Battery cell, method for preparing battery cell, battery device and electric device

Abstract

Provided in the present application are a battery cell, a method for preparing a battery cell, a battery device and an electric device. The battery cell of the present application comprises a positive electrode sheet, a negative electrode sheet and a pouch-type separator. At least one side edge of the pouch-type separator is sealed with a hot melt adhesive. One of the negative electrode sheet and the positive electrode sheet is disposed inside the pouch-type separator, and the other is disposed outside the pouch-type separator; alternatively, the negative electrode sheet and the positive electrode sheet are respectively disposed inside two adjacent pouch-type separators. The hot melt adhesive comprises a copolymer of C2-6 alkene and C2-6 alkenyl C1-6 carboxylate, a C2-6 polyolefin and a polymer, wherein monomers of the polymer comprise monomer 1, i.e., C2-6 alkenyl C1-6 carboxylate, and monomer 2, i.e., C2-6 alkyl C3-6 alkenoate. The pouch-type separator of the battery cell of the present application is not prone to debonding during cycling. The positive electrode sheet and / or the negative electrode sheet are / is confined within the pouch-type separator, thereby reducing the migration of dead lithium resulting from negative electrode pulverization toward the positive electrode, inhibiting the micro-short circuit and overcharge of the battery cell, and improving the safety performance of the battery cell.

Description

Battery cells, methods for preparing battery cells, battery devices and electrical devices

[0001] This application is based on and claims priority to CN application number 202411703236.1, filed on November 26, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, and in particular to a battery cell, a method for preparing a battery cell, a battery device, and an electrical device. Background Technology

[0003] In recent years, with the increasingly wide range of applications, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. Due to the significant advancements in battery technology, higher requirements have been placed on their safety performance and other aspects. Summary of the Invention

[0004] This application was made in view of the above-mentioned problems, and its purpose is to provide a battery cell, a method for preparing a battery cell, a battery device, and an electrical device. The pouch-shaped separator in the battery cell of this application is less prone to delamination during charge-discharge cycles. It confines the positive and / or negative electrode sheets within the pouch-shaped separator, reducing the migration of dead lithium from the negative electrode to the positive electrode, suppressing micro-short circuits and overcharging in the battery cell, and improving the safety performance of the battery cell.

[0005] To achieve the above objectives, the first aspect of this application provides a battery cell including a positive electrode, a negative electrode, and a separator, wherein the separator is bag-shaped and at least one side of the bag-shaped separator is sealed with hot melt adhesive.

[0006] One of the negative electrode and the positive electrode is located inside the bag-shaped diaphragm, and the other is located outside the bag-shaped diaphragm; or, the negative electrode and the positive electrode are respectively located inside two adjacent bag-shaped diaphragms.

[0007] Wherein, the hot melt adhesive includes C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 olefin ester copolymers, C 2- 6. Polyolefins and polymers, wherein the monomers of the polymers include monomer 1 and monomer 2 as follows;

[0008] Monomer 1: C 1-6 Carboxylic acid C 2-6 Olefin esters;

[0009] Monomer 2: C 3-6 Acetic acid C2-6 Alcohol esters.

[0010] The pouch-shaped separator of this application is less prone to delamination during battery cell charge-discharge cycles, reducing the migration of pulverized dead lithium from the negative electrode to the positive electrode, suppressing micro-short circuits and overcharging in the battery cells, and improving the safety performance of the battery cells. Furthermore, the hot melt adhesive of this application remains stable during battery cell charge-discharge cycles with almost no impurity leakage, reducing the negative impact on battery cell performance. In addition, the pouch-shaped separator restricts the movement of the negative electrode, suppressing sliding misalignment of the negative electrode relative to the separator, and solving the problem of battery cell short circuits caused by this.

[0011] In any embodiment, the hot melt adhesive comprises:

[0012] The C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 51-63 parts by weight of olefin ester copolymer;

[0013] The C 2-6 6-15 parts by weight of polyolefin;

[0014] The polymer is 15-41 parts by weight.

[0015] Therefore, on the one hand, the hot melt adhesive has a suitable viscosity, which can improve the adhesion performance to the side of the bag-shaped separator and make the hot melt adhesive evenly coated on the side of the bag-shaped separator; on the other hand, it can control the heat sealing temperature of the hot melt adhesive to not exceed the upper limit of the separator, suppress or avoid the thermal shrinkage of the separator, thereby solving the problem of short circuit of battery cells caused by separator shrinkage.

[0016] In any embodiment, the molar ratio of monomer 1 to monomer 2 is 5:5-8:2. Therefore, the hot melt adhesive has a suitable viscosity, which improves both the adhesive performance and the coating uniformity of the hot melt adhesive.

[0017] In any implementation, the C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 Olefin ester copolymers are C 2-4 Olefin-C 1-4 Carboxylic acid C 2-4 Olefin ester copolymers.

[0018] In any implementation, the C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 Olefin ester copolymers include one or more of ethylene-vinyl acetate copolymers, propylene-propylene acetate copolymers, and propylene-propylene propionate copolymers.

[0019] In any implementation, the C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 The number average molecular weight of olefin ester copolymers is 50,000–100,000.

[0020] In any implementation, the C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 C in olefin ester copolymers 1-6 Carboxylic acid C 2-6 The olefin molar content is 20%-30%.

[0021] In any embodiment, the hot melt adhesive comprises 8-15 parts by weight of the C 2-6 Polyolefins. This helps maintain the heat-sealing temperature of the hot melt adhesive within the diaphragm's maximum tolerance.

[0022] In any implementation, the C 2-6 Polyolefins are C 2-4 Polyolefins.

[0023] In any implementation, the C 2-6 Polyolefins include one or more of polyethylene, polypropylene, and polybutene.

[0024] In any implementation, the C 2-6 The number average molecular weight of polyolefins ranges from 30,000 to 120,000.

[0025] In any embodiment, the hot melt adhesive comprises 22-41 parts by weight of the polymer.

[0026] In any embodiment, monomer 1 is C 1-4 Carboxylic acid C 2-4 Olefin esters.

[0027] In any embodiment, the monomer 1 is selected from any one of vinyl acetate, vinyl propionate, and vinyl butyrate.

[0028] In any embodiment, the monomer 2 is C 3-4 Acetic acid C 2-4 Alcohol esters.

[0029] In any embodiment, the monomer 2 is selected from any one of butyl acrylate, methyl acrylate, ethyl acrylate, ethyl butyrate, and butyl butyrate.

[0030] In any embodiment, the monomer of the polymer further includes monomer 3 as follows;

[0031] Monomer 3:

[0032] Among them, R1 is selected from C 2-6 Alkenyl group, R2 is selected from C 7-10 Alkyl, hydroxyl C 1-6 Any one of alkyl and isobornyl.

[0033] Therefore, under the premise that the heat sealing temperature of the hot melt adhesive does not exceed the upper limit of the membrane, the introduction of monomer 3 can control the hot melt adhesive to have a more suitable viscosity, improve the adhesion of the hot melt adhesive, make the bag-shaped membrane less prone to opening, reduce the migration of pulverized dead lithium from the negative electrode to the positive electrode, and at the same time improve the coating uniformity of the hot melt adhesive to improve the sealing effect.

[0034] In any embodiment, the molar ratio of monomer 3 to the sum of monomer 1 and monomer 2 is 1:9-5:5.

[0035] In any implementation, R1 is selected from C. 2-4 olefins; and / or,

[0036] R2 is selected from C 7-8 Alkyl, hydroxyl C 1-4 Any one of alkyl and isobornyl.

[0037] In any embodiment, the monomer 3 includes one or more of isooctyl acrylate, hydroxyethyl acrylate, and isobornyl acrylate.

[0038] In any embodiment, the hot melt adhesive further includes 6-8 parts by weight of a viscosity modifier.

[0039] This helps to control the adhesive properties of hot melt adhesive, reduce delamination, and improve the uniformity of hot melt adhesive coating, thereby enhancing the sealing effect.

[0040] In any embodiment, the viscosity modifier includes one or more of rosin and paraffin.

[0041] In any embodiment, the viscosity modifier comprises rosin and paraffin wax, wherein the weight ratio of the rosin and paraffin wax is 1:4 to 1:1.

