode sheet and the negative electrode sheet. The separator comprises a base film, a roller coating layer and a spray coating layer. The base film has a first surface and a second surface opposite to each other. The roller coating layer is coated on the first surface, and the positive electrode sheet is bonded to the roller coating layer. Since the surface of the roller coating layer is relatively flat, the contact area between the roller coating layer and the positive electrode sheet can be increased, which helps to increase the bonding force between the separator and the positive electrode sheet and avoid displacement of the positive electrode sheet. The spray coating layer is coated on the second surface, and the negative electrode sheet is bonded to the spray coating layer. The spray coating layer can make the connection between the separator and the negative electrode sheet have a porous structure, which helps to fully infiltrate the electrolyte between the separator and the electrode sheet, thereby increasing the conductivity of the separator, the positive electrode sheet and the negative electrode sheet and improving the capacity and charge-discharge performance of the lithium ion battery. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the following embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort.

[0016] Figure 1 FIG. 1 shows a structural schematic diagram of a battery cell provided by the embodiments of the present application.

[0017] Figure 2 FIG. 2 shows a structural schematic diagram of a separator of the battery cell of FIG. 1. Figure 1

[0018] Figure 3 FIG. 3 shows a structural schematic diagram of a lithium ion battery provided by the embodiments of the present application. DETAILED DESCRIPTION

[0019] The embodiments of the present application will be described in detail below, and examples of the embodiments are shown in the drawings, in which the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application.

[0020] ​In the following, the technical solutions in the embodiments of the present application will be described clearly and completely in conjunction with the accompanying drawings of the embodiments of the present application, so that those skilled in the art can better understand the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0021] At present, in the ternary cell, the separator material plays an important role, and even affects the key performance of the cell, and often needs to be coated on the front and back of the separator to obtain the desired performance.

[0022] The coating process of the separator mainly includes roll coating and spraying. The roll coating process is a commonly used coating method. The micro-gravure roller brings the slurry out of the slurry box and coats it on the separator under pressure to form a continuous coating layer. The spraying process refers to spraying the slurry onto the separator by using a rotating spray head. The separator using the spraying process can ensure that the electrolyte is fully infiltrated at the interface in the cell, but the adhesion between the electrodes is poor. The separator using the roll coating process can ensure ideal adhesion between the electrodes in the cell, but the electrolyte has insufficient infiltration ability at the interface.

[0023] In the current cell design scheme, the separator coating process is usually single, that is, the front and back are roll coated or sprayed. However, under the background of the demand for supercharging of the stacked cell, it is required that the electrodes and the separator not only have good adhesion, but also ensure the full infiltration of the electrolyte, and the single coating process cannot meet the needs of both. Based on the above reasons, the present application provides a new cell structure, which can make the separator coating compatible with the advantages of the two coating processes, and improve the charge-discharge performance and safety of the cell.

[0024] Please refer to Figures 1 to 3 The present application provides a cell 10, which can be applied to a lithium ion battery 50.

[0025] The cell 10 includes a separator 100, a positive electrode sheet 200, and a negative electrode sheet 300. The positive electrode sheet 200, the separator 100, and the negative electrode sheet 300 can be assembled integrally by winding or stacking. The separator 100 can separate the positive electrode sheet 200 and the negative electrode sheet 300, which helps to avoid short circuiting of the positive electrode sheet 200 and the negative electrode sheet 300. In addition, the separator 100 also has the function of allowing electrolyte ions to pass through.

[0026] The diaphragm 100 comprises a base film 110, a roll-coated layer 120 and a spray-coated layer 130, the base film 110 has a first surface 111 and a second surface 112 opposite to each other, the roll-coated layer 120 is roll-coated on the first surface 111, and the spray-coated layer 130 is spray-coated on the second surface 112. The positive electrode sheet 200 is bonded to the roll-coated layer 120. The negative electrode sheet 300 is bonded to the spray-coated layer 130.

