Separator and preparation method therefor, secondary battery cell, battery device, and electric device

Abstract

A separator and a preparation method therefor, a secondary battery cell, a battery device, and an electric device. The separator comprises a porous base membrane and a porous coating located on at least one side of the porous base membrane. The porous coating comprises organic particles of phenolic resins and fibrous materials, and at least a portion of the organic particles of phenolic resins are located between the fibrous materials. The separator is used in a secondary battery cell, such that the secondary battery cell has both a high quality energy density and high reliability.

Description

Separator and method for manufacturing the same, secondary battery cell, battery device, and power using device

[0001] Cross Reference to Related Applications

[0002] This application claims priority to Chinese Patent Application No. 202411387965.0, filed on September 30, 2024, entitled “Separator and method for manufacturing the same, secondary battery cell, battery device, and power using device”, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates to a separator and method for manufacturing the same, secondary battery cell, battery device, and power using device. BACKGROUND

[0004] With the increasingly wide range of applications of secondary battery cells, people’s demand for the use of secondary battery cells is also increasing, such as the increasingly high requirements for the energy density and reliability of secondary battery cells. Therefore, how to make the secondary battery cell have higher energy density under the premise of high reliability is a technical problem to be solved at present. SUMMARY

[0005] The present disclosure provides a separator and method for manufacturing the same, secondary battery cell, battery device, and power using device, which is used in a secondary battery cell and can make the secondary battery cell have high mass energy density and high reliability.

[0006] In a first aspect, the present disclosure provides a separator, which comprises a porous base film and a porous coating layer located on at least one side of the porous base film, the porous coating layer comprising phenolic resin-based organic particles and fibrous material, and at least part of the phenolic resin-based organic particles being located between the fibrous material.

[0007] The density of the phenolic resin-based organic particles and the fibrous material is small, so that the secondary battery cell using the same can have higher mass energy density. The porous coating layer of the separator of the present disclosure comprises a mixture of phenolic resin-based organic particles and fibrous material, and after the introduction of the fibrous material, the phenolic resin-based organic particles can be connected in series and dispersed, so that the structural property and heat resistance of the whole porous coating layer can be improved, thereby reducing the thermal shrinkage of the whole separator, improving the reliability of the secondary battery cell, and also improving the air permeability of the whole separator. Therefore, the separator of the present disclosure can make the secondary battery cell have high mass energy density and high reliability.

[0008] In some embodiments, the phenolic resin-based organic particles have no glass transition temperature below 300°C. The phenolic resin-based organic particles have no glass transition temperature below 300°C, which means that the phenolic resin-based organic particles have good heat resistance and thermal stability, and thus can better resist thermal shrinkage of the porous base film, improve the heat resistance of the separator film, and improve the reliability of the secondary battery cell.

[0009] In some embodiments, the phenolic resin-based organic particles have no melting point. The phenolic resin-based organic particles have no melting point, which means that the phenolic resin-based organic particles have good heat resistance and thermal stability, and thus can better resist thermal shrinkage of the porous base film, improve the heat resistance of the separator film, and improve the reliability of the secondary battery cell.

[0010] In some embodiments, the phenolic resin-based organic particles are thermosetting resol.

[0011] In some embodiments, the phenolic resin-based organic particles have a dissolution rate of less than or equal to 3% when 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. The phenolic resin-based organic particles have a low dissolution rate in organic solvents, which means that the phenolic resin-based organic particles have high structural stability during long-term use of the secondary battery cell and high chemical stability in the electrolyte, and thus the secondary battery cell has longer cycle stability.

[0012] In some embodiments, the phenolic resin-based organic particles have a swelling degree of less than or equal to 3% when 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. The phenolic resin-based organic particles have a low swelling degree in organic solvents, which means that the phenolic resin-based organic particles have high structural stability during long-term use of the secondary battery cell, and thus improve the problem of decreased air permeability of the separator film during use.

[0013] In some embodiments, the phenolic resin-based organic particles have no oxidation peak in the cyclic voltammetry curve of the first cycle in the voltage range of 2.50V to 4.40V. The phenolic resin-based organic particles have no oxidation peak in the cyclic voltammetry curve of the first cycle in the voltage range of 2.50V to 4.40V, which means that the phenolic resin-based organic particles are stable in the voltage range of 2.50V to 4.40V. Therefore, the phenolic resin-based organic particles of the present disclosure have good electrochemical stability, can be applied to high-voltage secondary battery cells, improve the operating voltage and energy density of the secondary battery cell, and also enable the secondary battery cell to have good capacity performance characteristics at high voltage.

[0014] In some embodiments, the phenolic resin-based organic particles have a volume distribution particle size Dv50 of 160nm-800nm. The phenolic resin-based organic particles have a volume distribution particle size Dv50 in the above range, which is beneficial to the separator film having good heat resistance and air permeability.

[0015] In some embodiments, the phenolic resin-based organic particles have a true density of 1.0 g / cm3-1.4 g / cm3. 3 -1.4 g / cm3 3 .

[0016] In some embodiments, the fibrous material has a diameter ranging from 10 nm to 200 nm.

[0017] In some embodiments, the fibrous material has a length ranging from 0.15 μm to 30 μm. The fibrous material having a length ranging from 0.15 μm to 30 μm can better connect the phenolic resin-based organic particles, improve the overall structural property and heat resistance of the separation membrane, and reduce the thermal shrinkage of the separation membrane.

[0018] In some embodiments, the fibrous material comprises one or more of a sugar-based fiber, a protein-based fiber, a polymer fiber, and an inorganic fiber.

[0019] In some embodiments, the fibrous material comprises one or more of an alginate fiber and a derivative thereof, a nanocellulose fiber and a derivative thereof, a chitosan fiber and a derivative thereof, a chitin fiber and a derivative thereof, a plant cellulose, a silk fibroin fiber, a spider silk protein fiber, a corn protein fiber, a soy protein fiber, a keratin fiber, a wool fiber, a cashmere fiber, an aramid fiber, a polyester fiber, a polyamide fiber, a polyacrylonitrile fiber, a polyvinyl alcohol fiber, a polyethylene fiber, an ultrahigh molecular weight polyethylene fiber, a polypropylene fiber, a polytetrafluoroethylene fiber, a polyvinylidene fluoride fiber, a polyurethane fiber, an acetate fiber, a polycaprolactone fiber, a polylactic acid fiber, a polyether sulfone fiber, an acrylic fiber, an acrylic polymer fiber, a polymethyl methacrylate fiber, a poly-2-hydroxyethyl methacrylate fiber, a polyethylene terephthalate fiber, a polyethylene terephthalate fiber, a para-phenylenediamine fiber, a glass fiber, an asbestos fiber, and a silica fiber.

[0020] In some embodiments, the fibrous material has a polar group.

[0021] Optionally, the polar group comprises one or more of a hydroxyl group, a carboxyl group, an ester group, an amide group, a cyano group, an amine group, an aldehyde group, a sulfonic acid group, a boronic acid group, and a phosphoric acid group.

[0022] The fibrous material having a polar group can have a stronger interaction with the binder in the porous coating, such as forming a hydrogen bond or an ionic bond, etc., so that the adhesion between the porous coating and the porous base film is stronger, thereby improving the overall structural property of the separation membrane and the heat resistance of the separation membrane.

[0023] In some embodiments, the mass content of the phenolic resin-based organic particles in the porous coating is greater than or equal to 55% based on the total mass of the porous coating.

[0024] In some embodiments, the mass content of the fibrous material in the porous coating is 0.3%-30% based on the total mass of the porous coating.

[0025] The mass content of the fibrous material in the above range can make the separator film have good heat resistance and air permeability, thereby making the secondary battery cell have high reliability and good cycle performance.

[0026] In some embodiments, the porous coating further comprises a binder.

