Battery cells, batteries and power consuming 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 TO RELATED APPLICATIONS

[0001] This application claims priority to a Chinese patent application entitled "Battery Cell, Battery and Power Consumption Device," application number 202311457178.4, filed on November 3, 2023, the entire contents of which are incorporated herein by reference. [Technical Field]

[0002] This application relates to the field of battery technology, and more particularly to battery cells, batteries, and power consuming devices. [Background technology]

[0003] Due to their characteristics such as large capacity and long life, battery cells are widely used in electronic devices such as mobile phones, laptops, battery cars, electric vehicles, electric aircraft, electric ships, electric toy cars, electric toy ships, electric toy aircraft, and power tools.

[0004] With the ever-expanding application range of batteries, the requirements for the performance of battery cells are also gradually becoming more stringent. In order to improve the performance of battery cells, optimization and improvement of battery cells are generally carried out, but the reliability and cycle characteristics of the battery cells are still poor. Summary of the Invention

[0005] The present application has been made in view of the above-mentioned problems, and its object is to provide a battery cell, a battery, and a power consuming device.

[0006] According to a first aspect, the present application provides a battery cell including an electrode assembly, the electrode assembly including a first polar sheet, a second polar sheet, and a separator, the polarities of the first polar sheet and the second polar sheet being opposite, 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 including a swelling polymer, the swelling polymer satisfying 300%≦m2 / m1≦10000%, m3 / m2≦50%, where: A gel film is produced from a swelling polymer. The mass of the gel film is m1 g, the width of the gel film is 10 mm, the length is 10 mm, and the thickness is 1 mm. The gel film is added to an excess amount of dimethyl carbonate (DMC) and left standing at 25°C for 7 days to obtain a first swollen gel film. The mass of the first swollen gel film is m2 g. The first swollen gel film is left standing at 25°C for 7 days in an atmosphere with a humidity of 20% or less to obtain a dried gel film. The mass of the dried gel film is m3 g.

[0007] Thus, when the swelling polymer in the embodiment of the present application satisfies 300% ≤ m2 / m1 ≤ 10000% and m3 / m2 ≤ 50%, the electrolyte can be trapped in the swelling polymer by physical adsorption due to its own liquid trapping ability and liquid release ability. The electrolyte is trapped on the surface of the active material particles, forming a trapped liquid slow release point to release the electrolyte into the electrode assembly, improving the phenomenon of electrolyte shortage. In the process of cyclic charge and discharge of the battery cell, the electrolyte can be continuously wetted on the surface of the active material, not only protecting the active material interface, but also enabling smooth transport of active ions, thereby establishing interface protection, reducing side reactions at the solid-liquid interface, and improving the high-temperature storage performance, usage reliability, cycle characteristics, etc. of the battery cell.

[0008] In some embodiments, 500% ≤ m2 / m1 ≤ 5000%. When the embodiment of the present application satisfies the above range, the usage reliability and cycle characteristics, etc. of the battery cell can be further improved.

[0009] In some embodiments, the swelling polymer satisfies at least two of the following conditions.

[0010] (1) The gel film is subjected to a dynamic frequency sweep test at T m + 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, and 0.5 < K < 5. Tm represents the melting temperature of the gel film.

[0011] (2) The crystallinity of the swollen polymer measured by differential scanning calorimetry is Xc, where 0 < Xc ≤ 30%, and the glass transition temperature of the swollen polymer is T g and T g ≤ 25°C.

[0012] (3) The elastic modulus of the gel film is E, where E ≤ 1 MPa, and the elongation at break of the gel film is ε, where 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 solution and left standing at 25°C for ≥ 24 h to obtain a second swollen gel film. The preset electrolyte solution 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] Let the Shore hardness of the gel film be H a1 and the Shore hardness of the second swollen gel film be 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. Further optionally, 20 ≤ H a1 ≤ 100.

[0016] In this embodiment, the swelling polymer may be provided on at least one of the first and second polar sheets, and the film layer of the first polar sheet may have a porous structure, e.g., voids between the active material particles, and the swelling polymer may be dispersed in the porous structure of the first polar sheet. On the one hand, the swelling polymer may form a network that retains liquid using the porous structure as support, thereby improving the interfacial properties of the active material particles, achieving a liquid confinement effect, increasing the lithium ion transport rate, reducing interfacial side reactions in the active material layer, and improving the cycle performance of the battery cell. On the other hand, the swelling polymer swells upon contact with the electrolyte, reducing its mechanical strength. This allows it to effectively adapt to the expansion and deformation of the active material particles during the charge and discharge cycles of the battery cell, and it can more effectively adhere to the surface of the active material particles, reducing problems such as peeling at the solid-liquid interface caused by swelling to form a gel-like substance.

[0017] In some embodiments, the swelling polymer comprises a fluoropolymer, the fluoropolymer comprising at least one of a compound according to formula (AI) through a compound according to formula (AIII): [ka] In formula (AI) and formula (AII), R 11 , R 12 , R 13 and R 14 each independently comprises a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and R 11 , R 12 , R 13 and R 14 at least one of which contains a fluorine atom, and when substituted, the substituents contain 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; [ka] In formula (AIII), R 15 comprises a single bond, a substituted or unsubstituted C1-C3 alkyl group, and if substituted, the substituents comprise 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; p is selected from any positive integer of 1 to 3.

[0018] In some embodiments, the swelling polymer comprises an ether-based polymer, the ether-based polymer comprising a compound according to formula (BI) and / or a compound according to formula (BII): [ka] In formula (BI), R 21 and R 22 each independently comprises a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; R 23 comprises a substituted or unsubstituted C1-C5 alkylene group, [ka] In formula (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 an ether group, and R 24 ~R 27 At least one of the groups contains a substituted or unsubstituted C1-C3 alkoxy or ether group.

[0019] In some embodiments, the swelling polymer comprises an ester-based polymer, the ester-based polymer comprising a compound according to formula (CI) through formula (CIII): [ka] In formula (CI), R 31 , R 32 and R33 each independently comprises a hydrogen atom or a substituted or unsubstituted C1-C8 alkyl group; R 34 comprises a substituted or unsubstituted C1-C8 alkyl group or a substituted or unsubstituted C1-C8 hydroxyalkyl group; [ka] In formula (CII), R 35 contains a substituted or unsubstituted C2-C6 methylene group, and optionally R 35 each independently comprises a substituted or unsubstituted C2-C4 methylene group; [ka] In formula (CIII), R 36 , R 37 and R 38 each independently comprises a hydrogen atom or a substituted or unsubstituted C1-C8 alkyl group; R 39 comprises a substituted or unsubstituted C1-C8 alkyl group; Selectively, R 36 , R 37 and R 38 each independently comprises a hydrogen atom or a substituted or unsubstituted C1-C4 alkyl group.

[0020] In some embodiments, the swelling polymer comprises an aldehyde ketone polymer, the aldehyde ketone polymer comprising a compound according to Formula (DI) and / or a compound according to Formula (DII): [ka] In formula (DI), R 41 contains a single bond, a substituted or unsubstituted C1-C6 methylene group, and R 42 contains a hydrogen atom, a substituted or unsubstituted C1-C6 alkyl group, [ka] In formula (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 r and s are each independently selected from integers of 0 to 5, and at least one of r and s is selected from any positive integer.

[0021] In some embodiments, the first polar sheet includes a current collector and a film layer disposed on at least one surface of the current collector, the film layer including a swelling polymer and active material particles.

[0022] In some embodiments, the film layer includes a polymer layer containing a swelling polymer and an active material layer containing active material particles, the active material layer being disposed on at least one surface of a current collector, and the polymer layer being disposed on the surface of the active material layer opposite the current collector.

[0023] In some embodiments, the active material particles are plural and have a void between two adjacent active material particles, and the swelling polymer is distributed within the void.

[0024] In some embodiments, the separator includes a substrate and a coating layer disposed on at least one surface of the substrate;

[0025] In some embodiments, the swelling polymer is distributed within the void spaces of the substrate.

[0026] In some embodiments, the swelling polymer is distributed within the coating layer.

[0027] In some embodiments, the swelling polymer is provided on the surface of the coating layer opposite the substrate.

[0028] In some embodiments, the battery cell further includes a liquid electrolyte, the liquid electrolyte being located within the electrode assembly.

[0029] In some embodiments, the battery cell has a (m / ρ) / V 総孔 Meets ≥ 80% V 総孔 indicates the void volume of the electrode assembly in mL, m is the difference in mass between the battery cell before and after drying, expressed in g. ρ is the density of the liquid electrolyte in g / mL.

[0030] Therefore, when the battery cell of the present embodiment satisfies the above conditions, most of the liquid electrolyte is located within the pore structure of the electrode assembly, i.e., the electrode assembly itself has good liquid absorption and retention capabilities, which is beneficial for the transport of active ions and improves the dynamic characteristics of the battery cell. Although some of the liquid electrolyte can be dispersed in the swollen polymer and liquid is released during the cycle charging and discharging 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 electrolyte can wet the electrode assembly more uniformly, thereby improving the cycle characteristics of the battery cell.

[0031] In some embodiments, the battery cell comprises: 0≦y / Ah≦15% is satisfied, y is the volume of free electrolyte in the battery cell, expressed in mL; Ah indicates the nominal capacity of the battery cell, expressed in units of Ah.

[0032] As a result, when the battery cell of the embodiment of the present application satisfies the above conditions, the content of free electrolyte in the battery cell is extremely small, and even the battery cell contains substantially no free electrolyte, thereby significantly improving the usage reliability and cycle characteristics of the battery cell.

[0033] In some embodiments, the battery cell comprises: 0≦y / V 総孔 Meets ≦15% y is the volume of free electrolyte in the battery cell, expressed in mL; V 総孔 indicates the void volume of the electrode assembly, in mL.

[0034] As a result, when the battery cell of the embodiment of the present application satisfies the above conditions, the content of free electrolyte in the battery cell is extremely small, and even the battery cell contains substantially no free electrolyte, thereby significantly improving the usage reliability and cycle characteristics of the battery cell. In some embodiments, the battery cell is subjected to a linear sweep vibration test, and then charged to 100% SOC; a hole is drilled in the battery cell, and the hole is positioned at the lowest vertical position; and the volume of the liquid electrolyte flowing out of the battery cell is recorded as M1, where 0 mL≦M1≦0.5 mL, and optionally, M1 is 0 mL; where: The vibration direction of the linear sweep vibration test is simple harmonic motion up and down. The vibration frequency of the linear sweep vibration test is 10Hz to 55Hz. The maximum acceleration for linear sweep vibration testing is 30 m / s 2 and The number of sweep cycles in the linear sweep vibration test was 10. The vibration time for the linear sweep vibration test is 3 hours.

[0035] As a result, when the battery cell of the embodiment of the present application satisfies the above conditions, the content of free electrolyte in the battery cell is extremely small, and even the battery cell contains substantially no free electrolyte, thereby significantly improving the usage reliability and cycle characteristics of the battery cell.

[0036] In some embodiments, the battery cell is subjected to a linear sweep vibration test, and then the electrode assembly is removed. After the electrode assembly is subjected to a compression test, the volume of the electrolyte flowing out of the electrode assembly is recorded as M2, and 0 mL≦M2≦0.5 mL is satisfied, and optionally, M2 is 0 mL; where: The pressing direction in the pressing test is perpendicular to the thickness direction of the electrode assembly. The pressure level in the compression test is 0.35 MPa.

[0037] As a result, when the battery cell of the embodiment of the present application satisfies the above conditions, the battery cell will have an extremely small amount of free electrolyte inside after being pressed, and will even contain substantially no free electrolyte inside, thereby significantly improving the usage reliability and cycle characteristics of the battery cell.

[0038] According to a second aspect, the present application provides a battery including a battery cell according to any embodiment of the first aspect of the present application.

[0039] According to a third aspect, the present application provides a power consuming device including a battery according to any embodiment of the second aspect of the present application. [Brief explanation of the drawings]

[0040] In order to more clearly describe the technical solutions in the embodiments of the present application, the following briefly describes the drawings required for the embodiments of the present application. It should be understood that the drawings shown below are only some embodiments of the present application, and those skilled in the art can further obtain other drawings based on the drawings without any creative efforts.

[0041] [Figure 1] 1 is a schematic diagram of one embodiment of a battery cell of the present application. [Figure 2] 2 is an exploded schematic view of the battery cell shown in FIG. 1 according to an embodiment. [Figure 3] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 4] 1 is a schematic diagram of an embodiment of a battery pack of the present application. [Figure 5] 5 is an exploded schematic view of the battery pack shown in FIG. 4 according to the embodiment. [Figure 6] 1 is a schematic diagram of one embodiment of a power consuming device that includes a battery cell of the present application as a power source.

