Electrochemical device and electronic device

Abstract

The invention provides an electrochemical device and an electronic device. The electrochemical device comprises a positive pole piece, a negative pole piece and an isolating membrane, the positive pole piece comprises a positive current collector and a positive material layer arranged on at least one surface of the positive current collector, and the positive material layer comprises a positive active material; a plurality of salient points are arranged on the positive pole piece at intervals, the height of each salient point is H [mu] m, H is more than or equal to 20 and less than or equal to 80, the radius of each salient point is R mm, R is more than or equal to 0.3 and less than or equal to 10, the surface area of each salient point is S mm < 2 >, S is more than or equal to 0.08 and less than or equal to 2.51, and the salient points are formed by protruding part of the positive pole piece along one side of the thickness direction. The electrochemical device comprises the structure, so that the contact area between the isolating membrane and the positive pole piece can be increased, the cohesiveness between the isolating membrane and the positive pole piece can be improved, and the probability of occurrence of a circulating diving problem can be reduced, thereby improving the cycle performance of the electrochemical device; the structural parameters of the salient points are within the application range, so that the damage of the salient points to the isolating membrane and the positive pole piece can be reduced, the risks of electrolyte leakage and internal resistance increase are reduced, the service life is prolonged, and the safety performance is improved.

Description

Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to an electrochemical device and an electronic device. Background Art

[0002] In the field of secondary battery manufacturing technology, the separator is a key component. It is located between the positive and negative electrodes of the secondary battery and plays the role of isolating the positive and negative electrodes to prevent internal short circuits in the secondary battery. However, the adhesion between the separator and the positive electrode has an important influence on the performance of the battery. If the adhesion between the separator and the positive electrode is not good, it may cause problems such as electrolyte leakage and increased internal resistance during the use of the secondary battery, thereby affecting the service life and safety of the secondary battery.

[0003] At present, the adhesion between the separator and the positive electrode is mainly improved by improving the separator material or optimizing the preparation process. For example, the surface properties of the separator are improved by adding specific additives to the positive electrode or coating the surface of the separator, making it easier to bond with the electrode; another method is to optimize the preparation process, such as thermal composite condition technology, to improve the adhesion between the electrode and the separator. Although the adhesion between the separator and the positive electrode is improved to a certain extent, there are still some problems and limitations. The existing technical solutions may increase the internal resistance of the secondary battery and reduce the energy density of the secondary battery. Therefore, it is urgent to solve the cycle performance problem caused by the poor adhesion between the positive electrode and the separator in the secondary battery. Summary of the invention

[0004] The purpose of the present application is to provide an electrochemical device and an electronic device to improve the adhesion between the positive electrode plate and the separator, reduce the internal resistance, and improve the cycle performance of the electrochemical device.

[0005] It should be noted that in the invention content of this application, lithium-ion batteries are used as an example of secondary batteries to explain this application, but the secondary batteries of this application are not limited to lithium-ion batteries. The specific technical solutions are as follows:

[0006] The first aspect of the present application provides an electrochemical device, which includes a positive electrode sheet, a negative electrode sheet and a separator, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer arranged on at least one surface of the positive electrode current collector, the positive electrode material layer includes a positive electrode active material; the positive electrode sheet is provided with a plurality of convex points at intervals, the height of the convex points is H μm, 20≤H≤80, the radius of the convex points is R mm, 0.3≤R≤10, and the surface area of ​​the convex points is S mm 2, 0.08≤S≤2.51, the convex point is formed by the protrusion of part of the positive electrode sheet along one side in the thickness direction. The electrochemical device includes the above structure, which can increase the contact area between the separator and the positive electrode sheet, improve the bonding force between the separator and the positive electrode sheet, reduce the probability of the cycle diving problem, and improve the cycle performance of the electrochemical device; the structural parameters of the convex point are within the scope of this application, which can reduce the damage caused by the convex point to the separator and the positive electrode sheet, reduce the risk of electrolyte leakage and increased internal resistance, and improve the service life and safety performance of the electrochemical device.

[0007] In one embodiment of the present application, 0.3≤R≤8. By adjusting the radius of the bump within the scope of the present application, the cycle performance, service life and safety performance of the electrochemical device are further improved.

[0008] In one embodiment of the present application, the spacing between two adjacent protrusions is L mm, 0.5 mm ≤ L ≤ 4 mm. By adjusting the spacing L between two adjacent protrusions within the scope of the present application, the damage caused by the protrusions to the separator and the positive electrode sheet is reduced, and the positive electrode sheet has sufficient strength, the risk of electrolyte leakage is reduced, and the service life and safety performance of the electrochemical device are further improved; the contact area between the separator and the positive electrode sheet is increased, the bonding force between the separator and the positive electrode sheet is improved, the probability of the cycle jump problem is reduced, and the cycle performance of the electrochemical device is further improved.

[0009] In one embodiment of the present application, the isolation membrane includes a base membrane, a ceramic layer and a bonding layer, the ceramic layer is located between the base membrane and the bonding layer, and the thickness of the bonding layer is hμm, 0.7≤h / S≤40. By regulating the thickness h of the bonding layer within the scope of the present application, the liquid storage capacity of the isolation membrane can be improved, the uniformity of the electrolyte distribution can be improved, and the rigidity of the isolation membrane can be improved, thereby increasing the contact area between the isolation membrane and the positive electrode plate bumps, improving the bonding force between the isolation membrane and the positive electrode plate, and further improving the cycle performance and mechanical properties of the electrochemical device, and the electrochemical device has good energy density.

