Battery cell, battery and electric device

Abstract

A battery cell, a battery and an electric device. The battery cell comprises: a casing, which has an opening; an end cover, which is used for covering the opening; an electrode terminal, which is provided on the end cover, wherein in the direction of gravity, the electrode terminal is located at the bottom of the casing; and an electrode assembly, which is accommodated in the casing. The electrode assembly comprises a positive electrode sheet, a separator and a negative electrode sheet, wherein the separator is arranged between the positive electrode sheet and the negative electrode sheet; at least one of the positive electrode sheet, the separator and the negative electrode sheet contains a gel electrolyte; the gel electrolyte comprises a lyophilic polymer and a confined electrolyte located inside the lyophilic polymer; and in the casing, the volume of free electrolyte is less than or equal to 10 mL.

Description

Battery cell, battery and power device

[0001] Related applications

[0002] The present application claims priority to the Chinese patent application No. 2024111401451, filed on August 19, 2024, entitled "Battery cell, battery and power device", the contents of which are hereby incorporated by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the technical field of battery, in particular to a battery cell, a battery and a power device. BACKGROUND

[0004] The battery such as lithium ion battery is widely used in energy storage power supply systems of hydropower, thermal power, wind power and solar power station, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. In the use process of the battery cell, it may be necessary to invert the battery cell to expand the use scenario of the battery cell. However, the end cover of the battery cell is usually welded on the shell, and the welding seam is a relatively weak position. When the battery cell is inverted, a large amount of electrolyte will be in full contact with the welding seam, at which time the electrolyte may corrode the welding seam and cause leakage. SUMMARY

[0005] The first aspect of the present application provides a battery cell, comprising: a shell, the shell having an opening;

[0006] an end cover, the end cover being used to cover the opening; an electrode terminal, the electrode terminal being provided on the end cover; in the direction of gravity, the electrode terminal is located at the bottom of the shell; an electrode assembly, the electrode assembly being accommodated in the shell;

[0007] The electrode assembly comprises a positive electrode sheet, a separator and a negative electrode sheet, the separator being provided between the positive electrode sheet and the negative electrode sheet; at least one of the positive electrode sheet, the separator and the negative electrode sheet contains a gel electrolyte; the gel electrolyte comprises a lyophilic polymer and a limiting electrolyte, the limiting electrolyte being located inside the lyophilic polymer; in the shell, the free electrolyte is less than or equal to 10 mL.

[0008] In the above battery cell, by using the gel electrolyte, the electrolyte can be limited inside the lyophilic polymer, at which time the limiting electrolyte can better play the role of the electrolyte, so that the amount of free electrolyte in the battery cell can be greatly reduced, the corrosion of the free electrolyte to the welding seam can be reduced, and the risk of leakage of the battery cell can be reduced.

[0009] In some embodiments, in the shell, the free electrolyte is less than or equal to 2 mL.

[0010] In some embodiments, the material of the shell comprises one or more of aluminum, aluminum alloy, and stainless steel. At this time, the shell has better corrosion resistance, which is conducive to further reducing the risk of liquid leakage of the battery monomer.

[0011] In some embodiments, the gel electrolyte is uniformly distributed in at least one of the positive electrode sheet, the separator film, and the negative electrode sheet. The uniform distribution of the gel electrolyte can make the contact between the limited electrolyte and at least one of the positive electrode sheet, the separator film, and the negative electrode sheet more uniform, which is conducive to further promoting the full infiltration of the electrolyte into at least one of the positive electrode sheet, the separator film, and the negative electrode sheet, and further improving the cycle performance of the battery monomer.

[0012] In some embodiments, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer located on at least one surface of the positive electrode current collector, and the positive electrode active layer contains the gel electrolyte and the positive electrode active material.

[0013] In some embodiments, the gel electrolyte is distributed on the surface of the particles of the positive electrode active material. The distribution of the gel electrolyte on the surface of the particles of the positive electrode active material can protect the particles of the active material, reduce the side reaction between the particles of the positive electrode active material and the electrolyte, and further improve the cycle performance of the battery monomer.

[0014] In some embodiments, the gel electrolyte is distributed at the pores between the particles of the positive electrode active material. At this time, more electrolyte can be confined in the positive electrode sheet, further improving the cycle performance of the battery monomer.

[0015] In some embodiments, in the positive electrode active layer, the mass percentage of the lyophilic polymer in the positive electrode active layer is 0.1% to 2%. The mass percentage of the lyophilic polymer in the positive electrode active layer in this range can make the limited electrolyte have a suitable retention amount in the positive electrode active layer, make the limited electrolyte better adapt to the positive electrode active material, and further improve the cycle performance of the battery monomer.

[0016] In some embodiments, the positive electrode active material comprises one or more of lithium nickel manganese cobalt oxide and lithium-containing phosphate; in the lithium nickel manganese cobalt oxide, the molar percentage of nickel element is 50% to 95%, and optionally 80% to 95%, in terms of the molar percentage of nickel element, manganese element, and cobalt element. The lithium nickel manganese cobalt oxide with the molar percentage of nickel element in this range has a higher gram capacity, which is conducive to further improving the energy density of the battery monomer.

[0017] In some embodiments, the density of the positive electrode active layer is 2 g / cm 3 to 3.8 g / cm 3 . The density of the positive electrode active layer in this range can make the battery monomer have a more suitable weight and a higher energy density.

[0018] In some embodiments, the positive active material comprises lithium nickel cobalt manganese oxide, and the density of the positive active layer is 3.5 g / cm 3 ~ 3.8 g / cm 3 .

[0019] In some embodiments, the positive active material comprises lithium-containing phosphate, and the density of the positive active layer is 2 g / cm 3 ~ 3 g / cm 3 .

[0020] In some embodiments, the positive current collector comprises a first support layer and a first metal layer, the first metal layer is located on at least one surface of the first support layer, and the first metal layer is located between the first support layer and the positive active layer. The positive current collector adopts the form of a composite current collector, which can reduce the weight of the positive current collector relative to a pure metal current collector, and is conducive to further improving the energy density of the battery cell.

[0021] In some embodiments, the thickness of the first metal layer is 200 nm ~ 2000 nm.

[0022] In some embodiments, the negative electrode sheet comprises a negative current collector and a negative active layer located on at least one surface of the negative current collector, and the negative active layer contains a gel electrolyte and a negative active material.

[0023] In some embodiments, the gel electrolyte is distributed on the surface of the particles of the negative active material. The distribution of the gel electrolyte on the surface of the particles of the negative active material can protect the particles of the active material, reduce the side reaction between the particles of the negative active material and the electrolyte, and further improve the cycle performance of the battery cell.

[0024] In some embodiments, the gel electrolyte is distributed at the pores between the particles of the negative active material. At this time, more electrolyte can be confined in the negative electrode sheet, further improving the cycle performance of the battery cell.

[0025] In some embodiments, in the negative active layer, the mass percentage of the lyophilic polymer in the negative active layer is 1% ~ 5%. The mass percentage of the lyophilic polymer in the negative active layer in this range can make the confined electrolyte have a suitable amount in the negative active layer, make the confined electrolyte better adapt to the negative active material, and further improve the cycle performance of the battery cell.

[0026] In some embodiments, the density of the negative active layer is 1 g / cm 3 ~ 2 g / cm 3 , and optionally 1.3 g / cm 3 ~ 1.7 g / cm 3 .

[0027] In some embodiments, the negative current collector comprises a second support layer and a second metal layer, the second metal layer is on at least one surface of the second support layer, and the second metal layer is between the second support layer and the negative active layer. The negative current collector is in the form of a composite current collector, which can reduce the weight of the negative current collector relative to a pure metal current collector, and is conducive to further improving the energy density of the battery cell.

[0028] In some embodiments, the thickness of the second metal layer is 200 nm to 2000 nm.

[0029] In some embodiments, the gel electrolyte is distributed at the pores of the separator film. At this time, more electrolyte can be confined in the separator film, promoting the transmission of active ions and further improving the cycle performance of the battery cell.

[0030] In some embodiments, the separator film comprises a separator film substrate and a coating layer on at least one surface of the separator film substrate, and the coating layer contains a particulate filler. The coating layer containing the particulate filler has good heat resistance and high strength, which can improve the heat resistance and strength of the separator film, so that the separator film maintains a relatively stable structure during the cycle of the battery cell, and promotes the further improvement of the cycle performance of the battery cell. Optionally, the particulate filler comprises one or more of boehmite, aluminum oxide, silicon dioxide, and magnesium hydroxide.

[0031] In some embodiments, the thickness of the coating layer is 0.25 μm to 5 μm.

[0032] In some embodiments, the material of the separator film substrate comprises one or more of polyethylene, polypropylene, polyimide, and aramid.

[0033] In some embodiments, the lyophilic polymer comprises a fluorinated polymer; the fluorinated polymer has a crystallinity X c1 , 15%≤X c1 ≤25%; and the fluorinated polymer has a melting temperature T m1 , which is in °C, 120≤T m1 ≤140.

[0034] In some embodiments, the fluorinated polymer has a cold crystallinity X c2 , 10%≤X c2 ≤25%; and the fluorinated polymer has a cold crystallization temperature Tc2, which is in °C, 35≤T c2 ≤65.

[0035] In some embodiments, the monomer of the fluorinated polymer comprises hexafluoropropylene and vinylidene fluoride.

[0036] In some embodiments, the mole percentage of hexafluoropropylene is 6% to 13% based on the total mole ratio of hexafluoropropylene and vinylidene fluoride.

[0037] In some embodiments, the fluorinated polymer comprises at least one of a structural unit represented by Formula (AI) to a structural unit represented by Formula (AIII),

[0038] In Formula (AI) and Formula (AII), R 11 , R 12 , R 13 , and R 14 each independently comprises a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and R 11 , R 12 , R 13 , and R 14 at least one of which comprises a fluorine atom; when substituted, the substituent comprises one or more of a nitrile group, a nitro group, a sulfonic acid group, a sulfonyl group, an amide, a carboxyl group, an ester group, a halogen atom;

[0039] In Formula (AIII), R 15 comprises a single bond, a substituted or unsubstituted C1-C3 alkyl group; when substituted, the substituent comprises one or more of a nitrile group, a nitro group, a sulfonic acid group, a sulfonyl group, an amide, a carboxyl group, an ester group, a halogen atom; p is selected from a positive integer from 1 to 3; n is each independently selected from a positive integer from 1000 to 30000.

[0040] In some embodiments, the molecular weight of the lyotropic polymer is 1.2 x 10 5 g / mol to 1 x 10 6 g / mol.

[0041] In some embodiments, the lithium ion transference number of the gel electrolyte is ≥ 0.4.

[0042] The second aspect of the present application provides a battery. The battery comprises the battery cell of the first aspect.

