Battery cells, binders and their preparation methods, battery devices and electrical devices

Abstract

This application discloses a battery cell, a binder, a method for preparing the same, a battery device, and an electrical device. A battery cell includes a negative electrode sheet, the negative electrode sheet comprising a negative current collector and an active film layer disposed on at least one surface of the negative current collector. The active film layer comprises active particles and a film layer of binder coated on the surface of the active particles and having a three-dimensional cross-linked network structure. The binder comprises a first block copolymer and a second block copolymer; wherein the first block copolymer and / or the second block copolymer comprises repeating acrylic acid units. According to embodiments of this application, the cycle performance of the battery cell can be improved.

Description

Technical Field

[0001] This application relates to battery cells, and more particularly to a battery cell, a binder and its preparation method, a battery device and an electrical device. Background Technology

[0002] In lithium-ion battery cells, styrene-butadiene rubber (SBR) is often used as a binder for the graphite / silicon-based negative electrode. However, SBR has poor dispersion properties and can cause swelling after agglomeration. Therefore, it is usually used in conjunction with carboxymethyl cellulose (CMC), which has dispersing capabilities.

[0003] However, during the processing of negative electrode slurry, prolonged stirring and excessively high rotation speed can cause demulsification of the slurry, which reduces the adhesion and cohesion of the binder, leading to the demolding of the negative electrode active material and reducing the electrochemical performance of the battery cell. Summary of the Invention

[0004] This application provides a battery cell, a binder and its preparation method, a battery device and an electrical device, which can improve the cycle performance of the battery cell.

[0005] In a first aspect, embodiments of this application provide a battery cell, including a negative electrode sheet, the negative electrode sheet including a negative current collector and an active film layer disposed on at least one surface of the negative current collector, the active film layer including active particles and a film layer of binder coated on the surface of the active particles and having a three-dimensional cross-linked network structure; the binder includes a first block copolymer and a second block copolymer; wherein the first block copolymer and / or the second block copolymer includes acrylic repeating units; the first block copolymer further includes one or more of (3-acrylamidopropyl)trimethylammonium chloride repeating units, methacryloyloxyethyltrimethylammonium chloride repeating units and N-dimethyl-N-acrylamidopropylammonium chloride repeating units; the second block copolymer further includes one or more of 2-acrylamido-2-methyl-1-propanesulfonate sodium repeating units, dietherazole repeating units and vinylpyridine phosphate repeating units.

[0006] The first and second block copolymers in this application embodiment have positive and negative charge centers, respectively, and can achieve physical cross-linking under the action of Coulomb forces to form a three-dimensional network cross-linked structure. This structure can then coat the surface of the active material, achieving surface bonding. Compared to point bonding, surface bonding has stronger adhesive strength and can also absorb the stress generated by the volume expansion of active particles during charging and discharging, thereby reducing the volume expansion of active particles during charging and discharging. This improves the cycle performance of the battery cell.

[0007] In the embodiments of this application, the first block copolymer and the second block copolymer may simultaneously contain acrylic repeating units, or they may contain acrylic repeating units alone. Acrylic repeating units have abundant polar groups, which can form hydrogen bonds with the substrate, thereby improving the mechanical strength of the binder and thus improving the stability of the negative electrode sheet. This improves the cycle performance of the battery cell.

[0008] The three-dimensional cross-linked network structure of the binder in this embodiment can make the binder film layer more complete, thereby improving the cycle performance of the battery cell.

[0009] In some embodiments, the first block copolymer and / or the second block copolymer further include one or more of amide repeating units and ethylene glycol acrylate repeating units.

[0010] In some embodiments, the first block copolymer comprises amide repeating units, ethylene glycol acrylate repeating units, and (3-acrylamidopropyl)trimethylammonium chloride repeating units; the second block copolymer comprises amide repeating units, acrylic acid repeating units, and sodium 2-acrylamido-2-methyl-1-propanesulfonate repeating units.

[0011] In some embodiments, the repeating units in the adhesive satisfy at least one of conditions (1) to (5):

[0012] (1) The degree of polymerization of the repeating unit of acrylic acid is 9000 to 30000;

[0013] (2) The degree of polymerization of the repeating amide unit is 8000 to 13000;

[0014] (3) The degree of polymerization of the repeating unit of ethylene glycol acrylate is 9,000 to 40,000;

[0015] (4) The degree of polymerization of the repeating unit (3-acrylamidopropyl)trimethylammonium chloride is 10,000 to 13,000;

[0016] (5) The degree of polymerization of the repeating unit of sodium 2-acrylamide-2-methyl-1-propanesulfonate is 9000 to 14000.

[0017] In some embodiments, the amide repeating unit includes one or more of acrylamide repeating units, imide amide repeating units, and amide imide repeating units.

[0018] In some embodiments, based on the active film layer, the mass content of the adhesive is 1% to 8%.

[0019] Optionally, the adhesive content is 2% to 6% by mass.

[0020] Secondly, embodiments of this application provide an adhesive comprising a first block copolymer and a second block copolymer having a three-dimensional crosslinked network structure; wherein the first block copolymer and / or the second block copolymer comprises acrylic repeating units; the first block copolymer further comprises one or more of (3-acrylamidopropyl)trimethylammonium chloride repeating units, methacryloyloxyethyltrimethylammonium chloride repeating units, and N-dimethyl-N-acrylamidopropylammonium chloride repeating units; the second block copolymer further comprises one or more of 2-acrylamido-2-methyl-1-propanesulfonate repeating units, dietherazole repeating units, and vinylpyridine phosphate repeating units.

