Battery cells, batteries, and power consumption devices

Abstract

The present application relates to a battery cell, a battery, and a power consuming device, the battery cell comprising an electrode assembly, the electrode assembly comprising a first polar sheet, a second polar sheet, and a separator, the first polar sheet and the second polar sheet having opposite polarities, the separator being disposed between the first polar sheet and the second polar sheet, at least one of the first polar sheet, the second polar sheet, and the separator comprising a swelling polymer, the swelling polymer satisfying 300%≦m2 / m1≦10000% and m3 / m2≦50%. Figure 1

Description

Cross-reference of related applications 【0001】 This application claims priority to the Chinese patent application filed on November 3, 2023, application number 202311457178.4, titled "Battery Cell, Battery and Power Consumption Device," the entirety of which is incorporated herein by reference. [Technical Field] 【0002】 This application relates to the battery technology field, and more specifically to battery cells, batteries, and power consumption devices. [Background technology] 【0003】 Due to their characteristics such as high capacity and long lifespan, battery cells are widely used in electronic devices such as mobile phones, laptop computers, battery-powered cars, electric vehicles, electric aircraft, electric boats, electric toy cars, electric toy boats, electric toy aircraft, and power tools. 【0004】 As the range of battery applications expands, the requirements for battery cell performance are gradually becoming more stringent. While optimization and improvements are generally made to improve battery cell performance, the reliability and cycle characteristics of battery cells remain poor. [Overview of the Initiative] 【0005】 This invention was made in view of the above-mentioned problems, and its purpose is to provide a battery cell, a battery, and a power consumption device. 【0006】 According to a first aspect, the present application provides a battery cell including an electrode assembly, the electrode assembly including a first polarity sheet, a second polarity sheet and a separator, the polarities of the first polarity sheet and the second polarity sheet being opposite, the separator being placed between the first polarity sheet and the second polarity sheet, and at least one of the first polarity sheet, the second polarity sheet and the separator containing a swelling polymer, the swelling polymer satisfying 300% ≤ m² / m¹ ≤ 10000% and m³ / m² ≤ 50%. Here, A gel film is manufactured from a swollen polymer, and the mass of the gel film is m1 The units are g and The gel film has a width of 10 mm, a length of 10 mm, and a thickness of 1 mm. The gel film was added to an excess amount of dimethyl carbonate (DMC) and left to stand at 25°C for 7 days to obtain a first swollen gel film, the mass of which was m2 The units are g is, The first swollen gel film was left standing at 25°C for 7 days in an atmosphere with a humidity of 20% or less to obtain a dry gel film, and the mass of the dry gel film was m³ The units are It is g. 【0007】 As a result, when the swelling polymer in the embodiment of the present invention satisfies 300% ≤ m² / m¹ ≤ 10000% and m³ / m² ≤ 50%, the electrolyte can be trapped within the swelling polymer by physical adsorption due to its own liquid containment and liquid release capabilities. The electrolyte is trapped on the surface of the active material particles, forming a containment liquid release point and releasing the electrolyte into the electrode assembly, improving the electrolyte shortage phenomenon. During the cycle charging and discharging process of the battery cell, the electrolyte is continuously moistened on the active material surface and protects the active material interface, as well as enabling smooth transport of active ions. This establishes interface protection, reduces side reactions at the solid-liquid interface, and improves the high-temperature storage performance, reliability of use, and cycle characteristics of the battery cell. 【0008】 In some embodiments, 500% ≤ m2 / m1 ≤ 5000%. If the embodiments of the present application satisfy the above range, the reliability of the battery cell and its cycle characteristics can be further improved. 【0009】 In some embodiments, the swelling polymer satisfies at least two of the following conditions. 【0010】 (1) Gel film is T mA dynamic frequency sweep test is carried out at +20 °C to obtain a storage modulus G’ - loss modulus G” curve, the slope of the storage modulus G’ - loss modulus G” curve is K, 0.5 < K < 5, and Tm represents the melting temperature of the gel film. 【0011】 (2) The crystallinity of the swollen polymer measured by differential scanning calorimetry is Xc, 0 < Xc ≤ 30%, and the glass transition temperature of the swollen polymer is T g where T g ≤ 25 °C. 【0012】 (3) The elastic modulus of the gel film is E, E ≤ 1 MPa, and the elongation at break of the gel film is ε, ε ≥ 100%. 【0013】 When the embodiments of the present application satisfy the above ranges, the liquid confinement and liquid release capabilities of the swollen polymer can be improved, and the reliability in use and cycle characteristics of the battery cell can be further improved. 【0014】 In some embodiments, the gel film is added to a preset electrolyte and left standing at 25 °C for ≥ 24 h to obtain a second swollen gel film, the preset electrolyte contains dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), ethylene carbonate (EC) and lithium hexafluorophosphate (LiPF6), the masses of the dimethyl carbonate, the ethyl methyl carbonate and the ethylene carbonate are the same, and the molar amount of the lithium hexafluorophosphate (LiPF6) is 1 mol / L. 【0015】 The Shore hardness of the gel film is H a1 and the Shore hardness of the second swollen gel film is H a2 Then, the gel film and the second swollen gel film satisfy 0 ≤ H a2 / H a1 ≤ 0.5, and 0 ≤ H a2 ≤ 45, Optionally, 0 ≤ H a2 / H a1 ≤ 0.45, Furthermore, selectively, 20 ≤ H a1 The value is ≤ 100. 【0016】 As a result, the swelling polymer in the embodiment of the present invention may be provided on at least one of the first polar sheet and the second polar sheet, and the film layer of the first polar sheet has a porous structure, for example, having voids between the active material particles to form a porous structure, and the swelling polymer can be dispersed in the porous structure of the first polar sheet. On the one hand, the swelling polymer can form a network that holds liquid with the porous structure as support, improving the interfacial properties of the active material particles, achieving a liquid containment effect, improving the lithium ion transport rate, reducing interfacial side reactions of the active material layer, and improving the cycle characteristics of the battery cell. On the other hand, the swelling polymer swells upon contact with the electrolyte, reducing its mechanical strength, and can effectively adapt to the expansion deformation of the active material particles during the charge and discharge process of the battery cell, allowing it to adhere more effectively to the surface of the active material particles and reducing problems such as peeling of the solid-liquid interface due to swelling and the formation of a gel-like substance. 【0017】 In some embodiments, the swelling polymer comprises a fluoropolymer, and the fluoropolymer comprises at least one of the compounds represented by formula (AI) to formula (AIII). [ka] In equations (AI) and (AII), R 11 , R 12 , R 13 and R 14 Each independently contains 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 14At least one of these contains a fluorine atom, and if substituted, the substituent contains one or more of the following: a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, or a halogen atom. [ka] In equation (AIII), R 15 It contains a single bond, a substituted or unsubstituted C1-C3 alkyl group, and if substituted, the substituent includes one or more of the following: a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, or a halogen atom. p is selected from any positive integer between 1 and 3. 【0018】 In some embodiments, the swelling polymer comprises an ether-based polymer, and the ether-based polymer comprises a compound represented by formula (BI) and / or a compound represented by formula (BII). [ka] In equation (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 It contains substituted or unsubstituted C1-C5 alkylene groups, [ka] In equation (BII), R 24 ~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 ether group, and R 24 ~R 27 At least one of these includes a substituted or unsubstituted C1-C3 alkoxy group or ether group. 【0019】 In some embodiments, the swelling polymer comprises an ester polymer, and the ester polymer comprises compounds from formula (CI) to formula (CIII). [ka] In equation (CI), R 31 , R 32 and R 33 Each independently contains a hydrogen atom or a substituted or unsubstituted C1-C8 alkyl group, R 34 This includes a substituted or unsubstituted C1-C8 alkyl group, or a substituted or unsubstituted C1-C8 hydroxyalkyl group. [ka] In equation (CII), R 35 It contains a substituted or unsubstituted C2-C6 methylene group, and selectively, R 35 Each of these independently contains a substituted or unsubstituted C2-C4 methylene group, [ka] In equation (CIII), R 36 , R 37 and R 38 Each independently contains a hydrogen atom or a substituted or unsubstituted C1-C8 alkyl group, R 39 It contains a substituted or unsubstituted C1-C8 alkyl group, Selectively, R 36 , R 37 and R 38 Each of these independently contains a hydrogen atom and a substituted or unsubstituted C1-C4 alkyl group. 【0020】 In some embodiments, the swelling polymer comprises an aldehyde ketone polymer, and the aldehyde ketone polymer comprises a compound represented by formula (DI) and / or a compound represented by formula (DII). [ka] In equation (DI), R 41 R contains a single bond, a substituted or unsubstituted C1-C6 methylene group, 42 It contains a hydrogen atom, a substituted or unsubstituted C1-C6 alkyl group, [ka] In equation (DII), R 43 ~R 46 Each of these independently comprises 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, and each of r and s is independently selected from integers between 0 and 5, and at least one of r and s is selected from any positive integer. 【0021】 In some embodiments, the first polarity sheet includes a current collector and a film layer provided on at least one surface of the current collector, the film layer comprising a swollen polymer and active material particles. 【0022】 In some embodiments, the film layer comprises a polymer layer containing a swollen polymer and an active material layer containing active material particles, wherein the active material layer is provided on at least one surface of the current collector and the polymer layer is provided on the surface of the active material layer opposite to the current collector. 【0023】 In some embodiments, there are multiple active material particles, with a void between two adjacent active material particles, and the swollen polymer is distributed within the void. 【0024】 In some embodiments, the separator includes a substrate and a coating layer provided on at least one surface of the substrate. 【0025】 In some embodiments, the swollen polymer is distributed in the voids of the substrate. 【0026】 In some embodiments, the swollen polymer is distributed within the coating layer. 【0027】 In some embodiments, the swollen polymer is provided on the surface opposite to the substrate of the coating layer. 【0028】 In some embodiments, the battery cell further includes a liquid electrolyte, which is located within the electrode assembly. 【0029】 In some embodiments, the battery cell is (m / ρ) / V 総孔 Satisfying ≥80%, V 総孔 This indicates the numerical value of the void volume of the electrode assembly, in units of mL. m is the numerical difference between the mass of the battery cell before drying and the mass after drying, and its unit is g. ρ is a numerical value representing the density of the liquid electrolyte, and its unit is g / mL. 【0030】 As a result, when the battery cell of the embodiment of the present invention satisfies the above conditions, most of the liquid electrolyte is located within the void structure of the electrode assembly, meaning that the electrode assembly itself has good liquid absorption and liquid retention capabilities, which is advantageous for the transport of active ions and improves the dynamic characteristics of the battery cell. Some of the liquid electrolyte can be dispersed in the swelling polymer, and although liquid release occurs during the cycle charge-discharge process of the battery cell, the amount of liquid released is relatively small, so the liquid electrolyte is less likely to flow out of the electrode assembly, and the wetting of the electrolyte to the electrode assembly becomes more uniform, thereby improving the cycle characteristics of the battery cell. 【0031】 In some embodiments, the battery cell is Satisfying 0 ≤ y / Ah ≤ 15%, y represents the volume of free electrolyte in the battery cell, and its unit is mL. Ah indicates the nominal capacity of a battery cell, and the unit is Ah. 【0032】 As a result, when the battery cell of the embodiment of the present invention satisfies the above conditions, the amount of free electrolyte in the battery cell is extremely low, and furthermore, the battery cell contains virtually no free electrolyte, thereby significantly improving the reliability of use and cycle characteristics of the battery cell. 【0033】 In some embodiments, the battery cell is 0 ≤ y / V 総孔 Satisfying ≤15%, y represents the volume of free electrolyte in the battery cell, and its unit is mL. V 総孔 This indicates the numerical value of the void volume of the electrode assembly, in units of mL. 【0034】 As a result, when the battery cell of the embodiment of the present invention satisfies the above conditions, the amount of free electrolyte in the battery cell is extremely low, and furthermore, the battery cell contains virtually no free electrolyte, thereby significantly improving the reliability of use and cycle characteristics of the battery cell. In some embodiments, after the battery cell undergoes a linear sweep vibration test, it is charged to a 100% state of charge (SOC), a hole is drilled in the battery cell, and the hole is placed at the lowest vertical position. The volume of liquid electrolyte flowing out of the battery cell is recorded as M1, where 0 mL ≤ M1 ≤ 0.5 mL, and selectively, M1 is 0 mL. Here, The vibration direction in the linear sweep vibration test is simple vertical harmonic motion. The vibration frequency of the linear sweep vibration test is 10Hz to 55Hz. The maximum acceleration in the linear sweep vibration test is 30 m / s². 2 And, The number of sweep cycles in the linear sweep vibration test was 10. The vibration duration for the linear sweep vibration test is 3 hours. 【0035】 As a result, when the battery cell of the embodiment of the present invention satisfies the above conditions, the amount of free electrolyte in the battery cell is extremely low, and furthermore, the battery cell contains virtually no free electrolyte, thereby significantly improving the reliability of use and cycle characteristics of the battery cell. 【0036】 In some embodiments, after the battery cell undergoes a linear sweep vibration test, the electrode assembly is removed, and after a pressure test, the volume of electrolyte flowing out of the electrode assembly is recorded as M2, where 0 mL ≤ M2 ≤ 0.5 mL, and selectively, M2 is 0 mL. Here, The direction of pressure applied during the pressure test is perpendicular to the thickness direction of the electrode assembly. Regarding the degree of pressure applied in the pressure test, the applied force was 0.35 MPa. 【0037】 As a result, when the battery cell of the embodiment of the present invention satisfies the above conditions, the battery cell will have an extremely low content of free electrolyte inside after being pressed, and moreover, it will contain virtually no free electrolyte, thereby significantly improving the reliability and cycle characteristics of the battery cell. 【0038】 According to a second aspect, the present application provides a battery including a battery cell of any embodiment of the first aspect of the present application. 【0039】 According to a third aspect, the present application provides a power consumption device including a battery according to any embodiment of the second aspect of the present application. [Brief explanation of the drawing] 【0040】 To more clearly explain the technical solutions in the embodiments of this application, the necessary drawings for the embodiments are briefly described below. It should be understood that the drawings shown below represent only a few embodiments of this application, and those skilled in the art can obtain further drawings based on these drawings without requiring any creative effort. 【0041】 [Figure 1] This is a schematic diagram of one embodiment of the battery cell of the present invention. [Figure 2] Figure 1 is a schematic exploded view of an embodiment of the battery cell shown. [Figure 3] This is a schematic diagram of one embodiment of the battery module of the present invention. [Figure 4] This is a schematic diagram of one embodiment of the battery pack of the present invention. [Figure 5] Figure 4 is a schematic exploded view of an embodiment of the battery pack shown. [Figure 6] This is a schematic diagram of one embodiment of a power consumption device that includes the battery cell of the present invention as a power source. 