[0027] In some embodiments, the thickness of the porous coating is 0.4 μm-5 μm.

[0028] In a second aspect, the present disclosure provides a method for preparing the separator film of the first aspect, comprising the following steps: providing a porous base film; providing a slurry comprising phenolic resin-based organic particles, fibrous material, and a binder; coating the slurry on at least one side of the porous base film to obtain the separator film after drying.

[0029] In some embodiments, the method for providing the phenolic resin-based organic particles comprises the following steps: providing a resol resin-based material; curing the resol resin-based material at a first temperature and in a first atmosphere for a first time, then curing at a second temperature and in a second atmosphere for a second time, and then crushing and grinding to obtain the phenolic resin-based organic particles, wherein the first temperature is 90°C-180°C, and the second temperature is 190°C-290°C.

[0030] In some embodiments, the first time is 1h-5h.

[0031] In some embodiments, the second time can be 1h-6h.

[0032] In some embodiments, the first atmosphere is an inert gas atmosphere or an oxygen-containing atmosphere, and the volume fraction of oxygen in the oxygen-containing atmosphere is 5%-50%.

[0033] In some embodiments, the second atmosphere is an inert gas atmosphere or an oxygen-containing atmosphere, and the volume fraction of oxygen in the oxygen-containing atmosphere is 5%-50%.

[0034] In some embodiments, the step of providing the resol resin-based material comprises the following steps: reacting a phenolic compound and an aldehyde compound under the catalysis of an alkaline substance to obtain the resol resin-based material.

[0035] In some embodiments, the phenolic compound includes one or more of phenol, hydroquinone, resorcinol, catechol, cresol, and cardanol.

[0036] In some embodiments, the aldehyde compound includes one or more of formaldehyde, paraformaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, glyoxal, and furfural.

[0037] In some embodiments, the basic substance includes one or more of ammonia, NaOH, and Na2CO3.

[0038] In a third aspect, the present disclosure provides a secondary battery cell including a positive electrode sheet, a negative electrode sheet, and the separator of the first aspect of the present disclosure, the separator being disposed between the positive electrode sheet and the negative electrode sheet.

[0039] In a fourth aspect, the present disclosure provides a battery device including a plurality of the secondary battery cell of the third aspect of the present disclosure.

[0040] In a fifth aspect, the present disclosure provides an electric device including the secondary battery cell of the third aspect of the present disclosure or the battery device of the fourth aspect of the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings needed to be used in the embodiments of the present disclosure will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present disclosure, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the drawings.

[0042] FIG. 1 shows a schematic diagram of a secondary battery cell according to some embodiments of the present disclosure.

[0043] FIG. 2 shows a schematic diagram of an electric device according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0044] Hereinafter, specific embodiments of the separator and the method for manufacturing the same, the secondary battery cell, the battery device, and the electric device of the present disclosure will be described in detail with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed descriptions are omitted. For example, there will be cases where detailed descriptions of matters known to those skilled in the art, repeated descriptions of substantially identical configurations are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter recited in the claims.

[0045] The ranges disclosed herein are defined by their lower and upper endpoints, given that a range is defined by selecting a lower endpoint and an upper endpoint, the selected lower and upper endpoints define the boundaries of the particular range. Ranges defined by endpoints can be either inclusive or exclusive of the endpoints, and can be arbitrarily combined, i.e., any lower endpoint can be combined with any upper endpoint to form a range. For example, if ranges of 60-120 and 80-110 are listed, it is understood that ranges of 60-110 and 80-120 are also contemplated. Also, if minimum range values of 1 and 2 are listed, and if maximum range values of 3, 4, and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present disclosure, unless otherwise stated, a numerical range "a-b" indicates a shorthand way of describing all of the individual real combinations that fall between "a" and "b", where "a" and "b" are both real numbers. For example, the numerical range "0-5" indicates that all of the real numbers between "0" and "5" have been listed herein, and "0-5" is merely a shorthand way of describing these numerical combinations. In addition, when a parameter is stated to be an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0046] Unless otherwise specified, all embodiments and optional embodiments of the present disclosure can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present disclosure.

[0047] Unless otherwise specified, all technical features and optional technical features of the present disclosure can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present disclosure.

[0048] Unless otherwise specified, all steps of the present disclosure can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0049] Unless otherwise specified, in the present disclosure, the terms "first", "second", etc. are used to distinguish different objects, and are not used to describe a particular order or primary and secondary relationship.

[0050] In the present disclosure, the terms "a plurality of", "a plurality of" refer to two or more.

[0051] In the description of the embodiments of the present disclosure, if there is no special indication, the first feature is "on" or "under" the second feature, which can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature can be "above", "over" and "on" the second feature, which can be that the first feature is directly above or obliquely above the second feature, or only means that the horizontal height of the first feature is higher than that of the second feature. The first feature can be "below", "under" and "under" the second feature, which can be that the first feature is directly below or obliquely below the second feature, or only means that the horizontal height of the first feature is less than that of the second feature.

[0052] Unless otherwise specified, the test temperature of each parameter mentioned in the present disclosure is 25°C.

[0053] The secondary battery cell mentioned in the embodiments of the present disclosure can realize the function of charging and discharging independently, and can continue to be used by activating the active material through charging after discharging. The secondary battery cell can be in the shape of a cylinder, a cuboid or other shapes, which are not limited in the embodiments of the present disclosure. As shown in FIG. 1, the secondary battery cell 5 is a cuboid structure as an example.

[0054] The secondary battery cell provided by the embodiments of the present disclosure can include but is not limited to lithium battery cells, sodium battery cells, such as lithium ion battery cells, sodium ion battery cells, lithium metal battery cells, sodium metal battery cells, etc.

[0055] The secondary battery cell provided by the embodiments of the present disclosure includes an electrode assembly. The electrode assembly can be a winding structure or a stacking structure, which is not limited in the embodiments of the present disclosure. The secondary battery cell further includes an outer package, which can be used to package the electrode assembly. The outer package can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, such as one or more of aluminum plastic film, polypropylene, polybutylene terephthalate (PBT) and polybutylene succinate (PBS).

[0056] The battery apparatus mentioned in the embodiments of the present disclosure can include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly can include a plurality of secondary battery cells connected in series, in parallel or in a mixed manner through a busbar component.

[0057] In some embodiments, the battery cell assembly is usually formed by arranging a plurality of secondary battery cells.

[0058] As an example, the battery cell assembly can be a battery module, which is formed by arranging and fixing a plurality of secondary battery cells.

[0059] In some embodiments, the battery device can be a battery pack, which includes a case and one or more battery cell assemblies, the battery cell assemblies being accommodated in the case.

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

[0061] As an example, the battery cell assembly can also be accommodated in the case by directly fixing a plurality of secondary battery cells in the case.

[0062] As an example, the case can include a first case and a second case. The first case and the second case are fastened so that an enclosed space is formed inside the case to accommodate the battery cell assembly. Here, the enclosed means covered or closed, which can be sealed or unsealed. The first case can be a top cover or a bottom plate.

[0063] As an example, the case can include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are connected to the frame, respectively, so that an enclosed space is formed inside the case to accommodate the battery cell assembly.

[0064] In some embodiments, the case can be part of a chassis structure of a vehicle. For example, part of the case can be at least part of a floor of the vehicle, or part of the case can be at least part of a cross beam and a longitudinal beam of the vehicle.

[0065] The technical solutions described in the embodiments of the present disclosure are applicable to various electric devices using secondary battery cells and battery devices, such as mobile devices (e.g., mobile phones, tablet computers, notebook computers, 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. The secondary battery cells and the battery devices are used to store or provide electric energy.

[0066] FIG. 2 is a schematic diagram of an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0067] In the context of the present disclosure, the “phenol resin-based organic particles” mainly play a role in improving heat resistance in the porous coating of the separator film, and almost have no adhesiveness.

