Battery monomer, preparation method thereof and power utilization device

Abstract

The invention discloses a battery monomer, a preparation method thereof and a power utilization device. The battery monomer comprises an isolating membrane, the isolating membrane comprises a base membrane and a coating located on at least one side of the base membrane, the coating comprises a binder, the porosity of the binder is 30%-70%, the binder comprises secondary particles, the secondary particles comprise a plurality of primary particles, the primary particles comprise first particles and second particles, the Dv50 particle size of the first particles is larger than the Dv50 particle size of the second particles, and the Dv50 particle size of the second particles is larger than the Dv50 particle size of the first particles. The second particles include an acrylate-based copolymer. And the electrolyte can freely enter and exit from the coating, so that the ionic conductivity is improved, and the cycle performance of the battery monomer is improved.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to battery cells, methods for their preparation, and electrical devices. Background Technology

[0002] Secondary batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, but also widely used in electric vehicles such as electric bicycles, electric motorcycles and electric cars, as well as in military equipment and aerospace and other fields.

[0003] To meet usage requirements, rechargeable batteries typically need to have good cycle performance. Taking lithium-ion batteries as an example, a separator coating is used during the molding process. The separator coating (usually a polymer) itself has extremely low ionic conductivity. Due to the coating, some channels in the separator are blocked, affecting the migration of lithium ions in the electrolyte, increasing the internal resistance of the lithium-ion battery, and thus reducing the cycle performance of the lithium-ion battery. Summary of the Invention

[0004] In view of the technical problems existing in the background art, this application provides a battery cell that aims to improve the ionic conductivity of the separator and improve the cycle performance of the battery cell.

[0005] In one aspect of this application, a battery cell is provided. In some embodiments of this application, the battery cell includes a separator, the separator including a base film and a coating located on at least one side of the base film, the coating including an adhesive, the adhesive having a porosity of 30%-70%, the adhesive including secondary particles, the secondary particles including a plurality of primary particles, the primary particles including a first particle and a second particle, the first particle having a Dv50 particle size larger than the second particle's Dv50 particle size, and the second particle including an acrylate copolymer.

[0006] The first particle has a larger Dv50 particle size than the second particle. Due to the natural packing characteristics of particles of different sizes, the second particle can fill the gaps between the first particles or cover part of the surface of the first particles, forming some internal channels. The electrolyte can freely enter and exit the interior of the coating, which is beneficial to improving ionic conductivity, reducing some of the internal resistance of the battery cell, and thus improving the cycle performance of the battery cell. The second particle includes acrylate copolymers, which can act as a binder, allowing the binder to adhere to the base film. The high porosity of the binder is more conducive to the free entry and exit of the electrolyte inside the coating.

[0007] In some embodiments of this application, the Dv50 particle size of the binder is 6μm-20μm. Therefore, the binder has a suitable particle size, which is beneficial for improving the adhesion strength between the coating and the base film, making the coating less prone to peeling off, and maintaining good stability during charging and discharging; furthermore, it helps to shorten the ion transport path, further reducing the resistance of the battery cell.

[0008] In some embodiments of this application, the specific surface area of ​​the adhesive is 1m². 2 / g-10m 2 / g. Therefore, the binder has a rich porous structure, which is beneficial for improving ionic conductivity.

[0009] In some embodiments of this application, the pore diameter of the binder is 0.05 μm-2 μm. This facilitates ion migration in the electrolyte, thereby further improving ionic conductivity.

[0010] In some embodiments of this application, the tap density of the adhesive is 0.2 g / cm³. 3 -1.0g / cm 3 A lower tap density can indirectly reflect that the binder has a higher porosity, and higher porosity is beneficial for improving ionic conductivity.

[0011] In some embodiments of this application, the Dv50 particle size of the first particle is 1μm-5μm, and / or the Dv50 particle size of the second particle is 50nm-500nm. Therefore, the significant difference in Dv50 particle size between the second and first particles is beneficial for the second particle to fill the gaps between the first particles or cover part of the surface of the first particles, thereby facilitating the formation of a rich porous structure and promoting ion transport within the coating.

[0012] In some embodiments of this application, the first particle comprises at least one of an inorganic material and an organic polymer. The inorganic material includes at least one of alumina, titanium dioxide, boehmite, and silicon dioxide, and the organic polymer includes at least one of polystyrene, polymethyl methacrylate, polyacrylamide, and polyethylene. The first particle, made of the aforementioned materials, exhibits good temperature resistance and is not easily deformed at high temperatures, thus serving as a framework. The second particle, with its smaller particle size, can fill the gaps between the first particles or cover part of the surface of the first particles, forming a porous structure.

[0013] In some embodiments of this application, the glass transition temperature of the organic polymer is 50°C-150°C. Therefore, the organic polymer possesses a certain degree of hardness, can form a stable framework structure, is not easily deformed, and thus facilitates the formation of pore channels.

[0014] In some embodiments of this application, the reactive monomers forming the acrylate copolymer include at least two selected from ethyl acrylate, butyl acrylate, methyl methacrylate, hydroxyethyl acrylate, acrylonitrile, styrene, and acrylic acid. This is beneficial for improving the adhesive properties and solvent resistance of the acrylate copolymer.

[0015] In some embodiments of this application, the glass transition temperature of the acrylate copolymer is -50°C to 80°C. Therefore, the acrylate copolymer exhibits good adhesive properties.

[0016] In some embodiments of this application, the primary particles further include a dispersant, which includes at least one of sodium polyacrylate, sodium polymethacrylate, polypropylene ether, polyethylene glycol, polyvinylpyrrolidone, and polyacrylic acid. This is beneficial for improving the electrochemical stability of the binder, thereby further improving the cycle performance of the battery cell.

[0017] In another aspect of this application, a method for preparing a battery cell is proposed. In some embodiments of this application, the method for preparing a battery cell includes the step of forming a separator membrane. Forming the separator membrane includes: preparing a mixture, wherein preparing the mixture includes mixing a first dispersion and an acrylic latex, wherein the dispersed phase in the first dispersion includes first particles, the acrylic latex includes an acrylic copolymer, and the Dv50 particle size of the first particles is larger than the Dv50 particle size of the acrylic copolymer; granulating the mixture to obtain a binder, the binder having a porosity of 30%-70%, the binder including secondary particles, the secondary particles including a plurality of primary particles, the primary particles including the first particles and the acrylic copolymer; and disposing the binder on at least one side of a base film to form a coating to obtain the separator membrane.

[0018] Therefore, the acrylate copolymer has adhesive properties, which can make the adhesive adhere to the base film. The first particle and the acrylate copolymer have different particle sizes. The first particle has a larger particle size, which can form a framework structure. The acrylate copolymer has a smaller particle size, which can fill the gaps between the first particles or cover part of the surface of the first particles, forming a porous structure. The adhesive obtained by granulation has a rich porous structure and a high porosity, which is conducive to the free flow of electrolyte inside the coating. This is beneficial to improving ionic conductivity, reducing the internal resistance of the battery, and thus improving the cycle performance of the battery cell.