[0043] The third aspect of the present application provides a power consuming device. The power consuming device comprises the battery of the second aspect. BRIEF DESCRIPTION OF DRAWINGS

[0044] For better describing and illustrating the embodiments or examples provided by the present application, one or more drawings can be referred to. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any one of the disclosed applications, the presently described embodiments or examples, and the best mode presently understood of these applications. Moreover, in all the drawings, the same reference numbers are used to represent the same components. In the drawings:

[0045] FIG. 1 is a schematic view of a battery cell according to an embodiment of the present application.

[0046] FIG. 2 is an exploded view of the battery cell shown in FIG. 1 according to an embodiment of the present application.

[0047] FIG. 3 is a schematic view of an electric device using the battery cell according to an embodiment of the present application as a power source.

[0048] BRIEF DESCRIPTION OF DRAWINGS 1: battery cell; 11: case; 12: electrode assembly; 13: end cap; 14: electrode terminal; 2: electric device. DETAILED DESCRIPTION

[0049] For the purposes of promoting an understanding of the principles of the application, reference will now be made to the embodiments illustrated in the drawings. It is expressly understood that the drawings are for illustrative purposes and are not a limitation on the scope of the application. In addition, it is to be understood that certain specific details of the application are set forth in this description for a full and enabling understanding, but are not intended to limit the application. On the contrary, it is intended to cover all alternatives, modifications, and equivalents. For example, it is intended that the application encompass more recent types of battery cells and electric devices, and changes in the shape of the battery cell and the electric device, which are presently unforeseeable.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this description of the application, the following terms are defined with the following meanings:

[0051] "ranges" disclosed herein can be defined, for example, by the lower and upper values. Any lower limit can independently be combined with any upper limit to define a range of any value. For example, if a range of 60-120 and 80-110 is listed as exemplary, it is understood that a range of 60-110 and 80-120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is also listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, the use of "a" and "an" to describe a single item can be taken as equivalent to the use of "one" or "at least one," unless otherwise limited by context. In this application, the use of "or" as a conjunction can be taken as

[0052] In this application, the use of "a" and "an" to describe a single item can be taken as equivalent to the use of "one" or "at least one," unless otherwise limited by context. In this application, the use of "or" as a conjunction can be taken as

[0053] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, if not specifically stated.

[0054] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment or implementation of the application. The appearances of the phrase that the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of other embodiments. It is explicitly stated that the embodiments described herein can be combined with other embodiments. Reference herein to "an implementation" has a similar understanding.

[0055] Those skilled in the art can understand that the order of writing each step in the method of each embodiment or example does not mean a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. If not specifically stated, all steps of the present application can be performed in sequence or randomly. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method can also comprise step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0056] In the present application, "A, such as B" means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0057] In the present application, "optionally", "optional" and "optional" mean that it can or can not be present, that is, it means to select any one from the two parallel schemes of "yes" or "no". If there are multiple "options" in a technical solution, unless otherwise specified, and there is no contradiction or mutual restriction, each "option" is independent.

[0058] Generally, a battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent short circuiting of the positive and negative electrodes, and at the same time to allow ions to pass through.

[0059] In the present application, "battery cell" means a basic unit capable of realizing mutual conversion between chemical energy and electrical energy, and further, generally at least includes a positive electrode sheet, a negative electrode sheet and an electrolyte. During the charging and discharging process of the battery, active ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet.

[0060] An embodiment of the present application provides a battery cell, comprising: a shell, the shell having an opening; a cover, the cover being used to cover the opening; an electrode terminal, the electrode terminal being arranged on the cover; in a direction along gravity, the electrode terminal is located at a bottom of the shell; an electrode assembly, the electrode assembly being accommodated in the shell; the electrode assembly comprises a positive electrode sheet, a separator and a negative electrode sheet, the separator being arranged between the positive electrode sheet and the negative electrode sheet; at least one of the positive electrode sheet, the separator and the negative electrode sheet contains a gel electrolyte; the gel electrolyte comprises a lyophilic polymer and a limited electrolyte, the limited electrolyte being located inside the lyophilic polymer; free electrolyte in the shell is less than or equal to 10 mL.

[0061] In the battery cell of the embodiment, by using the gel electrolyte, the electrolyte can be limited inside the lyophilic polymer, at this time, the limited electrolyte can better play the role of the electrolyte, so that the amount of free electrolyte in the battery cell can be greatly reduced, the corrosion of the free electrolyte to the weld can be reduced, and the risk of liquid leakage of the battery cell can be reduced.

[0062] It can be understood that when the free electrolyte in the shell is 0, the limited electrolyte in the gel electrolyte and the electrolyte that can be adsorbed in the electrode assembly can play the role of the electrolyte, so that the battery cell can maintain good cycle performance. When the shell contains a small amount of free electrolyte, the free electrolyte can supplement the electrolyte in the electrode assembly when the electrolyte in the electrode assembly is consumed, so that the battery cell can maintain stable cycle performance. When the free electrolyte in the shell is less than or equal to 10 mL, the battery cell can maintain good cycle performance, and the risk of liquid leakage of the battery cell can be reduced.

[0063] In some embodiments, the free electrolyte in the shell can be 10 mL, 9.5 mL, 9 mL, 8.5 mL, 8 mL, 7.5 mL, 7 mL, 6.5 mL, 6 mL, 5.5 mL, 5 mL, 4.5 mL, 4 mL, 3.5 mL, 3 mL, 2.5 mL, 2 mL, 1.5 mL, 1 mL, 0.9 mL, 0.8 mL, 0.7 mL, 0.6 mL, 0.5 mL, 0.4 mL, 0.3 mL, 0.2 mL, 0.1 mL, 0 or any value in the range formed by any two of the above values. Alternatively, the free electrolyte in the shell is less than or equal to 2 mL.

[0064] After the electrolyte is injected into the battery cell, the electrolyte mainly exists in the following forms: one is the electrolyte that can be adsorbed in the electrode assembly, two is the limited electrolyte located inside the lyophilic polymer, and three is the free electrolyte that can be free in the battery cell.

[0065] The mass of the electrolyte injected into the battery cell and the mass of the free electrolyte in this application can be tested by the following method: Take a fresh battery cell, fully charge it to 0% SOC, and weigh the battery cell. The mass of the weighed cell is M1. A hole with a diameter of [missing information] is drilled at a local location in the battery cell. To construct a battery cell, place it above a container with the hole facing down and directly above the container, allowing the free electrolyte inside the battery cell to drip into the container below. Let the battery cell stand like this for 3 to 5 hours to allow all the free electrolyte to drip into the container. Then weigh the volume of electrolyte in the container; this is the volume of free electrolyte in the battery cell casing. Next, disassemble the battery cell and dry each component at 60°C to 95°C for 24 to 48 hours. Then immerse each component in dimethyl carbonate (DMC) solvent for 12 hours, and then dry each component at 60°C to 95°C for 24 to 48 hours. Repeat the immersion and drying process twice. Weigh each dried component, and record the total weight as M2. In the testing method, a fresh battery cell can be a battery cell that has just left the factory. A battery cell that has just left the factory can be a battery cell that has not been charged and discharged after formation, or a battery cell that has been assembled into an electrical device and has been used for less than 10 cycles. The mass of electrolyte injected into the battery cell is M1-M2.

[0066] In some embodiments, the casing material includes one or more of aluminum, aluminum alloys, and stainless steel. This provides the casing with good corrosion resistance, which helps to further reduce the risk of leakage from individual battery cells.

[0067] In some embodiments, the gel electrolyte is uniformly distributed in at least one of the positive electrode, the separator, and the negative electrode. Uniform distribution of the gel electrolyte allows for more uniform contact between the limiting electrolyte and at least one of the positive electrode, the separator, and the negative electrode, which is beneficial for further promoting sufficient wetting of the positive electrode, the separator, and the negative electrode by the electrolyte, and further improving the cycle performance of the battery cell.

[0068] In some embodiments, the positive electrode includes a positive current collector and a positive active layer located on at least one surface of the positive current collector. The positive active layer contains a gel electrolyte and a positive active material. The gel electrolyte is distributed on the surface of the positive active material particles. The distribution of the gel electrolyte on the surface of the positive active material particles can protect the active material particles, reduce side reactions between the positive active material particles and the electrolyte, and further improve the cycle performance of the battery cell.

[0069] The gel electrolyte is distributed on the surface of the particles of the positive active material, which means that the gel electrolyte is located on the surface of the positive active layer away from the positive current collector. For example, the surface of the positive current collector forms a film layer including the positive active material, and the gel electrolyte is located on the surface of the film layer away from the positive current collector. Alternatively, the preparation of the positive electrode sheet with such a structure includes the following steps: coating the positive electrode slurry including the positive active material on the surface of the positive current collector, drying and curing to obtain the film layer, and then disposing the lyophilic polymer on the surface of the film layer. When the lyophilic polymer is in contact with the electrolyte, the lyophilic polymer adsorbs the electrolyte to form the gel electrolyte. Thus, the structure in which the gel electrolyte is distributed on the surface of the particles of the positive active material is obtained. It can be understood that the positive electrode slurry can further include a binder and a conductive agent, etc.

[0070] In some embodiments, the gel electrolyte is distributed at the pores between the particles of the positive active material. At this time, more electrolyte can be confined in the positive electrode sheet, further improving the cycle performance of the battery cell. Alternatively, the preparation of the positive electrode sheet with such a structure includes the following steps: mixing the lyophilic polymer and the positive active material in a solvent to obtain a positive electrode slurry, then coating the positive electrode slurry on the surface of the positive current collector, and drying and curing to obtain a film layer. When the film layer is in contact with the electrolyte, the lyophilic polymer adsorbs the electrolyte to form the gel electrolyte. Thus, the structure in which the gel electrolyte is distributed at the pores between the particles of the positive active material is obtained. It can be understood that the positive electrode slurry can further include a binder and a conductive agent, etc.

[0071] In some embodiments, the mass percentage of the lyophilic polymer in the positive active layer is 0.1% to 2%. The mass percentage of the lyophilic polymer in the positive active layer in this range can make the confined electrolyte have a suitable amount in the positive active layer, so that the confined electrolyte and the positive active material are better adapted, further improving the cycle performance of the battery cell. Alternatively, the mass percentage of the lyophilic polymer in the positive active layer can be 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, or any value within the range formed by any two of the above values. Further alternatively, the mass percentage of the lyophilic polymer in the positive active layer is 0.1% to 1%.

[0072] In some embodiments, the positive active material comprises lithium nickel manganese cobalt oxide; and the mole percentage of nickel element in the lithium nickel manganese cobalt oxide, in terms of mole percentage of nickel element, manganese element and cobalt element, is 80% to 95%. The lithium nickel manganese cobalt oxide with the mole percentage of nickel element in this range has higher gram capacity, which is beneficial to further improve the energy density of the battery cell. Optionally, the mole percentage of nickel element, in terms of mole percentage of nickel element, manganese element and cobalt element, can be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95% or any value within a range consisting of any two of the above values. Optionally, the lithium nickel manganese cobalt oxide can be LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.92 Co 0.06 Mn 0.02 O2.