[0010] In one embodiment of the present application, 2≤h≤4. By adjusting the thickness h of the bonding layer within the scope of the present application, it is beneficial to improve the liquid storage capacity of the separator, improve the uniformity of electrolyte distribution, and further improve the rigidity of the separator, increase the contact area between the separator and the positive electrode sheet, improve the bonding force between the separator and the positive electrode sheet, further improve the cycle performance of the electrochemical device, and the electrochemical device has a good energy density.

[0011] In one embodiment of the present application, the material of the bonding layer is selected from at least one of polyvinylidene fluoride, acrylonitrile, methyl methacrylate or polyurethane. The material of the bonding layer is within the scope of the present application, and the bonding force between the separator and the positive electrode sheet is increased, further improving the cycle performance of the electrochemical device.

[0012] In one embodiment of the present application, the surface roughness of the separator is Ra nm, 6×S≤Ra≤200×S. By adjusting the surface roughness of the separator within the scope of the present application, the contact area between the separator and the positive electrode plate is increased, the bonding force between the two is improved, the probability of the cycle water jump problem is reduced, and the cycle performance of the electrochemical device is further improved.

[0013] In one embodiment of the present application, 10≤Ra≤20. By adjusting the surface roughness of the separator within the scope of the present application, the contact area between the separator and the positive electrode plate is increased, the bonding force between the two is improved, the probability of the cycle water jump problem is reduced, and the cycle performance of the electrochemical device is further improved.

[0014] In one embodiment of the present application, the bonding force between the positive electrode plate and the separator is FN / m, 20≤F≤30. The bonding force F between the positive electrode plate and the separator is within the scope of the present application, and the bonding between the positive electrode plate and the separator is improved, thereby reducing the probability of the cycle water jump problem, and further improving the cycle performance of the electrochemical device.

[0015] In one embodiment of the present application, the positive electrode active material is selected from at least one of lithium cobalt oxide, lithium iron phosphate or a ternary material.

[0016] The second aspect of the present application provides an electronic device, which includes the electrochemical device described in the first aspect of the present application. The electronic device includes the above structure, which can improve the cycle performance.

[0017] Beneficial effects of this application:

[0018] The present application provides an electrochemical device, which includes a positive electrode sheet, a negative electrode sheet and a separator, wherein the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode material layer includes a positive electrode active material; the positive electrode sheet is provided with a plurality of convex points at intervals, wherein the height of the convex points is H μm, 20≤H≤80, the radius of the convex points is R mm, 0.3≤R≤10, and the surface area of ​​the convex points is S mm 2 , 0.08≤S≤2.51, the convex point is formed by the protrusion of part of the positive electrode sheet along one side in the thickness direction. The electrochemical device includes the above structure, which can increase the contact area between the separator and the positive electrode sheet, improve the adhesion between the separator and the positive electrode sheet, reduce the probability of the cycle jump problem, and thus improve the cycle performance of the electrochemical device; the structural parameters of the convex point are within the scope of this application, which can reduce the damage caused by the convex point to the separator and the positive electrode sheet, reduce the risk of electrolyte leakage and increased internal resistance, and improve the service life and safety performance of the electrochemical device.

[0019] Of course, implementing any product or method of the present application does not necessarily require achieving all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and a person skilled in the art can also obtain other embodiments based on these drawings.

[0021] Figure 1 A schematic diagram of the structure of a lithium-ion battery prepared in Example 1-1 of the present application;

[0022] Figure 2 for Figure 1 A schematic diagram of the structure with a partial enlargement at the center;

[0023] Figure 3 A schematic diagram of the structure of the protrusion of the positive electrode sheet prepared in Example 1-1 of the present application;

[0024] Figure 4 This is a schematic diagram of the structure of the protrusions of the positive electrode plate prepared in Example 1-1 of the present application. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present application and the accompanying drawings to clearly and completely describe the technical solutions in the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the present application belong to the scope of protection of the present application.

[0026] It should be noted that in the specific implementation of the present application, lithium-ion batteries are used as an example of electrochemical devices to explain the present application, but the electrochemical devices of the present application are not limited to lithium-ion batteries. The specific technical solution is as follows:

[0027] The first aspect of the present application provides an electrochemical device, which includes a positive electrode sheet, a negative electrode sheet and a separator, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer arranged on at least one surface of the positive electrode current collector, the positive electrode material layer includes a positive electrode active material; the positive electrode sheet is provided with a plurality of convex points at intervals, the height of the convex points is H μm, 20≤H≤80, the radius of the convex points is R mm, 0.3≤R≤10, and the surface area of ​​the convex points is S mm 2 , 0.08≤S≤2.51, the convex point is formed by part of the positive electrode sheet protruding along one side in the thickness direction. Figure 1 and Figure 2As shown, the electrochemical device includes a positive electrode sheet 10, a negative electrode sheet 11 and a separator 12, the positive electrode sheet 10 includes a positive electrode collector 103 and a positive electrode material layer 102 arranged on both surfaces of the positive electrode collector 103, the positive electrode sheet 10 is provided with a convex point 101, and the negative electrode sheet includes a negative electrode collector 113 and a negative electrode material layer 112 arranged on both surfaces of the negative electrode collector 113; Figure 3 As shown, the height H of the convex point refers to the height of the highest point of the convex point in the positive electrode sheet above the horizontal plane of the positive electrode sheet. For example, the height H of the convex point can be 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm or a range consisting of any two of them; the radius R can be 0.3mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm or a range consisting of any two of them; the surface area S can be 0.08mm 2 , 0.1mm 2 , 0.5mm 2 , 1mm 2 , 1.5mm 2 , 2mm 2 , 2.51mm 2 The electrochemical device includes the above structure, which can increase the contact area between the separator and the positive electrode, improve the bonding force between the separator and the positive electrode, reduce the probability of cycle diving problems, and improve the cycle performance of the electrochemical device; the structural parameters of the bumps are within the scope of this application, which can reduce the damage caused by the bumps to the separator and the positive electrode, reduce the risk of electrolyte leakage and increased internal resistance, and improve the service life and safety performance of the electrochemical device.

