Separator and secondary battery

Abstract

The embodiment of the invention provides a diaphragm and a secondary battery. The diaphragm comprises a base film layer, one surface of the base film layer is provided with an inorganic ceramic layer, and the other surface of the base film layer is provided with a linear binder; the thickness of each linear binder is D2, the width of each linear binder is W2, D2 is greater than or equal to 1 mu m and less than or equal to 5 mu m, and W2 is greater than or equal to 20 mu m and less than or equal to 400 mu m. When the diaphragm is used in the secondary battery, the cycle performance of the secondary battery can be improved.

Description

Technical Field

[0001] The present application relates to the field of energy storage, and in particular to a diaphragm and a secondary battery. Background Art

[0002] As a kind of energy storage equipment, secondary batteries are widely used in portable electronic products, electric vehicles, aerospace, energy storage and other fields. With the expansion of application fields, the energy density and charging rate of current secondary batteries are also increasing, but their high temperature cycle performance is still difficult to improve. Summary of the invention

[0003] The present application can provide a diaphragm and a secondary battery. When the diaphragm of the present application is used in a secondary battery, the high-temperature cycle performance of the secondary battery can be effectively improved.

[0004] In a first aspect, the present application provides a diaphragm comprising a base membrane layer, one surface of the base membrane layer being provided with an inorganic ceramic layer, and the other surface being provided with a linear adhesive; each linear adhesive has a thickness of D2 and a width of W2, 1μm≤D2≤5μm, 20μm≤W2≤400μm.

[0005] Based on the above technical solution, the inventors found that when a guide layer formed by all linear adhesives is set on one surface of the base film layer, the gaps between adjacent linear adhesives can be used as electrolyte transmission channels, which can effectively improve the electrolyte replenishment capacity, and the electrolyte can better infiltrate the diaphragm, so the high-temperature cycle performance of the secondary battery can be greatly improved. In addition, since the linear adhesive in the guide layer also has a certain viscosity, the linear adhesive can play a role in fixing the diaphragm, making the diaphragm less likely to deform, and can also improve the high-temperature cycle performance of the secondary battery to a certain extent.

[0006] In one embodiment of the present application, the diaphragm satisfies at least one of the following conditions: (1) all linear adhesives are parallel to each other; (2) the sum of the projected areas of all linear adhesives on the base film layer accounts for 10% to 30% of the area of ​​the base film layer; (3) 2μm≤D2≤4μm; (4) 150μm≤W2≤250μm; (5) the spacing between adjacent linear adhesives is 50μm to 500μm.

[0007] Based on the above embodiments, the high temperature cycle performance of the secondary battery containing the above separator will be more significantly improved.

[0008] In one embodiment of the present application, the distance between adjacent linear adhesives is more preferably 110 μm to 360 μm, which can effectively improve the high temperature cycle performance and low temperature performance of the secondary battery.

[0009] In one embodiment of the present application, a point adhesive is provided on the surface of the inorganic ceramic layer away from the base film layer, and all the point adhesives constitute a bonding layer. The longest diameter of each point adhesive is 20μm to 500μm on average. There are 20 to 150 point adhesives in any area on the surface of the bonding layer, and the area is 3470μm long and 2600μm wide.

[0010] Based on the above implementation scheme, the adhesive force distribution of the separator is more uniform. When used in a secondary battery, the purple spot lithium precipitation phenomenon of the secondary battery can be better reduced, thereby improving the high temperature cycle performance of the secondary battery.

[0011] In one embodiment of the present application, the thickness of the adhesive layer is D1, and the diaphragm satisfies at least one of the following conditions: (1) the distance between two adjacent point adhesives is 20 μm to 1000 μm; (2) the projected area of ​​all point adhesives in any region in the region accounts for 20% to 60% of the total area of ​​the region; (3) 0.2 μm ≤ D1 ≤ 4 μm; (4) 1 ≤ D2 / D1 ≤ 2.

[0012] Based on the above implementation scheme, the interface performance of the separator is better, and the high-temperature cycle performance of the secondary battery using the above separator is also better.

[0013] In one embodiment of the present application, the projection shape of the bonding point in the region is at least one of a circle, a ring, an ellipse, a square or a rectangle.

[0014] In one embodiment of the present application, the bonding layer includes a first aqueous polymer, and the polymerized monomers of the first aqueous polymer include at least two of butadiene, methyl acrylate, methyl methacrylate, styrene, butyl methacrylate, isooctyl acrylate, ethylene, propylene or vinylidene fluoride.

[0015] Based on the above technical solution, the first aqueous polymer itself has good adhesion, and when the above separator is used in a secondary battery, the high-temperature cycle performance of the secondary battery can be further improved.

[0016] In one embodiment of the present application, all of the linear adhesives constitute a guide layer, the guide layer includes a second aqueous polymer, and the monomers of the second aqueous polymer include at least two of styrene, butyl methacrylate, propylene, vinylidene fluoride or hexafluoropropylene.

[0017] Based on the above technical solution, the second aqueous polymer itself has good adhesion, and when the above separator is used in a secondary battery, the high-temperature cycle performance of the secondary battery can be further improved.

[0018] In the second aspect, the present application provides a secondary battery, which includes an electrolyte and a battery cell, wherein the battery cell is stacked with a positive electrode, the above-mentioned separator and a negative electrode in sequence along its thickness direction, and the positive electrode is arranged on the surface of the guide layer; a pole ear is also arranged at the edge of the positive electrode, and the pole ear is located on the extension line of at least part of the linear adhesive.

[0019] Based on the secondary battery of the present application, the linear binder on the conductive layer can form a through electrolyte transmission channel between the diaphragm and the positive electrode, which can effectively improve the electrolyte replenishment capacity, improve the interface performance of the positive electrode and the diaphragm, and lead to better high-temperature cycle performance of the secondary battery. In addition, since the tabs are located on the extension line of at least part of the linear binder, the electrolyte at both ends of the battery cell can be transferred to the battery cell body, extending the high-temperature cycle performance of the battery cell and reducing the risk of lithium precipitation at the end.