[0073] In some embodiments, the density of the positive active layer is 2 g / cm 3 to 3.8 g / cm 3 . The density of the positive active layer in this range can make the battery cell have a more appropriate weight and higher energy density. For example, the density of the positive active layer can be 2 g / cm 3 , 2.1 g / cm 3 , 2.2 g / cm 3 , 2.3 g / cm 3 , 2.4 g / cm 3 , 2.5 g / cm 3 , 2.6 g / cm 3 , 2.7 g / cm 3 , 2.8 g / cm 3 , 2.9 g / cm 3 , 3 g / cm 3 , 3.1 g / cm 3 , 3.2 g / cm 3 , 3.3 g / cm 3 , 3.4 g / cm 3 , 3.5 g / cm 3 , 3.6 g / cm 3 , 3.7 g / cm 3 , 3.8 g / cm 3 or any value within a range consisting of any two of the above values.

[0074] Optionally, the positive active material comprises lithium nickel cobalt manganese oxide, and the density of the positive active layer is 3.5 g / cm 3 to 3.8 g / cm3 .

[0075] Optionally, the positive active material includes lithium-containing phosphate, and the density of the positive active layer is 2 g / cm 3 ~ 3 g / cm 3 .

[0076] In some embodiments, the energy density of the battery cell can be 250 Wh / kg ~ 400 Wh / kg by selecting the appropriate areal density of the positive active layer. For example, the energy density of the battery cell can be 250 Wh / kg, 260 Wh / kg, 270 Wh / kg, 280 Wh / kg, 290 Wh / kg, 300 Wh / kg, 310 Wh / kg, 320 Wh / kg, 330 Wh / kg, 340 Wh / kg, 350 Wh / kg, 360 Wh / kg, 370 Wh / kg, 380 Wh / kg, 390 Wh / kg, 400 Wh / kg, etc. Optionally, the energy density of the battery cell is 270 Wh / kg ~ 350 Wh / kg.

[0077] In some embodiments, the positive current collector includes a first support layer and a first metal layer, the first metal layer is located on at least one surface of the first support layer, and the first metal layer is located between the first support layer and the positive active layer. The positive current collector adopts the form of a composite current collector, which can reduce the weight of the positive current collector relative to a pure metal current collector, and is conducive to further improving the energy density of the battery cell. Optionally, the material of the first support layer includes at least one of polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), polyethylene, polypropylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polyformaldehyde, epoxy resin, phenolic resin, silicone rubber, and polycarbonate. Optionally, the material of the first metal layer includes at least one of aluminum and aluminum alloy.

[0078] In some embodiments, the thickness of the first metal layer is 200 nm ~ 2000 nm. Optionally, the thickness of the first metal layer can be 200 nm, 500 nm, 800 nm, 1000 nm, 1200 nm, 1500 nm, 1800 nm, 2000 nm, or any value within the range formed by any two of the above values.

[0079] In some embodiments, the positive current collector further comprises a first bonding layer between the first support layer and the first metal layer. The first bonding layer can improve the bonding between the first metal layer and the first support layer, reduce the risk of the first metal layer falling off, and help the positive current collector to maintain better structural stability, thereby further improving the cycle performance of the battery cell. Optionally, the material of the first bonding layer comprises at least one of polyolefin, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyurethane, epoxy resin, styrene-isoprene-styrene copolymer, styrene-butadiene-styrene copolymer, styrene-ethylene-butylene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer, silicone rubber, phenolic resin, urea-formaldehyde resin, and polyimide.

[0080] In some embodiments, the negative electrode tab comprises a negative current collector and a negative active layer on at least one surface of the negative current collector, and the negative active layer contains a gel electrolyte and a negative active material. The gel electrolyte is distributed on the surface of the particles of the negative active material. The distribution of the gel electrolyte on the surface of the particles of the negative active material can protect the particles of the active material, reduce the side reaction between the particles of the negative active material and the electrolyte, and further improve the cycle performance of the battery cell.

[0081] The gel electrolyte is distributed on the surface of the particles of the negative active material, which means that the gel electrolyte is located on the surface of the film layer away from the negative current collector. For example, the surface of the negative current collector forms a film layer containing the negative active material, and the gel electrolyte is located on the surface of the film layer away from the negative current collector. Optionally, the preparation of the negative electrode tab with such a structure comprises the following steps: coating a negative slurry containing the negative active material on the surface of the negative current collector, drying and curing to obtain the film layer, and then disposing the lyophilic polymer on the surface of the film layer. When the lyophilic polymer contacts with the electrolyte, the lyophilic polymer absorbs the electrolyte to form the gel electrolyte. Thus, the gel electrolyte is distributed on the surface of the particles of the negative active material. It can be understood that the negative slurry can further comprise a binder and a conductive agent, etc.

[0082] In some embodiments, the gel electrolyte is distributed at the pores between the particles of the negative active material. At this time, more electrolyte can be confined in the negative electrode tab, thereby further improving the cycle performance of the battery cell. Optionally, the preparation of the negative electrode tab with such a structure comprises the following steps: mixing the lyophilic polymer and the negative active material in a solvent to obtain a negative slurry, then coating the negative slurry on the surface of the negative current collector, and drying and curing to obtain a film layer. When the film layer contacts with the electrolyte, the lyophilic polymer absorbs the electrolyte to form the gel electrolyte. Thus, the gel electrolyte is distributed at the pores between the particles of the negative active material. It can be understood that the negative slurry can further comprise a binder and a conductive agent, etc.

[0083] In some embodiments, the mass percentage of the lyophilic polymer in the negative active layer is 1% to 5%. The mass percentage of the lyophilic polymer in the negative active layer in this range can allow the limiting electrolyte to have a suitable amount in the negative active layer, and allow the limiting electrolyte to better match the negative active material, and further improve the cycle performance of the battery cell. Alternatively, the mass percentage of the lyophilic polymer in the negative active layer can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any value in a range defined by any two of the above values. Further alternatively, the mass percentage of the lyophilic polymer in the negative active layer is 2% to 4%.

[0084] In some embodiments, the density of the negative active layer is 1 g / cm 3 to 2 g / cm 3 . Alternatively, the density of the negative active layer can be 1 g / cm 3 , 1.1 g / cm 3 , 1.2 g / cm 3 , 1.3 g / cm 3 , 1.4 g / cm 3 , 1.5 g / cm 3 , 1.6 g / cm 3 , 1.7 g / cm 3 , 1.8 g / cm 3 , 1.9 g / cm 3 , 2 g / cm 3 , or any value in a range defined by any two of the above values. Further alternatively, the density of the negative active layer is 1.3 g / cm 3 to 1.7 g / cm 3 . Further alternatively, the negative active material includes graphite.

[0085] In some embodiments, the negative current collector includes a second support layer and a second metal layer, the second metal layer is on at least one surface of the second support layer, and the second metal layer is between the second support layer and the negative active layer. The negative current collector is in the form of a composite current collector, which can reduce the weight of the negative current collector relative to a pure metal current collector, and is conducive to further improving the energy density of the battery cell. Alternatively, the material of the second support layer includes at least one of polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyphenylene terephthalamide, polyethylene, polypropylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polyformaldehyde, epoxy resin, phenolic resin, silicone rubber, and polycarbonate.

[0086] In some embodiments, the second metal layer has a thickness of 200 nm to 2000 nm. Optionally, the second metal layer has a thickness of 200 nm, 500 nm, 800 nm, 1000 nm, 1200 nm, 1500 nm, 1800 nm, 2000 nm, or any value within a range defined by any two of the aforementioned values.

[0087] In some embodiments, the negative current collector further comprises a second adhesive layer between the second support layer and the second metal layer. The second adhesive layer can improve the bonding force between the second metal layer and the second support layer, reduce the risk of the second metal layer falling off, and help the positive current collector to maintain better structural stability, thereby further improving the cycle performance of the battery cell. Optionally, the material of the second adhesive layer comprises at least one of polyolefin, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyurethane, epoxy resin, styrene-isoprene-styrene copolymer, styrene-butadiene-styrene copolymer, styrene-ethylene-butylene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer, silicone rubber, phenolic resin, urea-formaldehyde resin, and polyimide. Optionally, the material of the second metal layer comprises at least one of copper and copper alloy.

[0088] In some embodiments, the gel electrolyte is distributed in the pores of the separator film. In this case, more electrolyte can be confined in the separator film, which promotes the transmission of active ions and further improves the cycle performance of the battery cell.

[0089] In some embodiments, the separator film comprises a separator film substrate and a coating layer on at least one surface of the separator film substrate, and the coating layer contains a particulate filler. Optionally, the particulate filler comprises one or more of boehmite, alumina, silica, and magnesium hydroxide. The coating layer containing the particulate filler has good heat resistance and high strength, which can improve the heat resistance and strength of the separator film, so that the separator film maintains a relatively stable structure during the cycle of the battery cell and promotes further improvement of the cycle performance of the battery cell. Optionally, the thickness of the coating layer is 0.25 μm to 5 μm. For example, the thickness of the coating layer can be 0.25 μm, 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 3 μm, 4 μm, 5 μm, or any value within a range defined by any two of the aforementioned values.

[0090] In some embodiments, the coating layer comprises a solid-state electrolyte. The solid-state electrolyte is optionally lithium aluminum titanium phosphate. Optionally, the coating layer is provided between the positive electrode tab and the separator film substrate.

[0091] Optionally, the coating of the separator also contains an adhesive. The use of an adhesive can improve the adhesion between the coating and the separator substrate, further enhancing the structural stability of the separator. More optionally, the adhesive can be one or more of polyvinylidene fluoride and polyacrylate.

[0092] In some embodiments, the material of the separator substrate includes one or more of polyethylene, polypropylene, polyimide, and aramid. Optionally, the thickness of the separator substrate is 3 μm to 20 μm. For example, the thickness of the separator substrate can be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or any value within the range of any two of the above values. More optionally, the thickness of the separator substrate is 5 μm to 16 μm.

[0093] In some embodiments, the limiting electrolyte comprises a solvent and an electrolyte salt. Optionally, the solvent comprises at least one selected from cyclic carbonates, chain carbonates, carboxylic acid esters, fluorocarbonates, and sulfites. Cyclic carbonates include one or more selected from ethylene carbonate (EC) and propylene carbonate (PC). Chain carbonates include one or more selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC).

[0094] Electrolyte salts include lithium salts. Lithium salts include at least one of LiPF6, LiBF4, LiBOB, LiFSI, LiTFSI, Li2DFB, and LiODFB.

[0095] In some embodiments, the mass percentage of ethylene carbonate in the solvent of the limiting electrolyte is 0. The absence of ethylene carbonate in the electrolyte can give the battery cell better thermal stability.