[0042] In any embodiment, the melting temperature of the hot melt adhesive is 45-110°C, 45-90°C, or 45-80°C. Therefore, the temperature at which the hot melt adhesive heat-seals the bag-shaped separator in this application exceeds the separator's maximum tolerance, preventing separator shrinkage. Furthermore, during battery cell cycling, the hot melt adhesive with the aforementioned melting temperature maintains good sealing of the bag-shaped separator and is less prone to delamination.

[0043] In any embodiment, the viscosity of the hot melt adhesive at 25°C is 3800-10000 mPa·s, 5000-10000 mPa·s, or 5000-8200 mPa·s. Therefore, the hot melt adhesive used in this application exhibits good coating uniformity on the diaphragm side, provides excellent sealing for the bag-shaped diaphragm, and is less prone to delamination.

[0044] In any embodiment, the two opposite sides of the bag-shaped diaphragm are sealed with the hot melt adhesive.

[0045] Therefore, the negative electrode and / or positive electrode can be confined within the pouch-shaped separator, reducing the migration of dead lithium from the pulverized negative electrode to the positive electrode and improving the safety performance of the battery cell. In particular, confining the negative electrode within the pouch-shaped separator helps to suppress the sliding misalignment of the negative electrode relative to the separator in the stacked battery cell.

[0046] In any embodiment, the three sides of the bag-shaped diaphragm are sealed with the hot melt adhesive.

[0047] This reduces the migration of dead lithium from the negative electrode to the positive electrode, thus improving the safety performance of the battery cell. Furthermore, confining the negative electrode within the pouch-shaped separator helps suppress the sliding misalignment of the negative electrode relative to the separator in the stacked battery cell.

[0048] In any embodiment, the hot melt adhesive is distributed along the length of the side of the bag-shaped diaphragm, the length of the hot melt adhesive distribution is equal to the length of the side of the bag-shaped diaphragm, and the width of the hot melt adhesive distribution is 1-8 mm or 1.5-5 mm; the width direction of the hot melt adhesive distribution is perpendicular to the length direction of the hot melt adhesive distribution.

[0049] This allows the battery cells to maintain a high energy density while improving the sealing of the bag-shaped separator side, reducing the migration of dead lithium from the negative electrode to the positive electrode, and thus improving the safety performance of the battery cells.

[0050] In any embodiment, the membrane includes a base layer, wherein the base layer comprises one or more polyolefin materials.

[0051] In any embodiment, the diaphragm further includes a functional layer located on at least one side of the substrate layer, each of the functional layers independently comprising one or more of a ceramic material, a polycarbosilane material, a polyvinyl chloride material, and a polycarbonate material.

[0052] In any embodiment, the battery cell is a stacked battery cell.

[0053] A second aspect of this application provides a method for preparing a battery cell, comprising the following steps:

[0054] Place one of the negative and positive electrode plates inside the bag-shaped diaphragm, and the other outside the bag-shaped diaphragm, aligning them; or,

[0055] Place the negative electrode and the positive electrode in two adjacent bag-shaped diaphragms respectively, and align them;

[0056] The bag-shaped diaphragm is manufactured by either method one or method two as follows:

[0057] Method 1 includes the following steps:

[0058] The raw material is cut into diaphragms; hot melt adhesive is applied to either side or opposite sides of the diaphragm before or after cutting, and then cooled.

[0059] The diaphragm is folded along the length of the side coated with hot melt adhesive and then heat-sealed to obtain a bag-shaped diaphragm.

[0060] The second method includes the following steps:

[0061] The raw material is cut into diaphragms; hot melt adhesive is applied to three sides of the diaphragms before or after cutting, and then cooled.

[0062] Three sides of multiple diaphragms of the same size, coated with the hot melt adhesive, are heat-sealed to obtain a bag-shaped diaphragm.

[0063] Furthermore, the hot melt adhesive includes C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 olefin ester copolymers, C 2- 6. Polyolefins and polymers, wherein the monomers of the polymers include monomer 1 and monomer 2 as follows;

[0064] Monomer 1: C 1-6 Carboxylic acid C 2-6 Olefin esters;

[0065] Monomer 2: C 3-6 Acetic acid C 2-6 Alcohol esters.

[0066] The pouch-shaped separator of this application is less prone to delamination during battery cell charge-discharge cycles, reducing the migration of pulverized dead lithium from the negative electrode to the positive electrode, suppressing micro-short circuits and overcharging in the battery cells, and improving the safety performance of the battery cells. Furthermore, the hot melt adhesive of this application remains stable during battery cell charge-discharge cycles with almost no impurity leakage, reducing the negative impact on battery cell performance. In addition, the pouch-shaped separator restricts the movement of the negative electrode, suppressing sliding misalignment of the negative electrode relative to the separator, and solving the problem of battery cell short circuits caused by this.

[0067] In any embodiment, the hot melt adhesive is applied along the length of the diaphragm side, the length of the hot melt adhesive application is equal to the length of the diaphragm side, and the width of the hot melt adhesive application is 1-8 mm or 1.5-5 mm; the width direction of the hot melt adhesive application is perpendicular to the length direction of the hot melt adhesive application.

[0068] In any embodiment, the hot melt adhesive is applied at 45-110°C, 45-90°C, or 45-80°C; and / or,

[0069] The heat sealing temperature is 45-110℃, 45-90℃, or 45-80℃; and / or,

[0070] The heat sealing time is 0.5–10 minutes.

[0071] In any embodiment, the monomer of the polymer further includes monomer 3 as follows;

[0072] Monomer 3:

[0073] Among them, R1 is selected from C 2-6 Alkenyl group, R2 is selected from C 7-10 Alkyl, hydroxyl C 1-6 Any one of alkyl and isobornyl.

[0074] In any embodiment, the hot melt adhesive further includes a viscosity modifier, which includes one or more of rosin and paraffin.

[0075] In any embodiment, the hot melt adhesive comprises 51-63 parts by weight of the C. 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 olefin ester copolymer, 6-15 parts by weight of the aforementioned C 2-6 Polyolefin and 15-41 parts by weight of the polymer.

[0076] In any embodiment, the molar ratio of monomer 1 to monomer 2 is 5:5-8:2.

[0077] In any embodiment, the molar ratio of monomer 3 to the sum of monomer 1 and monomer 2 is 1:9-5:5.

[0078] In any embodiment, the hot melt adhesive further includes 6-8 parts by weight of the viscosity modifier.

[0079] In any embodiment, the weight ratio of the rosin and the paraffin in the viscosity modifier is 1:4 to 1:1.

[0080] In any embodiment, the battery cell obtained is the battery cell of the first aspect of this application.

[0081] A third aspect of this application provides a battery device, including a battery cell according to the first aspect of this application or a battery cell obtained by the method of the second aspect of this application.

[0082] The fourth aspect of this application provides an electrical device, including a battery cell of the first aspect of this application or a battery device of the third aspect of this application. Attached Figure Description

[0083] Figure 1 is a schematic diagram of a battery cell according to one embodiment of this application.

[0084] Figure 2 is an exploded view of a battery cell according to an embodiment of this application shown in Figure 1.

[0085] Figure 3 is a schematic diagram of a battery module according to one embodiment of this application.

[0086] Figure 4 is a schematic diagram of a battery pack according to one embodiment of this application.

[0087] Figure 5 is an exploded view of the battery pack of one embodiment of this application shown in Figure 4.

[0088] Figure 6 is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to an embodiment of this application.

[0089] Figure 7 is a flowchart of the fabrication of the bag-shaped diaphragm in Embodiment 1 of this application.

[0090] Figure 8A is a chromatogram of the electrolyte dilution solution before charging and discharging of a single battery cell in Example 1 of this application.

[0091] Figure 8B is a chromatogram of the electrolyte dilution solution after charging and discharging of a single battery cell in Example 1 of this application.

[0092] Figure 9 is a side view of the bag-shaped separator after the battery cell of Embodiment 1 of this application has been cycled.

[0093] Figure 10 is a side view of the bag-shaped battery cell of Comparative Example 1 after cycling.

[0094] Figure 11 shows the curves of the charging capacity / discharging capacity of the battery cells in Embodiment 1 and Comparative Example 1 of this application as a function of the number of cycles.

