Diaphragm, battery and electric equipment

Abstract

The embodiment of the invention provides a diaphragm, a battery and electric equipment. The diaphragm provided by the invention comprises a base membrane and an adhesive layer arranged on the base membrane and located on at least one side surface of the base membrane, and the edge area of the adhesive layer is composed of an organic polymer and a lithium salt. According to the invention, the ionic conductivity of the edge of the diaphragm can be improved and the edge impedance can be reduced by utilizing the additional lithium salt provided by the adhesive layer at the edge of the diaphragm, so that the consumption speed of an electrolyte in an edge region is reduced, the liquid retention capability of the diaphragm is improved, the problem of lithium precipitation at the edge of the battery is effectively relieved, and the safety and cycle performance of the battery are improved.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and in particular to a diaphragm, a battery and an electrical device. Background Art

[0002] At present, during the charging and discharging process of lithium-ion batteries, the current density and temperature rise in the edge area of ​​the battery's electrode (especially near the electrode ear) are larger than those in the main plane area, resulting in faster consumption of electrolyte in the edge area, which in turn increases the risk of lithium plating at the edge of the battery, affecting the safety and cycle performance of the battery.

[0003] In the prior art, by adding fluorine-containing inorganic microporous fillers at the edge of the diaphragm, the electrolyte decomposition in the edge area is suppressed, and the fluorine-containing inorganic microporous fillers are combined with the ion groups of the electrolyte to form an electrolyte-rich area in the edge area. However, the uniformity of the inorganic microporous filler in this method is difficult to control, and it may also cause insufficient electrolyte in the middle main area.

[0004] Therefore, there is an urgent need in the prior art for a technology that can effectively alleviate problems such as lithium deposition at the edge of the battery. Summary of the invention

[0005] The embodiments of the present invention provide a diaphragm, a battery and an electrical device, which can utilize the additional lithium salt provided by the glue layer at the edge of the diaphragm to improve the ionic conductivity of the edge of the diaphragm, reduce the edge impedance, and thereby reduce the consumption rate of the electrolyte in the edge area, effectively alleviating the problem of lithium deposition at the edge of the battery caused by the rapid consumption of the electrolyte in the edge area.

[0006] In a first aspect, the present invention provides a separator, comprising: a base film and a glue layer disposed on the base film and located on at least one side surface of the base film; the edge region of the glue layer is composed of an organic polymer and a lithium salt.

[0007] According to an embodiment of the present invention, the adhesive layer includes a first adhesive layer in the edge region and a second adhesive layer in the main plane region, the thickness of the first adhesive layer is greater than the thickness of the second adhesive layer; the thickness of the adhesive layer is 1-10 μm.

[0008] According to one embodiment of the present invention, the mass ratio of the lithium salt to the organic polymer is 0.04-1.

[0009] According to an embodiment of the present invention, the second adhesive layer is composed of an organic polymer.

[0010] According to an embodiment of the present invention, the organic polymer includes at least one of polyvinylidene fluoride, polyethylene oxide, polypropylene oxide, polyacrylonitrile, polyacrylate copolymer, polymethyl methacrylate, polypropylene oxide, polyvinylpyrrolidone, polyvinyl alcohol resin, polyvinyl butyral, and a copolymer of vinylidene fluoride or hexafluoropropylene.

[0011] According to an embodiment of the present invention, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(difluoromethanesulfonyl)imide, lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, or lithium tetrafluoroarsenate.

[0012] According to an embodiment of the present invention, the separator further includes a ceramic layer disposed between the base film and the adhesive layer.

[0013] According to an embodiment of the present invention, the material of the ceramic layer includes at least one of aluminum oxide and boehmite; and / or, the thickness of the ceramic layer is 1-4 μm.

[0014] According to an embodiment of the present invention, the material of the base film includes at least one of polyethylene, polypropylene, cellulose film, polyimide film, polyamide film, spandex, aramid film, or non-woven fabric; and / or, the thickness of the base film is 4-10 μm.

[0015] In a second aspect of the present invention, there is provided a battery, including: an electrode assembly composed of a negative electrode sheet, the separator according to the first aspect, and a positive electrode sheet.

[0016] In a third aspect of the present invention, there is provided an electrical device, including: a device main body and the battery according to the second aspect.

