Isolating membrane and preparation method thereof, battery monomer, battery device and power utilization device

Abstract

The invention relates to an isolating membrane and a preparation method thereof, a battery monomer, a battery device and a power utilization device. The isolating membrane comprises a porous base membrane and a porous coating, the porous coating is located on the surface of at least one side of the porous base membrane, and the porous coating comprises ceramic particles, a first carbon material and composite hot melt adhesive particles; the composite hot melt adhesive particles comprise a second carbon material and a hot melt adhesive, and the second carbon material exists in the composite hot melt adhesive particles and is blended with the hot melt adhesive to form the composite hot melt adhesive particles. The isolating membrane provided by the embodiment of the invention can further improve the reliability of the battery monomer.

Description

Technical Field

[0001] This disclosure relates to the field of batteries, and in particular to a separator and its preparation method, a battery cell, a battery device, and an electrical device. Background Technology

[0002] Separators often use porous base films, but porous base films themselves have poor mechanical properties and are easily punctured by dendrites formed on the negative electrode. Coating at least one side of the porous base film with ceramic particles can improve the problem of the separator being easily punctured, but increasing the number of ceramic particles has limited effect on improving the reliability of the battery cell. Summary of the Invention

[0003] This disclosure provides a separator and its preparation method, a battery cell, a battery device, and an electrical device, which can further improve the reliability of the battery cell.

[0004] In a first aspect, this disclosure provides a separator membrane, which includes a porous base membrane and a porous coating. The porous coating is located on at least one side surface of the porous base membrane and includes ceramic particles, a first carbon material, and composite hot melt adhesive particles. The composite hot melt adhesive particles include a second carbon material and hot melt adhesive. The second carbon material is present in the composite hot melt adhesive particles and is blended with the hot melt adhesive to form composite hot melt adhesive particles.

[0005] The separator in this embodiment includes a porous base film and a porous coating. The porous coating is located on at least one surface of the porous base film and includes ceramic particles, a first carbon material, and composite hot melt adhesive particles. The composite hot melt adhesive particles include a second carbon material and hot melt adhesive. The second carbon material is present in the composite hot melt adhesive particles and is blended with the hot melt adhesive to form composite hot melt adhesive particles. The second carbon material penetrates through the composite hot melt adhesive particles and overlaps with the first carbon material dispersed between the ceramic particles and the composite hot melt adhesive particles. When thermal runaway occurs in a battery cell, the high thermal conductivity of the first and second carbon materials can be used to melt the hot melt adhesive, bonding the ceramic particles, the first carbon material, and the second carbon material together to form a uniformly thick inorganic film layer, thereby reducing the collapse of the separator structure and improving the reliability of the battery cell.

[0006] In some embodiments, the mass ratio of the first carbon material to the second carbon material is (0.5-5):(0.1-1.6).

[0007] By adjusting the mass ratio of the first carbon material to the second carbon material within the aforementioned range, the rate of heat transfer in the separator can be increased when thermal runaway occurs in the battery cell, further promoting the melting of the composite hot melt adhesive particles, thereby further reducing the collapse of the separator structure and improving the reliability of the battery cell.

[0008] In some embodiments, the melting range of the hot melt adhesive is 130-160°C. By setting the melting range of the hot melt adhesive particles within the above range, the adhesive can play its bonding role while triggering the thermal closure of the separator in the event of misuse of the battery cell, bonding the ceramic particles, the first carbon material, and the second carbon material together to form an inorganic film layer of uniform thickness, thereby reducing the collapse of the separator structure and improving the reliability of the battery cell.

[0009] In some embodiments, the hot melt adhesive includes one or more of polyolefin hot melt adhesives, polyester hot melt adhesives, polyurethane hot melt adhesives, and polyamide hot melt adhesives.

[0010] In some embodiments, the viscosity-average molecular weight of the hot melt adhesive is 10,000 Da to 100,000 Da.

[0011] In some embodiments, the mass ratio of the second carbon material to the hot melt adhesive in the composite hot melt adhesive particles is from 1:99 to 20:80. This allows the thermal conductivity of the second carbon material to be utilized to promote the dissolution of the hot melt adhesive in the event of thermal runaway in a battery cell, thereby further improving the reliability of the battery cell.

[0012] In some embodiments, the volumetric particle size distribution Dv50 of the ceramic particles is 500 nm-20 μm.

[0013] In some embodiments, the volumetric particle size distribution Dv50 of the composite hot melt adhesive particles is 1μm-20μm.

[0014] In some embodiments, the thickness of the porous coating is 2-20 μm.

[0015] In some embodiments, the areal density of the porous coating is 0.0006-0.004 mg / mm². 2 .

[0016] By setting the thickness and / or areal density of the porous coating within the above range, the relationship between the air permeability, mechanical properties, and heat transfer of the separator can be balanced, thereby obtaining a separator with good mechanical strength and suitable air permeability while improving the reliability of the battery cell.

[0017] In some embodiments, the ceramic particles include one or more of aluminum oxide, boehmite, silicon dioxide, kaolin, silicate, calcium carbonate, hydrotalcite, montmorillonite, titanium dioxide, zirconium dioxide, magnesium oxide, magnesium hydroxide, boron nitride, silicon nitride, aluminum nitride, titanium nitride, boron carbide, silicon carbide, and zirconium carbide.

[0018] In some embodiments, the first carbon material includes one or more of carbon nanotubes, porous carbon fibers, porous conductive carbon, sheet graphite, and graphene.

[0019] In some embodiments, the second carbon material includes one or more of carbon nanotubes, porous carbon fibers, porous conductive carbon, sheet graphite, and graphene.