[0020] In one embodiment of the present application, the electrolyte transfer rate of the conductive layer is greater than the electrolyte transfer rate of the bonding layer.

[0021] In one embodiment of the present application, the electrolyte transmission rate of the bonding layer is 5 mm / min to 40 mm / min, and the electrolyte transmission rate of the guide layer is 15 mm / min to 60 mm / min.

[0022] In one embodiment of the present application, the electrolyte includes ethylene glycol diethyl cyanide and lithium tetrafluoroborate; and / or, the electrolyte includes adiponitrile and fluorobenzene.

[0023] Based on the above embodiments, the low temperature performance of the secondary battery can be significantly improved.

[0024] In one embodiment of the present application, the electrolyte includes ethylene glycol diethyl cyanide and lithium tetrafluoroborate, and the ratio of the mass content of ethylene glycol diethyl cyanide to the mass content of lithium tetrafluoroborate is 10-150 based on the total mass of the electrolyte.

[0025] In one embodiment of the present application, the ratio of the mass content of ethylene glycol diethyl cyanide to the mass content of lithium tetrafluoroborate is 30-75.

[0026] Based on the above embodiments, the low temperature performance of the secondary battery can be further improved.

[0027] In one embodiment of the present application, the electrolyte includes adiponitrile and fluorobenzene, and based on the total mass of the electrolyte, the sum of the mass content of adiponitrile and the mass content of fluorobenzene is 4.5% to 10%.

[0028] Based on the above embodiments, the low-temperature performance of the secondary battery can be further improved.

[0029] Beneficial effects of this application:

[0030] The present application provides a diaphragm and a secondary battery, wherein the diaphragm includes a base film layer, one surface of the base film layer is provided with an inorganic ceramic layer, and the other surface is provided with a guide layer, wherein a linear binder is provided in the guide layer, and each linear binder has a thickness of D2 and a width of W2, 1μm≤D2≤5μm, 20μm≤W2≤400μm. By providing a linear binder to form a guide layer, and controlling the width and thickness of the linear binder in the guide layer, an electrolyte transmission channel can be formed, which can effectively improve the electrolyte replenishment capacity. When the diaphragm of the present application is used in a secondary battery, the high temperature cycle performance of the secondary battery can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 This is a demonstration diagram of the electrolyte transmission rate test of the embodiment of the present application;

[0033] Figure 2 This is the CCD image of the bonding layer in Examples 3-4 of the present application. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of embodiments of the present application, rather than all 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. Those who do not specify specific conditions in the embodiments are carried out according to the conditions recommended by normal conditions or manufacturers. Those who do not specify the manufacturer for reagents or instruments used are conventional products that can be obtained by commercial purchase.

[0035] It should be noted that in the specific implementation manner of the present application, the present application is explained by taking a lithium-ion battery as an example of a secondary battery, but the secondary battery of the present application is not limited to a lithium-ion battery.

[0036] The inventors have discovered that in order to improve the energy density and charging rate of secondary batteries to meet usage requirements, the diaphragms, positive and negative electrodes inside the secondary batteries are all designed to be wide and thin; however, this will cause the diaphragm to deform easily, and the circulation interface of the secondary battery will also be prone to purple spot lithium precipitation, resulting in reduced safety performance of the secondary battery. Although there is currently a solution to use PCS coating in the diaphragm, this will cause the battery cell of the secondary battery to deform easily and will also deteriorate the high-temperature cycle performance of the secondary battery. Based on this, the inventors have discovered that when the diaphragm in the present application is used in a secondary battery, the high-temperature cycle performance of the secondary battery can be improved without basically affecting the circulation interface of the secondary battery. The secondary battery and diaphragm of the present application are described below:

[0037] The secondary battery of the present application comprises an electrolyte and a battery cell, wherein the battery cell comprises a positive electrode, a separator and a negative electrode in sequence along the thickness direction, and the positive electrode, the negative electrode and the separator are stacked.

[0038] Diaphragm

[0039] The diaphragm is used to isolate the positive electrode and the negative electrode to prevent the two from directly contacting and causing a short circuit. The diaphragm of the present application includes a base film layer, one surface of the base film layer is provided with an inorganic ceramic layer, and the other surface is provided with a linear adhesive. All linear adhesives constitute a guide layer, and each linear adhesive has a thickness of D2 and a width of W2, 1μm≤D2≤5μm, preferably 2μm≤D2≤4μm; 20μm≤W2≤400μm, preferably 150μm≤W2≤250μm. The width is the width of each linear adhesive in the width direction of the isolation membrane, and the length direction of the isolation membrane is the winding direction of the battery cell, and the width direction is perpendicular to the winding direction of the battery cell.

[0040] When a guide layer composed of a linear adhesive is provided in the diaphragm in the present application, the gaps between adjacent linear adhesives can be used as electrolyte transmission channels, which can effectively improve the electrolyte replenishment capacity, and the electrolyte can better infiltrate the diaphragm, improve the circulation interface of the diaphragm, and thus the high-temperature cycle performance of the secondary battery can be greatly improved. Moreover, since the evenly distributed linear adhesive also has a certain viscosity, the guide layer can play a role in fixing the diaphragm to a certain extent, making the diaphragm less likely to deform, thereby improving the high-temperature cycle performance of the secondary battery.

[0041] In some embodiments of the present application, the spacing between adjacent linear adhesives is 50μm to 500μm, preferably 110μm to 360μm; and the linear adhesives can be parallel to each other, so that the high temperature cycle performance of the secondary battery will be more significantly improved. In addition, in some embodiments of the present application, the sum of the projected areas of all linear adhesives on the base film layer accounts for 10% to 30% of the area of ​​the base film layer, which can ensure the bonding force and the dynamic performance of the battery cell. In addition, in the embodiments of the present application, the linear adhesive also has a length, but because the gap between adjacent linear adhesives is required as an electrolyte transmission channel, the electrolyte transmission channel usually needs to be the same length as the base film layer, so that the electrolyte can be better transmitted; therefore, for base film layers of the same size, the length of the linear adhesive is usually fixed and the same as the length of the base film layer.