【0042】 The drawings are not drawn according to actual proportions. [Explanation of symbols] 【0043】 1 Battery pack, 2 Upper housing, 3 Lower housing, 4 Battery module, 5 Battery cell, 51 Housing, 52 Electrode assembly, 53 Cover plate, 6 Power consumption device [Modes for carrying out the invention] 【0044】 The following describes in detail embodiments specifically disclosing the battery cell, battery, and power consumption device of the present application, with reference to the drawings as appropriate. However, unnecessary details may be omitted. For example, detailed explanations of well-known matters and redundant explanations of structures that are actually the same may be omitted. This is to avoid making the following explanation unnecessarily long and to make it easily understandable to those skilled in the art. The drawings and the following explanation are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the topics described in the claims. 【0045】 The “range” disclosed in this application is limited in the form of a lower limit and an upper limit, and a given range is limited by selecting one lower limit and one upper limit, which define the boundary of a particular range. The range thus limited may or may not include the endpoints, and any combination is possible, that is, any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 can also be assumed. Furthermore, if 1 and 2 are listed as the minimum range values ​​and 3, 4, and 5 are listed as the maximum range values, then the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 can all be assumed. In this application, unless otherwise specified, the numerical range “a-b” represents an abbreviated expression for any combination of real numbers a-b, where a and b are both real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0 to 5" have already been listed in this specification, and "0 to 5" is simply an abbreviated representation of combinations of these numbers. Also, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that this parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. 【0046】 Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical inventions. 【0047】 Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical concepts. 【0048】 All steps of this application may be performed sequentially or randomly unless otherwise specified, preferably in order. For example, if the method includes steps (a) and (b), it indicates that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, if the method further includes step (c), it means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), and so on. 【0049】 A battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator. The separator is placed between the positive and negative electrode sheets and primarily serves to prevent short circuits between them, while also allowing active ions to pass freely to form a circuit. 【0050】 During the cycle charging and discharging process of a battery cell, active ions are inserted into or removed from the active material, which can cause changes in the volume of the electrode assembly (e.g., expansion deformation). This can cause the electrolyte that has been wetting the electrode assembly to be constantly pushed out, and it is possible that not all of the pushed-out electrolyte is absorbed into the electrode assembly. This can lead to an electrolyte bridging phenomenon within the electrode assembly, and because the active material cannot be sufficiently wetted by the electrolyte bridging, there is a localized shortage of electrolyte in the active material. This prevents cycle charging and discharging in that region, causing a rapid deterioration of dynamic characteristics, leading to metal deposition at the interface and increasing the risk of dendrite formation. As dendrites grow, they may penetrate the separator and cause a short circuit between the positive and negative electrode sheets, thus degrading the reliability and cycle characteristics of the battery cell. 【0051】 In view of the above problems, the present invention provides a battery cell to which a swelling polymer is added to the electrode assembly. After contact with the electrolyte, the swelling polymer can trap the electrolyte between polymer molecular chains by physical adsorption and release the electrolyte into the electrode assembly, thereby improving the phenomenon of electrolyte depletion and reducing side reactions at the solid-liquid interface, and improving the reliability and cycle characteristics of the battery cell. The technical solution of the present invention will be described in detail below. 【0052】 battery cell According to a first aspect, the present invention provides a battery cell including an electrode assembly, the electrode assembly including a first polar sheet, a second polar sheet and a separator, wherein the polarities of the first polar sheet and the second polar sheet are opposite, the separator is placed between the first polar sheet and the second polar sheet, and at least one of the first polar sheet, the second polar sheet and the separator includes a swelling polymer. Here, A gel film is manufactured from a swollen polymer, and the mass of the gel film is m1 The units are g and The gel film has a width of 10 mm, a length of 10 mm, and a thickness of 1 mm. The gel film was added to an excess amount of dimethyl carbonate (DMC) and left to stand at 25°C for 7 days to obtain a first swollen gel film, the mass of which was m2 The units are g is, The first swollen gel film was left standing at 25°C for 7 days in an atmosphere with a humidity of 20% or less to obtain a dry gel film, and the mass of the dry gel film was m³ The units are g is, The swelling polymer satisfies the following conditions: 300% ≤ m² / m¹ ≤ 10000% and m³ / m² ≤ 50%. 【0053】 In embodiments of the present invention, the swelling polymer comprises multiple materials, for example, a polymer that is solid at room temperature (e.g., 0-45°C) or a polymer that is liquid at room temperature, and different forms of polymers can be manufactured into gel films in different ways. 【0054】 Specifically, for a polymer that is solid at room temperature and can be dissolved in a solvent, for example, 10 g of the polymer is dissolved in 90 g of N-methylpyrrolidone (NMP), stirred at 1200 rpm for 2 hours, and then dried at 130°C for ≥8 hours to obtain a polymer film, and a polymer film with a width of 10 mm, a length of 10 mm, and a thickness of 1 mm is used as a gel film. Dissolution is the process of mixing a solute and a solvent to form a homogeneous phase, and the ability to dissolve a polymer in a solvent can generally be understood as the solubility of the polymer in the solvent being greater than 10 g. 【0055】 For a polymer that is solid at room temperature, and which is basically insoluble in solvent, take 10g of the polymer and (melting point T m The polymer is pressed into a 1mm thick solid polymer film at (T20℃). In particular, for polymers that do not dissolve or melt, an appropriate softening temperature can be selected between Tg and Tb (Tb is the polymer decomposition temperature) for processing. The specific pressing process is as follows: The polymer is vacuum dried at 80℃ for 12 hours. After drying, the polymer is hot-pressed into thin sheets using a vulcanizing press, with the hot-press temperature set to (T m Set the temperature to +20°C and the rolling thickness to 1-2m m The rolling time is 2 minutes, and the pressure is 8 MPa. After rolling for 2 minutes, the sample is removed and cold-pressed in another vulcanizing press of the same type at a cold-pressing pressure of 10 MPa. A 10 cm x 10 cm square mold is used to obtain a gel film of a fixed size. When a polymer is said to be insoluble in a solvent, it can generally be understood that the polymer is poorly soluble in the solvent, and its solubility in the solvent is less than 0.01 g. 【0056】 For a liquid polymer at room temperature, an appropriate amount of sample is taken and dried for ≥8 hours at the boiling point of a solvent such as NMP to obtain a polymer film. The thickness of the polymer film is related to the solid content of the liquid plus the total height of the liquid before drying. A liquid with a solid content of 50% can be prepared, poured into a solid container to a height of 2 mm, and after drying, a gel film of 2 mm × 50% = 1 mm is obtained. 【0057】 The gel film is added to an excess amount of dimethyl carbonate (DMC (mass ratio of gel film to DMC: 1:100)). An excess amount means that even after adding the gel film to dimethyl carbonate (DMC) and letting it stand at 25°C for 7 days to obtain the first swollen gel film, it still contains free dimethyl carbonate (DMC). 【0058】 The gel film is swellable, meaning it can absorb DMC in the DMC and undergo volume expansion. m2 is the mass of the gel film after it has absorbed DMC, and the liquid absorption capacity of the gel film can be characterized by m2 / m1, thereby characterizing the liquid absorption capacity of the swelling polymer. Therefore, m2 / m1 can be defined as the amount of liquid absorbed by the gel film. When 300% ≤ m2 / m1 ≤ 10000%, the swelling performance of the swelling polymer is good, which is advantageous for absorbing and trapping liquid electrolytes within the swelling polymer, thus achieving liquid retention capacity. The mass of free electrolyte in the battery cell is small or even zero. As the mass of free electrolyte decreases, the risk of leakage in the battery cell and the resulting reliability of use is further reduced, improving the reliability and cycle characteristics of the battery cell. 【0059】 When the first swollen gel film is dried in a relatively dry environment (atmosphere with humidity below 20%), the solvent in the first swollen gel film is gradually released. m3 is the mass of the first swollen gel film after drying, and the liquid release capacity of the gel film can be characterized by m3 / m2, which in turn characterizes the liquid release capacity of the swollen polymer. Therefore, m3 / m2 can be defined as the amount of liquid released from the gel film. When m3 / m2 ≤ 50%, the ability of the swollen polymer to release the liquid electrolyte is good. During the cycle charge and discharge process of the battery cell, the liquid electrolyte trapped in the swollen polymer can be released and released into the electrode assembly. The liquid wetting performance in areas where the liquid is deficient in the electrode assembly is immediately replenished, thereby making the wetting performance of the entire electrode assembly uniform and reducing side reactions at the solid-liquid interface, improving the reliability and cycle characteristics of the battery cell. 【0060】 In the embodiment of the present invention, if the swelling polymer satisfies 300% ≤ m² / m¹ ≤ 10000% and m³ / m² ≤ 50%, the electrolyte can be trapped within the swelling polymer by physical adsorption due to its own liquid containment and release capabilities. The electrolyte is trapped on the surface of the active material particles, forming a containment liquid release point to release the electrolyte into the electrode assembly, improving the electrolyte depletion phenomenon. During the cycle charging and discharging process of the battery cell, the electrolyte is continuously moistened to the active material surface and protects the active material interface, as well as enabling smooth transport of active ions. This establishes interface protection, reduces side reactions at the solid-liquid interface, and improves the high-temperature storage performance, reliability of use, and cycle characteristics of the battery cell. 【0061】 In some embodiments, 500% ≤ m² / m¹ ≤ 5000%. When embodiments of the present application satisfy the above range, the high-temperature storage performance, operational reliability, and cycle characteristics of the battery cell can be further improved. 【0062】 Exemplarily, m2 / m1 may be 300%, 400%, 500%, 600%, 800%, 1000%, 1200%, 1400%, 1500%, 1600%, 1800%, 2000%, 2200%, 2400%, 2500%, 2600%, 2800%, 3000%, 3200%, 3300%, 3400%, 3500%, 3600%, 3700%, 3800%, 3900%, 4000%, 4200%, 4500%, 4600%, 4700%, 4800%, 4900%, 5000%, or a range consisting of any two of the above numerical values. 【0063】 Optionally, 0 < m3 / m2 ≤ 50%. Exemplarily, m3 / m2 may be 50%, 49%, 48%, 45%, 42%, 40%, 39%, 38%, 35%, 32%, 30%, 29%, 28%, 25%, 23%, 22%, 20%, 19%, 18%, 15%, 14%, 13%, 11%, 10%, 8%, 7%, 6%, 5%, 3%, 2%, 1%, or a range consisting of any two of the above numerical values. 【0064】 To further improve the liquid confinement and liquid release capabilities of the swelling polymer, the swelling polymer is further selected, for example, its physical and chemical properties are further selected, thereby selecting a swelling polymer with excellent performance. 【0065】 In some embodiments, the gel film is T m +20 °C, a dynamic frequency sweep test is performed to obtain a storage modulus G'-loss modulus G" curve, and the slope of the storage modulus G'-loss modulus G" curve is K, where 0.5 < K < 5, and T m represents the melting temperature of the gel film. In particular, for polymers that do not dissolve or melt, an appropriate softening temperature can be selected and tested between T g and T b (T b is the polymer decomposition temperature). 【0066】 According to conventional conclusions on linear viscoelasticity, for polymers, especially linear polymers, the modulus G'-loss modulus G'' curve in the terminal region (the range of the interval toward the maximum angular velocity) fits the frequency dependence, and the longest chain of the polymer contributes to the viscoelastic behavior. 【0067】 The specific steps for the dynamic frequency sweep test are as follows: The dynamic frequency sweep test is performed using a TA-AR2000EX rotational rheometer (TAinstruments, USA), with a parallel plate diameter of 25 mm and a thickness of 0.9 mm. To ensure testing in the linear viscoelastic region, the strain during the dynamic frequency sweep test is 2%, and the test temperature is T m The temperature was +20℃, and the frequency sweep range of the test was 500 rad / s ≤ w 2 The frequency range is ≤0.05 rad / s, which makes it easier to acquire data in the lowest possible frequency range. 【0068】 Dynamic frequency sweep testing can characterize the degree of molecular chain entanglement in solid-phase melt (molten state). If the swelling polymer of the embodiment of this application satisfies the above range, the swelling polymer exhibits a low crosslinking network structure. This degree of crosslinking helps the swelling polymer achieve sustained swelling liquid absorption capacity, improves the stability of the swelling polymer in the liquid storage space, and is advantageous for improving the cycle characteristics of battery cells. 【0069】 For example, K may be a range consisting of 0.51, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 3, 3.5, 4, 4.5, 4.95, or any two of the above values. 【0070】 In some embodiments, the degree of crystallinity of the swollen polymer, as measured by differential scanning calorimetry, is Xc, and 0 <Xc≦30%である。 【0071】 Crystallization refers to the process by which atoms, ions, or molecules in a material are arranged according to a specific spatial order to form an order. The structure of a polymer in a crystal is determined by both intramolecular and intermolecular elements, and intermolecular forces affect the packing density between molecular chains. The degree of crystallization Xc is used to characterize the degree of crystallization in a material and can be measured using differential scanning calorimetry (DSC). Specifically, the measurement steps are as follows: Take 0.5g to 0.8g of sample, place the sample in a crucible, heat and cool the sample under a nitrogen atmosphere, and heat at a rate of 10°C / min to obtain the material's inherent temperature. g Starting at a temperature 20°C lower than that, the material's inherent T m The process temperature is increased to a cutoff temperature 20°C higher than the actual glass transition temperature T of the material, based on the peak heat absorption / desorption values ​​or transition point of the material during the process. g and melting temperature T m Determine the following. 【0072】 When the crystallinity of the swollen polymer falls within the above range, the crystallinity is relatively low, the arrangement of polymer molecular chains tends to be sparse, the inter-chain forces are small, adjacent molecular chains open easily, and liquid electrolyte can easily enter between polymer molecular chains. This improves the liquid absorption and release capacity of the swollen polymer, further improving the cycle characteristics of the battery cell. 【0073】 As an example, the degree of crystallinity X of a swollen polymer measured by differential scanning calorimetry. C The percentage may be within the range of 1%, 2%, 5%, 10%, 15%, 20%, 25%, 30%, or any two of the above values. 【0074】 In some embodiments, the glass transition temperature of the swelling polymer is T g And, T g The temperature range is ≤25℃, and selectively, -60℃ ≤T g The temperature is ≤25℃. 【0075】 The glass transition temperature is the temperature at which a polymer segment transitions from frozen to moving, and the ambient temperature is T gIf the temperature is higher, the polymer segments enter a mobile state and exhibit excellent mobility. When the glass transition temperature of the swollen polymer is within the above range, the polymer segments have a certain degree of mobility, and the polymer gradually adapts to volume deformation due to electrolyte ingress, making destructive deformation less likely. Furthermore, the polymer segments have a certain degree of mobility, providing space for the liquid electrolyte to diffuse and invade. Moreover, the network structure inside the polymer has strong flexibility, which is advantageous in improving the swelling and liquid absorption capacity of the swollen polymer, further improving the cycle characteristics of the battery cell. 【0076】 For example, the glass transition temperature of the swelling polymer may be in the range of -60°C, -30°C, -20°C, -10°C, 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, or any two of the above values. 