[0042] The drawings are not drawn to scale. [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 DETAILED DESCRIPTION OF THE INVENTION

[0044] Hereinafter, embodiments specifically disclosing the battery cell, battery, and power consumption device of the present application will be described in detail with reference to the accompanying drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and redundant description of actually identical structures may be omitted. This is to avoid the following description becoming unnecessarily long and to facilitate understanding by those skilled in the art. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0045] The "ranges" disclosed herein are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, with the selected lower and upper limits defining the boundaries of the particular range. Such defined ranges may be inclusive or exclusive of their endpoints, and are arbitrarily combinable; i.e., any lower limit can be combined with any upper limit to form a single range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if 1 and 2 are listed as minimum range values ​​and 3, 4, and 5 are listed as maximum range values, the ranges 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all contemplated. In this application, unless otherwise specified, a numerical range "a to b" is a shorthand representation of any combination of real numbers a to b, where a and b are both real numbers. For example, the numerical range "0-5" represents a list of all real numbers between "0-5" in this specification, and "0-5" is merely a shorthand representation of combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that this parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0046] Unless otherwise stated, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0047] Unless otherwise stated, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0048] All steps in this application can be performed sequentially or randomly, and are preferably performed sequentially, unless otherwise specified. For example, if a method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, if it is said that the method may further include step (c), it means that step (c) may be added to the method in any order, e.g., the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[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 installed between the positive electrode sheet and the negative electrode sheet and serves mainly to prevent short circuits between the positive electrode sheet and the negative electrode sheet, while allowing active ions to pass freely through the separator to form a circuit.

[0050] During the charging and discharging cycles of a battery cell, active ions may be inserted into or removed from the active material, which may cause changes in the volume of the electrode assembly (e.g., expansion and deformation). This may cause the electrolyte wetted by the electrode assembly to be constantly extruded, and the extruded electrolyte may not all be absorbed into the electrode assembly. This may result in an electrolyte bridging phenomenon within the electrode assembly, which may prevent the active material from being sufficiently wetted, resulting in localized liquid shortages in the active material, making charging and discharging cycles impossible in those areas, resulting in a rapid deterioration of dynamic properties, metal precipitation at the interface, and an increased risk of dendrites. As the dendrites grow, they may penetrate the separator, causing a short circuit between the positive and negative electrode sheets, thereby deteriorating the usage reliability and cycle performance of the battery cell.

[0051] In view of the above, the present application provides a battery cell in which a swelling polymer is added to an electrode assembly, and after contacting the swelling polymer with an electrolyte, the swelling polymer can confine the electrolyte between the polymer molecular chains through physical adsorption and release the electrolyte into the electrode assembly, thereby alleviating the electrolyte shortage phenomenon and reducing side reactions at the solid-liquid interface, thereby improving the usage reliability and cycle performance of the battery cell. The technical solution of the present application is described in detail below.

[0052] Battery cell According to a first aspect, the present application provides a battery cell including an electrode assembly, the electrode assembly including 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, and at least one of the first polar sheet, the second polar sheet, and the separator including a swelling polymer; where: A gel film was prepared from the swollen polymer, and the mass of the gel film was m1g, the width of the gel film was 10mm, the length was 10mm, and the thickness was 1mm. The gel film was added to an excess amount of dimethyl carbonate (DMC) and allowed to stand at 25°C for 7 days, after which a first swollen gel film was obtained, and the mass of the first swollen gel film was m2g; The first swollen gel film is allowed to stand 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 is m3g; The swelling polymer satisfies the conditions 300%≦m2 / m1≦10000%, m3 / m2≦50%.

[0053] In embodiments of the present application, the swellable polymer may include a variety of materials, such as a polymer that is solid at room temperature (e.g., 0 to 45°C) or a polymer that is liquid at room temperature, and different forms of polymers can be fabricated into gel films using different methods.

[0054] Specifically, for a polymer that is solid at room temperature, the polymer 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 the polymer film is referred to as a gel film, with a width of 10 mm, a length of 10 mm, and a thickness of 1 mm. Dissolution refers to the process of mixing a solute and a solvent to form a homogeneous phase. The ability of a polymer to dissolve in a solvent can generally be understood to mean that the solubility of the polymer in the solvent is greater than 10 g.

[0055] For polymers that are solid at room temperature and do not dissolve in solvents, take 10 g of polymer and measure its melting point (T m The polymer is pressed into a 1 mm solid polymer film at a temperature of +20°C. In particular, for polymers that do not melt or dissolve, 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°C for 12 hours. After drying, the polymer is hot-pressed into a thin film in a vulcanization press, and the hot-pressing temperature is (T m The temperature was set at +20°C, the rolling thickness was 1-2 min, the rolling time was 2 min, and the pressure was 8 MPa. After 2 min of rolling, the sample was removed and cold-pressed in another vulcanizing press of the same type at a pressure of 10 MPa. A 10 cm x 10 cm square mold was used to obtain a gel film of a fixed size. "A polymer that is insoluble in a solvent" generally means that the polymer is poorly soluble in the solvent and has a solubility of less than 0.01 g in the solvent.

[0056] For liquid polymers at room temperature, take an appropriate amount of sample and dry it at the boiling point of a solvent, such as NMP, for ≥8 hours to obtain a polymer film. The thickness of the polymer film is related to the solid content of the liquid + the total height of the liquid before drying. A liquid with a solid content of 50% can be prepared and poured into a solid container to a height of 2 mm. After drying, a gel film of 2 mm x 50% = 1 mm will be obtained.

[0057] The gel film was added to an excess amount of dimethyl carbonate (DMC (mass ratio of gel film to DMC: 1:100)), where the excess amount means that the gel film still contained free dimethyl carbonate (DMC) after being added to DMC and left at 25°C for 7 days to obtain a first swollen gel film.

[0058] The gel film is swellable, i.e., it can absorb DMC in the DMC, causing a volume expansion phenomenon, where m2 is the mass of the gel film after absorbing DMC, and m2 / m1 characterizes the liquid absorption capacity of the gel film, which in turn characterizes the liquid absorption capacity of the swollen polymer, and thus m2 / m1 can be defined as the liquid absorption amount of the gel film. When 300%≦m2 / m1≦10,000%, the swelling performance of the swollen polymer is good, which is favorable for absorbing and trapping liquid electrolyte within the swollen polymer, thereby fulfilling the liquid retention function, and the mass of free electrolyte in the battery cell is small or even zero. As the mass of free electrolyte decreases, the risk of battery cell leakage, which causes reliability problems, is further reduced, and the reliability and cycle characteristics of the battery cell can be improved.

[0059] When the first swollen gel film is dried in a relatively dry environment (an atmosphere with a humidity of 20% or less), the solvent in the first swollen gel film is gradually released, where m3 is the mass of the first swollen gel film after drying, and m3 / m2 can be used to characterize the liquid release capacity of the gel film, which in turn characterizes the liquid release capacity of the swollen polymer, and thus m3 / m2 can be defined as the liquid release amount of the gel film. When m3 / m2 is ≦50%, the swollen polymer has good liquid electrolyte release capacity, and during the cycle charging and discharging of the battery cell, the liquid electrolyte trapped in the swollen polymer can be released and released into the electrode assembly, quickly replenishing the liquid wetting capacity of areas in the electrode assembly where liquid is insufficient, thereby uniforming the wetting capacity of the entire electrode assembly and reducing side reactions at the solid-liquid interface, thereby improving the usage reliability and cycle characteristics of the battery cell.

[0060] When the swelling polymer in the embodiment of the present application satisfies 300% ≤ m2 / m1 ≤ 10000% and m3 / m2 ≤ 50%, the electrolyte can be confined in the swelling polymer by physical adsorption due to its own liquid confinement ability and liquid release ability. The electrolyte is confined on the surface of the active material particles, forming a confined liquid slow release point to release the electrolyte into the electrode assembly, improving the phenomenon of electrolyte shortage. In the process of cyclic charge and discharge of the battery cell, the electrolyte can be continuously wetted on the surface of the active material, not only protecting the active material interface, but also enabling smooth transport of active ions, thereby establishing interface protection, reducing side reactions at the solid-liquid interface, and improving the high-temperature storage performance, service reliability, cycle characteristics, etc. of the battery cell.

[0061] In some embodiments, 500% ≤ m2 / m1 ≤ 5000%. When the embodiment of the present application satisfies the above range, the high-temperature storage performance, service reliability, cycle characteristics, etc. 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 composed 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 composed of any two of the above numerical values.

[0064] To further improve the liquid containment and release capabilities of the swollen polymer, the swollen polymer is further selected, for example, its physical and chemical properties are further selected, thereby selecting a swollen polymer with superior performance.

[0065] In some embodiments, the gel film is m A dynamic frequency sweep test was performed at +20°C to obtain the elastic modulus G'-loss elastic modulus G" curve. The slope of the elastic modulus G'-loss elastic modulus G" curve was K, which was 0.5 <K<5であり、T m represents the melting temperature of the gel film. In particular, for polymers that do not melt or dissolve, T g and T b (T b The appropriate softening temperature can be selected and tested between the polymer decomposition temperature.

[0066] According to the conventional conclusion of linear viscoelasticity, for polymers, especially linear polymers, the elastic modulus G'-loss modulus G" curve conforms to the frequency dependence in the terminal region (the range toward the maximum angular velocity) of the elastic modulus G'-loss modulus G" curve, and the longest chain of the polymer contributes to the viscoelastic behavior.

[0067] The specific steps of the dynamic frequency sweep test are as follows: The dynamic frequency sweep test was performed using a TA-AR2000EX rotational rheometer (TA Instruments, USA), with a parallel plate diameter of 25 mm and a thickness of 0.9 mm. To ensure the test was performed in the linear viscoelastic region, the strain during the dynamic frequency sweep test was 2% and the test temperature was T m +20℃, the test frequency sweep range is 500rad / s≦w 2 ≦0.05 rad / s, which makes it easier to obtain data in the lowest possible frequency range.

[0068] The dynamic frequency sweep test can characterize the degree of entanglement of molecular chains in a solid-phase melt (molten state). When the swollen polymer of the present embodiment satisfies the above range, the swollen polymer exhibits a low-crosslinked network structure. This crosslinking degree helps the swollen polymer achieve a sustained swelling liquid absorption capacity and improves the stability of the swollen polymer in the liquid storage space, which is beneficial to improving the cycle characteristics of the battery cell.

[0069] Illustratively, K may be 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 a range consisting of any two of the foregoing values.

[0070] In some embodiments, the crystallinity of the swollen polymer as measured by differential scanning calorimetry is Xc, and is 0 <Xc≦30%である。

[0071] Crystallization refers to the process by which atoms, ions, or molecules in a material are arranged in a certain spatial order to form an order. The structure of a polymer in a crystal is determined by both intramolecular and intermolecular factors, and intermolecular forces affect the packing density between molecular chains. Crystallinity 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: A 0.5-0.8g sample is placed in a crucible and heated and cooled under a nitrogen atmosphere at a heating rate of 10°C / min. The intrinsic T g Starting at a temperature 20°C lower than the material's inherent T m The temperature is raised to the cutoff temperature of the process, which is 20°C higher than the actual glass transition temperature T of the material based on the heat absorption / dissipation peak value or transition point of the material in the process. g and melting temperature T m etc. will be determined.

[0072] When the crystallinity of the swollen polymer is within the above range, the crystallinity is relatively low, the polymer molecular chains tend to be sparsely arranged, the inter-molecular force is small, adjacent molecular chains are easily opened, and the liquid electrolyte can easily enter between the polymer molecular chains, thereby improving the liquid absorption and release capabilities of the swollen polymer and further improving the cycle performance of the battery cell.

[0073] Illustratively, the crystallinity X of the swollen polymer measured by differential scanning calorimetry C The percentage may be 1%, 2%, 5%, 10%, 15%, 20%, 25%, 30%, or a range consisting of any two of the foregoing values.

[0074] In some embodiments, the glass transition temperature of the swollen polymer is T g and T g ≦25℃, and optionally, -60℃≦T g ≦25°C.