[0021] In some embodiments, the adhesive satisfies at least one of conditions (1) to (4):

[0022] (1) The adhesive strength of the adhesive is 10 N / m to 40 N / m;

[0023] (2) The cohesive strength of the adhesive is 300 N / m to 600 N / m;

[0024] (3) The tensile strength of the adhesive is 5 MPa to 70 MPa;

[0025] (4) The ion diffusion coefficient of the adhesive is 1*10 -11 cm 2 / s~1*10 -16 cm 2 / s.

[0026] Thirdly, embodiments of this application provide a method for preparing an adhesive, comprising: providing a first block copolymer, the first block copolymer comprising one or more of (3-acrylamidopropyl)trimethylammonium chloride repeating units, methacryloyloxyethyltrimethylammonium chloride repeating units, and N-dimethyl-N-acrylamidopropylammonium chloride repeating units; providing a second block copolymer, the second block copolymer comprising one or more of 2-acrylamido-2-methyl-1-propanesulfonate sodium repeating units, dietherazole repeating units, and vinylpyridine phosphate repeating units; and mixing the first block copolymer and the second block copolymer to obtain an adhesive, the adhesive comprising acrylic repeating units.

[0027] In some embodiments, the preparation method of the first block copolymer includes: mixing acrylamide, poly(ethylene glycol acrylate), (3-acrylamidopropyl)trimethylammonium chloride and a solvent to obtain a raw material solution; mixing the raw material solution and an initiator, and reacting at 60-80°C for 10-14 h to obtain the first block copolymer.

[0028] In some embodiments, the preparation method of the second block copolymer includes: mixing acrylamide, acrylic acid, sodium 2-acrylamido-2-methyl-1-propanesulfonate and a solvent to obtain a raw material solution; mixing the raw material solution and an initiator, and reacting at 60-80°C for 10-14 h to obtain the second block copolymer.

[0029] In some embodiments, the initiator includes one or more of 2,2-azobis(2-methylpropylimidazolium) hydrochloride, ammonium persulfate, and potassium persulfate.

[0030] Fourthly, embodiments of this application provide a battery device including a plurality of battery cells as described in the first aspect.

[0031] Fifthly, embodiments of this application provide an electrical device, including a battery cell as described in the first aspect or a battery device as described in the fourth aspect. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 The diagram shows a schematic of a battery cell provided in some embodiments of this application.

[0034] Figure 2 A schematic diagram of an electrical device provided in some embodiments of this application is shown.

[0035] Figure 3 The fast charging performance diagrams of Embodiment 1 and Comparative Example 1 of this application are shown.

[0036] Figure 4 The cyclic performance diagrams of Embodiment 1 and Comparative Example 1 of this application are shown, wherein both Embodiment 1 and Comparative Example 1 are provided with three parallel groups.

[0037] Figure 5 The images show actual photographs of the surface of the negative electrode sheet after fast charging cycles of Embodiment 1 and Comparative Example 1 of this application.

[0038] The accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0039] To better understand the above-mentioned objectives, features, and advantages of this application, the solution of this application will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0040] Many specific details are set forth in the following description in order to provide a full understanding of this application, but this application may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of this application, and not all embodiments.

[0041] The embodiments of this application for improving the cycle performance and fast-charging performance of battery cells are described in detail below with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0042] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0043] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0044] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0045] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0046] Unless otherwise specified, in this application, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0047] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0048] In the description of the embodiments of this application, unless otherwise specified, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0049] Unless otherwise stated, the test temperature for all parameters mentioned in this application is 25°C.

[0050] The battery cells mentioned in the embodiments of this application are capable of charging and discharging independently. The battery cells may be cylindrical, cuboid, or other shapes, and the embodiments of this application are not limited in this respect. Figure 1 This is a cuboid-shaped battery cell used as an example.

[0051] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0052] The battery cell provided in the embodiments of this application includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator disposed between the negative electrode and the positive electrode. During the charging and discharging process of the battery cell, active ions (e.g., lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, disposed between the positive and negative electrodes, serves to prevent short circuits between the positive and negative electrodes while allowing active ions to pass through. The electrode assembly can be a wound structure or a stacked structure; the embodiments of this application are not limited in this regard.

[0053] The battery cell also includes an outer packaging, which encapsulates the electrode components and electrolyte. The outer packaging can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. It can also be a flexible package, such as a pouch. The material of the flexible package can be plastic, such as one or more of aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0054] The battery cells provided in the embodiments of this application can be lithium-ion battery cells, sodium-ion battery cells, sodium-lithium-ion battery cells, lithium metal battery cells, sodium metal battery cells, lithium-sulfur battery cells, magnesium-ion battery cells, nickel-metal hydride battery cells, nickel-cadmium battery cells, lead-acid battery cells, etc., and the embodiments of this application are not limited to these.

[0055] The method for preparing the battery cell of this application is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a battery cell is obtained.

[0056] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0057] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0058] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0059] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0060] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0061] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0062] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0063] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0064] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0065] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use battery cells or battery devices, such as, but not limited to, mobile devices (e.g., mobile phones, tablets, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc. Battery cells and battery devices are used to store or provide electrical energy.

[0066] Figure 2 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0067] In view of the problems in the background art, the embodiments of this application provide a battery cell, a binder and a method for preparing the same, a battery device and an electrical device, which can improve the cycle performance of the battery cell.

[0068] battery cell

[0069] A battery cell includes a negative electrode sheet, the negative electrode sheet including a negative current collector and an active film layer disposed on at least one surface of the negative current collector, the active film layer including active particles and a film layer of binder coated on the surface of the active particles and having a three-dimensional cross-linked network structure; the binder includes a first block copolymer and a second block copolymer; wherein the first block copolymer and / or the second block copolymer includes acrylic repeating units; the first block copolymer further includes one or more of (3-acrylamidopropyl)trimethylammonium chloride repeating units, methacryloyloxyethyltrimethylammonium chloride repeating units, and N-dimethyl-N-acrylamidopropylammonium chloride repeating units; the second block copolymer further includes one or more of 2-acrylamido-2-methyl-1-propanesulfonate repeating units, dietherazole repeating units, and vinylpyridine phosphate repeating units.

