Secondary battery cell, battery device and electric device

Abstract

A secondary battery cell, a battery device and an electric device. The secondary battery cell comprises a casing, an electrode assembly and an end cap, wherein at least one end of the casing in a first direction has an opening, the electrode assembly is arranged inside the casing, and the end cap seals the opening. The dimension of the secondary battery cell in the first direction ranges from 220 mm to 500 mm. The electrode assembly comprises a positive electrode sheet, a negative electrode sheet, and a separator, the separator being arranged between the positive electrode sheet and the negative electrode sheet. The separator comprises a porous base film and a heat-resistant layer located on one side or two sides of the porous base film, the heat-resistant layer comprising silicon-containing organic cross-linked resin particles.

Description

Secondary battery cells, battery devices and electrical appliances

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese patent application 202510198880.6, filed on February 21, 2025, entitled “Secondary Battery Cell, Battery Device and Electrical Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to a secondary battery cell, a battery device, and an electrical device. Background Technology

[0004] With the increasingly widespread application of rechargeable battery cells, the demands on them are also growing, such as higher energy density and larger cell sizes. The separator in a rechargeable battery cell plays a crucial role in isolating the positive and negative electrodes and preventing internal short circuits, while its porous structure provides channels for ion transport. As the size of rechargeable battery cells increases, the wettability of the electrolyte on the separator decreases, significantly prolonging the settling time after electrolyte injection and affecting the production efficiency of the rechargeable battery cell. Furthermore, the separator located away from the settling direction of the rechargeable battery cell is prone to poor electrolyte retention or even drying out under gravity, affecting ion transport and the performance of the rechargeable battery cell. Therefore, how to achieve both high energy density and good electrochemical performance in rechargeable battery cells is a pressing technical problem that needs to be solved. Summary of the Invention

[0005] This disclosure provides a secondary battery cell, a battery device, and an electrical device, wherein the secondary battery cell has high energy density, high reliability, and good cycle performance.

[0006] In a first aspect, this disclosure provides a secondary battery cell, including a housing, an electrode assembly, and an end cap. The housing has an opening at at least one end along a first direction, the electrode assembly is disposed inside the housing, and the end cap closes the opening. The secondary battery cell has a dimension of 220mm-500mm in the first direction. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The separator is disposed between the positive electrode and the negative electrode. The separator includes a porous base film and a heat-resistant layer located on one or both sides of the porous base film. The heat-resistant layer includes silicon-containing organic crosslinked resin particles.

[0007] When the separator is heated, the porous base membrane shrinks, causing the silicon-containing organic cross-linked resin particles in the heat-resistant layer to rapidly contact and compress, thus applying a force to the porous base membrane opposite to the direction of thermal shrinkage. The separator of this disclosure has a heat-resistant layer, in which the silicon-containing organic cross-linked resin particles act as a skeletal support, thereby resisting the thermal shrinkage of the porous base membrane and improving the overall heat resistance of the separator. It is understood that the separator has good heat resistance and good resistance to deformation even at high temperatures. Therefore, when used in secondary battery cells, it can reduce the probability of short circuits between the positive and negative electrodes, improving the reliability of the secondary battery cells. The silicon-containing organic cross-linked resin particles of this disclosure have good electrolyte affinity, quickly bonding with the electrolyte during injection, rapidly wetting the separator, and also binding the electrolyte. This gives the separator good electrolyte wettability and retention, and reduces the risk of metal deposition at the edges and tabs of the secondary battery cells, thus enabling the secondary battery cells to have good cycle performance. Compared to inorganic ceramic materials such as boehmite and alumina, the heat-resistant layer of this disclosure uses low-density silicon-containing organic cross-linked resin particles, which enables the secondary battery cell to have a high-quality energy density. Therefore, the secondary battery cell of this disclosure can combine high-quality energy density, high reliability, and good cycle performance.

[0008] In some embodiments, the surface of the silicon-containing organic crosslinked resin particles has hydroxyl groups. The hydroxyl groups have good electrolyte affinity, allowing them to quickly bond with the electrolyte during injection, thus rapidly wetting the separator and binding the electrolyte. This results in the separator having good electrolyte wettability and retention, and reduces the risk of metal deposition at the edges and tabs of the secondary battery cells, thereby enabling the secondary battery cells to have good cycle performance.

[0009] In some embodiments, the hydroxyl content in the silicon-containing organic crosslinked resin particles is 500 μg / g to 700 μg / g. A hydroxyl content within this range is beneficial for improving the electrolyte wettability and liquid retention of the separator, and also helps reduce electrolyte side reactions, thereby further improving the cycle performance of the secondary battery cell.

[0010] In some embodiments, the silicon-containing organic crosslinked resin particles have no melting point. The absence of a melting point in the silicon-containing organic crosslinked resin particles indicates good heat resistance and thermal stability, thereby better resisting the thermal shrinkage of the porous base film, improving the heat resistance of the separator, and enhancing the reliability of the secondary battery cells.

[0011] In some embodiments, the silicon-containing organic crosslinked resin particles have no glass transition temperature. The absence of a glass transition temperature in the silicon-containing organic crosslinked resin particles indicates good heat resistance and thermal stability, thereby better resisting the thermal shrinkage of the porous base film, improving the heat resistance of the separator, and enhancing the reliability of the secondary battery cells.

[0012] In some embodiments, the swelling degree of the silicon-containing organic crosslinked resin particles after being immersed in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 at 60°C for 7 days is less than or equal to 3%. The low swelling degree of the silicon-containing organic crosslinked resin particles in organic solvents results in high structural stability during long-term use of the secondary battery cell, thereby improving the problem of decreased air permeability of the separator during use.

[0013] In some embodiments, the dissolution rate of the silicon-containing organic crosslinked resin particles after immersion at 60°C for 7 days in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 is less than or equal to 3%. The low dissolution rate of the silicon-containing organic crosslinked resin particles in organic solvents indicates high structural stability during long-term use of the secondary battery cell and high chemical stability in the electrolyte, thereby enabling the secondary battery cell to have longer cycle stability.

[0014] In some embodiments, the cyclic voltammetry curve of the silicon-containing organic crosslinked resin particles in the first cycle does not exhibit an oxidation peak in the voltage range of 2.5V to 4.4V. The absence of an oxidation peak in the cyclic voltammetry curve of the silicon-containing organic crosslinked resin particles in the voltage window of ≥2.5V and <4.4V indicates that the silicon-containing organic crosslinked resin particles are stable within this voltage window and do not undergo electrochemical redox reactions. This allows the secondary battery cell to possess a high voltage plateau and high-quality energy density.

[0015] In some embodiments, the silicon-containing organic crosslinked resin particles contain carbon-carbon bonds and silicon-oxygen structures.

[0016] In some embodiments, the silicon-containing organic crosslinked resin particles are a network structure formed with carbon-carbon bonds as the main chain and the side chains contain silicon-oxygen structures.

[0017] In some embodiments, the silicon-containing organic crosslinked resin particles are a network structure formed with carbon-carbon bonds as the main chain, and the side chains contain silicon-oxygen structures and benzene ring structures.

[0018] The rigidity of the benzene ring structure gives silicon-containing organic crosslinked resin particles good heat resistance. By using silicon-containing organic crosslinked resin particles with benzene ring structures in separators, it is possible to better generate forces to resist the shrinkage of porous base membranes, thereby improving the overall thermal shrinkage of the separator, enhancing its heat resistance, and improving the reliability of secondary battery cells.

[0019] In some embodiments, the silicon-containing organic crosslinked resin particles containing carbon-carbon bonds and silicon-oxygen structures include crosslinked structural units, which include divinylbenzene structural units, diethylene glycol divinyl ether structural units, triethylene glycol divinyl ether structural units, diallyl maleate structural units, ethylene glycol dimethacrylate structural units, 1,4-butanediol diacrylate structural units, 1,6-hexanediol diacrylate structural units, 1,8-octanediol diacrylate structural units, trimethylolpropane triacrylate structural units, and pentaerythritol trimethacrylate structural units. One or more of the following structural units: tetraethylene glycol dimethacrylate, dipropylene glycol diacrylate, 2,2,4-trimethyladipyl di[2-ethylaziridinium], 1,1-azeloyl di[2-methylaziridinium], 1,1-(1,3-phenylene dicarbonyl) di[2-methylaziridinium], trimethylolpropane tris(2-methyl-1-aziridinium propionate), trimethylolpropane tris[3-(2-methylaziridinium)propionate], and pentaerythritol tris(3-aziridinium)propionate.

[0020] In some embodiments, the silicon-containing organic crosslinked resin particles include polysilsesquioxane, and the weight-average molecular weight of the polysilsesquioxane is 10,000 to 100,000.

[0021] In some embodiments, the silicone-containing organic crosslinked resin particles comprise polysilsesquioxane, and the polysilsesquioxane has the following structural formula:

[0022] R1 and R2 each independently include an alkyl group with 1-12 carbon atoms, an unsaturated hydrocarbon group with 2-12 carbon atoms, or a phenyl group, n = 50-1000.

[0023] In some embodiments, polysilsesquioxanes comprise at least one of the following structural formulas:

[0024] Ph represents phenyl, n = 50-1000.

[0025] In some embodiments, the bulk density of the heat-resistant layer is 0.4 g / cm³. 3 -1.5g / cm 3 1g / cm can be selected. 3 -1.5g / cm 3 Within this range, the resulting separator exhibits excellent electrolyte wettability and electrolyte retention, thereby improving both the production efficiency of secondary battery cells and their cycle performance.

[0026] In some embodiments, the morphology of the silicon-containing organic cross-linked resin particles includes one or more of spherical, near-spherical, ellipsoidal, and near-ellipsoidal shapes. Spherical, near-spherical, ellipsoidal, and near-ellipsoidal silicon-containing organic cross-linked resin particles have high space utilization, contributing a significant amount of space for electrolyte storage. Therefore, by including one or more of spherical, near-spherical, ellipsoidal, and near-ellipsoidal shapes in the morphology of the silicon-containing organic cross-linked resin particles, it is possible to promote rapid wetting of the separator by the electrolyte while simultaneously storing the electrolyte in the pores of the separator to form ion transport channels, thereby improving the cycle performance and rate performance of the secondary battery cell.

[0027] In some embodiments, the volume distribution particle size Dv50 of the silicon-containing organic crosslinked resin particles is less than 1 μm, and can be selected as 60 nm-800 nm.

[0028] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the silicone organic crosslinked resin particles is 0.2-1.1.

[0029] In some embodiments, the mass percentage of silicon-containing organic crosslinked resin particles in the heat-resistant layer is greater than or equal to 80%.

[0030] In some embodiments, the true density of the silicon-containing organic cross-linked resin particles is 1.0 g / cm³. 3 -1.5g / cm 3 This allows secondary battery cells using the separator membrane disclosed herein to have a higher mass energy density.

[0031] In some embodiments, the heat-resistant layer includes an adhesive, which includes one or more of hydroxyl, carboxyl, carboxylate, ester, epoxy, and amide groups. These groups have good electrolyte affinity, allowing them to quickly bond with the electrolyte during injection and effectively wet the separator.

[0032] In some embodiments, the adhesive accounts for more than or equal to 1% of the mass of the heat-resistant layer.

[0033] In some embodiments, the adhesive includes one or more of the following: polyacrylate adhesives, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0034] In some embodiments, the separator further includes an adhesive layer disposed on at least a portion of the surface of the heat-resistant layer or the porous base membrane, the adhesive layer comprising polymer binder particles having a volume distribution particle size Dv50 of 6 μm-18 μm.

[0035] In some embodiments, the polymer binder particles include one or more of fluoropolymer binder particles and non-fluoropolymer binder particles.

[0036] In some embodiments, the polymer binder particles comprise an aggregate of primary particles.