[0019] In some embodiments of this application, the preparation of the mixture includes mixing a first dispersion, an acrylic latex, a dispersant, and water to obtain the mixture; wherein the mass ratio of the first particle, the acrylic copolymer, and the dispersant is (10–90):(10–90):(1–15). This facilitates the formation of a uniform slurry, making it easier to form relatively uniform spherical particles through granulation.

[0020] In some embodiments of this application, the sum of the mass contents of the first particle, the acrylate copolymer, and the dispersant in the mixture is 10%-30%. This is beneficial for forming more uniform particles.

[0021] In some embodiments of this application, the viscosity of the mixture is 100 mPa·s to 800 mPa·s. This results in good flowability, which helps reduce product adhesion to the inner wall of the granulator, thereby facilitating continuous granulation and increasing product yield.

[0022] In some embodiments of this application, the preparation of the acrylate latex includes the following steps: adding deionized water, an initiator, a pH buffer, and an electrolyte to a reaction vessel; raising the temperature in the reaction vessel to 50°C–80°C; adding reactive monomers dropwise to the reaction vessel and reacting for 6–12 hours to obtain a reaction product, wherein the reactive monomers include at least two of ethyl acrylate, butyl acrylate, methyl methacrylate, hydroxyethyl acrylate, acrylonitrile, styrene, and acrylic acid; adjusting the mass content of the acrylate copolymer in the reaction product to 30%–45% and the pH to 3–9 to obtain the acrylate latex. This facilitates control of the monomer reaction rate and improves monomer utilization.

[0023] In some embodiments of this application, the initiator includes at least one of potassium persulfate and ammonium persulfate. The aforementioned initiators can rapidly initiate the polymerization reaction of monomers, promoting the formation of acrylate copolymers.

[0024] In some embodiments of this application, the pH buffer includes NaHCO3. The above materials can adjust the pH value of the reaction system, keeping it within a relatively stable pH range, thereby promoting the polymerization reaction.

[0025] In some embodiments of this application, the electrolyte includes KCl. The aforementioned electrolyte can, to a certain extent, adjust the particle size of the latex particles, thereby facilitating the obtaining of acrylate copolymers with smaller particle sizes.

[0026] In another aspect, this application proposes an electrical device. In some embodiments of this application, the electrical device includes the battery cell described above or a battery cell prepared using the method described above. Therefore, the electrical device possesses all the features and advantages of the battery cell described above, which will not be repeated here.

[0027] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0028] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the alternative embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0029] Figure 1 This is a schematic diagram of a battery cell according to one embodiment of this application;

[0030] Figure 2 yes Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown.

[0031] Figure 3 This is a SEM image of an adhesive according to one embodiment of this application;

[0032] Figure 4 This is a SEM image of an adhesive according to one embodiment of this application;

[0033] Figure 5 This is a schematic diagram of a battery module according to an embodiment of this application;

[0034] Figure 6 This is a schematic diagram of a battery pack according to one embodiment of this application;

[0035] Figure 7 yes Figure 6 An exploded view of a battery pack according to an embodiment of this application is shown;

[0036] Figure 8 This is a schematic diagram of an electrical device according to an embodiment of this application;

[0037] Figure 9 This is the infrared absorption spectrum of an adhesive according to one embodiment of this application;

[0038] Figure 10 This is a DSC test curve of an adhesive according to one embodiment of this application.

[0039] Explanation of reference numerals in the attached figures:

[0040] 1 Battery cell; 11 Casing; 12 Electrode assembly; 13 Cover plate; 2 Battery module; 3 Battery pack; 31 Upper casing; 32 Lower casing; 100 Secondary particles; 110 Primary particles; 120 Pores; 111 First particle; 112 Second particle. Detailed Implementation

[0041] The embodiments of this application are described in detail below, with examples of these embodiments shown in the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0042] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0043] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are open-ended expressions, meaning they include what is specified in this application but do not exclude other aspects.

[0044] In the description of this application, all figures disclosed herein, whether or not the words "approximately" or "about" are used, are approximate values. Each figure may vary by less than 10% or by a difference that is considered reasonable by one of the art, such as 1%, 2%, 3%, 4%, or 5%.

[0045] 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 expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are 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 "ab" 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.

[0046] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. "First feature" and "second feature" may include one or more of the indicated feature.

[0047] In the description of this application, "multiple" means two or more.

[0048] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0049] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0050] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0051] 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.

[0052] To meet usage requirements, rechargeable batteries typically need good cycle performance. Taking lithium-ion batteries as an example, the separator is usually formed by a base film and an adhesive layer (separator coating) on ​​the base film. During the lithium-ion battery molding process, the adhesive layer can bond the positive and negative electrode plates to the separator. The separator coating is generally a polymer, and the separator coating itself has extremely low ionic conductivity. Due to the coating, some channels on the base film are blocked, affecting the migration of lithium ions in the electrolyte, increasing internal resistance, and reducing cycle performance.

[0053] In related technologies, PVDF (polyvinylidene fluoride) is used as a binder to be applied to the surface of the base membrane to form a membrane coating. However, due to the need to protect the environment and human health, the use of fluorine-containing materials needs to be restricted. Therefore, it is necessary to try to use other materials to replace the PVDF particles used in the membrane coating.

[0054] Acrylic copolymers possess adhesive properties and exhibit good stability in the presence of electrolytes, making them suitable for forming membrane coatings. However, using only acrylic copolymers as binders on a base membrane to form a coating results in low ionic conductivity, which is detrimental to lithium-ion migration. Porous structures can be formed by stacking particles of different sizes, with larger particles serving as the source of pores and creating larger gaps between adjacent particles. However, if acrylic copolymers are chosen for the larger particles and other materials for the smaller particles, the acrylic copolymers will form a film, encapsulating the smaller particles and failing to create a binder with sufficient porosity. Therefore, in this application, the binder includes first particles and second particles. The second particles are acrylate copolymers with adhesive properties, allowing the binder to adhere to the base film. By stacking first and second particles with different Dv50 particle sizes, the first particles with larger Dv50 particle sizes can form a framework, while the second particles with smaller Dv50 particle sizes can fill the gaps between the first particles or cover part of the surface of the first particles, forming internal channels that allow the electrolyte to freely enter and exit the coating, thereby improving ionic conductivity, reducing internal resistance in this area, and improving the cycle performance of the battery. The first and second particles are stacked to form primary particles, and multiple primary particles form secondary particles, thus obtaining the binder. The binder has high porosity, and the rich pore structure can further promote ion migration, thereby further improving the cycle performance of the battery cell.