[0075] The glass transition temperature is the temperature at which the polymer segments transition from frozen to mobile, and is the temperature at which the ambient temperature T g When the glass transition temperature of the swollen polymer is higher, the polymer segments enter a mobile state and have excellent mobility. When the glass transition temperature of the swollen polymer is within the above range, the polymer segments have a certain mobility, allowing the polymer to gradually adapt to the volumetric deformation caused by the intrusion of the electrolyte and making destructive deformation less likely to occur. Furthermore, the polymer segments have a certain mobility, providing space for the liquid electrolyte to diffuse and infiltrate. Furthermore, the internal network structure of the polymer has strong flexibility, which is beneficial to improving the swelling and liquid absorption capabilities of the swollen polymer and further improving the cycle performance of the battery cell.

[0076] Illustratively, the glass transition temperature of the swollen polymer may be −60° C., −30° C., −20° C., −10° C., 0° C., 5° C., 10° C., 15° C., 20° C., 25° C., or a range consisting of any two of the foregoing values.

[0077] In some embodiments, the gel film has a modulus of elasticity, E, where E≦1 MPa, and optionally, 0.01 MPa≦E≦1 MPa.

[0078] When the elastic modulus of the gel film is within the above range, the gel film has low elastic strength and undergoes yield deformation under the action of a low external force, i.e., the molecular segments of the swollen polymer are more likely to rearrange under the action of an 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 enter the swollen polymer.

[0079] For example, the elastic modulus of the gel film may be 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 a range consisting of any two of the above values.

[0080] In the embodiments of this application, the definition of elastic modulus is as defined in the art and can be measured using devices and instruments known in the art. For example, a Shimadzu AGS-X tensile tester is used to test the mechanical properties of the ink containing the polymer and measure the stress-strain curve of the gel film. Based on the national standard GB / T 1040.3-2006, the sample is cut into a long specimen approximately 5 mm wide and 50 mm long (the gel film thickness is controlled to 1-2 mm), and the tensile properties are measured at a tension speed of 50 mm / min. Elastic modulus E = stress max / (width * thickness), and elongation at break = strain / length.

[0081] In some embodiments, the gel film has a breaking elongation, ε, where ε≧100%. Optionally, 100%≦ε≦2000%.

[0082] When the elongation at break of the gel film is within the above range, it is favorable for sustained tensile deformation, i.e., the network structure inside the swollen polymer has strong toughness and has a large deformation space, and under the action of external force, the molecular segments can continuously rearrange, absorbing more liquid electrolyte during the swelling process, and the movement of the segments during the swelling process maintains the relative stability of the network structure, 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] Illustratively, the breaking elongation ε of the gel film may be 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 a range consisting of any two of the above values.

[0084] In the embodiments of the present application, the definition of breaking elongation has a meaning known in the art and can be measured using devices and instruments known in the art. For example, a Shimadzu AGS-X tensile tester is used to test the mechanical properties of the gel film and measure the stress-strain curve of the gel film. In accordance with the national standard GB / T 1040.3-2006, a gel film 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 to 2 mm), and the tensile properties are measured at a pulling speed of 50 mm / min to measure the breaking elongation of the gel film.

[0085] In some embodiments, the gel film is added to a predetermined electrolyte solution and allowed to stand at 25°C for ≥ 24 hours to obtain a second swollen gel film, wherein the predetermined electrolyte solution includes dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and lithium hexafluorophosphate (LiPF), wherein the masses of the dimethyl carbonate, ethyl methyl carbonate, and ethylene carbonate are equal, and the molar amount of the lithium hexafluorophosphate (LiPF) is 1 mol / L; Shore hardness of gel film is H a1 The Shore hardness of the second swollen gel film is H a2 Then, the gel film and the second swollen gel film are in the range of 0≦H a2 / H a1 ≦0.5 and 0≦H a2 ≦45, The composition of the preset electrolyte and the electrolyte in the battery are similar or almost the same, and the gel film is immersed in the preset electrolyte to reveal its swelling state. Dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) can be considered as solvents for the preset electrolyte, and lithium hexafluorophosphate (LiPF6) is the lithium salt of the preset electrolyte.

[0086] When a gel film is immersed in a predetermined electrolyte solution, the gel film can gradually absorb the solvent, trapping the solvent molecules within the gel film, causing the gel film to swell and gelate, and the mechanical strength of the gelled gel film can decrease. As the degree of swelling increases, the decrease in mechanical strength becomes more pronounced. Therefore, in embodiments of the present application, the mechanical strength of the gel film before and after swelling can be used to indicate the degree of swelling of the gel film. The Shore hardness is used to characterize the mechanical strength of the gel film.

[0087] In the embodiments of the present application, the Shore hardness of the gel film has the meaning known in the art and can be measured using devices and methods known in the art, and can be measured in accordance with national standard GB / T531.1-2008 / ISO 7619-1:2004 "Test method for indentation hardness of vulcanized or thermoplastic rubber, Part 1: Shore hardness method (Shore hardness)." For example, three pieces of gel film or three pieces of second swollen gel film are laminated in the thickness direction to prepare a sample, and the thickness after lamination is 3 mm, and the laminated sample is measured using a Shore AM type hardness tester.

[0088] After the measurement, the gel film and the second swollen gel film of the present embodiment have a viscosity of 0≦H a2 / H a1 ≦0.5 and 0≦H a2 ≦40.

[0089] The swelling polymer 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 may have a porous structure, e.g., voids between the active material particles, and the swelling polymer may be dispersed in the porous structure of the first polar sheet. On the one hand, the swelling polymer may form a network that retains liquid using the porous structure as support, thereby improving the interfacial properties of the active material particles, achieving a liquid confinement effect, increasing the lithium ion transport rate, reducing interfacial side reactions in the active material layer, and improving the cycle performance of the battery cell. On the other hand, the swelling polymer swells upon contact with the electrolyte, reducing its mechanical strength. This allows it to effectively accommodate the expansion and deformation of the active material particles during the charge and discharge cycles of the battery cell, and it can more effectively adhere to the surface of the active material particles, reducing problems such as peeling at the solid-liquid interface caused by swelling to form a gel-like substance.

[0090] The film layer of the second polar sheet also has a porous structure, and its structural format is the same as that of the first polar sheet. The porous structure may be a porous structure formed between the active material particles in the second polar sheet. The swelling behavior and mechanical properties of the swelling polymer are the same as those described for the first polar sheet, and therefore will not be described here.

[0091] When the gel film and second swollen gel film of the embodiment of the present application satisfy the above relationship, they have strong swelling ability, good liquid containment effect for the electrolyte, and can effectively adapt to the expansion and deformation of the active material particles during the charge and discharge cycle of the battery cell, and can be more effectively attached to the surface of the active material particles, reducing problems such as peeling of the solid-liquid interface caused by swelling to form a gel-like material, and improving the cycle characteristics of the battery cell.

[0092] Illustratively, the gel film and the second swollen gel film have a viscosity of 0≦H a2 / H a1 ≦0.2 may be satisfied.

[0093] For example, H a2 / H a1 may be 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, or a range consisting of any two of the above values.

[0094] More selectively, 20≦H a1 ≦100.

[0095] For example, the Shore hardness H of the gel film a1 may be 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, or a range consisting of any two of the above values.

[0096] 0≦H a2 For example, the Shore hardness H of the second swollen gel film is ≦45. a2may 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 a range consisting of any two of the above numerical values.

[0097] In this application, Shore hardness H a1 and Shore hardness H a2 The measurement standards are the same.

[0098] In order 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 comprises a fluoropolymer.

[0101] In some embodiments, the crystallinity of the fluoropolymer as measured by differential scanning calorimetry is X c1 and 0 <X c1 Illustratively, the crystallinity X of the fluoropolymer measured by differential scanning calorimetry is ≦30%. c1 The percentage may be 1%, 5%, 10%, 15%, 20%, 25%, 30%, or a range consisting of any two of the foregoing values.

[0102] In some embodiments, the melting temperature of the fluoropolymer is T m1 °C, 0 <T m1 ≦140° C. Illustratively, 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 foregoing values.

[0103] In some embodiments, the glass transition temperature of the fluoropolymer is T g1 °C, -60 °C ≤ T g1 ≦25° C. Illustratively, 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 foregoing values.

[0104] Therefore, fluoropolymers have a relatively low crystallinity, melting temperature or glass transition temperature, and the greater the flexibility of the fluoropolymer molecular chains, the greater the flexibility of the molecular chain segments, making it easier for adjacent molecular chains to open, allowing the solvent molecules in the electrolyte to enter between the fluoropolymer molecular chains and form a gel-like substance, effectively storing the electrolyte on the surface of the active material and improving the wettability of the active material.

[0105] In some embodiments, the fluoropolymer comprises at least one of the compounds shown in formula (AI) through (AIII).

[0106] The compound represented by formula (AI) is as follows: [ka] In formula (AI), 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 alkyl group, or a substituted or unsubstituted alkoxy group, and R 11 , R 12 , R 13 and R 14At least one of the groups contains a fluorine atom. When substituted, the substituents include 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 preferably a fluorine atom.

[0107] Selectively, 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-C10 alkyl group, or a substituted or unsubstituted C1-C10 alkoxy group.

[0108] Selectively, R 11 , R 12 , R 13 and R 14 each independently comprises a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and R 11 , R 12 , R 13 and R 14 At least one of them contains a fluorine atom.

[0109] In some embodiments, R 11 , R 12 , R 13 and R 14 each independently comprise 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 optionally R 11 , R 12 , R 13 and R 14 each independently includes 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, such as 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 a range consisting of any two of the foregoing numbers.

[0111] In some embodiments, the fluoropolymer comprises at least one of the compounds represented by formula (AI-1) to formula (AI-11): [ka]

[0112] The compound represented by formula (AII) is as follows:

[0113] [ka] In formula (AII), R 11 , R 12 , R 13 and R 14 each independently comprises a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkoxy group, and R 11 , R 12 , R 13 and R 14 At least one of the groups contains a fluorine atom. When substituted, the substituents include 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 preferably a fluorine atom.

[0114] Selectively, 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-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 comprises a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and R 11 , R 12 , R 13 and R 14 At least one of them contains a fluorine atom.

[0116] In some embodiments, R 11 , R 12 , R 13 and R 14 each independently comprise 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 optionally R 11 , R 12 , R 13 and R 14 each independently includes 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, such as 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 a range consisting of any two of the foregoing numbers.

[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 formula (AIII), R 15 includes a single bond, a substituted or unsubstituted alkyl group, and if substituted, the substituent includes a fluorine atom.

[0120] In some embodiments, when substituted, the substituents may include 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.

[0121] Selectively, R 15 includes a single bond, a substituted or unsubstituted C1-C10 alkyl group.

[0122] Selectively, R 15 includes a single bond, a substituted or unsubstituted C1-C3 alkyl group.

[0123] In some embodiments, p is selected from any positive integer from 1 to 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, such as 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 a range consisting of any two of the foregoing numbers.

[0125] In some embodiments, the fluoropolymer comprises at least one of the compounds represented by formula (AIII-1) to formula (AIII-3): [ka]

[0126] Exemplarily, the fluoropolymer includes one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoroethylenepropene 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 (abbreviated as CYTOP).

[0127] Optionally, the fluoropolymer comprises one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoroethylene propene copolymer (FEP), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE).

[0128] The fluoropolymer may be derived from one or more of the following monomers: fluorocyclohexane, fluoroethylene, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropylene, trifluoropropylene, tetrafluoropropylene, and pentafluoropropylene. Alternatively, the fluoropolymer may be derived from at least two of the following monomers: 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 fluoropolymers are all short-chain monomers, which are advantageous for polymerizing to form a linear or short-chain branched structure. This structural type has a low degree of entanglement, which is advantageous for improving the flexibility of the molecular chains, and the molecular chains can be sufficiently spread in the electrolyte, thereby further improving the interfacial properties of the active material.

[0130] In some embodiments, the molecular weight of the swelling polymer is 2×10 5 g / mol to 1.5 × 10 6 g / mol.

[0131] When the molecular weight of the swelling polymer is within the above range, the interaction between the molecular chains is relatively weak, which is favorable for the solvent molecules in the electrolyte to open the molecular chains and enter between them, thereby favoring the active ions to enter the active material through the solvent, realizing smooth and rapid movement of the active ions. For example, the molecular weight of the polymer is 2×10 5 g / mol, 5 × 10 5 g / mol, 8 × 10 5 g / mol, 1×10 6 g / mol, 1.5 × 10 6It may be g / mol or a range consisting of any two of the above values.

[0132] The above polymers are merely examples of structural groups in the main molecular chain, and in the embodiments of the present application, the polymer may be obtained by copolymerizing the above structural groups with small amounts of other types of structural groups (e.g., compounds such as olefin-based compounds, ester-based monomers, nitrile-based monomers, and amide-based monomers).