[0096] In some implementations...

[0097] The free electrolyte comprises a solvent and an electrolyte salt. Optionally, the solvent comprises at least one of cyclic carbonates, chain carbonates, carboxylic esters, fluorocarbonates, and sulfites. Cyclic carbonates include one or more of ethylene carbonate (EC) and propylene carbonate (PC). Chain carbonates include one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC).

[0098] Electrolyte salts include lithium salts. Lithium salts include at least one of LiPF6, LiBF4, LiBOB, LiFSI, LiTFSI, Li2DFB, and LiODFB.

[0099] Optionally, the limiting electrolyte and the free electrolyte are the same.

[0100] In some embodiments, the mass percentage of ethylene carbonate in the solvent of the free electrolyte is 0.

[0101] In some embodiments, the lyophilic polymer comprises one or more of a fluorinated polymer, an ether polymer, an ester polymer, and an aldehyde-ketone polymer.

[0102] fluorinated polymer

[0103] In some embodiments, the lyophilic polymer comprises a fluorinated polymer; the crystallinity of the fluorinated polymer is X c1 , 15%≤X c1 ≤25%; the melting temperature of the fluorinated polymer is T m1 , in units of ℃, 120≤T m1 ≤140.

[0104] The cold crystallinity of the fluorinated polymer is X c2 , 10%<X c2 ≤25%; the cold crystallization temperature of the fluorinated polymer is Tc2, in units of ℃, 35≤T c2 ≤65.

[0105] Crystallization refers to the process of ordering of atoms, ions, or molecules in a material according to a certain spatial order. The conformation of a polymer in crystallization is determined by both intramolecular and intermolecular factors, and intermolecular forces affect the packing density between molecular chains. The degree of crystallinity X c1 is used to represent the degree of crystallization in a material, which can be measured by differential scanning calorimetry (DSC). Specifically, the test procedure is as follows: take 0.5g-0.8g of sample, place the sample in a sample crucible, and perform temperature rising and falling treatment on the sample under nitrogen atmosphere, with a temperature rising rate of 10℃ / min, from an initial temperature of 20℃ lower than the intrinsic T g1 of the material to a cut-off temperature of 20℃ higher than the intrinsic T m1 of the material, to determine the actual glass transition temperature T g1 and melting temperature T m1 of the material according to the endothermic and exothermic peaks or transition points of the material in the process.

[0106] Thus, the fluorinated polymer has a relatively low crystallinity and melting temperature, so that the molecular chains tend to be arranged loosely, the force between the molecular chains is small, adjacent molecular chains are easily opened, and chain segment movement is achieved through intermolecular internal rotation, forming a molecular chain structure with high flexibility. Moreover, the fluorinated polymer and the electrolyte in the battery cell can form a gel electrolyte, further improving the cycle performance of the battery cell.

[0107] Exemplarily, the crystallinity X of the fluorinated polymer measured by differential scanning calorimetry can be 10%, 12%, 15%, 18%, 20%, 22%, 25%, or any value within a range consisting of any two of the above values. c1 may be 20%, 21%, 22%, 23%, 24%, 25%, or any value within a range consisting of any two of the above values.

[0108] Exemplarily, the melting temperature Tm of the fluorinated polymer can be 20°C, 50°C, 70°C, 90°C, 100°C, 120°C, 140°C, or any value within a range consisting of any two of the above values. m1 may be 20°C, 50°C, 70°C, 90°C, 100°C, 120°C, 140°C, or any value within a range consisting of any two of the above values.

[0109] Exemplarily, the cold crystallinity X of the fluorinated polymer measured by differential scanning calorimetry can be 10%, 12%, 15%, 18%, 20%, 22%, 25%, or any value within a range consisting of any two of the above values. c2 may be 10%, 12%, 15%, 18%, 20%, 22%, 25%, or any value within a range consisting of any two of the above values.

[0110] Exemplarily, the cold crystallization temperature Tc2 of the fluorinated polymer can be 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, or any value within a range consisting of any two of the above values.

[0111] In some embodiments, the glass transition temperature of the fluorinated polymer is Tg. g1 , in units of °C, -150≤Tg≤60. g1 .

[0112] The glass transition temperature is the transition temperature of the chain segment of the polymer from freezing to movement, and the glass transition temperature has a certain influence on the flexibility of the polymer molecular chain. The lower the glass transition temperature, the better the flexibility of the polymer molecular chain at room temperature, and the higher the glass transition temperature, the worse the flexibility of the molecular chain at room temperature. The glass transition temperature can be measured by differential scanning calorimetry DSC. The glass transition temperature of the polymer is relatively low, the chain segment of the molecular chain is better, and adjacent molecular chains are more easily opened. Exemplarily, the glass transition temperature of the fluorinated polymer can be -150°C, -120°C, -100°C, -80°C, -60°C, -30°C, 0°C, 30°C, 60°C, or any value within a range consisting of any two of the above values.

[0113] In some embodiments, the monomers of the fluorinated polymer include hexafluoropropylene and vinylidene fluoride. The design of both monomers of hexafluoropropylene and vinylidene fluoride can make the fluorinated polymer have a lower crystallinity, which is conducive to promoting the diffusion and infiltration of the electrolyte in the fluorinated polymer, improving the affinity of the fluorinated polymer to the electrolyte, and improving the liquid retention capacity of the gel electrolyte. Alternatively, the molar percentage of hexafluoropropylene is 6% to 13% based on the total molar ratio of hexafluoropropylene and vinylidene fluoride. The molar percentage of hexafluoropropylene in this range can make the fluorinated polymer have a stable structure, while maintaining good affinity to the electrolyte, reducing the risk of the fluorinated polymer being dissolved by the electrolyte, further promoting the retention of the electrolyte in the fluorinated polymer, reducing the risk of the confined electrolyte in the gel electrolyte becoming free electrolyte, and further reducing the risk of liquid leakage of the battery cell. Alternatively, the molar percentage of hexafluoropropylene can be 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, or any value within a range formed by any two of the above values based on the total molar ratio of hexafluoropropylene and vinylidene fluoride.

[0114] In some embodiments, the fluorinated polymer includes at least one of a structural unit represented by formula (AI) to a structural unit represented by formula (AIII),

[0115] In formula (AI) and formula (AII), R 11 , R 12 , R 13 , and R 14 each independently include a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and at least one of R 11 , R 12 , R 13 , and R 14 includes a fluorine atom; when substituted, the substituent includes one or more of a nitrile group (abbreviation: -CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide, a carboxyl group, an ester group, a halogen atom;

[0116] In formula (AIII), R 15 includes a single bond, a substituted or unsubstituted C1-C3 alkyl group; when substituted, the substituent includes one or more of a nitrile group, a nitro group, a sulfonic acid group, a sulfonyl group, an amide, a carboxyl group, an ester group, a halogen atom; p is selected from a positive integer of 1 to 3; and n is each independently selected from a positive integer of 1000 to 30000.

[0117] In some embodiments, R 11 , R 12 , R 13 , and R 14each independently comprises a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C2 alkyl group, or a substituted or unsubstituted C1-C2 alkoxy group; further optionally, R 11 , R 12 , R 13 and R 14 each independently comprises a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, a fluoromethyl group, a methoxy group, or a perfluoromethoxy group.

[0118] In some embodiments, the fluoropolymer comprises at least one of a structural unit represented by Formula (AI-1) to a structural unit represented by Formula (AI-11),

[0119] In some embodiments, the fluoropolymer comprises at least one of a structural unit represented by Formula (AII-1) to a structural unit represented by Formula (AII-5),

[0120] In some embodiments, the fluoropolymer comprises at least one of a structural unit represented by Formula (AIII-1) to a structural unit represented by Formula (AIII-3),

[0121] Illustratively, the fluoropolymer comprises one or more of polytetrafluoroethylene PTFE, polyvinylidene fluoride PVDF, perfluoroalkoxy polymer PFA, perfluoropolyether PFPE, polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP, polyvinylidene fluoride-trifluoroethylene copolymer PVDF-TrFE, and perfluoro(l-butene vinyl ether) polymer CYTOP.

[0122] Optionally, the fluoropolymer comprises one or more of polytetrafluoroethylene PTFE, polyvinylidene fluoride PVDF, perfluoroalkoxy polymer PFA, polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP, polyvinylidene fluoride-trifluoroethylene copolymer PVDF-TrFE.

[0123] The fluoropolymer described above can be derived from one or more of fluorocycloethane, fluorovinyl, 1,2-difluorovinyl, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropene, trifluoropropene, tetrafluoropropene, pentafluoropropene, and the like. Optionally, the fluoropolymer described above can be derived from at least two of fluorocycloethane, fluorovinyl, 1,2-difluorovinyl, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropene, trifluoropropene, tetrafluoropropene, pentafluoropropene.

[0124] The monomers used in the above fluorinated polymer are all short-chain monomers, which are beneficial to polymerization to form linear chain structures or short branched chain structures. The entanglement degree of this type of structure is low, which is beneficial to improve the flexibility of the molecular chain, and the molecular chain can fully stretch in the electrolyte, thereby further improving the interface performance of the active material.

[0125] In some embodiments, n is each independently selected from positive integers from 5000 to 20000; and / or the molecular weight of the lyophilic polymer is from 2x10 5 g / mol to 1.5x10 6 g / mol. When the molecular weight of the polymer is in the above range, the polymer can exhibit a certain solubility in the electrolyte, while it is not easy to be completely dissolved and dispersed in the electrolyte, which is beneficial to control the distribution and dispersion of the polymer on the surface of the active material; and further improve the flexibility between the molecular chains of the polymer, the interaction between the molecular chains is relatively weak, which is beneficial to the solvent molecules in the electrolyte to open the molecular chains and enter between the molecular chains, and to be wrapped by the molecular chains, thereby facilitating the active ions to enter the active material through the solvent, realizing the smooth and rapid migration of the active ions.

[0126] For example, the molecular weight of the polymer can be 2x10 5 g / mol, 5x10 5 g / mol, 8x10 5 g / mol, 1x10 6 g / mol, 1.5x10 6 g / mol, or any value within a range consisting of any two of the above values.

[0127] Ether polymer

[0128] The lyophilic polymer includes an ether polymer, wherein the ether polymer is made into a sheet-shaped structure; the sheet-shaped structure has an elastic modulus G'-dissipation modulus G" curve obtained by dynamic frequency scanning test at (T m2 +20) ℃, and the slope of the elastic modulus G'-dissipation modulus G" curve is K1,1 < K1 < ∞, T m2 ℃ represents the melting temperature of the ether polymer.

