Battery monomer, battery and electric device

Abstract

The invention provides a battery monomer, a battery and a power utilization device. In the battery monomer, the electrolyte can be limited in the lyophilic polymer through the use of the gel electrolyte, and at the moment, the limiting electrolyte can well play the role of the electrolyte, so that the amount of free electrolyte in the battery monomer can be greatly reduced, the corrosion of the free electrolyte to a welding seam is reduced, and the risk of liquid leakage of the battery monomer is reduced.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery cell, a battery, and an electrical device. Background Technology

[0002] The statements herein are provided only as background information in connection with this application and do not necessarily constitute prior art.

[0003] Lithium-ion batteries and other types of batteries are widely used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, aerospace, and many other fields. During the use of individual battery cells, it may be necessary to invert them to expand their application scenarios. However, the end caps of battery cells are usually welded to the casing, and the weld seam is a relatively weak point. When the battery cell is inverted, a large amount of electrolyte will come into full contact with the weld seam, which may corrode the weld seam and cause leakage. Summary of the Invention

[0004] A first aspect of this application provides a battery cell, characterized in that it comprises: a housing having an opening;

[0005] End cap for closing the opening; electrode terminal disposed on the end cap; the electrode terminal located at the bottom of the housing along the direction of gravity; electrode assembly housed within the housing;

[0006] The electrode assembly includes a positive electrode, a separator, and a negative electrode, with the separator disposed between the positive and negative electrodes; at least one of the positive electrode, the separator, and the negative electrode contains a gel electrolyte; the gel electrolyte includes a hydrophilic polymer and a limiting electrolyte, with the limiting electrolyte located inside the hydrophilic polymer; and the free electrolyte in the housing is less than or equal to 10 mL.

[0007] In the aforementioned battery cells, the use of gel electrolytes can confine the electrolyte within the hydrophilic polymer. In this case, the confining electrolyte can better perform its function, which can significantly reduce the amount of free electrolyte in the battery cell, reduce the corrosion of the weld by the free electrolyte, and lower the risk of leakage in the battery cell.

[0008] In some embodiments, the free electrolyte in the housing is less than or equal to 2 mL.

[0009] In some embodiments, the casing is made of 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.

[0010] 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, separator, and negative electrode, which further promotes sufficient wetting of these components by the electrolyte and improves the cycle performance of the battery cell.

[0011] 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 containing the gel electrolyte and the positive active material.

[0012] In some embodiments, the gel electrolyte is distributed on the surface of the positive electrode active material particles. The gel electrolyte distribution on the surface of the positive electrode active material particles can protect the particles, reduce side reactions between the positive electrode active material particles and the electrolyte, and further improve the cycle performance of the battery cell.

[0013] In some embodiments, the gel electrolyte is distributed in the pores between the particles of the positive electrode active material. This allows more electrolyte to be confined within the positive electrode, further improving the cycle performance of the battery cell.

[0014] In some embodiments, the hydrophilic polymer accounts for 0.1% to 2% of the mass percentage of the positive electrode active layer. This range allows the limiting electrolyte to maintain a suitable quantity within the positive electrode active layer, resulting in better compatibility between the limiting electrolyte and the positive electrode active material, and further improving the cycle performance of the battery cell.

[0015] In some embodiments, the positive electrode active material includes one or more of lithium nickel manganese cobalt oxide and lithium phosphate; in the lithium nickel manganese cobalt oxide, the molar percentage of nickel is 50% to 95%, optionally 80% to 95%, based on the molar percentage of nickel, manganese, and cobalt. Lithium nickel manganese cobalt oxides with a molar percentage of nickel within this range have higher specific capacity, which is beneficial for further improving the energy density of the battery cell.

[0016] In some embodiments, the density of the positive electrode active layer is 2 g / cm³. 3 ~3.8g / cm 3 Within this range, the density of the positive electrode active layer allows the battery cell to have a suitable weight and a high energy density.

[0017] In some embodiments, the positive electrode active material comprises lithium nickel cobalt manganese oxide, and the density of the positive electrode active layer is 3.5 g / cm³. 3 ~3.8g / cm 3 .

[0018] In some embodiments, the positive electrode active material comprises lithium phosphate, and the density of the positive electrode active layer is 2 g / cm³. 3 ~3g / cm 3 .

[0019] In some embodiments, the positive electrode current collector includes a first support layer and a first metal layer, the first metal layer being located on at least one surface of the first support layer and between the first support layer and the positive electrode active layer. The positive electrode current collector employs a composite current collector design, which reduces its weight compared to a pure metal current collector, thus contributing to a further increase in the energy density of the battery cell.

[0020] In some embodiments, the thickness of the first metal layer is 200 nm to 2000 nm.

[0021] In some embodiments, the negative electrode sheet includes a negative current collector and a negative active layer located on at least one surface of the negative current collector, the negative active layer containing the gel electrolyte and the negative active material.

[0022] In some embodiments, the gel electrolyte is distributed on the surface of the negative electrode active material particles. The gel electrolyte distribution on the surface of the negative electrode active material particles can protect the particles, reduce side reactions between the negative electrode active material particles and the electrolyte, and further improve the cycle performance of the battery cell.

[0023] In some embodiments, the gel electrolyte is distributed in the pores between the particles of the negative electrode active material. This allows more electrolyte to be confined within the negative electrode, further improving the cycle performance of the battery cell.

[0024] In some embodiments, the hydrophilic polymer accounts for 1% to 5% of the mass percentage of the negative electrode active layer. This range allows the limiting electrolyte to maintain a suitable quantity within the negative electrode active layer, resulting in better compatibility between the limiting electrolyte and the negative electrode active material, and further improving the cycle performance of the battery cell.

[0025] In some embodiments, the density of the negative electrode active layer is 1 g / cm³. 3 ~2g / cm 3 Optionally, it can be 1.3 g / cm³. 3 ~1.7g / cm3 .

[0026] In some embodiments, the negative electrode current collector includes a second support layer and a second metal layer, the second metal layer being located on at least one surface of the second support layer and between the second support layer and the negative electrode active layer. The negative electrode current collector adopts a composite current collector form, which can reduce the weight of the negative electrode current collector compared to a pure metal current collector, thus helping to further improve the energy density of the battery cell.

[0027] In some embodiments, the thickness of the second metal layer is 200 nm to 2000 nm.

[0028] In some embodiments, the gel electrolyte is distributed in the pores of the separator. This allows more electrolyte to be confined within the separator, promoting the transport of active ions and further improving the cycle performance of the battery cell.

[0029] In some embodiments, the separator includes a separator substrate and a coating on at least one surface of the separator substrate, the coating containing particulate filler. The coating containing particulate filler has good heat resistance and high strength, which can improve the heat resistance and strength of the separator, enabling the separator to maintain a relatively stable structure during battery cell cycling and further promoting the improvement of battery cell cycle performance. Optionally, the particulate filler includes one or more of boehmite, alumina, silicon dioxide, and magnesium hydroxide.

[0030] In some embodiments, the thickness of the coating is 0.25 μm to 5 μm.

[0031] In some embodiments, the material of the separator substrate includes one or more of polyethylene, polypropylene, polyimide, and aramid.

[0032] In some embodiments, the hydrophilic polymer comprises a fluorinated polymer; the crystallinity of the fluorinated polymer, as determined by differential scanning calorimetry, is X. c1 15%≤X c1 ≤25%; the melting temperature of the fluoropolymer is T m1 Its unit is ℃, 120≤T m1 ≤140.

[0033] In some embodiments, the cold crystallinity of the fluorinated polymer, as 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.

[0034] In some embodiments, the monomers of the fluorinated polymer include hexafluoropropylene and vinylidene fluoride.

[0035] In some embodiments, the molar percentage of hexafluoropropylene is 6% to 13% based on the total molar ratio of the hexafluoropropylene and the vinylidene fluoride.

[0036] In some embodiments, the fluoropolymer includes at least one of the structural units represented by formula (A1) to formula (AIII).

[0037] Formula (AI) Formula (AII),

[0038] In equations (AI) and (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 them contains a fluorine atom; when substituted, the substituents include one or more of the following: nitrile (-CN), nitro, sulfonic acid, sulfonyl, amide, carboxyl, ester, and halogen atom;

[0039] Formula (AIII);

[0040] In equation (AIII), R 15 Includes single bonds, substituted or unsubstituted C1-C3 alkyl groups; when substituted, the substituents include one or more of nitrile (-CN), nitro, sulfonic acid, sulfonyl, amide, carboxyl, ester, and halogen atoms; p is selected from positive integers from 1 to 3; n is selected from positive integers from 1000 to 30000.

[0041] In some embodiments, the molecular weight of the hydrophilic polymer is 1.2 × 10⁻⁶. 5 g / mol to 1×10 6 g / mol.

[0042] In some embodiments, the lithium-ion transference number of the gel electrolyte is ≥0.4.

[0043] A second aspect of this application provides a battery. The battery includes the battery cell.