[0020] In some embodiments, carbon nanotubes include single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0021] In some embodiments, the diameter of the carbon nanotubes is 6-12 nm and the length of the carbon nanotubes is 1-10 μm.

[0022] In some embodiments, the porous coating further includes a binder and / or a dispersant.

[0023] In some embodiments, the adhesive includes one or more of methylcellulose adhesives, acrylate adhesives, acrylic adhesives, and styrene-butadiene emulsion adhesives.

[0024] In some embodiments, the dispersant includes one or both of salt dispersants and amide dispersants.

[0025] In some embodiments, the air permeability of the separator is 100-450 s / 100 mL.

[0026] In some embodiments, the porous base membrane comprises one or both of polyethylene and polypropylene.

[0027] In some embodiments, the thickness of the porous base film is 7-20 μm.

[0028] In some embodiments, the average pore size of the porous base film is 30-120 nm.

[0029] In some embodiments, the porosity of the porous base membrane is 20%-55%.

[0030] This embodiment of the invention sets one or more of the thickness, average pore size, and porosity of the porous base film within the above-mentioned ranges, which allows the porous base film and the porous coating to cooperate with each other. This reduces the probability of the material in the porous coating clogging the pores of the porous base film and allows the separator to have high air permeability, thereby improving the cycle performance and charge / discharge efficiency of the battery cell while maintaining reliability.

[0031] In a second aspect, this disclosure provides a method for preparing a separator membrane, comprising: providing a mixture comprising ceramic particles, composite hot melt adhesive particles and a first carbon material; coating the mixture onto the surface of at least one side of a porous base membrane, and obtaining a separator membrane after drying; wherein the composite hot melt adhesive particles comprise a second carbon material and hot melt adhesive, the second carbon material being present in the composite hot melt adhesive particles and being blended with the hot melt adhesive to form composite hot melt adhesive particles.

[0032] In some embodiments, the preparation method further includes mixing the hot melt adhesive and the second carbon material and then granulating the mixture to obtain composite hot melt adhesive particles.

[0033] Thirdly, this disclosure provides a battery cell, which includes the separator of the first aspect of this disclosure.

[0034] Fourthly, this disclosure provides a battery device comprising a plurality of battery cells according to the third aspect of this disclosure.

[0035] Fifthly, this disclosure provides an electrical device comprising a battery cell according to claim 3 or a battery device according to claim 4. Attached Figure Description

[0036] 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.

[0037] Figure 1 This is a schematic diagram of one embodiment of the battery cell disclosed herein.

[0038] Figure 2 This is a schematic diagram of one embodiment of an electrical device that uses the battery device disclosed herein as a power source.

[0039] The accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0040] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the separator, its preparation method, 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.

[0041] 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.

[0042] 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 content of this disclosure.

[0043] 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 content of this disclosure.

[0044] 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 method may also include step (c), indicating 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.

[0045] In this disclosure, the terms "multiple" or "a variety" refer to two or more kinds.

[0046] Unless otherwise stated, the test temperature for all parameters mentioned in this disclosure is 25°C.

[0047] The battery cells mentioned in this disclosure are capable of charging and discharging independently. The battery cells may be cylindrical, cuboid, or other shapes, and this disclosure does not limit this. Figure 1 The example shown is a rectangular battery cell 5.

[0048] 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 battery cells connected in series, parallel, or mixed connections via a busbar.

[0049] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells. As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form a single module. As an example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0050] In some embodiments, the battery device may be a battery pack, which may include a housing and one or more individual battery cell assemblies housed within the housing. As an example, the individual battery cell assembly may be a battery module, which can be housed within the housing by securing the battery module to the housing. Alternatively, as an example, the individual battery cell assembly may be housed within the housing by directly securing multiple individual battery cells to the housing.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] The battery cells provided in the embodiments of this disclosure include lithium-ion battery cells, lithium metal battery cells, and negative electrode-free lithium metal battery cells, etc., and the embodiments of this disclosure are not limited to these.

[0055] A negative electrode-free lithium metal battery cell typically refers to a battery cell in which a negative electrode film layer is not actively formed on the negative electrode side during the battery cell manufacturing process. For example, a negative electrode film layer of carbonaceous active material is not formed at the negative electrode through processes such as coating or deposition during the battery cell manufacturing process. During the first charge, ions gain electrons on the negative electrode side and deposit on the surface of the negative electrode current collector to form a metallic phase. During discharge, the metal can be converted into metal ions and return to the positive electrode, achieving cyclic charging and discharging. Compared with other battery cells, a negative electrode-free lithium metal battery cell can achieve a higher energy density because it lacks a negative electrode film layer. In some embodiments, to improve the performance of the battery cell, some conventional materials that can be used as negative electrode active materials, such as carbon materials, can also be placed on the negative electrode side of the negative electrode-free lithium metal battery cell. Although these materials have a certain capacity, because their content is small and they are not used as the main negative electrode active material in the battery cell, the battery cell constructed in this way can still be regarded as a negative electrode-free lithium metal battery cell.

[0056] The CB value of a cathodeless lithium metal battery cell is typically very small; for example, in some embodiments, the CB value of a cathodeless lithium metal battery cell can be less than or equal to 0.1. The CB value is the capacity per unit area of ​​the negative electrode divided by the capacity per unit area of ​​the positive electrode in the battery cell. Because a cathodeless lithium metal battery cell contains little or no negative electrode active material, the capacity per unit area of ​​the negative electrode is small, resulting in a very small CB value, typically less than or equal to 0.1.

[0057] A single battery cell includes an electrode assembly and an electrolyte. The electrode assembly typically includes a negative electrode, a positive electrode, and a separator, with the separator disposed between the negative and positive electrodes. The electrode assembly can be a wound structure or a stacked structure; this disclosure does not limit the specific type.