[0037] In some embodiments, the ratio of the volume distribution particle size Dv50 of the silicon-containing organic crosslinked resin particles to the average pore size of the porous base membrane is greater than or equal to 1.2. This can reduce pore clogging problems and improve the air permeability and ion conduction properties of the separator.

[0038] In some embodiments, the average pore size of the porous base film is 25 nm-80 nm.

[0039] In some embodiments, the porosity of the porous base membrane is 25%-60%, optionally 30%-40%.

[0040] In some embodiments, the thickness of the porous base film is 3μm-11μm, and optionally 3μm-7μm.

[0041] In some embodiments, the thickness of the heat-resistant layer is 0.4 μm-5 μm.

[0042] In some embodiments, the electrolyte wetting length of the separator is greater than or equal to 40 mm, and can be selected as 50 mm-60 mm.

[0043] In some embodiments, the total thickness of the separator is 4.5 μm-14 μm.

[0044] In some embodiments, the porosity of the separator is 25%-60%, optionally 40%-48%.

[0045] In some embodiments, the positive electrode sheet 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, wherein the porosity of the positive electrode film layer is 15%-30%.

[0046] In some embodiments, the secondary battery cell includes an electrolyte with a viscosity of less than or equal to 5 mPa·s at 25°C. This helps to improve the electrolyte wettability of the secondary battery cell.

[0047] In some embodiments, the secondary battery cell includes an electrolyte, the electrolyte having an ionic conductivity of 8 mS / cm-16 mS / cm at 25°C.

[0048] Secondly, this disclosure provides a battery device comprising a plurality of secondary battery cells according to the first aspect of this disclosure.

[0049] Thirdly, this disclosure provides an electrical device that includes a secondary battery cell according to the first aspect of this disclosure or a battery device according to the second aspect of this disclosure. Attached Figure Description

[0050] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments of this disclosure will be briefly described below. Obviously, the drawings described below are merely some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on the drawings without any creative effort.

[0051] Figure 1 shows a schematic diagram of a secondary battery cell provided in some embodiments of this disclosure.

[0052] Figure 2 shows a schematic diagram of an electrical device provided in some embodiments of this disclosure.

[0053] The accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0054] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the secondary battery cell, battery device, and power-consuming device of this disclosure. 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 disclosure and are not intended to limit the subject matter of the claims.

[0055] The "range" disclosed in this disclosure is defined by a lower limit and an upper limit, whereby a given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the 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 expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​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 disclosure, 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.

[0056] Unless otherwise specified, all embodiments and optional embodiments of this disclosure 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 disclosure.

[0057] Unless otherwise specified, all technical features and optional technical features of this disclosure can be combined to form new technical solutions, and such technical solutions should be considered as included in the disclosure of this disclosure.

[0058] Unless otherwise specified, all steps in this disclosure 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.

[0059] Unless otherwise specified, in this disclosure, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0060] In this disclosure, the terms "multiple" or "a variety" refer to two or more kinds.

[0061] In the description of the embodiments of this disclosure, 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" of the second feature 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.

[0062] Unless otherwise stated, the test temperature for all parameters mentioned in this disclosure is 25°C.

[0063] The secondary battery cells mentioned in the embodiments of this disclosure can independently perform charge and discharge functions, and can continue to be used by recharging after discharge to activate the active materials. The secondary battery cells can be cylindrical, cuboid, or other shapes, etc., and the embodiments of this disclosure are not limited to this. Figure 1 shows a cuboid secondary battery cell 5 as an example.

[0064] The secondary battery cells provided in the embodiments of this disclosure may include, but are not limited to, lithium battery cells and sodium battery cells, such as lithium-ion battery cells, sodium-ion battery cells, lithium metal battery cells, sodium metal battery cells, etc.

[0065] The battery apparatus mentioned in the embodiments of this disclosure may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple secondary battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0066] In some embodiments, a battery cell assembly is typically formed by arranging multiple secondary battery cells.

[0067] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple secondary battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple secondary battery cells together with cable ties.

[0068] 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.

[0069] As an example, the battery cell assembly can be a battery module, and the battery cell assembly can be housed in the housing by fixing the battery module in the housing.

[0070] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple secondary battery cells to the housing.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] The technical solutions described in this disclosure are applicable to various electrical devices that use secondary 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. Secondary battery cells and battery devices are used to store or provide electrical energy.

[0075] Figure 2 is a schematic diagram of an example electrical device. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0076] In the context of this disclosure, the "silicone-containing organic crosslinked resin particles" primarily serve to improve heat resistance in the heat-resistant layer of the separator and have virtually no adhesive properties. The "polymer binder particles" serve to improve the adhesion between the separator and the electrode in the adhesive layer of the separator and have essentially no high-temperature resistance.

[0077] The melting point of silicon-containing organic crosslinked resin particles can be tested as follows: Take an appropriate amount of sample (e.g., 5mg-15mg) and place it in the crucible of a differential scanning calorimeter (DSC), level it, and cover the crucible. Parameter settings: nitrogen atmosphere, purge gas 60mL / min, protective gas 20mL / min; program settings: heat from 25℃ to 200℃ at a heating rate of 10℃ / min, hold for 5min to eliminate thermal history, then cool from 200℃ to -40℃ at a cooling rate of 10℃ / min, and then heat to 300℃ at a heating rate of 10℃ / min. The DSC curve is used to determine whether the silicon-containing organic crosslinked resin particles have a melting point below 300℃. Silicon-containing organic crosslinked resin particles having no melting point means that the DSC curve of the silicon-containing organic crosslinked resin particles has no melting peak.

[0078] The swelling degree of silicon-containing organic crosslinked resin particles can be tested as follows: Take an appropriate amount of sample (e.g., about 1g), denoted as m1, and place it in a semi-permeable membrane sample bag. Seal the bag; the sample bag should be permeable to the solvent but not to the sample. Immerse the sample bag in an appropriate amount of solvent (e.g., about 50g) at 60°C for 7 days (7*24h). After that, remove the sample bag, remove the sample from the bag, wipe off excess solvent, and weigh the sample again (m2). Swelling degree = (m2-m1) / m1×100%. The solvent is a mixed solvent obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7.

[0079] The dissolution rate of silicon-containing organic crosslinked resin particles can be tested as follows: Take an appropriate amount of sample (e.g., about 1g), and record its mass as m1. Place it in a semi-permeable membrane sample bag, seal it, and record the total mass of the sample bag as m2. The sample bag is permeable to the solvent but not to the sample. Immerse the sample bag in an appropriate amount of solvent (e.g., about 50g) at 60℃ for 7 days (7*24h). After that, remove the sample bag, drain it, dry it, and weigh the total mass of the sample bag again as m3. Dissolution rate = (m2-m3) / m1×100%. The solvent is a mixed solvent obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7.

[0080] The oxidation peak potential of the cyclic voltammetry curve of silicon-containing organic crosslinked resin particles can be tested as follows: Silicon-containing organic crosslinked resin particles, binder polyacrylate, and conductive agent conductive carbon black are dissolved in water at a solid content mass ratio of 64:7:29 to prepare a slurry. The slurry is coated onto aluminum foil as the positive electrode, and lithium foil is used as the negative electrode to assemble a coin cell. Cyclic voltammetry (CV) is performed on the coin cell at a scan rate of 0.10 mV / s, a voltage range of 2.50 V–5.00 V, and 3 cycles. The voltage corresponding to the peak point of the first cyclic voltammetry curve is taken as the oxidation peak potential. The electrolyte used in the test is LiPF6 with a concentration of 1 mol / L. The solvent of the electrolyte is obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 3:7.

[0081] Glass transition temperature T of silicon-containing organic crosslinked resin particles g The test can be performed as follows: Take an appropriate amount of sample (e.g., 5mg-15mg) and place it in the crucible of the differential scanning calorimeter (DSC), level it, and cover the crucible. Parameter settings: nitrogen atmosphere, purge gas 60mL / min, protective gas 20mL / min; program settings: heat from 25℃ to 200℃ at a heating rate of 10℃ / min, hold for 5min to eliminate thermal history, then cool from 200℃ to -40℃ at a cooling rate of 10℃ / min, and then heat to 300℃ at a heating rate of 10℃ / min. The glass transition temperature T of the silicon-containing organic crosslinked resin particles is obtained through the DSC curve. g Or determine whether the silicon-containing organic cross-linked resin particles have a glass transition temperature T. g Glass transition temperature T g This refers to the glass transition temperature from the glassy state to the elastic state, which exhibits a step-like change on the DSC curve. Silicon-containing organic crosslinked resin particles have no glass transition temperature T0. g This means that the DSC curve of silicon-containing organic crosslinked resin particles does not show a step-like change in the range below 300℃.

[0082] Dv10, Dv50, and Dv90 represent the particle sizes corresponding to a cumulative volumetric distribution percentage of 10%, 50%, and 90%, respectively. These values ​​can be determined using a laser particle size analyzer, referring to GB / T 19077-2016. During testing, add 1g of the sample to a clean small beaker and 20ml of deionized water. Sonicate at 53kHz / 120W for 5 minutes to ensure complete dispersion. Turn on the laser particle size analyzer, clean the optical path system, and automatically test the background. Stir the sonicated solution to ensure uniform dispersion, place it in the sample cell as required, and begin measuring the particle size. A MasterSizer 3000 laser particle size analyzer can be used as the testing instrument.

[0083] The separator is a crucial component supporting the charge-discharge electrochemical processes of a secondary battery cell. Commonly used separators are mostly made of polyolefin materials; however, these materials have low glass transition temperatures and exhibit significant thermal shrinkage upon heating. To improve the heat resistance of the separator, inorganic ceramic materials such as boehmite or alumina are commonly used as heat-resistant fillers and binders to construct the heat-resistant layer. Boehmite and alumina have high densities; for the same packing volume, their mass is greater than other materials, thus affecting the energy density of the secondary battery cell.

[0084] Understandably, during electrolyte injection, the electrolyte is first injected into the bottom of the secondary battery cell, then rises from the bottom to the top and, through capillary action, wets the positive electrode, negative electrode, and separator. The larger the secondary battery cell, the less likely the electrolyte is to remain at the top due to limited capillary action. This can lead to metal deposition issues at the edges and tabs of the cell, affecting its capacity, reliability, and cycle life.

[0085] This disclosure provides a secondary battery cell, a battery device and an electrical device including the secondary battery cell, which can have high energy density, high reliability and good cycle performance.

[0086] The secondary battery cell provided in this embodiment includes a housing, an electrode assembly, and an end cap. The housing has an opening at at least one end along a first direction, the electrode assembly is disposed inside the housing, and the end cap closes the opening.

[0087] The dimensions of a single secondary battery cell in the first direction are 220mm-500mm.

[0088] The electrode assembly includes a positive electrode, a negative electrode, and a separator. The separator is disposed between the positive electrode and the negative electrode. The separator includes a porous base film and a heat-resistant layer located on one or both sides of the porous base film. The heat-resistant layer includes silicon-containing organic cross-linked resin particles.

[0089] When the separator is heated, the porous base membrane shrinks, causing the silicon-containing organic cross-linked resin particles in the heat-resistant layer to rapidly contact and compress, thereby applying a force to the porous base membrane opposite to the direction of thermal shrinkage. The separator disclosed herein has a heat-resistant layer in which the silicon-containing organic cross-linked resin particles act as a skeletal support, thus resisting the thermal shrinkage of the porous base membrane and improving the overall heat resistance of the separator. It is understood that the separator has good heat resistance and maintains good deformation resistance even at high temperatures. Therefore, when used in secondary battery cells, it can reduce the probability of short circuits between the positive and negative electrodes, improving the reliability of the secondary battery cells.