[0055] The battery cells disclosed in this application include lithium-ion batteries, and these battery cells can be used in electrical devices that use batteries as a power source or in various energy storage systems that use batteries as energy storage elements. Electrical devices may include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys may include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0056] In one aspect of this application, a battery cell is provided. In some embodiments, the battery cell may include an outer packaging. The outer packaging can be used to encapsulate electrode components and electrolyte. In some embodiments, the outer packaging of the battery cell may be a rigid shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell may also be a flexible package, such as a pouch. The material of the flexible package may be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0057] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 Here is a square-structured battery cell 1 as an example.

[0058] In some embodiments, refer to Figure 2 The outer packaging may include a housing 11 and a cover plate 13. The housing 11 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 11 has an opening communicating with the receiving cavity, and the cover plate 13 can be placed over the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator can be formed into an electrode assembly 12 by a winding process or a stacking process. The electrode assembly 12 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 12. The number of electrode assemblies 12 contained in a single battery cell 1 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0059] In some embodiments of this application, the battery cell includes a separator, the separator including a base film and a coating located on at least one side of the base film, and a coating adhesive. The porosity of the adhesive can be 30%-70%, and the adhesive can include secondary particles, see reference. Figure 3 and Figure 4 The secondary particles 100 include a plurality of primary particles 110. The primary particles 110 include a first particle 111 and a second particle 112. The Dv50 particle size of the first particle 111 is larger than the Dv50 particle size of the second particle 112. The second particle 112 includes an acrylate copolymer.

[0060] In some embodiments, the secondary particles 100 are formed by the stacking of a plurality of primary particles 110.

[0061] In some embodiments of this application, the porosity of the adhesive is 30%-70%, for example, the porosity of the adhesive can be 30%, 40%, 50%, 60%, 70%, etc.

[0062] The porosity test method for the adhesive is as follows: 1. Pretreatment: Take an appropriate amount of sample in a 3 / 8 sample tube, heat and degas under vacuum for 2 hours, and weigh the total weight after cooling to room temperature. Subtract the mass of the sample tube to obtain the sample mass. 2. Test: Place the sample tube into the workstation. Under constant temperature and low temperature, the adsorbed gas is adsorbed onto the material under a series of gradually increasing pressures. The pore size distribution of the porous material is characterized by the curve of the volume of each pore size versus the corresponding partial pressure. 3. Adsorbed gas: Nitrogen; Adsorption pressure (ratio of adsorption pressure to saturated vapor pressure) range: 0-0.995-0; Test atmosphere: High-purity liquid nitrogen atmosphere.

[0063] The second particle comprises an acrylate copolymer, which has adhesive properties, allowing the binder to adhere to the base film. The acrylate copolymer exhibits good stability in the electrolyte, which is beneficial for improving the cycle stability of the battery. The first and second particles have different Dv50 particle sizes. During the stacking process, the first particle with a larger Dv50 particle size can act as a framework to build pores, while the second particle with a smaller Dv50 particle size can fill the gaps between the first particles or cover part of the surface of the first particles, creating some channels. The first and second particles stack to form primary particles, and multiple primary particles stack to form secondary particles, thus obtaining the binder. The binder has a high porosity (rich pore structure), allowing the electrolyte to freely enter and exit the coating through the pore structure, thereby improving ion mobility, reducing internal resistance, reducing energy consumption on internal resistance during charging and discharging, and thus improving the cycle performance of the battery.

[0064] In some embodiments of this application, the base film may include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.

[0065] In some embodiments of this application, reference is made to Figure 3 The binder includes secondary particles 100, which have pores 120. The pore diameter of the binder can be 0.05 μm to 2 μm, for example, 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, etc. A pore diameter within the above range is beneficial for further improving ion mobility, thereby further improving the cycle performance of the battery cell.

[0066] The method for testing the pore diameter of the adhesive is as follows: Prepare an adhesive sample, then perform gold sputtering, and use a scanning electron microscope to obtain the morphology of the adhesive. With an accelerating voltage of 10.00KV, a working distance of 14mm, and a magnification of 3000x, adjust the focus to ensure the sample is clear, start measuring the pore diameter of the particles and mark them, then adjust the sample position, and continuously measure the pore diameter up to 100 times. Calculate the average pore diameter as the pore diameter.

[0067] In some embodiments of this application, the Dv50 particle size of the binder can be 6μm-20μm, for example, the Dv50 particle size of the binder can be 6μm, 8μm, 10μm, 13μm, 15μm, 17μm, 20μm, etc. A Dv50 particle size within the above range is beneficial for forming a coating with uniform thickness and a smooth surface, thereby improving the wetting effect between the separator and the electrolyte, and further improving the ion transport effect; moreover, it is beneficial for improving the adhesion strength between the coating and the base film, thereby improving the stability and cycle performance of the battery cell.

[0068] It is understood that "Dv50 particle size" is a well-known definition in the art and can be measured by methods known in the art, for example, the following methods can be used for measurement:

[0069] The test was conducted using a laser particle size analyzer (Malvern Mastersizer 3000), with a helium-neon red light source as the main light source. A clean small beaker was prepared by adding 1g of the sample to be tested and 20ml of deionized water. The sample was sonicated at 53kHz / 120W for 5 minutes to ensure complete dispersion. The laser particle size analyzer was then turned on, and the optical path system was cleaned before automatically testing the background. The sonicated solution was stirred to ensure uniform dispersion, then placed into the sample cell as required. Particle size measurement was then initiated, and the results were read from the instrument.

[0070] In some embodiments of this application, the specific surface area of ​​the adhesive is 1m². 2 / g-10m 2 / g, for example, the specific surface area of ​​the adhesive can be 1m². 2 / g、3m 2 / g、5m 2 / g、8m 2 / g, 10m 2 / g, etc. Therefore, the binder possesses a rich porous structure, which is beneficial for further improving ionic conductivity.

[0071] The specific surface area of ​​powder samples was analyzed using nitrogen gas adsorption specific surface area analysis. The standard pretreatment method was 70℃ / 12H. Adsorbed gas: nitrogen; adsorption pressure: 0-0.995-0. Pretreatment: A suitable amount of sample was placed in a 3 / 8 sample tube, heated under vacuum for 2 hours to degas, and after cooling to room temperature, the total weight was weighed. The sample mass was obtained by subtracting the mass of the sample tube. Testing: The sample tube was placed in a workstation at a constant low temperature, and the amount of gas adsorbed on the solid surface under different adsorption pressures was measured. Based on the BET multilayer adsorption theory and its formula, the monolayer adsorption capacity of the sample was calculated, thereby determining the specific surface area per unit mass of the solid sample.

[0072] In some embodiments of this application, the primary particles include a first particle and a second particle, wherein the Dv50 particle size of the first particle is larger than that of the second particle.