[0070] The first and second block copolymers in this application embodiment have positive and negative charge centers, respectively, and can achieve physical cross-linking under the action of Coulomb forces to form a three-dimensional network cross-linked structure. This structure can then coat the surface of the active material, achieving surface bonding. Compared to point bonding, surface bonding has stronger adhesive strength and can also absorb the stress generated by the volume expansion of active particles during charging and discharging, thereby reducing the volume expansion of active particles during charging and discharging. This improves the cycle performance of the battery cell.

[0071] In the embodiments of this application, the first block copolymer and the second block copolymer may simultaneously contain repeating acrylic acid units, or they may each contain repeating acrylic acid units individually. For example, only the first block copolymer contains repeating acrylic acid units, while the second block copolymer does not; the first block copolymer does not contain repeating acrylic acid units, while only the second block copolymer contains repeating acrylic acid units; or both the first and second block copolymers contain repeating acrylic acid units. The repeating acrylic acid units have abundant polar groups, which can form hydrogen bonds with the substrate, thereby improving the mechanical strength of the binder and thus enhancing the stability of the negative electrode sheet. This improves the cycle performance and fast-charging performance of the battery cell.

[0072] The three-dimensional cross-linked network structure of the binder in this embodiment makes the binder film layer more complete. This can improve the cycle performance of the battery cell.

[0073] In this application, the structural units and content of the binder can be determined using methods known in the art, such as nuclear magnetic resonance spectroscopy.

[0074] Nuclear magnetic resonance spectroscopy (NMR) is used to study the absorption of radio frequency radiation by atomic nuclei in a strong magnetic field. It is one of the most powerful tools for qualitative analysis of the composition and structure of various organic and inorganic substances, and sometimes quantitative analysis as well. It can also be combined with infrared spectroscopy, such as Fourier transform infrared spectroscopy (FTIR), which examines the interaction between infrared radiation and the vibrations or rotations of molecules, allowing for structural analysis by recording the infrared absorption spectra of the sample.

[0075] The following test steps can be used to detect organic functional groups using infrared spectroscopy: An infrared beam passes through a depth of a few μm on the surface of an electrode (ATR is a Ge crystal). When irradiated with infrared light of continuously varying frequencies, molecules on the electrode surface absorb radiation at certain frequencies. This absorption causes a net change in the dipole moment due to their vibrational or rotational motion, resulting in transitions from the ground state to excited states in molecular vibrational and rotational energy levels. This weakens the intensity of transmitted light corresponding to these absorption regions. Recording the percentage transmittance versus wavenumber curve yields the infrared spectrum. The infrared spectrum and functional group analysis results are then obtained. For example, the national standard GB / T6040-2002, "General Rules for Infrared Spectroscopic Analysis," can be referenced. Alternatively, ICP testing can be used, for example, referring to standards YS / T1006.2-2014, GB / T23367.2-2009, or YS / T1028.5-2015.

[0076] Alternatively, an ICP inductively coupled plasma atomic emission spectrometer (model iCAP 740) can be used, and measurements can be performed according to the manufacturer's instructions. Further analysis can be performed by combining pyrolysis gravimetric analysis and gas chromatography-mass spectrometry.

[0077] In some embodiments, the first block copolymer and / or the second block copolymer further include one or more of amide repeating units and ethylene glycol acrylate repeating units.

[0078] In the embodiments of this application, the first block copolymer may further include one or more of amide repeating units and ethylene glycol acrylate repeating units, and the second block copolymer may also include one or more of amide repeating units and ethylene glycol acrylate repeating units. Furthermore, the total number of repeating units in both the first and second block copolymers must include acrylic repeating units, amide repeating units, and ethylene glycol acrylate repeating units. For example, if the first block copolymer includes only acrylic repeating units, the second block copolymer must include both amide repeating units and ethylene glycol acrylate repeating units; if the first block copolymer includes only amide repeating units, the second block copolymer must include both acrylic repeating units and ethylene glycol acrylate repeating units; if the first block copolymer includes only acrylic repeating units and amide repeating units, the second block copolymer must at least include ethylene glycol acrylate repeating units.

[0079] In this embodiment, the amide repeating unit can construct a strong hydrogen bond network to improve the self-healing ability of the binder and reduce the possibility of damage to the negative electrode sheet caused by the volume expansion of active particles during charging and discharging, thereby improving the stability of the negative electrode sheet. The ethylene glycol acrylate repeating unit is an ion-conducting segment that can construct an ion-conducting network, thereby improving the lithium-ion transport capability in the negative electrode film. This improves the cycle performance and fast-charging performance of the battery cell.

[0080] The three-dimensional cross-linked network structure of the binder in this application embodiment makes the strong hydrogen bond network constructed by the amide repeating units and the ion-conducting network constructed by the ethylene glycol acrylate repeating units more complete. The complete strong hydrogen bond network can guide the rearrangement of molecular chains to reform broken hydrogen bonds when cracks or damage occur in the binder, thereby achieving self-repair. Furthermore, the complete strong hydrogen bond network has excellent energy dissipation capabilities, absorbing and dissipating energy before cracks or damage occur in the binder to reduce crack propagation, thus enhancing the binder's toughness and damage resistance. The complete ion-conducting network can enhance the ion transport capability in the negative electrode film layer, thereby improving the fast-charging performance of the battery cell; simultaneously, it can reduce the possibility of concentration polarization, thus significantly improving low-temperature charging kinetics. This can better improve the cycle performance and fast-charging performance of the battery cell.