[0090] The silicon-containing organic crosslinked resin particles disclosed herein have good electrolyte affinity, and can quickly bond with the electrolyte during injection, thus rapidly wetting the separator and binding the electrolyte. This gives the separator good electrolyte wettability and liquid retention, and reduces the risk of metal deposition at the edges and tabs of the secondary battery cells, thereby giving the secondary battery cells good cycle performance.

[0091] Compared with inorganic ceramic materials such as boehmite and alumina, the heat-resistant layer disclosed herein uses low-density silicon-containing organic cross-linked resin particles, which enables secondary battery cells to have high-quality energy density.

[0092] Therefore, the secondary battery cell disclosed herein possesses high energy density, high reliability, and good cycle performance.

[0093] In some embodiments, the surface of the silicone-containing organic crosslinked resin particles has hydroxyl groups.

[0094] The hydroxyl group has good electrolyte affinity, and can quickly bond with the electrolyte during injection, thus rapidly wetting the separator. It can also bind the electrolyte, thereby giving the separator good electrolyte wettability and liquid retention. It can also reduce the risk of metal deposition at the edge and tab positions of the secondary battery cell, thus enabling the secondary battery cell to have good cycle performance.

[0095] In some embodiments, the hydroxyl content in the silicone-containing organic crosslinked resin particles can be 500 μg / g to 700 μg / g, for example, it can be 500 μg / g, 510 μg / g, 520 μg / g, 530 μg / g, 540 μg / g, 550 μg / g, 560 μg / g, 570 μg / g, 580 μg / g, 590 μg / g, 600 μg / g, 610 μg / g, 620 μg / g, 630 μg / g, 640 μg / g, 650 μg / g, 660 μg / g, 670 μg / g, 680 μg / g, 690 μg / g, 700 μg / g, or any range of the above values.

[0096] The content of hydroxyl groups within the above range is beneficial to improving the electrolyte wettability and liquid retention of the separator, and also helps to reduce electrolyte side reactions, thereby further improving the cycle performance of the secondary battery cell.

[0097] The content of hydroxyl groups can be obtained by titration. The principle of titration is based on the fact that silanol groups are Lewis acids and can undergo ion exchange reactions.

[0098] The specific testing steps are as follows:

[0099] Pretreatment: Place the sample to be tested in a 100℃ oven and dry for 12 hours, then place it in a desiccator to cool for later use.

[0100] Sample titration: Add the analyte to water and titrate with 0.1 mol / L NaOH standard solution until the pH reaches 4.0 ± 0.1. Continue titrating until the pH reaches 9.0 ± 0.1. Calculate the volume V of NaOH standard solution consumed to change the pH of the test solution from 4.0 to 9.0. pH4-9 .

[0101] Blank titration: Without adding the analyte, take an equal volume of water and titrate with 0.1 mol / L NaOH standard solution until the pH reaches 4.0 ± 0.1. Continue titrating until the pH reaches 9.0 ± 0.1. Calculate the volume V of NaOH standard solution consumed to change the pH of the blank solution from 4.0 to 9.0. B .

[0102] The content of hydroxyl groups is calculated using the following formula: α OH =1000*17.007*C NaOH *(V pH4-9 -V B ) / m.

[0103] α OH The content of hydroxyl groups is expressed in μg / g.

[0104] C NaOH This represents the actual concentration of the NaOH standard solution, accurate to four decimal places, in mol / L.

[0105] V B This represents the volume of NaOH standard solution consumed to adjust the pH of the blank solution from 4.0 to 9.0, in mL.

[0106] V pH4-9 This represents the volume of NaOH standard solution consumed to change the pH of the test solution from 4.0 to 9.0, expressed in mL.

[0107] m is the mass of the object to be measured, accurate to four decimal places, in grams.

[0108] 17.007 is the molar mass of the hydroxyl group.

[0109] The electrode assembly can be a wound structure or a stacked structure, and this disclosure does not limit this. The number of electrode assemblies contained in a single secondary battery cell can be one or more, and can be adjusted according to requirements.

[0110] The electrode assembly has tabs that allow current to be drawn out of the electrode assembly. The tabs include a positive tab and a negative tab.

[0111] The housing has an opening at at least one end along the first direction. In some embodiments, the housing may be a rigid shell, such as a hard plastic shell, an aluminum shell, a steel shell, or a composite metal shell (such as a copper-aluminum composite shell).

[0112] In some embodiments, the housing may include a base plate and side plates connected to the base plate, the base plate and side plates enclosing a receiving cavity in which the electrode assembly is disposed. In other embodiments, the housing may be a hollow structure with openings on opposite sides, and two end caps, one end cap corresponding to one opening of the housing and forming a sealed connection to form a receiving cavity for accommodating the electrode assembly.

[0113] In some embodiments, the secondary battery cell has electrode terminals for electrical connection to tabs. For example, the electrode terminals include a positive electrode terminal and a negative electrode terminal, with the positive electrode terminal electrically connected to the positive tab and the negative electrode terminal electrically connected to the negative tab. The electrode terminals can be directly connected to the tabs or indirectly connected to them via current collectors. The electrode terminals can be disposed on an end cap or on the housing.

[0114] The dimensions of a single secondary battery cell in the first direction can be obtained by measuring with a laser thickness gauge. During testing, 3-5 points can be randomly selected, and the average value is taken. It should be understood that the dimensions of the single secondary battery cell in the first direction do not include the dimensions of the electrode terminals set on the end cap.

[0115] In some embodiments, the packing density of the heat-resistant layer can be 0.4 g / cm³. 3 -1.5g / cm 3 For example, it can be 0.4 g / cm³. 3 0.5g / cm 3 0.6g / cm 3 0.7g / cm 3 0.8g / cm 3 0.9g / cm 3 1g / cm 3 1.1g / cm 3 1.2g / cm 3 1.3g / cm 3 1.4g / cm3 1.5g / cm 3 or a range consisting of any of the above values.

[0116] Bulk density of heat-resistant layer (g / cm³) 3 ) refers to the areal density (g / cm³) of the heat-resistant layer. 2 The ratio of thickness (cm) to total thickness (cm).

[0117] A low bulk density of the heat-resistant layer results in poor electrolyte retention in the separator; a high bulk density of the heat-resistant layer leads to poor electrolyte wettability and a slow wetting rate in the separator. The bulk density of the heat-resistant layer in this disclosure is 0.4 g / cm³. 3 -1.5g / cm 3 Within this range, the resulting separator can have good electrolyte wettability and liquid retention, thereby improving the production efficiency of secondary battery cells and giving them good cycle performance.

[0118] Optionally, the bulk density of the heat-resistant layer can be 1 g / cm³. 3 -1.5g / cm 3 1.1g / cm 3 -1.5g / cm 3 1.2g / cm 3 -1.5g / cm 3 .

[0119] The bulk density of the heat-resistant layer can be obtained by adjusting parameters such as the true density of the silicon-containing organic cross-linked resin particles, the morphology of the silicon-containing organic cross-linked resin particles, the size of the silicon-containing organic cross-linked resin particles, and the particle size distribution of the silicon-containing organic cross-linked resin particles.

[0120] The silicon-containing organic crosslinked resin particles disclosed herein are commercially available or can be prepared according to the preparation method provided herein.

[0121] In some embodiments, the true density of the silicon-containing organic crosslinked resin particles can be 1.0 g / cm³. 3 -1.5g / cm 3 .

[0122] Currently, the true density of inorganic particles such as boehmite and alumina is typically 2.5 g / cm³. 3 -3.5g / cm 3 The silicon-containing organic crosslinked resin particles disclosed herein have a low true density, thereby enabling secondary battery cells using the separator of this disclosure to have a higher mass energy density.

[0123] In some embodiments, the morphology of the silicon-containing organic crosslinked resin particles may include one or more of the following: spherical, near-spherical, ellipsoidal, and near-ellipsoidal.

[0124] The morphology of silicon-containing organic crosslinked resin particles can be tested using a scanning electron microscope, for example, according to JY / T 010-1996. The testing instrument can be a ZEISS Sigma 300 scanning electron microscope from Germany.

[0125] Spherical, near-spherical, ellipsoidal, and near-ellipsoidal silicon-containing organic cross-linked resin particles have high space utilization and can contribute a large amount of space for storing electrolyte. Therefore, by making the morphology of silicon-containing organic cross-linked resin particles include one or more of spherical, near-spherical, ellipsoidal, and near-ellipsoidal shapes, the electrolyte can be stored in the pores of the separator to form ion transport channels while promoting rapid wetting of the separator. This can improve the cycle performance and rate performance of the secondary battery cell.

[0126] In some embodiments, the volume distribution particle size Dv50 of the silicon-containing organic crosslinked resin particles is less than 1 μm, and can be selected from 60 nm to 800 nm, for example, it can be 60 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, or any range of the above values.

[0127] Optionally, the volume distribution particle size Dv50 of the silicon-containing organic crosslinked resin particles can be 60nm-700nm, 80nm-700nm, 100nm-700nm, 60nm-600nm, 80nm-600nm, 100nm-600nm, 60nm-500nm, 80nm-500nm, 100nm-500nm, 60nm-400nm, 80nm-400nm, 100nm-400nm, or 150nm-400nm.

[0128] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the silicon-containing organic crosslinked resin particles can be 0.2-1.1, for example, it can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, or any range of the above values.

[0129] In some embodiments, the silicone-containing organic crosslinked resin particles have no melting point.

[0130] The absence of melting point in silicon-containing organic crosslinked resin particles indicates good heat resistance and thermal stability, which can better resist the thermal shrinkage of porous base films, improve the heat resistance of separators, and enhance the reliability of secondary battery cells.

[0131] In some embodiments, the silicone-containing organic crosslinked resin particles have no glass transition temperature.

[0132] The absence of a glass transition temperature in silicon-containing organic crosslinked resin particles indicates good heat resistance and thermal stability. This allows them to better resist the thermal shrinkage of porous base films, improve the heat resistance of the separator, and enhance the reliability of secondary battery cells.

[0133] In some embodiments, the swelling degree of the silicon-containing organic crosslinked resin particles after being soaked in a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7 at 60°C for 7 days is less than or equal to 3%.

[0134] Silicon-containing organic cross-linked resin particles have low swelling in organic solvents and high structural stability during long-term use of secondary battery cells, thereby improving the problem of decreased air permeability of the separator during use.

[0135] In some embodiments, the dissolution rate of the silicon-containing organic crosslinked resin particles after being soaked in a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7 at 60°C for 7 days is less than or equal to 3%.

[0136] Silicon-containing organic crosslinked resin particles have a low dissolution rate in organic solvents, high structural stability during long-term use of secondary battery cells, and high chemical stability in electrolytes, which can enable secondary battery cells to have longer cycle stability.

[0137] In some embodiments, the cyclic voltammetry curves of the silicon-containing organic crosslinked resin particles during the first cycle do not exhibit oxidation peaks in the voltage range of 2.5V to 4.4V.

[0138] The cyclic voltammetry curve of the silicon-containing organic crosslinked resin particles in the first cycle does not have an oxidation peak in the voltage window range of ≥2.5V and <4.4V, indicating that the silicon-containing organic crosslinked resin particles are stable in the voltage window range of ≥2.5V and <4.4V and will not undergo electrochemical redox reactions. This allows the secondary battery cell to have a high voltage plateau and high quality energy density.

[0139] In some embodiments, the silicon-containing organic crosslinked resin particles include one or more of polysilsesquioxane, silicon-containing organic crosslinked resin particles containing carbon-carbon bonds and silicon-oxygen structures.

[0140] [Silicone-containing organic cross-linked resin particles containing carbon-carbon bonds and silicon-oxygen structures]

[0141] In some embodiments, the silicon-containing organic crosslinked resin particles contain carbon-carbon bonds and silicon-oxygen structures.

[0142] Optionally, the silicon-containing organic crosslinked resin particles have a network structure with carbon-carbon bonds as the main chain and silicon-oxygen structures in the side chains.