[0058] In some embodiments, the electrode assembly is a wound structure. The positive electrode, the separator, and the negative electrode are wound into a wound structure.

[0059] In some embodiments, the electrode assembly has a stacked structure.

[0060] As an example, multiple positive and negative electrode sheets can be set, with multiple positive and multiple negative electrode sheets stacked alternately. As an example, multiple positive electrode sheets can be set, and negative electrode sheets are folded to form multiple stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments.

[0061] As an example, both the positive and negative electrode sheets are folded to form multiple stacked folded segments.

[0062] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0063] As an example, the separator can be continuously installed between any adjacent positive or negative electrode plates by folding or rolling.

[0064] In some embodiments, the electrode assembly may be cylindrical, flat, or polygonal, etc.

[0065] In some embodiments, the electrode assembly has tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0066] The battery cell also includes an outer packaging, which encapsulates the electrode components and electrolyte. The outer packaging can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. It can also be a flexible package, such as a pouch. The material of the flexible package can be plastic, such as one or more of aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0067] In some embodiments, the number of electrode components contained in a single battery cell can be one or more, and can be adjusted as needed.

[0068] The technical solutions described in this disclosure are applicable to various electrical devices that use battery cells or battery devices, such as, but not limited to, mobile devices (e.g., mobile phones, tablets, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc. Battery cells and battery devices are used to store or provide electrical energy.

[0069] Figure 2 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0070] Ceramic particles are coated on at least one side of the porous base film. In the event of thermal runaway of a battery cell, there is a risk that the ceramic particles may fall off the surface of the separator. In this case, the design of ceramic particles in the separator is unlikely to improve the reliability of the battery cell.

[0071] In view of this, the present disclosure provides an isolation membrane, which includes a porous base membrane and a porous coating. The porous coating is located on at least one side surface of the porous base membrane and includes ceramic particles, a first carbon material, and composite hot melt adhesive particles.

[0072] The composite hot melt adhesive particles include a second carbon material and hot melt adhesive. The second carbon material is present in the composite hot melt adhesive particles and is blended with the hot melt adhesive to form composite hot melt adhesive particles.

[0073] It should be noted that in this embodiment, the second carbon material exists in the composite hot melt adhesive particles, and the first carbon material is dispersed between the ceramic particles and the composite hot melt adhesive particles. The first carbon material and the second carbon material can contact each other, thereby improving the heat transfer rate in the porous coating.

[0074] The pore structure in the porous coating can include the pore structure formed by the stacking of ceramic particles, the first carbon material and the composite hot melt adhesive particles, or the pore structure inherent in the first carbon material and the second carbon material themselves.

[0075] The separator in this embodiment includes a porous base film and a porous coating. The porous coating is located on at least one surface of the porous base film and includes ceramic particles, a first carbon material, and composite hot melt adhesive particles. The composite hot melt adhesive particles include a second carbon material and hot melt adhesive. The second carbon material is present in the composite hot melt adhesive particles and is blended with the hot melt adhesive to form composite hot melt adhesive particles. The second carbon material penetrates through the composite hot melt adhesive particles and overlaps with the first carbon material dispersed between the ceramic particles and the composite hot melt adhesive particles. When thermal runaway occurs in a battery cell, the high thermal conductivity of the first and second carbon materials can be used to melt the hot melt adhesive, bonding the ceramic particles, the first carbon material, and the second carbon material together to form a uniformly thick inorganic film layer, thereby reducing the collapse of the separator structure and improving the reliability of the battery cell.

[0076] In some embodiments, the mass ratio of the first carbon material to the second carbon material can be (0.5-5):(0.1-1.6).

[0077] By adjusting the mass ratio of the first carbon material to the second carbon material within the aforementioned range, the rate of heat transfer in the separator can be increased when thermal runaway occurs in the battery cell, further promoting the melting of the composite hot melt adhesive particles, thereby further reducing the collapse of the separator structure and improving the reliability of the battery cell.

[0078] In some embodiments, the mass ratio of the first carbon material to the second carbon material can be 1:(0.8-3), for example, 1:0.8, 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, or 1:3.

[0079] This allows for a further increase in the heat transfer rate within the separator when thermal runaway occurs in a single battery cell. This, in turn, promotes the melting of the composite hot melt adhesive particles, promptly bonding the ceramic particles, the first carbon material, and the second carbon material together to form a uniformly thick inorganic film layer. This reduces the collapse of the separator structure and improves the reliability of the single battery cell.

[0080] In some embodiments, the melting range of the hot melt adhesive can be 130-160°C, for example, 140-160°C, 150-160°C, 130-150°C, or 130-140°C.

[0081] The melting range of a hot melt adhesive refers to the temperature range between the temperature at which it begins to melt and the temperature at which it completely melts. It can be determined as follows: Take a small, representative sample from the plastic material being tested, ensuring the sample is dry, clean, and free of obvious defects. Cut the sample into small pieces or grind it into powder if necessary. Place the prepared sample into the sample chamber of the melting point apparatus, ensuring good contact between the sample and the temperature sensor. Set the heating rate to 10℃ / min. Start the melting point apparatus and heat according to the set parameters. During heating, closely monitor temperature changes and the melting behavior of the sample. When the sample begins to melt, record the temperature at which it begins to melt as the initial melting point. As the temperature continues to rise, record the temperature at which the sample completely melts as the final melting point. Melting range = Final melting point - Initial melting point.