【0077】 In some embodiments, the elastic modulus of the gel film is E, where E ≤ 1 MPa, and selectively, 0.01 MPa ≤ E ≤ 1 MPa. 【0078】 When the elastic modulus of the gel film is within the above range, the elastic strength of the gel film is low, yield deformation occurs under low external force, meaning that the molecular segments of the swollen polymer are more easily rearranged under external force, and when the swollen polymer is immersed in a liquid electrolyte, the liquid electrolyte solvates the molecular segments with a low energy barrier, making it easier for them to penetrate further into the swollen polymer. 【0079】 For example, the modulus of elasticity of the gel film may be within the range of 1 MPa, 0.9 MPa, 0.8 MPa, 0.7 MPa, 0.6 MPa, 0.5 MPa, 0.4 MPa, 0.3 MPa, 0.2 MPa, 0.1 MPa, 0.05 MPa, 0.02 MPa, 0.01 MPa, or any two of the above values. 【0080】 In the embodiments of this application, the definition of the modulus of elasticity is as known in the art and can be detected using apparatus and instruments known in the art. For example, the mechanical properties of an ink with added polymer are tested using a Shimadzu AGS-X tensile testing machine, and the stress-strain curve of the gel film is measured. Based on the national standard GB / T 1040.3-2006, the sample is cut into a long sample with a width of approximately 5 mm and a length of approximately 50 mm (the gel film thickness is controlled to 1-2 mm), and the tensile properties are measured by setting the tensile speed to 50 mm / min. The modulus of elasticity E = stress max / (width * thickness), and the elongation at break = strain / length. 【0081】 In some embodiments, the elongation at break of the gel film is ε, where ε ≥ 100%. Selectively, 100% ≤ ε ≤ 2000%. 【0082】 When the elongation at break of the gel film is within the above range, it is advantageous for sustained tensile deformation, meaning that the toughness of the network structure inside the swollen polymer is strong and there is a lot of deformation space, allowing for sustained rearrangement of molecular segments under external force, absorbing more liquid electrolyte during the swelling process, and maintaining the relative stability of the network structure through segment movement during swelling, forming a stable liquid storage space. For polymers with the same monomer type and composition ratio, the higher the elongation at break, the higher the corresponding swelling liquid absorption capacity of the polymer. 【0083】 For example, the elongation at break ε of the gel film may be within the range of 100%, 105%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%, 220%, 240%, 250%, 270%, 280%, 300%, 320%, 350%, 400%, 450%, 480%, 500%, 600%, 700%, 800%, 900%, 1000%, 1500%, 2000%, or any two of the above values. 【0084】 In the embodiments of this application, the definition of elongation at break is as known in the art and can be detected using apparatus and equipment known in the art. For example, the mechanical properties of the gel film are tested using Shimadzu's AGS-X tensile testing machine, and the stress-strain curve of the gel film is measured. Based on the national standard GB / T 1040.3-2006, the gel film sample is cut into long samples approximately 5 mm wide and 50 mm long (the thickness of the gel film is controlled to 1-2 mm), the tensile properties are measured by setting the tensile speed to 50 mm / min, and the elongation at break of the gel film is measured. 【0085】 In some embodiments, a gel film is added to a pre-set electrolyte and left to stand at 25°C for ≥24 hours to obtain a second swollen gel film, the pre-set electrolyte containing dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and lithium hexafluoride phosphate (LiPF6), the masses of dimethyl carbonate, ethyl methyl carbonate, and ethylene carbonate being equal, and the molar amount of lithium hexafluoride phosphate (LiPF6) being 1 mol / L. The Shore hardness of the gel film is H a1 The Shore hardness of the second swelling gel film is set to H a2 Therefore, the gel film and the second swollen gel film are 0 ≤ H a2 / H a1 Satisfying ≤ 0.5 and 0 ≤ H a2 ≤ 45, The composition of the pre-set electrolyte and the electrolyte in the battery are similar or nearly identical, and immersion of the gel film in the pre-set electrolyte results in a swollen state of the gel film. Dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) can be considered solvents of the pre-set electrolyte, and lithium hexafluoride phosphate (LiPF6) is the lithium salt of the pre-set electrolyte. 【0086】 When a gel film is immersed in a pre-set electrolyte, the gel film can gradually absorb the solvent, trapping solvent molecules within the film, potentially causing it to swell and gel. The mechanical strength of the gelled gel film may decrease. As the degree of swelling increases, the decrease in mechanical strength becomes more pronounced. Therefore, in the embodiments of this application, the degree of swelling of the gel film can be indicated using the mechanical strength of the gel film before and after swelling. The mechanical strength of the gel film is characterized using Shore hardness. 【0087】 In embodiments of this application, the Shore hardness of the gel film has a meaning known in the art and can be detected using apparatus and methods known in the art, and can be detected based on the national standard GB / T531.1-2008 / ISO 7619-1:2004 "Test method for indentation hardness of vulcanized rubber or thermoplastic rubber, Part 1: Shore hardness method (Shore hardness)". For example, a sample is prepared by laminating three gel films or three second-swelled gel films in the thickness direction, the thickness after lamination is set to 3 mm, and the sample after lamination is measured with a Shore AM hardness tester. 【0088】 After measurement, the gel film and the second swollen gel film of the embodiment of the present application are 0 ≤ H a2 / H a1 Satisfying ≤ 0.5 and 0 ≤ H a2 The value is ≤40. 【0089】 The swelling polymer may be provided on at least one of the first polar sheet and the second polar sheet. The film layer of the first polar sheet has a porous structure, for example, having voids between the active material particles to form a porous structure. The swelling polymer can be dispersed in the porous structure of the first polar sheet. On the one hand, the swelling polymer can form a network that holds liquid using the porous structure as support, improving the interfacial properties of the active material particles, achieving a liquid containment effect, improving the lithium ion transport rate, reducing interfacial side reactions in the active material layer, and improving the cycle characteristics of the battery cell. On the other hand, the swelling polymer swells upon contact with the electrolyte, reducing its mechanical strength. During the cycle charging and discharging process of the battery cell, it can effectively adapt to the expansion and deformation of the active material particles during the charging and discharging process, adhering more effectively to the surface of the active material particles and reducing problems such as delamination of the solid-liquid interface due to swelling and the formation of a gel-like substance. 【0090】 The film layer of the second polar sheet also has a porous structure, and its structural form is the same as that of the first polar sheet. The porous structure may be the porous structure formed between the active material particles in the second polar sheet. The swelling behavior and mechanical properties of the swelling polymer are as described for the first polar sheet, and will not be explained here. 【0091】 When the gel film and the second swollen gel film of the embodiment of the present invention satisfy the above relation, they have a strong swelling ability, a good liquid containment effect on the electrolyte, and can effectively adapt to the expansion and deformation of the active material particles during the charging and discharging process of the battery cell. They can adhere more effectively to the surface of the active material particles, reduce problems such as peeling of the solid-liquid interface due to swelling and the formation of a gel-like substance, and improve the cycle characteristics of the battery cell. 【0092】 For example, the gel film and the second swollen gel film are 0 ≤ H a2 / H a1 It is also acceptable if the value is ≤0.2. 【0093】 For example, H a2 / H a1This can be a range consisting of 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, or any two of the above values. 【0094】 Furthermore, selectively, 20 ≤ H a1 The value is ≤ 100. 【0095】 For example, the Shore hardness of a gel film is H a1 This can be a range consisting of 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, or any two of the above numbers. 【0096】 0 ≤ H a2 The value is ≤45. For example, the Shore hardness H of the second swelling gel film. a2 The range may be 0.1, 0.2, 0.3, 0.5, 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, 5.2, 5.5, 5.8, 6, 6.2, 6.5, 6.8, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, 25, 30, 35, 40, 41, 42, 43, 44, 45, or any two of the above values. 【0097】 In this application, Shore hardness H a1 and Shore hardness H a2 The measurement standards are the same. 【0098】 To further improve the liquid absorption and storage capacity of the swelling polymer, the affinity between the swelling polymer and the electrolyte can be improved by further selecting the material of the swelling polymer, thereby improving the liquid absorption and storage capacity of the swelling polymer. 【0099】 In some embodiments, the swelling polymer may include at least one of a fluoropolymer, an ether-based polymer, an ester-based polymer, and an aldehyde ketone-based polymer. 【0100】 [Fluoropolymer] In some embodiments, the swelling polymer includes a fluoropolymer. 【0101】 In some embodiments, the crystallinity of the fluoropolymer measured by differential scanning calorimetry is X c1 and 0 < X c1 ≤ 30%. Exemplarily, the percentage of the crystallinity X c1 of the fluoropolymer measured by differential scanning calorimetry may be 1%, 5%, 10%, 15%, 20%, 25%, 30%, or a range consisting of any two of the above numerical values. 【0102】 In some embodiments, the melting temperature of the fluoropolymer is T m1 °C and 0 < T m1 ≤ 140°C. Exemplarily, the melting temperature of the polymer may be 10°C, 20°C, 50°C, 70°C, 90°C, 100°C, 120°C, 140°C, or a range consisting of any two of the above numerical values. 【0103】 In some embodiments, the glass transition temperature of the fluoropolymer is T g1 °C and -60°C ≤ T g1 ≤ 25°C. Exemplarily, the glass transition temperature of the fluoropolymer may be -60°C, -30°C, 0°C, 10°C, 25°C, or a range consisting of any two of the above numerical values. 【0104】 Thereby, the fluoropolymer has a relatively low crystallinity, melting temperature, or glass transition temperature. The more excellent the flexibility of the fluoropolymer molecular chain is, the higher the flexibility of the segments of the molecular chain is, the easier the adjacent molecular chains open, the solvent molecules in the electrolyte can enter between the molecular chains of the fluoropolymer, form a gel-like substance, effectively store the electrolyte on the surface of the active material, and improve the wettability of the active material. 【0105】 In some embodiments, the fluoropolymer comprises at least one of the compounds represented by formula (AI) to the compounds represented by formula (AIII). 【0106】 The compound represented by formula (AI) is as follows. [Chemical formula] In formula (AI), R 11 , R 12 , R 13 and R 14 each independently include a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted alkoxy group, and at least one of R 11 , R 12 , R 13 and R 14 contains a fluorine atom. When substituted, the substituent includes one or more of a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, and a halogen atom. The halogen atom may include a fluorine atom, a bromine atom, etc., and is selectively a fluorine atom. 【0107】 Optionally, R 11 , R 12 , R 13 and R 14 each independently include a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C10 alkyl group or a substituted or unsubstituted C1-C10 alkoxy group. 【0108】 Optionally, R 11 , R 12 , R 13 and R 14 each independently include a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C3 alkyl group or a substituted or unsubstituted C1-C3 alkoxy group, and R 11 , R 12 each independently include a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C3 alkyl group or a substituted or unsubstituted C1-C3 alkoxy group, and at least one of R 12 , R 13 and R 14At least one of them contains a fluorine atom. 【0109】 In some embodiments, 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, and further selectively, R 11 , R 12 , R 13 and R 14 Each of these independently contains a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, a fluoromethyl group, a methoxy group, or a perfluoromethoxy group. 【0110】 In some embodiments, the degree of polymerization n of the fluoropolymer is selected from any positive integer between 1000 and 30000, and may be in the range of, for example, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, 16000, 17000, 18000, 19000, 20000, 21000, 22000, 23000, 24000, 25000, 26000, 27000, 28000, 29000, or any two of the above values. 【0111】 In some embodiments, the fluoropolymer comprises at least one compound from the compounds represented by formula (AI-1) to the compounds represented by formula (AI-11). [ka] 【0112】 The compound represented by formula (AII) is as follows: 【0113】 [ka] In equation (AII), R 11 , R12 , R 13 and R 14 Each independently comprises a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkoxy group, and R 11 , R 12 , R 13 and R 14 At least one of these atoms contains a fluorine atom. If substituted, the substituent contains one or more of the following: a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, or a halogen atom. The halogen atom may include a fluorine atom, a bromine atom, etc., and is selectively a fluorine atom. 【0114】 Selectively, R 11 , R 12 , R 13 and R 14 Each of these independently comprises a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C10 alkyl group, or a substituted or unsubstituted C1-C10 alkoxy group. 【0115】 Selectively, R 11 , R 12 , R 13 and R 14 Each independently contains 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. 【0116】 In some embodiments, 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, and further selectively, R 11 , R 12 , R 13and R 14 Each of these independently contains a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, a fluoromethyl group, a methoxy group, or a perfluoromethoxy group. 【0117】 In some embodiments, the degree of polymerization n of the fluoropolymer is selected from any positive integer between 1000 and 30000, and may be in the range of, for example, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, 16000, 17000, 18000, 19000, 20000, 21000, 22000, 23000, 24000, 25000, 26000, 27000, 28000, 29000, or any two of the above values. 【0118】 In some embodiments, the fluoropolymer comprises at least one of the compounds represented by formula (AII-1) to formula (AII-5), [ka] 【0119】 The compound represented by formula (AIII) is as follows: [ka] In equation (AIII), R 15 It contains single bonds, substituted or unsubstituted alkyl groups, and if substituted, the substituents include fluorine atoms. 【0120】 In some embodiments, if substituted, the substituent may include one or more of the following: a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, or a halogen atom. 【0121】 Selectively, R 15 It contains single bonds, substituted or unsubstituted C1-C10 alkyl groups. 【0122】 Selectively, R 15 It contains single bonds, substituted or unsubstituted C1-C3 alkyl groups. 【0123】 In some embodiments, p is selected from any positive integer between 1 and 3, for example, 1, 2, or 3. 【0124】 In some embodiments, the degree of polymerization n of the fluoropolymer is selected from any positive integer between 1000 and 30000, and may be in the range of, for example, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, 16000, 17000, 18000, 19000, 20000, 21000, 22000, 23000, 24000, 25000, 26000, 27000, 28000, 29000, or any two of the above values. 【0125】 In some embodiments, the fluoropolymer comprises at least one of the compounds represented by formula (AIII-1) to formula (AIII-3), [ka] 【0126】 Exemplary examples include one or more of the following: polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoroethylene propene copolymer (FEP), perfluoroalkoxyalkane (PFA), perfluoropolyether (PFPE), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE), and perfluoro(1-butenyl vinyl ether) polymer (CYTOP). 【0127】 Selectively, the fluoropolymer includes one or more of the following: polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoroethylene propene copolymer (FEP), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), and polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE). 【0128】 The above fluoropolymer may be derived from one or more monomers such as fluorocyclohexane, fluoroethylene, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropylene, trifluoropropylene, tetrafluoropropylene, and pentafluoropropylene. Selectively, the above fluoropolymer may be derived from at least two monomers such as fluorocyclohexane, fluoroethylene, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropylene, trifluoropropylene, tetrafluoropropylene, and pentafluoropropylene. 【0129】 The monomers used in the above-mentioned fluoropolymers are all short-chain monomers, which are advantageous for polymerization to form a linear or short-chain branched structure. This structural type results in a low degree of entanglement, which is advantageous for improving the flexibility of the molecular chains. The molecular chains spread sufficiently in the electrolyte, thereby further improving the interfacial properties of the active material. 