Composition for forming a battery shutdown layer

Abstract

The composition comprises a polyolefin dispersion of one or more polyolefins having a melting point of 80°C to 130°C and an average particle size of 0.5 microns to 5 microns, and a repair dispersion containing ethylene methacrylic acid copolymer ("EMAA") having a melting point of 80°C to 120°C and an average particle size of 0.1 microns to 1 micron, wherein the EMAA copolymer is neutralized to 0% to 40%, and furthermore, the weight ratio of EMAA to polyolefin in the composition is 1:100 to 10:100.

Description

Technical Field

[0001] The present disclosure generally relates to compositions, and more specifically to ceramic compositions for forming a shutdown layer.

Background Art

[0002] Introduction Lithium-ion batteries (LIBs) offer various advantages over conventional battery types, such as high energy density, high operating voltage, and long cycle life. These advantages mean that LIBs are widely used as power sources for various mobile devices and electric vehicles. One important component of LIBs is the separator. The separator is typically made of a polyolefin-based porous membrane containing high-density polyethylene. The separator serves to separate the cathode from the anode to avoid battery short circuits while allowing lithium ions to pass through during battery charging and discharging.

[0003] When the LIB exceeds the critical temperature, a heat-generating chemical reaction is initiated, heat is accumulated due to the evaporation of the electrolyte, internal pressure is generated, and pinholes occur in the separator. The pinholes cause uncontrollable transport of lithium ions, leading to a temperature increase and thermal runaway. To prevent thermal runaway, the concept of a shutdown layer has been introduced for LIB separators. The shutdown layer is a layer that employs a phase change mechanism to stop ion transport when the temperature of the separator approaches the starting point of thermal runaway. The shutdown layer shuts down the transport of lithium ions by melting and blocking the pinholes and diffusion channels of the separator. Despite being a promising concept, the commercialization progress has been slow because the shutdown performance, measured as the difference in the electrical resistance of the LIB before and after the phase change of the shutdown layer, is too low to effectively suppress thermal runaway. To withstand thermal runaway sufficiently, LIBs containing a shutdown layer need to have a shutdown performance of 50 ohms or more.

[0004] Ethylene-methacrylic acid copolymers ("EMAA") are known to exhibit self-healing properties when subjected to physical damage. The more methacrylic acid component is neutralized in the EMAA copolymer, the higher the ion content of the EMAA copolymer. Regarding the self-healing properties of EMAA, the paper "Effect of Ionic Content on Ballistic Self-Healing in EMAA Copolymers and Ionomers" states that the order-to-disorder transition temperature (T i In tests below the melting temperature (T = 40℃), a moderate ion content is most beneficial for repair; on the other hand, the melting temperature (T m It has been explained that at temperatures above 90°C, the repair properties improved with increasing ion content (Polym.Chem., 2013, 4, 4910 (abstract)). Essentially, the greater the neutralization rate of methacrylic acid in EMAA, the greater the self-repair effect observed at higher temperatures. While the self-repair properties of EMAA in air and gaseous environments are understood, the ability of EMAA to maintain its self-repair properties in the presence of solvents and electrolytes is unknown, and persistence cannot be expected due to the lack of other forces present in air and gaseous environments (such as surface tension).

[0005] Considering the above, the discovery of a shutdown layer that not only exhibits shutdown performance of 50 ohms or more in the presence of battery electrolyte, but also includes low-neutralization or non-neutralization EMAA to impart self-healing properties to the shutdown layer, and a composition capable of forming such a shutdown layer, is remarkable. [Overview of the Initiative]

[0006] The inventors of this disclosure have discovered a shutdown layer that not only exhibits shutdown performance of 50 ohms or more in the presence of a battery electrolyte, but also includes a low-neutralizing or non-neutralizing EMAA to give the shutdown layer self-healing properties, and a composition capable of forming a shutdown layer.

[0007] This invention is the result of the surprising discovery that a shutdown layer can be formed using low-neutralization or non-neutralization EMAA, which maintains self-healing properties despite being in contact with the battery electrolyte. Although not bound by theory, EMAA is thought to be present at the interface between the electrolyte and the polyolefin due to its surfactant properties. As the LIB approaches thermal runaway, the amount of interface between the electrolyte and the olefin dramatically decreases as the polyolefin melts and coalesces into a continuous coating. As the interface between the electrolyte and the olefin decreases, EMAA concentrates in areas where the olefin does not form a continuous film, "repairing" defects in the coating by filling holes. Once defects in the coating are sealed, the shutdown layer can effectively prevent thermal runaway. Although the above paper emphasizes that increased ion content is preferable at temperatures above the melting point (90°C), this discovery is surprising because low-neutralization or non-neutralization EMAA can effectively self-heal at these temperatures when used as a shutdown layer in LIBs.