[0095] Explanation of reference numerals in the attached diagram: 1-Battery pack; 2-Upper casing; 3-Lower casing; 4-Battery module; 5-Battery cell; 51-House casing; 52-Electrode assembly; 53-Top cover assembly; 6-Separator; 7-Hot melt adhesive. Detailed Implementation

[0096] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, battery module, battery pack, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0097] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0098] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0099] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. 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.

[0100] Unless otherwise specified, olefins in this application refer to straight-chain or branched hydrocarbons containing at least one carbon-carbon double bond, including, for example, "C". 2-6 "olefins", "C" 2-4 "Olefins", etc. Examples include, but are not limited to: ethylene, propylene, 1-butene, 2-butene, 1,3-butadiene, 1-pentene, 2-pentene, 3-pentene, 1,3-pentadiene, 1,4-pentadiene, 1-hexene, 2-hexene, 3-hexene, 1,4-hexadiene, etc.

[0101] Unless otherwise specified, the alkanes in this application refer to straight-chain or branched saturated alkanes, such as "C 1-6 Alkanes, C 1-4 Alkanes, C 1-3 Alkanes, C 7-10 "Alkanes", etc., specific examples include but are not limited to: methane, ethane, n-propane, isopropane, n-butane, isobutane, sec-butane, tert-butane, n-pentane, isopentane, 2-methylbutane, neopentane, 1-ethylpropane, n-hexane, isohexane, 3-methylpentane, 2-methylpentane, etc.

[0102] Unless otherwise specified, the carboxylic acid in this application refers to a compound obtained by replacing at least one methyl group in an alkane with a -COOH group. Alkanes are defined as described above. For example, "C 1-6 "Carboxylic acid", "C" 1-4 "Carboxylic acid", "C" 1-3 "Carboxylic acid", "C" 1-2 Carboxylic acids, etc., specific examples include but are not limited to: formic acid, acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid, isovaleric acid, etc.

[0103] Unless otherwise specified, enols in this application refer to compounds obtained by substituting at least one hydrogen atom in an alkene with a hydroxyl group. The definition of an alkene is as described above. For example, "C 2-6 Enols, C 2-4 Enols, etc. Specific examples include, but are not limited to: vinyl alcohol, 1-propen-2-ol, 1-propen-3-ol, 1-buten-3-ol, 1-buten-4-ol, 2-buten-1-ol, 2-buten-2-ol, etc.

[0104] Unless otherwise specified, the carboxylic acid olefin esters in this application refer to esters formed from carboxylic acids and enols. The definitions of carboxylic acids and enols are as described above. For example, "C..." 1-6 Carboxylic acid C 2-6 "olefin ester", "C" 1-4 Carboxylic acid C 2-4 "olefin ester", "C" 1-3 Carboxylic acid C 2-3 "Olefin esters", etc. Specific examples include, but are not limited to: vinyl acetate, propylene acetate, propylene propionate, vinyl propionate, vinyl butyrate, etc.

[0105] Unless otherwise specified, the olefinic acid in this application refers to a compound obtained by replacing at least one methyl group in an olefin with a -COOH group. The definition of an olefin is as described above. For example, "C 3-8 "ecnic acid", "C" 3-6 "ecnic acid", "C" 3-4 Examples of such substances include, but are not limited to, acrylic acid and butylated acid.

[0106] Unless otherwise specified, in this application, "alcohol" refers to a compound obtained by substituting at least one hydrogen atom in an alkane with a hydroxyl group. The definition of an alkane is as described above. For example, "C..." 1-6 "alcohol", "C" 2-6 "alcohol", "C" 2-4 "alcohol", "C" 2-3 "Alcohols", etc. Specific examples include, but are not limited to: methanol, ethanol, isopropanol, etc.

[0107] Unless otherwise specified, the enoic acid alcohol esters in this application refer to esters formed from enoic acids and alcohols. The definitions of enoic acids and alcohols are as described above. For example, "C..." 3-6 Acetic acid C2-6 "Alcohol ester", "C" 3-4 Acetic acid C 2-4 "Alcohol ester", "C" 3-4 Acetic acid C 2-3 "Alcohol esters", etc. Specific examples include, but are not limited to: butyl acrylate, methyl acrylate, ethyl acrylate, ethyl butyrate, butyl butyrate, etc.

[0108] Unless otherwise specified, the polyolefins in this application refer to copolymers formed by the polymerization of olefins. The definition of olefins is as described above. For example, C 2-6 Polyolefins, C 2-4 Polyolefins, C 2-3 Polyolefins, etc. Specific examples include, but are not limited to: polyethylene, polypropylene, poly-1-butene, poly-2-butene, etc.

[0109] Unless otherwise specified, alkyl in this application refers to a group obtained by removing one hydrogen atom from an alkane. The definition of alkane is as described above. Examples include "C1-C6 alkyl", "C1-C4 alkyl", "C1-C3 alkyl", etc. Specific examples include, but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, 2-methylbutyl, neopentyl, 1-ethylpropyl, n-hexyl, isohexyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,3-dimethylbutyl, 2-ethylbutyl, 1,2-dimethylpropyl, etc.

[0110] Unless otherwise specified, in this application, hydroxyalkyl refers to a group formed by replacing at least one hydrogen atom in an alkyl group with a hydroxyl group. The definition of alkyl is as described above. For example, "hydroxyl C..." 1-6 Alkyl group, hydroxyl group 1-4 Alkyl group, hydroxyl group 1-3 Alkyl groups, etc., specific examples include but are not limited to: hydroxymethyl, hydroxyethyl, 1-hydroxypropyl, 2-hydroxypropyl, etc.

[0111] Unless otherwise specified, the alkenyl group in this application refers to the group obtained by removing one hydrogen atom from an alkene. The definition of an alkene is as described above. For example, "C 2-6 "alkenyl", "C" 2-4 Examples of these include, but are not limited to, vinyl, 1-propenyl, 2-propenyl, 3-propenyl, 1-butenyl, and 2-butenyl.

[0112] Unless otherwise specified, the structural formula of isoborneol in this application is as follows:

[0113] [Battery cell]

[0114] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0115] The battery cell can be a lithium metal battery, a lithium sulfur battery, etc., but this application does not limit this.

[0116] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator positioned between the positive and negative electrodes. During the charging and discharging process of a single battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits while allowing active ions to pass through.

[0117] During charge-discharge cycles, pulverized dead lithium produced on the negative electrode can easily drift to the positive electrode, causing micro-short circuits and overcharging in the battery cell, thus affecting its safety performance. Additionally, when using stacked battery cells, the negative electrode can easily slide relative to the separator, leading to misalignment and causing short circuits in the battery cell.

[0118] To solve the above-mentioned technical problems, one embodiment of this application provides a battery cell, including a positive electrode, a negative electrode and a separator, wherein the separator is bag-shaped and at least one side of the bag-shaped separator is sealed with hot melt adhesive.

[0119] One of the negative electrode and the positive electrode is located inside the bag-shaped diaphragm, and the other is located outside the bag-shaped diaphragm; or, the negative electrode and the positive electrode are respectively located inside two adjacent bag-shaped diaphragms.

[0120] Wherein, the hot melt adhesive includes C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 olefin ester copolymers, C 2- 6. Polyolefins and polymers, wherein the monomers of the polymers include monomer 1 and monomer 2 as follows;

[0121] Monomer 1: C 1-6 Carboxylic acid C 2-6 Olefin esters;

[0122] Monomer 2: C 3-6 Acetic acid C 2-6 Alcohol esters.

[0123] The applicant unexpectedly discovered that the hot melt adhesive used in this application provides a good seal on the sides of the pouch-shaped separator, making it less prone to separation during battery cell charge-discharge cycles. This confines the negative electrode and / or positive electrode within the pouch-shaped separator, reducing the migration of pulverized dead lithium from the negative electrode to the positive electrode, suppressing micro-short circuits and overcharging in the battery cells, and improving the safety performance of the battery cells. Furthermore, the hot melt adhesive in this application remains stable during battery cell charge-discharge cycles with almost no impurity leakage, reducing the negative impact of impurities on battery cell performance. Additionally, the pouch-shaped separator restricts the movement of the negative electrode, suppressing slippage and misalignment of the negative electrode relative to the separator, thus resolving the resulting battery cell short circuit problem.