[0143] Optionally, the silicon-containing organic crosslinked resin particles have a network structure formed with carbon-carbon bonds as the main chain, and the side chains contain silicon-oxygen structures and benzene ring structures.

[0144] The rigidity of the benzene ring structure gives silicon-containing organic crosslinked resin particles good heat resistance. By using silicon-containing organic crosslinked resin particles with benzene ring structures in separators, it is possible to better generate forces to resist the shrinkage of porous base membranes, thereby improving the overall thermal shrinkage of the separator, enhancing its heat resistance, and improving the reliability of secondary battery cells.

[0145] In some embodiments, the silicon-containing organic crosslinked resin particles containing carbon-carbon bonds and silicon-oxygen structures include crosslinked structural units. The crosslinked structural units of the silicon-containing organic crosslinked resin particles refer to silicon-free structural units used to connect the silicon-containing structural units. Optionally, the crosslinked structural units may include divinylbenzene structural units, diethylene glycol divinyl ether structural units, triethylene glycol divinyl ether structural units, diallyl maleate structural units, ethylene glycol dimethacrylate structural units, 1,4-butanediol diacrylate structural units, 1,6-hexanediol diacrylate structural units, 1,8-octanediol diacrylate structural units, trimethylolpropane triacrylate structural units, pentaerythritol trimethacrylate structural units, tetraethylene glycol dimethacrylate structural units, and di... The structural unit comprises one or more of the following: tripropylene glycol diacrylate, 2,2,4-trimethyladipyl di[2-ethylaziridinium], 1,1-azeloyl di[2-methylaziridinium], 1,1-(1,3-phenylene dicarbonyl) di[2-methylaziridinium], trimethylolpropane tris(2-methyl-1-aziridinium propionate), trimethylolpropane tris[3-(2-methylaziridinium)propionate], and pentaerythritol tris(3-aziridinium)propionate.

[0146] Optionally, the crosslinking structural unit may include a divinylbenzene structural unit.

[0147] Optionally, the crosslinking structural unit may include a divinylbenzene structural unit, as well as diethylene glycol divinyl ether structural units, triethylene glycol divinyl ether structural units, diallyl maleate structural units, ethylene glycol dimethacrylate structural units, 1,4-butanediol diacrylate structural units, 1,6-hexanediol diacrylate structural units, 1,8-octanediol diacrylate structural units, trimethylolpropane triacrylate structural units, pentaerythritol trimethacrylate structural units, tetraethylene glycol dimethacrylate structural units, and di... The structural unit comprises one or more of the following: tripropylene glycol diacrylate, 2,2,4-trimethyladipyl di[2-ethylaziridinium], 1,1-azeloyl di[2-methylaziridinium], 1,1-(1,3-phenylene dicarbonyl) di[2-methylaziridinium], trimethylolpropane tris(2-methyl-1-aziridinium propionate), trimethylolpropane tris[3-(2-methylaziridinium)propionate], and pentaerythritol tris(3-aziridinium)propionate.

[0148] Silicon-containing organic crosslinked resin particles containing carbon-carbon bonds and silicon-oxygen structures are poorly soluble in both water and organic solvents, such as tetrahydrofuran (THF), dichloromethane (DCM), dimethylformamide (DMF), trichlorobenzene (TCB), and chloroform, at 25°C. They are also insoluble in the mobile phase used in gel permeation chromatography and cannot be used to determine molecular weight by gel permeation chromatography.

[0149] In some embodiments, silicon-containing organic crosslinked resin particles containing carbon-carbon bonds and silicon-oxygen structures have no melting point.

[0150] In some embodiments, silicon-containing organic crosslinked resin particles containing carbon-carbon bonds and silicon-oxygen structures have no glass transition temperature.

[0151] In some embodiments, the swelling degree of silicon-containing organic crosslinked resin particles containing carbon-carbon bonds and silicon-oxygen structures after being soaked in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 at 60°C for 7 days is less than or equal to 3%.

[0152] In some embodiments, the dissolution rate of silicon-containing organic crosslinked resin particles containing carbon-carbon bonds and silicon-oxygen structures after being soaked at 60°C for 7 days in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 is less than or equal to 3%.

[0153] In some embodiments, the cyclic voltammetry curves of silicon-containing organic crosslinked resin particles containing carbon-carbon bonds and silicon-oxygen structures do not exhibit oxidation peaks in the voltage range of 2.5V to 4.4V during the first cycle.

[0154] Silicon-containing organic crosslinked resin particles containing carbon-carbon bonds and silicon-oxygen structures are commercially available or can be prepared according to the preparation method provided in this disclosure.

[0155] A method for preparing silicon-containing organic crosslinked resin particles with carbon-carbon bonds and silicon-oxygen structures includes the following steps: providing a pre-emulsion comprising monomers, crosslinking agents, emulsifiers, initiators, and water; subjecting the pre-emulsion to emulsion polymerization under heating, inert gas protection, and stirring conditions to obtain the product. The monomers include silane coupling agents containing alkenyl and / or acryloyloxy groups. The mass fraction of the crosslinking agent is 3%-18% based on the total mass of monomers and crosslinking agents (100%).

[0156] The monomers include silane coupling agents containing alkenyl and / or acryloyloxy groups, thus initiating free radical generation and cross-linking reactions between monomers, and the monomers also undergo cross-linking reactions with the cross-linking agents. Therefore, using the monomers and cross-linking agents of this disclosure as raw materials, silicon-containing organic cross-linked resin particles with a three-dimensional network molecular structure can be formed, which are not easily softened or deformed at high temperatures and have high heat resistance.

[0157] When the mass fraction of the crosslinking agent is within the above range, silicon-containing organic crosslinked resin particles with good heat resistance can be obtained.

[0158] The mass fraction of the crosslinking agent is 3%-18%, for example, it can be 3%, 4%, 5%, 6%, 7%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 16%, 17%, 18%, or any combination of the above values.

[0159] Optionally, based on the total mass of monomers and crosslinking agents as 100%, the mass fraction of the crosslinking agent can be 4%-18%, 6%-18%, 8%-18%, 4%-16%, 6%-16%, 8%-16%, 4%-15%, 6%-15%, or 8%-15%.

[0160] When the mass fraction of the crosslinking agent is within the above range, silicon-containing organic crosslinked resin particles with better heat resistance can be obtained.

[0161] In some embodiments, the emulsion polymerization reaction may include the following steps: adding a pre-emulsion dropwise into a reactor containing water under a first temperature, an inert gas protection and stirring conditions, reacting for a first time, then heating to a second temperature to mature the reaction for a second time, to obtain the product.

[0162] By adjusting the types and amounts of each component in the preemulsion, as well as parameters such as reaction temperature and reaction time, silicon-containing organic crosslinked resin particles with different particle sizes and / or morphologies (such as spherical, near-spherical, ellipsoidal, and near-ellipsoidal) can be obtained.

[0163] In some embodiments, the first temperature can be 55°C-70°C.

[0164] In some embodiments, the first time can be 3h-6h.

[0165] In some embodiments, the second temperature can be 72℃-92℃, for example, it can be 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃, 89℃, 90℃, 91℃, 92℃, or any range of the above values.

[0166] In some embodiments, the second time can be 1h-5h, for example, it can be 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h, 4h, 4.2h, 4.4h, 4.6h, 4.8h, 5h, or any range of the above values.

[0167] The emulsion polymerization reaction is carried out under the protection of an inert gas. In some embodiments, the inert gas may include one or more of nitrogen, argon, and helium.

[0168] In some embodiments, the monomer may include a vinylsilane coupling agent and / or an acryloyloxysilane coupling agent.

[0169] Optionally, the monomer may include γ-methacryloxypropyltris(trimethylsiloxane), (3-acryloxypropyl)tris(trimethylsiloxy)silane, 3-methacryloxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, acryloxypropyltriethoxysilane, γ-methacryloxypropyltriisopropoxysilane, 3-(acryloxy)propyltrimethoxysilane, 3-methacryloxypropyltris(methoxyethoxy)silane, vinyltrimethoxysilane, 7-octenyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, tri-tert-butoxyvinylsilane, vinyltri... One or more of the following: (β-methoxyethoxy)silane, ethylenetri[(1-methylvinyl)oxy]silane, vinyltritert-butylperoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, 3-acryloyloxypropylmethyldimethoxysilane, methacryloyloxypropyldimethylmethoxysilane, (3-acryloyloxy)dimethylmethoxysilane, 3-methacryloyloxypropyldimethylethoxysilane, diethylmethylvinylsilane, vinyldimethylethoxysilane, methylvinyldiethoxysilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, methylvinyldimethoxysilane, and 3-(methacryloyloxy)propylmethyldiethoxysilane.

[0170] The crosslinking agent and monomers polymerize to form crosslinked structural units of silicon-containing organic crosslinked resin particles.

[0171] In some embodiments, the crosslinking agent may be a multifunctional crosslinking agent. Optionally, the crosslinking agent may include one or more of the following: divinylbenzene, diethylene glycol divinyl ether, triethylene glycol divinyl ether, diallyl maleate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,8-octanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol trimethacrylate, tetraethylene glycol dimethacrylate, tripropylene glycol diacrylate, 2,2,4-trimethyladipyl di[2-ethylaziridinium], 1,1-nonaiyl di[2-methylaziridinium], 1,1-(1,3-phenylene dicarbonyl) di[2-methylaziridinium], trimethylolpropane tris(2-methyl-1-aziridinium propionate), trimethylolpropane tris[3-(2-methylaziridinium)propionate], and pentaerythritol tris(3-aziridinium)propionate.

[0172] Optionally, the crosslinking agent may include divinylbenzene.

[0173] Optionally, the crosslinking agent may include divinylbenzene and one or more of diethylene glycol divinyl ether, triethylene glycol divinyl ether, diallyl maleate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,8-octanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol trimethacrylate, tetraethylene glycol dimethacrylate, tripropylene glycol diacrylate, 2,2,4-trimethyladipyl di[2-ethylaziridinium], 1,1-nonaiyl di[2-methylaziridinium], 1,1-(1,3-phenylene dicarbonyl) di[2-methylaziridinium], trimethylolpropane tris(2-methyl-1-aziridinium propionate), trimethylolpropane tris[3-(2-methylaziridinium)propionate], and pentaerythritol tris(3-aziridinium)propionate.

[0174] In some embodiments, the emulsifier may include, but is not limited to, one or more of alkyl sulfates, alkyl sulfonates, Tween emulsifiers, fatty alcohol polyoxyethylene ethers, fatty alcohol polyoxypropylene ethers, cetearyl alcohol polyethers, and oleyl alcohol polyethers. Optionally, the emulsifier includes one or more of sodium lauryl sulfate, sodium lauryl sulfonate, Tween 20, Tween 40, lauryl ether-7, lauryl ether-9, lauryl ether-10, and oleyl alcohol polyether-10.

[0175] In some embodiments, the initiator may be one or more of sodium persulfate, potassium persulfate, ammonium persulfate, sodium sulfite, sodium bisulfite, azobisisobutyronitrile, azobisisobutyramidine hydrochloride, azobisisobutyramidine imidazoline hydrochloride, and azobisisopropylimidazoline.

[0176] In some embodiments, the mass fraction of the initiator, based on the total mass of monomers and crosslinking agents (100%), can be 0.15%-2.5%, for example, 0.15%, 0.2%, 0.3%, 0.4%, 0.5%, 0.7%, 0.9%, 1.1%, 1.3%, 1.5%, 1.7%, 1.9%, 2.1%, 2.3%, 2.5%, or any range of the above values. Optionally, the mass fraction of the initiator can be 0.3%-2.1%, 0.3%-1.9%, 0.3%-1.7%, 0.3%-1.5%, or 0.3%-1.3%.