[0129] Specifically, the preparation process of the sheet-shaped structure is as follows: the ether polymer is vacuum dried at 80℃ for 12h. The dried ether polymer is hot-pressed into a sheet by a flat plate curing machine, and the hot-pressing temperature is set to (T m2+20)℃, the calendering thickness is 1mm-2mm, the calendering time is 2min, and the pressure is 8MPa. After 2min of calendering, the sample is taken out and placed on another vulcanizing machine of the same type for cold pressing, and the cold pressing pressure is 10MPa. A circular mold with a diameter of 25mm is used to obtain a polymer disc with a fixed size, and the polymer disc is a sheet structure. Exemplarily, the sheet structure can be a disc with a thickness of 1mm-2mm and a diameter of 25mm; or the sample can be prepared according to the sample standard required by the test equipment.

[0130] According to the conclusion of classical linear viscoelasticity, for polymers, especially linear polymers, the elastic modulus G'-dissipation modulus G" in the terminal region of the elastic modulus G'-dissipation modulus G" curve is frequency-dependent, and the longest chain of the polymer plays a role in viscoelastic behavior. The terminal region of the elastic modulus G'-dissipation modulus G" curve represents the interval range approaching the maximum angular velocity.

[0131] The specific steps of the dynamic frequency scanning test are as follows: the dynamic frequency scanning test is performed by using a TA-AR2000EX rotary rheometer, the parallel plate diameter is 25mm, and the thickness is 0.9mm. In order to ensure that the test is in the linear point elastic region, the strain is 2% during the dynamic frequency scanning test, and the test temperature is (T m2 +20)℃, and the frequency scanning range of the test is: 500rad / s≤w2≤0.05rad / s, so as to obtain data in the lowest frequency range as possible.

[0132] The dynamic frequency scanning test can characterize solid phase melting, that is, the entanglement degree of molecular chains in the melt state. Compared with linear structures or short branched chain structures, long branched structures, network structures and low crosslinking structures have high entanglement degree and will exhibit deviated linear terminal behavior, and ether polymers exhibit solid phase behavior. When the ether polymer of the present application meets the above range, the molecular chain entanglement state can be further reduced, which is beneficial to the diffusion of solvent molecules in the electrolyte between the molecular chains; and the ether polymer still maintains a certain molecular chain entanglement state, which can form a gel electrolyte with the electrolyte, and further improve the cycle performance of the battery monomer.

[0133] In some embodiments, 1

[0134] In some embodiments, the glass transition temperature of the ether polymer is T g2 , in ℃, -100≤T g2 ≤50; optionally, -80≤T g2≤ 30. Illustratively, the glass transition temperature Tg of the ether-based polymer is -100°C, -80°C, -60°C, -30°C, 0°C, 30°C, 50°C, or any value within a range defined by any two of the aforementioned values. g2 may be -100°C, -80°C, -60°C, -30°C, 0°C, 30°C, 50°C, or any value within a range defined by any two of the aforementioned values.

[0135] In some embodiments, the ether-based polymer includes a structural unit represented by Formula (BI),

[0136] In Formula (BI), R 21 and R 22 each independently include a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; R 23 includes a substituted or unsubstituted C1-C5 alkylene group. Alternatively, R 21 and R 22 each independently include a hydrogen atom, a substituted or unsubstituted C1-C2 alkyl group; and / or R 23 includes a single bond, a substituted or unsubstituted C1-C4 methylene group.

[0137] In some embodiments, when substituted, the substituent group can include one or more of a nitrile group, a nitro group, a sulfonic acid group, a sulfonyl group, an amide, a carboxyl group, an ester group, a halogen atom.

[0138] Illustratively, the ether-based polymer includes at least one of a structural unit represented by Formula (BI-1) to a structural unit represented by Formula (BI-8),

[0139] In some embodiments, the ether-based polymer includes a structural unit represented by Formula (BII),

[0140] In Formula (BII), R 24 to R 27 each independently include a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 alkoxy group, or an ether group, and R 24 to R 27 at least one of which includes a substituted or unsubstituted C1-C3 alkoxy group or an ether group.

[0141] Alternatively, R 24 to R 27 each independently include a hydrogen atom, a substituted or unsubstituted C1-C2 alkyl group, a substituted or unsubstituted C1-C2 alkoxy group, or an ether group, and R 24 to R 27 at least one of which includes a substituted or unsubstituted C1-C2 alkoxy group or an ether group.

[0142] In some embodiments, the ether-based polymer comprises at least one of structural units represented by formula (BII-1) to structural units represented by formula (BII-7),

[0143] The monomer used in the above-mentioned ether-based polymer is a short chain monomer or a structure having a ring with a number of members, e.g., a six-membered ring or less, which is advantageous for polymerization to form a high content of -O- structures, and such a structure type has a low degree of entanglement, which is advantageous for improving the flexibility of the molecular chain, and the molecular chain can be fully stretched in the electrolyte, which is easy to form a gel-like substance with the electrolyte, thereby further improving the cycle performance and storage performance of the battery cell.

[0144] The above-mentioned polymer is only an example of the structural group of the main molecular chain, and in the embodiments of the present application, the polymer can also be obtained by copolymerization of the above-mentioned structural group and other types of structural groups. The other types of structural groups can be, for example, olefin-based structural units, acrylonitrile-based structural units, etc.

[0145] When the above-mentioned group is substituted, the substituent group can include one or more of a nitrile group, a nitro group, a sulfonic acid group, a sulfonyl group, an amide, a carboxyl group, an ester group, and a halogen atom. The above-mentioned substituent group is a high-pressure resistant substituent group, which is more advantageous for stabilizing the structure of the polymer. The halogen atom can include a fluorine atom, a chlorine atom, a bromine atom, etc.

[0146] In some embodiments, n is each independently selected from positive integers from 1500 to 25000.

[0147] Alternatively, n is each independently selected from positive integers from 3000 to 18000.

[0148] In some embodiments, the molecular weight of the polymer is 1.2 x 10 5 g / mol to 1.0 x 10 6 g / mol.

[0149] For example, the molecular weight of the polymer can be 1.2 x 10 5 g / mol, 2 x 10 5 g / mol, 5 x 10 5 g / mol, 8 x 10 5 g / mol, 1 x 10 6 g / mol, or any value within a range defined by any two of the above values.

[0150] Ester-based polymer

[0151] In some embodiments, the lyophilic polymer comprises an ester-based polymer, wherein the ester-based polymer is made into a sheet-shaped structure; the sheet-shaped structure is in a state of (T m3+20)℃ under dynamic frequency scanning test to obtain an elastic modulus G'-dissipation modulus G" curve, a slope of the elastic modulus G'-dissipation modulus G" curve is K2, 1 < K2 < ∞, T m3 ℃ represents a melting temperature of the ester-based polymer.

[0152] When the ester-based polymer of the present application meets the above range, the molecular chain entanglement state can be further reduced, which is beneficial to the diffusion of solvent molecules in the electrolyte between the molecular chains; and the ether-based polymer still maintains a certain molecular chain entanglement state, which can form a gel-like substance with the electrolyte, further improving the cycle performance and storage performance of the battery monomer.

[0153] In some embodiments, 1 < K2≤ 100; further optionally, 1 < K2≤ 10.

[0154] Illustratively, K2may be 1.01, 1.1, 1.2, 1.5, 2, 5, 10, 15, 20, 30, 50, 100, 200, 500, 1000, 5000, 10000 or any value within a range consisting of any two of the above values.

[0155] In some embodiments, the glass transition temperature of the ester-based polymer is T g3 , in units of ℃, -100 ≤ T g3 ≤ 50; optionally, -80 ≤ T g3 ≤ 30.

[0156] Illustratively, the glass transition temperature of the ester-based polymer can be -100℃, -90℃, -80℃, -60℃, -30℃, 0℃, 30℃, 50℃ or any value within a range consisting of any two of the above values.

[0157] In some embodiments, the ester-based polymer comprises a structural unit represented by formula (CI).

[0158] In formula (CI), R 31 , R 32 and R 33 each independently comprise a hydrogen atom, or a substituted or unsubstituted C1-C8 alkyl group; R 34 comprises a substituted or unsubstituted C1-C8 alkyl group, or a substituted or unsubstituted C1-C8 hydroxyalkyl group; optionally, R 34 comprises a substituted or unsubstituted C1-C6 alkyl group, or a substituted or unsubstituted C1-C6 hydroxyalkyl group.

[0159] Optionally, R 31 comprises a hydrogen atom, or a substituted or unsubstituted methyl group; R 32 and R 33each independently comprises a hydrogen atom; R 34 comprises a substituted or unsubstituted C1-C4 alkyl group, or a substituted or unsubstituted C1-C4 hydroxyalkyl group.

[0160] Exemplarily, the ester-based polymer comprises at least one of structural units shown in formula (CI-1) to formula (CI-15).

[0161] In some embodiments, the ester-based polymer comprises a structural unit shown in formula (CII).

[0162] In formula (CII), R 35 comprises a substituted or unsubstituted C2-C6 methylene group; optionally, R 35 each independently comprises a substituted or unsubstituted C2-C4 methylene group.

[0163] Exemplarily, the ester-based polymer comprises at least one of structural units shown in formula (CII-1) to formula (CII-5).

[0164] The ester-based polymer described above has a low degree of entanglement of molecular chains, which is beneficial to improve the flexibility of the molecular chains, and the molecular chains can be fully stretched in the electrolyte and easily form a gel electrolyte with the electrolyte.

[0165] The polymer described above is only an example of the structural group of the main molecular chain, and in the embodiments of the present application, the polymer can also be obtained by copolymerization of the above-mentioned structural group and other types of structural groups. Other types of structural groups are, for example, olefin-based structural units, acrylonitrile-based structural units, maleic anhydride, and other monomers with functional groups.

[0166] When the above-mentioned groups are substituted, the substituents can include one or more of a nitrile group, a nitro group, a sulfonyl group, a carboxyl group, an ester group, a chlorine atom, a fluorine atom, and a bromine atom. The above-mentioned substituents are high-pressure resistant substituents, which are more beneficial to stabilize the structure of the polymer.

[0167] In some embodiments, n is each independently selected from positive integers from 800 to 20,000.

[0168] Optionally, n is each independently selected from positive integers from 1,000 to 15,000.

[0169] In some embodiments, the molecular weight of the polymer is 1.2 x 10 5 g / mol to 1.0 x 10 6 g / mol.

[0170] Exemplarily, the molecular weight of the polymer can be 1.2 x 105 g / mol, 2×10 5 g / mol, 5×10 5 g / mol, 8×10 5 g / mol, 1×10 6 g / mol, 1.5×10 6 g / mol or any value within the range consisting of any two of the above values.

[0171] Aldehyde polymers

[0172] In some embodiments, the hydrophilic polymer includes an aldehyde-ketone polymer, wherein the aldehyde-ketone polymer is formed into a sheet-like structure; the sheet-like structure is in (T m4 The elastic modulus G' - energy dissipation modulus G” curve was obtained by dynamic frequency scanning test at +20℃. The slope of the elastic modulus G' - energy dissipation modulus G” curve is K3, 0.8≤K3<∞, T m4 °C indicates the melting temperature of the aldehyde-ketone polymer.