[0027] In this way, the first surface 111 and the second surface 112 of the base film 110 are coated by different coating processes respectively. The roll-coated layer 120 on the first surface 111 can be roll-coated. The roll-coating process has high processing speed and precision, and is mature. In addition, the processing and maintenance of the roll are relatively simple, and the cost is relatively low. In addition, the surface of the roll-coated layer 120 is relatively flat, which can increase the contact area between the roll-coated layer 120 and the positive electrode sheet 200, thereby increasing the bonding force between the diaphragm 100 and the positive electrode sheet 200, and helping to avoid displacement of the positive electrode sheet 200. The spray-coated layer 130 on the second surface 112 can be spray-coated. The spray-coating process is suitable for a wide range of materials, is easy to operate, has a large specific surface area, high porosity, good uniformity of fiber filaments, and high yield. In addition, due to the high porosity of the spray-coated layer 130, a porous structure can be obtained at the connection between the diaphragm 100 and the negative electrode sheet 300, so that the electrolyte generates a "capillary phenomenon" through the porous structure. The electrolyte penetrates into the gap between the diaphragm 100 and the negative electrode sheet 300 under the action of the "capillary phenomenon", thereby improving the electrolyte wetting ability, which is beneficial to increasing the conductivity of lithium ions and improving the capacity and charge-discharge performance of the lithium ion battery 50.

[0028] The "capillary phenomenon" mentioned above refers to the phenomenon that the wetting liquid rises in the capillary tube and the non-wetting liquid falls in the capillary tube. For example, the vessel in the plant stem is a very fine capillary tube in the plant body, which can absorb water from the soil. For example, bricks absorb water, and towels absorb sweat, which are common "capillary phenomena".

[0029] The base film 110 can be a microporous film made of a polyolefin material, and the polyolefin material is a high molecular weight polyethylene and polypropylene, such as a polyethylene (PE) single-layer film or a polypropylene (PP) single-layer film. The polyolefin material has the advantages of high strength, good acid and alkali corrosion resistance, water resistance, chemical resistance, good biocompatibility, non-toxicity, etc., and its industrial preparation is relatively mature. For example, the base film 110 can be a PP / PE / PP multi-layer microporous film composed of PP and PE.

[0030] In addition, the base film 110 can also be a polyvinylidene difluoride (PVDF) porous film, a Polyimide (PI) electrospun porous film, and other PE and PP modified films, etc.

[0031] The preparation method of the base film 110 mainly includes a wet method and a dry method. The wet method is also called phase separation method or thermally induced phase separation (TIPS). The dry method is also called melt stretching. The purposes of the wet method and the dry method are to improve the porosity, air permeability, thermal stability, mechanical strength and the like of the separator 100. The processes of the wet method and the dry method can be referred to the prior art.

[0032] The material of the positive electrode sheet 200 can be lithium manganate, lithium cobaltate, lithium iron phosphate and ternary material or the like. The material of the negative electrode sheet 300 can be carbon material and silicon-based material or the like.

[0033] In some embodiments, the surface coverage of the spraying layer 130 on the second surface 112 can be 20% to 30%. For example, the surface coverage of the spraying layer 130 on the second surface 112 can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30% or any value between any two adjacent values in the above range. In this way, the porosity of the spraying layer 130 can be high, which helps to reduce the influence of the spraying layer 130 on the air permeability of the separator 100. In addition, the high porosity of the spraying layer 130 can also improve the wettability of the electrolyte.

[0034] In some embodiments, the spraying layer 130 can be distributed in an island structure on the second surface 112. The island structure can make the bonding part of the negative electrode sheet 300 and the separator 100 have a porous structure, improve the porosity between the negative electrode sheet 300 and the separator 100, so that the electrolyte can penetrate into the gap between the separator 100 and the negative electrode sheet 300 under the action of the "capillary phenomenon", thereby improving the wettability of the electrolyte and helping the separator 100, the positive electrode sheet 200 and the negative electrode sheet 300 to be fully wetted.

[0035] In some embodiments, the thickness of the spraying layer 130 can be 2 μm to 4 μm. For example, the thickness of the spraying layer 130 can be 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4 μm or any value between any two adjacent values in the above range. In this way, the thickness of the separator 100 can not be too thin or too thick.

[0036] Specifically, the thicker the thickness of the spray coating layer 130, the thicker the thickness of the separator 100, and thus the fewer the number of layers that the separator 100 can be wound, and accordingly, the capacity of the lithium ion battery 50 will be reduced. In addition, the thicker the thickness of the separator 100, the worse the air permeability of the separator 100 under the same porosity, resulting in an increase in the internal resistance of the lithium ion battery 50, a decrease in the energy density of the lithium ion battery 50, and thus an impact on the charge-discharge performance of the lithium ion battery 50. In addition, the thinner the thickness of the separator 100, the lower the puncture resistance, and the safety of the lithium ion battery 50 will be reduced.