[0177] In some embodiments, the preemulsion may further include a pH adjuster. Optionally, the pH adjuster may include, but is not limited to, one or more of sodium bicarbonate, sodium hydroxide, ammonia, etc.

[0178] The product obtained from the emulsion polymerization reaction can be used directly to prepare the heat-resistant layer slurry of the separator without drying, or the product obtained from the emulsion polymerization reaction can be used to prepare the heat-resistant layer slurry of the separator after drying.

[0179] In some embodiments, the method for preparing silicon-containing organic crosslinked resin particles containing carbon-carbon bonds and silicon-oxygen structures may further include the steps of: drying the product obtained from the emulsion polymerization reaction, followed by a crushing process and a wet grinding process to obtain the final product. The product may include aggregates of primary particles. The product obtained from wet grinding can be used directly to prepare the heat-resistant layer slurry of the separator without drying, or the product obtained from wet grinding can be dried before being used to prepare the heat-resistant layer slurry of the separator.

[0180] In other embodiments, the preparation method of silicon-containing organic crosslinked resin particles containing carbon-carbon bonds and silicon-oxygen structures may further include the steps of: drying the product obtained from the emulsion polymerization reaction, then baking it under an inert gas atmosphere, and then subjecting it to a crushing process and a wet grinding process to obtain the product. The product may include aggregates of primary particles. The product obtained from wet grinding can be used directly to prepare the heat-resistant layer slurry of the separator without drying, or the product obtained from wet grinding can be used to prepare the heat-resistant layer slurry of the separator after drying.

[0181] In some embodiments, the drying methods for the products obtained from emulsion polymerization may include, but are not limited to, vacuum drying, spray drying, forced air drying, microwave drying, or fluidized bed drying.

[0182] In some embodiments, the drying temperature of the product obtained from the emulsion polymerization reaction can be 80℃-150℃, for example, it can be 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, or any combination of the above values.

[0183] In some embodiments, the drying time of the product obtained from the emulsion polymerization reaction can be 2h-12h, for example, it can be 2h, 2.4h, 2.8h, 3.2h, 3.6h, 4h, 4.4h, 4.8h, 5.2h, 5.6h, 6h, 6.4h, 6.8h, 7.2h, 7.6h, 8h, 8.4h, 8.8h, 9.2h, 9.6h, 10h, 10.4h, 10.8h, 11.2h, 11.6h, 12h, or any range of the above values.

[0184] Baking is carried out in an inert gas atmosphere. In some embodiments, the inert gas may include one or more of nitrogen, argon, and helium.

[0185] In some embodiments, the baking temperature can be 160℃-250℃, for example, it can be 160℃, 165℃, 170℃, 175℃, 180℃, 185℃, 190℃, 195℃, 200℃, 205℃, 210℃, 215℃, 220℃, 225℃, 230℃, 235℃, 240℃, 245℃, 250℃, or any range of the above values.

[0186] In some embodiments, the baking time can be 1 hour to 8 hours, for example, 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, 4 hours, 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours, 5 hours, 5.2 hours, 5.4 hours, 5.6 hours, 5.8 hours, 6 hours, 6.2 hours, 6.4 hours, 6.6 hours, 6.8 hours, 7 hours, 7.2 hours, 7.4 hours, 7.6 hours, 7.8 hours, 8 hours, or any range of the above values. Optionally, the baking time can be 2 hours to 8 hours, 2.4 hours to 8 hours, or 3 hours to 8 hours.

[0187] In some embodiments, the crushing process can employ air jet mills, vibratory mills, mechanical mills, ultrasonic mills, ball mills, etc.

[0188] In some embodiments, the wet milling process may include the following steps: mixing crushed material with a solvent, grinding media and optional dispersant to obtain a mixed slurry, and then milling the mixed slurry to obtain a product.

[0189] Optionally, the solvent for wet milling may include one or more of water, methanol, and ethanol. More preferably, the solvent may include water.

[0190] Optionally, the dispersant used in wet milling may include one or more of polyacrylic acid dispersants, carboxymethyl cellulose dispersants, polyethylene glycol, polyvinyl alcohol, and polyvinylpyrrolidone. Optionally, the polyacrylic acid dispersant may include one or more of polypropionic acid, sodium polyacrylate, potassium polyacrylate, and ammonium acrylate. Optionally, the carboxymethyl cellulose dispersant may include one or more of carboxymethyl cellulose, sodium carboxymethyl cellulose, and potassium carboxymethyl cellulose.

[0191] Optionally, the polishing media may include one or more of zirconia balls, alumina balls, and silicon nitride balls.

[0192] Optionally, the average particle size of the grinding media can be 0.1 mm to 2 mm.

[0193] Optionally, the grinding speed can be 500rpm-3000rpm.

[0194] [Polysilsesquioxane]

[0195] In other embodiments, the silicon-containing organic crosslinked resin particles comprise polysilsesquioxane.

[0196] In some embodiments, the weight-average molecular weight of the polysilsesquioxane can be from 10,000 to 100,000, for example, it can be 10,000, 15,000, 20,000, 25,000, 30,000, 35,000, 40,000, 45,000, 50,000, 55,000, 60,000, 65,000, 70,000, 75,000, 80,000, 85,000, 90,000, 95,000, 100,000, or any combination of the above values. Optionally, the weight-average molecular weight of the polysilsesquioxane can be 10,000-95,000, 15,000-95,000, 20,000-90,000, 30,000-80,000, 40,000-70,000, or 50,000-60,000.

[0197] When the weight-average molecular weight of polysilsesquioxane is within the above range, polysilsesquioxane with uniform particle size distribution can be obtained, which improves the heat resistance of the separator. In addition, it can reduce the probability of polysilsesquioxane clogging the micropores on the separator, thereby improving the cycle performance of the secondary battery cell.

[0198] The weight-average molecular weight of polysilsesquioxanes can be determined using gel permeation chromatography (GPC) according to GB / T21863-2008. Specifically, it can be performed as follows: using an ultra-high performance polymer chromatograph (UHPLC): ACQUITY APC; detector: ACQUITY differential refractive index detector.

[0199] Parameter settings: Injection volume: 0 μL to 50 μL (depending on sample concentration); Pump flow rate: 0.2 mL / min; Mobile phase: 30 mol / L LiBr in NMP (N-methylpyrrolidone) solution; Sealing and cleaning solution: isopropanol; Pre-column: PLgel 10 μm Mini MIX-B Guard (size: 50 mm × 4.6 mm × 2); Analytical phase: PLgel 10 μm Mini MIX-B (size: 250 mm × 4.6 mm); Standards: polystyrene sleeve; Run time: 30 min; Detector: ACQUITY differential refractive index (RI) detector; Column oven temperature: 90 °C; Detector temperature: 55 °C.

[0200] Sample testing: a. Preparation of standard and test samples: Weigh 0.002g to 0.004g of standard / test sample and add 2mL of mobile phase liquid to prepare a 0.1% to 0.5% mixed standard solution and place it in the refrigerator for >8h; b. Standard solution / sample testing: Edit the sample group to be tested, select the established sample group method, and after the baseline stabilizes, click the run queue to start testing the samples.

[0201] Data processing: Based on the relationship between retention time and molecular weight, a calibration curve is established using a chemical workstation, and the sample spectrum is integrated and quantified. The chemical workstation automatically generates molecular weight and molecular weight distribution results.

[0202] In some embodiments, the structural formula of polysilsesquioxane may include:

[0203] R1 and R2 each independently include an alkyl group with 1-12 carbon atoms, an unsaturated hydrocarbon group with 2-12 carbon atoms, or a phenyl group, n = 50-1000.

[0204] The unsaturated hydrocarbon group can be alkenyl or ynyl.

[0205] Optionally, R1 and R2 each independently include alkyl groups with 2-11 carbon atoms, alkyl groups with 3-10 carbon atoms, alkyl groups with 4-9 carbon atoms, alkyl groups with 5-8 carbon atoms, alkyl groups with 6-7 carbon atoms, etc.

[0206] Optionally, R1 and R2 each independently include an alkenyl or ynyl group with 2-11 carbon atoms, an alkenyl or ynyl group with 3-10 carbon atoms, an alkenyl or ynyl group with 4-9 carbon atoms, an alkenyl or ynyl group with 5-8 carbon atoms, an alkenyl or ynyl group with 6-7 carbon atoms, etc.

[0207] Optionally, n = 50-999, n = 100-950, n = 200-900, n = 300-800, n = 400-700, n = 500-600.

[0208] Therefore, the polysilsesquioxane with the above-mentioned structure improves the heat resistance of the separator. In addition, it can reduce the probability of polysilsesquioxane clogging the micropores on the separator, thereby improving the cycle performance of the secondary battery cell.

[0209] Alternatively, the polysilsesquioxane may include at least one of the following structural formulas:

[0210] Ph represents phenyl, n = 50-1000.

[0211] Optionally, n = 50-999, n = 100-950, n = 200-900, n = 300-800, n = 400-700, n = 500-600, etc. It can be understood that the values ​​of n in the above structural formulas are independent of each other, and can be equal or unequal.

[0212] Therefore, the polysilsesquioxane with the above-mentioned structure improves the heat resistance of the separator. In addition, it can reduce the probability of polysilsesquioxane clogging the micropores on the separator, thereby improving the cycle performance of the secondary battery cell.

[0213] In some embodiments, polysilsesquioxane has no melting point.

[0214] In some embodiments, polysilsesquioxane has no glass transition temperature.

[0215] In some embodiments, the swelling degree of polysilsesquioxane after being immersed at 60°C for 7 days in a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7 is less than or equal to 3%.

[0216] In some embodiments, the dissolution rate of polysilsesquioxane in a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7, after being soaked at 60°C for 7 days, is less than or equal to 3%.

[0217] In some embodiments, the cyclic voltammetry curve of the polysilsesquioxane during the first cycle does not exhibit an oxidation peak in the voltage range of 2.5V to 4.4V.

[0218] Polysilsesquioxanes are commercially available or can be prepared according to the preparation method provided in this disclosure.

[0219] The preparation method of polysilsesquioxane includes the following steps: hydrolyzing the siloxane monomer, adding a catalyst, and polycondensing under heating conditions to obtain polysilsesquioxane.

[0220] In some embodiments, the hydrolysis temperature of the siloxane monomer can be 20°C-30°C. Within this hydrolysis temperature range, the siloxane monomer is fully hydrolyzed, and the resulting polysilsesquioxane, when used in a separator membrane, can improve the cycle performance of the secondary battery cell.

[0221] In some embodiments, the heating temperature can be 30°C-100°C. Within the above heating temperature range, polysilsesquioxane with uniform particle size distribution can be obtained, which can improve the cycle performance of secondary battery cells. Optionally, the heating temperature can be 40°C-80°C.

[0222] Specifically, the siloxane monomer first hydrolyzes to generate silanol, releasing alcohol to form a mixed solution. The alcohol increases the solubility of the siloxane monomer in the solution. Then, under the action of a catalyst, the silanol begins to condense, forming Si-O-Si bonds between silanols, further forming a network structure, at which point nucleation begins. Finally, these nuclei continuously absorb silanol from the solution and continue to grow until they become polysilsesquioxane. The nucleation and nucleus growth processes are competitive, and the reaction temperature affects both processes. When nucleation dominates, more nuclei are generated, resulting in smaller final polysilsesquioxane particle sizes; when nucleus growth dominates, the final microspheres have larger particle sizes. Increasing the temperature intensifies the reaction, generating more nuclei and consuming more silanol in the initial stages, thus limiting nucleus growth in later stages and resulting in smaller final polysilsesquioxane particle sizes. Controlling the heating temperature within the range of 30℃-100℃ can promote uniform polysilsesquioxane particle size and improve the cycle performance of the secondary battery cell.