[0017] The separator, battery, and electrical device provided by the present invention. An adhesive layer with an edge region composed of an organic polymer and a lithium salt is provided on at least one surface of the base film. By utilizing the additional lithium salt provided by the adhesive layer at the edge of the separator, the ionic conductivity at the edge of the separator is increased, the edge impedance is reduced, thereby reducing the consumption rate of the electrolyte in the edge region, improving the liquid retention ability of the separator, effectively alleviating the problem of lithium deposition at the edge of the battery, and improving the safety and cycle performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1It is a schematic structural diagram of the separator provided by an embodiment of the present invention;

[0020] Figure 2 It is a schematic structural diagram of the electrode assembly provided by an embodiment of the present invention.

[0021] Explanation of reference numerals: 1 - separator; 11 - base film; 12 - ceramic layer; 13 - first adhesive layer; 14 - second adhesive layer; 2 - negative electrode sheet; 21 - negative current collector; 22 - negative electrode paste coating; 23 - negative electrode main body plane area; 24 - negative electrode thinned area; 3 - positive electrode sheet; 31 - positive current collector; 32 - positive electrode paste coating; 33 - positive electrode main body plane area; 34 - positive electrode thinned area. Detailed implementation manners

[0022] To enable those skilled in the art to better understand the solution of the present invention, the present invention will be further described in detail below. The following specific implementation manners listed are only used to describe the principles and features of the present invention, and the examples given are only used to explain the present invention, not to limit the scope of the present invention. Based on the embodiments of the present invention, all other implementation manners obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0023] Based on the above introduction of the technical background, the first aspect of the present invention provides a separator, including: a base film and an adhesive layer provided on at least one surface of the base film, and the edge region of the adhesive layer is composed of an organic polymer and a lithium salt.

[0024] According to the research of the inventor, since the current density and temperature rise at the edge region of the electrode sheet of the battery are relatively large compared with the main body plane region, the electrolyte in the battery is consumed relatively fast at the edge region, increasing the risk of lithium deposition at the battery edge. By providing an adhesive layer with an edge region composed of an organic polymer and a lithium salt outside the base film, the additional lithium salt provided by the adhesive layer at the edge of the separator can be utilized to improve the ionic conductivity at the edge of the separator, reduce the edge impedance, thereby reducing the consumption rate of the electrolyte in the edge region, improving the liquid retention ability of the separator, effectively alleviating the problem of lithium deposition at the battery edge, and improving the safety and cycle performance of the battery.

[0025] In addition, currently, in order to avoid the phenomenon of "thick edges" at the edges during the coating of the positive and negative electrode slurries, and to avoid problems such as pole roll cracking and tape breakage caused by edge bulging of the electrode sheet, it is often necessary to thin the edges of the positive and negative electrode coating areas to varying degrees during the coating process, thereby generating thinned areas at the edges of the positive and negative electrode sheets. After the positive electrode sheet - separator - negative electrode sheet are sequentially arranged and assembled into a pole group, due to the existence of the thinned areas at the edges of the positive and negative electrode sheets, there will be a phenomenon that the edge of the pole group is insufficiently pressed during the hot pressing process of the pole group due to the thickness difference between the thinned area at the edge of the electrode sheet and the main body plane area, and the adhesion between the edge of the electrode sheet and the separator is poor. Furthermore, this will lead to a decrease in the ionic conductivity at the edge of the separator, an increase in the transmission path of lithium ions at the edge of the electrode sheet, which will further increase the edge impedance and further increase the risk of lithium deposition at the edge of the battery, affecting the safety and cycle performance of the battery.

[0026] Based on this, in some embodiments, the adhesive layer includes a first adhesive layer in the edge region and a second adhesive layer in the main body plane region, and the thickness of the first adhesive layer is greater than the thickness of the second adhesive layer.

[0027] According to the further research of the inventors, by setting the thickness of the first adhesive layer in the edge region to be greater than the thickness of the second adhesive layer in the main body plane region, the first adhesive layer of the adhesive layer is matched with the thinned area at the edge of the electrode, and the second adhesive layer of the adhesive layer is matched with the main body plane area of the electrode, eliminating the thickness difference between the thinned area at the edge of the electrode sheet and the main body plane area, and thereby improving the problem of poor bonding effect between the edge of the electrode sheet and the separator caused by insufficient edge pressing of the pole group during the hot pressing process of the pole group; correspondingly, after improving the bonding effect between the edge of the electrode sheet and the separator, the ionic conductivity at the edge of the separator is also increased, the transmission path of lithium ions at the edge of the electrode sheet is shortened, the impedance of the battery cell is reduced, and further, the consumption rate of the electrolyte in the edge region is reduced, the liquid retention capacity of the separator is improved, the problem of lithium deposition at the edge of the battery is effectively alleviated, and the safety and cycle performance of the battery are improved.