[0008] According to the first feature of this disclosure, the composition comprises a polyolefin dispersion of one or more polyolefins having a melting point of 80°C to 130°C and an average particle size of 0.5 microns to 5 microns, and a repair dispersion containing ethylene methacrylate copolymer ("EMAA") having a melting point of 80°C to 120°C and an average particle size of 0.1 microns to 1 micron, wherein the EMAA copolymer is neutralized to a degree of 0% to 40%, and furthermore, the weight ratio of EMAA to polyolefin in the composition is 1:100 to 10:100.

[0009] According to the second feature of this disclosure, the polyolefin and EMAA are dispersed in water, respectively.

[0010] According to the third feature of this disclosure, the repair dispersion has a solid content of 5% to 40% by weight based on the total weight of the repair dispersion, and the polyolefin dispersion has a solid content of 30% to 70% by weight based on the total weight of the polyolefin dispersion.

[0011] According to the fourth feature of this disclosure, the polyolefin is selected from the group consisting of ethylene, ethylene-propylene copolymer, ethylene-butylene copolymer, ethylene-hexene copolymer, and ethylene-octene copolymer.

[0012] According to the fifth feature of this disclosure, the polyolefin exhibits a melting temperature of 100°C to 120°C.

[0013] According to the sixth feature of this disclosure, the weight ratio of EMAA to polyolefin in the composition is 3:100 to 5:100.

[0014] According to the seventh feature of this disclosure, the polyolefin exhibits a melting temperature of 100°C to 110°C.

[0015] According to the eighth feature of this disclosure, EMAA contains 4% to 20% by weight of methacrylic acid based on the total weight of EMAA.

[0016] According to the ninth feature of this disclosure, the EMAA copolymer is neutralized by 20% to 40%.

[0017] According to the tenth feature of this disclosure, the shutdown composition comprises a composition, a binder, a wetting agent, and a thickening agent. [Modes for carrying out the invention]

[0018] As used herein, the term "and / or" means, when used in an enumeration of two or more items, that any one of the enumerated items may be used on its own, or any combination of two or more of the enumerated items may be used. For example, if a composition is described as containing components A, B, and / or C, the composition may contain A alone, B alone, C alone, A and B in combination, A and C in combination, B and C in combination, or A, B, and C in combination.

[0019] Unless otherwise stated, all ranges include the endpoints.

[0020] Unless otherwise indicated with a hyphenated two-digit test method number, the test method refers to the most recent test method as of the priority date of this document. References to test methods include both references to the testing association and the test method number. Test method organizations are referred to by one of the following abbreviations: ASTM refers to ASTM International (formerly the American Society for Testing and Materials), EN refers to European Norm, DIN refers to the German Institute for Standardization (Deutsches Institut fuer Normung), and ISO refers to the International Organization for Standardization.

[0021] Where used herein, unless otherwise specified, the term “average particle size” means the volume-average particle size determined using a Coulter LS 13 320 particle size analyzer (Beckman Coulter, Brea, Calif.) according to the manufacturer’s recommended procedure for laser scattering.

[0022] As used herein, the term “melt index” means a value determined according to ASTM D-1238 (2013). The melt index value is defined as the amount of polymer molten passing through a heated syringe with a plunger load of 190°C and 2.16 kg load for polyethylene polymers and 230°C and 2.16 kg load for polypropylene polymers at a rate of dg / min (or g / 10 min). For olefin copolymers, the polypropylene melt index test is used if more than 50% by weight of the copolymer contains propylene in its polymerized form. As used herein, the term “melting point” means a value determined by the DSC method using a ramp rate of 10°C / min.

[0023] As used herein, the term "solids content" refers to the weight percentage in the composition of the solids content of the primary polyolefin dispersion, the second film-forming dispersion, the dispersant, and the stabilizer, and, if present, the pigment, filler, or extender, and any additives that are not volatile under the conditions of use of the composition of the present invention. For example, additives such as water, coalescing agents, and solvents or bases such as ammonia or lower alkylamines that are volatile under the conditions of use of the composition of the present invention are not considered solids.