[0133] [Ether polymer] In some embodiments, the swelling polymer comprises an ether-based polymer.

[0134] In some embodiments, the ether-based polymer is prepared 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. The slope of the elastic modulus G'-loss elastic modulus G'' curve was K1, and 1 <K1<5であり、T m2 ° C. represents the melting temperature of the ether-based polymer. Illustratively, K1 may be 1.01, 1.1, 2, 3, 4, 4.5, 4.8, 4.9, or a range consisting of any two of the above values.

[0135] In some embodiments, the glass transition temperature of the ether-based polymer is T g2 °C, -20 °C ≤ T g2 ≦25°C. For example, 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 values. The ether-based polymer has a certain degree of flexibility at or above its glass transition temperature, which is advantageous for forming a gel-like substance, improves the wetting effect on the electrode sheet, and enhances the cycle characteristics of the battery.

[0136] In some embodiments, the ether-based polymer comprises a compound according to formula (BI): [ka] In formula (BI), R 21 and R 22 each independently comprises a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkoxy group; R 23 includes a single bond, a substituted or unsubstituted methylene group.

[0137] Selectively, R 21 and R 22 each independently comprises a hydrogen atom, a substituted or unsubstituted C1-C10 alkyl group, or a substituted or unsubstituted C1-C10 alkoxy group.

[0138] Selectively, 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.

[0139] Selectively, R 23 includes a single bond, a substituted or unsubstituted C1-C10 methylene group.

[0140] Selectively, R 23 includes a single bond, a substituted or unsubstituted C1-C5 methylene group.

[0141] Exemplarily, the ether-based polymer includes at least one of the compounds represented by formula (BI-1) to formula (BI-8): [ka]

[0142] In some embodiments, the ether-based polymer comprises a compound according to formula (BII): [ka] In formula (BII), R 24 ~R 27each independently comprises a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or an ether group, and R 24 ~R 27 At least one of the groups contains a substituted or unsubstituted alkoxy group or an ether group.

[0143] Selectively, R 24 ~R 27 each 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 an ether group, and R 24 ~R 27 At least one of the groups contains a substituted or unsubstituted C1-C3 alkoxy 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 an ether group, and R 24 ~R 27 At least one of the groups contains a substituted or unsubstituted C1-C2 alkoxy or ether group.

[0146] In some embodiments, the ether-based polymer comprises at least one of the compounds represented by formula (BII-1) to formula (BII-7): [ka]

[0147] When substituted, the substituents may include 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, and the halogen atom may include at least one of a fluorine atom, a bromine atom, and a chlorine atom.

[0148] The above polymers are merely examples of structural groups in the main molecular chain, and in the embodiments of the present application, the polymer may be obtained by copolymerizing the above structural groups with small amounts of other types of structural groups (e.g., compounds such as olefin-based compounds, ester-based monomers, nitrile-based monomers, and amide-based monomers).

[0149] In some embodiments, the degree of polymerization n of the ether-based polymer is selected from any positive integer between 1500 and 25000, such as 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 a range consisting of any two of the foregoing numbers.

[0150] Optionally, the degree of polymerization n of the ether-based polymer is selected from any positive integer between 3,000 and 18,000.

[0151] In some embodiments, the molecular weight of the ether-based polymer is 1.2×10 5 g / mol to 1.0 × 10 6 g / mol.

[0152] Illustratively, 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 It may be g / mol or a range consisting of any two of the above values.

[0153] [Ester polymer] In some embodiments, the swelling polymer comprises an ester-based polymer.

[0154] In some embodiments, the ester-based polymer is formed into a sheet-like structure, and the sheet-like structure is (T m3 A dynamic frequency sweep test was performed at +20°C to obtain the elastic modulus G'-loss elastic modulus G'' curve. The slope of the elastic modulus G'-loss elastic modulus G'' curve was K2, and 1 <K2<5であり、T m3 ° C. represents the melting temperature of the ester-based polymer. Illustratively, K2 may be 1.01, 1.1, 2, 3, 4, 4.5, or a range consisting of any two of the above values.

[0155] In some embodiments, the glass transition temperature of the ester-based polymer is T g3 °C, -20 °C ≤ T g3 ≦25°C. For example, 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 values. The ester-based polymer has a certain degree of flexibility at or above its glass transition temperature, which is advantageous for forming a 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 comprises a compound according to formula (CI): [ka] In formula (CI), R 31 , R 32 and R 33 each independently comprises a hydrogen atom or a substituted or unsubstituted alkyl group; R 34 includes substituted or unsubstituted alkyl groups, or substituted or unsubstituted hydroxyalkyl groups.

[0157] Selectively, R 31 , R 32 and R33 each independently comprises a hydrogen atom or a substituted or unsubstituted C1-C10 alkyl group.

[0158] Selectively, R 31 , R 32 and R 33 each independently comprises a hydrogen atom or a substituted or unsubstituted C1-C8 alkyl group; R 34 includes a substituted or unsubstituted C1-C8 alkyl group, or a substituted or unsubstituted C1-C8 hydroxyalkyl group.

[0159] In some embodiments, R 34 includes a substituted or unsubstituted C1-C6 alkyl group, or a substituted or unsubstituted C1-C6 hydroxyalkyl group.

[0160] In some embodiments, R 31 includes a hydrogen atom or a substituted or unsubstituted methyl group.

[0161] In some embodiments, R 32 and R 33 each independently contains a hydrogen atom.

[0162] In some embodiments, R 34 includes a substituted or unsubstituted C1-C4 alkyl group, or a substituted or unsubstituted C1-C4 hydroxyalkyl group.

[0163] Exemplarily, the ester-based polymer comprises at least one of the compounds represented by formula (CI-1) to formula (CI-15): [ka] [ka]

[0164] In some embodiments, the ester-based polymer comprises a compound according to formula (CII): [ka] In formula (CII), R 35 includes substituted or unsubstituted methylene groups.

[0165] Selectively, R 35 includes substituted or unsubstituted C1-C10 methylene groups.

[0166] Selectively, R 35 includes substituted or unsubstituted C2-C6 methylene groups.

[0167] Selectively, R 35 includes a substituted or unsubstituted C2-C4 methylene group.

[0168] Exemplarily, the ester-based polymer comprises at least one of the compounds represented by formula (CII-1) to formula (CII-5): [ka]

[0169] In some embodiments, the ester-based polymer comprises a compound according to formula (CIII): [ka] In formula (CIII), R 36 , R 37 and R 38 each independently comprises a hydrogen atom or a substituted or unsubstituted C1-C8 alkyl group; R 39 comprises a substituted or unsubstituted C1-C8 alkyl group; Selectively, R 36 , R 37 and R 38 each independently comprises a hydrogen atom or a substituted or unsubstituted C1-C4 alkyl group.

[0170] Exemplarily, the ester-based polymer comprises at least one of the compounds represented by formula (CIII-1) to formula (CIII-5): [ka]

[0171] When substituted, the substituents may include 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, which may include at least one of a fluorine atom, a bromine atom, and a chlorine atom.

[0172] The above polymers are merely examples of structural groups in the main molecular chain, and in the embodiments of the present application, the polymer may be obtained by copolymerizing the above structural groups with small amounts of other types of structural groups (for example, monomers having functional groups such as olefin-based compounds, acrylonitrile-based compounds, and maleic anhydride).

[0173] In some embodiments, the degree of polymerization n of the ester-based polymer is selected from any positive integer between 800 and 20,000, such as 800, 1,000, 1,500, 2,000, 3,000, 4,000, 5,000, 6,000, 7,000, 8,000, 9,000, 10,000, 11,000, 12,000, 13,000, 14,000, 15,000, 16,000, 17,000, 18,000, 19,000, 20,000, or a range consisting of any two of the above numbers.

[0174] In some embodiments, the degree of polymerization n of the ester-based polymer is selected from any positive integer between 1,000 and 15,000.

[0175] In some embodiments, the molecular weight of the ester-based polymer is 1.2×10 5 g / mol to 1.0 × 10 6 g / mol.

[0176] For example, the molecular weight of the ester 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, 1.5 × 10 6 It may be g / mol or a range consisting of any two of the above values.

[0177] [Aldehyde-ketone polymers] In some embodiments, the swelling polymer comprises an aldehyde ketone polymer.

[0178] In some embodiments, the aldehyde ketone polymer is prepared 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 modulus G'' curve. The slope of the elastic modulus G'-loss modulus G'' curve was K3, and 0.8≦K3<5. T m4 °C represents the melting temperature of the aldehyde ketone polymer. Illustratively, K3 may be 0.8, 0.85, 0.9, 1, 1.01, 1.1, 2, 3, 4, 4.5, or a range consisting of any two of the above values.

[0179] In some embodiments, the glass transition temperature of the aldehyde ketone polymer is T g4 °C, -20 °C ≤ T g4 ≦25°C. For example, the glass transition temperature of the aldehyde ketone 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 values. The aldehyde ketone polymer has a certain flexibility at or above its glass transition temperature, which is advantageous for forming a gel-like substance, improves the wetting effect on the electrode sheet, and enhances the cycle characteristics of the battery.

[0180] In some embodiments, the aldehyde ketone polymer comprises a compound according to formula (DI): [ka] In formula (DI), R 41 contains a single bond, a substituted or unsubstituted C1-C6 methylene group, and R 42 includes a hydrogen atom, a substituted or unsubstituted C1-C6 alkyl group.

[0181] Selectively, R 41 includes a single bond, a substituted or unsubstituted C1-C2 methylene group.

[0182] Selectively, R 42 includes a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group.

[0183] In the present embodiment, a single bond means that the group is absent and the atoms on both sides of the group are connected by a single bond, e.g., R 41 is a single bond, R 41 This means that the carbon atoms on both sides of the bond are bonded in the form of a single bond.

[0184] Exemplarily, the aldehyde ketone polymer includes at least one of the compounds represented by formula (DI-1) to formula (DI-6): [ka]

[0185] In some embodiments, the aldehyde ketone polymer comprises a compound according to formula (DII): [ka] In formula (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 r and s are each independently selected from integers of 0 to 5, and at least one of r and s is selected from any positive integer.

[0186] Selectively, 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-C2 hydroxyalkyl group, or a substituted or unsubstituted C1-C2 alkoxy group.

[0187] In some embodiments, the aldehyde ketone polymer comprises at least one of the compounds represented by formula (DII-1) to formula (DII-4): [ka]

[0188] The above polymers are merely examples of structural groups in the main molecular chain, and in the embodiments of the present application, the polymer may be obtained by copolymerizing the above structural groups with small amounts of other types of structural groups (e.g., olefin-based compounds, enol-based compounds, acrylonitrile-based compounds, etc.).

[0189] When the above groups are substituted, the substituents may include 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, which may include at least one of a fluorine atom, a bromine atom, and 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 15,000, such as 500, 800, 1,000, 1,500, 2,000, 3,000, 4,000, 5,000, 6,000, 7,000, 8,000, 9,000, 10,000, 11,000, 12,000, 13,000, 14,000, 15,000, or a range consisting of any two of the foregoing numbers.

[0191] Optionally, the degree of polymerization n of the aldehyde ketone polymer is selected from any positive integer between 500 and 10,000.

[0192] In some embodiments, the molecular weight of the aldehyde ketone polymer is 1.2×10 5 g / mol to 1.0 × 10 6 g / mol.

[0193] Illustratively, the molecular weight of the aldehyde ketone 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, 1.0 × 10 6 It may be g / mol or a range consisting of any two of the above values.

[0194] The relevant parameters of the swollen polymers of the present embodiments can be measured using the following methods.

[0195] The groups of the swollen polymer of the present embodiment can be detected using an infrared spectrophotometer (IR). Specifically, the swollen polymer was measured using a Thermo Nicolet Nexus 670 attenuated total reflectance Fourier transform infrared spectrometer (FTIR-ATR), and then measured in accordance with standard GB / T6040-2002, with the test range as follows: ATR 600-4000 cm -1 , Reproducibility: ±2cm -1 , resolution: 4cm -1 Superior penetration depth of 0.2~0.6μm.

[0196] The structure of the swollen polymer of the present embodiment can be detected using nuclear magnetic resonance (NMR). Specifically, H NMR and C NMR were performed on a Varian Mercury Plus-400 nuclear magnetic resonance instrument at a measurement temperature of 20°C, TMS as an internal standard, CDCl as a solvent, and a proton resonance frequency of 400 MHz.