[0044] A third aspect of this application provides an electrical device. The electrical device includes the battery. Attached Figure Description

[0045] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0046] Figure 1 This is a schematic diagram of a battery cell according to one embodiment of this application.

[0047] Figure 2 for Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown.

[0048] Figure 3 This is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to one embodiment of this application.

[0049] Explanation of reference numerals in the attached figures:

[0050] 1. Battery cell; 11. Housing; 12. Electrode assembly; 13. End cap; 14. Electrode terminal; 2. Electrical device. Detailed Implementation

[0051] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0052] 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 herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0053] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints. Any endpoint can be independently included or excluded, and they can be combined arbitrarily; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0054] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0055] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0056] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The term "implementation" as used herein has a similar understanding.

[0057] Those skilled in the art will understand that the order in which the steps are written in the methods of various embodiments or examples does not imply 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. Unless otherwise specified, all steps of this application may be performed sequentially or randomly. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0058] In this application, open-ended technical features or solutions described using terms such as "containing," "including," or "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may also include other members or exclude additional members unless otherwise specified. This can be considered as providing both the feature or solution that "A consists of a1, a2, and a3" and the feature or solution that "A includes not only a1, a2, and a3, but also other members."

[0059] In this application, unless otherwise specified, A (e.g., B) means that B is a non-limiting example of A, and it is understood that A is not limited to B.

[0060] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0061] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0062] In this application, unless otherwise specified, "cell battery" refers to the basic unit capable of converting chemical energy into electrical energy, and generally includes at least a positive electrode, a negative electrode, and an electrolyte. During the charging and discharging process of the battery, active ions move back and forth between the positive and negative electrode plates, inserting and extracting. The electrolyte acts as a conductor for the active ions between the positive and negative electrode plates.

[0063] One embodiment of this application provides a battery cell, comprising: a housing having an opening; an end cap for closing the opening; electrode terminals disposed on the end cap; the electrode terminals being located at the bottom of the housing along the direction of gravity; an electrode assembly housed within the housing; the electrode assembly including a positive electrode, a separator, and a negative electrode, the separator being disposed between the positive and negative electrode; at least one of the positive electrode, the separator, and the negative electrode containing a gel electrolyte; the gel electrolyte including a hydrophilic polymer and a limiting electrolyte, the limiting electrolyte being located inside the hydrophilic polymer; and the free electrolyte in the housing being less than or equal to 10 mL.

[0064] In the battery cell of this embodiment, the use of gel electrolyte can confine the electrolyte inside the hydrophilic polymer. At this time, the confined electrolyte can better play its role, which can significantly reduce the amount of free electrolyte in the battery cell, reduce the corrosion of the weld by the free electrolyte, and reduce the risk of leakage of the battery cell.

[0065] Understandably, when the free electrolyte in the casing is zero, the limiting electrolyte in the gel electrolyte and the electrolyte that may be adsorbed into the electrode assembly can function as electrolytes, maintaining good cycle performance of the battery cell. When the casing contains a small amount of free electrolyte, the free electrolyte can replenish the electrolyte in the electrode assembly as it is consumed, maintaining relatively stable cycle performance of the battery cell. When the free electrolyte in the casing is less than or equal to 10 mL, the risk of leakage in the battery cell can be reduced while maintaining good cycle performance.

[0066] In some embodiments, the free electrolyte in the casing 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 within the range of any two of the above values. Optionally, the free electrolyte in the casing is less than or equal to 2 mL.

[0067] After the electrolyte is injected into the battery cell, the electrolyte mainly exists in the following forms: first, electrolyte that may be adsorbed in the electrode assembly; second, confined electrolyte located inside the hydrophilic polymer; and third, free electrolyte that may be free in the battery cell.

[0068] 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 and fill it to 0% SOC. Weigh the battery cell, and the mass is M1. Make a hole with a diameter of φ5mm~8mm at a local location in the battery cell. Place the battery cell on top of a container with the hole facing down and directly above the container, so that the free electrolyte inside the battery cell can drip into the container below. Let the battery cell stand like this for 3h~5h to allow all the free electrolyte inside to drip into the container. Then weigh the volume of electrolyte in the container, which is the volume of free electrolyte in the battery cell casing. The battery cells are then disassembled. Each component is dried at 60℃~95℃ for 24h~48h, then immersed in dimethyl carbonate (DMC) solvent for 12h, and then dried again at 60℃~95℃ for 24h~48h. This soaking and drying process is repeated twice. The dried components are then weighed, and the total weight is recorded as M2. In this testing method, a fresh battery cell can be a newly manufactured battery cell (not yet charged / discharge cycled after formation) or a battery cell assembled in an electrical device and used for less than 10 cycles. The mass of the electrolyte injected into the battery cell is M1-M2.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] The gel electrolyte is distributed on the surface of the positive electrode active material particles, meaning it is located on the surface of the positive electrode active layer away from the positive electrode current collector. For example, a film layer including the positive electrode active material is formed on the surface of the positive electrode current collector, and the gel electrolyte is located on the surface of the film layer away from the positive electrode current collector. Optionally, the preparation of this type of positive electrode sheet includes the following steps: coating a positive electrode slurry including the positive electrode active material onto the surface of the positive electrode current collector, drying and curing to obtain a film layer, and then depositing a hydrophilic polymer on the surface of the film layer. When the hydrophilic polymer comes into contact with the electrolyte, it adsorbs the electrolyte to form a gel electrolyte. This results in a structure where the gel electrolyte is distributed on the surface of the positive electrode active material particles. It is understood that the positive electrode slurry may also include binders and conductive agents, etc.

[0073] In some embodiments, the gel electrolyte is distributed in the pores between the particles of the positive electrode active material. This allows for greater confinement of the electrolyte within the positive electrode, further improving the cycle performance of the battery cell. Optionally, the preparation of this type of positive electrode includes the following steps: mixing a hydrophilic polymer and the positive electrode active material in a solvent to obtain a positive electrode slurry; then coating the positive electrode slurry onto the surface of a positive electrode current collector; and finally drying and curing to obtain a film layer. When the film layer comes into contact with the electrolyte, the hydrophilic polymer adsorbs the electrolyte to form a gel electrolyte. This results in a structure where the gel electrolyte is distributed in the pores between the particles of the positive electrode active material. It is understood that the positive electrode slurry may also include binders and conductive agents.

[0074] In some embodiments, the hydrophilic polymer constitutes 0.1% to 2% of the positive electrode active layer by mass. This mass percentage range allows for a suitable retention of the limiting electrolyte within the positive electrode active layer, resulting in better compatibility between the limiting electrolyte and the positive electrode active material, and further improving the cycle performance of the battery cell. Optionally, the mass percentage of the hydrophilic polymer in the positive electrode 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 of any two of the above values. More preferably, the hydrophilic polymer constitutes 0.1% to 1% of the positive electrode active layer by mass.

[0075] In some embodiments, the positive electrode active material includes lithium nickel manganese cobalt oxide; in the lithium nickel manganese cobalt oxide, the molar percentage of nickel, based on the molar percentage of nickel, manganese, and cobalt, is 80% to 95%. Lithium nickel manganese cobalt oxides with a nickel molar percentage within this range have higher specific capacity, which is beneficial for further improving the energy density of the battery cell. Optionally, the molar percentage of nickel, based on the molar percentage of nickel, manganese, and cobalt, can be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, or any value within the range 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.

[0076] In some embodiments, the density of the positive electrode active layer is 2 g / cm³. 3 ~3.8g / cm 3 Within this density range, the positive electrode active layer can achieve a suitable weight and high energy density in the battery cell. For example, the density of the positive electrode active layer can be 2 g / cm³. 3 2.1g / cm 3 2.2g / cm 3 2.3g / cm 3 2.4g / cm 3 2.5g / cm 3 2.6g / cm 3 2.7g / cm 3 2.8g / cm 3 2.9g / cm 3 3g / cm 3 3.1g / cm 3 3.2g / cm 3 3.3g / cm 3 3.4g / cm 3 3.5g / cm 3 3.6g / cm 3 3.7g / cm 3 3.8g / cm 3 Or any value within the range consisting of any two of the above values.

[0077] Optionally, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the density of the positive electrode active layer is 3.5 g / cm³. 3 ~3.8g / cm3 .

[0078] Optionally, the positive electrode active material includes lithium phosphate, and the density of the positive electrode active layer is 2 g / cm³. 3 ~3g / cm 3 .

[0079] In some implementations, by selecting a suitable areal density of the positive electrode active layer, the battery cell can achieve an energy density of 250Wh / kg to 400Wh / kg. For example, the energy density of the battery cell can be 250Wh / kg, 260Wh / kg, 270Wh / kg, 280Wh / kg, 290Wh / kg, 300Wh / kg, 310Wh / kg, 320Wh / kg, 330Wh / kg, 340Wh / kg, 350Wh / kg, 360Wh / kg, 370Wh / kg, 380Wh / kg, 390Wh / kg, 400Wh / kg, etc. Optionally, the energy density of the battery cell is 270Wh / kg to 350Wh / kg.