[0024] Composition This disclosure relates to a composition. The composition includes a polyolefin dispersion and a repair dispersion. The composition may be used to form a shutdown composition.

[0025] Polyolefin dispersion The polyolefin dispersion is a plurality of polyolefin particles dispersed in a dispersion medium (e.g., water). The polyolefin may include ethylene, propylene, butylene, hexene, octene, and / or combinations thereof. For example, the polyolefin may be selected from the group consisting of ethylene, ethylene-propylene copolymer, ethylene-butylene copolymer, ethylene-hexene copolymer, and ethylene-octene copolymer. The polyolefin exhibits a melting temperature of 100°C to 120°C. For example, the polyolefin may exhibit a melting temperature of 80°C or higher, or 85°C or higher, or 90°C or higher, or 95°C or higher, or 100°C or higher, or 105°C or higher, or 110°C or higher, or 115°C or higher, or 120°C or higher, or 125°C or higher, while at the same time being 130°C or lower, or 125°C or lower, or 120°C or lower, or 115°C or lower, or 110°C or lower, or 105°C or lower, or 100°C or lower, or 95°C or lower, or 90°C or lower, or 85°C or lower.

[0026] The polyolefin particles in the polyolefin dispersion have an average particle size of 0.5 to 5 microns. For example, the polyolefin particles in the polyolefin dispersion may have an average particle size of 0.5 microns or more, or 1.0 microns or more, or 1.5 microns or more, or 2.0 microns or more, or 2.5 microns or more, or 3.0 microns or more, or 3.5 microns or more, or 4.0 microns or more, or 4.5 microns or more. On the other hand, at the same time, they may have an average particle size of 5.0 microns or less, or 4.5 microns or less, or 4.0 microns or less, or 3.5 microns or less, or 3.0 microns or less, or 2.5 microns or less, or 2.0 microns or less, or 1.5 microns or less, or 1.0 microns or less.

[0027] The polyolefin dispersion may have a solid content of 30% to 70% by weight based on the total weight of the polyolefin dispersion. For example, the polyolefin dispersion may have a solid content of 30% by weight or more, or 35% by weight or more, or 40% by weight or more, or 45% by weight or more, or 50% by weight or more, or 55% by weight or more, or 60% by weight or more, or 65% by weight or more. On the other hand, at the same time, it may have a solid content of 70% by weight or less, or 65% by weight or less, or 60% by weight or less, or 55% by weight or less, or 50% by weight or less, or 45% by weight or less, or 40% by weight or less, or 35% by weight or less.

[0028] A dispersant can be used to prepare the polyolefin dispersion. The dispersant may be a long-chain fatty acid having 14 to 40 carbon atoms, or preferably 16 to 36 carbon atoms, such as Unicid (trademark) 350 dispersant or behenic acid (C 22 )). The dispersant may be present in an amount of 10% by weight or less, or 6% by weight or less, or 4% by weight or less based on the total weight of the polyolefin dispersion.

[0029] Repair dispersion The repair dispersion is a plurality of EMAA particles dispersed or emulsified in a dispersion medium (e.g., water). The EMAA contains 4% to 20% by weight of methacrylic acid-derived units, based on the total weight of the EMAA. For example, the EMAA contains 4% or more by weight, or 5% or more by weight, or 6% or more by weight, or 7% or more by weight, or 8% or more by weight, or 10% or more by weight, or 12% or more by weight, or 14% or more by weight, or 15% or more by weight, or 16% or more by weight, or 18% or more by weight, while simultaneously containing 20% ​​or less by weight, or 18% or less by weight, or 16% or less by weight, or 15% or less by weight, or 14% or less by weight, or 12% or less by weight, or 10% or less by weight, or 8% or less by weight, or 7% or less by weight, or 6% or less by weight of methacrylic acid-derived units. The remainder of the EMAA contains ethylene-derived units.

[0030] EMAA indicates a melting temperature of 80°C to 120°C. For example, EMAA may indicate a melting temperature of 80°C or higher, or 85°C or higher, or 90°C or higher, or 95°C or higher, or 100°C or higher, or 105°C or higher, or 110°C or higher, or 115°C or higher, or 120°C or higher, or 125°C or higher, while simultaneously indicating a melting temperature of 130°C or lower, or 125°C or lower, or 120°C or lower, or 115°C or lower, or 110°C or lower, or 105°C or lower, or 100°C or lower, or 95°C or lower, or 90°C or lower, or 85°C or lower.