【0130】 In some embodiments, the molecular weight of the swollen polymer is 2 × 10⁻⁶. 5 From g / mol to 1.5 × 10 6 It is g / mol. 【0131】 When the molecular weight of the swelling polymer is within the above range, the inter-chain forces are relatively weak, which is favorable for solvent molecules in the electrolyte to open the chains and enter between them. This, in turn, is favorable for active ions to enter the active material via the solvent, resulting in smooth and rapid movement of active ions. For example, the molecular weight of the polymer is 2 × 10⁻⁶. 5 g / mol, 5 × 10 5 g / mol, 8 × 10 5 g / mol, 1 × 10⁻⁶ 6 g / mol, 1.5 × 10 6 It may also be a range consisting of g / mol or any two of the above values. 【0132】 The polymers described above are merely examples of structural groups of the main molecular chains. In embodiments of the present application, polymers may also be obtained by copolymerizing the above structural groups with small amounts of other types of structural groups (e.g., compounds such as olefin compounds, ester monomers, nitrile monomers, amide monomers, etc.). 【0133】 [Ether-based polymers] In some embodiments, the swelling polymer includes an ether-based polymer. 【0134】 In some embodiments, an ether-based polymer is manufactured into a sheet-like structure, and the sheet-like structure is (T m2 A dynamic frequency sweep test was performed at +20°C to obtain the elastic modulus G'-loss elastic modulus G'' curve, and the slope of the elastic modulus G'-loss elastic modulus G'' curve is K1, 1 <K1<5であり、T m2 °C represents the melting temperature of the ether polymer. For example, K1 may be in the range of 1.01, 1.1, 2, 3, 4, 4.5, 4.8, 4.9, or any two of the above values. 【0135】 In some embodiments, the glass transition temperature of the ether polymer is T g2 The temperature is in degrees Celsius, and -20°C ≤ T g2It is ≤ 25°C. Exemplarily, the glass transition temperature of the ether-based polymer may be -20°C, -15°C, -10°C, -5°C, -0°C, 5°C, 10°C, 15°C, 20°C, 25°C, or a range consisting of any two of the above numerical values. The ether-based polymer has a certain flexibility above the glass transition temperature, is advantageous for the formation of the gel substance, improves the wetting effect on the electrode sheet, and improves the cycle characteristics of the battery. 【0136】 In some embodiments, the ether-based polymer contains a compound represented by formula (BI), 【Chemical formula】 In formula (BI), R 21 and R 22 each independently contain a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkoxy group, and R 23 contains a single bond, a substituted or unsubstituted methylene group. 【0137】 Optionally, R 21 and R 22 each independently contain a hydrogen atom, a substituted or unsubstituted C1-C10 alkyl group, or a substituted or unsubstituted C1-C10 alkoxy group. 【0138】 Optionally, R 21 and R 22 each independently contain a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group. 【0139】 Optionally, R 23 contains a single bond, a substituted or unsubstituted C1-C10 methylene group. 【0140】 Optionally, R 23 contains a single bond, a substituted or unsubstituted C1-C5 methylene group. 【0141】 For example, an ether polymer comprises at least one compound from the compounds shown in formula (BI-1) to the compounds shown in formula (BI-8). [ka] 【0142】 In some embodiments, the ether polymer comprises a compound represented by formula (BII), [ka] In equation (BII), R 24 ~R 27 Each independently comprises a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group or ether group, and R 24 ~R 27 At least one of these includes a substituted or unsubstituted alkoxy or ether group. 【0143】 Selectively, R 24 ~R 27 Each of these independently comprises a hydrogen atom, a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C1-C10 alkoxy group, or an ether group. 【0144】 Selectively, R 24 ~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 ether group, and R 24 ~R 27 At least one of these includes a substituted or unsubstituted C1-C3 alkoxy group or ether group. 【0145】 Selectively, R 24 ~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 ether group, and R 24 ~R 27At least one of these includes a substituted or unsubstituted C1-C2 alkoxy group or ether group. 【0146】 In some embodiments, the ether polymer comprises at least one of the compounds represented by formula (BII-1) to formula (BII-7), [ka] 【0147】 If substituted, the substituent may include one or more of the following: a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, or a halogen atom, and the halogen atom may include at least one of the following: a fluorine atom, a bromine atom, or a chlorine atom. 【0148】 The polymers described above are merely examples of structural groups of the main molecular chains. In embodiments of the present application, polymers may also be obtained by copolymerizing the above structural groups with small amounts of other types of structural groups (e.g., compounds such as olefin compounds, ester monomers, nitrile monomers, amide monomers, etc.). 【0149】 In some embodiments, the degree of polymerization n of the ether polymer is selected from any positive integer between 1500 and 25000, and may be in the range of, for example, 1500, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, 16000, 17000, 18000, 19000, 20000, 21000, 22000, 23000, 24000, 25000, or any two of the above values. 【0150】 Selectively, the degree of polymerization n of the ether polymer is chosen from a positive integer between 3000 and 18000. 【0151】 In some embodiments, the molecular weight of the ether polymer is 1.2 × 10⁻⁶.5 from 1.0×10 6 g / mol. 【0152】 Exemplarily, the molecular weight of the polymer is 1.2×10 5 g / mol, 2×10 5 g / mol, 5×10 5 g / mol, 8×10 5 g / mol, 1×10 6 g / mol or a range consisting of any two of the above numerical values may also be applicable. 【0153】 [Ester-based polymer] In some embodiments, the swollen polymer contains an ester-based polymer. 【0154】 In some embodiments, the ester-based polymer is manufactured into a sheet-like structure, and the sheet-like structure is subjected to a dynamic frequency sweep test at (T m3 +20) °C to obtain a storage modulus G’ - loss modulus G’’ curve, and the slope of the storage modulus G’ - loss modulus G’’ curve is K2, where 1 < K2 < 5, and T m3 °C represents the melting temperature of the ester-based polymer. Exemplarily, K2 may be 1.01, 1.1, 2, 3, 4, 4.5 or a range consisting of any two of the above numerical values. 【0155】 In some embodiments, the glass transition temperature of the ester-based polymer is T g3 °C, where -20 °C ≤ T g3 ≤ 25 °C. Exemplarily, the glass transition temperature of the ester-based polymer may be -20 °C, -15 °C, -10 °C, -5 °C, -0 °C, 5 °C, 10 °C, 15 °C, 20 °C, 25 °C or a range consisting of any two of the above numerical values. The ester-based polymer has a certain flexibility above the glass transition temperature, which is advantageous for the formation of the gel-like substance, improves the wetting effect on the electrode sheet, and enhances the cycle characteristics of the battery. 【0156】 In some embodiments, the ester-based polymer contains a compound represented by formula (CI), [Chemical formula] In equation (CI), R 31 , R 32 and R 33 Each independently contains a hydrogen atom or a substituted or unsubstituted alkyl group, R 34 This includes substituted or unsubstituted alkyl groups, or substituted or unsubstituted hydroxyalkyl groups. 【0157】 Selectively, R 31 , R 32 and R 33 Each of these independently contains a hydrogen atom or a substituted or unsubstituted C1-C10 alkyl group. 【0158】 Selectively, R 31 , R 32 and R 33 Each independently contains a hydrogen atom or a substituted or unsubstituted C1-C8 alkyl group, R 34 This includes a substituted or unsubstituted C1-C8 alkyl group, or a substituted or unsubstituted C1-C8 hydroxyalkyl group. 【0159】 In some embodiments, R 34 This includes a substituted or unsubstituted C1-C6 alkyl group, or a substituted or unsubstituted C1-C6 hydroxyalkyl group. 【0160】 In some embodiments, R 31 It contains a hydrogen atom or a substituted or unsubstituted methyl group. 【0161】 In some embodiments, R 32 and R 33 Each of these independently contains a hydrogen atom. 【0162】 In some embodiments, R 34 This includes a substituted or unsubstituted C1-C4 alkyl group, or a substituted or unsubstituted C1-C4 hydroxyalkyl group. 【0163】 For example, an ester polymer comprises at least one compound from the compounds represented by formula (CI-1) to the compounds represented by formula (CI-15). [ka] [ka] 【0164】 In some embodiments, the ester polymer comprises a compound represented by formula (CII), [ka] In equation (CII), R 35 It contains substituted or unsubstituted methylene groups. 【0165】 Selectively, R 35 It contains substituted or unsubstituted C1-C10 methylene groups. 【0166】 Selectively, R 35 It contains substituted or unsubstituted C2-C6 methylene groups. 【0167】 Selectively, R 35 It contains substituted or unsubstituted C2-C4 methylene groups. 【0168】 For example, an ester polymer comprises at least one compound from the compounds shown in formula (CII-1) to the compounds shown in formula (CII-5). [ka] 【0169】 In some embodiments, the ester polymer comprises a compound represented by formula (CIII), [ka] In equation (CIII), R 36 , R37 and R 38 Each independently contains a hydrogen atom or a substituted or unsubstituted C1-C8 alkyl group, R 39 It contains a substituted or unsubstituted C1-C8 alkyl group, Selectively, R 36 , R 37 and R 38 Each of these independently contains a hydrogen atom and a substituted or unsubstituted C1-C4 alkyl group. 【0170】 For example, ester polymers are derived from compounds represented by formula (CIII-1) to formula (CIII- 6 It contains at least one of the compounds shown in ) [ka] 【0171】 If substituted, the substituent may include one or more of the following: a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, or a halogen atom. The halogen atom may include at least one of the following: a fluorine atom, a bromine atom, or a chlorine atom. 【0172】 The polymers described above are merely examples of structural groups of the main molecular chains. In embodiments of the present application, polymers may also be obtained by copolymerizing the above structural groups with small amounts of other types of structural groups (e.g., monomers having functional groups such as olefin compounds, acrylonitrile compounds, or maleic anhydride). 【0173】 In some embodiments, the degree of polymerization n of the ester polymer is selected from any positive integer between 800 and 20000, and may be in the range of, for example, 800, 1000, 1500, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, 16000, 17000, 18000, 19000, 20000, or any two of the above values. 【0174】 In some embodiments, the degree of polymerization n of the ester polymer is selected from any positive integer between 1000 and 15000. 【0175】 In some embodiments, the molecular weight of the ester polymer is 1.2 × 10⁻⁶. 5 From g / mol to 1.0 × 10 6 It is g / mol. 【0176】 For example, the molecular weight of an ester polymer is 1.2 × 10⁻⁶. 5 g / mol, 2 × 10⁻⁶ 5 g / mol, 5 × 10 5 g / mol, 8 × 10 5 g / mol, 1 × 10⁻⁶ 6 g / mol, 1.5 × 10 6 It may also be a range consisting of g / mol or any two of the above values. 【0177】 [Aldehyde ketone polymers] In some embodiments, the swelling polymer includes an aldehyde ketone polymer. 【0178】 In some embodiments, an aldehyde ketone polymer is produced into a sheet-like structure, and the sheet-like structure is (T m4 A dynamic frequency sweep test was performed at +20°C to obtain the elastic modulus G'-loss elastic modulus G'' curve, and the slope of the elastic modulus G'-loss elastic modulus G'' curve is K3, and 0.8 ≤ K3 < 5, T m4 °C represents the melting temperature of the aldehyde ketone polymer. For example, K3 may be in the range of 0.8, 0.85, 0.9, 1, 1.01, 1.1, 2, 3, 4, 4.5, or any two of the above values. 【0179】 In some embodiments, the glass transition temperature of the aldehyde ketone polymer is T g4 The temperature is in degrees Celsius, and -20°C ≤ T g4The temperature range is ≤25°C. For example, the glass transition temperature of an aldehyde ketone polymer may be in the range of -20°C, -15°C, -10°C, -5°C, -0°C, 5°C, 10°C, 15°C, 20°C, 25°C, or any two of the above values. Aldehyde ketone polymers exhibit a certain degree of flexibility above their glass transition temperature, which is advantageous for the formation of gel-like substances, improving the wetting effect on electrode sheets and enhancing the battery's cycle characteristics. 【0180】 In some embodiments, the aldehyde ketone polymer comprises a compound represented by formula (DI), [ka] In equation (DI), R 41 R contains a single bond, a substituted or unsubstituted C1-C6 methylene group, 42 It contains a hydrogen atom and a substituted or unsubstituted C1-C6 alkyl group. 【0181】 Selectively, R 41 It contains single bonds, substituted or unsubstituted C1-C2 methylene groups. 【0182】 Selectively, R 42 It contains a hydrogen atom and a substituted or unsubstituted C1-C3 alkyl group. 【0183】 In the embodiments of the present application, a single bond means that there is no group and the atoms on both sides of the group are bonded by a single bond, for example R 41 If it is a single bond, R 41 This means that the carbon atoms on both sides are bonded in the form of a single bond. 【0184】 Exemplary, an aldehyde ketone polymer comprises at least one compound from the compounds represented by formula (DI-1) to the compounds represented by formula (DI-6). [ka] 【0185】 In some embodiments, the aldehyde ketone polymer comprises a compound represented by formula (DII), [ka] In equation (DII), R 43 ~R 46 Each of these independently comprises 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, and each of r and s is independently selected from integers between 0 and 5, and at least one of r and s is selected from any positive integer. 【0186】 Selectively, R 43 ~R 46 Each of these independently contains 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. 【0187】 In some embodiments, the aldehyde ketone polymer comprises at least one compound from the compounds represented by formula (DII-1) to the compounds represented by formula (DII-4). [ka] 【0188】 The polymers described above are merely examples of structural groups of the main molecular chains, and in embodiments of the present application, polymers may also be obtained by copolymerizing the above structural groups with small amounts of other types of structural groups (e.g., olefin compounds, enol compounds, acrylonitrile compounds, etc.). 【0189】 If the above group is substituted, the substituent may include one or more of the following: a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, or a halogen atom. The halogen atom may include at least one of the following: a fluorine atom, a bromine atom, or a chlorine atom. 【0190】 In some embodiments, the degree of polymerization n of the aldehyde ketone polymer is selected from any positive integer between 500 and 15000, and may be in the range of, for example, 500, 800, 1000, 1500, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, or any two of the above values. 【0191】 Selectively, the degree of polymerization n of the aldehyde ketone polymer is chosen from any positive integer between 500 and 10000. 【0192】 In some embodiments, the molecular weight of the aldehyde ketone polymer is 1.2 × 10⁻⁶. 5 From g / mol to 1.0 × 10 6 It is g / mol. 【0193】 For example, the molecular weight of an aldehyde ketone polymer is 1.2 × 10⁻⁶. 5 g / mol, 2 × 10⁻⁶ 5 g / mol, 5 × 10 5 g / mol, 8 × 10 5 g / mol, 1 × 10⁻⁶ 6 g / mol, 1.0 × 10 6 It may also be a range consisting of g / mol or any two of the above values. 【0194】 The relevant parameters of the swelling polymer in the embodiment of the present invention can be measured using the following method. 【0195】 The groups of the swollen polymer in the embodiments of the present invention can be detected using an infrared spectrophotometer (IR), specifically the swollen polymer measured with a Thermo Nicolet Nexus 670 attenuated total reflectance Fourier transform infrared spectrometer (FTIR-ATR). , mark Measurements were taken in reference to GB / T6040-2002, and the test range was as follows: ATR method 600-4000 cm -1 , Reproducibility: ±2cm -1, resolution: 4cm -1 Superior performance, with a penetration depth of 0.2-0.6 μm. 【0196】 The structure of the swollen polymer in the embodiments of the present invention can be detected using nuclear magnetic resonance (NMR), specifically, 1H NMR and 13C NMR are performed using a Varian Mercury Plus-400 nuclear magnetic resonance spectrometer, with a measurement temperature of 20°C, TMS as the internal standard, CDCl3 as the solvent, and a proton resonance frequency of 400 MHz. 【0197】 The polymer monomer type of the swelling polymer in the embodiment of this application (particularly applicable to monomers that make up a small proportion of the polymer) is determined using a combination of decomposition-gas chromatography-mass spectrometry, and the specific measurement steps are as follows: A 0.5 mg sample is accurately weighed and placed in a sample cup, fixed to a sample rod, and then placed in a decomposition device attached near the GC (gas chromatography) sample inlet. After the temperature of the decomposition device reaches the set temperature, the sample injection button is pressed, and the sample cup rapidly falls into the core of the decomposition furnace by free fall. In an inert gas N2 atmosphere, the volatile components are instantly vaporized and separated into a gas chromatography column by a carrier gas. Finally, they are detected via a flame ionization detector (FID) or mass spectrometer (MS) to obtain a gas chromatogram or total ion chromatogram. 