[0124] In some embodiments, the hot melt adhesive includes:

[0125] The C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 51-63 parts by weight of olefin ester copolymer (e.g., 51 parts by weight, 53 parts by weight, 55 parts by weight, 56 parts by weight, 58 parts by weight, 59 parts by weight, 60 parts by weight, 61 parts by weight, 63 parts by weight or any range of the above values);

[0126] The C 2-6 6-15 parts by weight of polyolefin (e.g., 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 12 parts by weight, 13 parts by weight, 15 parts by weight or any range of the above values);

[0127] The polymer is 15-41 parts by weight (e.g., 15 parts by weight, 18 parts by weight, 20 parts by weight, 22 parts by weight, 25 parts by weight, 27 parts by weight, 30 parts by weight, 32 parts by weight, 34 parts by weight, 35 parts by weight, 37 parts by weight, 38 parts by weight, 40 parts by weight, 41 parts by weight, or any range of the above values).

[0128] Therefore, on the one hand, the hot melt adhesive has a suitable viscosity, which can improve the adhesion performance to the side of the bag-shaped separator and make the hot melt adhesive evenly coated on the side of the bag-shaped separator; on the other hand, it can control the heat sealing temperature of the hot melt adhesive to not exceed the upper limit of the separator, suppress or avoid the thermal shrinkage of the separator, thereby solving the problem of short circuit of battery cells caused by separator shrinkage.

[0129] In some embodiments, the molar ratio of monomer 1 to monomer 2 is 5:5 to 8:2, for example, 5:5, 6:4, 7:3, 8:2, or any range of the above values. Therefore, the hot melt adhesive has a suitable viscosity, which improves both the adhesive performance and the uniformity of the hot melt adhesive coating.

[0130] In some implementations, the C2-6 Olefin-C 1-6 Carboxylic acid C 2-6 Olefin ester copolymers are C 2-4 Olefin-C 1-4 Carboxylic acid C 2-4 Olefin ester copolymers.

[0131] In some implementations, the C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 Olefin ester copolymers include one or more of ethylene-vinyl acetate copolymers, propylene-propylene acetate copolymers, and propylene-propylene propionate copolymers.

[0132] In some implementations, the C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 The number average molecular weight of the olefin ester copolymer is 50,000 to 100,000, for example, 50,000, 60,000, 70,000, 80,000, 90,000, 100,000 or any combination of the above values.

[0133] In some implementations, the C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 C in olefin ester copolymers 1-6 Carboxylic acid C 2-6 The olefin molar content is 20%-30%, for example, 20%, 25%, 30% or any of the above values.

[0134] In some embodiments, the hot melt adhesive comprises 8-15 parts by weight of the C 2-6 Polyolefins. This helps maintain the heat-sealing temperature of the hot melt adhesive within the diaphragm's maximum tolerance.

[0135] In some implementations, the C 2-6 Polyolefins are C 2-4 Polyolefins.

[0136] In some implementations, the C 2-6 Polyolefins include one or more of polyethylene, polypropylene, and polybutene.

[0137] In some implementations, the C 2-6 The number average molecular weight of polyolefins is 30,000 to 120,000, for example, 30,000, 40,000, 50,000, 60,000, 70,000, 80,000, 90,000, 100,000, 110,000, 120,000 or any combination of the above values.

[0138] In some embodiments, the hot melt adhesive comprises 22-41 parts by weight of the polymer.

[0139] In some embodiments, monomer 1 is C1-4 Carboxylic acid C 2-4 Olefin esters.

[0140] In some embodiments, the monomer 1 is selected from any one of vinyl acetate, vinyl propionate, and vinyl butyrate.

[0141] In some embodiments, the monomer 2 is C 3-4 Acetic acid C 2-4 Alcohol esters.

[0142] In some embodiments, the monomer 2 is selected from any one of butyl acrylate, methyl acrylate, ethyl acrylate, ethyl butyrate, and butyl butyrate.

[0143] In some embodiments, the monomer of the polymer further includes monomer 3 as follows;

[0144] Monomer 3:

[0145] Among them, R1 is selected from C 2-6 Alkenyl group, R2 is selected from C 7-10 Alkyl, hydroxyl C 1-6 Any one of alkyl and isobornyl.

[0146] Therefore, under the premise that the heat sealing temperature of the hot melt adhesive does not exceed the upper limit of the membrane, the introduction of monomer 3 can control the hot melt adhesive to have a more suitable viscosity, improve the adhesion of the hot melt adhesive, make the bag-shaped membrane less prone to opening and sticking, reduce the migration of dead lithium from the negative electrode to the positive electrode, and at the same time improve the coating uniformity of the hot melt adhesive to improve the sealing effect.

[0147] In some embodiments, the molar ratio of monomer 3 to the sum of monomer 1 and monomer 2 is 1:9 to 5:5, for example, 1:9, 2:8, 3:7, 4:6, 5:5 or any range of the above values.

[0148] In some implementations, R1 is selected from C 2-4 olefins; and / or,

[0149] R2 is selected from C 7-8 Alkyl, hydroxyl C 1-4 Any one of alkyl and isobornyl.

[0150] In some embodiments, the monomer 3 includes one or more of isooctyl acrylate, hydroxyethyl acrylate, and isobornyl acrylate.

[0151] In some embodiments, the hot melt adhesive further includes 6-8 parts by weight (e.g., 6 parts by weight, 6.5 parts by weight, 7 parts by weight, 7.5 parts by weight, 8 parts by weight, or any range of the above values).

[0152] This helps to control the adhesive properties of hot melt adhesive, reduce delamination, and improve the uniformity of hot melt adhesive coating, thereby enhancing the sealing effect.

[0153] In some embodiments, the viscosity modifier includes one or more of rosin and paraffin.

[0154] In some embodiments, the viscosity modifier comprises rosin and paraffin, wherein the weight ratio of the rosin and paraffin is 1:4 to 1:1, for example, 1:1, 1:2, 1:3, 1:4 or any range of the above values.

[0155] In some embodiments, the melting temperature of the hot melt adhesive is 45-110°C, 45-90°C, or 45-80°C, for example, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, or any combination of the above values. Therefore, the temperature at which the hot melt adhesive heat-seals the bag-shaped separator in this application exceeds the separator's tolerance limit, preventing separator shrinkage. Furthermore, during battery cell cycling, the hot melt adhesive with the aforementioned melting temperature maintains good sealing performance of the bag-shaped separator and is less prone to delamination.

[0156] In this application, the melting temperature of the hot melt adhesive is tested using methods conventional in the art, such as differential scanning calorimetry.

[0157] In some embodiments, the viscosity of the hot melt adhesive at 25°C is 3800-10000 mPa·s, 5000-10000 mPa·s, or 5000-8200 mPa·s, for example, 3800 mPa·s, 4000 mPa·s, 4500 mPa·s, 5000 mPa·s, 6000 mPa·s, 7000 mPa·s, 8000 mPa·s, 9000 mPa·s, 10000 mPa·s, or any range of the above values. Therefore, the hot melt adhesive used in this application exhibits good uniformity of coating on the diaphragm side, provides good sealing for the bag-shaped diaphragm, and is less prone to delamination.

[0158] In this application, the viscosity of the hot melt adhesive is tested at 25°C using conventional methods in the art. For example, a viscosity meter is used, with an 18# rotor selected and the test performed at 70 rpm at 25°C.

[0159] In some embodiments, the two opposite sides of the bag-shaped diaphragm are sealed with the hot melt adhesive.

[0160] Therefore, the negative electrode and / or positive electrode can be confined within the pouch-shaped separator, reducing the migration of dead lithium from the pulverized negative electrode to the positive electrode and improving the safety performance of the battery cell. In particular, confining the negative electrode within the pouch-shaped separator helps to suppress the sliding misalignment of the negative electrode relative to the separator in the stacked battery cell.

[0161] In some embodiments, the three sides of the bag-shaped diaphragm are sealed with the hot melt adhesive.

[0162] This reduces the migration of dead lithium from the negative electrode to the positive electrode, thus improving the safety performance of the battery cell. Furthermore, confining the negative electrode within the pouch-shaped separator helps suppress the sliding misalignment of the negative electrode relative to the separator in the stacked battery cell.