[0031] The EMAA particles in the repair dispersion have an average particle size of 0.1 to 1 micron. For example, the polyolefin particles in the polyolefin dispersion may have an average particle size of 0.1 micron or more, or 0.2 micron or more, or 0.3 micron or more, or 0.4 micron or more, or 0.5 micron or more, or 0.6 micron or more, or 0.7 micron or more, or 0.8 micron or more, or 0.9 micron or more, while simultaneously having an average particle size of 1.0 micron or less, or 0.9 micron or less, or 0.8 micron or less, or 0.7 micron or less, or 0.6 micron or less, or 0.5 micron or less, or 0.4 micron or less, or 0.3 micron or less, or 0.2 micron or less.

[0032] The repair dispersion may have a solid content of 5% to 40% by weight, based on the total weight of the polyolefin dispersion. For example, the polyolefin dispersion may have a solid content of 5% or more by weight, or 10% or more by weight, or 15% or more by weight, or 20% or more by weight, or 25% or more by weight, or 30% or more by weight, or 35% or more by weight, based on the total weight of the repair dispersion, while simultaneously having a solid content of 40% or less by weight, or 35% or less by weight, or 30% or less by weight, or 25% or less by weight, or 20% or less by weight, or 15% or less by weight, or 10% or less by weight.

[0033] EMAA may have a wide range of neutralization rates. For example, EMAA may have a total acid content of 0% or more, or 1% or more, or 2% or more, or 4% or more, or 6% or more, or 8% or more, or 10% or more, or 12% or more, or 14% or more, or 16% or more, or 18% or more, or 20% or more, or 22% or more, or 24% or more, or 26% or more, or 28% or more, or 30% or more, or 32% or more, or 34% or more, or 36% or more, or It can be neutralized by 38% or more, while simultaneously being 40% or less, or 38% or less, or 36% or less, or 34% or less, or 32% or less, or 30% or less, or 28% or less, or 26% or less, or 24% or less, or 22% or less, or 20% or less, or 18% or less, or 16% or less, or 14% or less, or 12% or less, or 10% or less, or 8% or less, or 6% or less, or 4% or less, or 2% or less. EMAA can be neutralized using one or more metal ions. The metal ions can be monovalent, divalent, trivalent, polyvalent, or combinations thereof. Examples of suitable metal ions include Li, Na, Ag, Hg, Cu, Be, Mg, Ca, Sr, Ba, Cd, Sn, Pb, Fe, Co, Zn, Ni, Al, Sc, Hf, Ti, Zr, Ce, K, Na, and combinations thereof. When the metal ions are polyvalent, complexing agents such as stearates, oleates, salicylates, and phenolate radicals may be included. The EMAA may be a blend of an EMAA having a neutralization rate of more than 30% and a second EMAA having, for example, a lower neutralization rate, thereby achieving the desired neutralization rate.

[0034] EMAA may be present in the repair dispersion at a concentration such that the weight ratio of EMAA to polyolefin in the composition is 1:100 to 10:100. For example, the weight ratio of EMAA to polyolefin in the composition may be 1:100 or more, or 2:100 or more, or 3:100 or more, or 4:100 or more, or 5:100 or more, or 6:100 or more, or 7:100 or more, or 8:100 or more, or 9:100 or more, while simultaneously being 10:100 or less, or 9:100 or less, or 8:100 or less, or 7:100 or less, or 6:100 or less, or 5:100 or less, or 4:100 or less, or 3:100 or less, or 2:100 or less.

[0035] Shutdown composition As described above, this disclosure also relates to a shutdown composition which may comprise a composition, a binder, a wetting agent, and a thickening agent.