[0028] It should be noted that by bonding the adhesive layer to the surface of the base film, the bonding ability of the separator can be further improved, so that the edge of the electrode sheet and the separator can be bonded together more firmly.

[0029] In some embodiments, the thickness of the adhesive layer is 1 - 10 μm. The thickness of the adhesive layer is, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or a new range is formed by selecting any two of the foregoing values, and the value taken within the new range. It should be understood that a more appropriate thickness of the adhesive layer can ensure that while fully utilizing the beneficial effects brought by the adhesive layer, the adhesive layer does not occupy too much space.

[0030] In some embodiments, the mass ratio of the lithium salt to the organic polymer is 0.04 - 1. For example, the mass ratio of the lithium salt to the organic polymer is 0.04, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 1, or any two of the foregoing values are selected to form a new range, and the values taken within the new range.

[0031] In some embodiments, the second adhesive layer is composed of an organic polymer.

[0032] In some embodiments, the organic polymer includes at least one of polyvinylidene fluoride, polyethylene oxide, polypropylene oxide, polyacrylonitrile, polyacrylate copolymer, polymethyl methacrylate, polypropylene oxide, polyvinylpyrrolidone, polyvinyl alcohol resin, polyvinyl butyral, and a copolymer of vinylidene fluoride or hexafluoropropylene.

[0033] Specifically, the organic polymer in the first adhesive layer and the second adhesive layer can be any one of polyvinylidene fluoride, polyethylene oxide, polypropylene oxide, polyacrylonitrile, polyacrylate copolymer, polymethyl methacrylate, polypropylene oxide, polyvinylpyrrolidone, polyvinyl alcohol resin, polyvinyl butyral, and a copolymer of vinylidene fluoride or hexafluoropropylene, or can be composed of any combination of any of the above substances. For example, it can be composed of a combination of two, three or more substances. In this regard, the embodiments of the present invention do not make specific limitations. Such a setting can effectively improve the versatility of the adhesive layer, so that the adhesive layer can meet various different application scenarios.

[0034] In some embodiments, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(difluoromethanesulfonyl)imide, lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, or lithium tetrafluoroarsenate.

[0035] Specifically, the lithium salt in the first adhesive layer can be any one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(difluoromethanesulfonyl)imide, lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, or lithium tetrafluoroarsenate, or can be composed of any combination of any of the above substances. For example, it can be composed of a combination of two, three or more substances. In this regard, the embodiments of the present invention do not make specific limitations. Such a setting can effectively improve the versatility of the adhesive layer, so that the adhesive layer can meet various different application scenarios.

[0036] In some embodiments, the separator further includes a ceramic layer disposed between the base film and the adhesive layer. It should be understood that the provision of the ceramic layer can improve the thermal stability of the separator, serve as a physical barrier to increase the mechanical strength of the separator, and prevent large-area contact between the positive and negative electrodes caused by the shrinkage of the separator. At the same time, the provision of the ceramic layer can also improve the puncture resistance of the battery, hinder the penetration of lithium dendrites through the separator, and prevent short circuits caused by the puncture of the separator. In addition, due to the large pores in the ceramic layer, the wettability and liquid retention performance of the separator can be further increased, thereby improving the capacity retention rate of the battery.

[0037] In some embodiments, the material of the ceramic layer includes at least one of aluminum oxide and boehmite.

[0038] Specifically, the material of the ceramic layer can be any one of aluminum oxide and boehmite, or can be composed of any combination of the above substances. For example, it can be composed of a combination of two substances. In this regard, the embodiments of the present invention do not make specific limitations. Such a setting can effectively improve the versatility of the ceramic layer, enabling the ceramic layer to meet various different application scenarios.