[0042] In addition, in some embodiments of the present application, the flow-guiding layer includes a second water-based polymer; the monomers of the second water-based polymer include at least two of styrene, butyl methacrylate, propylene, vinylidene fluoride or hexafluoropropylene. The second water-based polymer itself has good bonding properties, and the main chain and side chain of the second water-based polymer can be additionally grafted with a bonding agent, which is beneficial to improving the bonding strength of the bonding layer.

[0043] In some embodiments of the present application, in order to make the strength distribution of the bonding force in each area of ​​the diaphragm surface roughly the same, a point adhesive is provided on the surface of the inorganic ceramic layer away from the base film layer, and all the point adhesives on the same surface constitute a bonding layer, and the longest diameter of each point adhesive is 20μm to 500μm on average, and can be 20μm, 50μm, 100μm, 150μm, 200μm, 240μm, 320μm, 360μm, 400μm , 450μm, 500μm or any two of the above values, preferably 200-400μm, there are 20-150 dot adhesives in any area on the surface of the adhesive layer, specifically 20, 30, 40, 55, 67, 86, 92, 100, 120, 150 or any two of the above values, preferably 40-100; the length of the area is 3470μm and the width is 2600μm. At this time, the secondary battery cycle can not only reduce the probability of the occurrence of interface purple spot lithium precipitation phenomenon, but also improve its own high temperature cycle performance.

[0044] It should be noted that the present application does not have any special restrictions on the shape of the point adhesive. Since the three-dimensional shape of the point adhesive is not intuitive enough, the present application describes the shape of the point adhesive in terms of the projection shape of the point adhesive in the region. Specifically, the projection shape of the point adhesive in the region can be at least one of a circle, annular ring, ellipse, square or rectangle. When the projection shape of the point adhesive in the region is annular ring, in some embodiments of the present application, the projection area of ​​the annular ring is x, the area of ​​the outer circle corresponding to the annular ring is y, and 10%≤x / y≤50%. It should also be noted that in the present application, the "longest diameter of the point-shaped adhesive" is also relative to the projection shape of the point-shaped adhesive in the area, which refers to the distance between the two points farthest apart in the projection shape; specifically, when the projection shape of the point-shaped adhesive is a circle, the "longest diameter" refers to the diameter of the circle; when the projection shape is a ring shape, the "longest diameter" refers to the radius of the large circle of the ring; when the projection shape is an ellipse, the "longest diameter" refers to the length of the major axis of the ellipse; when the projection shape is a square or a rectangle, the "longest diameter" refers to the length of the diagonal of the square or rectangle.

[0045] In some embodiments of the present application, in order to further improve the dynamic performance of the diaphragm, in the same bonding layer of the diaphragm, the distance between two adjacent point-shaped adhesives is 20 μm to 1000 μm, preferably 150 nm to 400 nm. In the present application, "the distance between two adjacent bonding points" refers to the distance between the projections of two adjacent bonding points, which is the distance between the closest parts of the two projections.

[0046] The present application does not have any special restrictions on the distribution of bonding points in the region. In the actual production process, based on the needs of the preparation process, the bonding points in the region are usually relatively uniform and regular, that is, the distance between two adjacent bonding points in the region is basically the same, and the projection of the bonding points in the region can form a pattern that is approximately rectangular or square; as an example, in this embodiment, the distribution of bonding points in the region is relatively uniform, and the projection of the bonding points can be arranged into a pattern that is approximately rectangular. In addition, in the specific embodiments of the present application, since there are more than one adjacent points to each bonding point, and the arrangement of the bonding points in the embodiments of the present application is relatively regular, the "distance between two adjacent bonding points" refers to the average distance, and the specific algorithm is: average distance = the sum of the distances between all two adjacent bonding points in the region / the number of bonding points in the region.

[0047] In some embodiments of the present application, in order to further enhance the surface adhesion of the diaphragm and make the diaphragm less susceptible to deformation, the projected area of ​​all bonding points in any region of the adhesive layer in the region generally accounts for 20% to 60% of the total area of ​​the region, preferably 20% to 35%.

[0048] The present application does not have any particular restrictions on the thickness of the adhesive layer. In actual use, in order to further enhance the surface adhesive force of the diaphragm and make the diaphragm less prone to deformation, the thickness D1 of the adhesive layer is usually between 0.2 μm and 4 μm, preferably 0.5 μm ≤ D1 ≤ 2 μm. Moreover, the thickness of the two adhesive layers may be the same or different, but in actual operation, in order to reduce the difficulty of the process of preparing the adhesive layer, the thickness of the two adhesive layers is usually the same.

[0049] The present application does not have any particular restriction on the thickness of the adhesive layer. In actual use, in order to further enhance the surface adhesion of the diaphragm and make the diaphragm less prone to deformation, the thickness D1 of the adhesive layer is generally between 0.2 μm and 4 μm, or 1≤D2 / D1≤2.

[0050] In addition, the present application generally adopts a coating method to prepare the guide layer and the bonding layer in the diaphragm, and the coating equipment selects one of gravure, micro-gravure, screen printing, and extrusion coating. In order to more conveniently control the binder to be linear or dot-shaped, as well as the thickness, width and spacing between adjacent linear binders of the linear binder, and the number, spacing and size of the dot-shaped binders, as an example, the screen printing coating method is used in the specific embodiment of the present application to prepare the guide layer and the bonding layer. When using this method, the binder can be changed to be linear or dot-shaped by replacing a screen printing plate of a different version, and the structural parameters of the linear binder or the dot-shaped binder can also be changed by changing the mesh of the screen printing plate.

[0051] In some embodiments of the present application, the adhesive layer includes a first water-based polymer by weight; wherein the polymerized monomers of the first water-based polymer include at least two of butadiene, methyl acrylate, methyl methacrylate, styrene, butyl methacrylate, isooctyl acrylate, ethylene, propylene or vinylidene fluoride. The first water-based polymer itself also has good adhesive properties, and the main chain and side chain of the first water-based polymer can also be additionally grafted with an adhesive, which is beneficial to improving the adhesive force of the adhesive layer. For example, acrylic acid, methyl methacrylate, butyl acrylate, octyl acrylate, isooctyl acrylate, butadiene or acrylonitrile can be grafted onto the first (or second) water-based polymer.

