A large-particle adhesive for a separator, a separator coating slurry, a separator, and a battery

Abstract

The present application provides a kind of big granule glue for diaphragm, diaphragm coating slurry, diaphragm and battery, the big granule glue is copolymer, the copolymer includes: aromatic ethylene structural unit;Acrylate structural unit;Crosslinking structural unit, the side chain of the crosslinking structural unit contains reactive functional group, the reactive functional group includes one or more of epoxy group, isocyanate group, siloxane group, hydroxyl group, amino group, carboxyl group and unsaturated hydrocarbon group;And acrylamide structural unit, the acrylamide structural unit contains imidazolidinone group, to overcome the problem that existing ceramic diaphragm exists high battery impedance and insufficient rate performance.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to a large-particle adhesive for separators, a separator coating slurry, a separator, and a battery. Background Technology

[0002] Lithium-ion batteries, sodium-ion batteries, and other energy storage devices are widely used in new energy vehicles, consumer electronics, and energy storage power stations due to their advantages such as high energy density and long cycle life. As one of the core components of energy storage devices, the battery separator's core function is to physically isolate the positive and negative electrodes, preventing direct contact and short circuits. Simultaneously, it must ensure the smooth migration of ions in the electrolyte. Its performance directly determines the battery's safety performance, cycle stability, and rate capability.

[0003] Existing commercial battery separators mainly use polyolefins (such as polyethylene PE and polypropylene PP) as the substrate. These separators have the characteristics of uniform pore size, high ion conduction efficiency, and low cost, but they have significant thermal stability defects: when the battery is under abnormal charging and discharging, external short circuit, or high temperature environment, the polyolefin substrate is prone to thermal shrinkage (usually significant shrinkage occurs at 80-150℃), which leads to the closure of the separator pore size or even structural damage. This makes it impossible to effectively isolate the positive and negative electrodes, which in turn causes direct contact short circuit between the positive and negative electrodes. In severe cases, it may lead to battery thermal runaway, fire and explosion and other safety accidents, becoming a key bottleneck restricting the high temperature safety performance of energy storage devices.

[0004] To address the thermal shrinkage issue of polyolefin separators, existing technologies widely employ a modification approach involving coating the separator surface with a ceramic coating (such as inorganic ceramic particles like alumina (Al2O3)). Ceramic particles possess excellent high-temperature resistance (melting points typically exceeding 1500℃), and after coating, the physical support of the ceramic layer can suppress the thermal shrinkage of the substrate, significantly improving the high-temperature stability of the separator and reducing the risk of high-temperature short circuits. However, this modification approach has unavoidable technical drawbacks:

[0005] The formation of ceramic coatings relies on binders: ceramic particles are inorganic and inert materials, unable to adhere to the surface of polyolefin separators on their own. Organic binders (such as polyvinylidene fluoride (PVDF), acrylate polymers, etc.) must be introduced into the coating system to fix the ceramic particles to the separator substrate and between the ceramic particles themselves. However, the battery cell manufacturing process requires a hot-pressing shaping process (typically at temperatures of 80-150℃ and pressures of 0.5-2MPa). During this process, the organic binder in the ceramic coating is prone to softening or even melting, causing adhesion between the ceramic coating and the positive and negative electrode surfaces. In addition, the ceramic layer and residual binder bonded to the electrode surface cover the porous structure of the electrode active material, hindering the penetration and spread of electrolyte at the electrode-separator interface. This results in insufficient electrolyte content inside the cell, which directly obstructs the migration path of ions between the electrode and the separator, significantly reducing ion exchange efficiency. Consequently, this leads to increased internal resistance and Joule heating during charging and discharging. On the other hand, the added ceramic layer itself also negatively impacts the ion conductivity of the separator. This increase in battery impedance is even more pronounced when electrolyte wetting is insufficient. The ion transport rate cannot match the demands of high-rate charging and discharging, resulting in a significant degradation of battery rate performance (such as high-rate discharge capacity and cycle stability), severely affecting the practical application of energy storage devices.

[0006] In summary, although existing ceramic-coated modified separators can improve high-temperature shrinkage resistance, the resulting derivative problems such as poor electrolyte wettability have not been effectively solved, which restricts the simultaneous improvement of battery safety and electrochemical performance. Summary of the Invention

[0007] To address the problems of high battery impedance and insufficient rate performance of existing ceramic separators, this invention provides a large-particle adhesive for separators, a separator coating slurry, a separator, and a battery.

[0008] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0009] On one hand, the present invention provides a large-particle adhesive for diaphragms, wherein the large-particle adhesive is a copolymer, and the copolymer comprises:

[0010] Aromatic ethylene structural units;

[0011] Acrylic ester structural units;

[0012] A cross-linked structural unit, wherein the side chain of the cross-linked structural unit contains reactive functional groups, the reactive functional groups including one or more of epoxy groups, isocyanate groups, siloxane groups, hydroxyl groups, amino groups, carboxyl groups and unsaturated hydrocarbon groups;

[0013] and an acrylamide structural unit, wherein the acrylamide structural unit contains an imidazolidine ketone group.

[0014] Optionally, the particle size of the large-particle adhesive is 1~9μm, and the Tg of the large-particle adhesive is 70~120℃.

[0015] Optionally, the mass ratio of the aromatic ethylene structural unit, the acrylate structural unit, the crosslinking structural unit and the acrylamide structural unit is (50~80):(10~30):(0.5~10):(1~5).