[0068] The separator film is an important component for supporting the secondary battery cell to complete the charge and discharge electrochemical process. The commonly used separator film is mostly polyolefin film. However, the heat resistance of the polyolefin film is poor, and the polyolefin film is easy to soften or melt at high temperature, which may cause short circuit of the secondary battery cell. In order to improve the heat resistance of the separator film, a coating layer is usually coated on the separator film to improve the heat resistance of the separator film. Boehmite, alumina and other inorganic particles are currently commonly used heat-resistant fillers. However, the density of such heat-resistant fillers is large, and the mass is large under the same packing volume, which affects the energy density of the secondary battery cell.

[0069] Therefore, the separator film provided by the embodiments of the present disclosure can make the secondary battery cell have high mass energy density and high reliability.

[0070] The separator film provided by the embodiments of the present disclosure includes a porous base film and a porous coating layer located on at least one side of the porous base film. The porous coating layer includes phenolic resin organic particles and fibrous material, and at least part of the phenolic resin organic particles are located between the fibrous material.

[0071] The porous base film and the porous coating layer both have a pore structure, so that the separator film has good air permeability and facilitates the passage of ions.

[0072] The density of the phenolic resin organic particles and the fibrous material is small, so that the secondary battery cell using the same has higher mass energy density.

[0073] The heat resistance of the phenolic resin organic particles alone used in the separator film is not excellent at a higher temperature. The fibrous material has the characteristics of high strength, high heat resistance and low heat shrinkage, but has a small diameter. If the fibrous material is used alone and used in the separator film, there may be a problem of reducing the air permeability of the separator film. The porous coating layer of the separator film provided by the embodiments of the present disclosure includes a mixture of the phenolic resin organic particles and the fibrous material. After the introduction of the fibrous material, the phenolic resin organic particles are connected in series and dispersed, so that the structure and heat resistance of the whole porous coating layer can be improved, thereby reducing the heat shrinkage of the whole separator film, improving the reliability of the secondary battery cell, and improving the air permeability of the whole separator film.

[0074] Therefore, the separator film provided by the embodiments of the present disclosure can make the secondary battery cell have high mass energy density and high reliability.

[0075] In some embodiments, the true density of the phenolic resin organic particles can be 1.0 g / cm 3 -1.4 g / cm 3 .

[0076] At present, the true density of boehmite, alumina and other inorganic particles is usually 2.5 g / cm 3 -3.5 g / cm 3The phenolic resin-based organic particles of the present disclosure have a low true density, and thus can allow the secondary battery cell employing the separator film of the present disclosure to have a higher mass energy density.

[0077] In some embodiments, the phenolic resin-based organic particles have no glass transition temperature below 300°C.

[0078] The phenolic resin-based organic particles have no glass transition temperature below 300°C, which indicates that they have good heat resistance and thermal stability, and thus can better resist thermal shrinkage of the porous base film, improve the heat resistance of the separator film, and improve the reliability of the secondary battery cell.

[0079] The glass transition temperature T g The test can be performed as follows: take an appropriate amount of sample (e.g., 5-15 mg) and place it in a differential scanning calorimeter (DSC) crucible, shake it flat, and cover it with a crucible cover; parameter settings: nitrogen atmosphere, purge gas 60 mL / min, protective gas 20 mL / min; program settings: increase the temperature from 25°C to 200°C at a rate of 10°C / min, hold for 5 min to eliminate thermal history, then decrease the temperature from 200°C to -40°C at a rate of 10°C / min, and then increase the temperature to 300°C at a rate of 10°C / min. Determine whether the phenolic resin-based organic particles have a glass transition temperature T g .

[0080] The glass transition temperature T g refers to the transition temperature from the glass state to the high-elasticity state, which shows a step change on the DSC curve.

[0081] The phenolic resin-based organic particles have no glass transition temperature T g refers to the fact that the DSC curve of the phenolic resin-based organic particles does not show a step change in the range below 300°C.

[0082] The phenolic resin-based organic particles of the present disclosure are neither soluble in water nor in organic solvents such as tetrahydrofuran (THF), dichloromethane (DCM), dimethylformamide (DMF), trichlorobenzene (TCB), chloroform at 25°C, i.e., they are not soluble in the mobile phase for gel permeation chromatography testing, and the molecular weight of the phenolic resin-based organic particles cannot be tested by gel permeation chromatography.

[0083] In some embodiments, the phenolic resin-based organic particles are thermosetting resins.

[0084] In some embodiments, the phenolic resin-based organic particles are thermosetting resol resins.

[0085] In some embodiments, the phenolic resin-based organic particles have no melting point.

[0086] The phenolic resin-based organic particles have no melting point, indicating that they have good heat resistance and thermal stability, and thus can better resist thermal shrinkage of the porous base film, improve the heat resistance of the separator film, and improve the reliability of the secondary battery cell.

[0087] The melting point can be tested as follows: take an appropriate amount of sample (e.g., 5-15 mg) and place it in a differential scanning calorimeter (DSC) crucible, shake it flat, and cover it with a crucible cover; parameter settings: nitrogen atmosphere, purge gas 60 mL / min, protective gas 20 mL / min; program settings: increase the temperature from 25°C to 200°C at a rate of 10°C / min, hold for 5 min to eliminate thermal history, then decrease the temperature from 200°C to -40°C at a rate of 10°C / min, and then increase the temperature to 300°C at a rate of 10°C / min. Determine whether the phenolic resin-based organic particles have a melting point below 300°C by the DSC curve. The phenolic resin-based organic particles have no melting point, meaning that the DSC curve of the phenolic resin-based organic particles has no melting peak.

[0088] In some embodiments, the dissolution rate of the phenolic resin-based organic particles in a mixed solvent composed of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 and soaked at 60°C for 7 days can be less than or equal to 3%.

[0089] The phenolic resin-based organic particles have a low dissolution rate in organic solvents, high structural stability during long-term use of the secondary battery cell, and high chemical stability in electrolyte, thereby enabling the secondary battery cell to have longer cycle stability.

[0090] The dissolution rate of the phenolic resin-based organic particles can be tested as follows: take an appropriate amount of sample (e.g., about 1 g) and record its mass as m1, place it in a semi-permeable membrane sample bag, seal it, record the total mass of the sample bag m2, and the sample bag can permeate the solvent but not the sample; soak the sample bag in an appropriate amount of solvent (e.g., about 50 g) at 60°C for 7 days, then take out the sample bag, drain it, dry it, and weigh it again to obtain the total mass of the sample bag m3; dissolution rate = (m2-m3) / m1 x 100%. The solvent is a mixed solvent composed of ethylene carbonate (EC) and methyl ethyl carbonate (EMC) in a volume ratio of 3:7.

[0091] In some embodiments, the swelling degree of the phenolic resin-based organic particles in a mixed solvent composed of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 and soaked at 60°C for 7 days can be less than or equal to 3%.

[0092] The phenolic resin-based organic particles have a low swelling degree in organic solvents, high structural stability during long-term use of the secondary battery cell, and thus improve the problem of reduced air permeability of the separator film during use.

[0093] The swelling degree of the phenolic resin-based organic particles can be tested according to the following method: take an appropriate amount of sample (for example, about 1 g), and record the mass as m1, and place it in a semi-permeable membrane sample bag, seal the bag, and the sample bag can permeate the solvent but cannot permeate the sample; immerse the sample bag in an appropriate amount of solvent (for example, about 50 g) at 60°C for 7 days, then take out the sample bag, take out the sample from the sample bag, wipe off the excess solvent, and weigh the sample again to obtain the mass m2; the swelling degree = (m2-m1) / m1x100%. The solvent is a mixed solvent obtained by mixing ethylene carbonate (EC) and methyl ethyl carbonate (EMC) at a volume ratio of 3:7.