【0198】 The molecular weight of the swollen polymer in the embodiments of this application is as known in the art and can be measured using apparatus and methods known in the art, and can be tested by gel permeation chromatography (GPC). The specific test steps are as follows: Take an appropriate amount of the sample to be measured (the sample concentration should ensure a light-shielding degree of 8% to 12%), add 20 ml of deionized water, and simultaneously sonicate for 5 min (53 kHz / 120 W) to ensure complete dispersion of the sample, and then measure the sample according to the GB / T19077-2016 / ISO 13320:2009 standard. 【0199】 The swelling polymer can be placed in various positions, such as within a polar sheet or a separator. The arrangement of the swelling polymer will now be described. 【0200】 In some embodiments, the polar sheet comprises a swelling polymer, specifically, the first polar sheet comprises a current collector and a film layer provided on at least one surface of the current collector, the film layer comprising a swelling polymer and active material particles. The swelling polymer may be provided only in the first polar sheet, or only in the second polar sheet, or the swelling polymer may be provided in both the first and second polar sheets. The first polar sheet may be a positive electrode sheet, and correspondingly the second polar sheet may be a negative electrode sheet. Or the first polar sheet may be a negative electrode sheet, and correspondingly the second polar sheet may be a positive electrode sheet. 【0201】 As an example, the film layer comprises a polymer layer and an active material layer, the polymer layer comprises a swollen polymer, and the active material layer comprises active material particles. The active material layer is provided on at least one surface of the current collector, and the polymer layer is provided on the surface of the active material layer opposite to the current collector. As can be understood, the active material particles and binder etc. dry on the surface of the current collector to form the active material layer, and the swollen polymer is provided on the surface of the active material layer opposite to the current collector. By being provided in this manner, the swollen polymer is advantageous in trapping the electrolyte on the surface of the active material particles, forming a trapped liquid release point, improving the transport rate of active ions while protecting the active material layer interface, reducing interfacial side reactions, and improving the high-temperature storage performance and cycle characteristics of the battery cell. 【0202】 Specifically, the manufacturing process for polarity sheets is as follows: 【0203】 Active material particles are added to a solvent to produce an active paste. 【0204】 The activated paste is applied to the surface of the current collector and allowed to dry and harden to form the active material layer. 【0205】 A swollen polymer is provided on the surface of the active material layer to form a polar sheet. 【0206】 As another example, the active material particles are multiple, with a void between two adjacent active material particles, and the swollen polymer is distributed within the void. This configuration can improve the liquid storage capacity of the active material layer, i.e., its ability to contain the electrolyte, thereby improving the reliability and cycle characteristics of the battery cell. 【0207】 Specifically, the manufacturing process of one embodiment of a polar sheet includes the following: 【0208】 The swollen polymer is dispersed in a solvent to form a mixed system. 【0209】 A paste is produced by adding active material particles to a mixed system. 【0210】 The paste is applied to the surface of the current collector and allowed to dry and harden to form a polarity sheet. 【0211】 Specifically, the manufacturing process for another embodiment of the polar sheet includes the following: 【0212】 A paste is manufactured by dispersing a swollen polymer and active material particles in a solvent. 【0213】 The paste is applied to the surface of the current collector and allowed to dry and harden to form a polarity sheet. 【0214】 As yet another example, the swollen polymer is distributed on the surface of the active material particles, and also in the voids between the active material particles. 【0215】 Specifically, the manufacturing process of one embodiment of a polar sheet includes the following: 【0216】 A paste is manufactured by dispersing a swollen polymer and active material particles in a solvent. 【0217】 The paste is applied to the surface of the current collector and allowed to dry and harden to form a film layer. 【0218】 A swollen polymer is provided on the surface of the film layer to form a polar sheet. 【0219】 In another embodiment, the separator comprises a swelling polymer, and specifically, the separator may include a substrate, and optionally, the separator may further include a coating layer provided on at least one surface of the substrate. 【0220】 For example, the substrate generally has a porous structure, and voids exist in the porous structure, and the swollen polymer is distributed in the voids of the substrate. 【0221】 In another example, the swelling polymer may be distributed within the coating layer. 【0222】 In yet another example, the swollen polymer may be provided on the surface opposite to the substrate of the coating layer. 【0223】 The specific distribution location of the swollen polymer may be one of the three forms described above, two of the three forms, or a combination of the three positions described above. 【0224】 In some embodiments, the separator includes a substrate, the substrate includes a swelling polymer, the swelling polymer may be the main material of the substrate, or the swelling polymer may be mixed with the main material of the substrate to produce the substrate. 【0225】 In yet another embodiment, the swollen polymer may be provided on the polar sheet and the separator, and the specific installation location is as described above, so a detailed explanation is omitted here. 【0226】 In some embodiments, the battery cell further includes a liquid electrolyte, which is located within the electrode assembly. 【0227】 Liquid electrolytes are fluid and can flow more easily around active material particles, improving the transport rate of active ions. In related technologies, liquid electrolytes typically exist in several forms within a battery cell: one is by diffusing into the void structure of the electrode assembly, for example, located in the voids of the polar sheet and / or separator; and the other is free within the battery cell. In contrast, the liquid electrolyte of the embodiments of the present invention exists in several forms: one is by diffusing into the void structure of the electrode assembly, for example, located in the voids of the polar sheet and / or separator; and the other is by diffusing into the swollen polymer. Thus, the liquid electrolyte of the embodiments of the present invention is substantially entirely located inside the electrode assembly, there is essentially no free electrolyte within the battery cell, and the reliability and cycle characteristics of the battery cell can be significantly improved. 【0228】 In some embodiments, the battery cell is further 0 ≤ y / V 総孔 Satisfying ≤15%, y represents the volume of free electrolyte in the battery cell, and its unit is mL. V 総孔 This indicates the numerical value of the void volume of the electrode assembly, in units of mL. 【0229】 When calculating using a formula, substitute only the numerical value and do not substitute the unit. 【0230】 When a battery cell meets the above conditions, the amount of free electrolyte within the battery cell is extremely low, and in fact, it contains virtually no free electrolyte, thereby significantly improving the reliability and cycle characteristics of the battery cell. 【0231】 For example, y / V 総孔 This can be a range consisting of 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any two of the above values. y / V 総孔 A value of 0 indicates that the amount of free electrolyte is 0 mL, meaning there is virtually no free electrolyte in the battery cell. 【0232】 The electrode assembly comprises a first polar sheet, a second polar sheet, and a separator, and the void volume of the electrode assembly is the sum of the void volumes of the first polar sheet, the second polar sheet, and the separator. In the embodiments of this application, the void volume has the meaning known in the art and can be measured using apparatus and methods known in the art, for example, by gas displacement, and the void volume is vm, where v represents the apparent volume (i.e., total volume) and m represents the actual volume. 【0233】 In some embodiments, the battery cell is (m / ρ) / V 総孔 Satisfying ≥80%, V 総孔 This indicates the void volume of the electrode assembly 52, and the unit is mL. m is the difference between the mass of the battery cell before drying and the mass after drying, and its unit is g. 【0234】 ρ represents the density of the electrolyte, and its unit is g / mL. 【0235】 In the embodiments of this application, m may be understood as the total amount of electrolyte in the battery cell. After the electrolyte is injected into the battery cell, the electrolyte exists mainly in the following forms: one is located in the void structure of the polar sheet and / or separator, and the other is diffused into the swollen polymer. m can be measured using the following method: a new battery cell is completely discharged to a 0% SOC charge state, the battery cell is weighed, and the weighed mass is taken as m1. A hole with a diameter of φ5~8 mm is made at a local location in the battery cell, the battery cell is placed above the container with the hole facing downwards and directly above the container, so that the free electrolyte inside the battery cell drips into the container below, and the battery cell is left to stand in this manner for 3h~5h so that all of the free electrolyte inside drips into the container. Next, the battery cells are dried at 60°C to 95°C for 24 to 48 hours, immersed in dimethyl carbonate (DMC) solvent for 12 hours, and then dried again at 60°C to 95°C for 24 to 48 hours. The dried battery cells are then weighed, and the weighed mass is denoted as m2, where m is m1 - m2. For example, the battery cells are dried at 60°C for 5 hours, and then weighed. In the embodiments of this application, the new battery cells may be newly shipped battery cells (not used in charge-discharge cycles after chemical formation), or battery cells that have been attached to a power consumption device and have been used for less than 10 cycles. 【0236】 In the embodiments of this application, when there is free electrolyte in the battery cell, the density ρ of the electrolyte is obtained by the following method: multiple battery cells in the battery, for example 10, are taken, a predetermined mass of electrolyte is poured out, and the volume of the poured-out electrolyte is measured. The ratio of the predetermined mass to the volume is the density ρ of the electrolyte. When there is no free electrolyte in the battery cell, the density ρ of the electrolyte is the density of the electrolyte injected into the battery cell. 【0237】 When a battery cell satisfies the above conditions, the majority of the liquid electrolyte is located within the void structure of the electrode assembly, meaning the electrode assembly itself has good liquid absorption and retention capabilities, which is advantageous for the transport of active ions and improves the dynamic characteristics of the battery cell. Some of the liquid electrolyte can be dispersed in a swelling polymer, and although liquid release occurs during the battery cell's cycle charging and discharging process, the amount of liquid released is relatively small, so the liquid electrolyte is less likely to flow out of the electrode assembly, and the wetting of the electrolyte to the electrode assembly becomes more uniform, thereby improving the battery cell's cycle characteristics. 【0238】 For example, (m / ρ) / V 総孔 ≥80% 、 (m / ρ) / V 総孔 ≥82% 、 (m / ρ) / V 総孔 ≥85% 、 (m / ρ) / V 総孔 ≥86% 、 (m / ρ) / V 総孔 ≥88%, (m / ρ) / V 総孔 ≥90% 、 (m / ρ) / V 総孔 ≥92% or (m / ρ) / V 総孔 It is ≥95%. 【0239】 In some embodiments, the battery cell further satisfies 0 ≤ y / Ah ≤ 15%, y represents the volume of free electrolyte in the battery cell, and its unit is mL. Ah indicates the nominal capacity of a battery cell, and the unit is Ah. 【0240】 When calculating using a formula, only substitute the numerical values ​​into the formula; do not substitute the units. 【0241】 The volume y (mL) of the free electrolyte can be measured using the following method: a new battery cell is completely discharged to a 0% SOC charge state; a hole with a diameter of φ5~8 mm is made at a local location on the battery cell; the battery cell is placed above the container with the hole facing downwards and directly above the container; thereby the free electrolyte inside the battery cell drips into the container below; the battery cell is left to stand in this manner for 3h~5h to allow all of the free electrolyte inside to drip into the container; and then the volume of the electrolyte in the container is measured to obtain y. In this embodiment, the new battery cell may be a battery cell that has just been shipped out (not used in charge / discharge cycles after chemical formation), or a battery cell that has been attached to a power consumption device and has been used for less than 10 cycles. 【0242】 When a battery cell meets the above conditions, the amount of free electrolyte within the battery cell is extremely low, and in fact, it contains virtually no free electrolyte, thereby significantly improving the reliability and cycle characteristics of the battery cell. 【0243】 For example, y / Ah may be in the range of 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any two of the above values. If y / Ah is 0, it indicates that the amount of free electrolyte is 0, i.e., there is substantially no free electrolyte in the battery cell. 【0244】 In some embodiments, after the battery cell undergoes a linear sweep vibration test, it is charged to a 100% charge state (SOC), a hole is drilled in the battery cell, and the hole is placed at the lowest vertical position. The volume of electrolyte flowing out of the battery cell is recorded as M1, where 0 mL ≤ M1 ≤ 0.5 mL, and selectively, M1 is 0 mL. Here, The vibration direction in the linear sweep vibration test is simple vertical harmonic motion. The vibration frequency of the linear sweep vibration test is 10Hz to 55Hz. The maximum acceleration in the linear sweep vibration test is 30 m / s². 2 And, The number of sweep cycles in the linear sweep vibration test was 10. The vibration duration for the linear sweep vibration test is 3 hours. 【0245】 In related technologies, during use, battery cells may experience phenomena such as vibration under external force. The electrolyte located within the electrode assembly may detach from the electrode assembly under vibration, forming free electrolyte. This free electrolyte within the battery cell may leak, leading to corrosion and posing risks such as battery cell failure. In the embodiments of this application, by subjecting the battery cell to standing and vibration treatment, the liquid electrolyte inside the battery cell can be effectively collected and discharged. This allows for a more accurate determination of whether there is a flowing liquid electrolyte between the battery cell housing and the electrode assembly, and thus determines the free electrolyte content. When the battery cell of the embodiments of this application satisfies the above conditions, the free electrolyte content within the battery cell is extremely low, and furthermore, substantially free of free electrolyte, thereby significantly improving the reliability and cycle characteristics of the battery cell. 【0246】 For example, M1 may be in the range of 0 mL, 0.05 mL, 0.1 mL, 0.15 mL, 0.2 mL, 0.25 mL, 0.3 mL, 0.35 mL, 0.4 mL, 0.45 mL, 0.5 mL, or any two of the above values. If M1 is 0 mL, it indicates that the amount of free electrolyte is 0, i.e., the battery cell has virtually no free electrolyte inside after the linear sweep vibration test. 【0247】 In some embodiments, after the above vibration test is performed on the battery cell, the housing is removed, the electrode assembly is taken out and a pressure test is performed, and the volume of electrolyte that flows out from the electrode assembly is recorded as M2 (a pressure device is suspended, and a weighing balance and an electrolyte collection container are installed at the bottom), and 0 mL ≤ M2 ≤ 0.5 mL, selectively, M2 is 0 mL. Here, The direction of pressure applied in the pressure test is perpendicular to the thickness direction of the electrode assembly 52. Regarding the degree of pressure applied in the pressure test, the applied force was 0.35 MPa. 【0248】 In related technologies, battery cells may be subjected to external pressure during use. The electrolyte located within the electrode assembly may detach from the electrode assembly under pressure, forming free electrolyte. This free electrolyte within the battery cell may leak, leading to corrosion and posing risks such as battery cell failure. In this embodiment, a pressure test is performed on the battery cell to effectively force out the liquid electrolyte inside the battery cell. This allows for a more accurate determination of whether there is a flowing liquid electrolyte between the battery cell housing and the electrode assembly, and thus determines the free electrolyte content. If the battery cell of this embodiment satisfies the above conditions, after pressure, the free electrolyte content within the battery cell is extremely low, and furthermore, substantially free of free electrolyte, thereby significantly improving the reliability and cycle characteristics of the battery cell. 【0249】 For example, M2 may be in the range of 0 mL, 0.05 mL, 0.1 mL, 0.15 mL, 0.2 mL, 0.25 mL, 0.3 mL, 0.35 mL, 0.4 mL, 0.45 mL, 0.5 mL, or any two of the above values. If M2 is 0 mL, it indicates that the amount of free electrolyte is 0, meaning that the battery cell has substantially no free electrolyte inside after the pressure test. 