[0073] In some embodiments of this application, the Dv50 particle size of the first particle can be 1μm-5μm, and the Dv50 particle size of the second particle can be 50nm-500nm. For example, the Dv50 particle size of the first particle can be 1μm, 2μm, 3μm, 4μm, 5μm, etc., and the Dv50 particle size of the second particle can be 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, etc. Thus, the significant difference in Dv50 particle size between different particles is beneficial for the second particle to fill the gaps between the first particles or cover part of the surface of the first particles, thereby forming pores during the stacking process, providing porous channels for ion conduction, and thus improving ionic conductivity.

[0074] In some embodiments of this application, the first particle may include at least one of inorganic materials and organic polymers. Selecting specific inorganic materials and / or organic polymers for the first particle is more beneficial for improving the cycle performance of the battery.

[0075] In some embodiments, the first particle may include an inorganic material, wherein the inorganic material may include at least one of alumina, titanium dioxide, boehmite, and silicon dioxide.

[0076] In other embodiments, the first particle may include an organic polymer, wherein the organic polymer may include at least one of polystyrene, polymethyl methacrylate, polyacrylamide, and polyethylene.

[0077] The first particle of the aforementioned material has good temperature resistance and is not easily deformed at high temperatures, thus serving as a framework. The second particle fills the gaps between the first particles or covers part of the surface of the first particles, forming a porous structure. The use of the aforementioned inorganic materials and / or organic polymers is more conducive to improving the cycle performance of the battery.

[0078] In some embodiments of this application, the glass transition temperature of the organic polymer can be between 50°C and 150°C. For example, the glass transition temperature of the organic polymer can be 50°C, 80°C, 100°C, 120°C, 130°C, 150°C, etc. Therefore, the organic polymer has good stability and is not easily deformed at higher temperatures, which is beneficial for forming a framework so that the second particle can fill the gaps or cover part of the surface of the first particle.

[0079] In this application, the glass transition temperature of the material is determined by DSC (differential scanning calorimetry).

[0080] In some embodiments, the second particle may comprise an acrylate copolymer. In some embodiments, the acrylate copolymer may be polymerized from at least two monomers selected from ethyl acrylate, butyl acrylate, methyl methacrylate, hydroxyethyl acrylate, acrylonitrile, styrene, and acrylic acid. Therefore, the second particle exhibits better adhesion and solvent resistance, which is beneficial for improving the stability of the adhesive and the bond strength between the coating and the base film.

[0081] In some embodiments, the glass transition temperature of the acrylate copolymer can be -50°C to 80°C. For example, the glass transition temperature of the acrylate copolymer can be -50°C, -30°C, -10°C, 0°C, 10°C, 30°C, 50°C, 80°C, etc. Therefore, the acrylate copolymer has good adhesion properties, which is beneficial for improving the adhesion strength between the coating and the base film.

[0082] In this application, no special limitation is made on the Dv50 particle size of the primary particles.

[0083] The particle size determination method is as follows: The Dv50 particle size of the material can be tested using methods known in the art. For example, it can be determined using a laser particle size analyzer (such as the Malvern Master Size 3000) according to standard GB / T 19077-2016. As an example, the test can be performed as follows: Take a clean small beaker, add 1g of the sample to be tested, add 20ml of deionized water, and sonicate at 53kHz / 120W for 5min to ensure complete dispersion of the sample. Turn on the laser particle size analyzer, clean the optical path system, and automatically test the background. Stir the sonicated test solution to ensure uniform dispersion, place it in the sample cell as required, and begin measuring the particle size. The measurement result can be read from the instrument.

[0084] In some embodiments of this application, in addition to the first and second particles, the primary particles may further include a dispersant, wherein the dispersant may include at least one of sodium polyacrylate, sodium polymethacrylate, polypropylene ether, polyethylene glycol, polyvinylpyrrolidone, and polyacrylic acid. Adding the above-mentioned dispersant is beneficial to improving the uniformity and bonding performance of the adhesive, thereby improving the stability of the adhesive in the electrolyte.

[0085] In some embodiments of this application, the tap density of the adhesive can be 0.2 g / cm³. 3 -1.0g / cm 3 For example, the tap density of the adhesive can be 0.2 g / cm³. 3 0.3g / cm 3 0.5g / cm 3 0.7g / cm 3 0.9g / cm 31.0g / cm 3 The binder has a low tap density and high porosity, which is beneficial for ion transport and diffusion, thereby improving the cycle performance of the battery cell.

[0086] In this application, tapped density refers to the mass per unit volume of powder in a container after it has been tapped under specified conditions.

[0087] In some embodiments of this application, the battery cell may be a lithium-ion battery cell.

[0088] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active metal ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0089] In some embodiments, the positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer including a positive active material.

[0090] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0091] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0092] In some embodiments of this application, the positive electrode active material may include lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (e.g., LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ()), and lithium nickel cobalt aluminum oxides (e.g., LiNi) 0.8 Co 0.15 Al 0.05 At least one of O2).

[0093] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of positive electrode active materials in this application, the molar Li content refers to the initial state of the material, i.e., before feeding. When the positive electrode active material is applied to the battery system, the molar Li content changes after charge-discharge cycles.

[0094] In the examples of positive electrode active materials in this application, the molar content of oxygen is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of oxygen will fluctuate.

[0095] In some embodiments of this application, the positive electrode active material layer may optionally include a binder. As an example, the binder in the positive electrode active material layer may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0096] In some embodiments of this application, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent in the positive electrode active material layer may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0097] In some embodiments of this application, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0098] In some embodiments of this application, the negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector.

[0099] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0100] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0101] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, tin-based materials, and lithium titanate, etc. Tin-based materials may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used.

[0102] In some embodiments, the negative electrode active material layer may optionally include a binder. The binder in the negative electrode active material layer may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0103] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. The conductive agent in the negative electrode active material layer may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0104] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0105] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0106] In some embodiments of this application, the electrolyte includes an electrolyte salt and a solvent.

[0107] In some embodiments of this application, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(trifluoromethanesulfonyl)imide, lithium fluorosulfonate, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0108] In some embodiments of this application, the solvent may include at least one of ethylene carbonate (EC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), propylene carbonate, butene carbonate, dimethyl carbonate, methyl propyl carbonate, dipropyl carbonate, ethyl propyl carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, and γ-butyrolactone.

[0109] In some embodiments of this application, the electrolyte may also include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0110] In some embodiments, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0111] Figure 5 This is battery module 2 as an example. (See reference...) Figure 5 In battery module 2, multiple battery cells 1 can be arranged sequentially along the length of battery module 2. Of course, they can also be arranged in any other way. Furthermore, these multiple battery cells 1 can be fixed in place using fasteners.

[0112] Optionally, the battery module 2 may also include a housing with a receiving space in which multiple battery cells 1 are received.