[0039] In some embodiments, the thickness of the ceramic layer is 1-4 μm. The thickness of the ceramic is, for example, 1 μm, 1.25 μm, 1.5 μm, 1.75 μm, 2 μm, 2.25 μm, 2.5 μm, 2.75 μm, 3 μm, 3.25 μm, 3.5 μm, 3.75 μm, 4 μm, or any two of the foregoing values can be selected to form a new range, and the values taken within the new range.

[0040] In some embodiments, the material of the base film includes at least one of polyethylene, polypropylene, cellulose film, polyimide film, polyamide film, spandex, aramid film, or non-woven fabric.

[0041] Specifically, the material of the base film can be any one of polyethylene, polypropylene, cellulose film, polyimide film, polyamide film, spandex, aramid film, or non-woven fabric, or can be composed of any combination of the above substances. For example, it can be composed of a combination of two, three, or more substances. In this regard, the embodiments of the present invention do not make specific limitations. Such a setting can effectively improve the versatility of the base film, enabling the base film to meet various different application scenarios.

[0042] In some embodiments, the thickness of the base film is 4-10 μm. The base film is, for example, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, or any two of the foregoing values can be selected to form a new range, and the values taken within the new range.

[0043] A specific embodiment will be provided below to illustrate the structure of the separator provided by the present invention. Figure 1 is a schematic structural diagram of the separator provided by an embodiment of the present invention. As Figure 1 shown, the separator includes a base film 11, adhesive layers provided on both side surfaces of the base film 11 and located on the base film 11, and a ceramic layer 12 provided between the base film and the adhesive layer on one side thereof. Among them, the adhesive layer includes a first adhesive layer 13 and a second adhesive layer 14. The first adhesive layer 13 is composed of an organic polymer (not shown in the figure) and a lithium salt (not shown in the figure), and the second adhesive layer 14 is composed of an organic polymer (not shown in the figure); the thickness of the first adhesive layer is greater than the thickness of the second adhesive layer.

[0044] In the above embodiment, by using the additional lithium salt provided by the adhesive layer at the edge of the separator, the ionic conductivity at the edge of the separator is increased, the edge impedance is reduced, and further the consumption rate of the electrolyte in the edge region is reduced, the liquid retention capacity of the separator is improved, the problem of lithium deposition at the edge of the battery is effectively alleviated, and the safety and cycle performance of the battery are improved. In addition, by using the thickness difference between the first adhesive layer and the second adhesive layer, the thickness difference between the edge thinning area and the main body plane area of the electrode sheet is eliminated, and further, during the hot pressing process of the electrode assembly, the problem of poor bonding effect between the edge of the electrode sheet and the separator due to insufficient pressure on the edge of the electrode sheet is improved; correspondingly, after improving the bonding effect between the edge of the electrode sheet and the separator, the transmission path of lithium ions at the edge of the electrode sheet is shortened, the ionic conductivity at the edge of the separator is increased, the impedance of the battery cell is reduced, and further the consumption rate of the electrolyte in the edge region is reduced, the liquid retention capacity of the separator is improved, the problem of lithium deposition at the edge of the battery is effectively alleviated, and the safety and cycle performance of the battery are improved.

[0045] The second aspect of the present invention provides a battery, including: an electrode assembly composed of a negative electrode sheet, the separator provided in the first aspect above, and a positive electrode sheet. Among them, the positive electrode sheet, the separator, and the negative electrode sheet are stacked in sequence to form an electrode assembly. In addition, if only one side of the separator is provided with a ceramic layer, the side of the separator with the ceramic layer is adjacent to the positive electrode sheet, and the non-ceramic layer side of the separator is adjacent to the negative electrode sheet.

[0046] A specific embodiment will be provided below to illustrate the structure of the electrode assembly in the battery provided by the present invention. Figure 2 is a schematic structural diagram of the electrode assembly provided by an embodiment of the present invention. As Figure 2As shown in the figure, the electrode assembly includes: the separator 1 provided by the present invention, the negative electrode sheet 2, and the positive electrode sheet 3. Among them, the negative electrode sheet 2 includes a negative current collector 21 and negative electrode coatings 22 on both side surfaces of the negative current collector 21, and the negative electrode sheet 2 is divided into two parts: a negative electrode main body planar region 23 and a negative electrode thinned region 24; the positive electrode sheet 3 includes a positive current collector 31 and positive electrode coatings 32 on both side surfaces of the positive current collector 31, and the positive electrode sheet 3 is divided into two parts: a positive electrode main body planar region 33 and a positive electrode thinned region 34. It should be understood that the second adhesive layer of the separator provided by the present invention corresponds to the negative electrode main body planar region 23 / positive electrode main body planar region 33, and the first adhesive layer of the separator provided by the present invention corresponds to the negative electrode thinned region 24 / positive electrode thinned region 34.