[0052] In addition, the present application has no particular restrictions on the material and thickness of the base film layer and the inorganic ceramic layer, as long as the purpose of the present application can be met. For example, the material of the base film layer can be at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film can be used. The inorganic ceramic layer may include 85% to 95% inorganic particles and 5% to 15% inorganic layer binder, wherein the inorganic particles include at least one of aluminum oxide, aluminum oxide, silicon dioxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zirconium oxide, zinc oxide, calcium oxide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate; the inorganic layer binder includes polyacrylate.

[0053] Since the secondary battery in the present application contains the above-mentioned diaphragm, the secondary battery in the present application has good high-temperature cycle performance. Moreover, the electrolyte transmission rate of the conductive layer in the secondary battery in the present application is greater than the electrolyte transmission rate of the bonding layer. The electrolyte transmission rate of the bonding layer is 5mm / min to 40mm / min, and the electrolyte transmission rate of the conductive layer is 15mm / min to 60mm / min.

[0054] Electrolyte

[0055] The electrolyte can transport lithium ions and electrons, ensuring the formation of a pathway inside the electrochemical device. Currently, there are also plans to reduce the purple spot lithium precipitation phenomenon in secondary batteries by changing the composition of the electrolyte, but this will lead to poor low-temperature performance of secondary batteries.

[0056] In some embodiments of the present application, in order to improve the low temperature performance of the secondary battery, the electrolyte satisfies at least one of the following conditions: (1) the electrolyte includes ethylene glycol diethyl cyanide and lithium tetrafluoroborate; (2) the electrolyte includes adiponitrile and fluorobenzene. For example, the electrolyte includes ethylene glycol diethyl cyanide and lithium tetrafluoroborate, and based on the total mass of the electrolyte, the ratio of the mass content of ethylene glycol diethyl cyanide to the mass content of lithium tetrafluoroborate is 10 to 150; more preferably, the ratio of the two is 30 to 75. Alternatively, the electrolyte includes adiponitrile and fluorobenzene, and based on the total mass of the electrolyte, the sum of the mass content of adiponitrile and the mass content of fluorobenzene is 4.5% to 10%.

[0057] positive electrode

[0058] In the present application, the positive electrode needs to be arranged on the surface of the conductive layer, and a pole ear is arranged on the edge of the positive electrode, and the pole ear is located on the extension line of at least part of the linear adhesive, so that the electrolyte at both ends of the battery cell can be transferred to the battery cell body, thereby extending the cycle performance of the battery cell and reducing the risk of lithium deposition at the end.

[0059] In addition, the positive electrode in the present application includes a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector. The "positive electrode active material layer arranged on at least one surface of the positive electrode current collector" means that the positive electrode active material layer can be arranged on one surface in the thickness direction of the positive electrode current collector, or on two surfaces in the thickness direction of the positive electrode current collector. Moreover, in the present application, the "surface of the positive electrode current collector" can be the entire area of ​​the positive electrode current collector, or it can be a partial area of ​​the positive electrode current collector. There is no special limitation in the present application, as long as the purpose of the present application can be achieved. In addition, in the present application, "the edge of the positive electrode is provided with a pole ear" means that the edge of the positive electrode current collector is provided with a pole ear.

[0060] The components of the positive electrode active material layer include a positive electrode active material, which can be any material that can reversibly embed and de-embed Li + 、Na + For example, the positive electrode active material includes but is not limited to at least one of lithium iron phosphate (LiFePO4), lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium nickel oxide, ternary materials, etc., and the ternary materials include but are not limited to LiNi x Co y Mn z O2、LiNi x Co y Al z O2, etc., and the content of Ni, Co, Mn, Al, etc. can be adjusted to ensure that x+y+z=1. For example, the ternary material can be LiNi 0.6 Co 0.2 Mn 0.2 O2、LiNi 0.88 Co 0.08 Mn 0.04 O2、LiNi 0.8 Co 0.15 Mn 0.05 O2、LiNi 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.88 Co 0.1 Mn 0.02 O2、LiNi 0.8 Co 0.15 Al 0.05 O2、LiNi 0.88 Co 0.1 Al 0.02 O2, etc.

[0061] In some embodiments of the present application, the components of the positive electrode active material layer also include a positive electrode conductive agent; the present application has no restrictions on the type of the positive electrode conductive agent, and any known conductive material can be used. Specifically, the positive electrode conductive agent includes, but is not limited to, at least one of acetylene black, Super-P and other carbon blacks, or amorphous carbon materials such as needle coke, or carbon nanotubes, or graphene, etc.

[0062] In some embodiments of the present application, the components of the positive electrode active material layer generally also contain a positive electrode binder. There is no particular restriction on the type of positive electrode binder used in the manufacture of the positive electrode active material layer. In the case of a coating method, any material that can be dissolved or dispersed in the liquid medium used in electrode manufacturing can be used. The positive electrode binder includes, but is not limited to, any one or at least two of the following: resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; rubber polymers such as styrene-butadiene rubber (SBR), nitrile rubber (NBR), fluororubber, isoprene rubber, polybutadiene rubber, and ethylene-propylene rubber; thermoplastic elastomer polymers such as styrene-butadiene-styrene block copolymers or their hydrides, ethylene-propylene-diene terpolymers (EPDM), styrene-ethylene-butadiene-ethylene copolymers, styrene-isoprene-styrene block copolymers or their hydrides; soft resin polymers such as isotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, and propylene-α-olefin copolymers; fluorine-based polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers; polymer compositions having ionic conductivity of alkali metal ions (especially lithium ions), etc.