[0082] The melting range of the hot melt adhesive particles is comparable to the pore-closing temperature of the porous base film. By setting the melting range of the hot melt adhesive particles within the above range, the hot melt adhesive can play its adhesive role while triggering the thermal closure of the separator in the event of abuse of the battery cell. This binds the ceramic particles, the first carbon material, and the second carbon material together to form an inorganic film layer of uniform thickness, thereby reducing the collapse of the separator structure and improving the reliability of the battery cell.

[0083] In some embodiments, the hot melt adhesive may include one or more of polyolefin hot melt adhesives, polyester hot melt adhesives, polyurethane hot melt adhesives, and polyamide hot melt adhesives. For example, the hot melt adhesive may include polyurethane and ethylene vinyl acetate copolymer.

[0084] In some embodiments, the viscosity-average molecular weight of the hot melt adhesive can be 10,000 Da-100,000 Da, 10,000 Da, 20,000 Da, 30,000 Da, 40,000 Da, 50,000 Da, 60,000 Da, 70,000 Da, 80,000 Da, 90,000 Da, or 100,000 Da.

[0085] Viscosity-average molecular weight (VMI) refers to the molecular weight at which viscosity averages. It can be measured as follows: Accurately weigh 0.20-0.25 g of sample and add it to a 25 mL volumetric flask. Add toluene to completely dissolve the sample. Place the flask in a preheated water bath. Once the desired temperature is reached, add toluene to the mark. Filter the solution through a dry No. 2 sand core funnel into a 50 mL ground glass conical flask and place it in a water bath for incubation. Vertically place the Ubbelohde viscometer in the incubator, ensuring the water surface completely submerges bulb D. Using a dry pipette, draw 10.0 mL of the prepared solution and inject it into bulb G through tube A. After incubating at 25 ± 1 °C, seal tube B. Use a syringe to draw the solution up to line a along tube C. Open tube B to allow the solution to flow down. Use a stopwatch to measure the time it takes for the liquid to flow between lines a and b. Repeat this process three times. The time error should be within 0.2 s. Take the average value as the solution outflow time. Take 2 mL, 2 mL, 4 mL, and 4 mL of constant-temperature pure toluene, respectively, and inject them into the viscometer. Mix thoroughly and measure the outflow time as described above. Calculate the intrinsic viscosity η by plotting the results. Alternatively, refer to a table based on the sample-solvent system and use the Mark-Hov-Wink empirical equation: η = kM α Calculate the viscosity-average molecular weight.

[0086] In some embodiments, the mass ratio of the second carbon material to the hot melt adhesive in the composite hot melt adhesive particles can be from 1:99 to 20:80, for example, 1:99, 2:98, 3:97, 4:96, 5:95, 6:94, 7:93, 8:92, 9:91, 10:90, 12:88, 14:86, 16:84, 18:82, 20:80.

[0087] By adjusting the mass ratio of the second carbon material to the hot melt adhesive within the above range, the thermal conductivity of the second carbon material can be used to promote the dissolution of the hot melt adhesive in a timely manner when thermal runaway occurs in the battery cell, thereby further improving the reliability of the battery cell.

[0088] In some embodiments, the volumetric particle size distribution Dv50 of the ceramic particles can be 500 nm-20 μm.

[0089] In some embodiments, the volumetric particle size distribution Dv50 of the composite hot melt adhesive particles can be 1μm-20μm.

[0090] In this embodiment, the volumetric particle size distribution Dv50 of the ceramic particles is comparable to that of the volumetric particle size distribution Dv50 of the composite hot melt adhesive particles, thereby making the thickness distribution of the porous coating more uniform.

[0091] The volumetric particle size distribution (Dv50) of ceramic particles or composite hot melt adhesive particles can be determined using a laser particle size analyzer (such as the Malvern Mastersizer 3000) in accordance with GB / T19077-2016. The physical definition of Dv50 is the particle size corresponding to a cumulative volumetric distribution percentage of 50% for the material.

[0092] In some embodiments, the thickness of the porous coating can be 2-20 μm, for example, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, or 20 μm.

[0093] In some embodiments, the areal density of the porous coating can be 0.0006-0.004 mg / mm². 2 0.0006 mg / mm 2 0.0008 mg / mm 2 0.001 mg / mm 2 0.002 mg / mm 2 0.003 mg / mm 2 0.004 mg / mm 2 .

[0094] By setting the thickness and / or areal density of the porous coating within the above range, the relationship between the air permeability, mechanical properties, and heat transfer of the separator can be balanced, thereby obtaining a separator with good mechanical strength and suitable air permeability while improving the reliability of the battery cell.

[0095] In some embodiments, the ceramic particles may include one or more of the following: aluminum oxide, boehmite, silicon dioxide, kaolin, silicate, calcium carbonate, hydrotalcite, montmorillonite, titanium dioxide, zirconium dioxide, magnesium oxide, magnesium hydroxide, boron nitride, silicon nitride, aluminum nitride, titanium nitride, boron carbide, silicon carbide, and zirconium carbide.

[0096] In some embodiments, the first carbon material may include one or more of carbon nanotubes, porous carbon fibers, porous conductive carbon, sheet graphite, and graphene.

[0097] In some embodiments, the second carbon material may include one or more of carbon nanotubes, porous carbon fibers, porous conductive carbon, and sheet graphite and graphene.

[0098] In the embodiments of this disclosure, the first carbon material and the second carbon material can be the same or different.

[0099] The first and second carbon materials contain delocalized π bonds, and their thermal conductivity is typically 1000-4000 W / (m·K), while the thermal conductivity of ceramic particles is only 30-42 W / (m·K). This means that the thermal conductivity of both the first and second carbon materials is significantly higher than that of the ceramic particles. In this embodiment, the first carbon material is incorporated into a porous coating to form a network structure. When thermal runaway occurs in a single battery cell, heat can be rapidly transferred to the porous base film, triggering timely thermal closure of the base film, reducing the probability of more severe thermal runaway, and improving the reliability of the battery cell.