[0028] In the present application, the surface area S of the protrusion refers to the surface area formed by the protrusion of the protrusion on one side of a portion of the positive electrode sheet along the thickness direction.

[0029] In one embodiment of the present application, 0.3≤R≤8. For example, the radius R can be 0.3mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, or a range consisting of any two of the values. By adjusting the radius R of the bump within the scope of the present application, the cycle performance, service life and safety performance of the electrochemical device are further improved.

[0030] In one embodiment of the present application, the spacing between two adjacent protrusions is L mm, 0.5 mm ≤ L ≤ 4 mm. For example, the spacing L between two adjacent protrusions can be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, or a range consisting of any two of these values. Figure 4 As shown, the distance between the highest points of two adjacent protrusions is L. By adjusting the distance L between two adjacent protrusions within the scope of this application, the damage caused by the protrusions to the separator and the positive electrode sheet is reduced, and the positive electrode sheet has sufficient strength, the risk of electrolyte leakage is reduced, and the service life and safety performance of the electrochemical device are further improved; the contact area between the separator and the positive electrode sheet is increased, the bonding force between the separator and the positive electrode sheet is improved, the probability of the cycle diving problem is reduced, and the cycle performance of the electrochemical device is further improved.

[0031] In one embodiment of the present application, the isolation membrane includes a base membrane, a ceramic layer and a bonding layer, the ceramic layer is located between the base membrane and the bonding layer, and the thickness of the bonding layer is hμm, 0.7≤h / S≤40. For example, the value of h / S can be 0.7, 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40 or a range consisting of any two of the values. By regulating the thickness h of the bonding layer within the scope of the present application, the liquid storage capacity of the isolation membrane can be improved, the uniformity of the electrolyte distribution can be improved, and the rigidity of the isolation membrane can be improved, thereby increasing the contact area between the isolation membrane and the positive electrode plate bump, improving the bonding force between the isolation membrane and the positive electrode plate, and further improving the cycle performance and mechanical properties of the electrochemical device, and the electrochemical device has a good energy density.

[0032] In one embodiment of the present application, 2≤h≤4. For example, the thickness h of the bonding layer can be 2μm, 2.2μm, 2.5μm, 2.8μm, 3μm, 3.2μm, 3.5μm, 3.8μm, 4μm or a range consisting of any two of these values. By regulating the thickness h of the bonding layer within the scope of the present application, it is beneficial to improve the liquid storage capacity of the separator and improve the uniformity of the electrolyte distribution. In addition, it is beneficial to improve the stiffness of the separator, increase the contact area between the separator and the positive electrode sheet, improve the bonding force between the separator and the positive electrode sheet, further improve the cycle performance of the electrochemical device, and the electrochemical device has a good energy density.

[0033] In one embodiment of the present application, the material of the bonding layer is selected from at least one of polyvinylidene fluoride, acrylonitrile, methyl methacrylate or polyurethane. The material of the bonding layer is within the scope of the present application, and the bonding force between the separator and the positive electrode sheet is increased, further improving the cycle performance of the electrochemical device.

[0034] In some embodiments of the present application, the base film may be a nonwoven fabric or a composite film having a porous structure, and the material of the base film may include at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric or a polypropylene-polyethylene-polypropylene porous composite film may be used.

[0035] In some embodiments of the present application, a ceramic layer and an adhesive layer are provided on at least one surface of the base film. The ceramic layer is located between the base film and the adhesive layer. The above-mentioned "at least one surface" means that the ceramic layer and the adhesive layer can be provided on one surface of the base film along its own thickness direction, or on two surfaces of the base film along its own thickness direction. It should be noted that the "surface" here can be the entire area of ​​the base film surface, or it can be a partial area of ​​the base film surface. This application has no special restrictions, as long as the purpose of this application can be achieved.

[0036] In some embodiments of the present application, the ceramic layer includes ceramic particles and a ceramic layer binder. The present application has no particular restrictions on ceramic particles, for example, the ceramic particles may include at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate. The present application has no particular restrictions on the ceramic layer binder, as long as the purpose of the present application can be achieved, for example, the ceramic layer binder may include but is not limited to polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyimide, polyamide-imide, styrene-butadiene rubber or polyvinylidene fluoride.

[0037] In the present application, the thickness of the isolation film may be 4 μm to 50 μm, the thickness of the base film may be 2.5 μm to 30 μm, and the thickness of the ceramic layer may be 0.5 μm to 5 μm.