[0197] The polymer monomer type of the swollen polymer in the embodiment of this application (especially applicable to monomers with a small proportion in the polymer) is measured by a combined decomposition-gas chromatography-mass spectrometry, and the specific measurement steps are as follows: 0.5 mg of sample is accurately weighed and placed in a sample cup, which is then attached to a sample rod and 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 instantly vaporize and enter the gas chromatography column with the carrier gas for separation. Finally, the sample is 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 present embodiment has a meaning known in the art and can be measured using devices and methods known in the art, such as gel permeation chromatography (GPC). The specific test steps are as follows: Take an appropriate amount of sample to be measured (the sample concentration should be 8%-12% opaque), add 20 ml of deionized water, and simultaneously ultrasonicate for 5 minutes (53 KHz / 120 W) to ensure complete dispersion of the sample. Then, measure the sample according to GB / T19077-2016 / ISO 13320:2009 standard.

[0199] The swelling polymer can be disposed in various positions, for example, in the polar sheet, in the separator, etc., and the manner in which the swelling polymer is disposed will be described below.

[0200] In some embodiments, the polar sheets include a swelling polymer. Specifically, the first polar sheet includes a current collector and a film layer disposed on at least one surface of the current collector, the film layer including the swelling polymer and active material particles. The swelling polymer may be disposed only in the first polar sheet, or only in the second polar sheet, or the swelling polymer may be disposed on both the first and second polar sheets. The first polar sheet may be a positive electrode sheet, and the second polar sheet may be a negative electrode sheet, or the first polar sheet may be a negative electrode sheet, and the second polar sheet may be a positive electrode sheet.

[0201] For example, the film layer includes a polymer layer and an active material layer, the polymer layer including a swelling polymer, and the active material layer including active material particles. The active material layer is disposed on at least one surface of a current collector, and the polymer layer is disposed on the surface of the active material layer opposite the current collector. As will be understood, the active material particles and binder are dried on the surface of the current collector to form the active material layer, and the swelling polymer is disposed on the surface of the active material layer opposite the current collector. By disposing in this manner, the swelling polymer is advantageous for trapping the electrolyte on the surface of the active material particles, forming a gradual release point, protecting the active material layer interface while increasing the transport rate of active ions, reducing interfacial side reactions, and improving the high-temperature storage performance and cycle characteristics of the battery cell.

[0202] Specifically, the polar sheet is manufactured as follows.

[0203] Active material particles are added to a solvent to produce an active paste.

[0204] The active paste is applied to the surface of the current collector, and is then dried and hardened to form an active material layer.

[0205] A swelling polymer is applied to the surface of the active material layer to form a polar sheet.

[0206] In another example, the active material particles are multiple and have voids between two adjacent active material particles, and the swelling polymer is distributed in the voids. This configuration can improve the liquid storage capacity of the active material layer, i.e., its ability to confine the electrolyte, thereby improving the reliability and cycle characteristics of the battery cell.

[0207] Specifically, the manufacturing process of one embodiment of the polar sheet includes:

[0208] The swollen polymer is dispersed in a solvent to form a mixed system.

[0209] Active material particles are added to the mixture to produce a paste.

[0210] The paste is applied to the surface of a current collector, and then dried and hardened to form a polar sheet.

[0211] Specifically, the manufacturing process of another embodiment of the polar sheet includes:

[0212] A swelling polymer and active material particles are dispersed in a solvent to produce a paste.

[0213] The paste is applied to the surface of a current collector, and then dried and hardened to form a polar sheet.

[0214] As yet another example, the swelling polymer is distributed on the surfaces of the active material particles, and the swelling polymer is distributed in the voids between the active material particles.

[0215] Specifically, the manufacturing process of one embodiment of the polar sheet includes:

[0216] A swelling polymer and active material particles are dispersed in a solvent to produce a paste.

[0217] The paste is applied to the surface of a current collector, and then dried and cured to form a film layer.

[0218] A swelling polymer is applied to the surface of the film layer to form a polar sheet.

[0219] In another embodiment, the separator includes 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, in which voids exist, 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 swelling polymer may be provided on the surface of the coating layer opposite the substrate.

[0223] The specific distribution position of the swelling polymer may be any one of the above three types, any two of them, or a combination of the above three types.

[0224] In some embodiments, the separator comprises a substrate, the substrate comprises a swelling polymer, the swelling polymer can be the predominant material of the substrate, or the swelling polymer can be mixed with the predominant material of the substrate to form the substrate.

[0225] In yet another embodiment, the swelling polymer may be provided on the polar sheet and the separator, and the specific installation position is as described above, and the description thereof will be omitted here.

[0226] In some embodiments, the battery cell further includes a liquid electrolyte, the liquid electrolyte being located within the electrode assembly.

[0227] Liquid electrolytes have fluidity and can flow more easily around active material particles, improving the transport rate of active ions. In related art, liquid electrolytes typically take several forms within a battery cell: first, they diffuse into the void structure of the electrode assembly, for example, they are located within the voids of the polar sheets and / or separator, and second, they are free within the battery cell. In contrast, the liquid electrolyte of the present embodiment takes several forms: first, they diffuse into the void structure of the electrode assembly, for example, they are located within the voids of the polar sheets and / or separator, and second, they are diffused into the swollen polymer. As a result, the liquid electrolyte of the present embodiment is substantially entirely located within the electrode assembly, and there is essentially no free electrolyte within the battery cell, which significantly improves the usage reliability and cycle characteristics of the battery cell.

[0228] In some embodiments, the battery cell further comprises: 0≦y / V 総孔 Meets ≦15% y is the volume of free electrolyte in the battery cell, expressed in mL; V 総孔 indicates the void volume of the electrode assembly, in mL.

[0229] When calculating a formula, only the numerical value is substituted, not the unit.

[0230] When the battery cell satisfies the above conditions, the content of free electrolyte in the battery cell is extremely small, and even the battery cell contains substantially no free electrolyte, thereby significantly improving the usage reliability and cycle characteristics of the battery cell.

[0231] For example, y / V 総孔 y / V may be 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or a range consisting of any two of the above values. 総孔 If 0, it indicates that the amount of free electrolyte is 0 mL, i.e., there is substantially no free electrolyte in the battery cell.

[0232] The electrode assembly includes 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 volume of the first polar sheet, the void volume of the second polar sheet, and the void volume of the separator. In the embodiments of the present application, the void volume has a meaning known in the art and can be measured using an apparatus and method known in the art, for example, by a gas displacement method, and the void volume is vm, where v represents the apparent volume (i.e., the total volume) and m represents the actual volume.

[0233] In some embodiments, the battery cell has a (m / ρ) / V 総孔 Meets ≥ 80% V 総孔 indicates the void volume of the electrode assembly 52, in mL; m is the difference between the mass of the battery cell before drying and the mass of the battery cell after drying, and is expressed in g.

[0234] ρ indicates the density of the electrolyte, and its unit is g / mL.

[0235] In the present embodiment, m may be understood to mean the total amount of electrolyte in the battery cell. After the electrolyte is injected into the battery cell, the electrolyte mainly exists in several forms: first, located within the pore structure of the polar sheet and / or separator, and second, diffused within the swollen polymer. m can be measured using the following method: a new battery cell is fully discharged to a 0% SOC state of charge, weighed, and the weighed mass is m1. A hole with a diameter of 5 to 8 mm is drilled at a local position on the battery cell, and the battery cell is placed above a container with the hole facing downward and directly above the container, allowing the free electrolyte inside the battery cell to drip into the container below. The battery cell is then left in this state for 3 to 5 hours to allow all the free electrolyte inside to drip into the container. The battery cell is then dried at 60°C to 95°C for 24 to 48 hours, immersed in dimethyl carbonate (DMC) solvent for 12 hours, and then dried at 60°C to 95°C for 24 to 48 hours. The dried battery cell is weighed, and the weighed mass is defined as m2, where m is m1 - m2. For example, the battery cell is dried at 60°C for 5 hours, and then weighed. In the present embodiment, the new battery cell may be a newly delivered battery cell (which has not been used for charge / discharge cycles after formation), or may be a battery cell that has been installed in a power consuming device and has been used for less than 10 cycles.

[0236] In the present embodiment, when there is free electrolyte in the battery cell, the density ρ of the electrolyte can be measured as follows: take a number of battery cells, for example, 10 cells, pour out a predetermined mass of electrolyte, measure the volume of the poured-out electrolyte, and 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 the battery cell satisfies the above conditions, most of the liquid electrolyte is located within the pore structure of the electrode assembly, i.e., the electrode assembly itself has good liquid absorption and retention capabilities, which is beneficial for the transport of active ions and improves the dynamic properties of the battery cell. Although some of the liquid electrolyte can be dispersed in the swollen polymer and liquid is released during the cycle charging and discharging 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 electrolyte can wet the electrode assembly more uniformly, thereby improving the cycle properties of the battery cell.

[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 ≧95%.

[0239] In some embodiments, the battery cell further satisfies 0≦y / Ah≦15%; y is the volume of free electrolyte in the battery cell, expressed in mL; Ah indicates the nominal capacity of the battery cell, expressed in units of Ah.

[0240] When calculating a formula, only the numerical values ​​are substituted into the formula, not the units.

[0241] The volume y (mL) of free electrolyte can be measured using the following method: a new battery cell is fully discharged to 0% SOC, a hole with a diameter of 5 to 8 mm is drilled at a local position on the battery cell, the battery cell is placed above a container with the hole facing downward and directly above the container, and the free electrolyte inside the battery cell drips into the container below. The battery cell is left in this state for 3 to 5 hours until all the free electrolyte inside drips into the container, and the volume of the electrolyte inside the container is then measured to obtain y. In this embodiment, the new battery cell may be a battery cell that has just been shipped (and has not been used for any charge-discharge cycles since formation), or a battery cell that has been installed in a power-consuming device and has been used for fewer than 10 cycles.

[0242] When the battery cell satisfies the above conditions, the content of free electrolyte in the battery cell is extremely small, and even the battery cell contains substantially no free electrolyte, thereby significantly improving the usage reliability and cycle characteristics of the battery cell.

[0243] For example, y / Ah may be 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or a range consisting of any two of the above values. y / Ah of 0 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, the battery cell is subjected to a linear sweep vibration test, and then charged to 100% SOC; a hole is drilled in the battery cell, and the hole is positioned at the lowest vertical position; and the volume of electrolyte flowing out of the battery cell is recorded as M1, where 0 mL≦M1≦0.5 mL, and optionally, M1 is 0 mL; where: The vibration direction of the linear sweep vibration test is simple harmonic motion up and down. The vibration frequency of the linear sweep vibration test is 10Hz to 55Hz. The maximum acceleration for linear sweep vibration testing is 30 m / s 2 and The number of sweep cycles in the linear sweep vibration test was 10. The vibration time for the linear sweep vibration test is 3 hours.

[0245] In the related art, during use, a battery cell may experience vibrations or other phenomena due to the action of external forces. The electrolyte located in the electrode assembly may detach from the electrode assembly under the action of vibration, forming free electrolyte. The free electrolyte in the battery cell may leak, causing corrosion of the battery cell and posing risks such as battery cell failure. In embodiments of the present application, the battery cell is subjected to a static and vibration treatment to effectively collect and discharge the liquid electrolyte inside the battery cell, thereby more accurately determining whether liquid electrolyte is present between the battery cell housing and the electrode assembly and determining the free electrolyte content. When the battery cell of the present application satisfies the above conditions, the free electrolyte content within the battery cell is extremely low, or even substantially free of free electrolyte, thereby significantly improving the usage reliability and cycle characteristics of the battery cell.

[0246] Illustratively, M1 may be 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 a range consisting of any two of the above values. If M1 is 0 mL, it indicates that the amount of free electrolyte is 0, that is, the battery cell has substantially no free electrolyte inside after the linear sweep vibration test.

[0247] In some embodiments, after the battery cell is subjected to the vibration test, the housing is removed, the electrode assembly is taken out, and a pressing test is performed. The volume of the electrolyte flowing out of the electrode assembly is recorded as M2 (the pressing device is empty, and a measuring balance and an electrolyte collecting container are placed at the bottom). 0 mL≦M2≦0.5 mL, and optionally, M2 is 0 mL; where: The pressing direction in the pressing test is perpendicular to the thickness direction of the electrode assembly 52. The pressure level in the compression test is 0.35 MPa.