[0037] In some embodiments, the surface coverage of the roll coating layer 120 on the first surface 111 is 60% to 70%. For example, the surface coverage of the roll coating layer 120 on the first surface 111 can be 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, or any value between any two adjacent values of the above, and the like. In this way, after the positive electrode sheet 200, the separator 100, and the negative electrode sheet 300 are sequentially stacked and assembled and then subjected to heat pressing treatment, the contact area between the roll coating layer 120 of the separator 100 and the positive electrode sheet 200 can be increased, which helps to make the adhesion between the separator 100 and the positive electrode sheet 200 more firm.

[0038] In some embodiments, the adhesion between the roll coating layer 120 and the positive electrode sheet 200 can be greater than 15 N / m. For example, the adhesion between the roll coating layer 120 and the positive electrode sheet 200 can be 16 N / m, 18 N / m, 20 N / m, 26 N / m, and the like. In this way, the adhesion between the separator 100 and the positive electrode sheet 200 can be made more firm, which helps to avoid displacement of the positive electrode sheet 200.

[0039] In some embodiments, the thickness of the roll coating layer 120 is 2 μm to 4 μm. In this way, the thickness of the separator 100 can not be too thin or too thick. For example, the thickness of the roll coating layer 120 can be 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4 μm, or any value between any two adjacent values of the above, and the like.

[0040] Specifically, the thicker the thickness of the roll-coated layer 120, the thicker the thickness of the separator 100, and thus the fewer the number of layers that the separator 100 can be wound, and accordingly, the capacity of the lithium ion battery 50 will be reduced. In addition, the thicker the thickness of the separator 100, the worse the air permeability of the separator 100 under the same porosity, resulting in a larger internal resistance of the lithium ion battery 50, a reduced energy density of the lithium ion battery 50, and thus an impact on the charge-discharge performance of the lithium ion battery 50. In addition, the thinner the thickness of the separator 100, the lower the puncture resistance, and the safety of the lithium ion battery 50 will be reduced.

[0041] In some embodiments, the spray-coated layer 130 and the roll-coated layer 120 can each be formed from a coating slurry including ceramic particles, a binder, a solvent, and an additive. The ceramic particles have a certain rigid support function, can make the separator 100 have excellent thermal stability and dimensional integrity at high temperatures, support the maintenance of the structure of the separator 100 at high temperatures, and improve the mechanical properties and safety of the separator 100.

[0042] The particle size of the ceramic particles is 0.3 μm to 2.5 μm. In this way, the dispersion of the ceramic particles is facilitated, and the coating slurry is made more uniform. For example, the particle size of the ceramic particles can be 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, or any value between any two adjacent values.

[0043] In the coating slurry, the mass ratio of the ceramic particles can be 10% to 30%, the mass ratio of the binder can be 5% to 40%, the mass ratio of the solvent can be 50% to 80%, and the mass ratio of the additive can be less than 5%. Generally, the higher the mass ratio of the ceramic particles, the higher the hardness and the better the thermal performance of the separator 100 after being coated on the base film 110, but too much ceramic particles will reduce the uniformity of the coating slurry and can weaken the skeleton structure of the binder, thereby possibly leading to a decrease in the mechanical properties of the separator 100.

[0044] For example, the mass ratio of the ceramic particles can be approximately 10%, the mass ratio of the binder can be approximately 5%, the mass ratio of the solvent can be approximately 80%, and the mass ratio of the additive can be approximately 5%.

[0045] For example, the mass ratio of the ceramic particles can be about 10%, the mass ratio of the binder can be about 36%, the mass ratio of the solvent can be about 50%, and the mass ratio of the additive can be about 4%.

[0046] For example, the mass ratio of the ceramic particles can be about 15%, the mass ratio of the binder can be about 15%, the mass ratio of the solvent can be about 68%, and the mass ratio of the additive can be about 2%.

[0047] For example, the mass ratio of the ceramic particles can be about 18%, the mass ratio of the binder can be about 25%, the mass ratio of the solvent can be about 54%, and the mass ratio of the additive can be about 3%.

[0048] For example, the mass ratio of the ceramic particles can be about 22%, the mass ratio of the binder can be about 14%, the mass ratio of the solvent can be about 60%, and the mass ratio of the additive can be about 4%.