[0081] In some embodiments, in order to better improve the cycle performance and fast charging performance of the battery cell, the first block copolymer includes amide repeating units, ethylene glycol acrylate repeating units, and (3-acrylamidopropyl)trimethylammonium chloride repeating units; the second block copolymer includes amide repeating units, acrylic acid repeating units, and sodium 2-acrylamido-2-methyl-1-propanesulfonate repeating units.

[0082] In some embodiments, the degree of polymerization of the acrylic repeating unit is 9000 to 30000.

[0083] In some embodiments, the degree of polymerization of the amide repeating unit is 8000 to 13000.

[0084] In some embodiments, the degree of polymerization of the ethylene glycol acrylate repeating unit is 9000 to 40000.

[0085] In some embodiments, the degree of polymerization of the (3-acrylamidopropyl)trimethylammonium chloride repeating unit is 10,000 to 30,000.

[0086] In some embodiments, the degree of polymerization of the repeating unit of sodium 2-acrylamide-2-methyl-1-propanesulfonate is 9000 to 14000.

[0087] The embodiments of this application have repeating units with a suitable content range, which can take into account the self-healing ability, ion conduction ability and mechanical strength of the binder, so that the battery cell has stable cycle performance and good fast charging performance.

[0088] Optionally, the degree of polymerization of the acrylic repeating unit is independently selected from any value among 9000, 10000, 15000, 20000, 25000, 30000 or any range between both.

[0089] Optionally, the degree of polymerization of the amide repeating unit is independently selected from any value among 8000, 8500, 9000, 9500, 10000, 11000, 12000, and 13000, or a range between any two.

[0090] Optionally, the degree of polymerization of the ethylene glycol acrylate repeating unit is independently selected from any value among 9000, 9500, 10000, 15000, 20000, 25000, 30000, 35000, 40000 or a range between any two.

[0091] Optionally, the degree of polymerization of the (3-acrylamidopropyl)trimethylammonium chloride repeating unit is independently selected from any value among 10000, 10400, 10800, 11200, 11600, 11800, 12200, 126000, 13000 or any range between the two.

[0092] Optionally, the degree of polymerization of the repeating unit of sodium 2-acrylamide-2-methyl-1-propanesulfonate is independently selected from any value among 9000, 10500, 11000, 11500, 12000, 12500, 13000, 13500, and 14000, or a range between any two.

[0093] In some embodiments, based on the active film layer, the mass content of the adhesive is 1% to 8%.

[0094] The embodiments of this application contain an appropriate amount of binder, which can form a film layer with uniform thickness on the surface of the active particles to fix the active particles by surface bonding. The film layer with uniform thickness can more evenly absorb the stress generated by the volume expansion of the active particles during charging and discharging, thereby improving the mechanical strength of the binder and reducing the possibility of damage to the active film layer.

[0095] In some embodiments, in order to make the thickness of the film layer formed by the adhesive more uniform, the mass content of the adhesive is 2% to 6%.

[0096] Optionally, based on the active film layer, the mass content of the adhesive is independently selected from 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, and 4. Any value from 4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6.0%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7.0%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9%, 8%, or a range between any two.

[0097] In this application, the mass content of the adhesive can be determined using methods known in the art, such as thermogravimetric analysis.

[0098] In some embodiments, the negative electrode active particles may be materials known in the art for use in battery cells. As examples, the negative electrode active particles may include, but are not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include, but are not limited to, one or more of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include, but are not limited to, one or more of elemental tin, tin oxide, and tin alloys.

[0099] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. As an example, the negative electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0100] In some embodiments, the negative electrode film layer may also include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0101] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include, but is not limited to, one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0102] The negative electrode film is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, negative electrode conductive agent, negative electrode binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0103] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet also includes a conductive undercoat layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector.

[0104] In some embodiments, the negative electrode sheet can be made of foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, foamed carbon, etc. When foamed metal is used as the negative electrode sheet, the surface of the foamed metal may or may not contain a negative electrode active material.

[0105] [Positive electrode plate]

[0106] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and comprising a positive electrode active material. For example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0107] In some embodiments, the positive electrode active material includes a material capable of extracting and inserting lithium.

[0108] As examples, positive electrode active materials may include, but are not limited to, one or more of lithium transition metal oxides, metal chalcogenides, lithium-containing phosphates, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, lithium titanium oxides, and their respective modified compounds. Lithium transition metal oxides may include, but are not limited to, layered structures and spinel structures. Examples of lithium-containing phosphates may include, but are not limited to, lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, lithium iron manganese phosphate and carbon composites, and their respective modified compounds.

[0109] In some embodiments, to further improve the energy density of a single battery cell, the positive electrode active material may include materials of the general formula Li. a Ni b Co c M d O e D f One or more of lithium transition metal oxides and their modified compounds. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M may include, but is not limited to, one or more of Ge, Mo, Sn, Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and D may include, but is not limited to, one or more of N, F, S and Cl.

[0110] In some embodiments, the positive electrode active material may simultaneously comprise lithium transition metal oxide and lithium phosphate. This is advantageous for obtaining battery cells that balance high capacity and high reliability.

[0111] As an example, the positive electrode active material may include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, and LiNi 1 / 2 Mn 1 / 2O2, LiMn2O4, Li 4 / 3 Ti 5 / 3 O4, LiNi 1 / 2 Mn 1 / 2 O2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.80 Co 0.15 Al 0.05 O2, LiFePO4, LiMnPO4, Li 1.13 Ti 0.57 Fe 0.3 One or more of S2.

[0112] In some embodiments, the positive electrode active material includes a material capable of extracting and inserting sodium. For example, the positive electrode active material may include, but is not limited to, one or more of layered transition metal oxides (including but not limited to P2 type, O3 type, etc.), polyanionic materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian materials.