[0173] In some implementations, 0.8 ≤ K3 ≤ 100; alternatively, 0.8 ≤ K3 ≤ 10.

[0174] For example, K3 can be 0.8, 0.9, 1, 2, 5, 10, 15, 20, 30, 50, 100, 200, 500, 1000, 5000, 10000, or any value within the range of any two of the above values.

[0175] In some embodiments, the glass transition temperature of the aldehyde-ketone polymer is T. g4 Its unit is ℃, -100≤T g4 ≤50; optionally, -80≤T g4 ≤30.

[0176] For example, the glass transition temperature of the aldehyde-ketone polymer can be -100°C, -90°C, -80°C, -60°C, -30°C, 0°C, 30°C, 50°C, or any value within the range of any two of the above values.

[0177] In some embodiments, the aldehyde-ketone polymer comprises structural units represented by formula (DI) and / or formula (DII).

[0178] In formula (DI), R 41 Including single-bonded, substituted, or unsubstituted C1-C6 methylene groups; R 42 Includes hydrogen atoms, substituted or unsubstituted C1-C6 alkyl groups.

[0179] Optionally, R 41includes a single bond, a substituted or unsubstituted C1-C2 methylene group.

[0180] Optionally, R 42 includes a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group.

[0181] In the embodiments of the present application, a single bond indicates that the group is absent, and the atoms on both sides of the group are connected by a single bond, for example, R 41 is a single bond, indicating that R 41 the carbon atoms on both sides are connected by a single bond.

[0182] Exemplarily, the aldehyde ketone polymer includes at least one of the structural units shown in formula (DI-1) to formula (DI-6).

[0183] In some embodiments, the aldehyde ketone polymer includes the structural unit shown in formula (DII).

[0184] In formula (DII), R 43 to R 46 each independently includes a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 hydroxyalkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; r and s are each independently selected from an integer from 0 to 5, and at least one of r and s is selected from a positive integer. Optionally, R 43 to R 46 each independently includes a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 hydroxyalkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; r and s are each independently selected from an integer from 0 to 5, and at least one of r and s is selected from a positive integer. Optionally, R

[0185] In some embodiments, the aldehyde ketone polymer includes at least one of the structural units shown in formula (DII-1) to formula (DII-4).

[0186] The aldehyde ketone polymer described above has a low degree of entanglement of molecular chains, which is beneficial to improve the flexibility of the molecular chains, and the molecular chains can be fully stretched in the electrolyte, which is beneficial to form a gel electrolyte with the electrolyte.

[0187] The polymer described above is only an example of the structural group of the main molecular chain, and in the embodiments of the present application, the polymer can also be obtained by copolymerization of the above-mentioned structural group and other types of structural groups. Other types of structural groups are, for example, olefin structural units, enol structural units, acrylonitrile structural units, etc.

[0188] When the above group is substituted, the substituent can include one or more of a nitrile group, a nitro group, a sulfonyl group, a carboxyl group, an ester group, a chlorine atom, a fluorine atom, and a bromine atom. The above substituent is a high-pressure resistant substituent, which is more conducive to stabilizing the structure of the polymer.

[0189] In some embodiments, each n is independently selected from a positive integer from 500 to 15000.

[0190] Alternatively, each n is independently selected from a positive integer from 500 to 10000.

[0191] In some embodiments, the molecular weight of the lyophilic polymer is from 1.2 x 10 5 g / mol to 1 x 10 6 g / mol.

[0192] Illustratively, the molecular weight of the lyophilic polymer can be about 1.2 x 10 5 g / mol, about 2 x 10 5 g / mol, about 5 x 10 5 g / mol, about 8 x 10 5 g / mol, about 1 x 10 6 g / mol, or any value within a range defined by any two of the above values.

[0193] The embodiments of the present application can further improve the cycle performance of the battery cell when the lyophilic polymer further satisfies one or more of the following conditions.

[0194] In some embodiments, the lyophilic polymer is added to the first solvent to form a polymer system at 70°C; the lyophilic polymer system is allowed to stand at 70°C for 8h and at 25°C for ≥24h, and after the two-stage standing treatment, part of the lyophilic polymer system is converted into a gel-state substance through swelling and adsorption, and then the polymer system is filtered through a 200-mesh filter screen to obtain a first substance. The mass of the lyophilic polymer is n, and the unit is g; the mass of the first substance is m, and the unit is g; the polymer and the first substance satisfy: 5≤m / n≤1000; alternatively, 10≤m / n≤1000; further alternatively, 10≤m / n≤50. Illustratively, m / n can be 5, 10, 20, 25, 28, 30, 32, 35, 40, 50, 80, 100, 200, 500, 1000, or any value within a range defined by any two of the above values.

[0195] Illustratively, the ratio of the mass content of the lyophilic polymer to the mass content of the first solvent based on the mass of the polymer system ranges from 1:100 to 1:10, for example, 3:50.

[0196] Exemplarily, the first solvent is the same as or similar to the solvent of the electrolyte, and the first solvent can include a carbonate solvent. For example, the carbonate solvent includes a cyclic carbonate solvent and / or a linear carbonate solvent.

[0197] As an example of the cyclic carbonate solvent, the cyclic carbonate solvent includes one or more of ethylene carbonate EC, vinylene carbonate VC, fluoroethylene carbonate FEC, difluoroethylene carbonate DFEC, vinyl ethylene carbonate VEC, and dioctyl carbonate CC.

[0198] As an example of the linear carbonate solvent, the linear carbonate solvent includes one or more of dimethyl carbonate DMC, diethyl carbonate DEC, ethyl methyl carbonate EMC, diphenyl carbonate DPC, methyl allyl carbonate MAC, and polycarbonate VA.

[0199] Optionally, the first solvent can also contain a lithium salt and an electrolyte additive, such as lithium hexafluorophosphate, vinylene carbonate VC, fluoroethylene carbonate FEC, etc.

[0200] In the present application, m / n is also referred to as a precipitation value, which characterizes the ability of the lyophilic polymer and the solvent to transform into a gel state substance.

[0201] The first substance mainly includes a gel state substance formed by the lyophilic polymer and the first solvent, and in the gel state substance, the molecular structure of the polymer does not change substantially.

[0202] In some embodiments, the first substance is dried at 80℃ for 12h to remove the first solvent in the first substance, and the dried first substance is detected by infrared spectrophotometry IR or nuclear magnetic resonance NMR test, and the main component of the dried first substance is the lyophilic polymer described above.

[0203] In the present application, the lyophilic polymer in the battery cell can be obtained by discharging the battery cell to 0% SOC, and then taking out the positive electrode sheet, the negative electrode sheet, and the separator, respectively. Taking the negative electrode sheet as an example: taking a negative electrode sheet with a mass of m1, washing it with a small amount of water to obtain a negative electrode powder, adding sufficient DMC solvent after drying at 80℃ for 4h, fully stirring to make the powder fully contact with the solvent, soaking at 60℃ for 24h, and then removing the solvent from the upper clear liquid by rotary evaporation to obtain a polymer film, and then obtaining the lyophilic polymer through washing, separation, etc. The lyophilic polymer in the positive electrode sheet and the separator can be obtained in a similar manner.

[0204] The related parameters of the lyotropic polymer of the embodiments of the present application can be detected by the following method: the groups of the lyotropic polymer of the embodiments of the present application can be detected by infrared spectrophotometry IR, specifically, the lyotropic polymer is tested by Thermo Nicolet Nexus 670 attenuated total reflection Fourier transform infrared spectrometer (abbreviated as: FTIR-ATR), and then tested by referring to the standard GB / T6040-2002, the test range: ATR method 600cm -1 ~4000cm -1 ; repeatability: ±2cm -1 ; resolution: better than 4cm -1 ; transmission depth 0.2μm~0.6μm.

[0205] The structure of the lyotropic polymer of the embodiments of the present application can be tested by nuclear magnetic resonance NMR, specifically, 1H NMR and 13C NMR are performed on a Varian Mercury Plus-400 nuclear magnetic resonance instrument, the test temperature is 20℃, TMS is an internal standard, CDCl3 is used as a solvent, and the proton resonance frequency is 400MHz.

[0206] The polymer monomer type of the lyotropic polymer of the embodiments of the present application can be tested by pyrolysis-gas chromatography-mass spectrometry. The specific test steps are as follows: accurately weigh 0.5mg of the sample into a sample cup, fix it on the sample rod, and then load it into a pyrolyzer installed near the gas chromatography (abbreviated as: GC) sample inlet. After the pyrolyzer temperature reaches the set temperature, press the sample button. The sample cup quickly falls into the pyrolysis furnace core by free fall, and the volatile components are instantly gasified in an inert gas N2 atmosphere, carried into the gas chromatography column by the carrier gas, separated, and finally detected by a flame ionization detector FID or a mass spectrometer MS, so as to obtain a gas chromatogram or a total ion current chromatogram.

[0207] The molecular weight of the lyotropic polymer of the embodiments of the present application is the meaning known in the art, and can be measured by using the commonly used equipment and methods in the art, and can be tested by gel permeation chromatography GPC. The specific test steps are as follows: take an appropriate amount of the sample to be tested, and the sample concentration can be ensured to be 8%-12% optical density, add 20ml of deionized water, and at the same time, ultrasonic for 5min under 53KHz / 120W to ensure that the sample is completely dispersed, and then the sample is measured according to the standard GB / T19077-2016 / ISO13320:2009.

[0208] Alternatively, the test is performed using a multi-angle laser light scattering instrument MALLS, specifically, an instrument using GPC with a Dawn Heleos II multi-angle laser light scattering device, an Optilab T-rEX refractive index detector, and a Visco Star II viscometer. The test is performed at 30°C, using tetrahydrofuran as the mobile phase, at a flow rate of 1.0 ml / min, and the SEC-SAMLL data is processed using a commercial software ASTRA6 to obtain the molecular weight parameters.

[0209] In some embodiments, the lithium ion transference number of the gel electrolyte is ≥ 0.4. The gel electrolyte has a large lithium ion transference number, which can facilitate the movement of lithium ions and make the intercalation and deintercalation of lithium ions easier, thereby further improving the cycle performance of the battery cell. Optionally, the lithium ion transference number of the gel electrolyte is 0.4, 0.5, 0.7, 0.8, 0.9, 1, etc.

[0210] The lithium ion transference number can be measured by using a constant potential polarization method. Specifically, a Li / electrolyte / Li symmetric battery structure is assembled. A small and constant potential difference ΔV is applied to the measured symmetric battery, and the change of current with time is recorded. The lithium ion transference number calculation formula is: wherein t + is the lithium ion transference number, δV is the applied potential difference, I0 is the initial current, R0 is the interface impedance of the electrode and electrolyte before polarization, I ss is the steady-state current, and R ss is the interface impedance of the electrode and electrolyte after polarization.