[0080] In some embodiments, the positive electrode current collector includes a first support layer and a first metal layer, the first metal layer being located on at least one surface of the first support layer and between the first support layer and the positive electrode active layer. The positive electrode current collector adopts a composite current collector form, which can reduce the weight of the positive electrode current collector compared to a pure metal current collector, thus facilitating further improvement in the energy density of the battery cell. Optionally, the material of the first support layer includes at least one selected from polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), polyethylene, polypropylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polyoxymethylene, epoxy resin, phenolic resin, silicone rubber, and polycarbonate. Optionally, the material of the first metal layer includes at least one selected from aluminum and aluminum alloys.

[0081] In some embodiments, the thickness of the first metal layer is 200 nm to 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 of any two of the above values.

[0082] In some embodiments, the positive electrode current collector further includes a first adhesive layer located between the first support layer and the first metal layer. The first adhesive layer can improve the bonding force between the first metal layer and the first support layer, reduce the risk of the first metal layer detaching, and help maintain better structural stability of the positive electrode current collector, further improving the cycle performance of the battery cell. Optionally, the material of the first adhesive layer includes 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-butene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer, silicone rubber, phenolic resin, urea-formaldehyde resin, and polyimide.

[0083] In some embodiments, the negative electrode sheet includes a negative current collector and a negative active layer located on at least one surface of the negative current collector. 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 gel electrolyte distribution on the surface of the particles of the negative active material can protect the particles of the active material, reduce side reactions between the negative active material particles and the electrolyte, and further improve the cycle performance of the battery cell.

[0084] The gel electrolyte is distributed on the surface of the negative electrode active material particles, meaning the gel electrolyte is located on the surface of the negative electrode active layer away from the negative electrode current collector. For example, a film layer including the negative electrode active material is formed on the surface of the negative electrode current collector, and the gel electrolyte is located on the surface of the film layer away from the negative electrode current collector. Optionally, the preparation of this type of negative electrode sheet includes the following steps: coating a negative electrode slurry including the negative electrode active material onto the surface of the negative electrode current collector, drying and curing to obtain a film layer, and then placing a hydrophilic polymer on the surface of the film layer. When the hydrophilic polymer comes into contact with the electrolyte, the hydrophilic polymer adsorbs the electrolyte to form a gel electrolyte. This results in a structure where the gel electrolyte is distributed on the surface of the negative electrode active material particles. It is understood that the negative electrode slurry may also include binders and conductive agents, etc.

[0085] In some embodiments, the gel electrolyte is distributed in the pores between the particles of the negative electrode active material. This allows for greater confinement of the electrolyte within the negative electrode, further improving the cycle performance of the battery cell. Optionally, the preparation of this type of negative electrode includes the following steps: mixing a hydrophilic polymer and the negative electrode active material in a solvent to obtain a negative electrode slurry; then coating the negative electrode slurry onto the surface of a negative electrode current collector; and finally drying and curing to obtain a film layer. When the film layer comes into contact with the electrolyte, the hydrophilic polymer adsorbs the electrolyte to form a gel electrolyte. This results in a structure where the gel electrolyte is distributed in the pores between the particles of the negative electrode active material. It is understood that the negative electrode slurry may also include binders and conductive agents.

[0086] In some embodiments, the hydrophilic polymer constitutes 1% to 5% of the mass percentage of the negative electrode active layer. This range allows for a suitable retention of the limiting electrolyte within the negative electrode active layer, resulting in better compatibility between the limiting electrolyte and the negative electrode active material, and further improving the cycle performance of the battery cell. Optionally, the mass percentage of the hydrophilic polymer in the negative electrode active layer can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any value within the range of any two of the above values. More preferably, the hydrophilic polymer constitutes 2% to 4% of the mass percentage of the negative electrode active layer.

[0087] In some embodiments, the density of the negative electrode active layer is 1 g / cm³. 3 ~2g / cm 3 Optionally, the density of the negative electrode active layer can be 1 g / cm³. 3 1.1g / cm 3 1.2g / cm 3 1.3g / cm 3 1.4g / cm 3 1.5g / cm 3 1.6g / cm 3 1.7g / cm 3 1.8g / cm 3 1.9g / cm 3 2g / cm 3 Or any value within the range formed by any two of the above values. Further optionally, the density of the negative electrode active layer is 1.3 g / cm³. 3 ~1.7g / cm 3 Alternatively, the negative electrode active material may include graphite.

[0088] In some embodiments, the negative electrode current collector includes a second support layer and a second metal layer, the second metal layer being located on at least one surface of the second support layer and between the second support layer and the negative electrode active layer. The negative electrode current collector adopts a composite current collector form, which can reduce the weight of the negative electrode current collector compared to a pure metal current collector, thus facilitating further improvement in the energy density of the battery cell. Optionally, the material of the second support layer includes at least one selected from polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), polyethylene, polypropylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polyoxymethylene, epoxy resin, phenolic resin, silicone rubber, and polycarbonate.

[0089] In some embodiments, the thickness of the second metal layer is 200 nm to 2000 nm. Optionally, the thickness of the second 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 of any two of the above values.

[0090] In some embodiments, the negative electrode current collector further includes a second adhesive layer located 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 detaching, and help maintain better structural stability of the positive electrode current collector, further improving the cycle performance of the battery cell. Optionally, the material of the second adhesive layer includes at least one of polyolefins, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, polyurethanes, epoxy resins, styrene-isoprene-styrene copolymers, styrene-butadiene-styrene copolymers, styrene-ethylene-butene-styrene copolymers, styrene-ethylene-propylene-styrene copolymers, silicone rubber, phenolic resins, urea-formaldehyde resins, and polyimides. Optionally, the material of the second metal layer includes at least one of copper and copper alloys.

[0091] In some embodiments, the gel electrolyte is distributed in the pores of the separator. This allows more electrolyte to be confined within the separator, promoting the transport of active ions and further improving the cycle performance of the battery cell.

[0092] In some embodiments, the separator includes a separator substrate and a coating on at least one surface of the separator substrate, the coating containing particulate filler. Optionally, the particulate filler includes one or more of boehmite, alumina, silica, and magnesium hydroxide. The coating containing particulate filler has good heat resistance and high strength, which can improve the heat resistance and strength of the separator, enabling the separator to maintain a relatively stable structure during battery cell cycling and further promoting the improvement of battery cell cycle performance. Optionally, the coating thickness is 0.25 μm to 5 μm. For example, the coating thickness 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 the range of any two of the above values.

[0093] In some embodiments, the coating includes a solid electrolyte. The solid electrolyte may optionally be lithium aluminum titanium phosphate. Optionally, a coating is provided between the positive electrode and the separator substrate.

[0094] 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.

[0095] 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 3μm to 20μm. For example, the thickness of the separator substrate can be 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, or any value within the range of any two of the above values. More optionally, the thickness of the separator substrate is 5μm to 16μm.

[0096] In some embodiments, the limiting electrolyte comprises a solvent and an electrolyte salt. Optionally, the solvent comprises at least one of cyclic carbonates, chain carbonates, carboxylic acid esters, fluorocarbonates, and sulfites. Cyclic carbonates comprise one or more of ethylene carbonate (EC) and propylene carbonate (PC). Chain carbonates comprise one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC).

[0097] Electrolyte salts include lithium salts. Lithium salts include at least one of LiPF6, LiBF4, LiBOB, LiFSI, LiTFSI, Li2DFB, and LiODFB.

[0098] 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.

[0099] In some implementations...

[0100] 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 comprise one or more of ethylene carbonate (EC) and propylene carbonate (PC). Chain carbonates comprise one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC).

[0101] Electrolyte salts include lithium salts. Lithium salts include at least one of LiPF6, LiBF4, LiBOB, LiFSI, LiTFSI, Li2DFB, and LiODFB.

[0102] Optionally, the limiting electrolyte and the free electrolyte are the same.

[0103] In some embodiments, the mass percentage of ethylene carbonate in the solvent of the free electrolyte is 0.

[0104] In some embodiments, the hydrophilic polymer includes one or more of fluorinated polymers, ether polymers, ester polymers, and aldehyde-ketone polymers.

[0105] Fluoropolymers

[0106] In some embodiments, the hydrophilic polymer includes a fluorinated polymer; the crystallinity of the fluorinated polymer, as determined by differential scanning calorimetry, is X. c1 15%≤X c1 ≤25%; the melting temperature of the fluoropolymer is T m1 Its unit is ℃, 120≤T m1 ≤140.

[0107] The cold crystallinity of fluorinated polymers, measured by differential scanning calorimetry, is X. c2 10% < X c2 ≤25%; the cold crystallization temperature of fluorinated polymers is Tc2, which is in °C, 35≤Tc2. c2 ≤65.