[0047] Generally, a battery includes an electrolyte, an electrode assembly, and a housing for encapsulation. The electrolyte is injected into the electrode assembly within the housing. Among them, the electrode assembly includes a negative electrode sheet, a separator, and a positive electrode sheet.

[0048] Specifically, the negative electrode sheet includes a negative current collector and a negative electrode coating on at least one side surface of the negative current collector. Specifically, a negative electrode coating can be provided on one side surface of the negative current collector, or negative electrode coatings can be respectively provided on opposite side surfaces in the thickness direction of the negative current collector.

[0049] Specifically, the negative electrode coating (negative electrode active material layer) may include a negative electrode active material, a conductive agent, and a binder, all of which can be conventional materials in the art. For example, the negative electrode active material may include at least one of graphite, hard carbon, soft carbon, mesophase carbon microspheres, silicon-based negative electrode materials (mainly including silicon monoxide, silicon-carbon negative electrodes), tin-based negative electrode materials (mainly including tin, tin alloys), etc.; the conductive agent may include one or more of conductive carbon black, carbon nanotubes (CNT), acetylene black, graphene, Ketjen black, carbon fiber; the binder may include one or more of sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyvinyl alcohol, sodium polyacrylate.

[0050] In the battery provided by the present invention, a conventional negative current collector in the art can be used. For example, the negative current collector includes copper foil.

[0051] In the battery provided by the present invention, the negative electrode sheet can be prepared by a conventional method in the art. For example, it can be prepared by a coating method. Specifically, components for forming the negative electrode coating such as the negative electrode active material, the conductive agent, and the binder can be dispersed in a second solvent. The second solvent includes, for example, water, to prepare a negative electrode slurry, and then it is coated on the surface of the negative current collector and dried, rolled, and other processes are carried out to obtain the negative electrode sheet.

[0052] In the battery provided by the present invention, the electrolyte can be a conventional electrolyte in the art. For example, the electrolyte is a non-aqueous electrolyte, which specifically may include an organic solvent, an additive, and an electrolyte salt. The organic solvent may include, for example, one or more of ethylene carbonate (EC), diethyl carbonate (DEC), and propylene carbonate (PC). The additive may include, for example, fluoroethylene carbonate (FEC). The electrolyte salt may include a lithium salt, and the lithium salt may include, for example, lithium hexafluorophosphate (LiPF6), etc., but is not limited thereto.

[0053] In the embodiments of the present invention, a conventional housing material in the art can be used to encapsulate the electrode assembly. The housing may include, for example, a soft packaging material such as an aluminum-plastic film, but is not limited thereto.

[0054] The present invention can assemble components such as a positive electrode sheet, a separator, and a negative electrode sheet into a battery by a conventional method in the art. For example, the positive electrode, the separator provided by the present invention, and the negative electrode sheet can be stacked to obtain the electrode assembly provided by the present invention; then the electrode assembly is placed in a housing (outer packaging), and after conventional processes such as liquid injection (i.e., injecting the electrolyte) and encapsulation, the battery provided by the present invention is obtained.

[0055] The fourth aspect of the present invention provides an electrical device, including a device main body and the battery provided by the third aspect of the present invention. The present invention does not particularly limit the type of the electrical device, and it can be any electrical device including the battery, including but not limited to mobile phones, portable devices, laptop computers, electric bicycles, electric vehicles, electric toys, energy storage devices, etc.

[0056] The present invention will be further introduced below through specific examples.

[0057] Example 1:

[0058] Step 1: Preparation of the first adhesive solution:

[0059] Lithium hexafluorophosphate, polyvinylidene fluoride, polyethylene glycol, and sodium dodecyl sulfate are added to an N-methylpyrrolidone solvent. After being sufficiently stirred evenly by a magnetic stirrer, the first adhesive solution is obtained by filtering through a filter screen. Among them, the mass ratio of lithium hexafluorophosphate to polyvinylidene fluoride is 0.05.