[0016] Optionally, the aromatic ethylene structural unit is a structural unit formed by the polymerization of aromatic ethylene monomers, wherein the aromatic ethylene monomers include one or more of styrene, α-methylstyrene, p-methylstyrene, p-methoxystyrene, 2-vinylnaphthalene, 3-vinylpyridine, and p-hydroxystyrene.

[0017] Optionally, the acrylate structural unit is a structural unit formed by the polymerization of acrylate monomers, and the acrylate monomers include one or more of isobornyl methacrylate, methyl methacrylate, butyl methacrylate, isobutyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, and isooctyl acrylate.

[0018] Optionally, the crosslinked structural unit is a structural unit formed by the polymerization of crosslinking monomers, and the crosslinking monomers include one or more of the following: glycidyl methacrylate, glycidyl acrylate, allyl glycidyl ether, glycidyl methacrylate, methacryloyl isocyanate, 2-isocyanate-based ethyl methacrylate, p-isocyanate-based styrene, vinyltrimethoxysilane, methacryloyloxypropyltrimethoxysilane, vinyltriethoxysilane, acryloyloxypropyltriethoxysilane, divinylbenzene, divinyltoluene, phenylethynyl acrylate, ethynyl methacrylate, N-vinylmaleimide, maleimide-based ethyl acrylate, methacrylic anhydride, p-sulfonyl chloride styrene, hydroxymethylacrylamide, hydroxyethyl acrylate, hydroxypropyl methacrylate, p-hydroxystyrene, glyceryl monoacrylate, aminoethyl methacrylate, N-aminopropylacrylamide, p-aminostyrene, N-methylaminoethyl acrylate, acrylamidopropionic acid, and methacryloyloxymalonic acid.

[0019] Optionally, the acrylamide structural unit is a structural unit formed by the polymerization of acrylamide monomers, and the acrylamide monomers include methacrylamide ethyl vinyl urea.

[0020] In another aspect, the present invention provides a diaphragm coating slurry comprising a first solvent, a binder, and a large-particle adhesive as described above, and optionally comprising a ceramic material.

[0021] In another aspect, the present invention provides a diaphragm including a diaphragm base layer and a diaphragm coating located on the surface of the diaphragm base layer, the diaphragm coating including an adhesive and large-particle adhesive as described above, and optionally including a ceramic material, the large-particle adhesive being at least partially protruding from the surface of the diaphragm coating.

[0022] In another aspect, the present invention provides a battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator as described above, wherein the separator is located between the positive electrode and the negative electrode, the separator coating abuts against the positive electrode, and / or the separator coating abuts against the negative electrode.

[0023] The large-particle adhesive provided by this invention features large particle size, low adhesion, high thermal stability, and electrolyte resistance. When applied to separator coatings, it forms granular protrusions on the separator coating surface, effectively preventing adhesion between the separator and the positive and negative electrodes. These granular protrusions also form electrolyte wetting channels, improving ion conduction efficiency. The large-particle adhesive comprises aromatic ethylene structural units, acrylate structural units, crosslinking structural units, and acrylamide structural units. The rigid molecular framework of the aromatic ethylene structural units imparts excellent morphological stability and high-temperature resistance to the large-particle adhesive, allowing it to maintain its intact particle shape during battery hot-pressing processes (80-120℃) and high-temperature conditions, preventing the loss of "protrusion support" due to softening and deformation. Functionally, it lays the structural foundation for anti-adhesion; the ester functional groups of the acrylate structural unit can improve the compatibility of large-particle adhesive with the binder and solvent in the membrane coating, ensuring that the large-particle adhesive is uniformly dispersed in the coating, avoiding localized areas without protrusions caused by agglomeration, and ensuring the uniformity of electrolyte channels; the reactive functional groups (such as epoxy groups, siloxane groups, etc.) of the side chains of the crosslinking structural unit can covalently crosslink with the membrane substrate, binder or other coating components to form a stable three-dimensional crosslinking network, further enhancing the mechanical strength and thermal stability of the large-particle adhesive, ensuring that the particles do not break or fall off during long-term use, and continuously maintaining the protrusion. In terms of morphology, the strong polarity of the imidazolium ketone group in the acrylamide structural unit can form hydrogen bonds or dipole interactions with polar solvents in the electrolyte (such as ethylene carbonate EC and dimethyl carbonate DMC), significantly improving the wettability of the electrolyte on the surface of large-particle adhesives. At the same time, this group can reduce the contact angle between the electrolyte and the separator coating, accelerating the penetration and spreading of the electrolyte between the separator coating and the positive and negative electrodes. Through the synergistic cooperation of the above structural units, the stable protrusion morphology of large-particle adhesives on the separator coating can be improved, avoiding adhesion, improving the wettability of the electrolyte, and thus effectively reducing battery impedance and improving rate performance. Detailed Implementation

[0024] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0025] One embodiment of the present invention provides a large-particle adhesive for diaphragms, wherein the large-particle adhesive is a copolymer, and the copolymer comprises:

[0026] Aromatic ethylene structural units;

[0027] Acrylic ester structural units;

[0028] A cross-linked structural unit, wherein the side chain of the cross-linked structural unit contains reactive functional groups, the reactive functional groups including one or more of epoxy groups, isocyanate groups, siloxane groups, hydroxyl groups, amino groups, carboxyl groups and unsaturated hydrocarbon groups;

[0029] and an acrylamide structural unit, wherein the acrylamide structural unit contains an imidazolidine ketone group.