[0223] In some embodiments, the catalyst may include one or more of ammonia, triethylamine, sodium hydroxide, magnesium hydroxide, and ammonium hydroxide. Therefore, the above catalyst can continuously and efficiently catalyze the polycondensation of hydrolyzed siloxane monomers, yielding polysilsesquioxanes with uniform particle size distribution, thereby improving the cycle performance of secondary battery cells.

[0224] In some embodiments, the siloxane monomer may include:

[0225] R3 includes any one of methyl or ethyl, and R4 includes any one of methyl, ethyl, phenyl, vinyl, allyl, and dodecyl. Therefore, the above-mentioned siloxane monomers can be hydrolyzed and polycondensed to obtain polysilsesquioxanes with uniform particle size distribution, which can improve the cycle performance of secondary battery cells.

[0226] As an example, siloxane monomers may include one or more of methyltrimethoxysilane, ethyltrimethoxysilane, phenyltrimethoxysilane, dodecyltrimethoxysilane, vinyltrimethoxysilane, allyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, phenyltriethoxysilane, dodecyltriethoxysilane, vinyltriethoxysilane, and allyltriethoxysilane.

[0227] Specifically, taking R3 as methyl and R4 as methyl as an example, the hydrolysis and condensation reaction process of siloxane monomers is as follows:

[0228] In some embodiments, the mass percentage of silicon-containing organic crosslinked resin particles in the heat-resistant layer may be greater than or equal to 80%.

[0229] Optionally, the mass percentage of silicon-containing organic crosslinked resin particles in the heat-resistant layer can be greater than or equal to 85%, greater than or equal to 88%, or greater than or equal to 90%.

[0230] In some embodiments, the heat-resistant layer comprises an adhesive, which includes one or more of hydroxyl, carboxyl, carboxylate, ester, epoxy, and amide groups. These groups have good electrolyte affinity, allowing them to quickly bond with the electrolyte during injection and effectively wet the separator.

[0231] In some embodiments, the adhesive in the heat-resistant layer may include one or more of the following: polyacrylate adhesives, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0232] In some embodiments, the adhesive may constitute 1% or more of the heat-resistant layer by mass. Optionally, the adhesive may constitute 1% to 10% of the heat-resistant layer by mass.

[0233] In some embodiments, the heat-resistant layer may further include a dispersant, such as, but not limited to, polyacrylic acid dispersants or carboxymethyl cellulose dispersants. As an example, the dispersant may include, but is not limited to, one or more of sodium carboxymethyl cellulose, sodium polyacrylate, and ammonium polyacrylate.

[0234] In some embodiments, the mass percentage of the dispersant in the heat-resistant layer can be 0%-2%, optionally 0.1%-2%. 0% indicates that the heat-resistant layer does not contain the dispersant.

[0235] In some embodiments, the separator may further include an adhesive layer disposed on at least a portion of the surface of the heat-resistant layer or the porous base membrane. The adhesive layer includes polymer binder particles, and the volume distribution particle size Dv50 of the polymer binder particles may be 6 μm-18 μm.

[0236] For example, a heat-resistant layer is disposed on a porous base membrane, and an adhesive layer is disposed on at least a portion of the surface of the heat-resistant layer on the side away from the porous base membrane; or, a heat-resistant layer is disposed on one side of the porous base membrane, and an adhesive layer is disposed on at least a portion of the surface of the other side of the porous base membrane.

[0237] In some embodiments, polymer binder particles may include aggregates of primary particles.

[0238] In some embodiments, the polymer binder particles may include one or more of fluoropolymer binder particles and non-fluoropolymer binder particles.

[0239] Optionally, the fluoropolymer binder particles may include vinylidene fluoride polymer particles, such as polyvinylidene fluoride (PVDF) particles and / or copolymer particles of vinylidene fluoride monomer and comonomer. The comonomer may include at least one of olefin monomers, fluorinated olefin monomers, chlorinated olefin monomers, acrylate monomers, acrylic monomers, and fluoroether monomers. Optionally, the comonomer may include at least one of the following: trifluoroethylene, trifluorochloroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl) ethers (e.g., perfluoro(methyl vinyl) ether, perfluoro(ethyl vinyl) ether, perfluoro(propyl vinyl) ether), perfluoro(1,3-m-dioxacyclopentene), and perfluoro(2,2-dimethyl-1,3-m-dioxacyclopentene).

[0240] Optionally, the non-fluoropolymer binder particles may include acrylate copolymers. Acrylate copolymers are a general term for polymers produced by copolymerization of acrylate monomers and other comonomers.

[0241] Acrylic copolymers have good adhesion, and using acrylic copolymers results in better adhesion between the separator and the electrode sheet after cold or hot pressing.

[0242] In some embodiments, the adhesive layer further includes an adhesive for bonding polymer adhesive particles. The adhesive may include one or more of the following: polyacrylate adhesives, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0243] In some embodiments, the adhesive layer may further include a dispersant and / or a surfactant. The dispersant may include, but is not limited to, polyacrylic acid dispersants or carboxymethyl cellulose dispersants. As an example, the dispersant may include, but is not limited to, one or more of sodium carboxymethyl cellulose, sodium polyacrylate, and ammonium polyacrylate. The surfactant may include ether-based surfactants.

[0244] In some embodiments, the thickness of the heat-resistant layer can be 0.4 μm-5 μm. The thickness of the heat-resistant layer refers to the thickness of the heat-resistant layer located on one side of the porous base film. Optionally, the thickness of the heat-resistant layer can be 0.5 μm-4 μm, 0.5 μm-3 μm, 0.5 μm-2 μm, 0.6 μm-4 μm, 0.6 μm-3 μm, 0.6 μm-2 μm, 0.8 μm-4 μm, 0.8 μm-3 μm, or 0.8 μm-2 μm.

[0245] In some embodiments, the ratio of the volume distribution particle size Dv50 of the silicon-containing organic crosslinked resin particles to the average pore size of the porous base membrane can be greater than or equal to 1.2. The volume distribution particle size Dv50 of the silicon-containing organic crosslinked resin particles and the average pore size of the porous base membrane have the same unit, for example, nm. This can reduce pore clogging problems and improve the air permeability and ion conduction properties of the separator.

[0246] In some embodiments, the average pore size of the porous base film can be 25nm-80nm, for example, it can be 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, or any range of the above values.

[0247] Optionally, the average pore size of the porous base film can be 35nm-80nm, 40nm-80nm, 45nm-80nm, 50nm-80nm, 35nm-75nm, 40nm-75nm, 45nm-75nm, or 50nm-75nm.

[0248] The average pore size of the porous membrane can be measured using a capillary porosity analyzer (bubble point method). An exemplary testing method is as follows: Take a circular sample with a diameter of 25 mm, and drop 3-5 drops of wetting solution onto it. After the sample is completely wetted, place it in a mold. Then, use an inert gas (such as nitrogen) to compress the wetting solution in the pores of the sample. The compression pressure and flow rate are inversely proportional to the pore size. The average pore size of the sample is obtained through software sampling and pressure-pore size conversion analysis. The testing instrument can be a PMI CFP 1500 pore size analyzer, with a testing pressure ranging from 100 psi to 350 psi.

[0249] In some embodiments, the porosity of the porous base membrane can be 25%-60%, for example, it can be 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any range of the above values.

[0250] Optionally, the porosity of the porous membrane can be 30%-40%.

[0251] In some embodiments, the thickness of the porous base film can be 3μm-11μm, and optionally 3μm-7μm.

[0252] In some embodiments, the porous base membrane may comprise a membrane selected from any one or at least two of the following: polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymer, polyphenylene sulfide, and polyvinyl naphthalene.

[0253] Optionally, the porous base membrane may comprise one or two membranes selected from the following: polyethylene and polypropylene.

[0254] Porous base membranes can be single-layer thin films or multi-layer composite thin films. When a porous base membrane is a multi-layer composite thin film, the materials of each layer can be the same or different.

[0255] In some embodiments, the electrolyte wetting length of the separator can be greater than or equal to 40 mm, and can be selected as 50 mm-60 mm.

[0256] The electrolyte wetting length of the separator can be tested as follows: at 25°C, cut the separator into a 5mm wide sample, fix both ends, and drop free electrolyte obtained from the secondary battery cell into the middle. Observe the electrolyte diffusion length, and take the stable diffusion length after 120s as the electrolyte wetting length of the separator.

[0257] In some embodiments, the thickness of the separator can be 4.5 μm-14 μm. This is beneficial for improving the energy density of the secondary battery cell.

[0258] In some embodiments, the porosity of the separator can be 25%-60%, optionally 40%-48%.

[0259] It should be noted that the heat-resistant layer parameters of the above-mentioned separator are all heat-resistant layer parameters of one side of the porous base membrane. When the heat-resistant layer is disposed on both sides of the porous base membrane, if the heat-resistant layer parameters of either side meet the requirements of this disclosure, it is considered to fall within the protection scope of this disclosure.

[0260] The secondary battery cells disclosed herein may include, but are not limited to, lithium battery cells, sodium battery cells, etc. The composition of the positive electrode, negative electrode and electrolyte may differ depending on the type of secondary battery cell.

[0261] [Positive electrode plate]

[0262] In some embodiments, the positive electrode may include 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.

[0263] Taking a lithium-ion battery cell as an example, the positive electrode active material may include, but is not limited to, one or more of lithium transition metal oxides, 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, and their respective modified compounds. 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 manganese iron phosphate, lithium manganese iron phosphate and carbon composites, and their respective modified compounds. In some embodiments, to further improve the energy density of the secondary battery cell, the positive electrode active material may include materials with the general formula Li a Ni b Co c M d O e A 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 includes but is not limited to one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A includes but is not limited to one or more of N, F, S and Cl.

[0264] As an example, the positive electrode active material may include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, and 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 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.85 Co 0.1 Al 0.05 One or more of O2, LiFePO4, and LiMnPO4.

[0265] During the charging and discharging process, Li undergoes insertion / extraction and consumption in a single secondary battery cell, resulting in varying molar Li content at different discharge states. In the examples of positive electrode active materials in this disclosure, the molar Li content represents the initial state of the material, i.e., the state before feeding. When the positive electrode active material is applied to a secondary battery cell, the molar Li content changes after charge-discharge cycles. Similarly, in the examples of positive electrode active materials in this disclosure, the molar O content is only a theoretical value. Lattice oxygen release causes changes in the molar O content, and the actual molar O content will also fluctuate.

[0266] Taking sodium-ion battery cells as an example, the positive electrode active material can be one or more of the following, including but not limited to sodium-containing transition metal oxides, polyanionic materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian blue materials. For example, the positive electrode active material can be, but is not limited to, NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, and NaNi 1 / 2 Ti 1 / 2 O2, NaNi 1 / 2 Mn 1 / 2 O2, Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2, NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, NaFePO4, NaMnPO4, NaCoPO4, Prussian blue materials, with the general formula X p M' q (PO4) r O x Y 3-x One or more of the materials. In general formula X p M' q (PO4) r O x Y 3-x In this case, 0 < p ≤ 4, 0 < q ≤ 2, 1 ≤ r ≤ 3, 0 ≤ x ≤ 2, and X includes, but is not limited to, H. + Li + Na + K + and NH4 + One or more of the following, M' is a transition metal cation, optionally including but not limited to one or more of V, Ti, Mn, Fe, Co, Ni, Cu and Zn, and Y is a halide anion, optionally one or more of F, Cl and Br.

[0267] The modified compounds for the positive electrode active materials of the aforementioned lithium battery cells and sodium battery cells can be obtained by doping and / or surface coating modifications of the positive electrode active materials.

[0268] In some embodiments, the positive electrode film layer may further 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.

[0269] In some embodiments, the positive electrode film layer may further include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0270] In some embodiments, the porosity of the positive electrode film can be 15%-30%.