[0108] Crystallization refers to the process by which atoms, ions, or molecules in a material arrange themselves in a specific spatial order to form an ordered structure. The conformation of polymers during crystallization is determined by both intramolecular and intermolecular factors. Intermolecular forces affect the packing density between molecular chains. Crystallinity X c1 The degree of crystallinity in a material is characterized by differential scanning calorimetry (DSC). Specifically, the testing procedure is as follows: Take 0.5g~0.8g of sample, place the sample in a crucible, and subject the sample to heating and cooling at a nitrogen atmosphere, with a heating rate of 10℃ / min from the intrinsic temperature of the material (T0). g1 The initial temperature was 20°C lower than the material's intrinsic temperature, and the temperature was increased to the material's intrinsic temperature. m1 The cutoff temperature for the 20°C increase is determined by the actual glass transition temperature T of the material, based on the peak values ​​of heat absorption and release or the transition point during the process. g1 and melting temperature T m1 wait.

[0109] Therefore, fluorinated polymers have relatively low crystallinity and melting temperature, resulting in a looser molecular chain arrangement, weaker intermolecular forces, and easier opening of adjacent molecular chains. Chain segment movement is achieved through intermolecular rotation, forming a highly flexible molecular chain structure. Furthermore, fluorinated polymers and the electrolyte in the battery cell can form a gel electrolyte, further improving the cycle performance of the battery cell.

[0110] For example, the crystallinity X of the fluorinated polymer was measured by differential scanning calorimetry. c1 It can be 20%, 21%, 22%, 23%, 24%, 25%, or any value within the range of any two of the above values.

[0111] For example, the melting temperature T of the fluoropolymer m1 It can be 20℃, 50℃, 70℃, 90℃, 100℃, 120℃, 140℃, or any value within the range of any two of the above values.

[0112] For example, the cold crystallinity X of fluorinated polymers measured by differential scanning calorimetry c2 It can be 10%, 12%, 15%, 18%, 20%, 22%, 25%, or any value within the range of any two of the above values.

[0113] For example, the cold crystallization temperature Tc2 of the fluoropolymer can be 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, or any value within the range of any two of the above values.

[0114] In some embodiments, the glass transition temperature of the fluorinated polymer is T. g1 Its unit is ℃, -150≤T g1 ≤60.

[0115] The glass transition temperature (GLT) is the temperature at which polymer chain segments transition from frozen to mobile. The GLT has a certain influence on the flexibility of polymer molecular chains; the lower the GLT, the better the flexibility of the polymer molecular chains at room temperature, and vice versa. The GLT can be measured using differential scanning calorimetry (DSC). Polymers with relatively low GLTs exhibit better chain segment flexibility, making it easier for adjacent molecular chains to open. For example, the GLT of fluorinated polymers can be -150℃, -120℃, -100℃, -80℃, -60℃, -30℃, 0℃, 30℃, 60℃, or any value within the range of any two of these values.

[0116] In some embodiments, the monomers of the fluorinated polymer include hexafluoropropylene and vinylidene fluoride. The design of using both hexafluoropropylene and vinylidene fluoride monomers allows the fluorinated polymer to have low crystallinity, which facilitates the diffusion and wetting of the electrolyte within the fluorinated polymer, improves the affinity of the fluorinated polymer for the electrolyte, and enhances the liquid retention capacity of the gel electrolyte. Optionally, the molar percentage of hexafluoropropylene, based on the total molar ratio of hexafluoropropylene and vinylidene fluoride, is 6% to 13%. This molar percentage range allows the fluorinated polymer to have a stable structure, maintaining good affinity for the electrolyte while reducing the risk of the fluorinated polymer dissolving in the electrolyte, further promoting electrolyte retention within the fluorinated polymer, reducing the risk of the confined electrolyte in the gel electrolyte becoming free electrolyte, and further reducing the risk of leakage from the battery cell. Optionally, the molar percentage of hexafluoropropylene, based on the total molar ratio of hexafluoropropylene and vinylidene fluoride, can be 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, or any value within the range of any two of the above values.

[0117] In some embodiments, the fluoropolymer includes at least one of the structural units represented by formula (A1) to formula (AIII).

[0118] Formula (AI) Formula (AII),

[0119] In equations (AI) and (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 them contains a fluorine atom; when substituted, the substituents include one or more of the following: nitrile (-CN), nitro, sulfonic acid, sulfonyl, amide, carboxyl, ester, and halogen atom;

[0120] Formula (AIII);

[0121] In equation (AIII), R 15 Includes single bonds, substituted or unsubstituted C1-C3 alkyl groups; when substituted, the substituents include one or more of nitrile (-CN), nitro, sulfonic acid, sulfonyl, amide, carboxyl, ester, and halogen atoms; p is selected from positive integers from 1 to 3; n is selected from positive integers from 1000 to 30000.

[0122] In some implementations, 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-C2 alkyl group, or a substituted or unsubstituted C1-C2 alkoxy group; further optionally, R 11 R 12 R 13 and R 14 Each of these atoms independently includes a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, a fluoromethyl group, a methoxy group, or a perfluoromethoxy group.

[0123] In some embodiments, the fluoropolymer includes at least one of the structural units shown in formula (AI-1) to formula (AI-11).

[0124]

[0125]

[0126] In some embodiments, the fluoropolymer includes at least one of the structural units shown in formula (AII-1) to formula (AII-5).

[0127]

[0128] In some embodiments, the fluoropolymer includes at least one of the structural units shown in formula (AIII-1) to formula (AIII-3).

[0129]

[0130] For example, fluorinated polymers include one or more of the following: perfluoroethylene PTFE, polyvinylidene fluoride PVDF, perfluoroethylene propylene copolymer FEP, perfluoroalkoxy polymer PFA, perfluoropolyether PFPE, polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP, polyvinylidene fluoride-trifluoroethylene copolymer PVDF-TrFE, and perfluoro(1-butenyl vinyl ether) polymer (CYTOP).

[0131] Optionally, the fluorinated polymer includes one or more of the following: perfluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoroethylene propylene copolymer (FEP), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), and polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE).

[0132] The aforementioned fluorinated polymers can be derived from one or more of the following monomers: fluorinated cyclohexane, fluorinated vinylidene, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropylene, trifluoropropylene, tetrafluoropropylene, and pentafluoropropylene. Optionally, the aforementioned fluorinated polymers can be derived from at least two of the following monomers: fluorinated cyclohexane, fluorinated vinylidene, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropylene, trifluoropropylene, tetrafluoropropylene, and pentafluoropropylene.

[0133] The monomers used in the above-mentioned fluorinated polymers are all short-chain monomers, which are conducive to the polymerization to form straight-chain linear structures or short-branched structures. This type of structure has a low degree of entanglement, which is conducive to improving the flexibility of the molecular chain. The molecular chain can fully extend in the electrolyte, thereby further improving the interfacial properties of the active material.

[0134] In some embodiments, n is selected from positive integers from 5000 to 20000; and / or the molecular weight of the hydrophilic polymer is 2 × 10⁻⁶. 5 g / mol up to 1.5 × 10 6 When the molecular weight of the polymer is within the above range, it ensures that the polymer exhibits a certain degree of solubility in the electrolyte, while being less likely to be completely dissolved and dispersed by the electrolyte. This is beneficial for controlling the distribution and dispersion of the polymer on the surface of the active material. Furthermore, it can further improve the flexibility between the polymer molecular chains, and the relatively weak interaction forces between the molecular chains facilitate the solvent molecules in the electrolyte to open the molecular chains and enter between the molecular chains, where they are encapsulated. This, in turn, facilitates the smooth and rapid migration of active ions into the active material through the solvent.

[0135] For example, the molecular weight of the polymer can be 2 × 10⁻⁶. 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.

[0136] [Ether Polymers]

[0137] Lyophilic polymers include ether polymers, wherein the ether polymers are formed into sheet-like structures; the sheet-like structures are in (T m2 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 K1, 1<K1<∞, T m2 °C indicates the melting temperature of ether polymers.

[0138] Specifically, the preparation process of the sheet-like structure is as follows: The ether polymer is vacuum dried at 80°C for 12 hours. The dried ether polymer is then hot-pressed into thin sheets using a flat vulcanizing machine, with the hot-pressing temperature set to (T...). m2 The temperature is +20℃, the calendering thickness is 1mm~2mm, the calendering time is 2min, and the pressure is 8MPa. After calendering for 2min, the sample is taken out and placed on another vulcanizing machine of the same model for cold pressing at a pressure of 10MPa. Polymer discs (sheet-like structures) of a fixed size can be obtained using a circular mold with a diameter of 25mm. For example, the sheet-like structure can be a disc with a thickness of 1mm~2mm and a diameter of 25mm; it can also be prepared according to the sample standard required by the testing equipment.

[0139] According to the conclusions of classical linear viscoelasticity, for polymers, especially linear polymers, the elastic modulus G'-energy dissipation modulus G" in the terminal region (the range approaching the maximum angular velocity) follows a frequency dependence, and the longest chain of the polymer plays a role in the viscoelastic behavior.