[0030] The large-particle adhesive provided by this invention features large particle size, low adhesion, high thermal stability, and electrolyte resistance. When applied to separator coatings, it forms granular protrusions on the coating surface, effectively preventing adhesion between the separator and the positive and negative electrodes. These granular protrusions also create electrolyte wetting channels, improving ion conduction efficiency. The large-particle adhesive comprises aromatic ethylene structural units, acrylate structural units, crosslinking structural units, and acrylamide structural units. The rigid molecular framework of the aromatic ethylene structural units endows the large-particle adhesive with excellent morphological stability and high-temperature resistance, allowing it to maintain its intact particle shape during battery hot-pressing processes (80-120℃) and high-temperature conditions, preventing the loss of "protrusion support" due to softening and deformation. Functionally, it lays the structural foundation for anti-adhesion; the ester functional groups of the acrylate structural unit can improve the compatibility of large-particle adhesive with the binder and solvent in the membrane coating, ensuring that the large-particle adhesive is uniformly dispersed in the coating, avoiding localized areas without protrusions caused by agglomeration, and ensuring the uniformity of electrolyte channels; the reactive functional groups (such as epoxy groups, siloxane groups, etc.) of the side chains of the crosslinking structural unit can covalently crosslink with the membrane substrate, binder or other coating components to form a stable three-dimensional crosslinking network, further enhancing the mechanical strength and thermal stability of the large-particle adhesive, ensuring that the particles do not break or fall off during long-term use, and continuously maintaining the protrusion. In terms of morphology, the strong polarity of the imidazolium ketone group in the acrylamide structural unit can form hydrogen bonds or dipole interactions with polar solvents in the electrolyte (such as ethylene carbonate EC and dimethyl carbonate DMC), significantly improving the wettability of the electrolyte on the surface of large-particle adhesives. At the same time, this group can reduce the contact angle between the electrolyte and the separator coating, accelerating the penetration and spreading of the electrolyte between the separator coating and the positive and negative electrodes. Through the synergistic cooperation of the above structural units, the stable protrusion morphology of large-particle adhesives on the separator coating can be improved, avoiding adhesion, improving the wettability of the electrolyte, and thus effectively reducing battery impedance and improving rate performance.

[0031] In some embodiments, the particle size of the large-particle adhesive is 1~9μm.

[0032] In a preferred embodiment, the particle size of the large-particle adhesive is 2~5μm.

[0033] If the particle size of the large-particle adhesive is too small, it will not be able to form protrusions that effectively separate the separator and the positive and negative electrodes, which will easily lead to problems such as separator adhesion and insufficient electrolyte wetting of the battery cell; if the particle size of the large-particle adhesive is too large, it will affect the smoothness of the separator coating and also affect the adhesion stability of the large-particle adhesive on the separator coating.

[0034] In some embodiments, the Tg of the large particle adhesive is 70~120℃.

[0035] In a preferred embodiment, the Tg of the large particle adhesive is 80~120℃.

[0036] When the Tg of the large-particle adhesive is within the above range, it can be ensured that the large-particle adhesive does not soften or deform during hot pressing and maintains its raised shape. At the same time, it is lower than the melting temperature of polyolefin separator substrate (PE about 135°C, PP about 160°C), which avoids the large-particle adhesive from cracking due to excessively high Tg (>120°C) under the high temperature conditions of separator processing or battery, thus taking into account both thermal stability and mechanical toughness and ensuring long-term reliability.

[0037] In some embodiments, the mass ratio of the aromatic ethylene structural unit, the acrylate structural unit, the crosslinking structural unit and the acrylamide structural unit is (50~80):(10~30):(0.5~10):(1~5).

[0038] By limiting the mass ratio of aromatic ethylene structural units, acrylate structural units, crosslinking structural units, and acrylamide structural units (e.g., aromatic ethylene structural units account for more than 60%), the functional proportion of each structural unit can be precisely controlled.

[0039] A high proportion of aromatic ethylene units ensures the core rigidity and high temperature resistance of large particle adhesives, and avoids instability of morphology due to too low a proportion.

[0040] An appropriate amount of acrylate units can balance rigidity and compatibility, avoiding the softening of particles due to excessive proportion and uneven dispersion due to insufficient proportion;

[0041] The proportion of the appropriate cross-linking structural units can control the cross-linking density, avoiding excessive cross-linking leading to particle brittleness and excessive cross-linking leading to insufficient thermal stability.

[0042] A reasonable proportion of acrylamide units can ensure wettability without affecting the rigidity and stability of other units;

[0043] Ultimately, by optimizing the mass ratio, the functions of each structural unit are maximized and coordinated, ensuring that the large particle adhesive simultaneously meets the requirements of stable protrusion shape, good electrolyte wettability, and excellent mechanical toughness, making it suitable for industrial production.

[0044] In some embodiments, the aromatic ethylene structural unit is a structural unit formed by the polymerization of aromatic ethylene monomers, wherein the aromatic ethylene monomers include one or more of styrene, α-methylstyrene, p-methylstyrene, p-methoxystyrene, 2-vinylnaphthalene, 3-vinylpyridine, and p-hydroxystyrene.

[0045] The aromatic ethylene monomers used above have a benzene ring structure, which has the characteristics of high rigidity and excellent high temperature resistance. This can effectively improve the morphological stability of large particle adhesives, and they do not soften or deform under hot pressing and high temperature conditions, ensuring the continued effectiveness of the raised function.