[0100] In some embodiments, the first carbon material may be one or more of carbon nanotubes, porous carbon fibers, and porous conductive carbon, and the second carbon material may be one or two of sheet graphite and graphene.

[0101] By selecting the combination of the first and second carbon materials mentioned above, a three-dimensional structure of sheet-like and linear carbon materials can be formed in the porous coating, which further enhances the heat transfer rate in the porous coating when thermal runaway occurs in the battery cell.

[0102] In some embodiments, carbon nanotubes may include single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0103] The separator in this embodiment can further utilize the porosity of the first and second carbon materials to increase the migration channels of lithium ions in the porous coating. Furthermore, the first carbon material forms a network structure in which the electrolyte can freely traverse, improving the permeability of the separator and thus enhancing the kinetic performance of the battery cell.

[0104] In some embodiments, the diameter of the carbon nanotubes is 6-12 nm and the length of the carbon nanotubes is 1-10 μm.

[0105] By selecting carbon nanotubes with the aforementioned diameter and length, the dispersion of carbon nanotubes and their thermal conductivity can be improved.

[0106] In some embodiments, the porous coating may also include a binder and / or a dispersant.

[0107] In some embodiments, the adhesive may include one or more of methylcellulose adhesives, acrylate adhesives, acrylic adhesives, and styrene-butadiene emulsion adhesives.

[0108] In some embodiments, the adhesive may include one or more of sodium carboxymethyl cellulose (CMC), polyacrylic acid emulsion, polyacrylate copolymer emulsion, polyvinyl alcohol solution, and styrene-butadiene rubber emulsion.

[0109] In some embodiments, the dispersant may include one or both of salt dispersants and amide dispersants.

[0110] In some embodiments, the dispersant may include one or more of sodium dodecylbenzenesulfonate, sodium hexametaphosphate, sodium pyrophosphate, sodium polyacrylate, potassium polyacrylate, and polyamide dispersants.

[0111] In some embodiments, based on the total mass of the porous coating, the mass content of the binder can be 2%-15% and the mass content of the dispersant can be 0.5%-5%.

[0112] In some embodiments, the air permeability of the separator membrane can be 100-450 s / 100 mL.

[0113] The air permeability of a separator membrane refers to the time required for 100 mL of gas to pass through a certain area of ​​the separator membrane. Air permeability can be tested using instruments and methods known in the art, such as GB / T36363-2018. An exemplary test method is as follows: Take three separator membranes at different locations, cut them into 5 cm × 5 cm samples, and use an air permeability meter to test the permeability of 100 mL of gas at a pressure of 1.22 kPa, measuring 6.45 cm. 2 The time required for the isolation membrane to achieve its air permeability is determined.

[0114] In some embodiments, the porous base membrane may include one or both of polyethylene and polypropylene.

[0115] By selecting the aforementioned porous base membrane, the mechanical strength and thermal stability of the separator can be improved.

[0116] In some embodiments, the thickness of the porous base film can be 7-20 μm.

[0117] In some embodiments, the average pore size of the porous base film can be 30-120 nm.

[0118] In some embodiments, the porosity of the porous base membrane can be 20%-55%.

[0119] This embodiment of the invention sets one or more of the thickness, average pore size, and porosity of the porous base film within the above-mentioned ranges, which allows the porous base film and the porous coating to cooperate with each other. This reduces the probability of the material in the porous coating clogging the pores of the porous base film and allows the separator to have high air permeability, thereby improving the cycle performance and charge / discharge efficiency of the battery cell while maintaining reliability.

[0120] [Preparation method of the separating membrane]

[0121] A method for preparing a separating membrane, comprising:

[0122] A mixture comprising ceramic particles, composite hot melt adhesive particles, and a first carbon material is provided;

[0123] The mixture is coated on at least one side of the surface of a porous base membrane and dried to obtain a separating membrane;

[0124] The composite hot melt adhesive particles include a second carbon material and hot melt adhesive. The second carbon material is present in the composite hot melt adhesive particles and is blended with the hot melt adhesive to form composite hot melt adhesive particles.

[0125] In the embodiments of this disclosure, the composite hot melt adhesive particles exist in the form of particles during the normal use of the battery cell, thereby not further reducing the air permeability of the separator.

[0126] In some embodiments, the step of providing a mixture comprising ceramic particles, composite hot melt adhesive particles, and a first carbon material may include a solvent in the mixture. For example, the solvent may be water.

[0127] In some embodiments, the preparation method may further include mixing hot melt adhesive and a second carbon material and then granulating the mixture to obtain composite hot melt adhesive particles.

[0128] In some embodiments, the mixture of hot melt adhesive and second carbon material may be heated during the granulation process. Exemplarily, the heating temperature may be 150-170°C.

[0129] In some embodiments, the mixture of hot melt adhesive and second carbon material may also be stirred during the granulation process. For example, the stirring time may be 5-10 minutes, and the stirring speed may be 50-500 rpm.

[0130] In some embodiments, the second carbon material and the first carbon material may be blended before granulation. Exemplarily, the blending speed is 60-80 rpm, and the blending time is 2-4 hours.

[0131] [Positive electrode plate]

[0132] The structure and composition of the positive electrode can be selected according to the type of battery cell, and the embodiments disclosed herein are not limited in this regard.

[0133] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer comprising a positive 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.

[0134] In some embodiments, the positive current collector may be a metal foil or a composite current collector. The metal foil may be a pure metal, an alloy, or a surface-treated metal; for example, aluminum foil may be used. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. For 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. For example, the polymer substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene.