[0063] In the positive electrode, the type of positive electrode current collector is not particularly limited, and it can be any material known to be suitable for use as a positive electrode current collector. The material of the positive electrode current collector includes, but is not limited to, metal materials such as aluminum, stainless steel, nickel plating, titanium, tantalum, and materials such as carbon cloth and carbon paper. In addition, in order to reduce the electronic contact resistance between the positive electrode current collector and the positive electrode active material layer, a conductive additive or a conductive coating may be provided on the surface of the positive electrode current collector. Conductive additives include, but are not limited to, carbon and precious metals such as gold, platinum, and silver. The conductive coating may be a mixture layer of an inorganic oxide, a conductive agent, and a positive electrode binder.

[0064] When preparing the positive electrode, the components in the positive electrode active material layer can be dissolved or dispersed in a liquid solvent to prepare a positive electrode slurry, and then the positive electrode slurry is coated on the positive electrode collector and dried to form a positive electrode active material layer on the positive electrode collector, thereby obtaining a positive electrode. When the positive electrode is prepared in this way, the solvent in the positive electrode slurry is not particularly limited, as long as it can dissolve or disperse the above components. Specifically, the solvent in the positive electrode slurry includes but is not limited to N-methylpyrrolidone (NMP), ethylene carbonate (EC), etc. In addition, when preparing the positive electrode, the components in the positive electrode active material layer can also be dry mixed to form a sheet, and then the obtained sheet is crimped to the positive electrode collector.

[0065] negative electrode

[0066] The negative electrode comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, and the components of the negative electrode active material layer include negative electrode active substances. That is, in the present application, the negative electrode active material layer can be disposed on one surface in the thickness direction of the negative electrode current collector, or on two surfaces in the thickness direction of the negative electrode current collector. Moreover, in the present application, the "surface of the negative electrode current collector" can be the entire area of ​​the negative electrode current collector, or it can be a partial area of ​​the negative electrode current collector. The present application has no special restrictions, as long as the purpose of the present application can be achieved.

[0067] The negative electrode active material layer generally contains negative electrode active materials, and the present application does not have any particular restrictions on the negative electrode active materials. Specifically, the negative electrode active material may include at least one of a carbon material or a silicon-based material. More specifically, the carbon material includes but is not limited to at least one of natural graphite, artificial graphite, mesophase microcarbon beads, hard carbon or soft carbon; the silicon-based material includes but is not limited to at least one of silicon, silicon-oxygen composite materials or silicon-carbon composite materials.

[0068] In some embodiments of the present application, the negative electrode active material layer generally further contains a negative electrode conductive agent. The present application has no particular restrictions on the type of the negative electrode conductive agent, as long as the purpose of the present application can be achieved. For example, the negative electrode conductive agent includes but is not limited to at least one of acetylene black, Ketjen black, carbon nanotubes, carbon fibers, carbon dots or graphene.

[0069] In some embodiments of the present application, the negative electrode active material layer may also contain a negative electrode binder and a thickener. The present application has no particular restrictions on the types of the negative electrode binder and the thickener, as long as the purpose of the present application can be achieved. For example, the negative electrode binder may include but is not limited to at least one of polyvinyl alcohol, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene rubber or acrylic (ester) styrene-butadiene rubber; the thickener in the negative electrode slurry may include but is not limited to at least one of sodium carboxymethyl cellulose or lithium carboxymethyl cellulose.

[0070] In the negative electrode, the material of the negative electrode current collector includes but is not limited to copper foil, aluminum foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam or a polymer substrate covered with a conductive metal, etc., and there is no special limitation in this application. Among them, the conductive metal includes but is not limited to copper, nickel or titanium, and the material of the polymer substrate includes but is not limited to at least one of polyethylene, polypropylene, ethylene propylene copolymer, polyethylene terephthalate, polyethylene naphthalate or poly(p-phenylene terephthalamide).

[0071] In addition, in the present application, there is no particular limitation on the thickness of the negative electrode current collector and the negative electrode active material layer, 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 12 μm, and the thickness of the single-sided negative electrode active material layer is 30 μm to 160 μm.

[0072] In addition, similar to the preparation of the positive electrode, when preparing the negative electrode, it can be configured into a negative electrode slurry, and then the negative electrode slurry is coated on the negative electrode current collector and dried to form a negative electrode active material layer on the negative electrode current collector to obtain the negative electrode; or the components in the negative electrode active material layer can be dry mixed to form a sheet, and then the obtained sheet is pressed onto the negative electrode current collector to form a negative electrode active material layer to obtain the negative electrode. The solvent in the negative electrode slurry includes any one of an aqueous solvent and an organic solvent. The aqueous solvent includes but is not limited to a mixed solvent of alcohol and water or water. Organic solvents include, but are not limited to, aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide, and tetrahydrofuran (THF); amides such as N-methylpyrrolidone (NMP), dimethylformamide, and dimethylacetamide; aprotic polar solvents such as hexamethylphosphoramide and dimethyl sulfoxide. In addition, in some other embodiments, when using an aqueous solvent, the components of the negative electrode slurry will also include a thickener and styrene-butadiene rubber (SBR) emulsion to slurry the negative electrode slurry, thereby adjusting the viscosity of the negative electrode slurry. The types of thickeners in the positive electrode slurry include, but are not limited to, at least one of carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and their salts.

[0073] The secondary battery of the present application can be used in electronic devices, and the purpose of the electrochemical device of the present application is not particularly limited, and it can be used in any electronic device known in the prior art. In some embodiments, the electrochemical device of the present application can be used for, but not limited to, laptop computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.

[0074] Example

[0075] The following uses lithium-ion secondary batteries as an example to provide examples and comparative examples to more specifically describe the implementation of the electrochemical device of the present application. Those skilled in the art will understand that the preparation method described in the present application is only an example, and any other suitable preparation method is within the scope of the present application.

[0076] Test methods and equipment:

[0077] Electrolyte transfer rate test:

[0078] 1. Cut the diaphragm sample into 15mm wide and 100mm long samples for later use;

[0079] 2. Fix both ends of the sample, leave the middle part hanging, and use a 1ml syringe to drop the electrolyte into the middle part of the sample (such as Figure 1 shown);

[0080] 3. Time for 1 minute and test the diffusion distance of the electrolyte along the length of the sample. Repeat three times for each sample and take the average value.