[0046] In some embodiments, the acrylate structural unit is a structural unit formed by the polymerization of acrylate monomers, and the acrylate monomers include one or more of isobornyl methacrylate, methyl methacrylate, butyl methacrylate, isobutyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, and isooctyl acrylate.

[0047] Ester functional groups can form weak interactions (such as van der Waals forces) with adhesives and membrane substrates, improving the dispersibility of large adhesive particles in coatings. The flexibility and compatibility of acrylate units can be adjusted by selecting different ester structures: for example, isobornyl methacrylate (containing a bicyclic structure) can improve unit rigidity and help aromatic ethylene units maintain particle morphology; butyl methacrylate (long-chain ester group) can enhance flexibility and prevent particle brittleness.

[0048] In some embodiments, the crosslinked structural unit is a structural unit formed by the polymerization of crosslinking monomers, and the crosslinking monomers include one or more of the following: glycidyl methacrylate, glycidyl acrylate, allyl glycidyl ether, glycidyl methacrylate, methacryloyl isocyanate, 2-isocyanate-based ethyl methacrylate, p-isocyanate-based styrene, vinyltrimethoxysilane, methacryloyloxypropyltrimethoxysilane, vinyltriethoxysilane, acryloyloxypropyltriethoxysilane, divinylbenzene, divinyltoluene, phenylethynyl acrylate, ethynyl methacrylate, N-vinylmaleimide, maleimide-based ethyl acrylate, methacrylic anhydride, p-sulfonyl chloride styrene, hydroxymethylacrylamide, hydroxyethyl acrylate, hydroxypropyl methacrylate, p-hydroxystyrene, glyceryl monoacrylate, aminoethyl methacrylate, N-aminopropylacrylamide, p-aminostyrene, N-methylaminoethyl acrylate, acrylamidopropionic acid, and methacryloyloxymalonic acid.

[0049] Using the above crosslinking monomers can form a network crosslinking in the large particle adhesive, which is beneficial to improving the thermal stability and electrolyte resistance of the large particle adhesive.

[0050] In some embodiments, the acrylamide structural unit is a structural unit formed by the polymerization of acrylamide monomers, wherein the acrylamide monomers include methacrylamide ethyl vinyl urea.

[0051] Compared to the amide group of ordinary acrylamide, the methacrylamide ethylvinyl urea has a stronger interaction with the electrolyte, which can significantly reduce the contact angle between the electrolyte and large particle adhesives and accelerate electrolyte wetting. In addition, the imidazolium ketone group has excellent chemical stability and does not decompose or fall off during long-term charge-discharge cycles of the battery, ensuring long-term stable wettability and avoiding a decrease in ion conduction efficiency due to group failure.

[0052] In some embodiments, without weakening the performance of the large-particle adhesive of this application, those skilled in the art may add other monomers to participate in the polymerization to form structural units as needed. The other monomers include, but are not limited to, vinyl nonpolar monomers, heteroatom-containing vinyl monomers, and (meth)acrylate functional derivative monomers. The vinyl nonpolar monomers specifically include one or more of vinyl acetate, vinyl chloride, vinylidene chloride, ethylene, propylene, 1-butene, isoprene, and butadiene. The heteroatom-containing vinyl monomers specifically include one or more of N-vinylpyrrolidone, N-vinylcaprolactam, vinylcarbazole, vinylpyrimidine, and vinylquinoline. The (meth)acrylate functional derivative monomers specifically include one or more of perfluorooctyl acrylate, dimethylaminoethyl methacrylate, and 2-ethylhexyl acrylate.

[0053] Another embodiment of the present invention provides a method for preparing large particle adhesive as described above, comprising the following operations:

[0054] The monomer and initiator are added to a second solvent, and a dispersion containing large-particle glue is obtained through polymerization and crosslinking.

[0055] The polymer monomers include aromatic ethylene monomers, acrylate monomers, crosslinking monomers, and acrylamide monomers.

[0056] In some embodiments, the polymerizable monomer and the initiator may be introduced in different ways, for example:

[0057] In one embodiment, all the monomers are added to a solvent to form a homogeneous monomer mixture, and an initiator is added to the monomer mixture either all at once or by dripping to initiate a polymerization reaction.

[0058] In one embodiment, a portion of the monomer is added to a solvent to form a homogeneous monomer mixture. A portion of the initiator is added directly to the monomer mixture or by dripping to form a polymerization seed. The remaining monomer and initiator are then added to allow the polymerization seed to grow to the desired particle size.

[0059] In one embodiment, the polymerization reaction is carried out by adding the monomer solution dropwise to the initiator solution.

[0060] In one embodiment, the polymerization reaction is carried out by simultaneously adding the monomer solution and the initiator dropwise.

[0061] In some embodiments, the initiator includes one or more of the following: azo initiators (such as azobisisobutyronitrile, azobisisoheptanenitrile, azodimethylpentanonitrile, azodicyclohexylformonitrile, and dimethyl azobisisobutyrate), peroxide initiators (such as benzoyl peroxide, lauroyl peroxide, di-tert-butyl peroxide, di-tert-pentyl peroxide, methyl ethyl ketone peroxide, tert-butyl hydroperoxide, and cumene hydroperoxide), and persulfate initiators (such as potassium persulfate, sodium persulfate, and ammonium persulfate).