【0250】 In some embodiments, a voltage of 200V is applied to the battery formation circuit. 4h The supply is provided, and the absolute value of the temperature change of the battery cell is ≤ 4°C. 【0251】 For example, by connecting the negative terminal of the battery cell and the inside of the outer casing to a 200V voltage to form a current circuit, the battery cell's temperature fluctuation range within 4 hours is 4°C or less, and there are no malfunctions such as ignition or explosion. In particular, when the free electrolyte y=0, the temperature fluctuation range is small, and the reliability of the battery cell's operation is greatly improved. 【0252】 [Positive electrode sheet] The battery cell includes a positive electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material and a swelling polymer. 【0253】 In some embodiments, the positive electrode film layer comprises a polymer layer containing a swollen polymer and a positive electrode active material layer containing positive electrode active material particles, wherein the positive electrode active material layer is provided on at least one surface of the positive electrode current collector, and the polymer layer is provided on the surface of the positive electrode active material layer opposite to the positive electrode current collector. 【0254】 In some embodiments, there are multiple positive electrode active material particles, with a void between two adjacent positive electrode active material particles, and the swollen polymer is distributed within the void, with the positive electrode active material particles and the swollen polymer located in the same film layer. 【0255】 For example, a positive electrode current collector has two opposing surfaces in the thickness direction of itself, and the positive electrode active material layer is provided on one or both of the two opposing surfaces of the positive electrode current collector. 【0256】 The positive electrode active material layer contains a positive electrode active material, and the positive electrode active material can be any positive electrode active material for battery cells known in the art. For example, the positive electrode active material may include at least one of lithium-containing positive electrode active materials and sodium-containing positive electrode active materials, such as at least one of lithium-containing phosphate compounds, lithium-containing transition metal oxides, sodium-containing phosphate compounds, and sodium-containing transition metal oxide materials. 【0257】 For example, the general formula for olivine-type phosphate active materials (lithium-containing phosphate compounds) is Li x A y Me a M b P 1-c X c Y zHere, 0≦x≦1.3, 0≦y≦1.3, and 0.9≦x+y≦1.3. 0.9≦a≦1.5, 0≦b≦0.5, and 0.9≦a+b≦1.5. 0≦c≦0.5, 3≦z≦5. A contains one or more of Na, K, and Mg; Me contains one or more of Mn, Fe, Co, and Ni; M contains one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X contains one or more of S, Si, Cl, B, C, and N; and Y contains one or more of O and F. Specifically, the olivine-type phosphate active material includes one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. 【0258】 Examples include lithium transition metal oxides (layered materials, such as ternary, lithium nickelate / sodium, lithium cobaltate / sodium, lithium manganeseate / sodium, lithium-rich layered, and rock salt phase layered materials). The general formula for layered cathode active materials is Li x A y Ni a Co b Mn c M (1-a-b-c) Y z Here, 0≦x≦2.1, 0≦y≦2.1, and 0.9≦x+y≦2.1. 0≦a≦1, 0≦b≦1, 0≦c≦1, and 0.1≦a+b+c≦1, and 1.8≦z≦3.5. A contains one or more of Na, K, and Mg; M contains one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; and Y contains one or more of O and F. Selectively, y=0. Specifically, the layered cathode active material is lithium cobaltate (LCO), lithium nickelate (LNO), lithium manganeseate (LMO), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NML33), LiNi 0.5 Co 0.2 Mn0.3 O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 It may contain one or more of O2 (NCM811) and NCA. 【0259】 During the charge-discharge process, the molar content of Li discharged from a battery cell differs depending on the state of the battery cell due to the desorption and consumption of active ions, such as Li. In the description of the positive electrode active material in the embodiments of this application, the molar content of Li is the initial state of the material, i.e., the state before the material is introduced. As the positive electrode active material is applied in a battery system and charge-discharge cycles progress, the molar content of Li may change. 【0260】 In the description of the positive electrode active material in the embodiments of this application, the molar content of oxygen (O) is merely a theoretical value, and the release of lattice oxygen causes a change in the molar content of oxygen (O), so the actual molar content of oxygen (O) fluctuates. 【0261】 In the embodiments of the present application, the modified compound may be subjected to doping modification or coating modification. Doping modification may involve adding doping elements, such as transition metals, to the compound, and coating modification may involve surface coating using a material such as carbon, i.e., forming a carbon coating layer or the like on the outer surface of the particles. 【0262】 In some embodiments, the mass content of the swelling polymer is ≤5% of the total mass of the positive electrode film layer, and selectively between 0.05% and 1%. When the mass content of the swelling polymer is within the above range, the swelling polymer can effectively improve the interfacial properties and structural stability of the positive electrode sheet. In this case, the swelling polymer may be located on the same layer as the positive electrode active material particles, or on a different layer. When located on a different layer, it means that the swelling polymer is located in the polymer layer and the positive electrode active material particles are located in the positive electrode active material layer. Selectively, the swelling polymer is located on the same layer as the positive electrode active material particles. 【0263】 For example, swelling The polymer mass content is 0.05%, 0.08%, 0.10%, 0.11%, 0.12%, 0.15%, 0.16%, 0.18%, 0.20%, 0.22%, 0.25%, 0.28%, 0.30%, 0.32%, 0.35%, 0.38%, 0.40%, 0.42%, 0.45%, 0.48%, 0.50%, 0.55%, 0.58%, 0.60%, 0.70%, 0.80%, 0.90%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1%. 5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0%, or a range consisting of any two of the above values. 【0264】 In embodiments of this application, the polymer mass content is as known in the art and can be measured using apparatus and methods known in the art, for example, according to JYT014-1996, by thermogravimetric analysis (TGA), specifically by creating a mass-temperature curve, i.e., a TG curve, based on the mass loss during the heating process of the polar sheet, and reading the corresponding mass loss, i.e., the total mass of polymer in the polar sheet, based on the polymer decomposition temperature, thereby calculating the polymer mass content. The measurement process may be in a nitrogen atmosphere and is detected using the following heating program: 5°C / min, RT~500°C, 10°C / min, 500~600°C, constant temperature at 600°C for 10 min, and end. 【0265】 In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. The metal foil may be, for example, aluminum foil or aluminum alloy foil. The composite current collector may include a polymer substrate layer and a metal material layer formed on at least one surface of the polymer substrate layer. For example, the metal material may include one or more combinations selected from aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, and the polymer substrate layer may include one or more combinations selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE). 【0266】 In some embodiments, the positive electrode active material layer may further selectively contain a positive electrode conductive agent. Embodiments of the present application do not particularly limit the type of positive electrode conductive agent, and for example, the positive electrode conductive agent may include one or more combinations selected from superconducting carbon, conductive carbon black, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass % of the positive electrode conductive agent is 5% or less of the total mass of the positive electrode active material layer. 【0267】 In some embodiments, the positive electrode active material layer may further selectively contain a positive electrode binder. The embodiments of the present application do not particularly limit the type of positive electrode binder, and as an example, the positive electrode binder may include one or more combinations selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene ternary copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ternary copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic resins. In some embodiments, the mass percentage of the positive electrode binder is 5% or less of the total mass of the positive electrode active material layer. The crystallinity of the positive electrode binder is higher than that of the fluoropolymers in the embodiments of the present application. 【0268】 The positive electrode active material layer is generally formed by applying a positive electrode paste to a positive electrode current collector, drying it, and cold pressing it. The positive electrode paste is generally formed by dispersing the positive electrode active material, selectively a swelling polymer, selectively a conductive agent, selectively a binder, and any other components in a solvent and stirring it uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP). The manufacture of the positive electrode sheet is not limited to the above method, and the above-described manufacturing method may be used. 【0269】 [Negative electrode sheet] The battery cell includes a negative electrode sheet. 【0270】 In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector. For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector. 【0271】 In some embodiments, the negative electrode film layer comprises a polymer layer containing a swollen polymer and a negative electrode active material layer containing negative electrode active material particles, wherein the negative electrode active material layer is provided on at least one surface of the negative electrode current collector, and the polymer layer is provided on the surface of the negative electrode active material layer opposite to the negative electrode current collector. 【0272】 In some embodiments, there are multiple negative electrode active material particles, with a void between two adjacent negative electrode active material particles, the swollen polymer is distributed within the void, and the negative electrode active material particles and the swollen polymer are located in the same film layer. 【0273】 The negative electrode active material can be any negative electrode active material for battery cells known in this art. For example, the negative electrode active material includes, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material can include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials. The tin-based material can include at least one of elemental tin, tin oxide, and tin alloy materials. 【0274】 In some embodiments, the mass content of the swelling polymer is ≤5% of the total mass of the negative electrode film layer, and selectively between 0.5% and 3.5%. When the mass content of the swelling polymer is within the above range, the swelling polymer can effectively improve the interfacial properties and structural stability of the negative electrode sheet. In this case, the swelling polymer may be located on the same layer as the negative electrode active material particles, or on a different layer. When located on a different layer, it means that the swelling polymer is located on the polymer layer and the negative electrode active material particles are located on the negative electrode active material layer. Selectively, the swelling polymer is located on the same layer as the negative electrode active material particles. 【0275】 For example, swellingThe polymer mass content is 0.05%, 0.08%, 0.10%, 0.11%, 0.12%, 0.15%, 0.16%, 0.18%, 0.20%, 0.22%, 0.25%, 0.28%, 0.30%, 0.32%, 0.35%, 0.38%, 0.40%, 0.42%, 0.45%, 0.48%, 0.50%, 0.55%, 0.58%, 0.60%, 0.70%, 0.80%, 0.90%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1%. 5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0%, or a range consisting of any two of the above values. 【0276】 In some embodiments, the negative electrode active material layer may further selectively contain a negative electrode conductive agent. Embodiments of the present application do not particularly limit the type of negative electrode conductive agent, and as an example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the negative electrode conductive agent is ≤5% of the total mass of the negative electrode active material layer. 【0277】 In some embodiments, the negative electrode active material layer may further selectively contain a negative electrode binder. Embodiments of the present application do not particularly limit the type of negative electrode binder, and as an example, the negative electrode binder may include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin (SR-1B), aqueous acrylic resin (e.g., polyacrylic acid (PAA), polymethacrylic acid (PMAA), sodium polyacrylate (PAAS)), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the mass percentage of the negative electrode binder is ≤5% of the total mass of the negative electrode active material layer. 【0278】 In some embodiments, the negative electrode active material layer may selectively further contain other additives. For example, the other additives may include thickeners such as sodium carboxymethylcellulose (CMC), PTC thermistor materials, etc. In some embodiments, the mass percentage of the other additives is ≤2% of the total mass of the negative electrode active material layer. 【0279】 In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. The metal foil may, for example, be copper foil. The composite current collector may include a polymer substrate layer and a metal material layer formed on at least one surface of the polymer substrate layer. For example, the metal material may include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer substrate layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE). 【0280】 The negative electrode active material layer is generally formed by applying a negative electrode paste to a negative electrode current collector, drying it, and cold pressing it. The negative electrode paste is generally formed by dispersing the negative electrode active material with a selectively swelling polymer, a selectively conductive agent, a selectively binder, or other selectable auxiliary agents in a solvent and stirring it uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water. The manufacture of the negative electrode sheet is not limited to the above method, and the above-described manufacturing method may be used. 【0281】 The negative electrode sheet does not exclude other additional functional layers other than the negative electrode active material layer. For example, in certain embodiments, the negative electrode sheet of the present invention further includes a conductive primer layer (e.g., consisting of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode active material layer and provided on the surface of the negative electrode current collector. In some other embodiments, the negative electrode sheet of the present invention further includes a protective layer that covers the surface of the negative electrode active material layer. 【0282】 [Separator] The battery cell includes a separator. 【0283】 In some embodiments, the separator includes a substrate. 【0284】 In some embodiments, the separator includes a substrate and a coating layer provided on at least one surface of the substrate. 【0285】 For example, the substrate generally has a porous structure, and voids exist in the porous structure, and the swollen polymer is distributed in the voids of the substrate. 【0286】 In another example, the swelling polymer may be distributed within the coating layer. 【0287】 In yet another example, the swollen polymer may be provided on the surface opposite to the substrate of the coating layer. 【0288】 The specific distribution location of the swollen polymer may be one of the three forms described above, two of the three forms, or a combination of the three positions described above. 【0289】 Embodiments of this application do not particularly limit the material of the substrate, and any known substrate having good chemical and mechanical stability can be selected, such as glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The substrate may be a single-layer film or a multilayer composite film. If the substrate is a multilayer composite film, the materials of each layer may be the same or different. The substrate generally has a porous structure, and voids exist in the porous structure, and the swelling polymer can be distributed in the voids of the substrate. 【0290】 In some embodiments, the coating layer may further contain a filler. Furthermore, the filler may contain at least one of inorganic particles and organic particles. The swelling polymer may be distributed within the coating layer. 【0291】 In some embodiments, the swollen polymer may be provided on the surface opposite to the substrate of the coating layer. 【0292】 In some embodiments, the decomposition temperature of the filler may be 200°C or higher, which gives the filler excellent thermal stability and resistance to decomposition, further improving the heat resistance of the separator. 