[0081] Detection of bonding point quantity:

[0082] At any position on the surface of the diaphragm, an area with a length of 3470 μm and a width of 2600 μm was selected, and the image information of the area was observed and recorded after magnification 100 times using a CCD (Charge-coupled Device) electron microscope of Keyence VHX5000. Figure 2 The CCD diagram of Example 3-4. The counting method of the bonding points in the region is as follows:

[0083] For bonding points that are not fully displayed in the area, if the portion in the selected area is less than 50% of the entire bonding points, it will not be counted in the total number. If it is equal to or greater than 50%, it will be counted as one bonding point.

[0084] Adhesion test:

[0085] The national standard GB / T 2790-1995, that is, the 180° peel test standard is adopted to test the adhesion between the separator and the positive electrode or the negative electrode. The separator and the positive electrode or the negative electrode are cut into 54.2 mm × 72.5 mm samples, the separator and the positive electrode or the negative electrode are compounded, and hot pressing is performed using a hot press. The hot pressing conditions are: temperature 85°C, pressure 1 MPa, hot pressing time 85 s (seconds), the compounded samples are cut into 15 mm × 54.2 mm strips, and the adhesion between the separator and the positive electrode or the negative electrode is tested according to the 180° peel test standard.

[0086] High temperature cycle performance test:

[0087] The secondary battery was placed in a 45°C thermostat for 30 minutes to allow the lithium-ion battery to reach a constant temperature. The secondary battery was then discharged at a constant current of 0.2C to 3V, and then rested for 5 minutes to measure the initial discharge capacity C0 of the secondary battery.

[0088] Then, charge and discharge were performed, where one charge and one discharge was counted as one cycle, and 800 cycles were performed. The discharge capacity C1 of the secondary battery after 800 cycles was measured. The charging process was as follows: (1) 3.5C constant current charging to 4.35V; (2) 3C constant current charging to 4.35V, constant voltage charging to 1.8C; (3) 1.8C constant current charging to 4.4V, constant voltage charging to 1.5C; (4) 1.5C constant current charging to 4.53V, constant voltage charging to 1.2C; (5) 1.2C constant current charging to 4.58V, constant voltage charging to 2100mA; (6) sleep for 5 minutes; (7) 0.5C constant current charging to 4.53V, constant voltage charging to 0.05C. The discharge process was as follows: 0.7C constant current discharge to 3.0V.

[0089] The capacity retention rate after 800 cycles at 45°C = C1 / C0×100%.

[0090] The higher the capacity retention rate, the better the high temperature cycle performance of the secondary battery.

[0091] Low temperature performance test:

[0092] Step 1: In an environment of 25°C, the formed secondary battery is charged and discharged for the first time. During discharge, it is discharged at a constant current of 0.2C to 3V. After that, the discharged secondary battery is allowed to stand for 5 minutes. Then, it is charged at a constant current of 0.5C to 4.53V. After that, it is charged at a constant voltage to 0.02C and allowed to stand for 60 minutes.

[0093] Step 2: Discharge at 0.2C to 2.5V, record the discharge capacity at this time, which is the discharge capacity of the first cycle of the secondary battery at 25°C, and then let it stand for 5 minutes.

[0094] Step 3: Place the secondary battery in 10℃, 0℃, -10℃, and -20℃ environments for discharge, and discharge at a constant current of 0.2C to 2.5V, and record the final discharge capacity of the secondary battery under each temperature condition. Before each discharge, this step will be charged in a 25℃ environment, and when charging, first charge at a constant current of 0.5C to 4.53V, and then charge at a constant voltage to 0.02C.

[0095] Step 4: Select the final discharge capacity of the secondary battery at -20°C, and use the following expression to calculate the low-temperature capacity retention rate of the secondary battery at -20°C:

[0096] Low-temperature capacity retention rate=(final discharge capacity of the secondary battery at -20°C / discharge capacity of the secondary battery at the first cycle at 25°C)×100%.

[0097] The greater the low-temperature capacity retention rate, the better the low-temperature performance of the secondary battery.

[0098] Example 1-1

[0099] <Preparation of Separator>

[0100] Inorganic boehmite particles with a Dv50 of 1 μm and polyacrylate are mixed in a mass ratio of 90:10 and dissolved in deionized water to form an inorganic coating slurry with a solid content of 50%. The obtained inorganic coating slurry is then evenly coated on one side of a base film layer made of polyethylene (PE) using a micro-concave coating method, and dried in an oven to obtain an inorganic ceramic layer.

[0101] 90g of the second water-based polymer particles (weight average molecular weight of 600,000, polymerized monomers are styrene and butyl methacrylate in a molar ratio of 1:1) are added to the stirrer, and then 10g of sodium carboxymethyl cellulose is added, stirred and mixed evenly, 5g of wetting agent dimethyl siloxane is added, and then deionized water is added for stirring, and the viscosity of the slurry is adjusted to 2000mPa·s~5000mPa·s, and the solid content is 5%, and the guide layer slurry is obtained. Subsequently, the above-mentioned adhesive layer slurry is evenly coated on the surface of the base film layer by screen printing, and the coating weight is 0.5g / m 2 , and then dried in an oven to form a guide layer.

[0102] <Preparation of negative electrode>

[0103] The negative electrode active materials artificial graphite, acetylene black, styrene-butadiene rubber and sodium carboxymethyl cellulose are mixed in a mass ratio of 96:1:1.5:1.5, and then deionized water is added as a solvent to prepare a negative electrode slurry with a solid content of 70%, and then a vacuum mixer is used to stir evenly. The negative electrode slurry is evenly coated on one surface of a copper foil with a thickness of 8 μm, dried at 110°C, and cold pressed to obtain a negative electrode sheet coated with a 150 μm negative electrode active material layer on one side, and then the above coating steps are repeated on the other surface of the negative electrode sheet to obtain a negative electrode sheet coated with a negative electrode active material layer on both sides. The negative electrode sheet is cut into a specification of 74 mm × 867 mm and welded to the pole ear for standby use.