[0062] In some embodiments, a surfactant is added to the second solvent. The surfactant includes one or more of anionic surfactants, cationic surfactants, and nonionic surfactants. Specifically, the anionic surfactant may be selected from one or more of alkylbenzene sulfonates (such as sodium dodecylbenzene sulfonate, sodium tetradecylbenzene sulfonate, sodium hexadecylbenzene sulfonate), alkyl sulfates (such as sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium hexadecyl sulfate), fatty acid salts (such as sodium stearate, sodium palmitate, sodium laurylate), alkyl sulfonates (such as sodium dodecyl sulfonate, sodium α-olefin sulfonate), and succinate sulfonates (such as sodium bis(2-ethylhexyl)succinate sulfonate, sodium bisoctylsuccinate sulfonate). The cationic surfactant may be selected from one or more of alkyl quaternary ammonium salts (such as hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium bromide), alkyl pyridine salts (such as hexadecylpyridine chloride, octadecylpyridine bromide), and benzyl quaternary ammonium salts (such as benzyltrimethylammonium chloride, benzyltriethylammonium bromide). The nonionic surfactant may be selected from one or more of the following: polyoxyethylene type (such as Tween 20, Tween 40, Tween 60, Tween 80, Span 20, Span 40, Span 60, Span 80, polyethylene glycol octylphenyl ether, polyethylene glycol nonylphenyl ether, fatty alcohol polyoxyethylene ether (such as lauryl alcohol polyoxyethylene ether, stearyl alcohol polyoxyethylene ether)), polyol type (such as glyceryl monostearate, glyceryl monooleate, sorbitan monostearate), and alkyl glycosides (such as dodecyl glycoside, tetradecyl glycoside, hexadecyl glycoside).

[0063] In some embodiments, the second solvent comprises one or more of an organic solvent and an aqueous solvent. Specifically, the organic solvent may be selected from one or more of alcohols (ethanol, propanol, ethylene glycol), aromatic hydrocarbons (such as toluene, xylene, ethylbenzene, cumene), esters (such as ethyl acetate, butyl acetate, isobutyl acetate, ethyl propionate, dimethyl carbonate, diethyl carbonate), ketones (such as acetone, butanone, methyl isobutyl ketone, cyclohexanone, diacetone alcohol), amides (such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone), ethers (such as tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, propylene glycol methyl ether), and sulfoxides (such as dimethyl sulfoxide). The aqueous solvent may be selected from deionized water, distilled water, ultrapure water, or a mixture of an aqueous solvent and an organic solvent (such as a mixture of deionized water and ethanol, or a mixture of deionized water and propylene glycol methyl ether), wherein the mass percentage of the aqueous solvent in the mixture is 50%-95%.

[0064] In some embodiments, the solvents used in preparing large particle adhesives or membrane coating slurries include aqueous solvents, specifically deionized water, distilled water, ultrapure water, or a mixture of aqueous solvents and organic solvents (such as a mixture of deionized water and ethanol, or a mixture of deionized water and propylene glycol methyl ether), wherein the mass percentage of aqueous solvents in the mixture is 50%-95%.

[0065] Another embodiment of the present invention provides a diaphragm coating slurry comprising a first solvent, a binder, and a large-particle adhesive as described above, and optionally including a ceramic material.

[0066] The types of solvents that can be selected for the first solvent are the same as those for the second solvent, and will not be described again.

[0067] The adhesive includes one or more of the following: fluoropolymers (such as polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-trifluorochloroethylene copolymer, polytetrafluoroethylene), polyacrylonitrile compounds (such as polyacrylonitrile, polyacrylonitrile-methyl methacrylate copolymer), polyvinyl alcohols (such as polyvinyl alcohol, polyvinyl alcohol formal, polyvinyl alcohol butyral), acrylates (such as polymethyl methacrylate, methyl methacrylate-butyl acrylate copolymer, ethyl acrylate-methyl acrylate copolymer), rubbers (such as styrene-butadiene rubber, nitrile rubber, carboxylated styrene-butadiene rubber), and cellulose compounds (such as sodium carboxymethyl cellulose, hydroxypropyl methylcellulose, hydroxyethyl cellulose).

[0068] The ceramic material includes one or more of oxides, composite oxides, and non-oxides. Specifically, the oxides may be selected from one or more of the following: alumina (e.g., α-alumina, γ-alumina, δ-alumina), silicon dioxide (e.g., fumed silica, precipitated silica, fused silica), titanium dioxide (e.g., rutile titanium dioxide, anatase titanium dioxide), zirconium oxide (e.g., monoclinic zirconium oxide, tetragonal zirconium oxide, cubic zirconium oxide), magnesium oxide, zinc oxide, cerium oxide, yttrium oxide, lanthanum oxide, neodymium oxide, and gadolinium oxide. The composite oxides may be selected from one or more of the following: spinel-type composite oxides (e.g., magnesium aluminum spinel, zinc aluminum spinel, nickel aluminum spinel), perovskite-type composite oxides (e.g., lanthanum aluminate, barium titanate, strontium titanate, barium zirconate, strontium zirconate), titanates (e.g., lithium titanate, magnesium titanate, zinc titanate), zirconates (e.g., calcium zirconate, magnesium zirconate), and aluminates (e.g., calcium aluminate, barium aluminate, magnesium aluminate). The non-oxide may be selected from one or more of aluminum nitride, boron nitride (such as hexagonal boron nitride, cubic boron nitride), silicon carbide (such as α-silicon carbide, β-silicon carbide), silicon nitride (such as α-silicon nitride, β-silicon nitride), aluminum boride, and zirconium boride.