[0113] In some embodiments, as an example, the positive electrode active material may include, but is not limited to, NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, Na 0.67 MO2 (M includes at least two of Fe, Co, Cr, Mn, Ni, V, Ti, and Mo), NaMO2 (M includes at least two of Fe, Co, Ni, V, Ti, and Mo), NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, Prussian blue, Prussian white, and one or more of their respective modified compounds.

[0114] The modified compounds for the above-mentioned positive electrode active materials can be obtained by doping and / or surface coating of the positive electrode active materials.

[0115] In some embodiments, the positive electrode film may optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0116] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene oxide, fluorinated acrylate resins, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0117] In some embodiments, the positive current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. As an example, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0118] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing positive electrode active materials, positive electrode conductive agents, positive electrode binders, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this.

[0119] [Electrolytes]

[0120] This application does not impose specific limitations on the type of electrolyte, which can be selected according to requirements. For example, the electrolyte can be selected from at least one of solid electrolytes and liquid electrolytes (i.e., electrolyte solutions).

[0121] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0122] Taking a lithium battery cell as an example, the electrolyte salt may include, but is not limited to, one or more of the following: lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0123] Taking sodium battery cells as an example, the electrolyte salt may include, but is not limited to, one or more of the following: sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium difluorosulfonyl imide (NaFSI), sodium difluoromethanesulfonyl imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalate borate (NaDFOB), sodium dioxalate borate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluorodioxalate phosphate (NaDFOP), and sodium tetrafluorooxalate phosphate (NaTFOP).

[0124] The type of solvent is not specifically limited and can be selected according to actual needs. In some embodiments, as an example, the solvent may include at least one 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), butyl 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), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0125] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of the battery cell, such as additives that improve the overcharge performance of the battery cell, additives that improve the high-temperature performance of the battery cell, and additives that improve the low-temperature power performance of the battery cell.

[0126] [Isolation membrane]

[0127] Battery cells using electrolytes, as well as some battery cells using solid electrolytes, also include a separator. The separator is disposed between the positive and negative electrodes, primarily serving to prevent short circuits between the positive and negative electrodes, while allowing metal ions to pass through. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0128] In some embodiments, the isolation membrane includes a porous base membrane and a coating located on at least one side of the porous base membrane.

[0129] In some embodiments, the material of the separator may include at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0130] In some embodiments, the coating includes an adhesive, which may include, but is not limited to, one or more of polyacrylate adhesives, nitrile rubber adhesives, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0131] In some embodiments, the coating may further include a dispersant, such as one or more of alkylphenol polyoxyethylene ethers, polyacrylic acid dispersants, and cellulose dispersants, including but not limited to. For example, the dispersant may include one or more of sodium carboxymethyl cellulose, sodium polyacrylate, and ammonium polyacrylate.

[0132] adhesive

[0133] An adhesive comprising a first block copolymer and a second block copolymer having a three-dimensional crosslinked network structure; wherein the first block copolymer and / or the second block copolymer comprises repeating acrylic acid units; the first block copolymer further comprises one or more repeating units of (3-acrylamidopropyl)trimethylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, and N-dimethyl-N-acrylamidopropylammonium chloride; and the second block copolymer further comprises one or more repeating units of sodium 2-acrylamido-2-methyl-1-propanesulfonate, dietherazole, and vinylpyridine phosphate.

[0134] The first and second block copolymers in this application embodiment have positive and negative charge centers, respectively, and can achieve physical cross-linking under the action of Coulomb forces to form a three-dimensional network cross-linked structure. This structure can then coat the surface of the active material, achieving surface bonding. Compared to point bonding, surface bonding has stronger adhesive strength and can also absorb the stress generated by the volume expansion of active particles during charging and discharging, thereby reducing the volume expansion of active particles during charging and discharging. This improves the cycle performance of the battery cell.

[0135] In the embodiments of this application, the first block copolymer and the second block copolymer may simultaneously contain acrylic repeating units, or they may contain acrylic repeating units alone. The acrylic repeating units have abundant polar groups, which can form hydrogen bonds with the substrate, thereby improving the mechanical strength of the binder and thus enhancing the stability of the negative electrode sheet. This improves the cycle performance and fast-charging performance of the battery cell.

[0136] The three-dimensional cross-linked network structure of the binder in this embodiment can make the binder film layer more complete, thereby improving the cycle performance of the battery cell.

[0137] In some embodiments, the adhesive force is 10 N / m to 40 N / m.

[0138] In some embodiments, the cohesive strength of the adhesive is 300 N / m to 600 N / m.

[0139] In some embodiments, the tensile strength of the adhesive is 5 MPa to 70 MPa.

[0140] In some embodiments, the ion diffusion coefficient of the adhesive is 1*10⁻⁶. -11 cm 2 / s~1*10 -16 cm 2 / s.

[0141] Tensile strength is a term known in the art and can be determined using instruments and methods known in the art. For example, a paste containing binder can be coated onto release paper, dried thoroughly in an oven at 110°C, with the binder film thickness controlled to be 60 μm after drying. Then, a strip sample of 10 cm × 2.5 cm can be cut, and the tensile strength and elongation at break can be tested according to the instruments and methods specified in GB / T 1040.1-2018 "Tension Methods for Plastics".

[0142] The ion diffusion coefficient of an adhesive refers to the speed at which ions move within or on the surface of the adhesive.

[0143] Optionally, the adhesive strength is independently selected from any value or a range between any two of 10N, 11N, 12N, 13N, 14N, 15N, 16N, 17N, 18N, 19N, 20N, 21N, 22N, 23N, 24N, 25N, 26N, 27N, 28N, 29N, 30N, 31N, 32N, 33N, 34N, 35N, 36N, 37N, 38N, 39N, and 40N.