[0113] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0114] Figure 6 and Figure 7 This is battery pack 3 as an example. (See reference...) Figure 6 and Figure 7 The battery pack 3 may include a battery box and multiple battery modules 2 disposed within the battery box. The battery box includes an upper box 31 and a lower box 32, with the upper box 31 covering the lower box 32 to form a closed space for accommodating the battery modules 2. The multiple battery modules 2 can be arranged in any manner within the battery box.

[0115] In some embodiments, the battery cell, battery module, or battery pack may be a power source for the electrical device or an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0116] Electrical devices can be equipped with individual battery cells, battery modules, or battery packs depending on their usage requirements.

[0117] Figure 8 This is an example of an electrical device. This device can be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0118] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0119] In another aspect of this application, a method for preparing the aforementioned battery cell is provided. In some embodiments of this application, the method for preparing the aforementioned battery cell includes the step of forming a separator, wherein forming the separator includes the following steps:

[0120] S100: Preparation of mixture.

[0121] In some embodiments of this application, preparing the mixture includes mixing a first dispersion and an acrylic latex.

[0122] In some embodiments of this application, the preparation of the mixture includes mixing a first dispersion, an acrylic latex, a dispersant, and water to obtain the mixture.

[0123] In some embodiments of this application, the dispersed phase in the first dispersion includes first particles, which comprise at least one of inorganic materials and organic polymers. The inorganic materials may include at least one of alumina, titanium dioxide, boehmite, and silica, while the organic polymers may include at least one of polystyrene, polymethyl methacrylate, polyacrylamide, and polyethylene. These first particles possess good temperature resistance and can serve as a framework, which is beneficial for forming a porous structure.

[0124] In some embodiments of this application, the first particles in the first dispersion include an organic polymer, the solvent in the first dispersion includes water, and the first dispersion includes at least one of a polycarboxylic acid dispersant and a hydrophilic functional monomer.

[0125] In some embodiments, the first dispersion comprises a polycarboxylic acid dispersant, which may include at least one of polyacrylic acid (PAA), sodium polyacrylate (PAAS), maleic acid-acrylic acid copolymer (MA-AA), etc. Adding a polycarboxylic acid dispersant can promote the dispersion of the first particles in the solvent and maintain good dispersion stability, preventing the first particles from settling.

[0126] In some embodiments of this application, the first particle comprises an organic polymer, which can be dispersed and emulsified to form a first dispersion. Specifically, a suitable wetting and dispersing agent, such as a polycarboxylic acid dispersant, can be selected according to the characteristics of the first particle, added to water, and after being dispersed evenly, the first particle is added, and the rotation speed is adjusted to disperse the first particle to a suitable particle size to obtain a first dispersion. The Dv50 particle size of the first particle in the first dispersion is 1 μm to 5 μm.

[0127] In other embodiments of this application, the first particle comprises an organic polymer that can self-emulsify to form a first dispersion, such that the Dv50 particle size of the first particle in the first dispersion is 1 μm to 5 μm. Specifically, self-emulsification refers to introducing a hydrophilic functional monomer, allowing the organic polymer to be dispersed in water to form a first dispersion. In some embodiments, the hydrophilic functional monomer may include acrylic acid.

[0128] In some embodiments of this application, acrylate latexes include acrylate copolymers, which can be polymerized from at least two monomers selected from ethyl acrylate, butyl acrylate, methyl methacrylate, hydroxyethyl acrylate, acrylonitrile, styrene, and acrylic acid. Acrylate copolymers exhibit good adhesive properties and good stability in the presence of electrolyte. Using these materials to prepare binders is beneficial for improving the performance of battery cells.

[0129] In some embodiments of this application, the Dv50 particle size of the first particle is larger than that of the acrylate copolymer, and the mass ratio of the first particle, the acrylate copolymer, and the dispersant is (10-90):(10-90):(1-15). This facilitates the formation of a binder with a rich porous structure through granulation.

[0130] In some embodiments of this application, the dispersant includes at least one of sodium polyacrylate, sodium polymethacrylate, polypropylene ether, polyethylene glycol, polyvinylpyrrolidone, and polyacrylic acid.

[0131] In some embodiments of this application, the total mass content of the first particle, the acrylate copolymer, and the dispersant in the mixture can be 10%-30%, for example, the total mass content of the first particle, the acrylate copolymer, and the dispersant in the mixture can be 10%, 15%, 20%, 25%, 30%, etc. This facilitates the formation of more uniform spherical particles through granulation.

[0132] In some embodiments of this application, the viscosity of the mixture can be between 100 mPa·s and 800 mPa·s, for example, the viscosity of the mixture can be 100 mPa·s, 200 mPa·s, 300 mPa·s, 500 mPa·s, 700 mPa·s, 800 mPa·s, etc. Therefore, the mixture has good flowability, which helps to form more uniform spherical particles through granulation.

[0133] In some embodiments of this application, the preparation of acrylic latex may include the following steps:

[0134] S110: Add deionized water, initiator, pH buffer and electrolyte to the reaction vessel.

[0135] In some embodiments of this application, the initiator may include at least one of potassium persulfate and ammonium persulfate. This allows for rapid initiation of the polymerization reaction, which is beneficial for shortening the reaction time.

[0136] In some embodiments of this application, the pH buffer may include NaHCO3. This allows the reaction system to be adjusted to a suitable pH value and maintains a relatively stable pH.

[0137] In some embodiments of this application, the electrolyte may include KCl. Therefore, the electrolyte can, to a certain extent, adjust the particle size and morphology of latex particles, which is beneficial for adjusting the particle size of acrylate copolymers.

[0138] The specific materials of the dispersant have been explained above and will not be repeated here.

[0139] In some embodiments, an emulsifier, such as sodium dodecyl sulfonate, may also be added to the reaction vessel.

[0140] In some embodiments, the reaction vessel may be a reaction kettle.

[0141] S120: Raises the temperature in the reaction vessel to 50℃~80℃.

[0142] In some embodiments, the temperature in the reaction vessel can be raised to 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, etc. At these temperatures, the initiator exhibits high activity, and the polymerization reaction of the monomer can be rapidly initiated after its addition.

[0143] S130: Add the reactant monomer dropwise into the reaction vessel and react for 6 to 12 hours to obtain the reaction product.

[0144] In some embodiments of this application, the reactive monomer may include at least two of ethyl acrylate, butyl acrylate, methyl methacrylate, hydroxyethyl acrylate, acrylonitrile, styrene, and acrylic acid.

[0145] Dropwise addition of reactive monomers allows for better control of the amount of various reactive monomers added, as well as the reaction rate and amount of certain monomers, thereby improving monomer utilization.

[0146] In some embodiments of this application, the reaction time can be 6h, 7h, 8h, 10h, 12h, etc. This allows the monomers to react fully, which is beneficial for improving monomer utilization and product yield.