[0248] In the related art, a battery cell may be subjected to external pressure during use, and the electrolyte located in the electrode assembly may detach from the electrode assembly under pressure, forming free electrolyte. The free electrolyte in the battery cell may leak, causing corrosion of the battery cell and posing risks such as battery cell failure. In embodiments of the present application, a pressure test is performed on the battery cell to effectively force the liquid electrolyte inside the battery cell to flow out, thereby more accurately determining whether liquid electrolyte exists between the battery cell housing and the electrode assembly and determining the free electrolyte content. If the battery cell of the present application satisfies the above conditions, the free electrolyte content in the battery cell is extremely low, or even substantially free of free electrolyte, after pressing, thereby significantly improving the usage reliability and cycle characteristics of the battery cell.

[0249] For example, M2 may be 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 a range consisting of any two of the above values. If M2 is 0 mL, it indicates that the amount of free electrolyte is 0, that is, the battery cell has substantially no free electrolyte inside after the compression test.

[0250] In some embodiments, a voltage of 200V is supplied to the battery formation circuit 4h, and the absolute value of the temperature change of the battery cell is ≦4°C.

[0251] For example, if a 200V current circuit is formed by connecting the negative terminal of a battery cell to the inside of the outer case, the temperature fluctuation range of the battery cell will be 4°C or less within 4 hours, and there will be no malfunctions such as fire or explosion. In particular, when the free electrolyte y=0, the temperature fluctuation range is small, greatly improving the reliability of the battery cell.

[0252] [Positive electrode sheet] The battery cell includes a positive electrode sheet, the positive electrode sheet including a positive electrode current collector and a positive electrode film layer disposed on the positive electrode current collector, the positive electrode film layer including a positive electrode active material and a swelling polymer.

[0253] In some embodiments, the positive electrode film layer includes a polymer layer containing a swollen polymer and a positive electrode active material layer containing positive electrode active material particles, the positive electrode active material layer being disposed on at least one surface of a positive electrode current collector, and the polymer layer being disposed on the surface of the positive electrode active material layer opposite the positive electrode current collector.

[0254] In some embodiments, the positive electrode active material particles are plural, and there is a gap between two adjacent positive electrode active material particles, the swelling polymer is distributed in the gap, and the positive electrode active material particles and the swelling polymer are located in the same film layer.

[0255] As an example, the positive electrode current collector has two surfaces that face each other in the thickness direction of the positive electrode current collector, and the positive electrode active material layer is provided on either one or both of the two facing surfaces of the positive electrode current collector.

[0256] The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material may 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 a lithium-containing positive electrode active material and a sodium-containing positive electrode active material, such as at least one of a lithium-containing phosphate compound, a lithium-containing transition metal oxide, a sodium-containing phosphate compound, and a sodium-containing transition metal oxide material.

[0257] For example, the general formula of an olivine-type phosphate active material (lithium-containing phosphate compound) is Li x A y Me a M b P 1-c X c Y zwhere 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 includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes 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 includes one or more of S, Si, Cl, B, C, and N; and Y includes 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] Exemplary examples include lithium transition metal oxides (layered materials, such as ternary, lithium / sodium nickelate, lithium / sodium cobaltate, lithium / sodium manganate, lithium-rich layered, and rock salt phase layered materials). The general formula for layered structure positive electrode active materials is Li x A y Ni a Co b Mn c M (1-a-b-c) Y z where 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 includes one or more of Na, K, and Mg; M includes 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 includes one or more of O and F. Optionally, y=0. Specifically, the layered structure positive electrode active material is lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium manganese oxide (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 One or more of O2 (NCM811) and NCA may be included.

[0259] During the charge and discharge process, the battery cell loses and consumes active ions, such as Li, resulting in different molar contents of Li discharged from the battery cell when it is in different states. In the description of the positive electrode active material in the embodiments of this application, the molar content of Li refers to the initial state of the material, i.e., the state before the material is added. When the positive electrode active material is applied to a battery system and charge and discharge cycles are performed, the molar content of Li may change.

[0260] In the description of the positive electrode active material in the embodiments of the present application, the molar content of oxygen (O) is merely a theoretical value, and the release of lattice oxygen brings about a change in the molar content of oxygen (O), and the molar content of oxygen (O) actually fluctuates.

[0261] In the embodiment of the present application, the modified compound may be doped or coated. The doping modification may involve adding a doping element, such as a transition metal, to the compound, while the 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 particle.

[0262] In some embodiments, the mass content of the swelling polymer is ≦5%, preferably 0.05% to 1%, relative to the total mass of the positive electrode film layer. When the mass content of the swelling polymer is within this 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 in the same layer as the positive electrode active material particles or in a different layer. "Location in a different layer" refers to the swelling polymer being located in a polymer layer and the positive electrode active material particles being located in a positive electrode active material layer. Optionally, the swelling polymer is located in the same layer as the positive electrode active material particles.

[0263] Illustratively, the mass content of the adsorbed polymer 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%, 2.10%, 2.11%, 2.12%, 2.13%, 2.14%, 2.15%, 2.16%, 2.17%, 2.18%, 2.19%, 2.20%, 2.21%, 2.22%, 2.23%, 2.24%, 2.25%, 2.26%, 2.27%, 2.28%, 2.29%, 2.30%, 2.31%, 2.32%, 2.33%, 2.34%, 2.35%, 2.36%, 2.37%, 2.38%, 2.39%, 2.40%, 2.42%, 2.45%, 2.48%, 2.50%, 2.55%, 2.58%, 2.60%, 2 %, 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 the present application, the polymer mass content has the meaning known in the art and can be measured using devices and methods known in the art, for example, using thermogravimetric analysis (TGA) according to JYT014-1996. Specifically, a mass-temperature curve (TG curve) is created based on the mass loss during the heating process of the polar sheet, and the corresponding weight loss (i.e., the total mass of the polymer in the polar sheet) is read based on the polymer decomposition temperature, and the polymer mass content is calculated accordingly. The measurement can be performed in a nitrogen atmosphere using the following heating program: 5°C / min, RT to 500°C, 10°C / min, 500 to 600°C, 10 minutes at 600°C, and then stop.

[0265] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. The metal foil may be, for example, an aluminum foil or an 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 alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. 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 optionally further include a positive electrode conductive agent. The present embodiment does not particularly limit the type of positive electrode conductive agent. 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 percentage of the positive electrode conductive agent is 5% or less with respect to the total mass of the positive electrode active material layer.

[0267] In some embodiments, the positive electrode active material layer may optionally further include a positive electrode binder. The present embodiment does not particularly limit the type of positive electrode binder. For example, the positive electrode binder may include one or more combinations selected from the group consisting of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene ternary copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ternary copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic resin. In some embodiments, the mass percentage of the positive electrode binder is 5% or less, relative to the total mass of the positive electrode active material layer. The crystallinity of the positive electrode binder is higher than that of the fluoropolymer of the present embodiment.

[0268] The positive electrode active material layer is typically formed by applying a positive electrode paste to a positive electrode current collector, drying it, and cold pressing it. The positive electrode paste is typically formed by dispersing the positive electrode active material, optionally a swelling polymer, optionally a conductive agent, optionally a binder, and any other components in a solvent and stirring the mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP). The production of the positive electrode sheet is not limited to the above method, and the above-mentioned production methods may also 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 disposed 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 a negative electrode film layer is disposed on either or both of the opposing surfaces of the negative electrode current collector.

[0271] In some embodiments, the negative electrode film layer includes a polymer layer containing a swollen polymer and a negative electrode active material layer containing negative electrode active material particles, the negative electrode active material layer being disposed on at least one surface of a negative electrode current collector, and the polymer layer being disposed on the surface of the negative electrode active material layer opposite the negative electrode current collector.

[0272] In some embodiments, the negative electrode active material particles are plural, and there is a gap between two adjacent negative electrode active material particles, the swelling polymer is distributed in the gap, and the negative electrode active material particles and the swelling polymer are located in the same film layer.

[0273] The negative electrode active material may be any negative electrode active material for battery cells known in the art. Examples of the negative electrode active material include, but are not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include at least one of silicon elemental, silicon oxide, silicon carbon composite, silicon nitrogen composite, and silicon alloy materials. Tin-based materials may include at least one of tin elemental, tin oxide, and tin alloy materials.

[0274] In some embodiments, the mass content of the swelling polymer is ≦5%, preferably 0.5% to 3.5%, relative to the total mass of the negative electrode film layer. When the mass content of the swelling polymer is within this 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 in the same layer as the negative electrode active material particles or in a different layer. "Location in a different layer" refers to the swelling polymer being located in a polymer layer and the negative electrode active material particles being located in a negative electrode active material layer. Optionally, the swelling polymer is located in the same layer as the negative electrode active material particles.

[0275] Illustratively, the mass content of the adsorbed polymer 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%, 2.10%, 2.11%, 2.12%, 2.13%, 2.14%, 2.15%, 2.16%, 2.17%, 2.18%, 2.19%, 2.20%, 2.21%, 2.22%, 2.23%, 2.24%, 2.25%, 2.26%, 2.27%, 2.28%, 2.29%, 2.30%, 2.31%, 2.32%, 2.33%, 2.34%, 2.35%, 2.36%, 2.37%, 2.38%, 2.39%, 2.40%, 2.42%, 2.45%, 2.48%, 2.50%, 2.55%, 2.58%, 2.60%, 2 %, 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 include a negative electrode conductive agent. The present embodiment does not particularly limit the type of negative electrode conductive agent. For 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% with respect to the total mass of the negative electrode active material layer.

[0277] In some embodiments, the negative electrode active material layer may optionally further include a negative electrode binder. The present embodiment does not particularly limit the type of negative electrode binder. For example, the negative electrode binder may include at least one of styrene butadiene rubber (SBR), water-soluble unsaturated resin (SR-1B), water-based 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% relative to the total mass of the negative electrode active material layer.

[0278] In some embodiments, the negative electrode active material layer may optionally further contain other additives. For example, the other additives may include a thickener, such as sodium carboxymethyl cellulose (CMC), a PTC thermistor material, etc. In some embodiments, the weight percentage of the other additives relative to the total weight of the negative electrode active material layer is ≦2%.

[0279] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. The metal foil can be, for example, a copper foil. The composite current collector can 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 can include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymer substrate layer can 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 typically formed by applying a negative electrode paste to a negative electrode current collector, drying it, and cold pressing it. The negative electrode paste is typically formed by dispersing the negative electrode active material, optionally a swelling polymer, optionally a conductive agent, optionally a binder, and other optional additives in a solvent and stirring the mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water. The production of the negative electrode sheet is not limited to the above method, and the above-mentioned production methods may also be used.

[0281] The negative electrode sheet does not exclude additional functional layers other than the negative electrode active material layer. For example, in certain embodiments, the negative electrode sheet of the present application further includes a conductive primer layer (e.g., composed 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 application further includes a protective layer covering the surface of the negative electrode active material layer.

[0282] [Separator] The battery cell includes a separator.

[0283] In some embodiments, the separator comprises a substrate.

[0284] In some embodiments, the separator includes a substrate and a coating layer disposed on at least one surface of the substrate.

[0285] For example, the substrate generally has a porous structure, in which voids exist, 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 swelling polymer may be provided on the surface of the coating layer opposite the substrate.

[0288] The specific distribution position of the swelling polymer may be any one of the above three types, any two of them, or a combination of the above three types.

[0289] The present embodiment does not particularly limit the material of the substrate, and any known substrate with good chemical and mechanical stability can be selected, such as at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The substrate can be a single-layer film or a multi-layer composite film. When the substrate is a multi-layer composite film, the materials of each layer can 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 can further include a filler. Further, the filler can include at least one of inorganic particles and organic particles. The swelling polymer can be distributed within the coating layer.

[0291] In some embodiments, the swelling polymer may be provided on the surface of the coating layer opposite the substrate.

[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, and can further improve the heat resistance of the separator.

[0293] The inorganic particles have high thermal stability and are resistant to decomposition. Optionally, the inorganic particles include at least one of inorganic particles having a dielectric constant of 5 or more, inorganic particles having ionic conductivity but not storing ions, and inorganic particles capable of generating an electrochemical reaction.

[0294] Optionally, the inorganic particles having a dielectric constant of 5 or more 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, magnesium aluminum silicate, magnesium lithium silicate, magnesium sodium silicate, bentonite, hectorite, zirconium titanate, barium titanate, Pb(Zr,Ti)O3 (abbreviated as PZT), Pb 1-m La m Zr 1-n Ti n O3 (abbreviated as PLZT, 0 <m<1、0<n<1)、Pb(Mg3Nb 2 / 3 The coating composition includes at least one of the following: )O3-PbTiO3 (abbreviated as PMN-PT), and each modified inorganic particle. Optionally, the modification method of each inorganic particle may be chemical and / or physical. Chemical modification methods include coupling agent modification (e.g., using a silane coupling agent, titanate coupling agent, etc.), surfactant modification, graft polymer modification, etc. Physical modification methods may include mechanical 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, selecting coupling agents, surface active materials, or polymer-modified inorganic particles with specific functional groups can further improve the wetting properties of the coating layer with the electrolyte and help improve the adhesive strength between the coating layer and the substrate.