[0038] In one embodiment of the present application, the surface roughness of the separator is Ra nm, 6×S≤Ra≤200×S. For example, the surface roughness Ra of the separator can be 6S, 8S, 10S, 12S, 14S, 16S, 18S, 20S, 40S, 60S, 80S, 100S, 120S, 140S, 160S, 180S, 200S or a range consisting of any two of the values. By regulating the surface roughness of the separator within the scope of the present application, the contact area between the separator and the positive electrode plate is increased, the bonding force between the two is improved, the probability of the cycle water jump problem is reduced, and the cycle performance of the electrochemical device is further improved.

[0039] In one embodiment of the present application, 10≤Ra≤20. For example, the surface roughness Ra of the separator can be 10nm, 12nm, 14nm, 16nm, 18nm, 20nm, or a range consisting of any two of these values. By regulating the surface roughness of the separator within the scope of the present application, the contact area between the separator and the positive electrode plate is increased, the bonding force between the two is improved, the probability of the cycle water jump problem is reduced, and the cycle performance of the electrochemical device is further improved.

[0040] In one embodiment of the present application, the bonding force between the positive electrode plate and the separator is FN / m, 20≤F≤30. For example, the bonding force F between the positive electrode plate and the separator can be 20N / m, 21N / m, 22N / m, 23N / m, 24N / m, 25N / m, 26N / m, 27N / m, 28N / m, 29N / m, 30N / m, or a range consisting of any two of these values. The bonding force F between the positive electrode plate and the separator is within the scope of the present application, and the bonding between the positive electrode plate and the separator is improved, thereby reducing the probability of the cycle water jump problem and further improving the cycle performance of the electrochemical device.

[0041] In the present application, the height H and radius R of the convex point can be adjusted by adjusting the structure of the rolling device.

[0042] In the present application, the surface area S of the protrusions can be adjusted by adjusting the structure and pressure of the rolling device.

[0043] In the present application, the distance L between two adjacent protrusions can be adjusted by adjusting the structure of the rolling device.

[0044] The present application has no particular limitation on the method for adjusting the surface roughness Ra of the isolation film, as long as the purpose of the present application can be achieved. For example, the surface roughness Ra of the isolation film can be adjusted by adjusting the bonding layer material or the coating process parameters of the bonding layer.

[0045] The present application has no particular restrictions on the method for adjusting the bonding force F between the positive electrode plate and the separator, as long as the purpose of the present application can be achieved. For example, the bonding force F between the positive electrode plate and the separator can be adjusted by adjusting the height H, radius R, and surface area S of the bump.

[0046] In one embodiment of the present application, the positive electrode active material is selected from at least one of lithium cobalt oxide, lithium iron phosphate or a ternary material.

[0047] In the present application, the above-mentioned "positive electrode material layer disposed on at least one surface of the positive electrode current collector" means that the positive electrode material layer can be disposed on one surface of the positive electrode current collector along its thickness direction, or on two surfaces of the positive electrode current collector along its thickness direction. It should be noted that the "surface" here can be the entire area of ​​the surface of the positive electrode current collector, or it can be a partial area of ​​the surface of the positive electrode current collector. This application has no special restrictions, as long as the purpose of this application can be achieved.

[0048] The present application has no particular limitation on the positive electrode current collector, as long as the purpose of the present application can be achieved. For example, it may include aluminum foil, aluminum alloy foil or a composite current collector (such as an aluminum-carbon composite current collector).

[0049] The positive electrode material layer may also include a positive electrode conductor and a positive electrode binder. The present application does not particularly limit the types of positive electrode conductors and positive electrode binders, as long as the purpose of the present application can be achieved. For example, the positive electrode conductor may include but is not limited to at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metal materials or conductive polymers, and the conductive carbon black may include but is not limited to at least one of acetylene black or Ketjen black. The above-mentioned carbon nanotubes may include but are not limited to single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above-mentioned carbon fibers may include but are not limited to vapor-grown carbon fibers (VGCF) and / or nano-carbon fibers. The above-mentioned metal materials may include but are not limited to metal powders and / or metal fibers, and specifically, the metal may include but is not limited to at least one of copper, nickel, aluminum or silver. The above-mentioned conductive polymers may include but are not limited to at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene or polypyrrole.

[0050] The present application has no particular limitation on the positive electrode binder as long as the purpose of the present application can be achieved. For example, the positive electrode binder may include but is not limited to at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyimide, polyamide-imide, styrene-butadiene rubber or polyvinylidene fluoride.

[0051] In the present application, the thickness of the positive electrode current collector is 5μm to 20μm, and the thickness of the double-sided positive electrode material layer is 50μm to 120μm. Optionally, the positive electrode sheet may also include a positive electrode conductive layer, which is located between the positive electrode current collector and the positive electrode material layer. There is no particular restriction on the composition of the positive electrode conductive layer, and it can be a conductive layer commonly used in the art. The positive electrode conductive layer includes a positive electrode conductive layer conductive agent and a positive electrode conductive layer binder. The present application has no particular restrictions on the positive electrode conductive layer conductive agent and the positive electrode conductive layer binder, for example, it can be at least one of the above-mentioned positive electrode conductive agent and the above-mentioned positive electrode binder.