[0211] Another embodiment of the present application provides a battery. The battery includes a battery cell.

[0212] Another embodiment of the present application provides an electrical device. The electrical device includes a battery.

[0213] The battery cell, battery, and electrical device of the present application are described below with reference to the accompanying drawings.

[0214] Positive electrode tab

[0215] The positive electrode tab includes a positive electrode current collector and a positive electrode active layer disposed on at least one surface of the positive electrode current collector, and the positive electrode active layer includes a positive electrode active material.

[0216] As a non-limiting example, the positive electrode current collector has two opposite surfaces in the thickness direction of itself, and the positive electrode active layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0217] In some embodiments, in addition to the lithium nickel manganese cobalt oxide described above, the positive electrode active material can also include positive electrode active materials for batteries known in the art. As non-limiting examples, positive electrode active materials for batteries known in the art include, but are not limited to, one or more of lithium-containing phosphates, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof, etc. Non-limiting examples of lithium-containing phosphates can include, but are not limited to, one or more of lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon. Non-limiting examples of lithium cobalt oxide can include LiCoO2; non-limiting examples of lithium nickel oxide can include LiNiO2; non-limiting examples of lithium manganese oxide can include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt aluminum oxide can include LiNi 0.8 Co 0.15 Al 0.05 O2.

[0218] In some embodiments, the positive electrode active layer can also optionally include a binder. As non-limiting examples, the binder can include one or more of polyvinylidene fluoride (abbreviated: PVDF), polytetrafluoroethylene (abbreviated: PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0219] In some embodiments, the positive electrode active layer can also optionally include a conductive agent. As non-limiting examples, the conductive agent can include one or more of super P carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0220] In some embodiments, the positive electrode tab can be prepared by dispersing the components described above for preparing the positive electrode tab, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one side surface of the positive electrode current collector, and after processes such as drying, cold pressing, etc., the positive electrode tab can be obtained. The type of solvent can be selected from, but is not limited to, any of the foregoing embodiments, such as N-methyl pyrrolidone (abbreviated: NMP). The surface of the positive electrode current collector on which the positive electrode slurry is coated can be on a single surface of the positive electrode current collector, or on both surfaces of the positive electrode current collector. The surface of the positive electrode current collector on which the positive electrode slurry is coated can be on a single surface of the positive electrode current collector, or on both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40wt% to 80wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000mPa·s to 25000mPa·s.

[0221] Negative electrode sheet

[0222] The negative electrode sheet includes a negative current collector and a negative active layer disposed on at least one surface of the negative current collector, the negative active layer including a negative active material.

[0223] As a non-limiting example, the negative current collector has two surfaces opposite in the thickness direction thereof, and the negative active layer is disposed on either one or both of the two opposite surfaces of the negative current collector.

[0224] In some embodiments, the negative active material can further include a negative active material for a battery as known in the art. As a non-limiting example, the negative active material can include one or more of other carbon-based materials other than the above-described graphite, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material can include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material can include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative active material for a battery can also be used. These negative active materials can be used alone or in combination with two or more.

[0225] In some embodiments, the negative active layer can further optionally include a binder. The binder can include one or more of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0226] In some embodiments, the negative active layer can further optionally include a conductive agent. The conductive agent can include one or more of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0227] In some embodiments, the negative active layer can further optionally include other auxiliary agents such as a thickening agent, etc. The thickening agent can be sodium carboxymethyl cellulose (CMC-Na).

[0228] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent, for example, deionized water, to form a negative electrode slurry; coating the negative electrode slurry on at least one side surface of the negative electrode current collector; and drying, cold-pressing, or the like, to obtain the negative electrode sheet. The surface of the negative electrode current collector to which the negative electrode slurry is coated can be a single surface of the negative electrode current collector or both surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40 wt% to 60 wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000 mPa·s to 10000 mPa·s.

[0229] Electrolyte

[0230] The electrolyte has the function of conducting ions between the positive electrode sheet and the negative electrode sheet. The electrolyte can be liquid, gel, or all-solid.

[0231] In some embodiments, the limiting electrolyte and the free electrolyte of the present application include an electrolyte salt and a solvent.

[0232] In some embodiments, the electrolyte salt can include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluoro-oxalato-borate (LiDFOB), lithium bis-oxalato-borate (LiBOB), lithium difluoro-bis-oxalato-phosphate (LiDFOP), and lithium tetrafluoro-oxalato-phosphate (LiTFOP).

[0233] In some embodiments, the solvent can include one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate, fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0234] In some embodiments, the electrolyte can optionally further include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature or low-temperature performance of the battery, etc.

[0235] In some embodiments, the additive in the electrolyte can include, but is not limited to, one or more of fluoroethylene carbonate (abbreviated as FEC), difluoroethylene carbonate (abbreviated as DFEC), trifluoromethyl ethylene carbonate (abbreviated as TFPC), etc.

[0236] Separator film

[0237] In some embodiments, the separator film can be any known porous structure separator film having good chemical stability and mechanical stability.

[0238] In some embodiments, the material of the separator film can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator film is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0239] In some embodiments, the thickness of the separator film can be 6 μm to 40 μm, and can be optionally 12 μm to 20 μm.

[0240] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator film can be used to make an electrode assembly through a winding process or a stacking process.

[0241] In some embodiments, the housing of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The housing of the battery cell can also be a soft pack, such as a pouch soft pack. The material of the soft pack can be plastic, and further non-limiting examples of the plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0242] The battery includes at least one battery cell. The battery can include one or more battery cells.

[0243] The shape of the battery cell is not particularly limited, and can be cylindrical, square, or any other shape. For example, FIG. 1 is a battery cell 1 in a square structure as an example. The battery cell 1 includes a housing 11 having an opening. An end cap 13 is used to cover the opening. An electrode terminal 14 is provided on the end cap. In the direction of gravity, the electrode terminal 14 is located at the bottom of the housing.

[0244] Referring to FIG. 2, the housing 11 can include a bottom plate and side plates connected to the bottom plate, which enclose a receiving cavity. The end cover 13 can be provided on the opening to seal the receiving cavity. The positive electrode tab, the negative electrode tab, and the separator can form the electrode assembly 12 through a winding process or a stacking process. The electrode assembly 12 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 12. The number of the electrode assembly 12 included in the battery cell 1 can be one or more, which can be selected by a person skilled in the art according to actual needs.

[0245] The battery can be a battery module or a battery pack.

[0246] The battery module includes at least one battery cell. The number of the battery cell included in the battery module can be one or more, which can be selected by a person skilled in the art according to the application and capacity of the battery module.

[0247] In the battery module, the plurality of battery cells can be arranged in sequence along the length direction of the battery module. Of course, other arbitrary arrangements can also be used. Further, the plurality of battery cells can be fixed by fasteners.

[0248] Optionally, the battery module can further include a housing having a receiving space, and the plurality of battery cells are received in the receiving space.

[0249] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack. The number of the battery module included in the battery pack can be one or more, which can be selected by a person skilled in the art according to the application and capacity of the battery pack.

[0250] The battery pack can include a battery box and a plurality of battery modules arranged in the battery box. The battery box includes an upper box body and a lower box body. The upper box body can be provided on the lower box body and form a closed space for receiving the battery modules. The plurality of battery modules can be arranged in the battery box in any manner.

[0251] In addition, the present application also provides a power utilization device including the battery provided by the present application. The battery can be used as a power source of the power utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device, an electric vehicle, an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto. The mobile device can be a mobile phone, a notebook computer, etc., for example; the electric vehicle can be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but is not limited thereto.

[0252] As the power utilization device, the battery can be selected according to the use requirements thereof.

[0253] FIG. 3 is an example of an electric device 2. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the demand of the electric device for a battery with high power and high energy density, a battery pack or a battery module can be used.

[0254] The device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The device generally requires thinning, and a battery can be used as a power source.

[0255] In order to make the technical problems, technical solutions and beneficial effects solved in the present application clearer, the present application will be further described in detail below in combination with embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and in no way limits the present application and its application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0256] Unless specific techniques or conditions are specified in the embodiments, the techniques or conditions described in the literature in the art or according to the product instructions are used. Unless the manufacturer of the reagent or instrument is specified, it is a conventional product that can be obtained by purchase on the market.

[0257] Embodiment 1

[0258] (1) Preparation of the positive electrode sheet

[0259] The positive electrode active material, the conductive agent carbon black, and the binder PVDF were added into N-methyl pyrrolidone (NMP for short) in a mass percentage of 98.4%:0.4%:1.2% to mix and prepare a positive electrode slurry. The positive electrode slurry was coated on an aluminum foil with a thickness of 12 μm and dried at 85°C, followed by cold pressing, then edge cutting, sheet cutting, and striping, and dried at 85°C under vacuum for 4 h to prepare a positive electrode sheet. The density of the positive electrode active layer in the positive electrode sheet was 3.5 g / cm 3 .

[0260] (2) Preparation of the negative electrode sheet

[0261] The lyophilic polymer, graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR for short), and thickening agent sodium methyl cellulose (CMC-Na for short) were added into deionized water in a mass percentage of 3%:94%:0.5%:1.5%:1% to mix and prepare a negative electrode slurry. The negative electrode slurry was coated on a copper foil with a thickness of 8 μm and dried at 85°C, followed by cold pressing, then edge cutting, sheet cutting, and striping, and dried at 120°C under vacuum for 12 h to prepare a negative electrode sheet. The density of the negative electrode active layer in the negative electrode sheet was 1.6 g / cm3 The content of the hydrophilic polymer in the negative active layer is 3% by mass percentage.

[0262] (3) Separator film

[0263] A polyethylene substrate with a boehmite coating layer having a thickness of 2 μm on the surface thereof.

[0264] (4) Preparation of electrolyte

[0265] In an environment with a water content of less than 10 ppm, non-aqueous organic solvents ethylene carbonate DMC and methyl ethyl carbonate EMC are mixed in a mass ratio of 1:9 to obtain an electrolyte solvent, and then lithium salt LiPF6 is mixed with the mixed solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L, and 1% wt VC and 3% wt FEC additives are added.

[0266] (5) Preparation of battery monomer

[0267] The above positive electrode sheet, separator film and negative electrode sheet are stacked in order, with the separator film between the positive electrode sheet and the negative electrode sheet to play a separating role, and then wound to obtain an electrode assembly; the electrode assembly is placed in an aluminum shell, dried, and then injected with electrolyte, and then subjected to vacuum packaging, standing, formation, shaping and other processes to obtain a battery monomer.

[0268] Examples 2-14 and Comparative Example 1

[0269] The differences between Examples 2-14 and Comparative Example 1 compared to Example 1 are shown in Table 1.

[0270] Comparative Example 2

[0271] Compared to Example 1, the difference between Comparative Example 1 is that the hydrophilic polymer in the positive active layer is replaced by a positive active material, and the hydrophilic polymer in the negative active layer is replaced by a negative active material. That is, the battery monomer of Comparative Example 2 does not contain a hydrophilic polymer.