[0271] The porosity of the positive electrode film can be tested as follows: Take a single-sided coated positive electrode sheet that has been cold-pressed (if it is a double-sided coated positive electrode sheet, the positive electrode film layer on one side can be wiped off first), cut it into small circular samples of a certain area, and calculate the apparent volume V1 of the positive electrode sheet; referring to GB / T 24586-2009, use an inert gas (such as helium or nitrogen) as the medium, adopt the gas replacement method, and use a true density meter to measure the true volume V2 of the positive electrode sheet. Porosity of the positive electrode film layer = (V1-V2) / V1×100%. Multiple samples (such as 30 pieces) with good appearance and no powder shedding at the edges can be tested, and the average value of the results can be taken to improve the accuracy of the test results. The testing instrument can be a Micromeritics AccuPyc II 1340 true density meter.

[0272] 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 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 aluminum, aluminum 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.

[0273] 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.

[0274] [Negative electrode plate]

[0275] In some embodiments, the negative electrode sheet may include a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and comprising a negative electrode active material. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0276] The negative electrode active material may be any material known in the art for use in secondary battery cells. As an example, the negative electrode active material may include, but is 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.

[0277] 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.

[0278] In some embodiments, the negative electrode film layer may further include a negative electrode binder. As an example, the negative electrode binder may include, but is not limited to, one or more of 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).

[0279] 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.

[0280] 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.

[0281] 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.

[0282] 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.

[0283] 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.

[0284] [Electrolytes]

[0285] The secondary battery cell also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and an organic solvent.

[0286] 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).

[0287] 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).

[0288] In some embodiments, the organic solvent may include, but is not limited to, one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl ester carbonate (BC), 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), diethyl sulfone (ESE), ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ether.

[0289] In some embodiments, the electrolyte may also 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 secondary battery cell, such as additives that improve overcharge performance, additives that improve high-temperature performance, additives that improve low-temperature performance, etc.

[0290] Optionally, the additive may include one or more of fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), and ethylene sulfate (DTD).

[0291] In some embodiments, the viscosity of the electrolyte at 25°C can be less than or equal to 5 mPa·s, and optionally less than or equal to 3 mPa·s. This helps to improve the electrolyte wettability of the secondary battery cell.

[0292] The viscosity of the electrolyte can be tested using a viscometer. When the rotor rotates continuously at a constant speed in the sample, the shear force it experiences causes the spring to generate torque. The torque is proportional to the viscosity, thus yielding the viscosity value of the sample.

[0293] For example, the viscosity of the electrolyte can be tested as follows: Under ambient humidity <80%, take a 30mL sample and keep it at a constant temperature of 25℃ in a water bath for at least 30 minutes. Place the rotor (e.g., a No. 18 rotor) into the sample cup, add the sample to about 0.3cm from the rim, start the connected viscometer, select a speed of 70RPM and rotate for 5 minutes to obtain the viscosity value. Ten data points can be collected during the test, and the average value is taken. The testing instrument can be a Bollerfeld DV-2TLV viscometer.

[0294] In some embodiments, the ionic conductivity of the electrolyte at 25°C can be 8mS / cm-16mS / cm, and can be selected as 9mS / cm-12mS / cm.

[0295] The ionic conductivity of the electrolyte can be obtained by testing with a conductivity meter. For example, a suitable amount of electrolyte can be taken, divided into three equal portions, and the conductivity of each sample can be measured using a conductivity meter at 25°C. The average value of the test results is then taken as the ionic conductivity of the electrolyte. A DDS-307 conductivity meter can be used as the testing instrument.

[0296] Methods for preparing secondary battery cells are well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a secondary battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly is then placed in a housing, an electrolyte is injected, and after encapsulation, settling, and other processes, a secondary battery cell is obtained.

[0297] In some embodiments, the method for preparing the separator membrane may include the following steps: providing a porous base membrane; providing a heat-resistant layer slurry comprising silicon-containing organic crosslinked resin particles and a binder; coating the heat-resistant layer slurry onto one or both sides of the porous base membrane; and drying it in an oven to obtain the separator membrane.

[0298] In some embodiments, the solvent for the heat-resistant layer slurry may be water, such as deionized water.

[0299] In some embodiments, the heat-resistant slurry may also include other components, such as dispersants and / or wetting agents.

[0300] In some embodiments, the viscosity of the heat-resistant slurry at 25°C can be 50 mPa·s to 500 mPa·s.

[0301] In some embodiments, the solid content of the heat-resistant slurry can be 10%-25%.

[0302] In some embodiments, the zeta potential of the heat-resistant slurry is -90mV to -30mV.

[0303] In some embodiments, the method for preparing the separator includes the following steps: coating a heat-resistant layer slurry on one or both sides of a porous base membrane, drying it in an oven to form a heat-resistant layer, then coating an adhesive layer slurry comprising polymer binder particles and an adhesive onto at least a portion of the surface of the heat-resistant layer, and then drying it in an oven to obtain the separator.

[0304] In some embodiments, the method for preparing the separator membrane includes the following steps: coating a heat-resistant layer slurry on one side of a porous base membrane, coating an adhesive layer slurry including polymer binder particles and binder on at least a portion of the surface of the other side of the porous base membrane, and drying it in an oven to obtain the separator membrane.

[0305] In some embodiments, the solvent for the adhesive layer slurry may be water, such as deionized water.

[0306] In some embodiments, the adhesive layer slurry may also include other components, such as dispersants and / or wetting agents.

[0307] In some embodiments, the adhesive layer slurry can be applied by spraying.

[0308] Example

[0309] The following embodiments describe the disclosure of this disclosure 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 this disclosure. 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.

[0310] Example 1

[0311] Preparation of the separating membrane

[0312] Silicon-containing organic crosslinked resin particles, dispersant sodium carboxymethyl cellulose, and binder polyacrylate were mixed evenly in deionized water in a certain proportion to obtain a heat-resistant layer slurry. The solid mass ratio of the silicon-containing organic crosslinked resin particles, dispersant sodium carboxymethyl cellulose, and binder polyacrylate in the heat-resistant layer slurry was 90:2:8.

[0313] Commercially available polyvinylidene fluoride granules (polymer binder particles), polyacrylate binder, sodium carboxymethyl cellulose dispersant, and ether-based surfactants were mixed evenly in deionized water at a solid content mass ratio of 87:8:3:2 to obtain the adhesive layer slurry.

[0314] A commercially available 7μm thick polyethylene microporous film was used as the porous base membrane. The prepared heat-resistant layer slurry was coated onto both surfaces of the porous base membrane using a microgravure process. After oven drying, an adhesive layer slurry was sprayed on, followed by oven drying and slitting to obtain the release membrane. The volume distribution particle size (Dv50) of the silicone organic crosslinked resin particles in the heat-resistant layer was 100nm, and the particle size distribution (Dv90-Dv10) / Dv50 was 0.99. The thickness of the heat-resistant layer was 1.5μm, and the bulk density was 1.47g / cm³. 3 The volume distribution particle size (Dv50) of the polyvinylidene fluoride (PVDF) particles in the adhesive layer is 7 μm. The silicon-containing organic cross-linked resin particles in the heat-resistant layer also meet the following characteristics: spherical morphology, hydroxyl groups on the particle surface, a network structure formed by carbon-carbon bonds as the main chain, silicon-oxygen structures in the side chains, and no melting point or glass transition temperature.

[0315] Preparation of secondary battery cells

[0316] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2, positive electrode binder polyvinylidene fluoride (PVDF), and positive electrode conductive agent carbon black are added to N-methylpyrrolidone (NMP) in a mass ratio of 97:2:1 and thoroughly mixed to prepare a positive electrode slurry. The positive electrode slurry is then uniformly coated onto the positive electrode current collector aluminum foil, and subsequently dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0317] Artificial graphite (anode active material), acetylene black (anode conductive agent), styrene-butadiene rubber (SBR) (anode binder), and sodium carboxymethyl cellulose (thickener) were added to deionized water at a mass ratio of 96.0:1.5:1.5:1. After thorough mixing, a cathode slurry was prepared. The cathode slurry was then uniformly coated onto copper foil (anode current collector), and subsequently dried, cold-pressed, and slit to obtain the cathode sheet.

[0318] At 25°C, ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3:7 to obtain a mixed solvent. LiPF6, vinylene carbonate (VC), and vinyl sulfate (DTD) were then dissolved in this mixed solvent to obtain the electrolyte. The concentration of LiPF6 was 1 mol / L. The mass fraction of VC was 2%, and the mass fraction of DTD was 3%, based on the mass of the electrolyte.

[0319] The positive electrode, separator, and negative electrode are stacked, wound, and hot-pressed in sequence to obtain an electrode assembly. The electrode assembly is placed in a hard shell, and the electrolyte prepared above is added. After encapsulation, settling, and formation processes, a secondary battery cell is obtained. The dimensions of the secondary battery cell are 33.4mm * 221.1mm * 102.3mm (thickness * length * width), that is, the dimension of the secondary battery cell in the first direction is 221.1mm.

[0320] Examples 2 to 3

[0321] Except for the following differences, the preparation process of the secondary battery cell is the same as that in Example 1.

[0322] In the isolation membrane prepared in Example 2: the volume distribution particle size Dv50 of the silicon-containing organic crosslinked resin particles in the heat-resistant layer is 200 nm, and the particle size distribution (Dv90-Dv10) / Dv50 is 1.01; the thickness of the heat-resistant layer is 1.5 μm, and the bulk density is 1.33 g / cm³. 3 The volume distribution particle size (Dv50) of the polyvinylidene fluoride (PVDF) particles in the adhesive layer is 7 μm. The silicon-containing organic cross-linked resin particles in the heat-resistant layer also meet the following characteristics: spherical morphology, hydroxyl groups on the particle surface, a network structure formed by carbon-carbon bonds as the main chain, silicon-oxygen structures in the side chains, and no melting point or glass transition temperature.

[0323] In the isolation membrane prepared in Example 3: the volume distribution particle size Dv50 of the silicon-containing organic crosslinked resin particles in the heat-resistant layer is 300 nm, and the particle size distribution (Dv90-Dv10) / Dv50 is 1.02; the thickness of the heat-resistant layer is 1.5 μm, and the bulk density is 1.20 g / cm³. 3 The volume distribution particle size (Dv50) of the polyvinylidene fluoride (PVDF) particles in the adhesive layer is 7 μm. The silicon-containing organic cross-linked resin particles in the heat-resistant layer also meet the following characteristics: spherical morphology, hydroxyl groups on the particle surface, a network structure formed by carbon-carbon bonds as the main chain, silicon-oxygen structures in the side chains, and no melting point or glass transition temperature.

[0324] Comparative Example 1

[0325] Except for the following differences, the preparation process of the secondary battery cell is the same as that in Example 1.

[0326] Preparation of the separating membrane

[0327] Alumina, sodium carboxymethyl cellulose dispersant, and polyacrylate binder were mixed evenly in deionized water in a certain proportion to obtain a heat-resistant slurry. The solid mass ratio of alumina, sodium carboxymethyl cellulose dispersant, and polyacrylate binder in the first slurry was 90:2:8.

[0328] Commercially available polyvinylidene fluoride granules (polymer binder particles), polyacrylate binder, sodium carboxymethyl cellulose dispersant, and ether-based surfactants were mixed evenly in deionized water at a solid content mass ratio of 87:8:3:2 to obtain the adhesive layer slurry.

[0329] A commercially available 7μm thick polyethylene microporous film was used as the porous base membrane. The prepared heat-resistant layer slurry was coated onto both surfaces of the porous base membrane using a microgravure process. After oven drying, an adhesive layer slurry was sprayed on, followed by oven drying and slitting to obtain the release membrane. The alumina in the heat-resistant layer had a blocky morphology with a volumetric particle size distribution (Dv50) of 800 nm and a particle size distribution (Dv90-Dv10) / Dv50 of 1.20. The heat-resistant layer had a thickness of 1.5μm and a bulk density of 3.33 g / cm³. 3 The volume distribution particle size Dv50 of the polyvinylidene fluoride particles in the adhesive layer is 7 μm.