[0104] <Preparation of positive electrode>

[0105] The positive electrode active materials lithium cobalt oxide, acetylene black, and polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 94:3:3, and then N-methylpyrrolidone (NMP) is added as a solvent to prepare a positive electrode slurry with a solid content of 75%, and then a vacuum mixer is used to stir evenly. The positive electrode slurry is evenly coated on one surface of an aluminum foil with a thickness of 12μm, dried at 90°C, and cold pressed to obtain a positive electrode sheet coated with a 100μm thick positive electrode active material layer on one side, and then the above steps are repeated on the other surface of the positive electrode sheet to obtain a positive electrode sheet coated with a positive electrode active material layer on both sides. The positive electrode sheet is cut into a specification of 74mm×867mm and welded to the pole ear for standby use.

[0106] <Preparation of Electrolyte>

[0107] In an environment with a water content of less than 10ppm, non-aqueous organic solvents of ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), propyl propionate (PP), and vinylene carbonate (VC) are mixed in a mass ratio of 20:30:20:28:2, and then lithium hexafluorophosphate (LiPF6) is added to the non-aqueous organic solvent to dissolve and mix evenly to obtain an electrolyte. Based on the total mass of the electrolyte, the mass content of LiPF6 is 8%.

[0108] <Preparation of Secondary Battery>

[0109] The positive electrode, separator and negative electrode prepared above are stacked in order, wherein the positive electrode contacts the current-conducting layer, the negative electrode contacts the bonding layer, and the positive electrode tab is located on at least part of the extension line of the linear binder, and then wound to obtain an electrode assembly. The electrode assembly is packed into an aluminum-plastic film packaging bag, and the moisture is removed at 80°C, and the prepared electrolyte is injected, and a secondary battery is obtained through vacuum packaging, standing, forming, shaping and other processes.

[0110] Example 1-2 to Example 1-15

[0111] Except for adjusting the thickness D2, width W2 of the linear adhesive, and the spacing between adjacent linear adhesives according to Table 1, the rest is basically the same as Example 1-1.

[0112] Comparative Examples 1 to 4

[0113] Except for adjusting the thickness D2, width W2 of the linear adhesive, and the spacing between adjacent linear adhesives according to Table 1, the rest is basically the same as Example 1-1.

[0114] Table 1

[0115]

[0116]

[0117] Note: In Table 1, D2 is the thickness of the linear adhesive, W2 is the width of the linear adhesive, the unit of the electrolyte transfer rate is mm / min, and the unit of the adhesive force is N / m. The same is true for Tables 2 to 4. In Comparative Example 4, the surface of the base film layer is completely covered by the linear adhesive, so the sum of the projected areas of the linear adhesive on the base film layer accounts for 100% of the area of ​​the base film layer.

[0118] Example 2-1 to Example 2-6

[0119] Except for changing the type of the second aqueous polymer particles according to Table 2, the rest is basically the same as Example 1-10.

[0120] Table 2

[0121]

[0122]

[0123] Example 3-1

[0124] Except for preparing the diaphragm according to the following method and adjusting the relevant parameters of the bonding layer, the remaining steps are basically the same as those of Examples 1-10:

[0125] <Preparation of Separator>

[0126] Inorganic boehmite particles with a Dv50 of 1 μm and polyacrylate are mixed in a mass ratio of 90:10 and dissolved in deionized water to form an inorganic coating slurry with a solid content of 50%. The obtained inorganic coating slurry is then evenly coated on one side of a base film layer made of polyethylene (PE) using a micro-concave coating method, and dried in an oven to obtain an inorganic ceramic layer.

[0127] 90g of the first aqueous polymer particles (weight average molecular weight of 600,000, polymerized monomers are butadiene and methyl acrylate in a molar ratio of 1:1) are added to the stirrer, and then 10g of sodium carboxymethyl cellulose is added, and the mixture is stirred and mixed evenly, 5g of dimethylsiloxane as a wetting agent is added, and then deionized water is added for stirring, and the viscosity of the slurry is adjusted to 2000mPa·s to 5000mPa·s, and the solid content is 5%, and a bonding layer slurry is obtained. Subsequently, the above bonding layer slurry is evenly coated on the surface of the inorganic ceramic layer by a micro-concave coating method, and the coating weight is 0.5g / m 2 , and then dried in an oven to form a bonding layer.

[0128] 90g of the second water-based polymer particles (weight average molecular weight of 600,000, polymerized monomers are styrene and butyl methacrylate in a molar ratio of 1:1) are added to the stirrer, and then 10g of sodium carboxymethyl cellulose is added, stirred and mixed evenly, 5g of wetting agent dimethyl siloxane is added, and then deionized water is added for stirring, and the viscosity of the slurry is adjusted to 2000mPa·s~5000mPa·s, and the solid content is 5%, and the guide layer slurry is obtained. Subsequently, the above-mentioned adhesive layer slurry is evenly coated on the surface of the base film layer by screen printing, and the coating weight is 0.5g / m 2 , and then dried in an oven to form a guide layer.

[0129] Example 3-2 to Example 3-21

[0130] Except for adjusting the relevant preparation parameters of the electrolyte according to Table 3, the rest is basically the same as Example 4-1.

[0131] Table 3

[0132]

[0133]

[0134] Example 4-1

[0135] Except for preparing the electrolyte according to the following method, the remaining steps are basically the same as those of Example 1-10:

[0136] <Preparation of Electrolyte>

[0137] In an argon atmosphere glove box with a water content of less than 10 ppm, non-aqueous organic solvents EC, DEC, PC, PP, and VC were mixed in a mass ratio of 20:30:20:28:2 to prepare a base solvent, and then LiPF6, ethylene glycol diethyl cyanoether, and lithium tetrafluoroborate were added to form an electrolyte. Based on the total mass of the electrolyte, the mass content of LiPF6 was 8%, the mass content of ethylene glycol diethyl cyanoether and lithium tetrafluoroborate was shown in Table 4, and the remainder was the base solvent.

[0138] Example 4-2 to Example 4-6

[0139] Except for adjusting the relevant preparation parameters of the electrolyte according to Table 4, the rest is basically the same as Example 4-1.