[0069] Another embodiment of the present invention provides a diaphragm including a diaphragm base layer and a diaphragm coating located on the surface of the diaphragm base layer, the diaphragm coating including an adhesive and a large particle adhesive, and optionally including a ceramic material, the large particle adhesive being at least partially protruding from the surface of the diaphragm coating.

[0070] The membrane base layer comprises one or more of polyolefin materials and special polymer materials. Specifically, the polyolefin materials may be selected from one or more of polyethylene (such as low-density polyethylene, high-density polyethylene, linear low-density polyethylene), polypropylene (such as homopolymer polypropylene, block copolymer polypropylene, random copolymer polypropylene), and polyethylene-polypropylene composite substrate (such as polyethylene / polypropylene bilayer composite film, polypropylene / polyethylene / polypropylene trilayer composite film). The special polymer materials include one or more of polyimide, polyetheretherketone, polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polytetrafluoroethylene, and polyvinylidene fluoride.

[0071] Another embodiment of the present invention provides a battery including a positive electrode, a negative electrode, an electrolyte and a separator as described above, the separator being located between the positive electrode and the negative electrode, the separator coating abutting against the positive electrode, and / or the separator coating abutting against the negative electrode.

[0072] By employing the separator as described above, the raised structure of the large-particle adhesive prevents thermal adhesion when the separator coating comes into contact with the positive and negative electrodes, thus forming a channel for electrolyte flow and wetting between the separator and the positive and negative electrodes. This increases the contact area at the electrode / electrolyte interface, improves ion exchange efficiency, reduces battery impedance, and decreases Joule heating during charging and discharging, avoiding a vicious cycle of electrolyte decomposition and gas production due to heat generation. Simultaneously, the improved ion conduction efficiency can meet the demands of high-rate charging and discharging. Ceramic materials (optional) suppress high-temperature shrinkage of the separator; under these dual effects, the risk of high-temperature short circuits in the battery is reduced, and the probability of thermal runaway is significantly decreased.

[0073] The present invention will be further illustrated by the following examples.

[0074] Example 1

[0075] This embodiment illustrates the large-particle adhesive, separator, battery, and their preparation method disclosed in this invention, including the following steps:

[0076] 1. Mixing solvent and surfactant

[0077] Add 200 mL of ethanol to a 500 mL four-necked flask (equipped with a stirrer, constant pressure dropping funnel, thermometer, and reflux condenser), turn on the stirrer (300 r / min), add Tween 80 (1.5 g) and sodium dodecylbenzenesulfonate (0.5 g) at room temperature, and stir for 15 min until the surfactant is completely dissolved to form a homogeneous solvent-surfactant system.

[0078] 2. All monomers dispersed

[0079] Styrene (65g), butyl methacrylate (20g), methacrylamide isocyanate (10g), and methacrylamide ethyl vinyl urea (5g) were added sequentially to the four-necked flask. The temperature was raised to 75℃ (below the decomposition temperature of the initiator, to ensure uniform dispersion of the monomers first), and stirring was maintained at 350r / min for 30min. No obvious oil phase separation was observed by the naked eye, forming a uniform monomer-solvent-surfactant dispersion system.

[0080] 3. Initiator addition and polymerization reaction

[0081] Add the dissolved AIBN initiator solution (1.2g AIBN + 20mL mixed solvent) to a constant pressure dropping funnel. Under constant temperature of 75℃ and stirring at 350r / min, slowly add the initiator solution at a rate of 0.35mL / min for 60min.

[0082] After the initiator was added, the temperature was raised to 85°C and maintained for polymerization for 5 hours. During the polymerization process, the system gradually formed a milky white suspension.

[0083] 4. Post-processing and product characterization

[0084] After the polymerization reaction is complete, the reaction solution is cooled to room temperature, poured into a centrifuge tube, and centrifuged at 8000 r / min for 15 min. The supernatant (containing unreacted monomers, solvents and surfactants) is discarded.

[0085] The solid particles obtained by repeated washing and centrifugation with ethanol (to remove residual impurities) were obtained as large-particle latex with a solid content of 40%.

[0086] 5. Diaphragm preparation

[0087] The large-particle adhesive latex, alumina, CMC and diaphragm adhesive are mixed and dispersed to obtain a diaphragm coating slurry. The mass ratio of the large-particle adhesive, alumina, CMC and diaphragm adhesive is 5:95:0.5:4.5. The slurry is coated onto the surface of the polypropylene diaphragm base layer using a micro-gravure coating process and dried with hot air at 60℃ for 10 minutes to obtain the diaphragm coating.

[0088] 6. Battery manufacturing

[0089] The obtained separator is assembled with the positive electrode (lithium cobalt oxide) and the negative electrode (graphite) into a stacked battery. After hot pressing, it is installed in the casing, and then injected with electrolyte, formed, and aged to obtain a lithium-ion battery.

[0090] Example 2

[0091] This embodiment illustrates the large particle adhesive, diaphragm, and preparation method disclosed in this invention, and includes most of the operational steps in Example 1 below, with the following difference:

[0092] The monomers used in the polymerization reaction are: styrene (70g), butyl acrylate (15g), glycidyl methacrylate (3g), and methacrylamide ethyl vinyl urea (2g).