【0293】 Inorganic particles have high thermal stability and are resistant to decomposition. Selectively, the inorganic particles include at least one of the following: inorganic particles with a dielectric constant of 5 or higher, inorganic particles that are ionic conductive but do not store ions, and inorganic particles that can generate electrochemical reactions. 【0294】 Selectively, inorganic particles with a dielectric constant of 5 or higher include boehmite, aluminum oxide, zinc oxide, silicon oxide, titanium oxide, zirconium oxide, barium oxide, calcium oxide, magnesium oxide, nickel oxide, tin oxide, cerium oxide, yttrium oxide, hafnium oxide, aluminum hydroxide, magnesium hydroxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, magnesium fluoride, calcium fluoride, barium fluoride, barium sulfate, aluminum magnesium silicate, lithium magnesium silicate, sodium magnesium silicate, bentonite, hectorite, zirconium titanate, barium titanate, Pb(Zr,Ti)O3 (abbreviated as PZT), and Pb 1-m La m Zr 1-n Ti n O3 (abbreviation PLZT, 0 <m<1、0<n<1)、Pb(Mg3Nb 2 / 3 The material comprises O3-PbTiO3 (abbreviated PMN-PT) and at least one of the respective modified inorganic particles. Selectively, the modification method for each inorganic particle may be chemical modification and / or physical modification. Chemical modification methods include coupling agent modification (e.g., using silane coupling agents, titanate coupling agents, etc.), surfactant modification, graft polymer modification, etc. Physical modification methods may include mechanical force dispersion, ultrasonic dispersion, high-energy treatment, etc. The modification treatment can reduce the aggregation of inorganic particles, thereby enabling the construction and formation of a more stable and uniform spatial network structure with nanocellulose. Furthermore, by selecting coupling agents, surface active materials, or polymer-modified inorganic particles having specific functional groups, it is possible to further improve the wetting properties of the coating layer to the electrolyte and improve the adhesive strength between the coating layer and the substrate. 【0295】 Selectively, inorganic particles that are ion-conductive but do not store ions include Li3PO4 and lithium titanium phosphate. x1 Ti y1 (PO4)3, Lithium Aluminum Titanium Phosphate x2 Al y2 Ti z1 (PO4)3, (LiAlTiP) x3O y3 is glass, lithium lanthanum titanate Li x4 La y4 TiO3, lithium germanium thiophosphate Li x5 Ge y5 P z2 S w , lithium nitride Li x6 N y6 , SiS2-based glass Li x7 Si y7 S z3 and P2S5-based glass Li x8 P y8 S z4 contains at least one of them, where 0 < x1 < 2, 0 < y1 < 3, 0 < x2 < 2, 0 < y2 < 1, 0 < z1 < 3, 0 < x3 < 4, 0 < y3 < 13, 0 < x4 < 2, 0 < y4 < 3, 0 < x5 < 4, 0 < y5 < 1, 0 < z2 < 1, 0 < w < 5, 0 < x6 < 4, 0 < y6 < 2, 0 < x7 < 3, 0 < y7 < 2, 0 < z3 < 4, 0 < x8 < 3, 0 < y8 < 3, 0 < z4 < 7. Thereby, the ion transport characteristics of the separator can be further improved. 【0296】 Since the organic particles have excellent thermal stability and are difficult to decompose, the heat resistance of the separator can be improved. At the same time, when the internal temperature of the battery cell reaches the melting point of the organic particles due to overcharging abuse, thermal abuse, etc., the organic particles can further melt and be sucked into the pores of the substrate by capillary action to close the pores and play a role in closing the circuit, which is beneficial to ensuring the high safety performance of the battery cell. 【0297】 In some embodiments, the organic particles include, but are not limited to, one or more of the following: polyethylene particles, polypropylene particles, polystyrene particles, melamine resin particles, phenolic resin particles, polyester particles (e.g., polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate), polyimide particles, polyamide-imide particles, polyaramid particles, polyphenylene sulfide particles, polysulfone particles, polyethersulfone particles, polyetheretherketone particles, polyaryletherketone particles, and copolymers of butyl acrylate and ethyl methacrylate (e.g., crosslinked polymers of butyl acrylate and ethyl methacrylate). 【0298】 In some embodiments, the coating layer further comprises a binder. The present application does not particularly limit the type of binder, and any known material having good adhesion can be selected. As an example, the binder comprises at least one of aqueous acrylic resins (e.g., acrylic acid, methacrylic acid, homopolymers of sodium acrylate monomers or copolymers with other comonomers), polyvinyl alcohol, isobutylene-maleic anhydride copolymer, and polyacrylamide. 【0299】 Selectively, the binder content in the coating layer is <30% relative to the mass of the coating layer. 【0300】 [Electrolyte] In some embodiments, the battery cell contains an electrolyte. The electrolyte is trapped within a swollen polymer and located on the surface of the active material particles, becoming a non-free electrolyte. 【0301】 During the charging and discharging process of a battery cell, active ions reciprocate between the positive and negative electrode sheets, being inserted and removed, while the electrolyte plays a role in conducting these active ions between the positive and negative electrode sheets. This invention does not particularly limit the type of electrolyte, and it can be selected according to actual requirements. 【0302】 The electrolyte solution contains an electrolyte salt and a solvent. The types of electrolyte salt and solvent are not specifically limited and can be selected according to actual requirements. 【0303】 If the battery cell of the present application is a lithium-ion battery, the electrolyte salt may, for example, include at least one of the following: lithium hexafluoride phosphate (LiPF6), lithium tetraborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoride arsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium bisoxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP). 【0304】 If the battery cell of the present invention is a sodium-ion battery, the electrolyte salt may, for example, include, at least one of the following: sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium bisfluorosulfonylimide (NaFSI), sodium bistrifluoromethanesulfonylimide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalate borate (NaDFOB), sodium bisoxalate borate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluorobisoxalate phosphate (NaDFOP), and sodium tetrafluorooxalate phosphate (NaTFOP). 【0305】 For example, the solvent may include, but is not limited to, one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), methylsulfonylmethane (MSM), ethyl methanesulfonate (EMS), and diethylsulfone (ESE). 【0306】 In some embodiments, the electrolyte selectively further comprises additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and further additives that can improve specific performance characteristics of the battery, such as additives that improve the overcharge characteristics of the battery, additives that improve the high-temperature characteristics of the battery, and additives that improve the low-temperature power characteristics of the battery. 【0307】 In some embodiments, the positive electrode sheet, separator, and negative electrode sheet can be manufactured into an electrode assembly via a winding process and / or a lamination process. 【0308】 In some embodiments, the battery cell may include an outer casing. This outer casing is used to enclose the electrode assembly and the electrolyte. 【0309】 In some embodiments, the outer casing of the battery cell may be a rigid case such as a hard plastic case, an aluminum case, or a steel case. The outer casing of the battery cell may also be a soft pack such as a pouch-type soft pack. The material of the soft pack may be at least one of plastics, such as polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS). 【0310】 In some embodiments, the positive electrode sheet, separator, and negative electrode sheet can be manufactured into an electrode assembly via a winding process or a lamination process. 【0311】 This invention does not particularly limit the shape of the battery cell, and it may be cylindrical, prismatic, or any other shape. Figure 1 shows a prismatic battery cell 5 as an example. 【0312】 In some embodiments, as shown in Figures 1 and 2, the exterior material may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, forming a housing cavity enclosed by the bottom plate and side plates. The housing 51 has an opening that communicates with the housing cavity, and the cover plate 53 is used to cover the opening and seal the housing cavity. The positive electrode sheet, negative electrode sheet, and separator can form an electrode assembly 52 via a winding or lamination process. The electrode assembly 52 is sealed in the housing cavity. The electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more and can be adjusted as needed. 【0313】 The method for manufacturing the battery cell described in this application is known. In some embodiments, a battery cell can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. For example, an electrode assembly can be formed from a positive electrode sheet, a separator, and a negative electrode sheet through a winding or lamination process. The electrode assembly can then be placed in an outer casing, dried, injected with an electrolyte, and then subjected to processes such as vacuum sealing, settling, chemical conversion, and shaping to obtain a battery cell. 【0314】 In some embodiments of the present invention, the battery cells according to the present invention can be assembled into a battery module, and the number of battery cells included in the battery module may be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. 【0315】 Figure 3 is a schematic diagram of an example battery module 4. As shown in 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 be arranged in any other manner. Furthermore, the multiple battery cells 5 can be fixed in place by fasteners. 【0316】 Selectively, the battery module 4 may further comprise an outer case having a housing space for accommodating multiple battery cells 5. 【0317】 In some embodiments, the above battery modules can be further assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack. 【0318】 The battery module 4 and the battery pack can both be specific examples of the battery in the embodiment of the present invention. 【0319】 Figures 4 and 5 are schematic diagrams of an example battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a battery case and a plurality of battery modules 4 installed inside the battery case. The battery case includes an upper housing 2 and a lower housing 3, the upper housing 2 being used to cover the lower housing 3 and forming a sealed space for housing the battery modules 4. The plurality of battery modules 4 can be arranged inside the battery case in any manner. 【0320】 power consumption equipment According to a second aspect, the present application provides a power consumption device comprising at least one of a battery cell, battery module, or battery pack relating to the present application. The battery cell, battery module, and battery pack may be used as a power source for the power consumption device or as an energy storage element for the power consumption device. The power consumption device may, 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.), trains, ships and satellites, energy storage systems, etc. In some embodiments, the battery cell includes an electrolyte injection port, which is used to inject electrolyte, and when the battery cell is applied to a power consumption device, the electrolyte injection port is located at the bottom along the vertical direction of the battery cell. Because the amount of free electrolyte in the battery cell is extremely small, or even nonexistent, providing the electrolyte injection port at the bottom along the vertical direction of the battery cell can also improve the reliability of the battery cell and the reliability of the power consumption device. 【0321】 The power consumption device can be configured with a battery cell, battery module, or battery pack depending on its operating conditions. Figure 6 is a schematic diagram of an example power consumption device. This power consumption device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power output and high energy density requirements of the power consumption device, a battery pack 1 or a battery module can be used. Another example of a power consumption device may be a mobile phone, a tablet PC, a laptop computer, etc. These power consumption devices are generally required to be lightweight and thin, and can use battery cells as a power source. 【0322】 Examples The following describes examples of the present application. The examples described below are illustrative and are for interpretive purposes only, and should not be considered as limitations thereon. Unless otherwise specified in the examples, the examples should be carried out in accordance with the techniques or conditions described in the literature in the art or in accordance with the product specifications. Unless otherwise specified, the reagents or equipment used are all commercially available, common products. 【0323】 Example 1: Manufacturing of a lithium-ion battery (1) Manufacturing of positive electrode sheets: Swelling polymer, LiNi cathode active material 0.8 Co 0.1 Mn 0.1 O2 (NCM811), the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) are added to N-methylpyrrolidone (NMP) and mixed to produce a cathode paste. The swollen polymer LiNi in the cathode paste 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agentThe mass ratio of carbon black to PVDF is 0.2:97.3:2:0.5. The positive electrode paste is applied to the aluminum foil of the current collector, dried at 85°C, then cold-pressed, followed by trimming, cutting, and slitting, and finally dried for 4 hours under vacuum conditions at 85°C to produce the positive electrode sheet. The degree of crystallinity of the binder polyvinylidene fluoride (PVDF) is 48%, the melting temperature is 164°C, and the glass transition temperature is 39°C. 【0324】 (2) Manufacturing of negative electrode sheets: A negative electrode paste is prepared by uniformly mixing a swelling polymer, artificial graphite (negative electrode active material), carbon black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethylcellulose (CMC) (thickener) in deionized water in a weight ratio of 2.5:94.9:2:0.5:0.1. The negative electrode paste is applied to the copper foil of the current collector, dried at 85°C, then cold-pressed, trimmed, cut, and slit, and finally dried under vacuum conditions at 120°C for 12 hours to produce a negative electrode sheet. 【0325】 (3) Manufacturing of electrolyte: In an environment with a moisture content of less than 10 ppm, non-aqueous organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a volume ratio of 3:7 to obtain an electrolyte solvent. Then, the resulting solvent is mixed with the lithium salt LiPF6 to prepare an electrolyte with a lithium salt concentration of 1 mol / L. 【0326】 (4) Manufacturing of lithium-ion batteries: Using a 16 μm polyethylene film (PE) as a separator, the positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator acting as a barrier between the positive and negative electrode sheets. The assembly is then wound up to obtain an electrode assembly. The electrode assembly is placed in an outer casing, dried, and then injected with electrolyte. A lithium-ion battery is obtained through processes such as vacuum sealing, standing, chemical formation, and shaping. 【0327】 Examples 2 to 4 Lithium-ion batteries were manufactured using the same method as in Example 1, but with the difference from Example 1, the amount of swelling polymer used in Examples 2 to 4 was adjusted. 【0328】 Examples 5 to 9 Lithium-ion batteries were manufactured using the same method as in Example 1, but with the difference from Example 1, in Examples 5 to 9, the type of swelling polymer was adjusted. 【0329】 Examples 10 and 11 Lithium-ion batteries were manufactured in the same manner as in Example 1, but with the difference from Example 1, the type of swelling polymer was adjusted in Examples 10 and 11. 【0330】 Comparative Example 1 A lithium-ion battery was manufactured in the same manner as in Example 1, but the difference from Example 1 is that Comparative Example 1 does not use a swelling polymer. 【0331】 (1) Manufacturing of positive electrode sheets: LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) are added to N-methylpyrrolidone (NMP) and mixed to produce a cathode paste. LiNi in the cathode paste 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agent The mass ratio of carbon black to PVDF is 97.5:2:0.5. The positive electrode paste is applied to the aluminum foil of the current collector, dried at 85°C, then cold-pressed, followed by trimming, cutting, and slitting, and finally dried for 4 hours under vacuum conditions at 85°C to produce the positive electrode sheet. 【0332】 (2) Manufacturing of negative electrode sheets: A negative electrode paste is prepared by uniformly mixing artificial graphite (negative electrode active material), carbon black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethylcellulose (CMC) (thickener) in deionized water in a weight ratio of 94.9:2:0.5:2.6. The negative electrode paste is applied to the copper foil of the current collector, dried at 85°C, then cold-pressed, trimmed, cut, and slit, and finally dried under vacuum conditions at 120°C for 12 hours to produce a negative electrode sheet. 【0333】 Comparative Example 2 A lithium-ion battery was manufactured in the same manner as in Example 1, but the difference from Example 1 was that the type of swelling polymer was adjusted in Comparative Example 2. 