[0140] The specific steps of the dynamic frequency scanning test are as follows: A TA-AR2000EX rotational rheometer is used for the dynamic frequency scanning test. The parallel plate has a diameter of 25mm and a thickness of 0.9mm. To ensure the test is conducted within the linear springback region, the strain is set at 2% during the dynamic frequency scanning test, and the test temperature is (T...). m2 +20)℃, the frequency scan range for testing is: 500rad / s≤w2≤0.05rad / s, in order to obtain data in the lowest possible frequency range.

[0141] Dynamic frequency scanning tests can characterize the degree of molecular chain entanglement under solid-state melting (molten state). Compared with linear or short-branched structures, long-branched structures, network structures, and low-crosslinking structures have a high degree of entanglement and exhibit deviate from linear end-effector behavior. Ether polymers exhibit solid-state behavior. When the ether polymers of this application meet the above-mentioned range, the molecular chain entanglement state can be further reduced, which is beneficial to the diffusion of solvent molecules in the electrolyte between molecular chains. Furthermore, the ether polymers still maintain a certain degree of molecular chain entanglement, enabling them to form a gel electrolyte with the electrolyte, further improving the cycle performance of the battery cell.

[0142] In some implementations, 1 < K1 ≤ 100; alternatively, 1 < K1 ≤ 10. For example, K1 can be 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.

[0143] In some embodiments, the glass transition temperature of the ether polymer is T.g2 Its unit is ℃, -100≤T g2 ≤50; optionally, -80≤T g2 ≤30. For example, the glass transition temperature T of ether polymers. g2 It can be -100℃, -80℃, -60℃, -30℃, 0℃, 30℃, 50℃, or any value within the range of any two of the above values.

[0144] In some embodiments, the ether polymer comprises the structural unit shown in formula (BI).

[0145] Formula (BI);

[0146] In formula (BI), R 21 and R 22 Each independently comprises a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; R 23 Includes substituted or unsubstituted C1-C5 alkylene groups. Optionally, R 21 and R 22 Each independently comprises a hydrogen atom, a substituted or unsubstituted C1-C2 alkyl group; and / or R 23 This includes single-bonded, substituted, or unsubstituted C1-C4 methylene groups.

[0147] In some embodiments, when substituted, the substituent may include one or more of the following: nitrile (-CN), nitro, sulfonic acid, sulfonyl, amide, carboxyl, ester, and halogen atom.

[0148] For example, the ether polymer includes at least one of the structural units shown in formula (BI-1) to formula (BI-8).

[0149]

[0150]

[0151] In some embodiments, the ether polymer comprises the structural unit represented by formula (BII).

[0152] Formula (BII);

[0153] In formula (BII), R 24 To R 27 Each independently comprises 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 them contains a substituted or unsubstituted C1-C3 alkoxy or ether group.

[0154] Optionally, R 24 To R 27 Each independently comprises 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 them contains a substituted or unsubstituted C1-C2 alkoxy or ether group.

[0155] In some embodiments, the ether polymer includes at least one of the structural units shown in formula (BII-1) to formula (BII-7).

[0156]

[0157] The monomers used in the above-mentioned ether polymers are polycyclic rings, such as six-membered rings or shorter-chain monomers, which are conducive to the polymerization to form a high content of -O- structures. This type of structure has a low degree of entanglement, which is beneficial to improving the flexibility of the molecular chain. The molecular chain can fully extend in the electrolyte and easily form a gel with the electrolyte, further improving the cycle performance and storage performance of the battery cell.

[0158] The polymers described above are merely examples of structural groups in the main molecular chains. In the embodiments of this application, the polymers may also be obtained by copolymerizing the above structural groups with other types of structural groups (such as olefin structural units, acrylonitrile structural units, etc.).

[0159] When the above groups are substituted, the substituents may include one or more of the following: nitrile (-CN), nitro, sulfonic acid, sulfonyl, amide, carboxyl, ester, and halogen atom. These substituents are high-pressure resistant and are more conducive to stabilizing the polymer structure. Halogen atoms may include fluorine, chlorine, bromine, etc.

[0160] In some implementations, n is selected from a positive integer from 1500 to 25000.

[0161] Optionally, n is selected from a positive integer between 3000 and 18000.

[0162] In some embodiments, the polymer has a molecular weight of 1.2 × 10⁻⁶. 5 g / mol to 1.0 × 10 6 g / mol.

[0163] For example, the molecular weight of the polymer can be 1.2 × 10⁻⁶. 5 g / mol, 2×10 5 g / mol, 5×10 5 g / mol, 8×10 5g / mol, 1×10 6 g / mol or any value within the range consisting of any two of the above values.

[0164] Ester polymers

[0165] In some embodiments, the hydrophilic polymer includes an ester polymer, wherein the ester polymer is formed into a sheet-like structure; the sheet-like structure is in (T m3 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 K2, 1<K2<∞, T m3 °C represents the melting temperature of ester polymers.

[0166] When the ester polymers of this application meet the above-mentioned range, they can further reduce the molecular chain entanglement state, which is beneficial to the diffusion of solvent molecules in the electrolyte between molecular chains; and the ether polymers still maintain 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 cell.

[0167] In some implementations, 1 < K2 ≤ 100; further alternatively, 1 < K2 ≤ 10.

[0168] For example, K2 can 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 the range of any two of the above values.

[0169] In some embodiments, the glass transition temperature of the ester polymer is T. g3 Its unit is ℃, -100≤T g3 ≤50; optionally, -80≤T g3 ≤30.

[0170] For example, the glass transition temperature of the ester 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.

[0171] In some embodiments, the ester polymer comprises the structural unit shown in formula (CI).

[0172] Formula (CI);

[0173] In formula (CI), R 31 R 32 and R 33Each independently comprises a hydrogen atom, or a substituted or unsubstituted C1-C8 alkyl group; R 34 Includes substituted or unsubstituted C1-C8 alkyl groups, or substituted or unsubstituted C1-C8 hydroxyalkyl groups; optionally, R 34 This includes substituted or unsubstituted C1-C6 alkyl groups, or substituted or unsubstituted C1-C6 hydroxyalkyl groups.

[0174] Optionally, R 31 Includes hydrogen atoms, or substituted or unsubstituted methyl groups; R 32 and R 33 Each independently comprises a hydrogen atom; R 34 This includes substituted or unsubstituted C1-C4 alkyl groups, or substituted or unsubstituted C1-C4 hydroxyalkyl groups.

[0175] For example, the ester polymer includes at least one of the structural units shown in formula (CI-1) to formula (CI-15).

[0176]

[0177]

[0178] In some embodiments, the ester polymer comprises the structural unit shown in formula (CII).

[0179] Formula (CII);

[0180] In formula (CII), R 35 Includes substituted or unsubstituted C2-C6 methylene groups; optionally, R 35 Each independently includes substituted or unsubstituted C2-C4 methylene groups.

[0181] For example, the ester polymer includes at least one of the structural units shown in formula (CII-1) to formula (CII-5).

[0182]

[0183] The aforementioned ester polymers have a low degree of molecular chain entanglement, which is beneficial to improving the flexibility of the molecular chains. The molecular chains can fully extend in the electrolyte and easily form a gel electrolyte with the electrolyte.

[0184] The polymers described above are merely examples of structural groups in the main molecular chains. In the embodiments of this application, the polymers may also be obtained by copolymerizing the above structural groups with other types of structural groups (such as olefin structural units, acrylonitrile structural units, maleic anhydride and other monomers with functional groups).

[0185] When the above groups are substituted, the substituents may include one or more of the following: nitrile, nitro, sulfonyl, carboxyl, ester, chlorine, fluorine, and bromine. These substituents are high-pressure resistant and are more conducive to stabilizing the polymer structure.

[0186] In some implementations, n is selected from a positive integer from 800 to 20000.

[0187] Optionally, n is selected from a positive integer between 1000 and 15000.

[0188] In some embodiments, the polymer has a molecular weight of 1.2 × 10⁻⁶. 5 g / mol to 1.0 × 10 6 g / mol.

[0189] For example, the molecular weight of the polymer can be 1.2 × 10⁻⁶. 5 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.

[0190] Aldehyde-ketone polymers

[0191] 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.

[0192] In some implementations, 0.8 ≤ K3 ≤ 100; alternatively, 0.8 ≤ K3 ≤ 10.

[0193] 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.

[0194] 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.

[0195] 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.

[0196] In some embodiments, the aldehyde-ketone polymer comprises structural units represented by formula (DI) and / or formula (DII).

[0197] Formula (DI);

[0198] 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.

[0199] Optionally, R 41 This includes single-bonded, substituted, or unsubstituted C1-C2 methylene groups.

[0200] Optionally, R 42 Includes hydrogen atoms, substituted or unsubstituted C1-C3 alkyl groups.

[0201] In the embodiments of this application, a single bond indicates that the group does not exist, and the atoms on both sides of the group are connected by a single bond, such as R. 41 A single bond, representing R 41 The carbon atoms on both sides are connected by single bonds.