[0036] The thickening agent has the function of thickening the shutdown composition so that it can be applied to the battery separator and adhere well. The shutdown composition may contain 0.01% to 1.00% by weight of the thickening agent based on the total weight of the shutdown composition. For example, the shutdown composition may contain 0.01% or more by weight, or 0.05% or more by weight, or 0.10% or more by weight, or 0.15% or more by weight, or 0.20% or more by weight, or 0.25% or more by weight, or 0.30% or more by weight, or 0.35% or more by weight, or 0.40% or more by weight, or 0.45% or more by weight, or 0.50% or more by weight, or 0.55% or more by weight, or 0.60% or more by weight, or 0.65% or more by weight, or 0.70% or more by weight, or 0.75% or more by weight, or 0.80% or more by weight, or 0.85% or more by weight, or 0.90% or more by weight, or 0. It may contain 95% by weight or more, while simultaneously containing a thickening agent in amounts of 1.00% by weight or less, or 0.95% by weight or less, or 0.90% by weight or less, or 0.85% by weight or less, or 0.80% by weight or less, or 0.75% by weight or less, or 0.70% by weight or less, or 0.65% by weight or less, or 0.60% by weight or less, or 0.55% by weight or less, or 0.50% by weight or less, or 0.45% by weight or less, or 0.40% by weight or less, or 0.35% by weight or less, or 0.30% by weight or less, or 0.25% by weight or less, or 0.20% by weight or less, or 0.15% by weight or less, or 0.10% by weight or less, or 0.05% by weight or less.

[0037] The thickener is a copolymer of units derived from ethyl acrylate, methacrylic acid, and functional monomers. The thickener may be a random copolymer or a block copolymer. The thickener can be added to the shutdown composition as a dispersion of the thickener in one or more fluids (e.g., water). The thickener may have a solid content of 5% to 50% by weight, based on the total weight of the thickener. For example, the thickener may have a solid content of 5% or more by weight, or 10% or more by weight, or 15% or more by weight, or 20% or more by weight, or 25% or more by weight, or 30% or more by weight, or 35% or more by weight, or 40% or more by weight, or 45% or more by weight, while at the same time having a solid content of 50% or less by weight, or 45% or less by weight, or 40% or less by weight, or 35% or less by weight, or 30% or less by weight, or 25% or less by weight, or 20% or less by weight, or 15% or less by weight, or 10% or less by weight.

[0038] The thickener contains 30% to 70% by weight of ethyl acrylate units based on the total weight of the thickener. For example, the thickener may contain 30% or more by weight of ethyl acrylate, or 35% or more by weight of ethyl acrylate, or 40% or more by weight of ethyl acrylate, or 50% or more by weight of ethyl acrylate, or 55% or more by weight of ethyl acrylate, or 60% or more by weight, or 65% or more by weight, based on the total weight of the thickener, while simultaneously containing 70% or less by weight of ethyl acrylate, or 65% or less by weight, or 60% or less by weight, or 55% or less by weight, or 50% or less by weight, or 45% or less by weight, or 40% or less by weight, or 35% or less by weight.

[0039] The thickener contains 20% to 60% by weight of methacrylic acid-derived units based on the total weight of the thickener. For example, the thickener may contain 20% or more by weight, or 25% or more by weight, or 30% or more by weight, or 35% or more by weight, or 40% or more by weight, or 45% or more by weight, or 50% or more by weight, or 55% or more by weight, while simultaneously containing 60% or less by weight, or 55% or less by weight, or 50% or less by weight, or 45% or less by weight, or 40% or less by weight, or 35% or less by weight, or 30% or less by weight, or 25% or less by weight of methacrylic acid-derived units.

[0040] The thickener contains units derived from functional monomers. Functional monomers have structure (I)

[0041] [ka] (In the formula, m is the average value from 10 to 40, and n is the average value from 5 to 30). The values ​​of m and n in structure (I) are: 13 It is determined using ¹¹C nuclear magnetic resonance. The m of structure (I) may have an average value of 10 or more, or 12 or more, or 14 or more, or 16 or more, or 18 or more, or 20 or more, or 22 or more, or 24 or more, or 26 or more, or 28 or more, or 30 or more, or 32 or more, or 34 or more, or 36 or more, or 38 or more, while at the same time having an average value of 40 or less, or 38 or less, or 36 or less, or 34 or less, or 32 or less, or 30 or less, or 28 or less, or 26 or less, or 24 or less, or 22 or less, or 20 or less, or 18 or less, or 16 or less, or 14 or less, or 12 or less. n in structure (I) may have an average value of 5 or more, or 6 or more, or 8 or more, or 10 or more, or 12 or more, or 14 or more, or 16 or more, or 18 or more, or 20 or more, or 22 or more, or 24 or more, or 26 or more, or 28 or more, while simultaneously having an average value of 30 or less, or 28 or less, or 26 or less, or 24 or less, or 22 or less, or 20 or less, or 18 or less, or 16 or less, or 14 or less, or 12 or less, or 10 or less, or 8 or less, or 6 or less.