[0272] Test Example

[0273] (1) The mass energy density of the battery monomer in the examples and comparative examples was tested, and the test method was as follows: the battery monomer was charged at 0.33C constant current to 4.2V, and then charged at constant voltage to the cutoff current 0.05C; then the battery monomer was discharged at 0.33C constant current to 2.8V, and the discharge energy was recorded, the unit of discharge energy was Wh. The mass of the battery monomer was weighed, the unit of the mass of the battery monomer was kg, and the unit mass energy density of the battery monomer was calculated from the discharge energy / mass, the unit was Wh / kg.

[0274] (2) The cycle performance of the battery cells in the examples and comparative examples was tested by the following method: the capacity of the battery cell before cycling was tested; the battery cell was charged at 0.33C to 10% SOC, at 3C to 15% SOC, at 2C to 20% SOC, at 1.5C to 15% SOC, at 1C to 20% SOC, and then charged at 0.33C to 100% SOC at a constant current, with a cut-off voltage of 4.2V, and charged at 4.2V to 0.05C at a constant voltage; the battery cell was discharged at 0.5C to 5% SOC at a cut-off voltage of 2.8V; the cycle was repeated 1600 times, the capacity of the battery after cycling was tested, and the cycle retention rate after 1100 cycles was calculated.

[0275] (3) The battery cell leakage was tested by the following method: the battery cell was charged to 100% SOC, and then stored upside down at 45°C, the voltage of the battery cell was recorded, and the corrosion of the explosion-proof valve and the aluminum shell was observed. If there is abnormal voltage fluctuation or corrosion of the explosion-proof valve and the aluminum shell, there is a long-term risk of leakage.

[0276] Table 1

[0277] In Table 1, X c2 represents the cold crystallinity of the lyophilic polymer. Tc2 represents the cold crystallization temperature of the lyophilic polymer, in °C. The unit of molecular weight is 10,000 g / mol. a represents the mass percentage of the lyophilic polymer in the positive electrode active layer. b represents the mass percentage of the lyophilic polymer in the negative electrode active layer. c represents the volume of the free electrolyte in the battery cell, in mL. In the column of "monomer", VDF+HFP represents that the monomers of the lyophilic polymer are VDF and HFP, and the values in the parentheses represent the mole percentage of VDF and HFP based on the total mole ratio of VDF and HFP monomers. For example, VDF+HFP (91%:9%) represents that the mole percentages of VDF and HFP are 91% and 9%, respectively, based on the total mole ratio of VDF and HFP monomers.

[0278] By testing the leakage of the battery cells in the examples and comparative examples, the battery cells in Comparative Example 1 leaked, and the battery cells in the examples and Comparative Example 2 did not leak.

[0279] Table 2

[0280] As can be seen from Table 2, when the battery cell contains a lyophilic polymer and has a small amount of free electrolyte, the battery cell can have both high energy density and good cycle performance.

[0281] Table 3

[0282] As can be seen from Table 3, when the volume of the free electrolyte in the battery cell is less than or equal to 10 mL, the battery cell has good cycle performance.

[0283] Table 4

[0284] As can be seen from Table 4, when the mole ratio of the lyophilic polymer monomer is in a suitable range, the battery cell has good cycle performance.

[0285] Table 5

[0286] As can be seen from Table 5, when the mass percentage of the lyophilic polymer in the positive active layer is 0.1% to 2% and the mass percentage of the lyophilic polymer in the negative active layer is 1% to 5%, the battery cell has good cycle performance.

[0287] Table 6

[0288] As can be seen from Table 6, in the lithium nickel manganese cobalt oxide, when the mole percentage of the nickel element is 80% to 95% in terms of the mole percentage of the nickel element, the manganese element and the cobalt element, the battery cell can have both high energy density and good cycle performance.

[0289] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, but as long as the combinations of the technical features do not contradict each other, they should be considered within the scope of the present disclosure.

[0290] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled persons in the art, some modifications and improvements can be made without departing from the concept of the present application, and these are within the scope of the present application. Therefore, the scope of the patent of the present application should be subject to the appended claims.

Claims

1. A battery cell, comprising: a housing having an opening; an end cap for covering the opening; an electrode terminal provided on the end cap; the electrode terminal is located at a bottom of the housing in a direction of gravity; an electrode assembly accommodated in the housing; the electrode assembly comprises a positive electrode tab, a separator, and a negative electrode tab, the separator is provided between the positive electrode tab and the negative electrode tab; at least one of the positive electrode tab, the separator, and the negative electrode tab contains a gel electrolyte; the gel electrolyte comprises a lyophilic polymer and a confined electrolyte, the confined electrolyte is located inside the lyophilic polymer; the housing contains less than or equal to 10 mL of free electrolyte. The housing contains less than or equal to 2 mL of free electrolyte. The housing is made of one or more of aluminum, aluminum alloy, and stainless steel. The gel electrolyte is uniformly distributed in at least one of the positive electrode tab, the separator, and the negative electrode tab. The positive electrode tab comprises a positive current collector and a positive active layer on at least one surface of the positive current collector, the positive active layer contains the gel electrolyte and a positive active material. The gel electrolyte satisfies one or more of the following characteristics: (1) the gel electrolyte is distributed on the surface of the positive active material particles; and (2) the gel electrolyte is distributed at the pores between the positive active material particles.

2. The battery cell of claim 1, wherein, The positive active layer contains 0.1%to 2%of the lyophilic polymer by mass percentage of the positive active layer.

3. The battery cell of claim 1 or 2, wherein, The positive active material comprises one or more of lithium nickel manganese cobalt oxide and lithium-containing phosphate; the lithium nickel manganese cobalt oxide contains 50%to 95%of nickel element by mole percentage of nickel element, manganese element, and cobalt element, optionally 80%to 95%.

4. The battery cell according to any one of claims 1 to 3, wherein, The positive current collector comprises a first support layer and a first metal layer on at least one surface of the first support layer, the first metal layer is located between the first support layer and the positive active layer.

5. The battery cell of any one of claims 1-4, wherein, The first metal layer has a thickness of 200 nm to 2000 nm.

6. The battery cell of claim 5, wherein, The negative electrode tab comprises a negative current collector and a negative active layer on at least one surface of the negative current collector, the negative active layer contains the gel electrolyte and a negative active material. The gel electrolyte satisfies one or more of the following characteristics: (1) the gel electrolyte is distributed on the surface of the negative active material particles; and 7. The battery cell of claim 5 or 6, wherein, (2) the gel electrolyte is distributed at the pores between the negative active material particles.

8. The battery cell of any one of claims 5-7, wherein, The negative active layer contains 1%to 5%of the lyophilic polymer by mass percentage of the negative active layer.

9. The battery cell of any one of claims 5-8, wherein, The density of the positive electrode active layer is 2 g / cm 3 ~ 3.8 g / cm 3 ; Optionally, the positive active material includes lithium nickel cobalt manganese oxide, and the density of the positive active layer is 3.5 g / cm 3 ~ 3.8 g / cm 3 ; Optionally, the positive active material includes a lithium-containing phosphate, and the density of the positive active layer is 2 g / cm 3 ~ 3 g / cm 3 .

10. The battery cell of any one of claims 5-9, wherein, The negative current collector comprises a second support layer and a second metal layer on at least one surface of the second support layer, the second metal layer is located between the second support layer and the negative active layer.

11. The battery cell of claim 10, wherein, The second metal layer has a thickness of 200 nm to 2000 nm.

12. The battery cell of any one of claims 1-11, wherein, The gel electrolyte is distributed at the pores of the separator.

13. The battery cell of claim 12, wherein, ​ ​ ​ 14. The battery cell of claim 12 or 13, wherein, ​ 15. The battery cell of any one of claims 12-14, wherein, The density of the negative active layer is 1 g / cm 3 ~ 2 g / cm 3 , optionally 1.3 g / cm 3 ~ 1.7 g / cm 3 .

16. The battery cell of any one of claims 12-15, wherein, ​ 17. The battery cell of claim 16, wherein, ​ 18. The battery cell of any one of claims 1-17, wherein, ​ 19. The battery cell of any one of claims 1-18, wherein, The separator film includes a separator film substrate and a coating layer on at least one surface of the separator film substrate, the coating layer containing a particulate filler; Optionally, the particulate filler includes one or more of boehmite, alumina, silica, and magnesium hydroxide. Optionally, the thickness of the coating layer is 0.25 μm to 5 μm. Optionally, the material of the separator film substrate includes one or more of polyethylene, polypropylene, polyimide, and aramid.

20. The battery cell of any one of claims 1-19, wherein, The lyophilic polymer comprises a fluorinated polymer; the fluorinated polymer has a crystallinity X measured by differential scanning calorimetry c1 , 15%≤X c1 ≤25%; the fluorinated polymer has a melting temperature T m1 , in °C, 120≤T m1 ≤140.

21. The battery cell of any one of claims 1-19, wherein, The cold crystallinity of the fluorinated polymer, measured by differential scanning calorimetry, is X. c2 10% < X c2 ≤25%; the cold crystallization temperature of the fluorinated polymer is Tc2, in °C, 35≤Tc2. c2 ≤65.

22. The battery cell of claim 20 or 21, wherein, The monomers of the fluoropolymer include hexafluoropropylene and vinylidene fluoride. Optionally, the mole percentage of the hexafluoropropylene is 6% to 13% based on the total mole ratio of the hexafluoropropylene and the vinylidene fluoride.

23. The battery cell of any one of claims 20-22, wherein, The fluoropolymer includes at least one of a structural unit represented by Formula (AI) to a structural unit represented by Formula (AIII), In formula (AI) and formula (AII), R 11 , R 12 , R 13 , and R 14 each independently include a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and R 11 , R 12 , R 13 , and R 14 at least one of which includes a fluorine atom; when substituted, the substituent includes one or more of a nitrile group, a nitro group, a sulfonic acid group, a sulfonyl group, an amide, a carboxyl group, an ester group, a halogen atom; In formula (AIII), R 15 including a single bond, substituted or unsubstituted C1-C3 alkyl; when substituted, the substituent includes one or more of a nitrile group, a nitro group, a sulfonic acid group, a sulfonyl group, an amide, a carboxyl group, an ester group, a halogen atom; p is a positive integer selected from 1 to 3; n is each independently a positive integer selected from 1000 to 30000.

24. The battery cell of any one of claims 1-23, wherein, The lyotropic polymer has a molecular weight of 1.2 x 10 5 g / mol to 1 x 10 6 g / mol.

25. The battery cell of any one of claims 1-24, wherein, The lithium ion transference number of the gel electrolyte is ≥0.

4.

26. A battery including the battery cell of any one of claims 1 to 25.

27. An electric device including the battery of claim 26.