[0147] S140: Adjust the mass content of the acrylate copolymer of the reaction product to 30% to 45% and the pH to 3 to 9 to obtain acrylate latex.

[0148] In some embodiments, the mass content of the reaction product acrylate copolymer can be adjusted to 30%, 32%, 35%, 37%, 40%, 43%, 45%, etc., and the pH can be adjusted to 3, 5, 6, 7, 9, etc., to obtain acrylate latex.

[0149] S200: The mixture is granulated to obtain a binder.

[0150] In some embodiments of this application, the adhesive includes secondary particles, which in turn include a plurality of primary particles. The primary particles may include first particles and acrylate copolymers.

[0151] In some embodiments, the primary particles may include first particles, acrylate copolymers, and dispersants.

[0152] In some embodiments, secondary particles may be formed by the accumulation of multiple primary particles.

[0153] In some embodiments, the Dv50 particle size of the acrylate copolymer can be 50 nm to 500 nm. The acrylate copolymer with a smaller Dv50 particle size can fill the gaps between the first particles or cover part of the surface of the first particles, forming a porous structure during the stacking process, thus promoting the transport and diffusion of ions within the coating.

[0154] In some embodiments of this application, the pore diameter of the adhesive is 0.05 μm to 2 μm. This is beneficial for further improving the ionic conductivity.

[0155] In some embodiments, the Dv50 particle size of the adhesive is 6 μm to 20 μm.

[0156] In some embodiments of this application, the mixture can be granulated by spray drying to obtain a binder with a Dv50 particle size of 6μm to 20μm.

[0157] S300: An adhesive is placed on at least one side of the base film to form a coating to obtain a release membrane.

[0158] In some embodiments of this application, the base film may include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.

[0159] In some embodiments, an adhesive can be applied to at least one side of the base film to form a coating, thereby obtaining a separator. The adhesive has numerous pores, which facilitates ion conduction and thus improves the cycle performance of the battery cell.

[0160] In some embodiments of this application, the adhesive may be sprayed onto at least one side of the base film.

[0161] In some embodiments, the adhesive can be mixed with glue (glue is a solution of adhesive material, which refers to a material with adhesive properties, such as polyacrylic acid, polyvinyl alcohol, and carboxymethyl cellulose), and stirred and mixed evenly in deionized water to obtain a coating slurry with a total mass content of 20% of adhesive and adhesive material. The coating slurry is then evenly applied to the surface of the base film and dried to obtain a release film.

[0162] In some embodiments, the adhesive may be an aqueous solution of carboxymethyl cellulose. The concentration of the adhesive is not specifically limited in this application; those skilled in the art can set and adjust it according to actual needs.

[0163] In this application, a slurry composed of materials with different particle sizes is granulated to obtain a binder. Due to the different particle sizes of the raw materials, a certain amount of pores will be generated during the stacking process. After the binder is applied to the separator and wound into a lithium-ion battery, additional pores that allow the electrolyte to migrate freely are provided, which reduces some of the internal resistance and improves the cycle capacity retention rate of the lithium-ion battery.

[0164] In another aspect of this application, an electrical device is proposed. In some embodiments of this application, the electrical device includes the battery cell described above or a battery cell prepared using the methods described above. Thus, the electrical device includes all the features and advantages of the battery described above, which will not be repeated here.

[0165] In some embodiments, a single battery cell can be used as a power source for an electrical device or as an energy storage unit for an electrical device. Electrical devices may include, but are not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0166] The following specific embodiments illustrate the solution of this application. It should be noted that these embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0167] Example 1

[0168] (1) Preparation of the separating membrane

[0169] Preparation of acrylic latex: The monomers are butyl acrylate, styrene, and acrylic acid, with a mass ratio of butyl acrylate, styrene, and acrylic acid of 36:61:3. Emulsifier (sodium dodecyl sulfonate), electrolyte (KCl), pH buffer (NaHCO3), and a certain amount of deionized water are added to a reaction vessel and stirred until homogeneous. Nitrogen gas is introduced, and initiator (ammonium persulfate) is added. The mixture is stirred, heated to 70°C, and the monomers are added dropwise. The reaction is carried out for 7 hours, then heated to 80°C and held for one hour. The product is then discharged, yielding an acrylic latex with a solid content (mass content of the acrylic copolymer) of 40% and a viscosity of 176 mPa·s.

[0170] A first dispersion (solvent is water, the dispersed phase includes first particles made of polystyrene with a Dv50 particle size of 1.42 μm), acrylic latex (including acrylic copolymers), and a dispersant (polyacrylic acid) were prepared by mixing the first particles, acrylic copolymers, and dispersant in a mass ratio of 45:45:10 with water to form a slurry with a total mass of 18% and a viscosity of 307 mPa·s. The slurry was then granulated using a spray-drying method to produce a binder with a Dv50 particle size of 7.6 μm and a tap density of 0.54 g / cm³. 3 .

[0171] The aforementioned adhesive and glue (an aqueous solution of carboxymethyl cellulose (CMC)) were mixed evenly in deionized water at a solid mass ratio of 100:15 (i.e., the mass ratio of adhesive to CMC was 100:15) to obtain a coating slurry (solid content of 20%, i.e., the sum of the mass contents of adhesive and CMC in the coating slurry was 20%). The coating slurry was then uniformly coated onto the surface of the base film and dried to form a coating, thus obtaining a release membrane. A commercially available PE microporous film with a thickness of 7 μm and an average pore size of 80 nm (from Zhuogao Electronic Technology Co., Ltd.) was used as the base film.

[0172] (2) Preparation of positive electrode sheet

[0173] A positive electrode slurry was prepared by thoroughly mixing polyvinylidene fluoride (PVDF), lithium iron phosphate (LFP), conductive agent carbon black, and N-methylpyrrolidone (NMP) in a mass ratio of 1.4:62.56:0.65:35.39. The positive electrode slurry was then subjected to a 210 g / m³ concentration. 2 The loading is uniformly coated on the positive current collector aluminum foil, and then dried, cold-pressed and cut to obtain the positive electrode sheet.

[0174] (3) Preparation of negative electrode sheet

[0175] Natural graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) were added to deionized water at a mass ratio of 96.5:1.2:0.8:1.5. After thorough mixing, a negative electrode slurry (solid content 64%, i.e., deionized water content 36%) was prepared. This negative electrode slurry was then... 2 The loading amount is coated on the negative electrode current collector copper foil, and then dried, cold pressed and slit to obtain the negative electrode sheet.

[0176] (4) Preparation of electrolyte

[0177] At 25°C, ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain a mixed solvent. Then, LiPF6 is dissolved in the above mixed solvent at a concentration of 1 mol / L to obtain an electrolyte.