[0135] In some embodiments, the positive electrode active material includes a material capable of extracting and inserting lithium. Optionally, 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, one or more of 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.

[0136] In some embodiments, to further improve the energy density of a single battery cell, the positive electrode active material may include materials of the general formula Li. a Ni b Co c M d O e 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 may include one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A may include one or more of N, F, S and Cl.

[0137] 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 (abbreviated as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (abbreviated as NCM523), LiNi0.5 Co 0.25 Mn 0.25 O2 (abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NCM811), LiNi 0.83 Mn 0.08 Co 0.07 O2 (abbreviated as Ni83), LiNi 0.90 Mn 0.05 Co 0.05 O2 (abbreviated as Ni90), LiNi 0.94 Mn 0.03 Co 0.03 O2 (abbreviated as Ni94), LiNi 0.96 Co 0.02 Mn 0.02 O2 (abbreviated as Ni96), LiNi 0.80 Co 0.15 Al 0.05 One or more of O2, LiFePO4, LiMnPO4 and their respective modified compounds.

[0138] During the charging and discharging process, lithium (Li) undergoes insertion / extraction and consumption within a single 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 material addition. As the positive electrode active material is applied to the 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. Oxygen release from the crystal lattice causes changes in the molar O content, leading to fluctuations in the actual molar O content.

[0139] The modified compounds for the above-mentioned positive electrode active materials can be obtained by doping and / or surface coating of the positive electrode active materials.

[0140] 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, at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0141] In some embodiments, the positive electrode film may further include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0142] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, positive conductive agent, positive binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0143] [Negative electrode plate]

[0144] The structure and composition of the negative electrode can be selected according to the type of battery cell, and the embodiments disclosed herein are not limited in this regard.

[0145] 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.

[0146] The negative electrode active material can be any negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, mesophase microcarbon spheres, silicon-based materials, and tin-based materials. Silicon-based materials may include at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include at least one of elemental tin, tin oxides, and tin alloys. However, this disclosure is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for battery cells may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0147] 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.

[0148] 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).

[0149] 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.

[0150] 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.

[0151] 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 may also include a conductive undercoat layer (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector; in some embodiments, the negative electrode sheet may also include a protective layer covering the surface of the negative electrode film layer.

[0152] In some embodiments, the negative electrode sheet may include a negative current collector and a metal layer disposed on at least one surface of the negative current collector, wherein the metal material in the metal layer may include one or more of elemental lithium and lithium alloy.

[0153] Lithium alloys can be alloys formed from metallic lithium with other metallic or non-metallic elements. For example, other metallic elements in lithium alloys may include one or more of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, and platinum, while non-metallic elements may include one or more of boron, carbon, and silicon.

[0154] In some embodiments, the negative electrode may be a lithium sheet (foil) or a lithium alloy sheet (foil).

[0155] In some embodiments, the negative electrode may include a negative current collector but not a metal layer, thereby assembling a negative electrode-free lithium metal battery cell. During the charge-discharge cycle of the negative electrode-free lithium metal battery cell, lithium from the positive electrode will be deposited and stripped off as lithium metal on the negative electrode side.

[0156] In some embodiments, the negative electrode current collector may include a metal foil, a conductive polymer material, a carbon material, or a composite current collector. Examples of metal foils include pure metals, alloys, and surface-treated metals, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer substrate and a metal material layer formed on at least one surface of the polymer substrate. Examples of metal materials include, but are not limited to, one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, aluminum, aluminum alloys, silver, and silver alloys. Examples of polymer materials include, but are not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE). The composite current collector can be formed by forming a metal material on a polymer substrate.

[0157] 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, or foamed carbon, etc. When foamed metal is used as the negative electrode sheet, the surface of the foamed metal may or may not have a negative electrode active material.

[0158] As an example, negative electrode active materials can be filled or / and deposited within the negative electrode current collector.

[0159] In some embodiments, a separator is disposed between the positive and negative electrodes.

[0160] [Electrolytes]

[0161] Each battery cell includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. This disclosure does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte may include one or more of solid electrolytes, gel electrolytes, and liquid electrolytes (i.e., electrolyte solutions).

[0162] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0163] The type of electrolyte salt is not specifically limited and can be selected according to actual needs. In some embodiments, as an example, the electrolyte salt may include, but is not limited to, one or more of 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).

[0164] There are no specific restrictions on the type of solvent; it can be selected according to actual needs.

[0165] In some embodiments, the solvent may include at least one selected from ethylene carbonate, propylene carbonate (PPC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE). An ether solvent may also be selected. Ether solvents may include one or more of the following: ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether, and crown ether.

[0166] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of the battery cell, such as additives that improve the overcharge / fast charge performance of the battery cell, additives that improve the high-temperature performance of the battery cell, additives that improve the low-temperature performance of the battery cell, etc.

[0167] The gel electrolyte includes a polymer as a backbone network and can be used in conjunction with an ionic liquid-lithium salt.

[0168] Solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0169] As an example, the polymers of polymeric solid electrolytes may include polyethers (polyoxyethylene), polysiloxanes, polycarbonates, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquids, cellulose, etc.

[0170] As an example, inorganic solid electrolytes can be one or more of the following: oxide solid electrolytes (crystalline perovskite, lithium superconducting ion conductors, garnet, amorphous LiPON thin films), sulfide solid electrolytes (crystalline lithium superconducting ion conductors, amorphous sulfides), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0171] As an example, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to polymer solid electrolytes.