[0140] Embodiment 4-7

[0141] Except for preparing the electrolyte according to the following method, the remaining steps are basically the same as those of Example 1-10:

[0142] <Preparation of Electrolyte>

[0143] In an argon atmosphere glove box with a water content of less than 10 ppm, non-aqueous organic solvents EC, DEC, PC, PP, and VC were mixed in a mass ratio of 20:30:20:28:2 to prepare a basic solvent, and then lithium salt lithium hexafluorophosphate (LiPF6), adiponitrile, and fluorobenzene were added to form an electrolyte. Based on the total mass of the electrolyte, the mass content of LiPF6 was 8%, the mass contents of adiponitrile and fluorobenzene were shown in Table 4, and the remainder was the basic solvent.

[0144] Example 4-8 to Example 4-16

[0145] Except for adjusting the relevant preparation parameters of the electrolyte according to Table 4, the rest is basically the same as Example 4-8.

[0146] Table 4

[0147]

[0148]

[0149] Note: "%" is omitted in the contents of each component of the electrolyte in Table 4.

[0150] Referring to Tables 1 to 4, it can be seen from the embodiments and comparative examples that when the separator of the present application is used in a secondary battery, the high temperature cycle performance of the secondary battery can be effectively improved. In particular, when the separator of the present application contains an adhesive layer, the high temperature cycle performance of the secondary battery can be further improved. In particular, when ethylene glycol diethyl cyanide and lithium tetrafluoroborate, or adiponitrile and chlorobenzene are added to the electrolyte, the low temperature performance of the secondary battery can also be improved.

[0151] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method or article that includes a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements that are inherent to such process, method or article.

[0152] 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.

[0153] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A diaphragm, characterized in that: It includes a base film layer, one surface of which is provided with an inorganic ceramic layer, and the other surface of which is provided with a linear adhesive, and the linear adhesive constitutes a guide layer; each of the linear adhesives has a thickness of D2 and a width of W2, 1μm≤D2≤5μm, 20μm≤W2≤400μm.

2. The diaphragm according to claim 1, characterized in that It meets at least one of the following conditions: (1) The linear adhesives are parallel to each other; (2) The sum of the projected areas of all the linear adhesives on the base film layer accounts for 10% to 30% of the area of ​​the base film layer; (3) 2μm≤D2≤4μm; (4) 150μm≤W2≤250μm; (5) The distance between adjacent linear adhesives is 50 μm to 500 μm.

3. The diaphragm according to claim 1, characterized in that The surface of the inorganic ceramic layer away from the base film layer is provided with point adhesives, and all the point adhesives constitute a bonding layer. The longest diameter of each point adhesive is 20μm to 500μm on average. There are 30 to 150 point adhesives in any area on the surface of the bonding layer, and the length of the area is 3470μm and the width is 2600μm.

4. The diaphragm according to claim 3, characterized in that The thickness of the bonding layer is D1, and the diaphragm satisfies at least one of the following conditions: (1) The distance between two adjacent dot-shaped adhesives is 20 μm to 1000 μm; (2) The projection area of ​​all the dot-shaped adhesives in any of the regions in the region accounts for 20% to 60% of the total area of ​​the region; (3) 0.2μm≤D1≤4μm; (4)1≤D2 / D1≤2.

5. The diaphragm according to claim 3, characterized in that The projection shape of the point-shaped adhesive in the area is at least one of a circle, a ring, an ellipse, a square or a rectangle.

6. The diaphragm according to claim 3 or 4, characterized in that: The bonding layer includes a first water-based polymer, and monomers of the first water-based polymer include at least two of butadiene, methyl acrylate, methyl methacrylate, styrene, butyl methacrylate, isooctyl acrylate, ethylene, propylene or vinylidene fluoride.

7. The diaphragm according to any one of claims 1 to 5, characterized in that: All the linear adhesives constitute a guide layer, and the guide layer includes a second water-based polymer, and the monomers of the second water-based polymer include at least two of styrene, butyl methacrylate, propylene, vinylidene fluoride or hexafluoropropylene.

8. The diaphragm according to claim 2, characterized in that The distance between adjacent linear adhesives is 110 μm to 360 μm.

9. A secondary battery, characterized in that: It includes an electrolyte and a battery cell, wherein the battery cell is provided with a positive electrode, a separator according to any one of claims 1 to 8 and a negative electrode stacked in sequence along the thickness direction thereof, wherein the positive electrode is arranged on the surface of the conductive layer; a pole ear is also arranged at the edge of the positive electrode, and the pole ear is located on the extension line of at least part of the linear adhesive.

10. The secondary battery according to claim 9, characterized in that: The surface of the inorganic ceramic layer away from the base film layer is provided with a dot-shaped adhesive, and all the dot-shaped adhesives constitute a bonding layer. The electrolyte transmission rate of the guide layer is greater than the electrolyte transmission rate of the bonding layer.

11. The secondary battery according to claim 10, characterized in that: The electrolyte transmission rate of the bonding layer is 5 mm / min to 40 mm / min, and the electrolyte transmission rate of the guide layer is 15 mm / min to 60 mm / min.

12. The secondary battery according to claim 9, characterized in that: The electrolyte comprises ethylene glycol diethyl cyanide and lithium tetrafluoroborate; and / or, The electrolyte includes adiponitrile and fluorobenzene.

13. The secondary battery according to claim 12, characterized in that: The electrolyte includes ethylene glycol diethyl cyanide and lithium tetrafluoroborate. Based on the total mass of the electrolyte, the ratio of the mass content of the ethylene glycol diethyl cyanide to the mass content of the lithium tetrafluoroborate is 10-150.

14. The secondary battery according to claim 13, characterized in that: The ratio of the mass content of the ethylene glycol diethyl cyanide to the mass content of the lithium tetrafluoroborate is 30-75.

15. The secondary battery according to claim 12, characterized in that: The electrolyte comprises adiponitrile and fluorobenzene, and based on the total mass of the electrolyte, the sum of the mass content of adiponitrile and the mass content of fluorobenzene is 4.5% to 10%.

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