[0094] In some embodiments, the cyclic voltammogram of the phenolic resin-based organic particles in the first cycle has no oxidation peak in the voltage range of 2.50V to 4.40V.

[0095] The cyclic voltammogram of the phenolic resin-based organic particles in the first cycle has no oxidation peak in the voltage range of 2.50V to 4.40V, which indicates that the phenolic resin-based organic particles are stable in the voltage range of 2.50V to 4.40V. Therefore, the phenolic resin-based organic particles of the present disclosure have good electrochemical stability, can be applied in high-voltage secondary battery cells, improve the working voltage and energy density of the secondary battery cells, and also enable the secondary battery cells to have good capacity performance at high voltage.

[0096] The oxidation peak potential of the cyclic voltammogram of the phenolic resin-based organic particles can be tested according to the following method: take the phenolic resin-based organic particles, the binder polymethyl methacrylate, and the conductive agent conductive carbon black, and dissolve them in water at a solid content mass ratio of 64:7:29 to prepare a slurry, coat the slurry on an aluminum foil as a positive electrode, use a lithium foil as a negative electrode, and assemble a coin cell. Perform cyclic voltammetry (CV) test on the coin cell at a scan rate of 0.10mV / s, a voltage range of 2.50V-5.00V, and 3 cycles, and take the voltage corresponding to the peak point of the first cycle cyclic voltammogram as the oxidation peak potential. The electrolyte salt of the electrolyte used for testing is LiPF6, and the concentration is 1mol / L. The solvent of the electrolyte is obtained by mixing ethylene carbonate (EC) and methyl ethyl carbonate (EMC) at a volume ratio of 3:7.

[0097] In some embodiments, the phenolic resin-based organic particles can have a volume distribution particle size Dv50 in the range of 160 nm to 800 nm, for example, 160 nm, 180 nm, 200 nm, 220 nm, 240 nm, 260 nm, 280 nm, 300 nm, 320 nm, 340 nm, 360 nm, 380 nm, 400 nm, 420 nm, 440 nm, 460 nm, 480 nm, 500 nm, 520 nm, 540 nm, 560 nm, 580 nm, 600 nm, 620 nm, 640 nm, 660 nm, 680 nm, 700 nm, 720 nm, 740 nm, 760 nm, 780 nm, 800 nm, or a range defined by any two of the above values.

[0098] The volume distribution particle size Dv50 of the phenolic resin-based organic particles in the above range is conducive to the isolation film having good heat resistance and air permeability.

[0099] Dv50 represents the particle size corresponding to the cumulative volume distribution percentage of 50%, which can be tested by a laser particle size analyzer according to GB / T 19077-2016. During the test, 1 g of the sample to be tested is added to a clean small beaker, 20 ml of deionized water is added, and ultrasonic treatment is performed at 53 KHz / 120 W for 5 min to ensure that the sample is completely dispersed. After the light path system is cleaned, the background is automatically tested. The ultrasonically treated sample solution is stirred to make it uniformly dispersed, and then placed in the sample cell as required to start measuring the particle size. The testing instrument can be a MasterSizer 3000 laser particle size analyzer.

[0100] In some embodiments, the diameter of the fibrous material can be in the range of 10 nm to 200 nm.

[0101] Alternatively, the diameter of the fibrous material can be in the range of 10 nm to 160 nm, 12 nm to 160 nm, 14 nm to 160 nm, 16 nm to 160 nm, 18 nm to 160 nm, 20 nm to 160 nm, 10 nm to 120 nm, 12 nm to 120 nm, 14 nm to 120 nm, 16 nm to 120 nm, 18 nm to 120 nm, 20 nm to 120 nm, 10 nm to 100 nm, 12 nm to 100 nm, 14 nm to 100 nm, 16 nm to 100 nm, 18 nm to 100 nm, 20 nm to 100 nm, 10 nm to 80 nm, 12 nm to 80 nm, 14 nm to 80 nm, 16 nm to 80 nm, 18 nm to 80 nm, 20 nm to 80 nm, 14 nm to 50 nm, 16 nm to 50 nm, 18 nm to 50 nm, 20 nm to 50 nm.

[0102] In some embodiments, the fibrous material can have a length ranging from 0.15 pm to 30 pm.

[0103] Optionally, the fibrous material can have a length ranging from 0.3 pm to 20 pm, 0.4 pm to 20 pm, 0.5 pm to 20 pm, 0.6 pm to 20 pm, 0.8 pm to 20 pm, 0.3 pm to 15 pm, 0.4 pm to 15 pm, 0.5 pm to 15 pm, 0.6 pm to 15 pm, 0.8 pm to 15 pm, 0.3 pm to 10 pm, 0.4 pm to 10 pm, 0.5 pm to 10 pm, 0.6 pm to 10 pm, 0.8 pm to 10 pm, 0.3 pm to 8 pm, 0.4 pm to 8 pm, 0.5 pm to 8 pm, 0.6 pm to 8 pm, 0.8 pm to 8 pm, 0.3 pm to 5 pm, 0.4 pm to 5 pm, 0.5 pm to 5 pm, 0.6 pm to 5 pm, 0.8 pm to 5 pm, 0.3 pm to 4 pm, 0.4 pm to 4 pm, 0.5 pm to 4 pm, 0.6 pm to 4 pm, 0.8 pm to 4 pm.

[0104] The fibrous material can have a length ranging from 0.3 pm to 20 pm, 0.4 pm to 20 pm, 0.5 pm to 20 pm, 0.6 pm to 20 pm, 0.8 pm to 20 pm, 0.3 pm to 15 pm, 0.4 pm to 15 pm, 0.5 pm to 15 pm, 0.6 pm to 15 pm, 0.8 pm to 15 pm, 0.3 pm to 10 pm, 0.4 pm to 10 pm, 0.5 pm to 10 pm, 0.6 pm to 10 pm, 0.8 pm to 10 pm, 0.3 pm to 8 pm, 0.4 pm to 8 pm, 0.5 pm to 8 pm, 0.6 pm to 8 pm, 0.8 pm to 8 pm, 0.3 pm to 5 pm, 0.4 pm to 5 pm, 0.5 pm to 5 pm, 0.6 pm to 5 pm, 0.8 pm to 5 pm, 0.3 pm to 4 pm, 0.4 pm to 4 pm, 0.5 pm to 4 pm, 0.6 pm to 4 pm, 0.8 pm to 4 pm.

[0105] In some embodiments, the fibrous material can include one or more of sugar-based fibers, protein-based fibers, polymeric fibers, inorganic fibers.

[0106] In some embodiments, the fibrous material can include one or more of alginate fibers, nanocellulose fibers, chitosan fibers, chitin fibers, plant cellulose fibers, silk fibroin fibers, spider silk fibers, corn protein fibers, soy protein fibers, keratin fibers, wool fibers, cashmere fibers, aramid fibers, polyester fibers, polyamide fibers, polyacrylonitrile fibers, polyvinyl alcohol fibers, polyethylene fibers, ultra-high molecular weight polyethylene fibers, polypropylene fibers, polytetrafluoroethylene fibers, polyvinylidene fluoride fibers, polyurethane fibers, acetate fibers, polycaprolactone fibers, polylactic acid fibers, polyether sulfone fibers, acrylic fibers, acrylic polymer fibers, polymethyl methacrylate fibers, poly(2-hydroxyethyl methacrylate) fibers, polyethylene terephthalate fibers, polyethylene terephthalate fibers, para-phenylenediamine fibers, glass fibers, asbestos fibers, silica fibers.

[0107] Optionally, the alginate fibers can include one or more of alginate fibers, alginate salt fibers, and other chemically modified alginate derivative fibers.