[0163] In some embodiments, the hot melt adhesive is distributed along the length of the side of the bag-shaped diaphragm, the length of the hot melt adhesive distribution being equal to the length of the side of the bag-shaped diaphragm, and the width of the hot melt adhesive distribution being 1-8 mm or 1.5-5 mm, for example, 1 mm, 1.5 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, or any range of the above values; the width direction of the hot melt adhesive distribution is perpendicular to the length direction of the hot melt adhesive distribution. As an example, the above length and width directions can be as shown in Figure 7.

[0164] This allows the battery cells to maintain a high energy density while improving the sealing of the bag-shaped separator side, reducing the migration of dead lithium from the negative electrode to the positive electrode, and thus improving the safety performance of the battery cells.

[0165] In some embodiments, the diaphragm includes a base layer, wherein the base layer comprises one or more polyolefin materials; or, the base layer comprises one or more polyethylene materials and polypropylene materials.

[0166] In some embodiments, the diaphragm further includes functional layers located on at least one side of the substrate layer, each of the functional layers independently comprising one or more of a ceramic material, a polycarbosilane material, a polyvinyl chloride material, and a polycarbonate material.

[0167] Therefore, not limited to the base layer and functional layer materials mentioned above, the hot melt adhesive of this application can be used to bond and seal common base layer or functional layer materials in the art to form a bag-shaped diaphragm.

[0168] In some implementations, the battery cell is a stacked battery cell.

[0169] Another embodiment of this application provides a method for preparing a battery cell, comprising the following steps:

[0170] Place one of the negative and positive electrode plates inside the bag-shaped diaphragm, and the other outside the bag-shaped diaphragm, aligning them; or,

[0171] Place the negative electrode and the positive electrode in two adjacent bag-shaped diaphragms respectively, and align them;

[0172] The bag-shaped diaphragm is manufactured by either method one or method two as follows:

[0173] Method 1 includes the following steps:

[0174] The raw material is cut into diaphragms; hot melt adhesive is applied to either side or opposite sides of the diaphragm before or after cutting, and then cooled.

[0175] The diaphragm is folded along the length of the side coated with hot melt adhesive and then heat-sealed to obtain a bag-shaped diaphragm.

[0176] The second method includes the following steps:

[0177] The raw material is cut into diaphragms; hot melt adhesive is applied to three sides of the diaphragms before or after cutting, and then cooled.

[0178] Three sides of multiple diaphragms of the same size, coated with the hot melt adhesive, are heat-sealed to obtain a bag-shaped diaphragm.

[0179] Furthermore, the hot melt adhesive includes C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 olefin ester copolymers, C 2- 6. Polyolefins and polymers, wherein the monomers of the polymers include monomer 1 and monomer 2 as follows;

[0180] Monomer 1: C 1-6 Carboxylic acid C 2-6 Olefin esters;

[0181] Monomer 2: C 3-6 Acetic acid C 2-6 Alcohol esters.

[0182] This application employs hot melt adhesive to effectively seal the sides of the pouch-shaped separator, preventing it from easily separating during battery cell charge-discharge cycles. This confines the negative electrode and / or positive electrode within the pouch-shaped separator, reducing the migration of pulverized dead lithium from the negative electrode to the positive electrode, suppressing micro-short circuits and overcharging in the battery cell, and improving the battery cell's safety performance. Furthermore, the hot melt adhesive remains stable during battery cell charge-discharge cycles with virtually no impurity leakage, reducing the negative impact of impurities on the battery cell. Additionally, the pouch-shaped separator restricts the movement of the negative electrode, suppressing slippage and misalignment between the negative electrode and the separator, thus resolving the resulting battery cell short circuit problem.

[0183] In some embodiments, the hot melt adhesive is applied along the length of the diaphragm side, the length of the hot melt adhesive application being equal to the length of the diaphragm side, and the width of the hot melt adhesive application being 1-8 mm or 1.5-5 mm, for example, 1 mm, 1.5 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm or any range of the above values; the width direction of the hot melt adhesive application is perpendicular to the length direction of the hot melt adhesive application.

[0184] In some embodiments, the hot melt adhesive is applied at 45-110°C, 45-90°C, or 45-80°C, for example, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, or any range of the above values; and / or,

[0185] The heat-sealing temperature is 45-110℃, 45-90℃, or 45-80℃, for example, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, or any range of the above values; and / or,

[0186] The heat sealing time is 0.5–10 minutes, for example, 0.5 minutes, 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes or any range of the above values.

[0187] In some embodiments, the monomer of the polymer further includes monomer 3 as follows;

[0188] Monomer 3:

[0189] Among them, R1 is selected from C 2-6 Alkenyl group, R2 is selected from C 7-10 Alkyl, hydroxyl C 1-6 Any one of alkyl and isobornyl.

[0190] In some embodiments, the hot melt adhesive further includes a viscosity modifier, which includes one or more of rosin and paraffin.

[0191] In some embodiments, the hot melt adhesive comprises 51-63 parts by weight (e.g., 51 parts by weight, 53 parts by weight, 55 parts by weight, 56 parts by weight, 58 parts by weight, 59 parts by weight, 60 parts by weight, 61 parts by weight, 63 parts by weight, or any range of the above values) of the C. 2-6 Olefin-C 1-6 Carboxylic acid C 2-6The olefin ester copolymer, 6-15 parts by weight (e.g., 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 12 parts by weight, 13 parts by weight, 15 parts by weight, or any range of the above values) of the C 2-6 The polymer comprising 15-41 parts by weight (e.g., 15 parts by weight, 18 parts by weight, 20 parts by weight, 22 parts by weight, 25 parts by weight, 27 parts by weight, 30 parts by weight, 32 parts by weight, 34 parts by weight, 35 parts by weight, 37 parts by weight, 38 parts by weight, 40 parts by weight, 41 parts by weight, or any range of the above values).

[0192] In some embodiments, the molar ratio of monomer 1 to monomer 2 is 5:5 to 8:2, for example, 5:5, 6:4, 7:3, 8:2 or any range of the above values.

[0193] In some embodiments, the molar ratio of monomer 3 to the sum of monomer 1 and monomer 2 is 1:9 to 5:5, for example, 1:9, 2:8, 3:7, 4:6, 5:5 or any range of the above values.

[0194] In some embodiments, the hot melt adhesive further includes 6-8 parts by weight (e.g., 6 parts by weight, 6.5 parts by weight, 7 parts by weight, 7.5 parts by weight, 8 parts by weight, or any range of the above values) of the viscosity modifier.

[0195] In some embodiments, the weight ratio of the rosin and the paraffin in the viscosity modifier is 1:4 to 1:1, for example, 1:1, 1:2, 1:3, 1:4 or any range of the above values.

[0196] In some embodiments, the battery cell obtained is the battery cell of the first aspect of this application.

[0197] In some embodiments, this application does not have a particular limitation on the type of diaphragm, and any known porous diaphragm with good chemical and mechanical stability can be selected.

[0198] As an example, the main material of the separator can be selected from at least one of polyethylene, polypropylene, polyvinylidene fluoride, ceramic, polycarbosilane, polyvinyl chloride, and polycarbonate. The separator can 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 can be the same or different, without particular limitation. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be applied to the surface of the separator.

[0199]

Positive Electrode

[0200] In some embodiments, the positive electrode can be a positive electrode sheet, which may include a positive current collector and a positive active material disposed on at least one surface of the positive current collector.

[0201] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material is disposed on either or both of the two opposite surfaces of the positive current collector.

[0202] As an example, the positive current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0203] As an example, the positive electrode active material may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium phosphate may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Examples of lithium transition metal oxide may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Modified compounds refer to substances obtained by modification methods such as doping or coating based on the above-mentioned substances.

[0204] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of cathode materials in this application, the molar Li content refers to the initial state of the material, i.e., the state before feeding. When the cathode material is applied to the battery system, the molar Li content changes after charge-discharge cycles.

[0205] In the examples of cathode materials in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0206] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0207] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0208] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0209] [Negative electrode plate]

[0210] In some embodiments, the negative electrode can be a negative electrode sheet, and the negative electrode sheet can include a negative current collector.

[0211] As an example, the negative electrode current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material substrate and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0212] As an example, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material disposed on at least one surface of the negative electrode current collector.

[0213] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0214] As an example, the negative electrode active material may be a negative electrode active material known in the art for use in lithium metal battery cells or lithium-sulfur battery cells. As an example, the negative electrode active material may include at least one of the following materials: lithium or lithium alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for lithium metal battery cells or lithium-sulfur battery cells may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0215] As an example, negative electrode active materials can be filled or / and deposited within the negative electrode current collector.