[0202] For example, the aldehyde-ketone polymer includes at least one of the structural units shown in formula (DI-1) to formula (DI-6).

[0203]

[0204] In some embodiments, the aldehyde-ketone polymer comprises the structural unit shown in formula (DII).

[0205] Formula (DII);

[0206] 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 integers from 0 to 5, and at least one of r and s is selected from a positive integer. Optionally, R 43 To R 46Each of these components independently includes a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C2 hydroxyalkyl group, or a substituted or unsubstituted C1-C2 alkoxy group.

[0207] In some embodiments, the aldehyde-ketone polymer includes at least one of the structural units shown in formula (DII-1) to formula (DII-4).

[0208]

[0209]

[0210] The molecular chains of the aforementioned aldehyde-ketone polymers have a low degree of entanglement, which is beneficial to improving the flexibility of the molecular chains. The molecular chains can fully extend in the electrolyte, which is conducive to forming a gel electrolyte with the electrolyte.

[0211] The polymers described above are merely examples of structural groups in the main molecular chains. In the embodiments of this application, the polymers may also be obtained by copolymerizing the above structural groups with other types of structural groups (such as olefin structural units, enol structural units, acrylonitrile structural units, etc.).

[0212] When the above groups are substituted, the substituents may include one or more of the following: nitrile (-CN), nitro, sulfonyl, carboxyl, ester, chlorine, fluorine, and bromine. These substituents are high-pressure resistant and are more conducive to stabilizing the polymer structure.

[0213] In some implementations, n is selected from a positive integer from 500 to 15000.

[0214] Optionally, n is selected from positive integers from 500 to 10000.

[0215] In some embodiments, the molecular weight of the hydrophilic polymer is 1.2 × 10⁻⁶. 5 g / mol to 1×10 6 g / mol.

[0216] For example, the molecular weight of the hydrophilic polymer can be about 1.2 × 10⁻⁶. 5 g / mol, approximately 2 × 10 5 g / mol, approximately 5 × 10 5 g / mol, approximately 8 × 10 5 g / mol, approximately 1×10 6 g / mol or any value within the range consisting of any two of the above values.

[0217] The embodiments of this application can further improve the cycle performance of battery cells when the hydrophilic polymer also meets one or more of the following conditions.

[0218] In some embodiments, the hydrophilic polymer is added to a first solvent at 70°C to form a polymer system. After standing at 70°C for 8 hours and then at 25°C for ≥24 hours, undergoing these two stages of standing treatment, the hydrophilic polymer system partially swells and adsorbs, transforming into a gel state. The polymer system is then filtered through a 200-mesh filter, leaving the first substance. The mass of the hydrophilic polymer is n (in grams); the mass of the first substance is m (in grams); the polymer and the first substance satisfy: 5 ≤ m / n ≤ 1000; optionally, 10 ≤ m / n ≤ 1000; further optionally, 10 ≤ m / n ≤ 50. Exemplarily, m / n can be 5, 10, 20, 25, 28, 30, 32, 35, 40, 50, 80, 100, 200, 500, 1000, or any value within the range of any two of the above values.

[0219] For example, based on the mass of the polymer system, the ratio of the mass content of the lyophilic polymer to the mass content of the first solvent ranges from 1:100 to 1:10, for example, 3:50.

[0220] For example, the first solvent is the same as or similar to the solvent of the electrolyte, and the first solvent may include carbonate solvents. For example, carbonate solvents include cyclic carbonate solvents and / or linear carbonate solvents.

[0221] Examples of cyclic carbonate solvents include one or more of ethylene carbonate EC, vinylene carbonate VC, fluoroethylene carbonate FEC, difluoroethylene carbonate DFEC, vinyl ethylene carbonate VEC, and dioctyl carbonate CC.

[0222] As examples of linear carbonate solvents, linear carbonate solvents include one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), diphenyl carbonate (DPC), methyl allyl carbonate (MAC), and polycarbonate (VA).

[0223] Optionally, the first solvent may also contain lithium salt and electrolyte additives, such as lithium hexafluorophosphate, vinylene carbonate (VC), fluorovinylene carbonate (FEC), etc.

[0224] In this application, m / n is also referred to as precipitation value, which characterizes the ability of lyophilic polymers and solvents to transform into a gel-state substance.

[0225] The first substance mainly includes gel-state substances formed by lyophilic polymers and a first solvent. In this type of gel-state substance, the molecular structure of the polymer remains basically unchanged.

[0226] In some embodiments, the first substance is dried at 80°C for 12 hours to remove the first solvent from the first substance, and then detected by infrared spectrophotometry (IR) or nuclear magnetic resonance (NMR). After drying, the main component of the first substance is the hydrophilic polymer mentioned above.

[0227] In this application, the hydrophilic polymer in the battery cell can be obtained by the following method: First, discharge the battery cell to 0% SOC, and then separate the positive electrode, negative electrode, and separator. Taking the negative electrode as an example: Take a negative electrode with a mass of m1, rinse it with a small amount of water to obtain negative electrode powder, dry it at 80℃ for 4 hours, add sufficient DMC solvent, stir thoroughly to ensure full contact between the powder and the solvent, soak it at 60℃ for 24 hours, and then remove the solvent by rotary evaporation of the supernatant to obtain a polymer film. The hydrophilic polymer is obtained through washing, separation, and other operations. The hydrophilic polymer in the positive electrode and separator can be obtained by a similar method.

[0228] The relevant parameters of the hydrophilic polymer in the embodiments of this application can be detected by the following method: the functional groups of the hydrophilic polymer in the embodiments of this application can be detected by infrared spectrophotometry (IR). Specifically, the hydrophilic polymer is tested using a Thermo Nicolet Nexus 670 attenuated total reflectance Fourier transform infrared spectrometer (FTIR-ATR), and then tested according to standard GB / T6040-2002. The test range is: ATR method 600 cm⁻¹. -1 ~4000cm -1 Repeatability: ±2cm -1 Resolution: Better than 4cm -1 Transmission depth: 0.2μm~0.6μm.

[0229] The structure of the lyophilic polymer in the embodiments of this application can be determined by nuclear magnetic resonance (NMR). Specifically, 1H NMR and 13C NMR are performed on a Varian Mercury Plus-400 NMR spectrometer at a test temperature of 20°C, with TMS as an internal standard, CDCl3 as a solvent, and a proton resonance frequency of 400MHz.

[0230] The polymer monomer type of the lyophilic polymer described in this application (especially suitable for monomers with a small proportion in the polymer) can be determined using pyrolysis-gas chromatography-mass spectrometry (GC-MS). The specific testing steps are as follows: Accurately weigh 0.5 mg of sample into a sample cup, fix it to the injection rod, and then place it into the pyrolyzer installed near the GC (gas chromatograph) injection port. After the pyrolyzer reaches the set temperature, press the injection button. The sample cup will rapidly fall into the core of the pyrolysis furnace through free fall. In an inert N2 atmosphere, the volatile components will instantly vaporize and be carried into the gas chromatography column by the carrier gas for separation. Finally, the components will be detected by flame ionization detector (FID) or mass spectrometer (MS) to obtain a gas chromatogram or total ion chromatogram.

[0231] The molecular weight of the hydrophilic polymer in the embodiments of this application has a meaning known in the art and can be determined using commonly used equipment and methods in the art, such as gel permeation chromatography (GPC). The specific testing steps are as follows: Take an appropriate amount of the sample to be tested (the sample concentration should be 8%-12% opacity), add 20 ml of deionized water, and simultaneously incubate for 5 minutes (53 kHz / 120 W) to ensure complete dispersion of the sample. Then, determine the sample according to GB / T19077-2016 / ISO13320:2009 standard.

[0232] Alternatively, a multi-angle laser scattering instrument (MALLS) can be used for testing. Specifically, a GPC coupled with a Dawn Heleos II multi-angle laser light scattering device, an Optilab T-rEX refractive index (RI) detector, and a Visco Star II viscometer is employed. Tests are conducted at 30°C using tetrahydrofuran as the mobile phase at a flow rate of 1.0 ml / min. SEC-SAMLL data are processed using the commercial software ASTRA6 to obtain molecular weight parameters.

[0233] In some embodiments, the lithium-ion transference number of the gel electrolyte is ≥0.4. A larger lithium-ion transference number in the gel electrolyte promotes lithium-ion movement and facilitates lithium-ion insertion and extraction, which is beneficial for 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.

[0234] The lithium-ion transport number can be measured using the constant potential polarization method. Specifically, a Li / electrolyte / Li symmetrical battery structure is assembled. A small and constant potential difference ΔV (typically around 10 mV) is applied to the symmetrical battery, and the current change over time is recorded. The formula for calculating the lithium-ion transport number is: , where t +δV is the lithium-ion transport number, δV is the applied potential difference, I0 is the initial current, R0 is the interfacial impedance between the electrode and the electrolyte before polarization, and I ss For steady-state current, R ss This represents the interfacial impedance between the electrode and the electrolyte after polarization.