[0093] Example 3

[0094] This embodiment illustrates the large particle adhesive, diaphragm, and preparation method disclosed in this invention, and includes most of the operational steps in Example 1 below, with the following difference:

[0095] The monomers used in the polymerization reaction are: styrene (75g), methyl methacrylate (20g), vinyltriethoxysilane (5g), and methacrylamide ethylvinyl urea (3g).

[0096] Example 4

[0097] This embodiment illustrates the large particle adhesive, diaphragm, and preparation method disclosed in this invention, and includes most of the operational steps in Example 1 below, with the following difference:

[0098] The monomers used in the polymerization reaction are: styrene (80g), isobutyl methacrylate (15g), hydroxymethylacrylamide (8g), and methacrylamide ethylvinyl urea (3g).

[0099] Example 5

[0100] This embodiment illustrates the large particle adhesive, diaphragm, and preparation method disclosed in this invention, and includes most of the operational steps in Example 1 below, with the following difference:

[0101] The monomers used in the polymerization reaction are: styrene (50g), methyl acrylate (30g), hydroxymethylacrylamide (0.5g), and methacrylamide ethylvinyl urea (1g).

[0102] Example 6

[0103] This embodiment illustrates the large particle adhesive, diaphragm, and preparation method disclosed in this invention, and includes most of the operational steps in Example 1 below, with the following difference:

[0104] The monomers used in the polymerization reaction are: styrene (80g), methyl methacrylate (30g), glycidyl methacrylate (8g), and methacrylamide ethyl vinyl urea (5g).

[0105] Comparative Example 1

[0106] This comparative example is used to illustrate the large particle adhesive, diaphragm, and preparation method disclosed in this invention, including most of the operational steps in Example 1 below, with the following differences:

[0107] Methyl acrylate is used instead of styrene in the polymerization monomer.

[0108] Comparative Example 2

[0109] This comparative example is used to illustrate the large particle adhesive, diaphragm, and preparation method disclosed in this invention, including most of the operational steps in Example 1 below, with the following differences:

[0110] The monomers include only styrene, butyl methacrylate, and methacryloyl isocyanate, but not methacrylamide ethyl vinyl urea.

[0111] Comparative Example 3

[0112] This comparative example is used to illustrate the large particle adhesive, diaphragm, and preparation method disclosed in this invention, including most of the operational steps in Example 1 below, with the following differences:

[0113] The monomers include only styrene, methacryloyl isocyanate, and methacrylamide ethyl vinyl urea, but not butyl methacrylate.

[0114] Comparative Example 4

[0115] This comparative example is used to illustrate the large particle adhesive, diaphragm, and preparation method disclosed in this invention, including most of the operational steps in Example 1 below, with the following differences:

[0116] The monomers include only styrene, butyl methacrylate, and methacrylamide ethyl vinyl urea, but not methacryloyl isocyanate.

[0117] Performance testing

[0118] The large-particle adhesive and diaphragm prepared above were subjected to the following performance tests:

[0119] The D50 particle size of large-particle adhesive was determined using a laser particle size analyzer.

[0120] The glass transition temperature (Tg) of large particle adhesives was determined by differential scanning calorimetry (DSC).

[0121] 3. The obtained batteries were tested using an electrochemical workstation, and the average value of 5 batteries in each group was taken.

[0122] The test results are entered into Table 1.

[0123] Table 1

[0124]

[0125] The test results of Examples 1-4 and Comparative Examples 1-4 show that the four structural units (aromatic ethylene structural unit, acrylate structural unit, crosslinking structural unit, and acrylamide structural unit) of the large particle adhesive defined in this invention work synergistically to ensure the thermal stability (Tg) of the large particle adhesive and reduce battery impedance. The absence of any structural unit or the replacement of a key structural unit will lead to a decrease in the thermal stability of the large particle adhesive or an increase in battery impedance, making it impossible to simultaneously achieve good morphological stability and excellent electrochemical performance.

[0126] The test results from Examples 1-4 and Examples 5-6 show that when the mass ratio of each structural unit, particle size, and Tg parameter of the large-particle adhesive are within a suitable range, it is more beneficial to improve battery performance. When the mass ratio of each structural unit exceeds the specified range, or when the Tg deviates from the preferred range, it will lead to a significant increase in battery impedance, affecting the effect of the large-particle adhesive in forming stable protrusions in the separator coating and improving electrolyte wettability, thereby restricting the electrochemical performance of the battery.

[0127] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A separator coating slurry, characterized by, The mixture includes a first solvent, a binder, and large-particle adhesive, and optionally includes a ceramic material, wherein the large-particle adhesive is a copolymer, and the copolymer comprises: Aromatic ethylene structural units; Acrylic ester structural units; A cross-linked structural unit, wherein the side chain of the cross-linked structural unit contains reactive functional groups, the reactive functional groups including one or more of epoxy groups, isocyanate groups, siloxane groups, hydroxyl groups, amino groups, carboxyl groups and unsaturated hydrocarbon groups; and an acrylamide structural unit, wherein the acrylamide structural unit contains an imidazolidine ketone group.

2. The diaphragm coating slurry according to claim 1, characterized in that, The particle size of the large-particle adhesive is 1~9μm, and the Tg of the large-particle adhesive is 70~120℃.

3. The separator coating slurry of claim 1, wherein, The mass ratio of the aromatic ethylene structural unit, the acrylate structural unit, the crosslinking structural unit and the acrylamide structural unit is (50~80):(10~30):(0.5~10):(1~5).