[0060] Step 2: Preparation of the second adhesive solution:

[0061] Polyvinylidene fluoride, polyethylene glycol, and sodium dodecyl sulfate are added to an N-methylpyrrolidone solvent. After being sufficiently stirred evenly by a magnetic stirrer, the second adhesive solution is obtained by filtering through a filter screen.

[0062] Step 3: Preparation of the ceramic slurry:

[0063] Add boehmite, polyvinylidene fluoride, and polyethylene glycol to deionized water in sequence, disperse ultrasonically, stir evenly, and filter through a filter screen to obtain a ceramic slurry.

[0064] Step 4: Preparation of the separator:

[0065] Coat the above ceramic slurry evenly on one side of a 7-μm-thick PE base film by roll coating, with a ceramic layer thickness of 2 μm. Then, coat the first adhesive solution and the second adhesive solution on the surface of the ceramic layer simultaneously. The first adhesive solution and the second adhesive solution are coated on different regions of the ceramic layer respectively to form a first adhesive layer and a second adhesive layer. Among them, the thickness of the first adhesive layer on one side of the ceramic layer is 8 μm, and the thickness of the second adhesive layer is 3 μm. On the other side of the PE base film (the side without the ceramic layer), coat the first adhesive solution and the second adhesive solution correspondingly, and the coating regions are the same as those on the other side. Among them, the thickness of the first adhesive layer is 6 μm, and the thickness of the second adhesive layer is 3 μm. After drying, a separator is obtained, which includes a base film, a ceramic layer, a first adhesive layer, and a second adhesive layer.

[0066] Example 2:

[0067] The difference from Example 1 is that in the preparation process of the first adhesive solution in Step 1, the mass ratio of the lithium salt lithium hexafluorophosphate to polyvinylidene fluoride is adjusted to 0.4.

[0068] Example 3:

[0069] The difference from Example 1 is that in the preparation process of the first adhesive solution in Step 1, the mass ratio of the lithium salt lithium hexafluorophosphate to polyvinylidene fluoride is adjusted to 0.9.

[0070] Example 4:

[0071] The difference from Example 2 is that in the preparation process of the first adhesive solution in Step 1, the lithium salt lithium hexafluorophosphate is adjusted to lithium bis(fluorosulfonyl)imide.

[0072] Example 5:

[0073] The difference from Example 2 is that in the preparation process of the first adhesive solution in Step 1, the lithium salt lithium hexafluorophosphate is adjusted to include lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

[0074] Example 6:

[0075] The difference from Example 2 is that in the preparation process of the first adhesive solution in Step 1 and the preparation process of the second adhesive solution in Step 2, polyvinylidene fluoride is adjusted to vinylidene fluoride hexafluoropropylene copolymer.

[0076] Comparative Example 1:

[0077] The difference from Example 2 is that in the preparation process of the first adhesive solution in Step 1, no lithium salt is added.

[0078] Comparative Example 2:

[0079] The difference from Comparative Example 1 lies in that during the preparation of the separator in Step 4, the thicknesses of the first adhesive layer and the second adhesive layer on the side of the PE base film with the ceramic layer, and the thicknesses of the first adhesive layer and the second adhesive layer on the other side are all 3 μm.

[0080] Specifically, the parameters in each example and comparative example are shown in Table 1:

[0081] Table 1 Parameters in Each Example and Comparative Example

[0082]

[0083] The batteries prepared from each example and comparative example were all subjected to a separator liquid retention capacity test, a lithium plating test, and a normal temperature cycle life test. The test data are shown in Table 2.

[0084] Specific performance test methods:

[0085] (1) Separator liquid retention capacity test: The fresh separator areas corresponding to the first adhesive layer and the second adhesive layer were respectively punched into separator sheets of the same size, numbered, weighed, and the data were recorded. The same type of electrolyte was taken, and at the same temperature, the separator was immersed in the electrolyte for 12 h. After taking it out, it was weighed in sequence, and the liquid absorption weight was calculated respectively to evaluate the liquid retention capacity of the separator.

[0086] (2) Normal temperature cycle performance test: In a 25°C environment, the battery cell was discharged at a constant current of 1C to 2.0V; charged at a constant current and constant voltage of 1C to 3.8V, and the cut-off current was 0.05C; discharged at a constant current of 1C to 2.0V, that is, one charge and discharge cycle test was completed. The charge and discharge cycle was repeated until the capacity retention rate was lower than 80%, and then the test was stopped, and the number of cycles was recorded.