[0216] In some embodiments, the positive current collector can be made of aluminum, and the negative current collector can be made of copper.

[0217] In some embodiments, the negative electrode sheet can be prepared by coating the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, onto the negative electrode current collector, and then obtaining the negative electrode sheet after processes such as cold pressing.

[0218] Electrolytes

[0219] In some embodiments, the battery cell also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. The electrolyte can be liquid, gel, or solid.

[0220] Liquid electrolytes include electrolyte salts and solvents.

[0221] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0222] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, 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. The solvent may also be an ether solvent. Ether solvents may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0223] 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 additives that can improve certain properties of the battery cell, such as additives that improve the overcharge / fast charge performance of the battery cell, additives that improve the high-temperature performance of the battery cell, and additives that improve the low-temperature performance of the battery cell.

[0224] The gel electrolyte includes a polymer as a backbone network and can be used in conjunction with an ionic liquid-lithium salt.

[0225] Solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0226] As an example, the polymers of polymeric solid electrolytes may include polyethers (polyoxyethylene), polysiloxanes, polycarbonates, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquids, cellulose, etc.

[0227] As an example, inorganic solid electrolytes can be one or more of the following: oxide solid electrolytes (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON thin film), sulfide solid electrolytes (crystalline lithium superconducting ion conductor (lithium-germanium-phosphorus-sulfur, sulfosilium-germanium), amorphous sulfides), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0228] As an example, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to polymer solid electrolytes.

[0229] In some implementations, the positive electrode, negative electrode, and bag-shaped diaphragm can be fabricated into an electrode assembly using a winding or stacking process.

[0230] [Structure of the Electrode Assembly]

[0231] The electrode assembly can be a wound structure, a stacked structure, or a hybrid structure of wound and stacked.

[0232] In some implementations, the electrode assembly is a wound structure. The positive and negative electrode sheets are wound into a wound structure.

[0233] In some implementations, the electrode assembly is a stacked structure.

[0234] As an example, multiple positive and negative electrodes can be set, and multiple positive and multiple negative electrodes can be stacked alternately.

[0235] As an example, multiple positive electrode plates can be provided, and negative electrode plates can be folded to form multiple stacked folded segments, with a positive electrode plate sandwiched between adjacent folded segments.

[0236] As an example, both the positive and negative electrode plates are folded to form multiple stacked folded segments.

[0237] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0238] As an example, the separators can be continuously arranged, either by folding or rolling between any adjacent positive or negative electrode plates.

[0239] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0240] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0241]

shell

[0242] In some embodiments, the battery cell may include a casing. The casing may be a steel casing, an aluminum casing, a plastic casing (such as a polypropylene casing), a composite metal casing (such as a copper-aluminum composite casing), or an aluminum-plastic film, etc. In some embodiments, the casing may be a sealed structure or a non-sealed structure. As an example, when the casing is a non-sealed structure, the casing serves to protect the electrode assembly, and a sealing bag is included between the casing and the electrode assembly to encapsulate the electrode assembly and electrolyte. Specifically, the sealing bag may be a bag-shaped insulating component or an aluminum-plastic film. When the casing is a sealed structure, it is used to encapsulate components such as the electrode assembly and electrolyte.

[0243] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries. This application does not have any particular limitations.

[0244] In some embodiments, the housing includes an end cap and a housing, the housing having an opening, and the end cap covering the opening. The housing may have one or more openings. The end cap may also have one or more.

[0245] Electrode terminals

[0246] In some embodiments, at least one electrode terminal is provided on the housing, and the electrode terminal is electrically connected to the tab. The electrode terminal can be directly connected to the tab, or it can be indirectly connected to the tab through a current collector. The electrode terminal can be provided on the end cap or on the housing.

[0247] Pressure relief mechanism

[0248] In some embodiments, a pressure relief mechanism is provided on the casing. The pressure relief mechanism is used to release the internal gas of the battery cell.

[0249] As an example, the internal pressure or temperature of a battery cell is actuated to release the internal pressure or temperature when it reaches a predetermined threshold. When the internal pressure or temperature of the battery cell reaches the predetermined threshold, the pressure relief mechanism is activated or a weak structure in the pressure relief mechanism is broken, thereby creating an opening or channel for the internal pressure or temperature to be released. The threshold design varies depending on the design requirements. The threshold may depend on the materials of one or more of the positive electrode, negative electrode, electrolyte, and separator in the battery cell.

[0250] As an example, the pressure relief mechanism can be integrally molded with the housing.

[0251] As an example, the pressure relief mechanism can also be separately installed and connected to the housing.

[0252] The term "actuation" as used in this application refers to the activation or actuation of the pressure relief mechanism to a certain state, thereby releasing the internal pressure and temperature of the battery cell. The actions of the pressure relief mechanism may include, but are not limited to: movement of components within the mechanism to form an exhaust channel, rupture, breakage, tearing, or opening of at least a portion of the mechanism, etc. When the pressure relief mechanism is activated, the high-temperature, high-pressure substances inside the battery cell are discharged as waste from the activated portion. This method allows for pressure and temperature relief of the battery cell under controllable pressure or temperature, thereby preventing potentially more serious accidents.

[0253] In some embodiments, when the housing is a non-sealed structure, the pressure relief mechanism can be configured as a through hole for venting gas inside the battery cell.

[0254] The emissions from battery cells mentioned in this application include, but are not limited to: electrolyte, dissolved or split positive and negative electrode plates, fragments of separators, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0255] [Battery Device]

[0256] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0257] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0258] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0259] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0260] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0261] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0262] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0263] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0264] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0265] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use individual battery cells, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft.

[0266] For example, Figure 1 shows a square-structured battery cell 5 as an example.

[0267] In some embodiments, referring to FIG2, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0268] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0269] Figure 3 shows a battery module 4 as an example. Referring to Figure 3, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0270] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0271] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0272] Figures 4 and 5 show a battery pack 1 as an example. Referring to Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0273] In addition, this application also provides an electrical device, which includes at least one of the battery cell, battery module, or battery pack provided in this application. The battery cell, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0274] As an electrical device, you can choose individual battery cells, battery modules, or battery packs according to your usage requirements.

[0275] Figure 6 shows an example of an electrical device. This 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 the individual battery cells, a battery pack or battery module can be used.

[0276] [Example]

[0277] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0278] Example 1

[0279] (1) Preparation of the diaphragm:

[0280] Preparation of hot melt adhesive slurry: 52 parts by mass of ethylene-vinyl acetate copolymer (number-average molecular weight 60,000-70,000, molecular weight distribution coefficient 3-4, vinyl acetate molar content in the copolymer 25%, melt index MI 200), 5.1 parts by mass of polypropylene (number-average molecular weight 80,000, molecular weight distribution coefficient 2-3), and 11.9 parts by mass of a copolymer of vinyl acetate (monomer 1) and butyl acrylate (monomer 2) (number-average molecular weight 2400, molecular weight distribution coefficient 1, molar ratio of monomer 1 to monomer 2 7:3) were dissolved in N-methyl-2-pyrrolidone at 60°C to obtain the hot melt adhesive slurry. The melting temperature of the hot melt adhesive was 80°C, and the viscosity at 25°C was 7200 mPa·s.

[0281] As shown in Figure 7, at 80°C, hot melt adhesive 7 is rolled onto one side of the polyethylene diaphragm 6 at equal intervals. The rolling direction is along the length of the diaphragm 6 to be cut, and the width of the hot melt adhesive 7 is 3 mm. After cooling, it is cut along the center line of the width of the hot melt adhesive 7 to obtain a diaphragm 6 with a width of 45 mm and a length of 102 mm. The width of the hot melt adhesive 7 on both sides of the diaphragm 6 is 1.5 mm. The diaphragm 6 is folded in half along the length direction, and the overlapping two sides are hot-pressed at 80°C for 2 minutes to obtain a bag-shaped diaphragm.