[0178] (5) Preparation of secondary batteries

[0179] The positive electrode, separator, and negative electrode are stacked and wound in sequence and hot-pressed to obtain a battery cell. The battery cell is placed in an outer packaging, and the electrolyte prepared in step (4) is added. After encapsulation, standing, formation, aging and other processes, a secondary battery is obtained.

[0180] Example 2

[0181] The difference between Example 2 and Example 1 is that the Dv50 particle size of the polystyrene is 1 μm, the acrylate copolymer is formed by copolymerization of ethyl acrylate and methyl methacrylate with a mass ratio of 72:28, the Dv50 particle size of the acrylate copolymer is 50 nm, and the dispersant is sodium polyacrylate.

[0182] The differences between Examples 2-21 and Example 1 are recorded in Table 1. The remaining steps are the same as in Example 1, and a secondary battery is obtained.

[0183] Comparative Example 1

[0184] Unlike Example 1, an acrylic latex was prepared using the same method as in Example 1 and directly dispersed in deionized water to form a slurry with a viscosity of 78 mPa·s and a mass content of 20.65% acrylic copolymer. Spray drying was then used to form an adhesive with a Dv50 particle size of 6.84 μm. The adhesive prepared in Comparative Example 1 was used to replace the adhesive in Example 1, and a coating slurry was prepared using the same method as in Example 1, forming a coating on a base film to obtain a release film.

[0185] The secondary battery was prepared using the same method as in Example 1.

[0186] Comparative Example 2

[0187] Unlike Example 2, Comparative Example 2 did not use the first dispersion to prepare the slurry for spray drying. Instead, it used only an acrylic latex, a dispersant, and water to obtain the slurry, which was then spray-dried to form binder particles. The binder prepared in Comparative Example 2 was used to replace the binder in Example 2, and the separator and secondary battery were prepared using the same method as in Example 2.

[0188] Table 1

[0189]

[0190]

[0191]

[0192] The pore diameter, porosity, Dv50 particle size, specific surface area, tap density, air permeability of the separator, and capacity retention of the battery in each embodiment and comparative example were tested, and the test results are recorded in Table 2.

[0193] (1) The method for testing the pore diameter of the adhesive is as follows:

[0194] The binder sample was prepared and then sputtered with gold. The morphology of the binder was obtained using a scanning electron microscope. With an accelerating voltage of 10.00 kV, a working distance of 14 mm, and a magnification of 3000, the focus was adjusted to ensure the sample was clear. The pore diameter of the particles was measured and marked. The sample position was then adjusted, and the number of pore diameters was continuously measured up to 100. The average pore diameter was then calculated as the pore diameter.

[0195] (2) The test method for the porosity of the adhesive is as follows:

[0196] 1. Pretreatment: Take an appropriate amount of sample in a 3 / 8 sample tube, heat and degas under vacuum for 2 hours, and weigh the total weight after cooling to room temperature. Subtract the mass of the sample tube to obtain the sample mass. 2. Testing: Place the sample tube into the workstation. Under constant temperature and low temperature, the adsorbed gas is adsorbed onto the test material under a series of progressively increasing pressures. The pore size distribution of the porous material is characterized by a curve showing the volume of each pore size versus the corresponding partial pressure. 3. Adsorbed gas: Nitrogen; Adsorption pressure (ratio of adsorption pressure to saturated vapor pressure) range: 0-0.995-0; Test atmosphere: High-purity liquid nitrogen atmosphere.

[0197] (3) The Dv50 particle size test method is as follows:

[0198] The test was conducted using a laser particle size analyzer (Malvern Mastersizer 3000), with a helium-neon red light source as the main light source. A clean small beaker was prepared by adding 1g of the sample to be tested and 20ml of deionized water. The sample was sonicated at 53kHz / 120W for 5 minutes to ensure complete dispersion. The laser particle size analyzer was then turned on, and the optical path system was cleaned before automatically testing the background. The sonicated solution was stirred to ensure uniform dispersion, then placed into the sample cell as required. Particle size measurement was then initiated, and the results were read from the instrument.

[0199] (4) The method for testing specific surface area is as follows:

[0200] The specific surface area of ​​powder samples was analyzed using nitrogen gas adsorption specific surface area analysis. The standard pretreatment method was 70℃ / 12H. Adsorbed gas: nitrogen; adsorption pressure: 0-0.995-0. Pretreatment: A suitable amount of sample was placed in a 3 / 8 sample tube, heated under vacuum for 2 hours to degas, and after cooling to room temperature, the total weight was weighed. The sample mass was obtained by subtracting the mass of the sample tube. Testing: The sample tube was placed in a workstation at a constant low temperature, and the amount of gas adsorbed on the solid surface under different adsorption pressures was measured. Based on the BET multilayer adsorption theory and its formula, the monolayer adsorption capacity of the sample was calculated, thereby determining the specific surface area per unit mass of the solid sample.

[0201] (5) The test method for tap density is as follows:

[0202] A graduated cylinder containing powder is fixed to a mechanical vibration device. A motor drives the device to vibrate vertically up and down, gradually compacting the powder. Once the set number of vibrations is reached, the vibration stops, and the volume of the graduated cylinder is read. The density of the compacted powder is calculated by dividing mass by volume. Amplitude: 3.0 ± 0.1 mm, vibration frequency: 250 ± 15 times / min, number of vibrations: 5000.

[0203] (6) The air permeability test method for the isolation membrane is as follows:

[0204] Referring to GB / T36363-2018, three pieces of the separator membrane at different locations were cut and tested. The average of the three measurements was taken as the air permeability of the separator membrane. Test conditions: pressure 1.22 kPa, gas volume 100 ml air, test area 6.45 cm². 2 .

[0205] (7) The battery capacity retention rate test steps are as follows:

[0206] At 25°C, the prepared battery was charged to 3.8V at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 3.8V, left to rest for 5 minutes, and then discharged to 2.0V at 1 / 3C. The resulting discharge capacity was recorded as the initial capacity C0. The above steps were repeated for the same battery, and the discharge capacity C of the battery after the nth cycle was recorded. n Then, the battery capacity retention rate P after each cycle n =(C n / C0)×100%. In this application, the battery capacity retention rate after 500 cycles can be used to reflect the difference in cycle performance.