[0052] In the present application, the preparation process of the positive electrode sheet includes but is not limited to: mixing the positive electrode active material, the positive electrode binder, and the positive electrode conductive agent in a mass ratio of (95-98): (0.8-2): (1-3) to form a positive electrode slurry, coating the positive electrode slurry on the two surfaces of the positive electrode collector respectively and drying to form a positive electrode sheet; then using a convex point roller designed according to the convex point parameters to roll, adjusting the pressure of the rolling equipment to 15-25MPa, the temperature during rolling is room temperature, and the humidity is 5%-10%.

[0053] In the present application, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The above-mentioned "negative electrode material layer is disposed on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be disposed on one surface of the negative electrode current collector along its own thickness direction, or it can be disposed on two surfaces of the negative electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of ​​the surface of the negative electrode current collector, or it can be a partial area of ​​the surface of the negative electrode current collector. This application has no special restrictions, as long as the purpose of this application can be achieved.

[0054] The present application has no particular limitation on the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, it may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam or a composite current collector. For example, the composite current collector may be a lithium-copper composite current collector, a carbon-copper composite current collector, a nickel-copper composite current collector, a titanium-copper composite current collector, etc.

[0055] The negative electrode material layer includes a negative electrode active material. The present application has no particular limitation on the negative electrode active material as long as the purpose of the present application can be achieved. For example, the negative electrode active material may include but is not limited to natural graphite, artificial graphite, mesophase microcarbon beads, hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO 2 , spinel-structured lithiated TiO 2 -Li 4 Ti 5 O 12 Or at least one of Li-Al alloy.

[0056] In some embodiments of the present application, the negative electrode material layer may further include a negative electrode conductive agent and a negative electrode binder. The present application does not particularly limit the types of the negative electrode conductive agent and the negative electrode binder, as long as the purpose of the present application can be achieved. For example, it may be at least one of the above-mentioned positive electrode conductive agent and the above-mentioned positive electrode binder. The present application does not particularly limit the mass ratio of the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder in the negative electrode material layer. Those skilled in the art may select according to actual needs, as long as the purpose of the present application can be achieved.

[0057] The present application has no particular limitation on the thickness of the negative electrode material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the double-sided negative electrode material layer is 30 μm to 120 μm.

[0058] The present application has no particular limitation on the thickness of the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, the thickness of the negative electrode current collector is 4 μm to 15 μm.

[0059] Optionally, the negative electrode sheet may further include a negative electrode conductive layer, which is located between the negative electrode current collector and the negative electrode material layer. The present application has no particular restrictions on the composition of the negative electrode conductive layer, which may be a conductive layer commonly used in the art. For example, the negative electrode conductive layer includes a negative electrode conductive layer conductive agent and a negative electrode conductive layer binder. The present application has no particular restrictions on the negative electrode conductive layer conductive agent and the negative electrode conductive layer binder, and may be, for example, at least one of the above-mentioned positive electrode conductive agent and the above-mentioned positive electrode binder.

[0060] In the present application, the electrochemical device further includes an electrolyte, and the electrolyte includes a lithium salt and a non-aqueous solvent.

[0061] The present application has no particular restrictions on lithium salts, as long as the purpose of the present application can be achieved. For example, lithium salts may include but are not limited to lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ) lithium hexafluoroarsenate (LiAsF 6 ), lithium perchlorate (LiClO 4 ), lithium tetraphenylborate (LiB(C 6 H5) 4 ), lithium methanesulfonate (LiCH 3 SO 3 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium bis(trifluoromethanesulfonyl imide (LiN(SO 2 CF 3 ) 2 ), tris(trifluoromethylsulfonyl)methyllithium (LiC(SO 2 CF 3 ) 3 ), lithium hexafluorosilicate (LiSiF 6 ), lithium bis(oxalatoborate) (LiBOB) and lithium difluoroborate (LiF 2 The present application has no particular limitation on the content of the lithium salt in the electrolyte, as long as the purpose of the present application can be achieved.

[0062] The present application has no particular limitation on the non-aqueous solvent as long as the purpose of the present application can be achieved. For example, the non-aqueous solvent may include but is not limited to at least one of carbonate compounds, carboxylate compounds, ether compounds or other organic solvents.

[0063] The carbonate compound may include but is not limited to at least one of a linear carbonate compound, a cyclic carbonate compound or a fluorinated carbonate compound. The linear carbonate compound may include but is not limited to at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC) or methyl ethyl carbonate (MEC). The cyclic carbonate may include but is not limited to at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) or vinyl ethylene carbonate (VEC). The fluorinated carbonate compound may include, but is not limited to, at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The above-mentioned carboxylate compound may include, but is not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decalactone, valerolactone, or caprolactone. The above-mentioned ether compound may include but is not limited to at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran or tetrahydrofuran. The above-mentioned other organic solvents may include but are not limited to at least one of dimethyl sulfoxide, 1,2-dioxolane, cyclopentane, methyl cyclopentane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate or trioctyl phosphate. The present application has no particular restrictions on the content of the non-aqueous solvent in the electrolyte, as long as the purpose of the present application can be achieved.