[0282] (2) Preparation of the positive electrode sheet:

[0283] Lithium nickel cobalt manganese oxide material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 98:1:1. NMP solvent was added and stirred until the system was homogeneous to obtain the positive electrode slurry. The positive electrode slurry was uniformly coated on both sides of the positive electrode current collector aluminum foil, air-dried at room temperature, and then transferred to an oven for further drying. It was then cut into 40mm*50mm rectangles to serve as the positive electrode sheet, with a positive electrode surface capacity of 3.5 mAh / cm². 2 .

[0284] (3) Preparation of negative electrode sheet:

[0285] A 50μm thick lithium foil is rolled onto one side of a 12μm thick copper foil and then cut into a 41mm*51mm rectangle to serve as a negative electrode.

[0286] (4) Preparation of electrolyte:

[0287] Take 1.51g of lithium hexafluorophosphate, add ethylene carbonate (EC) and ethyl methyl carbonate (EMC) as solvents, wherein the weight ratio of ethylene carbonate to ethyl methyl carbonate is 3:7, and stir thoroughly to form an electrolyte with a lithium hexafluorophosphate concentration of 1M.

[0288] (5) Assembly of individual battery cells:

[0289] The negative electrode is placed inside a bag-shaped separator, and the positive electrode is placed outside the bag-shaped separator and aligned and hot-pressed to form an electrode assembly. The prepared electrolyte is injected, and the aluminum-plastic film bag is vacuum hot-pressed and sealed. After standing at room temperature for at least 6 hours, a single battery cell is obtained.

[0290] The parameter differences between Examples 2-10 and Comparative Examples 1-4 and Example 1 are shown in Table 1.

[0291] Example 11

[0292] Ten individual cells from Example 1 are stacked to form a multi-layer laminated small soft pack. Among them, there are 11 negative electrode plates and 10 positive electrode plates, which are wrapped in aluminum-plastic film bags to form a laminated dry cell with a rated capacity of 1.40Ah.

[0293] Battery cell testing

[0294] (1) Electrolyte analysis of individual battery cells before and after cycling:

[0295] At an ambient temperature of 25℃, the battery cells were charged at a constant current of 0.5C to 4.3V, then charged at a constant voltage of 0.05C, allowed to stand for 10 minutes, and then discharged at a constant current of 0.5C to 2.8V, allowed to stand for 10 minutes. This charge-discharge process was repeated until the battery cells degraded to 80% SOC or completed 160 cycles. The electrolytes of the battery cells before and after charge-discharge were diluted 10 times their volume with ethyl methyl carbonate (EMC) and analyzed by gas chromatography.

[0296] Gas chromatography operating conditions: SH-POLARWAX-MS column (30m, 0.25mm ID, 0.25μm); helium as carrier gas; FID detector; column temperature program: 45℃ for 5 min, increase to 150℃ at 10℃ / min and hold for 10 min, then increase to 250℃ at 20℃ / min and hold for 10 min.

[0297] The chromatograms of the electrolyte dilution solution before and after charging and discharging of the battery cell in Example 1 are shown in Figures 8A-8B, respectively.

[0298] As shown in Figures 8A-8B, the hot melt adhesive used in this application for bonding bag-shaped diaphragms exhibits almost no impurities seeping into the electrolyte during cyclic charging and discharging, demonstrating good stability.

[0299] (2) Test on the migration of pulverized dead lithium in battery cells:

[0300] At an ambient temperature of 25℃, the battery cells were charged at a constant current of 0.5C to 4.3V, then charged at a constant voltage of 0.05C, allowed to stand for 10 minutes, and then discharged at a constant current of 0.5C to 2.8V, allowed to stand for 10 minutes. This charge-discharge process was repeated until the battery cells degraded to 80% SOC or completed 160 cycles. Battery cells that did not reach 160 cycles were marked. The battery cells were disassembled and the bag-shaped separator was opened to observe whether there was powdered lithium on the side of the separator.

[0301] Figure 9 shows a side view of the bag-shaped separator after cycling of the battery cell of Example 1. After cycling, the side of the separator of Example 1 was clean, and no pulverized dead lithium was found, indicating that the pulverized dead lithium was effectively isolated within the bag-shaped separator.

[0302] Figure 10 shows a side view of the bagged battery cell after cycling in Comparative Example 1. After cycling, a significant amount of pulverized dead lithium was observed on the side of the separator, indicating that the pulverized dead lithium had drifted towards the positive electrode.

[0303] (3) Overcharge test of individual battery cells:

[0304] Battery cell nominal capacity measurement: At an ambient temperature of 25℃, the battery cell is charged at a constant current of 0.1C to a voltage of 4.3V, then charged at a constant voltage to 0.05C, left to stand for 10 minutes, and then discharged at a constant current of 0.1C to a voltage of 2.8V. The charging capacity during this process is the nominal capacity of the battery cell.

[0305] Overcharge test: Charge the battery cell at a constant current of 0.5C to 4.3V, then charge at a constant voltage of 0.05C, let it rest for 10 minutes, and discharge at a constant current of 0.5C to 2.8V, let it rest for 10 minutes. Repeat the above charge and discharge process until the battery cell decays to 80% SOC or completes 160 cycles, and test the charge and discharge curve. If the charging capacity of the battery cell exceeds the nominal capacity of the battery cell, or if current fluctuations occur in the constant voltage charging stage of the charge and discharge curve and the cell cannot normally transition to the discharge stage, it is considered that a micro-short circuit or overcharge has occurred.

[0306] Figure 11 shows the charging / discharging capacity as a function of the number of cycles, plotted based on the charge / discharge curves. It can be seen that the battery cell in Example 1 did not experience overcharging, while the battery cell in Comparative Example 1 did.

[0307] (4) Energy density test of individual battery cells:

[0308] At an ambient temperature of 25℃, charge the battery cell at a constant current of 0.5C to a voltage of 4.3V, then charge at a constant voltage of 0.05C, let it stand for 10 minutes, and then discharge at a constant current of 0.5C to a voltage of 2.8V, and let it stand for 10 minutes. Record the discharge capacity A0 and the discharge plateau voltage V at this time. Weigh the battery cell m0 (generally excluding the electrode terminals and the insulating film outside the casing). The energy density of the battery cell VED = (A0 × V) / m0, in Wh / kg.

[0309] The results are shown in Table 2.

[0310] Table 2 Test results of Examples 1-10 and Comparative Examples 1-4

[0311] As shown in Table 2:

[0312] In the battery cells of Examples 1-8 of this application, no pulverization or dead lithium was observed on the side of the pouch separator after cycling, and no overcharging problem was observed. Among them, the cycle performance of the battery cells of Examples 1-4 and 6-8 was significantly improved.

[0313] Comparative Example 1 did not use hot melt adhesive to bond the separator. After cycling, its battery cells exhibited significant lithium pulverization on the separator sides, resulting in severe overcharging and very poor cycle performance. Comparative Example 2 used hot melt adhesive with an excessively high melting temperature, exceeding the separator's tolerance limit, causing severe shrinkage and deformation, making it impossible to manufacture battery cells normally. Comparative Example 3 used hot melt adhesive with high viscosity, resulting in uneven coating thickness deviations of up to 70% on both sides of the separator, leading to poor adhesion on one side. After cycling, its battery cells exhibited significant lithium pulverization on the separator sides, resulting in severe overcharging and poor cycle performance. Comparative Example 4 used hot melt adhesive with high viscosity, resulting in uneven coating thickness deviations of up to 30% on both sides of the separator, causing the bagged separator sides to open during mid-cycle. After cycling, its battery cells exhibited significant lithium pulverization on the separator sides, resulting in substantial overcharging and poor cycle performance.

[0314] Compared with Comparative Examples 1 and 3-4, the battery cells of Examples 9-10 of this application exhibit less pulverized dead lithium and less overcharge after cycling. The cycle performance of the battery cells of Examples 9-10 of this application is also better than that of Comparative Examples 1 and 3-4.

[0315] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, comprising a positive electrode, a negative electrode, and a separator, wherein the separator is bag-shaped, and at least one side of the bag-shaped separator is sealed with hot melt adhesive; One of the negative electrode and the positive electrode is located inside the bag-shaped diaphragm, and the other is located outside the bag-shaped diaphragm; or, the negative electrode and the positive electrode are respectively located inside two adjacent bag-shaped diaphragms. in, The hot melt adhesive includes C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 olefin ester copolymers, C 2-6 Polyolefins and polymers, wherein the monomers of the polymers include monomer 1 and monomer 2 as follows; Monomer 1: C 1-6 Carboxylic acid C 2-6 Olefin esters; Monomer 2: C 3-6 Acetic acid C 2-6 Alcohol esters.