[0087] (3) Lithium plating test: In a 25°C environment, charged at a constant current and constant voltage of 2C to 3.8V, and the cut-off current was 0.05C; discharged at a constant current of 1C to 2.0V. The above charge and discharge cycle was repeated 100 times. After the cycle ended, charged at a constant current and constant voltage of 1C to 3.8V, and the cut-off current was 0.05C to fully charge the battery. The battery was disassembled under the specified temperature and humidity environment, and the lithium plating situation on the large surface and edge of the negative electrode of the battery cell was observed.

[0088] Table 2 Test Data of the Batteries Prepared from Each Example and Comparative Example

[0089]

[0090] According to the data in Table 2, by comparing the results of the liquid retention capacity test, cycle performance test, and lithium plating test of the diaphragms in Examples 1-6 and Comparative Example 1, it is found that for the batteries prepared using the diaphragms in the examples, compared with the batteries prepared using the diaphragms in the comparative example, the liquid retention capacity of the first adhesive layer region of the diaphragm and the number of cycles at 80% capacity retention rate are both significantly improved, and no lithium plating phenomenon occurs. This indicates that the additional lithium salt provided by the adhesive layer with lithium salt included at the edge outside the base film can reduce the consumption rate of the electrolyte in the edge region, improve the liquid retention capacity of the diaphragm, effectively alleviate the problem of lithium plating at the battery edge, and improve the cycle performance of the battery.

[0091] In addition, by comparing the results of the liquid retention capacity test and cycle performance test of the diaphragms in Comparative Example 1 and Comparative Example 2, it is found that the liquid retention capacity of the first adhesive layer region of the diaphragm in Comparative Example 1 and the number of cycles at 80% capacity retention rate are both higher than those in Comparative Example 2. This indicates that by setting the thickness of the first adhesive layer of the adhesive layer to be greater than that of the second adhesive layer, the consumption rate of the electrolyte in the edge region can be reduced to a certain extent, the liquid retention capacity of the diaphragm can be improved, and the cycle performance of the battery can be improved.

[0092] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A diaphragm, characterized in that: include: A base film and an adhesive layer disposed on the base film and located on at least one side surface of the base film; The edge area of ​​the glue layer is composed of an organic polymer and a lithium salt.

2. The diaphragm according to claim 1, characterized in that The adhesive layer comprises a first adhesive layer in the edge region and a second adhesive layer in the main body plane region, and the thickness of the first adhesive layer is greater than the thickness of the second adhesive layer; The thickness of the adhesive layer is 1-10 μm.

3. The diaphragm according to claim 1 or 2, characterized in that: The mass ratio of the lithium salt to the organic polymer is 0.04-1.

4. The diaphragm according to claim 2, characterized in that The second adhesive layer is composed of an organic polymer.

5. The diaphragm according to any one of claims 1, 2 or 4, characterized in that: The organic polymer includes at least one of polyvinylidene fluoride, polyethylene oxide, polypropylene oxide, polyacrylonitrile, polyacrylate copolymer, polymethyl methacrylate, polypropylene oxide, polyvinyl pyrrolidone, polyvinyl alcohol resin, polyvinyl butyral and vinylidene fluoride or hexafluoropropylene copolymer.

6. The diaphragm according to any one of claims 1, 2 or 4, characterized in that: The lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(difluoromethanesulfonyl)imide, lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate or lithium tetrafluoroarsenate.

7. The diaphragm according to any one of claims 1, 2 or 4, characterized in that The diaphragm further includes a ceramic layer, and the ceramic layer is arranged between the base film and the glue layer.

8. The diaphragm according to claim 7, characterized in that The material of the ceramic layer includes at least one of aluminum oxide and boehmite; and / or the thickness of the ceramic layer is 1-4 μm.

9. The diaphragm according to any one of claims 1, 2 or 4, characterized in that The material of the base film includes at least one of polyethylene, polypropylene, cellulose film, polyimide film, polyamide film, spandex, aramid film or non-woven fabric; and / or the base film has a thickness of 4-10 μm.

10. A battery, characterized in that: include: An electrode group is formed by a negative electrode sheet, the separator according to any one of claims 1 to 9, and a positive electrode sheet.

11. An electrical device, characterized in that: include: A device body and a battery as claimed in claim 10.

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