[0064] The electrochemical device also includes a housing for accommodating a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte, as well as other components known in the field of electrochemical devices, and this application does not limit the above-mentioned other components. This application does not particularly limit the housing, and it can be a housing known in the art, as long as the purpose of this application can be achieved. For example, the housing can be a hard shell housing or a flexible shell. The material of the hard shell housing can be metal, and this application does not limit the type of metal, and a metal hard shell housing known in the art can be used, as long as the purpose of this application can be achieved. The flexible housing can be a metal plastic film, such as an aluminum plastic film, a steel plastic film, etc.

[0065] The present application does not particularly limit the type of electrochemical device, which may include any device that undergoes an electrochemical reaction. In the present application, the electrochemical device may include, but is not limited to: a lithium metal secondary battery, a lithium ion secondary battery (lithium ion battery), a lithium polymer secondary battery or a lithium ion polymer secondary battery (lithium ion polymer battery), etc.

[0066] The preparation process of the electrochemical device of the present application is well known to those skilled in the art, and the present application has no particular limitations. For example, the preparation process of the electrochemical device may include but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and winding, folding and other operations as needed to obtain an electrode assembly with a wound structure, placing the electrode assembly in a shell, injecting the electrolyte into the shell and sealing it to obtain an electrochemical device. Alternatively, stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and then fixing the four corners of the entire stacked structure with tape to obtain an electrode assembly with a stacked structure, placing the electrode assembly in a shell, injecting the electrolyte into the shell and sealing it to obtain an electrochemical device. In addition, overcurrent protection elements, guide plates, etc. may also be placed in the shell as needed to prevent pressure rise and overcharge and discharge inside the electrochemical device.

[0067] A second aspect of the present application provides an electronic device, which includes the electrochemical device described in the first aspect of the present application.

[0068] The present application does not particularly limit the type of electronic device, and it can be used for any electronic device known in the prior art. In some embodiments of the present application, the electronic device may include, but is not limited to, a laptop computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery and a lithium-ion capacitor, etc.

[0069] Example

[0070] The following examples and comparative examples are given to more specifically describe the embodiments of the present application. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0071] Test methods and equipment:

[0072] Test of bump height H, radius R, surface area S and distance L between two adjacent bumps:

[0073] The lithium-ion battery was charged to 4.5V at 2C constant current, charged to 0.05C at 4.5V constant voltage, left to stand for 5 minutes, and then discharged to 3.0V at 0.5C constant current. The lithium-ion battery was disassembled and the positive electrode sheet with a positive electrode material layer on the surface was taken out.

[0074] The positive electrode sheets of the embodiment and the comparative example were plasma cut longitudinally along the thickness direction to obtain a flat cross section, and the cross section was characterized by a Philips XL-30 field emission scanning electron microscope (SEM) at a magnification of 300 times. The height and chord length of the convex point were observed and measured under the electron microscope; according to the convex point height H and the convex point chord length, the convex point chord length is the diameter of the projection area of ​​the convex point on the electrode sheet, combined with the radius R = (4 × height H × height H + chord length × chord length) / (8 × height H), the radius of the spherical convex point was calculated, which was recorded as the radius R;

[0075] The positive electrode sheets of the embodiment and the comparative example were plasma cut longitudinally along the thickness direction to obtain a flat cross section, and the cross section was characterized by using a Philips XL-30 field emission SEM with a magnification of 300 times. The spacing L between two adjacent convex points was observed and measured under the electron microscope;

[0076] According to the calculation formula of the spherical crown surface area S = 2 × π × R × H / 1000, based on the measured convex point radius and convex point height, the convex point surface area S (mm 2 ).

[0077] Test of thickness h of the isolation film bonding layer:

[0078] The lithium-ion battery was charged to 4.5V at a constant current of 2C, charged to 0.05C at a constant voltage of 4.5V, left to stand for 5 minutes, and then discharged to 3.0V at a constant current of 0.5C. The lithium-ion battery was disassembled, and the separator, positive electrode sheet, and negative electrode sheet were immersed in DMC for 30 minutes, ultrasonically cleaned for 10 minutes, and the separator was removed.

[0079] The isolation membranes of the embodiments and comparative examples were plasma cut longitudinally along the thickness direction to obtain a flat cross section, and the cross section was characterized using a Philips XL-30 field emission SEM with a magnification of 300 times. The thickness of the bonding layer of the isolation membrane was observed and measured under an electron microscope, and the measurements were taken at multiple locations and the average value was taken.

[0080] Isolation film surface roughness Ra test:

[0081] The lithium-ion battery was charged to 4.5V at 2C constant current, charged to 0.05C at 4.5V constant voltage, left to stand for 5 minutes, and discharged to 3.0V at 0.5C constant current. The lithium-ion battery was disassembled, and the separator, positive electrode sheet, and negative electrode sheet were immersed in DMC for 30 minutes, ultrasonically cleaned for 10 minutes, and the separator was taken out.

[0082] Use a contact surface roughness tester to test the surface roughness Ra. Select 10 samples with a length of 150mm and a width of 10mm, place them flat on the test platform, and measure at a speed of 0.5mm / s. After the equipment test is completed, record the test data and take the average value as Ra.

[0083] Adhesion test between positive electrode and separator:

[0084] The lithium-ion battery was charged to 4.5V at 2C constant current, charged to 0.05C at 4.5V constant voltage, left to stand for 5 minutes, and discharged to 3.0V at 0.5C constant current. The lithium-ion battery was disassembled, only the negative electrode was removed, and the isolation film and positive electrode were removed to test the adhesion.