[0295] Alternatively, inorganic particles that are ionically conductive but do not store ions include Li3PO4, lithium titanium phosphate, Li x1 Ti y1 (PO4)3, Lithium titanium aluminum phosphate Li 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, and 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 overcharge abuse, thermal abuse, etc., the organic particles can further melt, and are sucked into the pores of the base material 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 polyethylene particles, polypropylene particles, polystyrene particles, melamine resin particles, phenolic resin particles, polyester particles (e.g., polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate), polyimide particles, polyamideimide 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 adhesive properties can be selected. As an example, the binder includes at least one of a water-soluble acrylic resin (e.g., a homopolymer of acrylic acid, methacrylic acid, or sodium acrylate monomer or a copolymer with other comonomers), polyvinyl alcohol, an isobutylene-maleic anhydride copolymer, and a polyacrylamide.

[0299] Optionally, the content of binder in the coating layer is <30% based on the weight of the coating layer.

[0300] [Electrolyte] In some embodiments, the battery cell includes an electrolyte that is entrapped in a swollen polymer and located on the surface of the active material particles, resulting in no free electrolyte.

[0301] During the charge and discharge process of the battery cell, active ions are inserted and removed between the positive electrode sheet and the negative electrode sheet, and the electrolyte serves to conduct the active ions between the positive electrode sheet and the negative electrode sheet. The present application does not particularly limit the type of electrolyte, and it can be selected according to actual needs.

[0302] The electrolyte solution includes an electrolyte salt and a solvent, and the types of the electrolyte salt and the solvent are not specifically limited and can be selected according to actual needs.

[0303] When the battery cell of the present application is a lithium-ion battery, for example, the electrolyte salt may include at least one of lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPOF), lithium difluorobisoxalatophosphate (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0304] When the battery cell of the present application is a sodium-ion battery, for example, the electrolyte salt may include at least one of sodium hexafluorophosphate (NaPF), sodium tetrafluoroborate (NaBF), sodium perchlorate (NaClO), sodium hexafluoroarsenate (NaAsF), sodium bisfluorosulfonylimide (NaFSI), sodium bistrifluoromethanesulfonylimide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalatoborate (NaDFOB), sodium bisoxalatoborate (NaBOB), sodium difluorophosphate (NaPOF), sodium difluorobisoxalatophosphate (NaDFOP), and sodium tetrafluorooxalatophosphate (NaTFOP), but is not limited thereto.

[0305] By way of example, the solvent may include, but is not limited to, one or more of 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 solution optionally further contains additives. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and additives that can improve specific battery performance, such as an additive that improves the overcharge characteristics of the battery, an additive that improves the high-temperature characteristics of the battery, or an additive that improves the low-temperature power output characteristics of the battery.

[0307] In some embodiments, the positive electrode sheet, separator, and negative electrode sheet can be fabricated into an electrode assembly via a winding and / or lamination process.

[0308] In some embodiments, the battery cell may include a housing material that is used to encapsulate the electrode assembly and the electrolyte.

[0309] In some embodiments, the battery cell exterior may be a hard case such as a hard plastic case, an aluminum case, or a steel case. The battery cell exterior may be a soft pack such as a pouch-type soft pack. The soft pack may be made of plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0310] In some embodiments, the positive electrode sheet, separator, and negative electrode sheet can be fabricated into an electrode assembly via a winding or lamination process.

[0311] The present application does not particularly limit the shape of the battery cell, and it may be cylindrical, rectangular, or any other shape. Figure 1 shows a battery cell 5 with a rectangular structure as an example.

[0312] In some embodiments, as shown in FIGS. 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 storage cavity surrounded by the bottom plate and side plates. The housing 51 has an opening communicating with the storage cavity, and the cover plate 53 is used to cover the opening and seal the storage cavity. The positive electrode sheet, the negative electrode sheet, and the separator may form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is sealed in the storage cavity. An electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 included in the battery cell 5 may be one or more and can be adjusted as needed.

[0313] The manufacturing method of the battery cell of the present application is well 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 the positive electrode sheet, the separator, and the negative electrode sheet through a winding process or a stacking process. The electrode assembly can then be placed in a housing, dried, and then injected with an electrolyte. The battery cell can then be obtained through processes such as vacuum sealing, standing, chemical conversion, and shaping.

[0314] In some embodiments of the present application, the battery cells of the present application can be assembled into a battery module, and the battery module may include multiple battery cells, the specific number of which can be adjusted according to the application and capacity of the battery module.

[0315] FIG. 3 is a schematic diagram of an example battery module 4. As shown in FIG. 3, in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length of the battery module 4. Of course, any other arrangement may also be used. The plurality of battery cells 5 can also be fastened together using fasteners.

[0316] Optionally, the battery module 4 may further include an outer case having an accommodating space for accommodating the plurality of battery cells 5.

[0317] In some embodiments, the 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 embodiments of the present application.

[0319] 4 and 5 are schematic diagrams of an example battery pack 1. As shown in FIGS. 4 and 5, the battery pack 1 may include a battery case and a plurality of battery modules 4 installed in the battery case. The battery case includes an upper housing 2 and a lower housing 3, and the upper housing 2 is used to cover the lower housing 3 and forms a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery case in any manner.

[0320] power consumption equipment According to a second aspect, the present application provides a power consuming device including at least one of a battery cell, a battery module, or a battery pack according to the present application. The battery cell, the battery module, and the battery pack may be used as a power source for the power consuming device or as an energy storage element for the power consuming device. The power consuming device may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), a train, a ship, a satellite, an energy storage system, etc. In some embodiments, the battery cell includes a fill hole for injecting electrolyte, and when the battery cell is applied to the power consuming device, the fill hole is located at the bottom along the vertical direction of the battery cell. Because the amount of free electrolyte in the battery cell is very small, or even absent, providing the fill hole at the bottom along the vertical direction of the battery cell can also improve the reliability of the battery cell and the power consuming device.

[0321] A power consuming device can be configured as a battery cell, a battery module, or a battery pack depending on its usage conditions. FIG. 6 is a schematic diagram of an example power consuming device. The power consuming device 6 may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the power consuming device, a battery pack 1 or a battery module may be used. Another example power consuming device may be a mobile phone, a tablet computer, a laptop computer, etc. The power consuming device is generally required to be lightweight and thin, and can use a battery cell as a power source.

[0322] Example Examples of the present application are described below. The examples described below are illustrative and are intended only to explain the present application and should not be understood as limitations on the present application. If specific techniques or conditions are not specified in the examples, they will be carried out according to techniques or conditions described in literature in the field or according to product specifications. If the manufacturer of the reagents or equipment used is not specified, they are all commercially available general products.

[0323] Example 1: Manufacture of a lithium-ion battery (1) Manufacturing of positive electrode sheet: Swelling polymer, positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive carbon black, and binder polyvinylidene fluoride (PVDF) are mixed with N-methylpyrrolidone (NMP) to produce a positive electrode paste. The swelling polymer in the positive electrode paste, LiNi 0.8 Co 0.1 Mn 0.1The mass ratio of O2 (NCM811), conductive carbon black, and PVDF was 0.2:97.3:2:0.5. The positive electrode paste was applied to an aluminum foil current collector, dried at 85°C, and then cold-pressed. The resulting sheet was then trimmed, cut, and slit, and then dried under vacuum at 85°C for 4 hours to produce a positive electrode sheet. The polyvinylidene fluoride (PVDF) binder had a crystallinity of 48%, a melting temperature of 164°C, and a glass transition temperature of 39°C.

[0324] (2) Manufacturing of negative electrode sheet: The negative electrode paste is prepared by adding the swelling polymer, the negative electrode active material artificial graphite, the conductive agent carbon black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) in a weight ratio of 2.5:94.9:2:0.5:0.1 to deionized water and mixing uniformly. The negative electrode paste is applied to a copper foil current collector and dried at 85°C. After that, the foil is cold pressed, trimmed, cut, and slit, and then dried under vacuum at 120°C for 12 hours to produce a negative electrode sheet.

[0325] (3) Electrolyte production: In an environment with a water content of less than 10 ppm, the 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, and then the resulting solvent is mixed with lithium salt LiPF6 to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0326] (4) Lithium-ion battery manufacturing: The positive electrode sheet, separator, and negative electrode sheet are stacked in this order using a 16 μm polyethylene (PE) film as a separator. The separator serves to separate the positive and negative electrode sheets, and then the stack is wound up to obtain an electrode assembly. The electrode assembly is placed in a housing and dried. After that, an electrolyte is injected, and the assembly is vacuum sealed, left to stand, chemically formed, and shaped to obtain a lithium-ion battery.

[0327] Examples 2 to 4 Lithium ion batteries were produced in the same manner as in Example 1, except that Examples 2 to 4 differed from Example 1 in that the amount of swelling polymer used was adjusted.

[0328] Examples 5 to 9 Lithium ion batteries were produced in the same manner as in Example 1, except that Examples 5 to 9 differed from Example 1 in that the type of swelling polymer was adjusted.

[0329] Examples 10 and 11 Lithium ion batteries were produced in the same manner as in Example 1, except that Examples 10 and 11 differed from Example 1 in that the type of swelling polymer was adjusted.

[0330] Comparative Example 1 A lithium ion battery was produced in the same manner as in Example 1, except that Comparative Example 1 did not use a swelling polymer.

[0331] (1) Manufacturing of positive electrode sheet: Positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive carbon black, and binder polyvinylidene fluoride (PVDF) are mixed with N-methylpyrrolidone (NMP) to produce a positive electrode paste. 0.8 Co 0.1 Mn 0.1 The mass ratio of O2 (NCM811), conductive carbon black, and PVDF was 97.5:2:0.5. The positive electrode paste was applied to an aluminum foil current collector, dried at 85°C, cold pressed, trimmed, cut, and slit, and then dried under vacuum at 85°C for 4 hours to produce a positive electrode sheet.

[0332] (2) Manufacturing of negative electrode sheet: The negative electrode paste is prepared by adding the negative electrode active material artificial graphite, the conductive agent carbon black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) in a weight ratio of 94.9:2:0.5:2.6 to deionized water and mixing uniformly. The negative electrode paste is applied to a copper foil current collector and dried at 85°C. After that, the foil is cold pressed, trimmed, cut, and slit, and then dried under vacuum at 120°C for 12 hours to produce a negative electrode sheet.

[0333] Comparative Example 2 A lithium ion battery was produced in the same manner as in Example 1, except that Comparative Example 2 differed from Example 1 in that the type of swelling polymer was adjusted.

[0334] Exam section 1. Battery cell capacity retention rate test Taking Example 1 as an example, the fabricated lithium ion battery is first determined and its C0 is measured. After discharging at 1C to 2.8V, it is left standing for 5 minutes, then charged at a constant current of 1 / 3C to 4.25V, and then charged at a constant voltage of 4.25V to a current of 0.05C. After leaving standing for 5 minutes, it is discharged at 1C to 2.8V. The capacity released at this time is defined as C0.

[0335] The battery capacity retention test was carried out as follows: A battery corresponding to Example 1 was charged to 4.25 V at room temperature using an equivalent 1.2 C step charge (charged to 0.5 C 0 Ah at a constant current of 1.2 C, then to 0.3 C 0 Ah at a constant current of 0.87 C, and finally to V2 at a constant current of 1 / 3 C), then further charged to a constant voltage of 4.25 V at a current of 0.05 C, allowed to stand for 5 minutes, and further discharged to 2.8 V at 0.33 C. The resulting capacity was designated as the initial capacity C0, and the initial clamping force of the cell was set to 12,000 N. The above steps were repeated for the same battery, and the discharge capacity Cn of the battery after n cycles was recorded. The battery capacity retention rate after each cycle was calculated as Pn=Cn / C0*100%, and the values ​​of 250 points P1, P2...P250 were taken as the ordinate and the corresponding cycle number as the abscissa, to obtain a curve of battery capacity retention rate vs. cycle number for the polymer of Example 1.