[0049] For example, the mass ratio of the ceramic particles can be about 30%, the mass ratio of the binder can be about 10%, the mass ratio of the solvent can be about 57%, and the mass ratio of the additive can be about 3%.

[0050] The ceramic particles can be alumina powder, which does not need to be further ground, reducing the production steps, improving production efficiency, and making the distribution of the alumina powder in the coating slurry more uniform. The purity of the alumina powder can be greater than or equal to 99.7%. Generally speaking, the higher the percentage of the purity of the alumina powder, the higher the quality of the alumina powder, the fewer the impurities in the alumina powder, and the lower the impact of the impurities in the alumina powder on the performance of the coating slurry. In other embodiments, the ceramic particles can also be silicon dioxide, magnesium oxide, calcium oxide, etc.

[0051] In addition, when the current is too large, the alumina powder can block the current. Because the base film 110 has many micropores, when the current is too large, the phenomenon of perforation is easy to occur, which can cause the lithium-ion battery 50 to burn or even explode. When high-purity alumina powder is used as part of the material of the coating slurry together with the binder, solvent, etc. to coat the surface of the base film 110, it can effectively play a mediation role. Because the alumina powder is a plate-like crystal structure, when the alumina powder encounters a large current, the alumina powder will heat up, causing the plate-like crystal structure of the alumina powder coating material to expand in volume, thereby closing the micropores on the base film 110, thereby playing a role in blocking the current. When the temperature drops, the volume of the material will shrink, at which time the micropores on the base film 110 will be reopened. By utilizing the special physical and chemical properties of the alumina powder, the safety performance of the lithium-ion battery 50 can be improved to a certain extent.

[0052] Meanwhile, the aluminum oxide powder can also be used as a flame retardant, and the material containing the aluminum oxide powder also has flame retardant properties, which helps to reach the zero point of combustion of the lithium ion battery 50 under high temperature conditions, and the material containing the aluminum oxide powder has good flame retardant properties, thus helping to prevent the lithium ion battery 50 from burning or exploding on a large scale.

[0053] The adhesive can increase the adhesion of the base film 110 to the coating slurry, and the adhesive swells when heated, which can bond the base film 110 to the pole piece, helping to improve the hardness of the lithium ion battery 50, while also avoiding deformation of the lithium ion battery 50. The adhesive can use materials such as polyvinyl alcohol (PVA), carboxymethyl cellulose (E466), and polyvinylidene difluoride (PVDF).

[0054] The solvent can generally be an aqueous solvent and an oily solvent, where the aqueous solvent can be water, ethanol, glycerol, and other polar organic solvents, and the oily solvent can be acetone, N-methylpyrrolidone (NMP), and other non-polar solvents. In actual formulations, the use of solvents is not limited to one, and the ratio can be adjusted according to actual needs.

[0055] The additive can be used to improve the performance of the separator 100 and highlight certain specific properties, and the type and amount of the additive can be flexibly changed according to needs. For example, the additive can include a surfactant, a conductive agent, and a dispersant, etc. Among them, the surfactant can reduce the surface tension of the coating slurry and improve the affinity of the base film 110 to the coating slurry. The material of the surfactant can be a fluorocarbon surfactant, a silane surfactant, a polyol surfactant, etc. The conductive agent can enhance the conduction of lithium ions, and the material of the conductive agent can be carbon nanotubes. The dispersant can promote uniform dispersion of the coating slurry, and the material of the dispersant can be esters such as polyoxyethylene dioleate and polytetraethylene glycol monostearate, and organic salts, etc. In other embodiments, the additive can also be an organic silicon defoaming agent, a thickening agent, etc.

[0056] In some embodiments, the base film 110 can be coated with the roll coating layer 120 and then coated with the spray coating layer 130, which is affected by the roll coating process and the spray coating process. Generally, the total coating time of the roll coating layer 120 and the spray coating layer 130 is not more than 8 hours. In this way, it helps to avoid the coating slurry from coagulating due to a long standing time, which affects the performance of the coating slurry.

[0057] For example, when the coating slurry is coated on the first surface 111 and the second surface 112 of the base film 110, generally, the roll coating process can be first performed on the first surface 111 of the base film 110 to coat the roll coating layer 120 on the first surface 111. After the roll coating layer 120 is coated, the spray coating process can be performed on the second surface 112 to coat the spray coating layer 130 on the second surface 112. Generally, the total coating time of the roll coating layer 120 and the spray coating layer 130 is not more than 8 hours.