[0172] Methods for preparing 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 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 placed in an outer packaging, dried, and then injected with the electrolyte. After vacuum sealing, settling, and formation processes, a battery cell is obtained.

[0173] Example

[0174] The following examples describe the contents of this disclosure in more detail. These examples 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 examples are based on mass, and all reagents used in the examples are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0175] Example 1

[0176] Preparation of the separating membrane:

[0177] The second carbon material, flake graphite, was mixed with hot melt adhesive ethylene vinyl acetate copolymer (EVA) at a mass ratio of 15:85 and then granulated by a granulator to obtain composite hot melt adhesive particles with a volume particle size distribution Dv50 of 1.43 μm.

[0178] Alumina ceramic particles, EVA composite hot melt adhesive particles containing flake graphite, sodium dodecylbenzenesulfonate dispersant, sodium carboxymethyl cellulose (CMC) binder, carbon nanotubes (the first carbon material), and deionized water were mixed in a mass ratio of 27.2:6.8:1:5:1:59. This mixture was added to a mixing tank and stirred to obtain a uniformly dispersed slurry. The slurry was then coated onto both surfaces of a commercially available porous polyethylene (PE) film with a thickness of 7 μm and an average pore size of 80 nm. The areal density of the porous coating was 0.0011 mg / mm². 2 After drying, the film is rolled up and then cut for later use.

[0179] Preparation of the positive electrode sheet:

[0180] A positive electrode slurry was prepared by thoroughly mixing polyvinylidene fluoride (PVDF), lithium iron phosphate (LFP), conductive agent carbon black, and N-methylpyrrolidone (NMP) at a mass ratio of 1.4:62.56:0.65:35.39. The positive electrode slurry was then subjected to a 210 g / m³ concentration. 2 The loading is uniformly coated on the positive current collector aluminum foil, and then dried, cold-pressed and cut to obtain the positive electrode sheet.

[0181] Preparation of negative electrode sheet:

[0182] Natural graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) were added to deionized water at a mass ratio of 96.5:1.2:0.8:1.5 and thoroughly mixed to prepare a negative electrode slurry (solid content 64%). This negative electrode slurry was then subjected to a 100 g / m³... 2 The loading amount is coated on the negative electrode current collector copper foil, and then dried, cold pressed and slit to obtain the negative electrode sheet.

[0183] Electrolyte preparation:

[0184] In a drying room at 25°C, ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain a mixed solvent. LiPF6 was then dissolved in the mixed solvent to obtain an electrolyte, wherein the concentration of LiPF6 was 1 mol / L.

[0185] The positive electrode sheet, separator, and negative electrode sheet are stacked, wound, and hot-pressed in sequence to obtain a battery cell. The battery cell is placed in an outer packaging, the prepared electrolyte is added, and after processes such as encapsulation, settling, formation, and aging, a single battery cell is obtained.

[0186] Example 2

[0187] Except that the hot melt adhesive in the composite hot melt adhesive particles is polyurethane, the preparation method of the battery cell is the same as in Example 1.

[0188] Example 3

[0189] Except that the second carbon material in the composite hot melt adhesive particles is graphene, the preparation method of the battery cell is the same as in Example 1.

[0190] Example 4

[0191] Except that the first carbon material is porous carbon fiber, the preparation method of the battery cell is the same as in Example 1.

[0192] Example 5

[0193] Except that the mass ratio of the first carbon material to the second carbon material is 1:0.816, the total mass of the first carbon material and the second carbon material in the porous coating is the same as in Example 1. The preparation method of the battery cell is the same as in Example 1.

[0194] Example 6

[0195] Except that the mass ratio of the first carbon material to the second carbon material is 1:1.224, the total mass of the first carbon material and the second carbon material in the porous coating is the same as in Example 1. The preparation method of the battery cell is the same as in Example 1.

[0196] Example 7

[0197] Except that the mass ratio of the first carbon material to the second carbon material is 1:0.6, the total mass of the first carbon material and the second carbon material in the porous coating is the same as in Example 1. The preparation method of the battery cell is the same as in Example 1.

[0198] Example 8

[0199] Except that the mass ratio of the first carbon material to the second carbon material is 1:0.428, the total mass of the first carbon material and the second carbon material in the porous coating is the same as in Example 1. The preparation method of the battery cell is the same as in Example 1.

[0200] Comparative Example 1

[0201] Except that the porous coating does not contain composite hot melt adhesive particles, the preparation method of the battery cell is the same as in Example 1.

[0202] Comparative Example 2

[0203] Except that the porous coating does not contain the first carbon material, the preparation method of the battery cell is the same as in Example 1.

[0204] Comparative Example 3

[0205] Except that the composite hot melt adhesive particles do not contain a second carbon material, the preparation method of the battery cell is the same as in Example 1.

[0206] Test section

[0207] (1) Cyclic capacity retention

[0208] At 25℃, a single battery cell is charged at a constant current of 1 / 3C to 3.8V, then charged at a constant voltage of 3.8V to a current of 0.05C, left to rest for 5 minutes, and then discharged at 1 / 3C to 2.0V. The resulting discharge capacity is recorded as the initial capacity C0. The above steps are repeated for the same battery cell, and the discharge capacity Cn of the battery after the nth cycle is recorded. The capacity retention rate of the battery cell after each cycle is Pn = (Cn / C0) × 100%. The difference in cycle performance can be reflected by the capacity retention rate of the battery after 500 cycles.

[0209] (2) Air permeability of the separator

[0210] Air permeability was tested according to GB / T36363-2018. Three separator membranes at different locations were taken, and each membrane was cut into 5cm × 5cm samples. Using an air permeability meter, under a pressure of 1.22kPa, the test showed that 100mL of gas passed through 6.45cm. 2 The time required for the isolation membrane to achieve its air permeability is determined.