[0108] Optionally, the nanocellulose and derivative fibers thereof can include one or more of nanocellulose fibers, carboxymethyl cellulose fibers, carboxyethyl cellulose fibers, sulfonated cellulose fibers, hydroxymethyl cellulose fibers, hydroxyethyl cellulose fibers, hydroxypropyl cellulose fibers, oxidized cellulose fibers, and other chemically modified cellulose derivative fibers.

[0109] Optionally, the chitosan and derivative fibers thereof can include one or more of chitosan fibers, carboxymethyl chitosan fibers, carboxyethyl chitosan fibers, hydroxypropyl chitosan fibers, hydroxyethyl chitosan fibers, sulfonated chitosan fibers, succinyl chitosan fibers, acetylated chitosan fibers, propionyl chitosan fibers, butyryl chitosan fibers, chitin fibers, and other chemically modified chitosan derivative fibers.

[0110] Optionally, the chitin and derivative fibers thereof can include one or more of chitin fibers, carboxymethyl chitin fibers, carboxyethyl chitin fibers, sulfonated chitin fibers, acetylated chitin fibers, and other chemically modified chitin derivative fibers.

[0111] Plant cellulose refers to cellulose made from plants rich in cellulose. Optionally, the plant cellulose can include one or more of bamboo cellulose, cotton cellulose, wood cellulose, herbaceous plant cellulose, sugar cane bagasse cellulose, flax cellulose.

[0112] In some embodiments, the fibrous material can have polar groups.

[0113] Optionally, the polar groups can include one or more of hydroxyl groups, carboxyl groups, ester groups, amide groups, cyano groups, amine groups, aldehyde groups, sulfonic acid groups, boronic acid groups, phosphoric acid groups.

[0114] The fibrous material has polar groups, which can produce stronger interactions with the binder in the porous coating, such as forming hydrogen bonds or ionic bonds, etc., so that the adhesion between the porous coating and the porous base membrane is stronger, thereby improving the overall structural integrity of the separator membrane and improving the heat resistance of the separator membrane.

[0115] In some embodiments, the mass content of the phenolic resin-based organic particles in the porous coating can be greater than or equal to 55% based on the total mass of the porous coating. Optionally, the mass content of the phenolic resin-based organic particles in the porous coating can be greater than or equal to 60%, greater than or equal to 65%, greater than or equal to 70%, greater than or equal to 75%, greater than or equal to 80%.

[0116] In some embodiments, the mass content of the fibrous material in the porous coating can be 0.3%-30%, for example, can be 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, or a range consisting of any of the aforementioned values, based on the total mass of the porous coating.

[0117] Optionally, the mass content of the fibrous material in the porous coating can be 1%-20%, 1%-15%, 1%-10%, 2%-20%, 2%-15%, 2%-10%, 3%-20%, 3%-15%, 3%-10%, 4%-20%, 4%-15%, 4%-10%, 5%-20%, 5%-15%, 5%-10%.

[0118] The mass content of the fibrous material in the above range can make the separator film have good heat resistance and air permeability, thereby making the secondary battery cell have high reliability and good cycle performance.

[0119] In some embodiments, the porous coating includes a binder, which can include but is not limited to one or more of polyacrylate binders, nitrile rubber binders, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0120] In some embodiments, the mass content of the binder in the porous coating can be 0.5%-10%, for example, can be 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or a range consisting of any of the aforementioned values, based on the total mass of the porous coating. Optionally, the mass content of the binder in the porous coating can be 1%-8%.

[0121] In some embodiments, the porous coating can further include a dispersant, for example, can include but is not limited to one or more of alkylphenol polyoxyethylene ethers and the like, polyacrylic acid dispersants, cellulose dispersants. As an example, the dispersant can include but is not limited to one or more of sodium carboxymethyl cellulose, sodium polyacrylate, ammonium polyacrylate.

[0122] In some embodiments, the separator film can further include polymeric binder particles.

[0123] The "polymer binder particles" improve the adhesion of the separator to the electrode sheet in the porous coating of the separator, and have substantially no high-temperature resistance.

[0124] In some embodiments, the polymer binder particles can be embedded in the phenol resin-based organic particles and the fibrous material and form protrusions on the surface of the porous coating.

[0125] In other embodiments, the porous coating of the separator includes a heat-resistant layer disposed on the porous base film and a bonding layer disposed on at least a portion of the surface of the heat-resistant layer away from the porous base film, the phenol resin-based organic particles are disposed in the heat-resistant layer, and the polymer binder particles are disposed in the bonding layer.

[0126] In yet other embodiments, the porous coating of the separator includes a heat-resistant layer disposed on one side of the porous base film and a bonding layer disposed on at least a portion of the surface of the other side of the porous base film, the phenol resin-based organic particles are disposed in the heat-resistant layer, and the polymer binder particles are disposed in the bonding layer.

[0127] In some embodiments, the average particle diameter of the polymer binder particles can be 6 μm to 18 μm.

[0128] In some embodiments, the polymer binder particles can include vinylidene fluoride-based polymer particles, such as polyvinylidene fluoride (PVDF) particles and / or copolymer particles of a vinylidene fluoride monomer and a comonomer.

[0129] The comonomer can include at least one of an olefin monomer, a fluorine-containing olefin monomer, a chlorine-containing olefin monomer, an acrylate monomer, an acrylic monomer, and a fluorine ether monomer.

[0130] Optionally, the comonomer can include at least one of trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl) ether (e.g., perfluoro(methyl vinyl) ether, perfluoro(ethyl vinyl) ether, perfluoro(propyl vinyl) ether), perfluoro(1,3-dioxolane), and perfluoro(2,2-dimethyl-1,3-dioxolane).

[0131] In some embodiments, the thickness of the porous coating can be 0.4 μm to 5 μm. The thickness of the porous coating refers to the thickness of the porous coating on one side of the porous base film. Optionally, the thickness of the porous coating can be 0.4 μm to 4 μm, 0.4 μm to 3 μm, 0.4 μm to 2 μm, 0.8 μm to 4 μm, 0.8 μm to 3 μm, 0.8 μm to 2 μm.

[0132] In some embodiments, the porous base film can comprise a film or nonwoven web selected from any one or at least two of polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyether sulfone, polyphenylene ether, cyclic olefin copolymer, polyphenylene sulfide, polyvinyl naphthalene.

[0133] The porous base film can be a single-layer film or a multi-layer composite film. When the porous base film is a multi-layer composite film, the materials of the layers can be the same or different.

[0134] In some embodiments, the thickness of the porous base film can be 4-12 μm, optionally 4-9 μm.

[0135] In some embodiments, the porosity of the porous base film can be 25-60%, optionally 28-50%.

[0136] In some embodiments, the thickness of the separator film can be 5-14 μm, optionally 5-12 μm, 6-12 μm. This is advantageous for improving the energy density of the secondary battery cell.

[0137] It should be noted that the porous coating parameters of the separator film described above are the porous coating parameters of one side of the porous base film. When the porous coating is provided on both sides of the porous base film, the porous coating parameters of any one side thereof satisfying the present disclosure are considered to fall within the protection scope of the present disclosure.

[0138] The present disclosure also provides a method for preparing a separator film, which can prepare the separator film of the present disclosure.

[0139] The method for preparing a separator film comprises the following steps: providing a porous base film; providing a slurry comprising phenolic resin-based organic particles, fibrous material, and binder; coating the slurry on at least one side of the porous base film to obtain the separator film after drying.

[0140] In some embodiments, the slurry can further comprise polymeric binder particles, and after drying of the slurry, the polymeric binder particles are embedded in the phenolic resin-based organic particles and fibrous material and form protrusions on the surface of the porous coating.

[0141] In some embodiments, the method for preparing a separator film can comprise the following steps: coating a heat-resistant layer slurry comprising phenolic resin-based organic particles and binder on at least one side of the porous base film to form a heat-resistant layer after drying; and coating an adhesive layer slurry comprising polymeric binder particles and binder on at least a part of the surface of the heat-resistant layer to obtain the separator film after drying.