[0235] Another embodiment of this application provides a battery. The battery includes a single battery cell.

[0236] Another embodiment of this application provides an electrical device that includes a battery.

[0237] The following description, with appropriate reference to the accompanying drawings, describes the battery cell, battery, and power device of this application.

[0238]

Positive Electrode

[0239] The positive electrode includes a positive current collector and a positive active layer disposed on at least one surface of the positive current collector, the positive active layer including a positive active material.

[0240] As a non-limiting example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0241] In some embodiments, in addition to the lithium nickel manganese cobalt oxides described above, the positive electrode active material may also include positive electrode active materials for batteries known in the art. As a non-limiting example, positive electrode active materials for batteries known in the art include, but are not limited to, one or more of lithium phosphates, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt aluminum oxides, and their modified compounds. Non-limiting examples of lithium phosphates may include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt aluminum oxides may include LiNi 0.8 Co 0.15 Al 0.05 O2.

[0242] In some embodiments, the positive electrode active layer may optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0243] In some embodiments, the positive electrode active layer may optionally include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0244] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry onto at least one surface of the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing, and other processes. The solvent can be selected from, but is not limited to, any of the solvents described in the foregoing embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface or both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40% by weight (wt%) to 80 wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 mPa·s to 25000 mPa·s.

[0245] [Negative electrode plate]

[0246] 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.

[0247] As a non-limiting example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0248] In some embodiments, the negative electrode active material may also include negative electrode active materials known in the art for use in batteries. As a non-limiting example, the negative electrode active material may include one or more of the following materials: carbon-based materials other than graphite, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0249] In some embodiments, the negative electrode active layer may optionally include a binder. The binder may 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).

[0250] In some embodiments, the negative electrode active layer may optionally include a conductive agent. The conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0251] In some embodiments, the negative electrode active layer may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0252] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (a non-limiting example of a solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto at least one surface of a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing, and other processes. The surface of the negative electrode current collector coated with the negative electrode slurry 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 40wt% to 60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000 mPa·s to 10000 mPa·s.

[0253] Electrolytes

[0254] Electrolytes function to conduct ions between the positive and negative electrodes. Electrolytes can be liquid, gel-like, or entirely solid.

[0255] In some embodiments, the limiting electrolyte and free electrolyte of this application include electrolyte salts and solvents.

[0256] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0257] In some embodiments, the solvent may include 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), butene carbonate ( One or more of the following: 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.

[0258] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0259] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), etc.

[0260]

Isolation Film

[0261] In some embodiments, the separator can be any known porous separator with good chemical and mechanical stability.

[0262] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0263] In some embodiments, the thickness of the separator is 6 micrometers (μm) to 40 μm, and optionally 12 μm to 20 μm.

[0264] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0265] In some embodiments, the casing of the battery cell can be a rigid casing, such as a hard plastic casing, an aluminum casing, a steel casing, etc. The casing of the battery cell can also be a pouch, such as a pouch-type pouch. The material of the pouch can be plastic; further, non-limiting examples of plastics may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0266] A battery includes at least one battery cell. A battery may include one or more battery cells.

[0267] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 Here is an example of a square-structured battery cell 1. Battery cell 1 includes a housing 11 with an opening, an end cap 13 for closing the opening, and electrode terminals 14 disposed on the end cap. The electrode terminals 14 are located at the bottom of the housing along the direction of gravity.

[0268] Reference Figure 2 The housing 11 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. An end cap 13 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 12 via a winding or stacking process. The electrode assembly 12 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 12. The number of electrode assemblies 12 contained in a single battery cell 1 can be one or more, which can be selected by those skilled in the art according to actual needs.

[0269] The battery can be a battery module or a battery pack.

[0270] A battery module includes at least one battery cell. The number of battery cells in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0271] In a battery module, multiple battery cells can be arranged sequentially along the length of the module. Of course, they can also be arranged in any other manner. Furthermore, these battery cells can be secured using fasteners.

[0272] Optionally, the battery module may also include a housing with a receiving space in which multiple battery cells are housed.

[0273] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the battery pack may contain one or more battery modules. Those skilled in the art can select an appropriate number based on the application and capacity of the battery pack.

[0274] The battery pack may include a battery box and multiple battery modules disposed within the battery box. The battery box includes an upper body and a lower body, with the upper body covering the lower body to form a closed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0275] In addition, this application also provides an electrical device, which includes the battery provided in this application. The battery can be used as a power source for the electrical device or as an energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Among them, mobile devices may be, for example, mobile phones, laptops, etc.; electric vehicles may be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to.

[0276] As an electrical device, the battery can be selected according to its usage requirements.

[0277] Figure 3 Here is an example of an electrical device 2. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this electrical device, a battery pack or battery module can be used.

[0278] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can be powered by a battery.

[0279] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0280] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0281] Example 1

[0282] (1) Preparation of positive electrode sheet

[0283] A positive electrode slurry was prepared by mixing positive electrode active material, conductive agent carbon black, and binder PVDF in a mass percentage ratio of 98.4%:0.4%:1.2% with N-methylpyrrolidone (NMP). The positive electrode slurry was coated onto a 12 μm thick aluminum foil, dried at 85°C, and then cold-pressed. After edge trimming, cutting, and slitting, the foil was dried under vacuum at 85°C for 4 hours to form the positive electrode sheet. The density of the positive electrode active layer in the positive electrode sheet was 3.5 g / cm³. 3 .

[0284] (2) Preparation of negative electrode sheet

[0285] A negative electrode slurry was prepared by mixing a hydrophilic polymer, graphite, conductive carbon black, styrene-butadiene rubber (SBR) as a binder, and sodium methyl cellulose (CMC-Na) as a thickener in deionized water at a mass percentage ratio of 3%:94%:0.5%:1.5%:1%. The negative electrode slurry was coated onto an 8 μm thick copper foil, dried at 85°C, and then cold-pressed. After edge trimming, cutting, and slitting, the foil was dried under vacuum at 120°C for 12 hours to form the negative electrode sheet. The density of the negative electrode active layer in the negative electrode sheet was 1.6 g / cm³. 3 In the negative electrode active layer, the hydrophilic polymer accounts for 3% of the mass percentage of the negative electrode active layer.

[0286] (3) Separating membrane

[0287] The substrate is made of polyethylene and has a boehmite coating with a thickness of 2 μm on its surface.

[0288] (4) Preparation of electrolyte

[0289] In an environment with a water content of less than 10 ppm, non-aqueous organic solvents ethylene carbonate (DMC) and ethyl methyl carbonate (EMC) are mixed at a mass ratio of 1:9 to obtain an electrolyte solvent. Then, lithium salt (LiPF6) is mixed with the mixed solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L. Finally, 1% wtVC and 3% wtFEC additives are added.

[0290] (5) Preparation of battery cells

[0291] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrode. The electrode assembly is then wound to obtain an electrode assembly. The electrode assembly is placed in an aluminum shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a battery cell is obtained.

[0292] Examples 2 to 14, Comparative Example 1

[0293] The differences between Examples 2-14 and Comparative Example 1 compared to Example 1 are shown in Table 1.

[0294] Comparative Example 2

[0295] Compared to Example 1, Comparative Example 1 differs in that the hydrophilic polymer in the positive electrode active layer is replaced with a positive electrode active material, and the hydrophilic polymer in the negative electrode active layer is replaced with a negative electrode active material. That is, the battery cell of Comparative Example 2 does not contain a hydrophilic polymer.

[0296] Test case

[0297] (1) The mass energy density of the battery cells in the examples and comparative examples was tested. The test method was as follows: the battery cell was charged at a constant current of 0.33C to 4.2V, and then charged at a constant voltage to the cutoff current of 0.05C; the battery cell was then discharged at a constant current of 0.33C to 2.8V, and the discharge energy (in Wh) was recorded. The mass of the battery cell was weighed (in kg), and the mass energy density of the battery cell was calculated from the discharge energy / mass, in Wh / kg.

[0298] (2) The cycle performance of the battery cells in the examples and comparative examples was tested. The test method was as follows: the capacity of the battery cells before cycling was tested; 0.33C charging to 10% SOC, 3C charging to 15% SOC, 2C charging to 20% SOC, 1.5C charging to 15% SOC, 1C charging to 20% SOC, then 0.33C constant current charging to 100% SOC, with a cutoff voltage of 4.2V, and 4.2V constant voltage charging to 0.05C; 0.5C discharging to 5% SOC, with a cutoff voltage of 2.8V; repeating 1600 cycles, the capacity of the battery after cycling was tested, and the cycle retention rate after 1100 cycles was calculated.

[0299] (3) Test for leakage of individual battery cells. The test method is as follows: charge the individual battery cells to 100% SOC, store them upside down at 45°C, and record the battery voltage, the condition of the explosion-proof valve, and the corrosion of the aluminum shell. If abnormal voltage fluctuations or corrosion of the explosion-proof valve or aluminum shell occur, there is a long-term risk of leakage.