2. The battery cell according to claim 1, wherein, The hot melt adhesive includes: The C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 51-63 parts by weight of olefin ester copolymer; The C 2-6 6-15 parts by weight of polyolefin; The polymer is 15-41 parts by weight.

3. The battery cell according to claim 1 or 2, wherein, The molar ratio of monomer 1 to monomer 2 is 5:5-8:

2.

4. The battery cell according to any one of claims 1 to 3, characterized in that... One or more of the following: The C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 Olefin ester copolymers are C 2-4 Olefin-C 1-4 Carboxylic acid C 2-4 Olefin ester copolymers; The C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 Olefin ester copolymers include one or more of ethylene-vinyl acetate copolymers, propylene-propylene acetate copolymers, and propylene-propylene propionate copolymers; The C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 The number-average molecular weight of olefin ester copolymers is 50,000–100,000; The C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 C in olefin ester copolymers 1-6 Carboxylic acid C 2-6 The olefin molar content is 20%-30%.

5. The battery cell according to any one of claims 1 to 4, characterized in that... One or more of the following: The hot melt adhesive comprises 8-15 parts by weight of the C. 2-6 Polyolefins; The C 2-6 Polyolefins are C 2-4 Polyolefins; The C 2-6 Polyolefins include one or more of polyethylene, polypropylene, and polybutene; The C 2-6 The number average molecular weight of polyolefins ranges from 30,000 to 120,000.

6. The battery cell according to any one of claims 1 to 5, characterized in that... One or more of the following: The hot melt adhesive comprises 22-41 parts by weight of the polymer; The monomer 1 is C 1-4 Carboxylic acid C 2-4 Olefin esters; The monomer 1 is selected from any one of vinyl acetate, vinyl propionate, and vinyl butyrate; The monomer 2 is C 3-4 Acetic acid C 2-4 Alcohol esters; The monomer 2 is selected from any one of butyl acrylate, methyl acrylate, ethyl acrylate, ethyl butyrate, and butyl butyrate.

7. The battery cell according to any one of claims 1 to 6, wherein, The monomers of the polymer also include the following monomer 3; Monomer 3: Among them, R1 is selected from C 2-6 Alkenyl group, R2 is selected from C 7-10 Alkyl, hydroxyl C 1-6 Any one of alkyl and isobornyl.

8. The battery cell according to claim 7, wherein, The molar ratio of monomer 3 to the total of monomer 1 and monomer 2 is 1:9-5:

5.

9. The battery cell according to claim 7 or 8, wherein, R1 is selected from C 2-4 Olefins; And / or, R2 is selected from C 7-8 Alkyl, hydroxyl C 1-4 Any one of alkyl and isobornyl.

10. The battery cell according to any one of claims 7 to 9, wherein, The monomer 3 includes one or more of isooctyl acrylate, hydroxyethyl acrylate, and isobornyl acrylate.

11. The battery cell according to any one of claims 1 to 10, wherein, The hot melt adhesive also includes 6-8 parts by weight of viscosity modifier.

12. The battery cell according to claim 11, wherein, The viscosity modifier includes one or more of rosin and paraffin.

13. The battery cell according to claim 12, wherein, The viscosity modifier comprises rosin and paraffin wax, wherein the weight ratio of the rosin to the paraffin wax is 1:4 to 1:

1.

14. The battery cell according to any one of claims 1 to 13, wherein, The hot melt adhesive has a melting temperature of 45-110℃, 45-90℃, or 45-80℃; and / or, The viscosity of the hot melt adhesive at 25°C is 3800-10000 mPa·s, 5000-10000 mPa·s, or 5000-8200 mPa·s.

15. The battery cell according to any one of claims 1 to 14, wherein, The two opposite sides of the bag-shaped diaphragm are sealed with the hot melt adhesive; or... The three sides of the bag-shaped diaphragm are sealed with the hot melt adhesive.

16. The battery cell according to any one of claims 1 to 15, wherein, The hot melt adhesive is distributed along the length of the side of the bag-shaped diaphragm, and the length of the hot melt adhesive distribution is equal to the length of the side of the bag-shaped diaphragm. The width of the hot melt adhesive distribution is 1-8 mm or 1.5-5 mm. The width direction of the hot melt adhesive distribution is perpendicular to the length direction of the hot melt adhesive distribution.

17. The battery cell according to any one of claims 1 to 16, wherein, The membrane includes a base layer, wherein the base layer comprises one or more polyolefin materials.

18. The battery cell according to claim 17, wherein, The diaphragm further includes functional layers located on at least one side of the base layer, each of which independently comprises one or more of ceramic materials, polycarbosilane materials, polyvinyl chloride materials, and polycarbonate materials.

19. The battery cell according to any one of claims 1 to 18, wherein it is a stacked battery cell.

20. A method for preparing a battery cell, comprising the following steps: Place one of the negative and positive electrode plates inside the bag-shaped diaphragm, and the other outside the bag-shaped diaphragm, aligning them; or, Place the negative electrode and the positive electrode in two adjacent bag-shaped diaphragms respectively, and align them; in, The bag-shaped diaphragm is manufactured by either method one or method two as follows: Method 1 includes the following steps: The raw material is cut into diaphragms; hot melt adhesive is applied to either side or opposite sides of the diaphragm before or after cutting, and then cooled. Fold the diaphragm along the length of the side coated with the hot melt adhesive and heat seal it to obtain a bag-shaped diaphragm; The second method includes the following steps: The raw material is cut into diaphragms; hot melt adhesive is applied to three sides of the diaphragms before or after cutting, and then cooled. Three sides of multiple diaphragms of the same size, coated with the hot melt adhesive, are heat-sealed to obtain a bag-shaped diaphragm. Furthermore, the hot melt adhesive includes C 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 olefin ester copolymers, C 2-6 Polyolefins and polymers, wherein the monomers of the polymers include monomer 1 and monomer 2 as follows; Monomer 1: C 1-6 Carboxylic acid C 2-6 Olefin esters; Monomer 2: C 3-6 Acetic acid C 2-6 Alcohol esters.

21. The method according to claim 20, wherein, The hot melt adhesive is applied along the length of the diaphragm side, the length of the hot melt adhesive application is equal to the length of the diaphragm side, and the width of the hot melt adhesive application is 1-8 mm or 1.5-5 mm; the width direction of the hot melt adhesive application is perpendicular to the length direction of the hot melt adhesive application.

22. The method according to claim 20 or 21, wherein, Apply the hot melt adhesive at 45-110℃, 45-90℃, or 45-80℃; and / or, The heat sealing temperature is 45-110℃, 45-90℃, or 45-80℃; and / or, The heat sealing time is 0.5-10 minutes.

23. The method according to any one of claims 20 to 22, wherein, The monomers of the polymer also include the following monomer 3; Monomer 3: Among them, R1 is selected from C 2-6 Alkenyl group, R2 is selected from C 7-10 Alkyl, hydroxyl C 1-6 Any one of alkyl and isobornyl.

24. The method according to any one of claims 20 to 23, wherein, The hot melt adhesive also includes a viscosity modifier, which includes one or more of rosin and paraffin.

25. The method according to any one of claims 20 to 24, characterized in that... One or more of the following: The hot melt adhesive comprises 51-63 parts by weight of the C. 2-6 Olefin-C 1-6 Carboxylic acid C 2-6 olefin ester copolymer, 6-15 parts by weight of the aforementioned C 2-6 Polyolefin and 15-41 parts by weight of the polymer; The molar ratio of monomer 1 to monomer 2 is 5:5-8:2; The molar ratio of monomer 3 to the total of monomer 1 and monomer 2 is 1:9-5:5; The hot melt adhesive also includes 6-8 parts by weight of the viscosity modifier; The weight ratio of rosin to paraffin in the viscosity modifier is 1:4 to 1:1; The obtained battery cell is the battery cell described in any one of claims 1 to 19.

26. A battery device comprising a battery cell according to any one of claims 1 to 19 or a battery cell prepared by the method according to any one of claims 20 to 25.

27. An electrical device comprising a battery cell as described in any one of claims 1 to 19 or a battery device as described in claim 26.

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