[0142] In some embodiments, the method for preparing the separation film can include the steps of: applying a heat-resistant slurry including the phenolic resin-based organic particles and a binder on one side of a porous base film, and applying a bonding layer slurry including the polymeric binder particles and a binder on at least a portion of the surface of the other side of the porous base film, to obtain the separation film after drying.

[0143] In some embodiments, the solvent of the slurry can be water, such as deionized water.

[0144] In some embodiments, the slurry can further include other components, such as a dispersant and / or a wetting agent, etc. In some embodiments, the method for providing the phenolic resin-based organic particles can include the steps of: providing a resol phenolic resin-based material; curing the resol phenolic resin-based material at a first temperature and in a first atmosphere for a first time, and then curing at a second temperature and in a second atmosphere for a second time, and then crushing and grinding to obtain the phenolic resin-based organic particles, the first temperature being 90-180°C, and the second temperature being 190-290°C.

[0145] The phenolic resin-based organic particles prepared according to the present disclosure are thermosetting resol resin.

[0146] The first temperature can be 90-180°C, such as 90°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 180°C, or a range defined by any two of the aforementioned values.

[0147] The first temperature in the above range can make the curing of the resol phenolic resin-based material in the first stage more uniform and sufficient, so that the phenolic resin-based organic particles with good heat resistance can be obtained.

[0148] Alternatively, the first temperature can be 90-180°C, 100-180°C, 110-180°C, 100-165°C, 110-165°C.

[0149] The first temperature in the above range can make the curing of the resol phenolic resin-based material in the first stage more uniform and sufficient, so that the phenolic resin-based organic particles with good heat resistance can be obtained.

[0150] The second temperature can be 190-290°C, such as 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C, 225°C, 230°C, 235°C, 240°C, 245°C, 250°C, 255°C, 260°C, 265°C, 270°C, 275°C, 280°C, 285°C, 290°C, or a range defined by any two of the aforementioned values.

[0151] The second temperature is in the above range, which can make the phenolic resin organic particles more fully cured, and obtain phenolic resin organic particles with good heat resistance.

[0152] Alternatively, the second temperature can be 200-285°C, 200-280°C.

[0153] The second temperature is in the above range, which can obtain phenolic resin organic particles with better heat resistance.

[0154] In some embodiments, the first time can be 1-5h, for example, 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 a range consisting of any of the above values.

[0155] The first time is in the above range, which can make the resol resin material more uniformly and fully cured in the first stage, and thus can obtain phenolic resin organic particles with better heat resistance.

[0156] In some embodiments, the second time can be 1-6h, for example, 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, 5.2h, 5.4h, 5.6h, 5.8h, 6h, or a range consisting of any of the above values.

[0157] The second time is in the above range, which can make the phenolic resin organic particles more fully cured and have better heat resistance.

[0158] In some embodiments, the first atmosphere can be an inert gas atmosphere or an oxygen-containing atmosphere. The oxygen-containing atmosphere can include oxygen and an inert gas. Alternatively, the volume fraction of oxygen in the oxygen-containing atmosphere can be 5-50%. Alternatively, the inert gas can include, but is not limited to, one or more of nitrogen, argon, and helium.

[0159] Alternatively, the first atmosphere is an oxygen-containing atmosphere, and the volume fraction of oxygen in the oxygen-containing atmosphere can be 10-30%. More alternatively, the first atmosphere can be an air atmosphere.

[0160] In some embodiments, the second atmosphere can be an inert gas atmosphere or an oxygen-containing atmosphere. The oxygen-containing atmosphere can include oxygen and an inert gas. Alternatively, the volume fraction of oxygen in the oxygen-containing atmosphere can be 5-50%. Alternatively, the inert gas can include, but is not limited to, one or more of nitrogen, argon, and helium.

[0161] Optionally, the second atmosphere is an oxygen-containing atmosphere, and the volume fraction of oxygen in the oxygen-containing atmosphere can be 10%-30%. More optionally, the second atmosphere can be an air atmosphere.

[0162] In some embodiments, the method of providing the slurry comprising the phenolic resin-based organic particles can further comprise a step of a magnetic removal treatment after the milling treatment.

[0163] The resol resin-based material can be commercially available or synthesized according to methods known in the art. In some embodiments, the method of preparing the resol resin-based material comprises the step of reacting a phenolic compound and an aldehyde compound under catalysis of an alkaline substance to obtain the resol resin-based material.

[0164] Optionally, the alkaline substance can comprise one or more of ammonia, NaOH, Na2CO3.

[0165] Optionally, the phenolic compound can comprise one or more of phenol, p-dihydroxybenzene, m-dihydroxybenzene, o-dihydroxybenzene, cresol, cardanol.

[0166] Optionally, the aldehyde compound can comprise one or more of formaldehyde, paraformaldehyde, acetaldehyde, propyl aldehyde, n-butyl aldehyde, glyoxal, and furfural.

[0167] Embodiments of the present disclosure further provide a secondary battery cell. The secondary battery cell comprises the separator provided by the present disclosure. Thus, the secondary battery cell can have both high quality energy density and high reliability.

[0168] The secondary battery cell further comprises a positive electrode sheet, a negative electrode sheet, and an electrolyte, and the separator is disposed between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet, the separator, and the negative electrode sheet can form an electrode assembly through a rolling process and / or a stacking process.

[0169] The secondary battery cell provided by the present disclosure can include, but is not limited to, a lithium secondary battery cell, a sodium secondary battery cell, etc., and the composition of the positive electrode sheet, the negative electrode sheet, and the electrolyte can vary depending on the type of the secondary battery cell.

[0170] [Positive electrode sheet]

[0171] In some embodiments, the positive electrode sheet can comprise a positive current collector and a positive film layer disposed on at least one surface of the positive current collector and comprising a positive active material. For example, the positive current collector has two surfaces opposite in the thickness direction of the positive current collector, and the positive film layer is disposed on either one or both of the two opposite surfaces of the positive current collector.

[0172] LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi0.8Co0.2O2, LiNi0.8Mn0.2O2, LiNi0.5Co0.2Mn0.3O2, LiNi0.6Co0.2Mn0.2O2, LiNi0.5Co0.3Mn0.2O2, LiNi0.8Al0.2O2, LiFePO4, LiMnPO4, and modified compounds of each of the foregoing, and the like. In some embodiments, to further enhance the energy density of the secondary battery cell, the positive active material can include one or more of lithium transition metal oxides of the general formula Li a Ni b Co c M d O e A f and modified compounds thereof, where 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.

[0173] LiCoO2, LiNiO2, LiMnO2, LiMn2O4, 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 O2, LiFePO4, LiMnPO4, and modified compounds of each of the foregoing, and the like.

[0174] The secondary battery cell will be accompanied by Li deintercalation and consumption during charging and discharging, and the molar content of Li is different when the secondary battery cell is discharged to different states. In the disclosure, the molar content of Li in the listing of the positive electrode active material is the initial state of the material, i.e. the state before feeding, and the positive electrode active material is applied to the secondary battery cell. After charging and discharging cycles, the molar content of Li will change. In the disclosure, the molar content of O in the listing of the positive electrode active material is only the theoretical state value, and the release of oxygen from the crystal lattice will cause the molar content of O to change, and the actual molar content of O will also appear to float.

[0175] Taking a sodium battery cell as an example, the positive electrode active material can include but is not limited to one or more of sodium-containing transition metal oxides, polyanion materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and prussian blue materials. As an example, the positive electrode active material can include but is not limited to one or more of NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, 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, and materials of the general formula X p M’ q (PO4) r O x Y 3-x . In the general formula X p M’ q (PO4) r O x Y 3-x , 0 < p < 4, 0 < q < 2, 1 < r < 3, 0 < x < 2, X includes but is not limited to one or more of H + , Li + , Na + , K + and NH4 + , M' is a transition metal cation, which can optionally include but is not limited to one or more of V, Ti, Mn, Fe, Co, Ni, Cu and Zn, and Y is a halide anion, which can optionally be one or more of F, Cl and Br.