【0334】 Examination section 1. Battery cell capacity retention rate test Using Example 1 as an example, the manufactured lithium-ion battery is first defined and C0 is measured. After discharging to 2.8V at 1C, it is left to stand for 5 minutes, then charged to 4.25V with a constant current of 1 / 3C, and further charged to a current of 0.05C at a constant voltage of 4.25V, left to stand for 5 minutes, and then discharged to 2.8V at 1C. The capacity released at this time is defined as C0. 【0335】 Next, the process for the battery capacity retention rate test is as follows: The battery corresponding to Example 1 is charged to 4.25V in a room temperature environment using an equivalent 1.2C step charge (charged to 0.5C0Ah with a constant current of 1.2C, then further charged to 0.3C0Ah with a constant current of 0.87C, and then further charged to V2 with a constant current of 1 / 3C), then charged to a current of 0.05C with a constant voltage of 4.25V, left to stand for 5 minutes, and then discharged to 2.8V at 0.33C. The obtained capacity is defined as the initial capacity C0, and the initial clamping force of the cell is set to 12000N. The above steps are repeated for the same battery, and the discharge capacity Cn of the battery after n cycles is recorded. The battery capacity retention rate Pn after each cycle is calculated as Cn / C0 * 100%, and the values ​​of 250 points, P1, P2...P250, are used as the vertical coordinate, with the corresponding number of cycles as the horizontal coordinate, to obtain a curve diagram of the relationship between the battery capacity retention rate and the number of cycles for the polymer of Example 1. 【0336】 In this test process, the first cycle corresponds to n=1, the second cycle to n=2, ... the 250th cycle to n=250. In Table 3, the battery capacity retention rate data corresponding to Example 1 is the data obtained after 250 cycles under the above test conditions, i.e., the P250 value. 【0337】 The test procedures for Comparative Example 1 and the other examples are the same as described above. 【0338】 2. DC resistance test of battery cells Using Example 1 as an example, the manufactured lithium-ion battery is first defined and C0 is measured. After discharging to 2.8V at 1C, it is left to stand for 5 minutes, then charged to 4.25V with a constant current of 1 / 3C, and further charged to a current of 0.05C at a constant voltage of 4.25V, left to stand for 5 minutes, and then discharged to 2.8V at 1C. The capacity released at this time is defined as C0. 【0339】 Next, the process for testing the DC resistance of the battery is as follows: At 25°C, the battery cell corresponding to Example 1 is charged to 4.25V by an equivalent 1.2C step charge (charged to 0.5C0Ah with a constant current of 1.2C, then further charged to 0.3C0Ah with a constant current of 0.87C, and then further charged to V2 with a constant current of 1 / 3C), and then charged to a current of 0.05C with a constant voltage of 4.25V, left standing for 5 minutes, and the voltage V1 is recorded. Then, it is discharged for 30s at 1 / 3C, the voltage V2 is recorded, and the internal resistance DCR1 of the battery after the first cycle is obtained by (V2-V1) / 1 / 3C. The initial clamping force of the battery cell is set to 12000N. The above steps are repeated for the same battery, and the internal resistance DCRn of the battery after n cycles is recorded (n=1, 2, 3...250). The values ​​of the 250 points DCR1, DCR2, DCR3...DCR250 are used as the vertical coordinate, and the corresponding cycle number is used as the horizontal coordinate to obtain a curve diagram of the battery discharge DCIR and cycle number corresponding to the polymer in Example 1. In this test process, the first cycle corresponds to n=1, the second cycle to n=2, ... the 250th cycle to n=250. In Table 3, the internal resistance increase ratio of the battery in Example 1 = (DCRn - DCR1) / DCR1 * 100%. 【0340】 The test procedures for Comparative Example 1 and the other examples are the same as described above. The data in Table 3 were obtained after 250 cycles under the above test conditions. 【0341】 Test results The test results are shown in Tables 1 to 3. 【0342】 [Table 1] 【0343】 Table 1 indicates that in the monomer, 85% vinyl acetate + 15% ethylene represents a mass content of 85% vinyl acetate and 15% ethylene relative to the total mass of the monomer. Changes in polymerization conditions (polymerization temperature, polymerization pressure, etc.) can cause changes in properties, such as glass transition temperature, even in polymers formed using the same type of monomer. 【0344】 [Table 2] 【0345】 In Table 2, a 0.2% swelling polymer content in the positive electrode sheet indicates that the mass content of the swelling polymer is 0.2% relative to the total mass of the positive electrode film layer. 【0346】 A 0.0% addition of swelling polymer to the cathode sheet indicates that no swelling polymer is added to the cathode film layer. 【0347】 [Table 3] 【0348】 As can be seen from Table 3, the positive and negative electrode sheets of Comparative Example 1 do not contain a swelling polymer. During the lithium-ion battery cycle, the volume of the lithium-ion battery changes, which can cause the electrolyte in the electrode assembly to be pushed out, potentially leading to leakage problems. This increases the risk of lithium dendrite formation, reducing the reliability and cycle characteristics of the lithium-ion battery. 【0349】 Comparative Example 2 has polyethylene oxide added to the polar sheet, but the swelling ability of the polymer is low, resulting in low liquid retention efficiency, and its own high resistance degrades the dynamic characteristics of the battery. 【0350】 In the embodiment of the present invention, by adding a swelling polymer to at least one of the positive electrode sheet, negative electrode sheet, and separator, the swelling polymer can contain the electrolyte and release the electrolyte during the charge and discharge process, improving the electrolyte retention capacity of the electrode assembly and improving the wetting performance of the electrolyte to the electrode assembly, thereby improving the reliability of use and cycle characteristics of the lithium-ion battery. 【0351】 Although exemplary embodiments have been shown and described, as will be understood by those skilled in the art, the above embodiments should not be interpreted as limitations on the present application, and modifications, substitutions, and alterations can be made to the embodiments without departing from the spirit, principles, and scope of the present application.

Claims

[Claim 1] A battery cell comprising an electrode assembly, wherein the electrode assembly comprises a first polarity sheet, a second polarity sheet, and a separator, the polarities of the first polarity sheet and the second polarity sheet being opposite, the separator being placed between the first polarity sheet and the second polarity sheet, and the electrode assembly containing an electrolyte, the solvent of the electrolyte being ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate The material comprises one or more of the following: fluorocarbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), methylsulfonylmethane (MSM), ethyl methanesulfonate (EMS), and diethylsulfone (ESE), and at least one of the first polar sheet, the second polar sheet, and the separator comprises a swelling polymer, wherein the swelling polymer has a swelling capacity of 300% or less. ２ / m １ ≤10000%, m ３ / m ２ Satisfying ≤ 50%, Here, A gel film is produced from the aforementioned swelling polymer, and the mass of the gel film is m １ The unit is g, and the width of the gel film is 10 mm, the length is 10 mm, and the thickness is 1 mm. The gel film was added to an excess amount of dimethyl carbonate (DMC), and after standing at 25°C for 7 days, a first swollen gel film was obtained, and the mass of the first swollen gel film was m ２ The unit is grams. The first swollen gel film was left standing at 25°C for 7 days in an atmosphere with a humidity of 20% or less to obtain a dried gel film, and the mass of the dried gel film was m ３ A battery cell, with units of grams. [Claim 2] 500% ≤ m ２ / m １ ≤ 5000% and the battery cell according to claim 1 [Claim 3] The aforementioned swelling polymer is The aforementioned gel film is T ｍ A dynamic frequency sweep test was performed at +20°C to obtain the elastic modulus G' - loss elastic modulus G'' curve, and the slope of the elastic modulus G' - loss elastic modulus G'' curve is K, where 0.5 < K < 5, and T ｍ The conditions (1) represent the melting temperature of the gel film, The degree of crystallinity of the aforementioned swollen polymer, measured by differential scanning calorimetry, is Xc, where 0 < Xc ≤ 30%. The glass transition temperature of the aforementioned swelling polymer is T ｇ And, T ｇ Condition (2) is ≤25℃, The battery cell according to claim 1, satisfying at least two of the conditions (3) that the elastic modulus of the gel film is E, E ≤ 1 MPa, and the elongation at break of the gel film is ε, ε ≥ 100%. [Claim 4] The gel film is added to a pre-set electrolyte and left to stand at 25°C for ≥24 hours to obtain a second swollen gel film. The pre-set electrolyte consists of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and lithium hexafluoride phosphate (LiPF). ６ ) contains the same mass of dimethyl carbonate, ethyl methyl carbonate and ethylene carbonate, and lithium hexafluoride phosphate (LiPF) ６ The molar amount of ) is 1 mol / L, The Shore hardness of the gel film is H ａ１ The Shore hardness of the second swollen gel film is set to H ａ２ Therefore, the gel film and the second swollen gel film are 0 ≤ H ａ２ / H ａ１ Satisfying ≤ 0.5 and 0 ≤ H ａ２ A battery cell according to any one of claims 1 to 3, wherein the value is ≤ 45. [Claim 5] 0 ≤ H ａ２ / H ａ１ ≤ 0.45 and / or 20 ≤ H ａ１ The battery cell according to claim 4, wherein the coefficient of gravity is ≤ 100. [Claim 6] The swelling polymer comprises a fluoropolymer, and the fluoropolymer comprises at least one compound from the compounds represented by formula (AI) to the compounds represented by formula (AIII). 【Chemistry 1】 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 these contains a fluorine atom, and if substituted, the substituent contains one or more of a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, or a halogen atom. 【Chemistry 2】 In equation (AIII), R １５ It contains a single bond, a substituted or unsubstituted C1-C3 alkyl group, and if substituted, the substituent includes one or more of the following: a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, or a halogen atom. p is selected from any positive integer between 1 and 3. The battery cell according to any one of claims 1 to 3, wherein the degree of polymerization n of the fluoropolymer is selected from any positive integer between 5,000 and 20,000. [Claim 7] The swelling polymer comprises an ether-based polymer, and the ether-based polymer comprises a compound represented by formula (BI) and / or a compound represented by formula (BII). 【Transformation 3】 In equation (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 It contains substituted or unsubstituted C1-C5 alkylene groups, 【Chemistry 4】 In equation (BII), R ２４ ~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 ether group, and R ２４ ~R ２７ At least one of these includes a substituted or unsubstituted C1-C3 alkoxy group or ether group, The battery cell according to any one of claims 1 to 3, wherein the degree of polymerization n of the ether polymer is selected from any positive integer between 1500 and 25000. [Claim 8] The swelling polymer includes an ester polymer, and the ester polymer includes compounds from formula (CI) to formula (CIII). 【Transformation 5】 In formula (CI), R ３１ , R ３２ and R ３３ Each independently contains a hydrogen atom or a substituted or unsubstituted C1-C8 alkyl group, R ３４ This includes a substituted or unsubstituted C1-C8 alkyl group, or a substituted or unsubstituted C1-C8 hydroxyalkyl group. 【Transformation 6】 In equation (CII), R ３５ It contains a substituted or unsubstituted C2-C6 methylene group, 【Transformation 7】 In equation (CIII), R ３６ , R ３７ and R ３８ Each independently contains a hydrogen atom or a substituted or unsubstituted C1-C8 alkyl group, R ３９ It contains a substituted or unsubstituted C1-C8 alkyl group, The battery cell according to any one of claims 1 to 3, wherein the degree of polymerization n of the ester polymer is selected from any positive integer between 800 and 20000. [Claim 9] The swelling polymer comprises an aldehyde ketone polymer, and the aldehyde ketone polymer comprises a compound represented by formula (DI) and / or a compound represented by formula (DII). 【Transformation 8】 In equation (DI), R ４１ R contains a single bond, a substituted or unsubstituted C1-C6 methylene group, ４２ It contains a hydrogen atom, a substituted or unsubstituted C1-C6 alkyl group, 【Chemistry 9】 In equation (DII), R ４３ ~R ４６ Each independently comprises 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, and each independently selected from integers between 0 and 5, and at least one of r and s is selected from any positive integer. The battery cell according to any one of claims 1 to 3, wherein the degree of polymerization n of the aldehyde ketone polymer is selected from any positive integer between 500 and 15000. [Claim 10] The battery cell according to any one of claims 1 to 3, wherein the first polarity sheet includes a current collector and a film layer provided on at least one surface of the current collector, and the film layer includes the swollen polymer and active material particles. [Claim 11] The film layer comprises a polymer layer containing a swollen polymer and an active material layer containing active material particles, wherein the active material layer is provided on at least one surface of the current collector, the polymer layer is provided on the surface of the active material layer opposite to the current collector, and / or The battery cell according to claim 10, wherein the active material particles are plurality, there is a void between two adjacent active material particles, and the swollen polymer is distributed within the void. [Claim 12] The separator includes a substrate and a coating layer provided on at least one surface of the substrate. The swollen polymer is distributed in the voids of the substrate and / or The swollen polymer is distributed within the coating layer and / or The battery cell according to any one of claims 1 to 3, wherein the swollen polymer is provided on the surface of the coating layer opposite to the substrate. [Claim 13] The battery cell according to any one of claims 1 to 3, further comprising a liquid electrolyte, wherein the liquid electrolyte is located within the electrode assembly. [Claim 14] The aforementioned battery cell is (m / ρ) / V 総孔 Satisfying ≥80%, V 総孔 This indicates the numerical value of the void volume of the electrode assembly, and the unit is mL. m is the numerical difference between the mass of the battery cell before drying and the mass after drying, and its unit is g. The battery cell according to claim 13, wherein ρ is a numerical value of the density of the liquid electrolyte, and its unit is g / mL. [Claim 15] The aforementioned battery cell is Satisfying 0 ≤ y / Ah ≤ 15%, y represents the volume of free electrolyte in the battery cell, and its unit is mL. Ah indicates the nominal capacity of the battery cell, and the unit is Ah, as described in any one of claims 1 to 3. [Claim 16] The aforementioned battery cell is 0 ≤ y / V 総孔 Satisfying ≤ 15%, y represents the volume of free electrolyte in the battery cell, and its unit is mL. V 総孔 The battery cell according to any one of claims 1 to 3, wherein indicates the numerical value of the void volume of the electrode assembly, and the unit is mL. [Claim 17] After the battery cell underwent a linear sweep vibration test, it was charged to 100% SOC (State of Charge). A hole was made in the battery cell, and the hole was placed at the lowest vertical position. The volume of liquid electrolyte flowing out of the battery cell was recorded as M1, and it was found that 0 mL ≤ M1 ≤ 0.5 mL. Here, The vibration direction of the linear sweep vibration test described above is simple vertical harmonic motion. The vibration frequency of the linear sweep vibration test described above is 10 Hz to 55 Hz. The maximum acceleration in the linear sweep vibration test was 30 m / s². ２ And, The number of sweep cycles in the linear sweep vibration test is 10. The battery cell according to claim 13, wherein the vibration time of the linear sweep vibration test is 3 hours. [Claim 18] The battery cell according to claim 17, wherein after a linear sweep vibration test, the battery cell is charged to a 100% state of charge (SOC), a hole is made in the battery cell, and the hole is placed at the lowest vertical position, and the volume of liquid electrolyte flowing out of the battery cell is recorded as M1, and M1 is 0 mL. [Claim 19] After the battery cell underwent a linear sweep vibration test, the electrode assembly was removed, and after a pressure test of the electrode assembly, the volume of electrolyte flowing out of the electrode assembly was recorded as M2, and it was found that 0 mL ≤ M2 ≤ 0.5 mL. Here, The pressing direction in the aforementioned pressing test is perpendicular to the thickness direction of the electrode assembly. The battery cell according to claim 17, wherein the degree of pressure applied in the aforementioned pressure test is 0.35 MPa. [Claim 20] The battery cell according to claim 9, wherein after a linear sweep vibration test is performed on the battery cell, the electrode assembly is removed, and after a pressure test is performed on the electrode assembly, the volume of electrolyte flowing out of the electrode assembly is recorded as M2, and M2 is 0 mL. [Claim 21] A battery comprising a battery cell according to any one of claims 1 to 3. [Claim 22] A power consumption device including a battery as described in claim 21.

Images