[0330] Performance testing

[0331] (1) Thermal shrinkage rate test of the separator film

[0332] The heat shrinkage rate test of the release liner can be referenced in GB / T 36363-2018. An example can be found by following these steps:

[0333] Cut the release film into samples with a width of 50mm and a length of 100mm using a punching machine. Take 5 parallel samples and place them on A4 paper. Then place the A4 paper containing the samples on corrugated paper with a thickness of 1mm to 5mm.

[0334] Set the temperature of the forced-air drying oven to 130℃. After the temperature reaches the set temperature and stabilizes for 60 minutes, place the A4 paper placed on the corrugated paper into the forced-air drying oven and start timing. After the set time (1 hour in this disclosure) is reached, measure the length and width of the isolation film, and mark the values ​​as a and b respectively.

[0335] Calculation of heat shrinkage rate: Longitudinal (MD) heat shrinkage rate = [(100-a) / 100]×100%, Transverse (TD) heat shrinkage rate = [(50-b) / 50]×100%, take the average value of 3 parallel samples as the test result.

[0336] (2) Electrolyte wettability test of the separator

[0337] At 25°C, the separator was cut into 5mm wide samples, both ends were fixed, and the electrolyte of Example 1 was dropped into the middle. The diffusion length of the electrolyte was observed, and the stable diffusion length after 120s was taken as the electrolyte wetting length of the separator.

[0338] (3) Electrode assembly electrolyte wettability test

[0339] At 25°C, a clamp is used to fit the electrode assembly being measured, ensuring the electrode assembly is locked in place, with one side of the tab at the top and the other side protruding 1 cm from the clamp. A copper wire is threaded through the clamp to suspend the electrode assembly. The sealed container is placed on a balance, with the clamp positioned in the center of the container without touching the walls. The electrolyte from Example 1 is poured into the sealed container, with only the bottom of the electrode assembly immersed in the electrolyte. The software is opened to record data. The cap is then fixed. Data processing: After a certain period of time, the data is saved and subjected to appropriate fitting processing. The mass change point of the electrode assembly absorbing the electrolyte is taken as the starting point of the data, with the horizontal axis representing t^0.5 and the vertical axis representing mass. The slope can represent the rate at which the electrode assembly absorbs the electrolyte.

[0340] (4) Cycle performance test of secondary battery cells

[0341] At 45℃, a single secondary battery cell is charged to 4.25V at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 4.25V, left to rest for 5 minutes, and then discharged to 2.8V at a constant current of 1 / 3C. The resulting discharge capacity is recorded as the initial capacity C0. This charging and discharging process is repeated, and the discharge capacity Cn of the single secondary battery cell after the nth cycle is recorded. The capacity retention rate of the single secondary battery cell after each cycle is Pn = (Cn / C0) × 100%. The capacity retention rate of the single secondary battery cell after 500 cycles can be used to reflect the difference in cycle performance of the single secondary battery cell.

[0342] Table 1

[0343] The test results above show that the silicon-containing organic cross-linked resin particles of this disclosure can give the separator high heat resistance, as well as good electrolyte wettability and electrolyte retention. This reduces the risk of metal deposition at the edges and tabs of the secondary battery cells, thus enabling the secondary battery cells to have both high reliability and good cycle performance. The silicon-containing organic cross-linked resin particles of this disclosure have regular morphologies, such as spherical, near-spherical, ellipsoidal, and near-ellipsoidal shapes. These morphologies result in high space utilization, contributing a significant amount of space for electrolyte storage. This promotes rapid electrolyte wetting of the separator while simultaneously storing the electrolyte within the pores of the separator, forming ion transport channels, thereby improving the cycle performance of the secondary battery cells.

[0344] It should be noted that this disclosure is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same essential structure and achieving the same effect as the technical concept within the scope of this disclosure are included in the technical scope of this disclosure. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, are also included in the scope of this disclosure without departing from the spirit of this disclosure.

Claims

1. A secondary battery cell, comprising: a case having an opening at at least one end in a first direction; an electrode assembly provided in the case; and a terminal cover closing the opening; the secondary battery cell having a size of 220 mm to 500 mm in the first direction; the electrode assembly including a positive electrode sheet, a negative electrode sheet, and a separator provided between the positive electrode sheet and the negative electrode sheet, the separator including a porous base film and a heat-resistant layer provided on one side or both sides of the porous base film, the heat-resistant layer including silicon-containing organic crosslinking resin particles. The silicon-containing organic crosslinking resin particles have a surface with hydroxyl groups; optionally, the content of the hydroxyl groups in the silicon-containing organic crosslinking resin particles is 500 μg / g to 700 μg / g. The silicon-containing organic crosslinking resin particles satisfy one or more of the following conditions (1) to (5): (1) the silicon-containing organic crosslinking resin particles have no melting point; (2) the silicon-containing organic crosslinking resin particles have no glass transition temperature; (3) the silicon-containing organic crosslinking resin particles have a swelling degree of 3% or less when immersed in a mixed solvent of ethylene carbonate and methyl ethyl carbonate at a volume ratio of 3:7 at 60°C for 7 days; (4) the silicon-containing organic crosslinking resin particles have a dissolution rate of 3% or less when immersed in a mixed solvent of ethylene carbonate and methyl ethy carbonate at a volume ratio of 3:7 at 60°C for 7 days; and (5) the silicon-containing organic crosslinking resin particles have no oxidation peak in a cyclic voltammogram of the first cycle in a voltage range of 2.5 V to 4.4 V. The silicon-containing organic crosslinking resin particles contain carbon-carbon bonds and siloxane structures. The silicon-containing organic crosslinking resin particles are network structures formed with carbon-carbon bonds as a main chain, and side chains containing siloxane structures. The silicon-containing organic crosslinking resin particles are network structures formed with a carbon-carbon bond as a main chain, and side chains containing siloxane structures and benzene ring structures. The silicon-containing organic crosslinking resin particles include one or more of a crosslinking structure unit including a divinylbenzene structure unit, a diethylene glycol divinyl ether structure unit, a triethylene glycol divinyl ether structure unit, a maleic acid diallyl ester structure unit, an ethylene glycol dimethacrylate structure unit, a 1,4-butanediol diacrylate structure unit, a 1,6-hexanediol diacrylate structure unit, a 1,8-octanediol diacrylate structure unit, a trimethylolpropane triacrylate structure unit, a pentaerythritol trimethacrylate structure unit, a tetraethylene glycol dimethacrylate structure unit, a tripropylene glycol diacrylate structure unit, a 2,2,4-trimethyladipoyl bis[2-ethylaziridine] structure unit, a 1,1-sebacoyl bis[2-methylaziridine] structure unit, a 1,1-(1,3-phenylenedicarbonyl) bis[2-methylaziridine] structure unit, a trimethylolpropane tris(2-methyl-1-aziridinyl propionate) structure unit, a trimethylolpropane-tris[3-(2-methylaziridinyl) propionate] structure unit, and a pentaerythritol tri(3-aziridinyl) propionate structure unit.

2. The secondary battery cell according to claim 1, wherein ​ 3. The secondary battery cell according to any one of claims 1-2, wherein, ​ ​ ​ ​ ​ ​ 4. The secondary battery cell according to any one of claims 1 to 3, wherein ​ 5. The secondary battery cell according to claim 4, wherein ​ 6. The secondary battery cell according to claim 5, wherein ​ 7. The secondary battery cell according to any one of claims 4 to 6, wherein ​ 8. The secondary battery cell according to any one of claims 1 to 3, wherein The silicon-containing organic cross-linking resin particles include a polysilsesquioxane, and the polysilsesquioxane satisfies one or both of the following conditions (1) and (2): (1) The weight average molecular weight of the polysilsesquioxane is 10,000-100,000; (2) the structure of the polysilsesquioxane includes: R1, R2 each independently include an alkyl group of 1-12 carbon atoms, an unsaturated hydrocarbon group of 2-12 carbon atoms, or a phenyl group, and n = 50-1000.

9. The secondary battery cell according to claim 8, wherein The polysilsesquioxane comprises at least one of the following structural formulas: Ph represents a phenyl group, and n = 50-1000.

10. The secondary battery cell according to any one of claims 1 to 9, wherein The heat resistant layer has a bulk density of 0.4 g / cm 3 -1.5 g / cm 3 , optionally 1 g / cm 3 -1.5 g / cm 3 .

11. The secondary battery cell according to any one of claims 1-10, wherein, The morphology of the silicon-containing organic cross-linking resin particles includes one or more of a spherical shape, a spherical-like shape, an ellipsoidal shape, and an ellipsoidal-like shape; and / or, The volume distribution particle size Dv50 of the silicon-containing organic cross-linking resin particles is less than 1 μm, and is optionally 60 nm-800 nm; and / or, The particle size distribution (Dv90-Dv10) / Dv50 of the silicon-containing organic cross-linking resin particles is 0.2-1.1; and / or, The mass ratio of the silicon-containing organic cross-linking resin particles in the heat-resistant layer is greater than or equal to 80%.

12. The secondary battery cell according to any one of claims 1 to 11, wherein The true density of the silicon-containing organic crosslinked resin particles is 1.0 g / cm 3 -1.5 g / cm 3 .

13. The secondary battery cell according to any one of claims 1 to 12, wherein The heat-resistant layer includes a binder, and the binder includes one or more of a hydroxyl group, a carboxyl group, a carboxylate group, an ester group, an epoxy group, and an amide group.

14. The secondary battery cell according to claim 13, wherein, The mass ratio of the binder in the heat-resistant layer is greater than or equal to 1%; and / or, The binder includes one or more of a polyacrylate-based binder, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

15. The secondary battery cell according to any one of claims 1-14, the separator further including a bonding layer disposed on at least a portion of a surface of the heat-resistant layer or the porous base film, and the bonding layer includes polymer binder particles having a volume distribution particle size Dv50 of 6 μm-18 μm.

16. The secondary battery cell according to claim 15, wherein, The polymer binder particles include one or more of fluorine-containing polymer binder particles and non-fluorine polymer binder particles; and / or, The polymer binder particles include an aggregate of primary particles.

17. The secondary battery cell according to any one of claims 1-16, wherein, The ratio of the volume distribution particle size Dv50 of the silicon-containing organic cross-linking resin particles to the average pore diameter of the porous base film is greater than or equal to 1.2; and / or, The average pore diameter of the porous base film is 25 nm-80 nm; and / or, The porosity of the porous base film is 25%-60%, and is optionally 30%-40%; and / or, The thickness of the porous base film is 3 μm-11 μm, and is optionally 3 μm-7 μm.

18. The secondary battery cell according to any one of claims 1-17, wherein, The thickness of the heat-resistant layer is 0.4 μm-5 μm; and / or, The electrolyte impregnation length of the separator is greater than or equal to 40 mm, and is optionally 50 mm-60 mm; and / or, The total thickness of the separator is 4.5 μm-14 μm; and / or, The porosity of the separator film is 25%-60%, and optionally 40%-48%. 19.The secondary battery cell of any one of claims 1-18, wherein, The positive electrode tab includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material, the positive electrode film layer having a porosity of 15%-30%; and / or, The secondary battery cell includes an electrolyte, the electrolyte having a viscosity of less than or equal to 5 mPa·s at 25 ℃; and / or, The secondary battery cell includes an electrolyte, the electrolyte having an ionic conductivity of 8 mS / cm-16 mS / cm at 25 ℃. 20.A battery device comprising a plurality of the secondary battery cell of any one of claims 1-19. 21.A power-using device comprising the secondary battery cell of any one of claims 1-19 or the battery device of claim 20.

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