[0058] Referring to Figure 3 The embodiments of the present application also provide a lithium ion battery 50, which can be a cylindrical battery, a square battery, a soft package battery or other types. The lithium ion battery 50 comprises a shell 20 and the battery cell 10 in any of the above embodiments, and the battery cell 10 is assembled in the shell 20. Since the lithium ion battery 50 comprises the battery cell 10, the lithium ion battery 50 has all the beneficial effects of the battery cell 10, which will not be repeated here.

[0059] In the battery cell 10 and the lithium ion battery 50 provided by the present application, the battery cell 10 comprises the separator 100, the positive electrode sheet 200 and the negative electrode sheet 300. The separator 100 can separate the positive electrode sheet 200 and the negative electrode sheet 300, which helps to avoid the short circuit of the positive electrode sheet 200 and the negative electrode sheet 300. The separator 100 comprises the base film 110, the roll coating layer 120 and the spray coating layer 130. The base film 110 has the opposite first surface 111 and second surface 112. The roll coating layer 120 is roll coated on the first surface 111, and the spray coating layer 130 is spray coated on the second surface 112. The positive electrode sheet 200 is bonded to the roll coating layer 120. The negative electrode sheet 300 is bonded to the spray coating layer 130. Since the surface of the roll coating layer 120 is relatively flat, the contact area of the roll coating layer 120 and the positive electrode sheet 200 can be increased, which helps to increase the bonding force between the separator 100 and the positive electrode sheet 200, and avoid the displacement of the positive electrode sheet 200. The spray coating layer 130 can make the connection between the separator 100 and the negative electrode sheet 300 have a porous structure, which helps to make the electrolyte fully infiltrate between the separator 100 and the electrode sheet, thereby increasing the conductivity of the separator 100, the positive electrode sheet 200 and the negative electrode sheet 300, and improving the capacity and charge-discharge performance of the lithium ion battery 50.

[0060] In addition, the use of the term "some embodiments", "other embodiments", etc. does not indicate a varying level of preference for particular embodiments. The specification has specific embodiments that include specific features, structures, compositions, and methods. Each of the specific embodiments can not include all of the features, structures, compositions, and methods. If this application includes more than one embodiment, each of the embodiments can not include the same or similar features, structures, compositions, and methods. Each of the specific embodiments are not mutually exclusive, but can be independently selected because they represent distinct improvements to the technology.

[0061] The above embodiments are only used to illustrate the technical solutions of the present application, but not limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. An electric cell, characterized by, The diaphragm (100) comprises a base film (110), a roller coating layer (120) and a spray coating layer (130), the spray coating layer (130) and the roller coating layer (120) are both formed by a coating slurry, the base film (110) has a first surface (111) and a second surface (112) opposite to each other, the roller coating layer (120) is roller coated on the first surface (111), the spray coating layer (130) is spray coated on the second surface (112), the spray coating layer (130) is distributed in an island structure on the second surface (112) and has a porous structure to allow electrolyte to penetrate the diaphragm (100) by capillary action formed by the porous structure; a positive electrode sheet (200) bonded to the roller coating layer (120), the surface coverage of the roller coating layer (120) on the first surface (111) is 60% to 70%, so that the bonding force between the roller coating layer (120) and the positive electrode sheet (200) is greater than 15 N / m; and a negative electrode sheet (300) bonded to the spray coating layer (130). The surface coverage of the spray coating layer (130) on the second surface (112) is 20% to 30%. The thickness of the spray coating layer (130) is 2 μm to 4 μm.

2. The electric cell of claim 1, wherein, The thickness of the roller coating layer (120) is 2 μm to 4 μm.

3. The electric cell of claim 1, wherein, The coating slurry comprises ceramic particles, a bonding agent, a solvent and an additive, the mass ratio of the ceramic particles is 10% to 30%, the mass ratio of the bonding agent is 5% to 40%, the mass ratio of the solvent is 50% to 80%, and the mass ratio of the additive is less than 5%.

4. The electric cell of claim 1, wherein, The particle size of the ceramic particles is 0.3 μm to 2.5 μm.

5. The electric cell of claim 1, wherein, The shell (20); and 6. The electric cell of claim 5, wherein, The electric core (10) according to any one of claims 1 to 6 is assembled in the shell (20).

7. A lithium-ion battery, characterized by ​ ​ ​ ​

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