[0211] (3) Thermal runaway test

[0212] Place the battery cells in an oven, heat the oven to 160°C at a rate of 10°C / min, and maintain the temperature at 160°C for 30 minutes. Observe whether the battery cells catch fire or explode.

[0213] (4) Test of membrane collapse

[0214] Cut a sample of the separator membrane to a size of 3.6cm × 3.6cm, fix one side of the separator membrane to a glass plate, place the glass plate at a 30-degree angle into the heating device, set the heating rate to 10℃ / min, heat to 160℃, and then take it out to observe the shape change of the separator membrane.

[0215] The test results of Examples 1-8 and Comparative Examples 1-3 are shown in Table 1.

[0216] Table 1

[0217]

[0218] As can be seen from the test results of the embodiments and comparative examples, the separator of the present disclosure embodiments can enable the battery cell to have a good cycle capacity retention rate, reduce the occurrence of battery cell explosion and fire during thermal runaway test, and reduce the temperature of the battery cell when the separator thermally closes, thereby further improving the reliability of the battery cell.

[0219] 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 structure and effect as the technical concept within the scope of this disclosure are included within 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 within the scope of this disclosure without departing from the spirit of this disclosure.

Claims

1. A separating membrane, characterized in that, The isolation membrane includes a porous base membrane and a porous coating. The porous coating is located on at least one surface of the porous base membrane and includes ceramic particles, a first carbon material, and composite hot melt adhesive particles. The composite hot melt adhesive particles include a second carbon material and hot melt adhesive, wherein the second carbon material is present in the composite hot melt adhesive particles and is formed by blending with the hot melt adhesive to form the composite hot melt adhesive particles.

2. The separator membrane according to claim 1, characterized in that, The mass ratio of the first carbon material to the second carbon material is (0.5-5):(0.1-1.6).

3. The separator according to claim 1 or 2, characterized in that, The hot melt adhesive has a melting range of 130-160℃.

4. The separator according to any one of claims 1-3, characterized in that, The hot melt adhesive includes one or more of polyolefin hot melt adhesives, polyester hot melt adhesives, polyurethane hot melt adhesives, and polyamide hot melt adhesives; and / or, The viscosity-average molecular weight of the hot melt adhesive is 10,000 Da to 100,000 Da.

5. The separator according to any one of claims 1-4, characterized in that, In the composite hot melt adhesive particles, the mass ratio of the second carbon material to the hot melt adhesive is 1:99 to 20:

80.

6. The separator according to any one of claims 1-5, characterized in that, The volumetric particle size distribution Dv50 of the ceramic particles is 500 nm-20 μm; and / or, The volumetric particle size distribution Dv50 of the composite hot melt adhesive particles is 1μm-20μm.

7. The separator according to any one of claims 1-6, characterized in that, The thickness of the porous coating is 2-20 μm; and / or, The areal density of the porous coating is 0.0006-0.004 mg / mm². 2 .

8. The separator according to any one of claims 1-7, characterized in that, The ceramic particles include one or more of the following: aluminum oxide, boehmite, silicon dioxide, kaolin, silicate, calcium carbonate, hydrotalcite, montmorillonite, titanium dioxide, zirconium dioxide, magnesium oxide, magnesium hydroxide, boron nitride, silicon nitride, aluminum nitride, titanium nitride, boron carbide, silicon carbide, and zirconium carbide.

9. The separator according to any one of claims 1-8, characterized in that, The first carbon material includes one or more of carbon nanotubes, porous carbon fibers, porous conductive carbon, sheet graphite, and graphene; and / or, The second carbon material includes one or more of carbon nanotubes, porous carbon fibers, porous conductive carbon, sheet graphite, and graphene. Optionally, the carbon nanotubes include single-walled carbon nanotubes and multi-walled carbon nanotubes; Optionally, the carbon nanotube has a diameter of 6-12 nm and a length of 1-10 μm.

10. The separator according to any one of claims 1-9, characterized in that, The porous coating also includes a binder and / or a dispersant; Optionally, the adhesive includes one or more of methylcellulose adhesives, acrylate adhesives, acrylic adhesives, and styrene-butadiene emulsion adhesives; Optionally, the dispersant includes one or both of salt dispersants and amide dispersants.

11. The separator according to any one of claims 1-10, characterized in that, The isolation membrane satisfies one or more of the following conditions (1)-(5): (1) The air permeability of the isolation membrane is 100-450s / 100mL; (2) The porous base membrane includes one or both of polyethylene and polypropylene; (3) The thickness of the porous base film is 7-20 μm; (4) The average pore size of the porous base film is 30-120 nm; (5) The porosity of the porous base membrane is 20%-55%.

12. A method for preparing a separating membrane, comprising: A mixture comprising ceramic particles, composite hot melt adhesive particles, and a first carbon material is provided; The mixture is coated on at least one side of a porous base membrane and dried to obtain the isolation membrane. The composite hot melt adhesive particles include a second carbon material and hot melt adhesive, wherein the second carbon material is present in the composite hot melt adhesive particles and is formed by blending with the hot melt adhesive to form the composite hot melt adhesive particles.

13. The preparation method according to claim 12, characterized in that, The preparation method further includes mixing the hot melt adhesive and the second carbon material and then granulating the mixture to obtain the composite hot melt adhesive particles.

14. A single battery cell, characterized in that, The battery cell includes the separator as described in any one of claims 1-11.

15. A battery device, characterized in that, It includes multiple battery cells as described in claim 14.

16. An electrical appliance, characterized in that, Includes the battery cell of claim 14 or the battery device of claim 15.

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