[0085] Use the 180° peel test method for pressure-sensitive adhesive tape. The specific steps are as follows:

[0086] (1) Fix the test sample on the steel plate with double-sided tape. The sample size is 70 mm in length and 20 mm in width.

[0087] (2) Affix 3M tape on the surface of the separator away from the positive electrode sheet. The tape size is 15 mm wide and 50 mm long.

[0088] (3) Use a tensile testing instrument (model: Shimadzu AGX-V2) to peel off the 3M tape 180° at a speed of 100 mm / min to obtain the bonding force between the positive electrode sheet and the isolation film in N / m.

[0089] 1000 cycles capacity retention test:

[0090] At a test environment temperature of 25°C, the lithium ion batteries prepared in the comparative example and the example are charged to 4.5V at a constant current of 2C, charged to 0.05C at a constant voltage of 4.5V, left to stand for 5 minutes, and discharged to a voltage of 3.0V at a constant current of 0.5C. The discharge capacity of the lithium ion battery at this time is recorded as C0, and left to stand for 5 minutes. This is one cycle. Repeat the above cycle for 1000 cycles, and record the discharge capacity C1 after 1000 cycles. The 1000 cycle capacity retention rate (%) = C1 / C0×100%.

[0091] Example 1

[0092] <Preparation of positive electrode sheet>

[0093] The positive electrode active material LiCoO 2, positive electrode binder polyvinylidene fluoride, positive electrode conductor Super P are mixed in a mass ratio of 97.6:1.3:1.1, Super P is acetylene black, N-methylpyrrolidone (NMP) is added as a solvent, and a slurry with a solid content of 75wt% is prepared. After vacuum stirring, the positive electrode slurry is obtained. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm, and dried at 120°C to obtain a positive electrode sheet with a single-sided coating of a positive electrode material layer. The coating weight of the positive electrode material layer is 267.8mg / 1540mm 2 . Then repeat the above steps on the other surface of the aluminum foil to obtain a positive electrode sheet coated with a positive electrode material layer on both sides. After drying at 120°C, cold press, and then use a convex roller (H=40um, R=3mm) for rolling. Adjust the pressure of the rolling equipment to 20MPa, the temperature during rolling is room temperature, and the humidity is 7.5%. Then cut and weld the pole ears to obtain a positive electrode sheet with a specification of 74mm×867mm for standby use. Among them, the thickness of the single-sided positive electrode material layer is 42μm, and the compaction density of the positive electrode sheet is 4.2g / cm 3 ; The bumps in the positive electrode are evenly distributed.

[0094] <Preparation of negative electrode sheet>

[0095] The negative electrode active material artificial graphite, the negative electrode binder styrene butadiene rubber, the thickener sodium carboxymethyl cellulose, and the conductive carbon black are mixed in a mass ratio of 98:1:0.5:0.5, the conductive carbon black is acetylene black, and deionized water is added as a solvent to prepare a slurry with a solid content of 45wt%. The negative electrode slurry is obtained after being stirred evenly by a vacuum mixer. The negative electrode slurry is evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 6μm, and dried at 120°C to obtain a negative electrode sheet with a single-sided coating of a negative electrode material layer. The coating weight of the negative electrode material layer is 142mg / 1540mm 2 Then repeat the above steps on the other surface of the copper foil to obtain a negative electrode sheet with a negative electrode material layer on both sides. After drying at 120°C, cold pressing, cutting and welding the tabs, a negative electrode sheet with a specification of 78mm×875mm is obtained for standby use. Among them, the thickness of the single-sided negative electrode material layer is 54.5μm, and the compaction density of the negative electrode sheet is 1.55g / cm 3 .

[0096] <Preparation of Electrolyte>

[0097] In an environment where the water content is less than 10 ppm, dimethyl carbonate, diethyl carbonate, and ethylene carbonate are mixed in a mass ratio of 1:1:1 to obtain an organic solvent, and then an electrolyte salt LiPF is added to the organic solvent. 6, and mixed evenly to obtain an electrolyte. The electrolyte salt has a mass percentage of 12.5% ​​based on the mass of the electrolyte, and the rest is an organic solvent.

[0098] <Isolation film>

[0099] A 10 μm thick polyethylene base film is used as the base film of the isolation film. A 5 μm thick alumina ceramic layer is coated on one surface of the base film, and then 2.5 mg / 1540.25 mm2 is coated on the surface of the alumina ceramic layer away from the base film and on the other surface of the base film. 2 The coating speed was controlled at 5 m / min and the temperature was room temperature.

[0100] <Preparation of lithium-ion batteries>

[0101] The positive electrode sheet, separator, and negative electrode sheet prepared above are stacked in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and the electrode assembly is wound. The electrode assembly is placed in an aluminum-plastic film packaging bag, and the water is removed at 80°C, and the prepared electrolyte is injected. After vacuum packaging, standing, formation, degassing, and trimming steps, a lithium-ion battery is obtained. Among them, the formation upper limit voltage is 4.52V, the formation temperature is 85°C, and the formation standing time is 2h.

[0102] Example 2 to Example 15

[0103] Except for adjusting the relevant data according to Table 1, the rest is the same as Example 1. The height H, radius R and distance L between two convex points are adjusted by adjusting the structure of the rolling device to be as shown in Table 1.