[0144] Optionally, the cohesive force of the adhesive is independently selected from any value or a range between any two of 300 N / m, 310 N / m, 320 N / m, 330 N / m, 340 N / m, 350 N / m, 360 N / m, 370 N / m, 380 N / m, 390 N / m, 400 N / m, 410 N / m, 420 N / m, 430 N / m, 440 N / m, 450 N / m, 460 N / m, 470 N / m, 480 N / m, 490 N / m, 500 N / m, 510 N / m, 520 N / m, 530 N / m, 540 N / m, 550 N / m, 560 N / m, 570 N / m, 580 N / m, 590 N / m, and 600 N / m.

[0145] Optionally, the tensile strength of the adhesive is independently selected from 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, 11 MPa, 12 MPa, 13 MPa, 14 MPa, 15 MPa, 16 MPa, 17 MPa, 18 MPa, 19 MPa, 20 MPa, 21 MPa, 22 MPa, 23 MPa, 24 MPa, 25 MPa, 26 MPa, 27 MPa, 28 MPa, 29 MPa, 30 MPa, 31 MPa, 32 MPa, 33 MPa, 34 MPa, 35 MPa, 36 MPa, 37 MPa, 38 MPa, etc. The values ​​are any one of the following: 39MPa, 40MPa, 41MPa, 42MPa, 43MPa, 44MPa, 45MPa, 46MPa, 47MPa, 48MPa, 49MPa, 50MPa, 51MPa, 52MPa, 53MPa, 54MPa, 55MPa, 56MPa, 57MPa, 58MPa, 59MPa, 60MPa, 61MPa, 62MPa, 63MPa, 64MPa, 65MPa, 66MPa, 67MPa, 68MPa, 69MPa, and 70MPa, or any value within a range of two.

[0146] Optionally, the ion diffusion coefficient of the adhesive is independently selected from 1*10. -16 cm 2 / s、1*10 -15 cm 2 / s、1*10- 14 cm 2 / s、1*10 -13 cm 2 / s、1*10 -12 cm 2 / s、1*10 -11 cm 2 Any value in / s or any range between the two.

[0147] Preparation method

[0148] This application provides a method for preparing an adhesive, comprising: providing a first block copolymer, the first block copolymer comprising one or more of (3-acrylamidopropyl)trimethylammonium chloride repeating units, methacryloyloxyethyltrimethylammonium chloride repeating units, and N-dimethyl-N-acrylamidopropylammonium chloride repeating units; providing a second block copolymer, the second block copolymer comprising one or more of 2-acrylamido-2-methyl-1-propanesulfonate repeating units, dietherazole repeating units, and vinylpyridine phosphate repeating units; and mixing the first block copolymer and the second block copolymer to obtain an adhesive, the adhesive comprising acrylic repeating units.

[0149] In this embodiment, a first block copolymer with a positively charged center and a second block copolymer with a negatively charged center are mixed. The first and second block copolymers undergo physical cross-linking under the Coulomb forces of the positive and negative charges to form an adhesive with a three-dimensional cross-linked network structure. The number of acrylic repeating units in the first and / or second block copolymers can be adjusted as needed to ensure that the adhesive has an appropriate content of acrylic repeating units.

[0150] In other embodiments, the number of amide repeating units and / or ethylene glycol acrylate repeating units in the first block copolymer and / or the second block copolymer can be adjusted as needed to make the adhesive have predetermined repeating units.

[0151] In some embodiments, the preparation method of the first block copolymer includes: mixing acrylamide, poly(ethylene glycol acrylate), (3-acrylamidopropyl)trimethylammonium chloride and a solvent to obtain a raw material solution; mixing the raw material solution and an initiator, and reacting at 60-80°C for 10-14 h to obtain the first block copolymer.

[0152] In some embodiments, the preparation method of the second block copolymer includes: mixing acrylamide, acrylic acid, sodium 2-acrylamido-2-methyl-1-propanesulfonate and a solvent to obtain a raw material solution; mixing the raw material solution and an initiator, and reacting at 60-80°C for 10-14 h to obtain the second block copolymer.

[0153] In some embodiments, the initiator includes one or more of 2,2-azobis(2-methylpropylimidazolium) hydrochloride, ammonium persulfate, and potassium persulfate.

[0154] Example

[0155] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0156] 1. Preparation of adhesive

[0157] 1.1 Synthesis of the first block copolymer: Deionized water and one or more of amide, poly(ethylene glycol acrylate) and (3-acrylamidopropyl)trimethylammonium chloride were added to the reactor at room temperature (25°C) in a predetermined ratio; the mixture was then stirred and mixed evenly to obtain a raw material solution; the raw material solution was then placed in a heating jacket, and an initiator was added after the temperature stabilized to react and obtain the first block copolymer.

[0158] 1.2 Synthesis of the second block copolymer: Deionized water and one or more of acrylamide, acrylic acid and sodium 2-acrylamide-2-methyl-1-propanesulfonate were added to the reactor at room temperature (25℃); the mixture was stirred and mixed evenly to obtain a raw material solution; the raw material solution was then placed in a heating jacket, and an initiator was added after the temperature stabilized to react and obtain the second block copolymer.

[0159] 1.3 The first block copolymer and the second block copolymer described above are mixed in a preset ratio to obtain an adhesive.

[0160] 2. Positive electrode plate

[0161] NCM ternary material, conductive agent (conductive carbon black), and binder (PVDF) were mixed at a mass ratio of 98:1:1, and then N-methylpyrrolidone was added. The mixture was stirred for 6 hours to obtain a positive electrode slurry with a solid content of 50 wt%. The positive electrode slurry was then coated onto a positive electrode current collector aluminum foil (13 μm thick), and after drying and cold pressing, a positive electrode sheet with a positive electrode active layer of 35 μm thickness was obtained.