[0176] The modified compounds of the positive electrode active materials of the above lithium battery cells and sodium battery cells can be doping modification and / or surface coating modification of the positive electrode active materials.

[0177] In some embodiments, the positive electrode film layer can further include a positive electrode conductive agent. As an example, the positive electrode conductive agent can include, but is not limited to, one or more of super-P, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0178] In some embodiments, the positive electrode film layer can further include a positive electrode binder. As an example, the positive electrode binder can include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic resin.

[0179] In some embodiments, the positive electrode current collector can employ a metal foil or a composite current collector. As an example of the metal foil, an aluminum foil can be employed. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can include, but is not limited to, one or more of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy. As an example, the polymer material base layer can include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0180] The positive electrode film layer is generally formed by coating a positive electrode slurry on a positive electrode current collector, drying, and cold-pressing. The positive electrode slurry is generally formed by dispersing and uniformly stirring a positive electrode active material, a positive electrode conductive agent, a positive electrode binder, and any other components in a solvent. The solvent can be N-methyl pyrrolidone (NMP), but is not limited thereto.

[0181] [Negative electrode tab]

[0182] In some embodiments, the negative electrode tab can include a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material. For example, the negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0183] The negative electrode active material can employ a material known in the art that can be used for a secondary battery cell. As an example, the negative electrode active material can include, but is not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, a silicon-based material, a tin-based material, and lithium titanate. The silicon-based material can include, but is not limited to, one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and a silicon alloy material. The tin-based material can include, but is not limited to, one or more of elemental tin, tin oxide, and a tin alloy material.

[0184] In some embodiments, the negative electrode film layer can further include a negative electrode conductive agent. As an example, the negative electrode conductive agent can include, but is not limited to, one or more of super P, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0185] In some embodiments, the negative electrode film layer can further include a negative electrode binder. As an example, the negative electrode binder can include, but is not limited to, one or more of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethylacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0186] In some embodiments, the negative electrode film layer can further include other auxiliary agents. As an example, the other auxiliary agents can include thickening agents, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

[0187] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. As an example of the metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can include, but is not limited to, one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0188] The negative electrode film layer is typically formed by coating a negative electrode slurry on a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is typically formed by dispersing and uniformly stirring a negative electrode active material, a negative electrode conductive agent, a negative electrode binder, and other optional auxiliary agents in a solvent. The solvent can be N-methyl pyrrolidone (NMP) or deionized water, but is not limited thereto.

[0189] The negative electrode tab does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode tab further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) interposed between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector.

[0190] In some embodiments, the negative electrode tab can employ a foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, foamed carbon, or the like. When the foamed metal is used as the negative electrode tab, the surface of the foamed metal can not be provided with a negative electrode active material, and of course, can be provided with a negative electrode active material.

[0191] [Electrolyte]

[0192] The electrolyte functions to conduct ions between the positive electrode and the negative electrode.

[0193] In some embodiments, the electrolyte employs an electrolyte solution that includes an electrolyte salt and an organic solvent.

[0194] Taking a lithium battery cell as an example, the electrolyte salt can include, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalato borate (LiDFOB), lithium bisoxalato borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalato phosphate (LiDFOP), and lithium tetrafluorooxalato phosphate (LiTFOP).

[0195] Taking a sodium battery cell as an example, the electrolyte salt can include, but is not limited to, one or more of sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium bisfluorosulfonylimide (NaFSI), sodium bis-trifluoromethanesulfonylimide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalato borate (NaDFOB), sodium bisoxalato borate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluorodioxalato phosphate (NaDFOP), and sodium tetrafluorooxalato phosphate (NaTFOP).

[0196] In some embodiments, the organic solvent can include, but is not limited to, one or more of 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), butylene 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, crown ether.

[0197] In some embodiments, the electrolyte can further include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and an additive capable of improving certain performance of the secondary battery cell, such as an additive capable of improving overcharge performance, an additive capable of improving high-temperature performance, an additive capable of improving low-temperature performance, and the like.

[0198] Optionally, the additive can include one or more of fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,3-propane sultone (PS), and vinyl sulfate (DTD).

[0199] Methods for preparing secondary battery cells are known. In some embodiments, a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte can be assembled to form a secondary battery cell. As an example, a positive electrode sheet, a separator, and a negative electrode sheet can be formed into an electrode assembly through a winding process and / or a stacking process, the electrode assembly can be placed in an outer package, and the electrolyte described above can be injected after drying, followed by processes such as standing and formation, to obtain a secondary battery cell.

[0200] Embodiments

[0201] The present disclosure is described in more detail by the following embodiments, which are merely illustrative and not restrictive, as various modifications and changes in the embodiments will be obvious to those skilled in the art within the scope of the present disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used as received without further purification, and the instruments used in the examples are commercially available.

[0202] Example 1

[0203] A commercially available phenol and formaldehyde-based resol resin material was placed in a curing oven, the atmosphere was set to air, the temperature was set to 135°C, and the temperature was maintained for 3 h; after the end, the temperature of the curing oven was increased to 255°C, and the temperature was maintained for 3 h. After the end of the two curing processes, the cured resol resin material was taken out, naturally cooled in air, and then crushed, ground, and wet-magnetic removed to obtain a resol resin-based organic particle 1# slurry.

[0204] The resol resin-based organic particle 1# satisfies the following characteristics: it is a thermosetting resol resin, has no melting point below 300°C, and has no glass transition temperature Tg below 300°C. g .

[0205] The above slurry, nanocellulose fiber, binder polymethyl methacrylate and dispersant sodium carboxymethyl cellulose were stirred uniformly in deionized water to obtain a heat-resistant layer porous coating slurry. The length of the nanocellulose fiber ranges from 0.5 μm to 5 μm, and the diameter ranges from 20 nm to 50 nm. The solid content mass ratio of the phenolic resin organic particles, nanocellulose fiber, dispersant sodium carboxymethyl cellulose, and binder polymethyl methacrylate in the porous coating slurry is 88:2:2:8.

[0206] A commercially available polyethylene microporous film with a thickness of 7 μm was used as the porous base film. The porous coating slurry was coated on both surfaces of the porous base film by microgravure method, and then dried and slitted to obtain the separator.

[0207] Example 2

[0208] The preparation of the separator was the same as in Example 1, except for the following differences.

[0209] The solid content mass ratio of the phenolic resin organic particles, nanocellulose fiber, dispersant sodium carboxymethyl cellulose, and binder polymethyl methacrylate in the porous coating slurry was 86:4:2:8.

[0210] Example 3

[0211] The preparation of the separator was the same as in Example 1, except for the following differences.

[0212] The solid content mass ratio of the phenolic resin organic particles, nanocellulose fiber, dispersant sodium carboxymethyl cellulose, and binder polymethyl methacrylate in the porous coating slurry was 84:6:2:8.

[0213] Example 4

[0214] The preparation of the separator was the same as in Example 1, except for the following differences.

[0215] The solid content mass ratio of the phenolic resin organic particles, nanocellulose fiber, dispersant sodium carboxymethyl cellulose, and binder polymethyl methacrylate in the porous coating slurry was 82:8:2:8.

[0216] Comparative Example 1

[0217] A commercially available phenol and formaldehyde-based resol resin material was placed in a curing oven, the atmosphere was set to air atmosphere, the temperature was set to 135°C, and the temperature was maintained for 1 h for curing. After the curing was completed, the cured phenolic resin material was taken out, naturally cooled in air, and then crushed, ground, and wet-magnetic removed to obtain a phenolic resin organic particle D1# slurry.