[0336] In the test process, the first cycle corresponds to n = 1, the second cycle corresponds to n = 2, ... the 250th cycle corresponds to n = 250. In Table 3, the battery capacity retention rate data for 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 other Examples were the same as above.

[0338] 2. Battery cell DC resistance test Taking Example 1 as an example, the fabricated lithium ion battery is first determined and its C0 is measured. After discharging at 1C to 2.8V, it is left standing for 5 minutes, then charged at a constant current of 1 / 3C to 4.25V, and then charged at a constant voltage of 4.25V to a current of 0.05C. After leaving standing for 5 minutes, it is discharged at 1C to 2.8V. The capacity released at this time is defined as C0.

[0339] The battery DC resistance test procedure was as follows: At 25°C, a battery cell corresponding to Example 1 was charged to 4.25V using an equivalent 1.2C step charge (charged to 0.5C 0Ah at a constant current of 1.2C, then charged to 0.3C 0Ah at a constant current of 0.87C, and finally charged to V2 at a constant current of 1 / 3C). It was then charged to a constant voltage of 4.25V at a current of 0.05C, allowed to stand for 5 minutes, and the voltage V1 was recorded. It was then discharged at 1 / 3C for 30 seconds, and the voltage V2 was recorded. The battery's internal resistance DCR1 after the first cycle was calculated using the formula (V2 - V1) / 1 / 3C. The initial clamping force of the battery cell was set to 12,000 N. The same battery was subjected to the same procedure, and the internal resistance DCRn of the battery after n cycles (n=1, 2, 3...250) was recorded. The 250 values ​​of DCR1, DCR2, DCR3...DCR250 were taken as the ordinate and the corresponding cycle number as the abscissa to obtain a curve of the battery discharge DCIR vs. cycle number for the polymer of Example 1. During the test, the first cycle corresponds to n=1, the second cycle corresponds to n=2, and the 250th cycle corresponds to n=250. In Table 3, the internal resistance increase ratio of the battery of Example 1 = (DCRn-DCR1) / DCR1*100%.

[0340] The test procedures for Comparative Example 1 and the other Examples are the same as above. The data in Table 3 are 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] In Table 1, 85% vinyl acetate + 15% ethylene in the monomers indicates that the mass content of vinyl acetate is 85% and the mass content of ethylene is 15% relative to the total mass of the monomers. Changes in polymerization conditions (polymerization temperature, polymerization pressure, etc.) can cause changes in properties such as glass transition temperature, even for polymers formed using the same type of monomers.

[0344] [Table 2]

[0345] In Table 2, the swelling polymer content of the positive electrode sheet being 0.2% means that the mass content of the swelling polymer is 0.2% with respect to the total mass of the positive electrode film layer.

[0346] The amount of swelling polymer added to the positive electrode sheet being 0.0% indicates that no swelling polymer was added to the positive electrode film layer.

[0347] [Table 3]

[0348] As can be seen from Table 3, the positive electrode sheet and the negative electrode sheet of Comparative Example 1 did not contain a swelling polymer. During the cycling process of the lithium ion battery, the volume of the lithium ion battery changes, which may cause the electrolyte in the electrode assembly to be pushed out, resulting in leakage problems. This increases the risk of lithium dendrites appearing, and reduces the usage reliability and cycling characteristics of the lithium ion battery.

[0349] In Comparative Example 2, polyethylene oxide is added to the polar sheet, but the swelling ability of the polymer is low, and not only is the liquid retention efficiency low, but the high resistance itself reduces the dynamic characteristics of the battery.

[0350] In the present embodiment, by adding a swelling polymer to at least one of the positive electrode sheet, the negative electrode sheet, and the separator, the swelling polymer can confine the electrolyte and release the electrolyte during charging and discharging, improving the liquid retention ability of the electrode assembly and the wetting ability of the electrolyte to the electrode assembly, thereby improving the usage reliability and cycle characteristics of the lithium ion battery.

[0351] While exemplary embodiments have been shown and described, those skilled in the art will understand that the above embodiments should not be construed as limitations on the present application, and that changes, substitutions, and alterations can be made to the embodiments without departing from the spirit, principles, and scope of the present application.

Claims

1. A battery cell including an electrode assembly, the electrode assembly including 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 including a swelling polymer, the swelling polymer having a viscosity of 300%≦m ２ / m １ ≦10000%, m ３ / m ２ ≦50% is satisfied, where: A gel film is produced from the swollen polymer, and the mass of the gel film is m １ g, 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 allowed to stand at 25°C for 7 days to obtain a first swollen gel film, and the mass of the first swollen gel film was m ２ g, The first swollen gel film is 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 is m ３ g of the battery cell.

2. 500%≦m ２ / m １ 5000%. The battery cell of claim 1 .

3. The swelling polymer is The gel film is T ｍ A dynamic frequency sweep test is performed at +20°C to obtain a G'-G" curve, the slope of which is K, and the T ｍ is the condition (1) that represents the melting temperature of the gel film; The swollen polymer has a crystallinity of Xc as measured by differential scanning calorimetry, where Xc is 0<Xc≦30%; The glass transition temperature of the swollen polymer is T ｇ and T ｇ Condition (2) where the temperature is ≦25° C.; The battery cell according to claim 1 or 2, wherein at least two of the following conditions (3) are satisfied: the elastic modulus of the gel film is E, where E≦1 MPa; and the breaking elongation of the gel film is ε, where ε≧100%.

4. The gel film is added to a predetermined electrolyte solution and allowed to stand at 25° C. for ≥ 24 hours to obtain a second swollen gel film, the predetermined electrolyte solution being dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and lithium hexafluorophosphate (LiPF). ６ wherein the masses of the dimethyl carbonate, the ethyl methyl carbonate, and the ethylene carbonate are the same, and the lithium hexafluorophosphate LiPF ６ The molar amount of is 1 mol / L, 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 have a thickness of 0≦H ａ２ / H ａ１ ≦0.5 and 0≦H ａ２ The battery cell according to any one of claims 1 to 3, wherein the resistance is ≦45.

5. 0≦H ａ２ / H ａ１ ≦0.45, and / or 20≦H ａ１ 5. The battery cell of claim 4, wherein:

6. The swelling polymer comprises a fluoropolymer, and the fluoropolymer comprises at least one of the compounds represented by formula (AI) to formula (AIII), 【Chemistry 1】 In formula (AI) and formula (AII), R １１ , R １２ , R １３ and R １４ each independently comprises a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and R １１ , R １２ , R １３ and R １４ at least one of the groups contains a fluorine atom, and when substituted, the substituents contain 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; 【Chemistry 2】 In formula (AIII), R １５ comprises a single bond, a substituted or unsubstituted C1-C3 alkyl group, and if substituted, the substituents comprise 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; p is selected from any positive integer from 1 to 3; The battery cell according to any one of claims 1 to 5, wherein the degree of polymerization n of the fluoropolymer is selected from any positive integer of 5,000 to 20,000.

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 formula (BI), R ２１ and R ２２ each independently comprises a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; R ２３ comprises a substituted or unsubstituted C1-C5 alkylene group; 【Chemistry 4】 In formula (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 an ether group, and R ２４ ~R ２７ at least one of which contains a substituted or unsubstituted C1-C3 alkoxy or ether group; 7. The battery cell according to claim 1, wherein the degree of polymerization n of the ether-based polymer is selected from the positive integers of 1,500 to 25,000.

8. The swelling polymer comprises an ester-based polymer, and the ester-based polymer comprises a compound represented by formula (CI) to a compound represented by formula (CIII), 【Transformation 5】 In formula (CI), R ３１ , R ３２ and R ３３ each independently comprises a hydrogen atom or a substituted or unsubstituted C1-C8 alkyl group; R ３４ comprises a substituted or unsubstituted C1-C8 alkyl group or a substituted or unsubstituted C1-C8 hydroxyalkyl group; 【Transformation 6】 In formula (CII), R ３５ contains a substituted or unsubstituted C2-C6 methylene group, 【Transformation 7】 In formula (CIII), R ３６ , R ３７ and R ３８ each independently comprises a hydrogen atom or a substituted or unsubstituted C1-C8 alkyl group; R ３９ comprises a substituted or unsubstituted C1-C8 alkyl group; The battery cell according to any one of claims 1 to 7, wherein the degree of polymerization n of the ester-based polymer is selected from any positive integer from 800 to 20,000.

9. the swelling polymer comprises an aldehyde ketone polymer, the aldehyde ketone polymer comprising a compound represented by formula (DI) and / or a compound represented by formula (DII), 【Transformation 8】 In formula (DI), R ４１ contains a single bond, a substituted or unsubstituted C1-C6 methylene group, and R ４２ contains a hydrogen atom, a substituted or unsubstituted C1-C6 alkyl group, 【Chemistry 9】 In formula (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; r and s are each independently selected from integers of 0 to 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 8, wherein the degree of polymerization n of the aldehyde ketone polymer is selected from any positive integer of 500 to 15,000.

10. The battery cell according to any one of claims 1 to 9, wherein the first polar sheet includes a current collector and a film layer provided on at least one surface of the current collector, the film layer including the swelling polymer and active material particles.

11. the film layer includes a polymer layer containing a swelling polymer and an active material layer containing active material particles, the active material layer being disposed on at least one surface of the current collector, and the polymer layer being disposed on the surface of the active material layer opposite the current collector; and / or The battery cell according to claim 10 , wherein the active material particles are plural, and a gap is formed between two adjacent active material particles, and the swelling polymer is distributed in the gap.

12. the separator includes a substrate and a coating layer provided on at least one surface of the substrate; the swelling polymer is distributed in the void spaces of the substrate; and / or the swelling polymer is distributed within the coating layer; and / or The battery cell according to any one of claims 1 to 11, wherein the swelling polymer is provided on a surface of the coating layer opposite to the substrate.

13. The battery cell according to any one of claims 1 to 12, further comprising a liquid electrolyte, the liquid electrolyte being located within the electrode assembly.

14. The battery cell is (m / ρ) / V 総孔 Satisfies ≧80%, V 総孔 represents the void volume of the electrode assembly, in mL; m is the difference in mass of the battery cell before drying and after drying, expressed in g; 14. The battery cell according to claim 1, wherein ρ is a numerical value of the density of the liquid electrolyte, and the unit is g / mL.

15. The battery cell is 0≦y / Ah≦15%, y represents the volume of free electrolyte in the battery cell, expressed in mL; The battery cell according to any one of claims 1 to 14, wherein Ah indicates a numerical value of the nominal capacity of the battery cell, and the unit is Ah.

16. The battery cell is 0≦y / V 総孔 ≦15% is satisfied, y represents the volume of free electrolyte in the battery cell, expressed in mL; V 総孔 The battery cell according to any one of claims 1 to 15, wherein ∇ represents a numerical value of the void volume of the electrode assembly, and the unit is mL.

17. After the battery cell is subjected to a linear sweep vibration test, the battery cell is charged to 100% SOC, a hole is drilled in the battery cell, and the hole is positioned at the lowest position in the vertical direction. The volume of the liquid electrolyte flowing out of the battery cell is recorded as M1, and 0 mL≦M1≦0.5 mL is satisfied; where: The vibration direction of the linear sweep vibration test is a simple vertical harmonic motion, The vibration frequency of the linear sweep vibration test is 10 Hz to 55 Hz; The maximum acceleration of the linear sweep vibration test is 30 m / s ２ and The number of sweep cycles in the linear sweep vibration test was 10; The battery cell according to any one of claims 1 to 16, wherein the vibration time of the linear sweep vibration test is 3 hours.

18. 18. The battery cell of claim 17, wherein after the battery cell is subjected to a linear sweep vibration test, the battery cell 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 position in a vertical direction, and a volume of liquid electrolyte flowing out of the battery cell is recorded as M1, where M1 is 0 mL.

19. After the battery cell is subjected to a linear sweep vibration test, the electrode assembly is removed, and the electrode assembly is subjected to a compression test. The volume of the electrolyte flowing out of the electrode assembly is recorded as M2, and 0 mL≦M2≦0.5 mL is satisfied. where: The pressing direction of the pressing test is perpendicular to the thickness direction of the electrode assembly, The battery cell according to claim 17 , wherein the pressing force in the pressing test is 0.35 MPa.

20. 10. The battery cell of claim 9, wherein the electrode assembly is removed from the battery cell after the linear sweep vibration test, and the electrode assembly is subjected to a compression test, and a volume of electrolyte flowing out of the electrode assembly is recorded as M2, and M2 is 0 mL.

21. A battery comprising the battery cell according to any one of claims 1 to 20.

22. 22. A power consuming device comprising the battery of claim 21.

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