[0162] 3. Negative electrode plate

[0163] The negative electrode active material (artificial graphite and silicon carbide material with a volume average particle size Dv50 of 12 μm), conductive agent SuperP, the above-mentioned binder, and dispersant sodium carboxymethyl cellulose (CMC-Na) were mixed and dispersed in deionized water at a mass ratio of 97:1:1:1, and stirred evenly to obtain a negative electrode active slurry; the negative electrode slurry was then prepared at 7 mg / cm³. 2 The coating density is uniformly coated on the copper foil of the negative electrode current collector, and after drying, the negative electrode sheet is obtained.

[0164] 4. Separating membrane

[0165] A porous separator membrane was obtained by using a polyethylene (PE) film (7μm thick) as the separator membrane.

[0166] 5. Electrolyte

[0167] The electrolyte salt LiPF6 was mixed with a mixed solvent and the additive VC (ethylene carbonate) to obtain the electrolyte solution. The concentration of the electrolyte salt in the mixed solvent was 1 mol / L. The mixed solvent consisted of EC (ethylene carbonate), DMC (dimethyl carbonate), and EMC (ethyl methyl carbonate) in a mass ratio of 33:33:34. The additive VC accounted for 2 wt% of the electrolyte solution.

[0168] 6. Assembly

[0169] The above-mentioned positive electrode sheet, separator and negative electrode sheet are wound and wrapped in an aluminum-plastic film bag, then injected with the prepared electrolyte, vacuum sealed and left to stand at room temperature for 6 hours to obtain a battery cell.

[0170] Table 1. Adhesive Synthesis Formulation

[0171]

[0172]

[0173] Table 2 Adhesive Properties

[0174] Adhesion strength N / m Tensile strength (MPa) <![CDATA[Ionic diffusion coefficient cm 2 / s]]> Cohesion N / m Example 1 38 60 <![CDATA[10 -11 ]]> 500 Example 2 35 50 <![CDATA[10 -11 ]]> 400 Example 3 36 59 <![CDATA[10 -11 ]]> 480 Example 4 38 60 <![CDATA[10 -14 ]]> 495 Example 5 10 30 <![CDATA[10 -11 ]]> 300 Example 6 36 55 <![CDATA[10 -11 ]]> 430 Comparative Example 1 20 45 <![CDATA[10 -17 ]]> 290 Comparative Example 2 5 20 <![CDATA[10 -11 ]]> 295

[0175] Data Analysis

[0176] 1. Capacity test

[0177] At 25°C, the battery cell was charged at a constant current of 0.33C to the charging cutoff voltage of 4.25V, then charged at a constant voltage to a current of 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.33C to the discharge cutoff voltage of 2.5V. Its actual capacity was recorded as C0.

[0178] 2. Fast charging performance test

[0179] At 35℃, the battery cells were sequentially charged at a constant current of 0.5C0, 1C0, 1.5C0, 2C0, 2.5C0, 3C0, 3.5C0, 4C0, 4.5C0, and 5C0 until the full battery charging cutoff voltage of 4.25V or the negative terminal cutoff potential of 0V (whichever comes first). After each charging, the cells were discharged at 1C0 until the full battery discharge cutoff voltage of 2.5V. The charging rates were recorded at 10%, 20%, 30% SOC...80% SOC. By plotting the SOC-negative electrode potential curves at different charging rates, and performing linear fitting, the charging rate corresponding to a negative electrode potential of 0V at different SOC states is obtained. This charging rate is the charging window for that SOC state, denoted as C10%SOC, C20%SOC, C30%SOC, C40%SOC, C50%SOC, C60%SOC, C70%SOC, and C80%SOC. Using the formula: (60 / C20%SOC + 60 / C30%SOC + 60 / C40%SOC + 60 / C50%SOC + 60 / C60%SOC + 60 / C70%SOC + 60 / C80%SOC) × 10%, the charging time T for the battery to charge from 10% SOC to 80% SOC is calculated. A shorter charging time T indicates better fast-charging performance of the secondary battery.

[0180] The charging curves obtained by plotting the charging rate corresponding to different SOC states during the above test process on the ordinate and SOC on the abscissa are as follows: Figure 3 As shown, Figure 3 The vertical axis represents the charge rate (Rate, C), and the horizontal axis represents the state of charge (SOC).

[0181] 3. Cyclic performance test

[0182] At 25°C, the prepared battery cells were charged to 4.25V at 0.33C0, left to stand for 5 minutes, and then discharged to 2.5V at 0.33C0. The discharge capacity C1 was recorded at this time, and C1 / C0 is the capacity retention rate. This process was repeated, and the capacity values ​​C1, C2, C3, etc., were recorded for each cycle. The capacity retention rate for each cycle was calculated until the capacity retention rate was less than or equal to 80%. The number of cycles at this time was recorded (one charge-discharge cycle is one cycle).

[0183] The battery cells that were cycled through charge and discharge until their capacity was less than 80% of the initial capacity were fully charged, and then disassembled to observe the lithium deposition on the negative electrode.

[0184] The test results are shown in Table 3 and Figure 1-3 .

[0185] Table 3 Electrical properties

[0186] Charging time at 35℃ Number of cycles Example 1 18min 3000 Example 2 17.5min 2500 Example 3 17.9min 2800 Example 4 20min 3003 Example 5 18.1min 2300 Example 6 17.9min 2600 Comparative Example 1 22min 2100 Comparative Example 2 18.1min 1500

[0187] Depend on Figure 3 It can be seen that, compared with the use of styrene-butadiene rubber (SBR) as the negative electrode binder in Comparative Example 1, the charging capability of Example 1 of this application is improved by 18% at 35°C.

[0188] Depend on Figure 4 It can be seen that, compared with the use of styrene-butadiene rubber (SBR) as the negative electrode binder in Comparative Example 1, the capacity retention rate of Example 1 of this application is improved by 10% under pure fast charge cycle at 25°C and high charge and discharge rate.