4. The separator coating slurry of claim 1, wherein, The aromatic ethylene structural unit is a structural unit formed by the polymerization of aromatic ethylene monomers, and the aromatic ethylene monomers include one or more of styrene, α-methylstyrene, p-methylstyrene, p-methoxystyrene, 2-vinylnaphthalene, 3-vinylpyridine and p-hydroxystyrene.

5. The separator coating slurry of claim 1, wherein, The acrylate structural unit is a structural unit formed by the polymerization of acrylate monomers, and the acrylate monomers include one or more of isobornyl methacrylate, methyl methacrylate, butyl methacrylate, isobutyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, and isooctyl acrylate.

6. The separator coating slurry of claim 1, wherein, The cross-linked structural unit is a structural unit formed by the polymerization of cross-linking monomers. The cross-linking monomers include one or more of the following: glycidyl methacrylate, glycidyl acrylate, allyl glycidyl ether, glycidyl methacrylate, methacryloyl isocyanate, 2-isocyanate-based ethyl methacrylate, p-isocyanate-based styrene, vinyltrimethoxysilane, methacryloyloxypropyltrimethoxysilane, vinyltriethoxysilane, acryloyloxypropyltriethoxysilane, divinylbenzene, divinyltoluene, phenylethynyl acrylate, ethynyl methacrylate, N-vinylmaleimide, maleimide-based ethyl acrylate, methacrylic anhydride, hydroxymethylacrylamide, hydroxyethyl acrylate, hydroxypropyl methacrylate, p-hydroxystyrene, glyceryl monoacrylate, aminoethyl methacrylate, N-aminopropylacrylamide, p-aminostyrene, N-methylaminoethyl acrylate, acrylamide propionic acid, and methacryloyloxymalonic acid.

7. The separator coating slurry of claim 1, wherein, The acrylamide structural unit is a structural unit formed by the polymerization of acrylamide monomers, and the acrylamide monomers include methacrylamide ethyl vinyl urea.

8. A diaphragm characterized by, The membrane includes a membrane base layer and a membrane coating located on the surface of the membrane base layer. The membrane coating includes an adhesive and a large-particle adhesive, and optionally includes a ceramic material. The large-particle adhesive at least partially protrudes from the surface of the membrane coating. The large-particle adhesive is a copolymer, and the copolymer includes: Aromatic ethylene structural units; Acrylic ester structural units; A cross-linked structural unit, wherein the side chain of the cross-linked structural unit contains reactive functional groups, the reactive functional groups including one or more of epoxy groups, isocyanate groups, siloxane groups, hydroxyl groups, amino groups, carboxyl groups and unsaturated hydrocarbon groups; and an acrylamide structural unit, wherein the acrylamide structural unit contains an imidazolidine ketone group.

9. The diaphragm of claim 8, wherein, The particle size of the large-particle adhesive is 1~9μm, and the Tg of the large-particle adhesive is 70~120℃.

10. The septum of claim 8, wherein, The mass ratio of the aromatic ethylene structural unit, the acrylate structural unit, the crosslinking structural unit and the acrylamide structural unit is (50~80):(10~30):(0.5~10):(1~5).

11. The diaphragm of claim 8, wherein The aromatic ethylene structural unit is a structural unit formed by the polymerization of aromatic ethylene monomers, and the aromatic ethylene monomers include one or more of styrene, α-methylstyrene, p-methylstyrene, p-methoxystyrene, 2-vinylnaphthalene, 3-vinylpyridine and p-hydroxystyrene.

12. The septum of claim 8, wherein, The acrylate structural unit is a structural unit formed by the polymerization of acrylate monomers, and the acrylate monomers include one or more of isobornyl methacrylate, methyl methacrylate, butyl methacrylate, isobutyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, and isooctyl acrylate.

13. The septum of claim 8, wherein, The cross-linked structural unit is a structural unit formed by the polymerization of cross-linking monomers. The cross-linking monomers include one or more of the following: glycidyl methacrylate, glycidyl acrylate, allyl glycidyl ether, glycidyl methacrylate, methacryloyl isocyanate, 2-isocyanate-based ethyl methacrylate, p-isocyanate-based styrene, vinyltrimethoxysilane, methacryloyloxypropyltrimethoxysilane, vinyltriethoxysilane, acryloyloxypropyltriethoxysilane, divinylbenzene, divinyltoluene, phenylethynyl acrylate, ethynyl methacrylate, N-vinylmaleimide, maleimide-based ethyl acrylate, methacrylic anhydride, hydroxymethylacrylamide, hydroxyethyl acrylate, hydroxypropyl methacrylate, p-hydroxystyrene, glyceryl monoacrylate, aminoethyl methacrylate, N-aminopropylacrylamide, p-aminostyrene, N-methylaminoethyl acrylate, acrylamide propionic acid, and methacryloyloxymalonic acid.

14. The septum of claim 8, wherein, The acrylamide structural unit is a structural unit formed by the polymerization of acrylamide monomers, and the acrylamide monomers include methacrylamide ethyl vinyl urea.

15. A battery, characterized by It includes a positive electrode, a negative electrode, an electrolyte, and a separator as described in any one of claims 8 to 14, wherein the separator is located between the positive electrode and the negative electrode, the separator coating abuts against the positive electrode, and / or the separator coating abuts against the negative electrode.

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