[0300] Table 1

[0301]

[0302] In Table 1, X c2This indicates the cold crystallinity of the hydrophilic polymer. Tc2 represents the cold crystallization temperature of the hydrophilic polymer, in °C. Molecular weight is in 10,000 g / mol. 'a' represents the mass percentage of the hydrophilic polymer in the positive electrode active layer. 'b' represents the mass percentage of the hydrophilic polymer in the negative electrode active layer. 'c' represents the volume of free electrolyte in the battery cell, in mL. In the 'Single' column, VDF+HFP indicates that the hydrophilic polymer consists of VDF and HFP monomers. The values ​​in parentheses represent the molar percentages of VDF and HFP as a percentage of the total molar ratio of VDF and HFP monomers. For example, VDF+HFP (91%:9%) means that the molar percentages of VDF and HFP as a percentage of the total molar ratio of VDF and HFP monomers are 91% and 9%, respectively.

[0303] By testing the leakage of individual battery cells in the examples and comparative examples, leakage was found in the individual battery cells of Comparative Example 1, while no leakage was found in the examples and comparative examples 2.

[0304] Table 2

[0305]

[0306] As can be seen from Table 2, when the battery cell contains a hydrophilic polymer and has a low amount of free electrolyte, the battery cell can achieve both high energy density and good cycle performance.

[0307] Table 3

[0308]

[0309] As can be seen from Table 3, when the volume of free electrolyte in a single battery cell is less than or equal to 10 mL, the battery cell exhibits good cycle performance.

[0310] Table 4

[0311]

[0312] As can be seen from Table 3, when the molar ratio of the hydrophilic polymer monomers is within a suitable range, the battery cells exhibit good cycle performance.

[0313] Table 5

[0314]

[0315] As shown in Table 5, when the mass percentage of the hydrophilic polymer in the positive electrode active layer is 0.1% to 2% and the mass percentage of the hydrophilic polymer in the negative electrode active layer is 1% to 5%, the battery cell has good cycle performance.

[0316] Table 6

[0317]

[0318] As shown in Table 6, when the molar percentage of nickel in lithium nickel manganese cobalt oxide is 80% to 95% (based on the molar percentage of nickel, manganese, and cobalt), the battery cell can achieve both high energy density and good cycle performance.

[0319] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0320] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A battery cell, characterized in that, include: A housing having an opening; An end cap, the end cap being used to close the opening; Electrode terminals, wherein the electrode terminals are disposed on the end cap; Along the direction of gravity, the electrode terminals are located at the bottom of the housing; An electrode assembly, the electrode assembly being housed within the housing; The electrode assembly includes a positive electrode, a separator, and a negative electrode, wherein the separator is disposed between the positive electrode and the negative electrode; at least one of the positive electrode, the separator, and the negative electrode contains a gel electrolyte; the gel electrolyte includes a hydrophilic polymer and a limiting electrolyte, wherein the limiting electrolyte is located inside the hydrophilic polymer; The free electrolyte in the shell is less than or equal to 10 mL.

2. The battery cell according to claim 1, characterized in that, The free electrolyte in the casing is less than or equal to 2 mL.

3. The battery cell according to claim 1 or 2, characterized in that, The material of the housing includes one or more of aluminum, aluminum alloys, and stainless steel.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The gel electrolyte is uniformly distributed in at least one of the positive electrode, the separator, and the negative electrode.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The positive electrode sheet 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 containing the gel electrolyte and the positive active material.

6. The battery cell according to claim 5, characterized in that, The gel electrolyte satisfies one or more of the following characteristics: (1) The gel electrolyte is distributed on the surface of the particles of the positive electrode active material; (2) The gel electrolyte is distributed in the pores between the particles of the positive electrode active material.

7. The battery cell according to claim 5 or 6, characterized in that, In the positive electrode active layer, the hydrophilic polymer accounts for 0.1% to 2% of the mass percentage of the positive electrode active layer.

8. The battery cell according to any one of claims 5 to 7, characterized in that, The positive electrode active material includes one or more of lithium nickel manganese cobalt oxide and lithium phosphate; in the lithium nickel manganese cobalt oxide, the molar percentage of nickel is 50% to 95%, optionally 80% to 95%, based on the molar percentage of nickel, manganese and cobalt elements.

9. The battery cell according to any one of claims 5 to 8, characterized in that, The density of the positive electrode active layer is 2 g / cm³. 3 ~3.8g / cm 3 ; Optionally, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the density of the positive electrode active layer is 3.5 g / cm³. 3 ~3.8g / cm 3 ; Optionally, the positive electrode active material includes lithium phosphate, and the density of the positive electrode active layer is 2 g / cm³. 3 ~3g / cm 3 .

10. The battery cell according to any one of claims 5 to 9, characterized in that, The positive electrode current collector includes a first support layer and a first metal layer, wherein the first metal layer is located on at least one surface of the first support layer and between the first support layer and the positive electrode active layer.

11. The battery cell according to claim 10, characterized in that, The thickness of the first metal layer is 200nm~2000nm.

12. The battery cell according to any one of claims 1 to 11, characterized in that, The negative electrode sheet includes a negative current collector and a negative active layer located on at least one surface of the negative current collector, the negative active layer containing the gel electrolyte and the negative active material.

13. The battery cell according to claim 12, characterized in that, The gel electrolyte satisfies one or more of the following characteristics: (1) The gel electrolyte is distributed on the surface of the particles of the negative electrode active material; (2) The gel electrolyte is distributed in the pores between the particles of the negative electrode active material.

14. The battery cell according to claim 12 or 13, characterized in that, In the negative electrode active layer, the hydrophilic polymer accounts for 1% to 5% of the mass percentage of the negative electrode active layer.

15. The battery cell according to any one of claims 12 to 14, characterized in that, The density of the negative electrode active layer is 1 g / cm³. 3 ~2g / cm 3 Optionally, it can be 1.3 g / cm³. 3 ~1.7g / cm 3 .

16. The battery cell according to any one of claims 12 to 15, characterized in that, The negative electrode current collector includes a second support layer and a second metal layer, the second metal layer being located on at least one surface of the second support layer and between the second support layer and the negative electrode active layer.

17. The battery cell according to claim 16, characterized in that, The thickness of the second metal layer is 200nm~2000nm.

18. The battery cell according to any one of claims 1 to 17, characterized in that, The gel electrolyte is distributed in the pores of the separating membrane.

19. The battery cell according to any one of claims 1 to 18, characterized in that, The separator includes a separator substrate and a coating located on at least one surface of the separator substrate, the coating containing particulate filler; Optionally, the particulate filler includes one or more of boehmite, alumina, silica, and magnesium hydroxide; Optionally, the thickness of the coating is 0.25 μm to 5 μm; Optionally, the material of the separator substrate includes one or more of polyethylene, polypropylene, polyimide, and aramid.

20. The battery cell according to any one of claims 1 to 19, characterized in that, The lyophilic polymer includes a fluorinated polymer; the crystallinity of the fluorinated polymer, as determined by differential scanning calorimetry, is X. c1 15%≤X c1 ≤25%; the melting temperature of the fluoropolymer is T m1 Its unit is ℃, 120≤T m1 ≤140.

21. The battery cell according to any one of claims 1 to 19, characterized in that, 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 according to claim 20 or 21, characterized in that, The monomers of the fluorinated polymer include hexafluoropropylene and vinylidene fluoride; Optionally, the molar percentage of hexafluoropropylene is 6% to 13% based on the total molar ratio of the hexafluoropropylene and the vinylidene fluoride.

23. The battery cell according to any one of claims 20 to 22, characterized in that, The fluoropolymer includes at least one of the structural units shown in formula (A1) to formula (AIII). Formula (AI) Formula (AII), In equations (AI) and (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 them contains a fluorine atom; when substituted, the substituents include one or more of the following: nitrile (-CN), nitro, sulfonic acid, sulfonyl, amide, carboxyl, ester, and halogen atom; Formula (AIII); In equation (AIII), R 15 Includes single bonds, substituted or unsubstituted C1-C3 alkyl groups; when substituted, the substituents include one or more of nitrile (-CN), nitro, sulfonic acid, sulfonyl, amide, carboxyl, ester, and halogen atoms; p is selected from positive integers from 1 to 3; n is selected from positive integers from 1000 to 30000.

24. The battery cell according to any one of claims 1 to 23, characterized in that, The molecular weight of the hydrophilic polymer is 1.2 × 10⁻⁶. 5 g / mol to 1×10 6 g / mol.

25. The battery cell according to any one of claims 1 to 24, characterized in that, The lithium-ion transference number of the gel electrolyte is ≥0.

4.

26. A battery, characterized in that, Includes the battery cell according to any one of claims 1 to 25.

27. An electrical appliance, characterized in that, Includes the battery as described in claim 26.

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