[0207] Table 2

[0208]

[0209]

[0210] The adhesive can be prepared using the method proposed in this application. Figure 3 and Figure 4 SEM images of the adhesive in Example 1 at different magnifications are shown. Figure 3 and Figure 4 As can be seen, the adhesive includes secondary particles with a porous structure. The secondary particles 100 are formed by the accumulation of multiple primary particles 110, and the secondary particles 100 have pores 120. The primary particles 110 include first particles 111 and second particles 112. The second particles 112 can fill the gaps between the first particles 111 or cover part of the surface of the first particles 111. Furthermore, Figure 9 and Figure 10 The infrared absorption spectrum and DSC test curve of the adhesive prepared in Example 1 are respectively obtained from... Figure 9 and Figure 10 It can be seen that the main components of the adhesive prepared in Example 1 are acrylate and styrene. Specifically, this can be seen from the infrared image: 3026 cm⁻¹ -1 It is the stretching vibration peak of the unsaturated CH on the benzene ring; 2952 cm⁻¹ -1 It is the stretching vibration peak of alkane CH; 1728 cm⁻¹ -1 It is the C=O stretching vibration peak in acrylates; 1600 cm⁻¹ -1 1493cm -1 1452cm -1 It is a vibrational peak of the benzene ring skeleton; 1159 cm⁻¹ -1 It is the CO stretching vibration peak in butyl acrylate; 1452 cm⁻¹ -1 It is the in-plane bending vibration peak of the monosubstituted benzene ring =CH; 756 cm⁻¹ -1 696cm -1 The peaks are out-of-plane bending vibration peaks of the monosubstituted benzene ring CH; based on the above absorption peaks, it can be determined that styrene, butyl acrylate, etc. are present. The glass transition temperature of polystyrene is 105℃, and the glass transition temperature of butyl acrylate is -55℃. Based on these factors, the binder prepared in Example 1 is determined to be a composite material of polystyrene combined with styrene-butyl acrylate.

[0211] Comparative Example 1 directly dispersed acrylic latex in deionized water to form a slurry, which was then spray-dried to form binder particles. These particles were then prepared into a coating slurry, applied to the base membrane, and dried to form a coating. Table 2 shows that the air permeability of the separator in Comparative Example 1 was poor, indicating that the porosity of the separator in Comparative Example 1 was low.

[0212] The binder particles prepared in Comparative Example 2 also had low porosity, resulting in poor air permeability of the resulting isolation membrane after forming a coating on the base film.

[0213] As can be seen from Table 2, compared with Comparative Example 1 and Comparative Example 2, in Examples 1 to 21, the binder prepared by the method proposed in this application forms a coating on the base film, resulting in a separator with better air permeability. The coating has abundant pore channels, allowing the electrolyte to freely enter and exit through the pore channels of the coating, which is beneficial to improving the ion conductivity of the separator, reducing the internal resistance of the battery, and improving the cycle capacity retention rate of the battery.

[0214] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," and "other embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0215] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A battery cell, characterized in that, The device includes a release membrane, which comprises a base membrane and a coating located on at least one side of the base membrane. The coating includes an adhesive with a porosity of 30%-70%, and the adhesive includes secondary particles comprising a plurality of primary particles. The primary particles include a first particle and a second particle, wherein the Dv50 particle size of the first particle is larger than that of the second particle, and the second particle comprises an acrylate copolymer.

2. The battery cell according to claim 1, characterized in that, The binder has a Dv50 particle size of 6μm-20μm.

3. The battery cell according to claim 1 or 2, characterized in that, The specific surface area of ​​the adhesive is 1m². 2 / g-10m 2 / g.

4. The battery cell according to any one of claims 1-3, characterized in that, The pore diameter of the adhesive is 0.05μm-2μm.

5. The battery cell according to any one of claims 1-4, characterized in that, The tap density of the adhesive is 0.2 g / cm³. 3 -1.0g / cm 3 .

6. The battery cell according to any one of claims 1-5, characterized in that, The first particle has a Dv50 particle size of 1μm-5μm, and / or the second particle has a Dv50 particle size of 50nm-500nm.

7. The battery cell according to any one of claims 1-6, characterized in that, The first particle comprises at least one of inorganic matter and organic polymer, wherein the inorganic matter comprises at least one of alumina, titanium dioxide, boehmite and silica, and the organic polymer comprises at least one of polystyrene, polymethyl methacrylate, polyacrylamide and polyethylene.

8. The battery cell according to claim 7, characterized in that, The glass transition temperature of the organic polymer is 50℃-150℃.

9. The battery cell according to any one of claims 1-8, characterized in that, The reactive monomers that form the acrylate copolymer include at least two of ethyl acrylate, butyl acrylate, methyl methacrylate, hydroxyethyl acrylate, acrylonitrile, styrene, and acrylic acid.

10. The battery cell according to any one of claims 1-9, characterized in that, The glass transition temperature of the acrylate copolymer is -50℃ to 80℃.

11. The battery cell according to any one of claims 1-10, characterized in that, The primary particles further include a dispersant, which includes at least one of sodium polyacrylate, sodium polymethacrylate, polypropylene ether, polyethylene glycol, polyvinylpyrrolidone, and polyacrylic acid.

12. A method for preparing a single battery cell, characterized in that, The step includes forming a separator membrane, wherein forming the separator membrane includes: The preparation of the mixture includes mixing a first dispersion and an acrylate latex, wherein the dispersed phase in the first dispersion includes first particles, the acrylate latex includes an acrylate copolymer, and the Dv50 particle size of the first particles is larger than the Dv50 particle size of the acrylate copolymer. The mixture is granulated to obtain a binder with a porosity of 30%-70%. The binder comprises secondary particles, which in turn comprise a plurality of primary particles, and the primary particles comprise the first particles and the acrylate copolymer. The adhesive is disposed on at least one side of the base film to form a coating to obtain the release membrane.

13. The method according to claim 12, characterized in that, The preparation of the mixture includes mixing a first dispersion, an acrylate latex, a dispersant, and water to obtain the mixture; wherein the mass ratio of the first particles, the acrylate copolymer, and the dispersant is (10-90):(10-90):(1-15).

14. The method according to claim 13, characterized in that, The total mass content of the first particle, the acrylate copolymer, and the dispersant in the mixture is 10%-30%; and / or the viscosity of the mixture is 100 mPa·s-800 mPa·s.

15. The method according to any one of claims 12-14, characterized in that, The preparation of the acrylate latex includes the following steps: Add deionized water, initiator, pH buffer and electrolyte to the reaction vessel; The temperature in the reaction vessel is raised to 50°C to 80°C; Add the reaction monomer dropwise into the reaction vessel and react for 6 h to 12 h to obtain the reaction product. The reaction monomer includes at least two of ethyl acrylate, butyl acrylate, methyl methacrylate, hydroxyethyl acrylate, acrylonitrile, styrene and acrylic acid. The mass content of the acrylate copolymer in the reaction product is adjusted to 30%–45%, and the pH is adjusted to 3–9 to obtain the acrylate latex.

16. The method according to claim 15, characterized in that, At least one of the following conditions must be met: The initiator includes at least one of potassium persulfate and ammonium persulfate; The pH buffer includes NaHCO3; The electrolyte includes KCl.

17. An electrical device, characterized in that, The battery cell includes any one of claims 1-11 or a battery cell prepared by any one of claims 12-16.

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