[0189] Depend on Figure 5 As can be seen, compared with the use of styrene-butadiene rubber (SBR) as the negative electrode binder in Comparative Example 1, after 10 cycles of pure fast charging, the disassembly of Example 1 of this application showed that almost no lithium dendrites were generated on the surface of the negative electrode sheet, while the surface of the negative electrode sheet using SBR binder was covered with lithium dendrites.

[0190] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A battery cell, comprising a negative electrode sheet, characterized in that, The negative electrode sheet includes a negative current collector and an active film layer disposed on at least one surface of the negative current collector. The active film layer includes active particles and a film layer of binder coated on the surface of the active particles and having a three-dimensional cross-linked network structure. The adhesive comprises a first block copolymer and a second block copolymer; Wherein, the first block copolymer and / or the second block copolymer comprises repeating acrylic acid units; The first block copolymer further includes one or more of (3-acrylamidopropyl)trimethylammonium chloride repeating units, methacryloyloxyethyltrimethylammonium chloride repeating units, and N-dimethyl-N-acrylamidopropylammonium chloride repeating units; the second block copolymer further includes one or more of 2-acrylamido-2-methyl-1-propanesulfonate repeating units, dietherazole repeating units, and vinylpyridine phosphate repeating units.

2. The battery cell according to claim 1, characterized in that, The first block copolymer and / or the second block copolymer further include one or more of amide repeating units and ethylene glycol acrylate repeating units.

3. The battery cell according to claim 2, characterized in that, The first block copolymer comprises amide repeating units, ethylene glycol acrylate repeating units, and (3-acrylamidopropyl)trimethylammonium chloride repeating units; the second block copolymer comprises amide repeating units, acrylic acid repeating units, and sodium 2-acrylamido-2-methyl-1-propanesulfonate repeating units.

4. The battery cell according to claim 2 or 3, characterized in that, The repeating units in the adhesive satisfy at least one of conditions (1) to (5): (1) The degree of polymerization of the acrylic repeating unit is 9000 to 30000; (2) The degree of polymerization of the amide repeating unit is 8000 to 13000; (3) The degree of polymerization of the ethylene glycol acrylate repeating unit is 9000 to 40000; (4) The degree of polymerization of the (3-acrylamidopropyl)trimethylammonium chloride repeating unit is 10,000 to 13,000; (5) The degree of polymerization of the repeating unit of sodium 2-acrylamide-2-methyl-1-propanesulfonate is 9000 to 14000.

5. The battery cell according to any one of claims 2-4, characterized in that, The amide repeating unit includes one or more of acrylamide repeating units, imide amide repeating units, and amide imide repeating units.

6. The battery cell according to any one of claims 1-5, characterized in that, Based on the active film layer, the mass content of the adhesive is 1% to 8%; Optionally, the adhesive has a mass content of 2% to 6%.

7. An adhesive, characterized in that, The adhesive comprises a first block copolymer and a second block copolymer and has a three-dimensional cross-linked network structure; Wherein, the first block copolymer and / or the second block copolymer comprises repeating acrylic acid units; The first block copolymer further includes one or more of (3-acrylamidopropyl)trimethylammonium chloride repeating units, methacryloyloxyethyltrimethylammonium chloride repeating units, and N-dimethyl-N-acrylamidopropylammonium chloride repeating units; the second block copolymer further includes one or more of 2-acrylamido-2-methyl-1-propanesulfonate repeating units, dietherazole repeating units, and vinylpyridine phosphate repeating units.

8. The adhesive according to claim 7, characterized in that, The adhesive satisfies at least one of conditions (1) to (4): (1) The adhesive force of the adhesive is 10 N / m to 40 N / m; (2) The cohesive strength of the adhesive is 300 N / m to 600 N / m; (3) The tensile strength of the adhesive is 5 MPa to 70 MPa; (4) The ion diffusion coefficient of the adhesive is 1*10 -11 cm 2 / s~1*10 -16 cm 2 / s.

9. A method for preparing an adhesive, characterized in that, include: A first block copolymer is provided, the first block copolymer comprising one or more of (3-acrylamidopropyl)trimethylammonium chloride repeating units, methacryloyloxyethyltrimethylammonium chloride repeating units, and N-dimethyl-N-acrylamidopropylammonium chloride repeating units; A second block copolymer is provided, the second block copolymer comprising one or more repeating units of sodium 2-acrylamide-2-methyl-1-propanesulfonate, dietherazole repeating units, and vinylpyridine phosphate repeating units; The first block copolymer and the second block copolymer are mixed to obtain an adhesive, wherein the adhesive comprises repeating acrylic units.

10. The preparation method according to claim 9, characterized in that, The method for preparing the first block copolymer includes: Acrylamide, poly(ethylene glycol acrylate), (3-acrylamidopropyl)trimethylammonium chloride and solvent were mixed and treated to obtain the raw material solution; The raw material solution and the initiator are mixed and reacted at 60-80°C for 10-14 hours to obtain the first block copolymer.

11. The preparation method according to claim 9, characterized in that, The method for preparing the second block copolymer includes: Acrylamide, acrylic acid, sodium 2-acrylamido-2-methyl-1-propanesulfonate, and solvent were mixed and treated to obtain a raw material solution; The raw material solution and the initiator are mixed and reacted at 60-80°C for 10-14 hours to obtain the second block copolymer.

12. The preparation method according to claim 10 or 11, characterized in that, The initiator includes one or more of 2,2-azobis(2-methylpropylimidazolium) hydrochloride, ammonium persulfate, and potassium persulfate.

13. A battery device, characterized in that, It includes any one of the battery cells according to claims 1-6.

14. An electrical appliance, characterized in that, Includes the battery cell according to any one of claims 1-6 or the battery device according to claim 13.

Images