[0218] The phenolic resin organic particles D1# slurry, the dispersant sodium carboxymethyl cellulose, and the binder polymethyl methacrylate were stirred and mixed uniformly in deionized water to obtain a porous coating slurry. The solid content mass ratio of the phenolic resin organic particles D1#, the dispersant sodium carboxymethyl cellulose, and the binder polymethyl methacrylate in the porous coating slurry was 90:2:8.

[0219] A commercially available polyethylene microporous film with a thickness of 7 μm was used as the porous base film. The porous coating slurry was coated on both surfaces of the porous base film by microgravure coating, and then dried and slit to obtain the separator film.

[0220] Performance test

[0221] The heat shrinkage rate of the separator film can be tested according to GB / T 36363-2018.

[0222] The separator film was punched into a sample with a width of 50 mm and a length of 100 mm by a punch press, and 5 parallel samples were placed on an A4 paper. Then the A4 paper with the samples was placed on a corrugated paper with a thickness of 1 mm to 5 mm.

[0223] The temperature of the air-blast oven was set to 140℃. After the temperature reached the set temperature and stabilized for 60 min, the A4 paper placed on the corrugated paper was placed in the air-blast oven, and the timing started. After the set time (1 h in the present disclosure) was reached, the length and width of the separator film were measured, and the values were marked as a and b, respectively.

[0224] Heat shrinkage rate calculation: longitudinal (MD) heat shrinkage rate = [(100-a) / 100] x 100%, transverse (TD) heat shrinkage rate = [(50-b) / 50] x 100%, and the average value of 3 parallel samples was taken as the test result.

[0225] Table 1

[0226] From the above test results, it can be seen that the separator film of the present disclosure has better heat resistance.

[0227] It should be noted that the present disclosure is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same technical idea and playing the same role and effect within the scope of the technical solutions of the present disclosure are all included in the technical scope of the present disclosure. In addition, within the scope of the main idea of the present disclosure, various modifications that can be thought of by those skilled in the art, and other ways constructed by combining part of the components in the embodiments are also included in the scope of the present disclosure.

Claims

1. An isolation membrane comprising a porous base film and a porous coating layer on at least one side of the porous base film, wherein, The porous coating includes phenolic resin-based organic particles and fibrous materials, and at least part of the phenolic resin-based organic particles are located between the fibrous materials.

2. The separator film according to claim 1, wherein The phenolic resin-based organic particles have no glass transition temperature below 300°C.

3. The separator film according to any one of claims 1-2, wherein, The phenolic resin-based organic particles satisfy at least one of the following conditions (1) to (2): (1) The phenolic resin-based organic particles have no melting point; (2) The phenolic resin-based organic particles are thermosetting resol.

4. The separator film according to any one of claims 1 to 3, wherein The phenolic resin-based organic particles satisfy at least one of the following conditions (1) to (3): (1) The phenolic resin-based organic particles have a dissolution rate of less than or equal to 3% when soaked in a mixed solvent composed of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 at 60°C for 7 days; (2) The phenolic resin-based organic particles have a swelling degree of less than or equal to 3% when soaked in a mixed solvent composed of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 at 60°C for 7 days; (3) The phenolic resin-based organic particles have no oxidation peak in the cyclic voltammetry curve of the first cycle in the voltage range of 2.50V to 4.40V.

5. The separator film according to any one of claims 1 to 4, wherein The volume distribution particle size Dv50 of the phenolic resin-based organic particles is 160nm-800nm; and / or The phenolic resin-based organic particles have a true density of 1.0 g / cm 3 -1.4 g / cm 3 .

6. The separator film according to any one of claims 1 to 5, wherein The diameter of the fibrous materials ranges from 10nm to 200nm; and / or The length of the fibrous materials ranges from 0.15μm to 30μm.

7. The separator film according to any one of claims 1 to 6, wherein The fibrous materials include one or more of sugar-based fibers, protein-based fibers, polymer fibers, and inorganic fibers.

8. The separator film according to claim 7, wherein The fibrous materials include one or more of alginate and derivative fibers thereof, nanocellulose and derivative fibers thereof, chitosan and derivative fibers thereof, chitin and derivative fibers thereof, plant cellulose, silk fibroin fibers, spider silk fibers, corn protein fibers, soy protein fibers, keratin fibers, wool fibers, cashmere fibers, aramid fibers, polyester fibers, polyamide fibers, polyacrylonitrile fibers, polyvinyl alcohol fibers, polyethylene fibers, ultra-high molecular weight polyethylene fibers, polypropylene fibers, polytetrafluoroethylene fibers, polyvinylidene fluoride fibers, polyurethane fibers, acetate fibers, polycaprolactone fibers, polylactic acid fibers, polyether sulfone fibers, acrylic fibers, acrylic polymer fibers, polymethyl methacrylate fibers, poly-2-hydroxyethyl methacrylate fibers, polyethylene phthalate fibers, polyethylene terephthalate fibers, poly-p-phenyleneterephthalamide fibers, glass fibers, asbestos fibers, and silica fibers.

9. The separator film according to any one of claims 1 to 8, wherein The fibrous materials have polar groups, Optionally, the polar groups include one or more of hydroxyl groups, carboxyl groups, ester groups, amide groups, cyano groups, amine groups, aldehyde groups, sulfonic acid groups, boronic acid groups, and phosphoric acid groups.

10. The separator film according to any one of claims 1 to 9, wherein The mass content of the phenolic resin-based organic particles in the porous coating is greater than or equal to 55% based on the total mass of the porous coating; and / or The mass content of the fibrous material in the porous coating is 0.3%-30% based on the total mass of the porous coating.

11. The separator film according to any one of claims 1-10, wherein, The porous coating further comprises a binder; and / or, The thickness of the porous coating is 0.4-5 pm.

12. A method for preparing the separator film according to any one of claims 1-11, comprising the steps of: providing a porous base film; providing a slurry comprising phenolic resin-based organic particles, fibrous material, and a binder; coating the slurry on at least one side of the porous base film to obtain the separator film after drying.

13. The method of claim 12, wherein, The method for providing the phenolic resin-based organic particles comprises the steps of: providing a resol resin-based material; curing the resol resin-based material at a first temperature and in a first atmosphere for a first time, and then curing at a second temperature and in a second atmosphere for a second time, and then crushing and grinding to obtain the phenolic resin-based organic particles, wherein the first temperature is 90-180°C, and the second temperature is 190-290°C.

14. The method according to claim 13, wherein, The first time is 1-5 h; and / or, The second time can be 1-6 h; and / or, The first atmosphere is an inert gas atmosphere or an oxygen-containing atmosphere, and the volume fraction of oxygen in the oxygen-containing atmosphere is 5%-50%; and / or, The second atmosphere is an inert gas atmosphere or an oxygen-containing atmosphere, and the volume fraction of oxygen in the oxygen-containing atmosphere is 5%-50%.

15. The method of any one of claims 13-14, wherein, The step of providing the resol resin-based material comprises the step of: reacting a phenolic compound and an aldehyde compound in the presence of a basic substance to obtain the resol resin-based material.

16. The method according to claim 15, wherein, The phenolic compound comprises one or more of phenol, hydroquinone, resorcinol, catechol, cresol, and cardanol; and / or, The aldehyde compound comprises one or more of formaldehyde, paraformaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, glyoxal, and furfural; and / or, The basic substance comprises one or more of ammonia, NaOH, and Na2CO3.

17. A secondary battery cell comprising a positive electrode sheet, a negative electrode sheet, and the separator film according to any one of claims 1-11, wherein the separator film is disposed between the positive electrode sheet and the negative electrode sheet.

18. A battery device comprising a plurality of the secondary battery cell according to claim 17.

19. An electric device comprising the secondary battery cell according to claim 17 or the battery device according to claim 18.

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