[0104] Example 16 to Example 19

[0105] Except for adjusting the coating process parameters of the isolation film adhesive layer so that the surface roughness of the isolation film surface is as shown in Table 1, the rest is the same as Example 1.

[0106] Comparative Example 1

[0107] Except that the bumps are not set in <Preparation of Positive Electrode Plate> and the relevant data are adjusted according to Table 1, the rest is the same as Example 1.

[0108] Comparative Example 2 to Comparative Example 5

[0109] Except that the height H and radius R of the protrusions are adjusted as shown in Table 1 by adjusting the structure of the rolling equipment, the rest is the same as Example 1.

[0110] The lithium ion batteries in the embodiments and comparative examples were tested, and the preparation parameters and performance parameters of the lithium ion batteries in the embodiments and comparative examples were shown in Table 1.

[0111]

[0112]

[0113] In an electrochemical device, the height H, radius R, and surface area S of the protrusions in the positive electrode sheet will affect the cycle performance of the electrochemical device. From Examples 1 to 19 and Comparative Examples 1 to 5, it can be seen that when the positive electrode sheet is provided with a plurality of protrusions at intervals and the height, radius, and area of ​​the protrusions are within the range of the present application, the obtained electrochemical device has a high 1000 cycle capacity retention rate, indicating that the cycle performance of the electrochemical device is improved.

[0114] The spacing L between two adjacent protrusions in the positive electrode sheet will affect the cycle performance of the electrochemical device. It can be seen from Examples 1, 8 and 9 that when the spacing L between two adjacent protrusions in the positive electrode sheet is within the range of the present application, the 1000-cycle capacity retention rate of the obtained electrochemical device is high, indicating that the cycle performance of the electrochemical device is improved.

[0115] The type of positive electrode active material will affect the cycle performance of the electrochemical device. It can be seen from Examples 1 and 10 that when the type of positive electrode active material is within the scope of this application, the 1000 cycle capacity retention rate of the obtained electrochemical device is high, indicating that the cycle performance of the electrochemical device is improved.

[0116] The thickness h and material of the isolation film bonding layer will affect the cycle performance of the electrochemical device. It can be seen from Examples 1 and 11 to 15 that when the thickness h and material type of the isolation film bonding layer are within the scope of this application, the 1000-cycle capacity retention rate of the obtained electrochemical device is high, indicating that the cycle performance of the electrochemical device is improved.

[0117] The value of h / S affects the cycle performance of the electrochemical device. It can be seen from Examples 1, 12 to 15 that when the value of h / S is within the range of the present application, the 1000 cycle capacity retention rate of the obtained electrochemical device is high, indicating that the cycle performance of the electrochemical device is improved.

[0118] The surface roughness Ra of the separator will affect the cycle performance of the electrochemical device. It can be seen from Examples 1 and 16 to 19 that when the surface roughness Ra of the separator is within the range of this application, the 1000-cycle capacity retention rate of the obtained electrochemical device is high, indicating that the cycle performance of the electrochemical device is improved.

[0119] The bonding force between the positive electrode sheet and the separator is affected by the height H, radius R, surface area S of the bump, the spacing L between two adjacent bumps, the thickness h of the separator bonding layer, and the surface roughness Ra of the separator. From Examples 1 to 19 and Comparative Examples 1 to 5, it can be seen that when the height H, radius R, surface area S of the bump, the spacing L between two adjacent bumps, the thickness h of the separator bonding layer, and the surface roughness Ra of the separator are within the range of this application, the bonding force between the positive electrode sheet and the separator is also within the range of this application.

[0120] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method or article including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method or article.

[0121] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0122] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. An electrochemical device comprising a positive electrode sheet, a negative electrode sheet and a separator, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode material layer comprises a positive electrode active material; The positive electrode plate is provided with a plurality of convex points at intervals, the height of the convex points is H μm, 20≤H≤80, the radius of the convex points is R mm, 0.3≤R≤10, and the surface area of ​​the convex points is S mm 2 , 0.08≤S≤2.51, the convex point is formed by a portion of the positive electrode plate protruding on one side along the thickness direction.

2. The electrochemical device according to claim 1, wherein: 0.3≤R≤8。 3. The electrochemical device according to claim 1, wherein The distance between two adjacent protrusions is L mm, 0.5 mm ≤ L ≤ 4 mm.

4. The electrochemical device according to claim 1, wherein The isolation film includes a base film, a ceramic layer and a bonding layer. The ceramic layer is located between the base film and the bonding layer. The thickness of the bonding layer is h μm, and 0.7≤h / S≤40.

5. The electrochemical device according to claim 4, wherein: 2≤h≤4。 6. The electrochemical device according to claim 4, wherein: The material of the bonding layer is selected from at least one of polyvinylidene fluoride, acrylonitrile, methyl methacrylate or polyurethane.

7. The electrochemical device according to claim 1, wherein: The surface roughness of the isolation film is Ra nm, 6×S≤Ra≤200×S.

8. The electrochemical device according to claim 7, wherein: 10≤Ra≤20.

9. The electrochemical device according to claim 1, wherein: The bonding force between the positive electrode plate and the isolation film is FN / m, 20≤F≤30.

10. The electrochemical device according to claim 1, wherein The positive electrode active material is selected from at least one of lithium cobalt oxide, lithium iron phosphate or ternary materials.

11. An electronic device comprising the electrochemical device according to any one of claims 1 to 10.

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