[0042] The thickener may contain 1% to 20% by weight of functional monomers based on the total weight of the thickener. For example, the thickener may contain 1% or more by weight, or 2% or more by weight, or 4% or more by weight, or 6% or more by weight, or 8% or more by weight, or 10% or more by weight, or 12% or more by weight, or 14% or more by weight, or 16% or more by weight, or 18% or more by weight, while simultaneously containing 20% ​​or less by weight, or 18% or less by weight, or 16% or less by weight, or 14% or less by weight, or 12% or less by weight, or 10% or less by weight, or 8% or less by weight, or 6% or less by weight, or 4% or less by weight, or 2% or less by weight of functional monomers.

[0043] The thickening agent may be dissolved in a solvent to form a thickening agent solution, which may then be added to the shutdown composition as the thickening agent solution. The solvent used to dissolve the thickening agent may be water or another solvent. Lithium hydroxide may be added to the thickening agent solution to adjust the pH of the solution to a desired value. The pH of the thickening agent solution may be 7.0 or higher, or 7.2 or higher, or 7.4 or higher, or 7.6 or higher, or 7.8 or higher, or 8.0 or higher, or 8.1 or higher, or 8.2 or higher, or 8.4 or higher, or 8.6 or higher, or 8.8 or higher, while simultaneously being 9.0 or lower, or 8.8 or lower, or 8.6 or lower, or 8.4 or lower, or 8.2 or lower, or 8.0 or lower, or 7.8 or lower, or 7.6 or lower, or 7.4 or lower, or 7.2 or lower.

[0044] The shutdown composition includes a binder. The binder helps to bind the materials of the shutdown composition after the shutdown composition has been deposited on a separator and dried to form a shutdown layer. The binder may contain one or more of polybutyl acrylate and styrene-butadiene rubber.

[0045] The shutdown composition may contain 0.1% to 7% by weight of binder, based on the total weight of the shutdown composition. For example, the shutdown composition may contain 0.1% or more by weight, or 0.5% or more by weight, or 1% or more by weight, or 2% or more by weight, or 3% or more by weight, or 4% or more by weight, or 5% or more by weight, or 6% or more by weight, while simultaneously containing 7% or less by weight, or 6% or less by weight, or 5% or less by weight, or 4% or less by weight, or 3% or less by weight, or 2% or less by weight, or 1% or less by weight, or 0.5% or less of binder.

[0046] The binder may be added to the shutdown composition as a solid or emulsion. In the example where the binder is an emulsion, the binder emulsion may have a solid content of 20% to 60% by weight based on the total weight of the binder emulsion. For example, the binder emulsion may be 20% or more by weight, or 25% or more by weight, or 30% or more by weight, or 35% or more by weight, or 40% or more by weight, or 45% or more by weight, or 50% or more by weight, or 55% or more by weight, while at the same time being 60% or less by weight, or 55% or less by weight, or 50% or less by weight, or 45% or less by weight, or 40% or less by weight, or 35% or less by weight, or 30% or less by weight, or 25% or less by weight. In the example where the binder is added to the shutdown composition as a binder emulsion, the shutdown composition may contain 1% to 10% by weight of the binder emulsion based on the total weight of the shutdown composition. For example, the shutdown composition may contain, based on the total weight of the shutdown composition, 1% or more by weight, or 2% or more by weight, or 3% or more by weight, or 4% or more by weight, or 5% or more by weight, or 6% or more by weight, or 7% or more by weight, or 8% or more by weight, or 9% or more by weight, while simultaneously containing 10% or less by weight, or 9% or less by weight, or 8% or less by weight, or 7% or less by weight, or 6% or less by weight, or 5% or less by weight, or 4% or less by weight, or 3% or less by weight, or 2% or less by weight of a binder emulsion.

[0047] The shutdown composition may include one or more additives or auxiliary polymers, such as acrylic emulsion polymers, vinyl acrylic emulsion polymers, styrene acrylic emulsion polymers, vinyl acetate ethylene emulsion polymers, and combinations thereof; one or more fillers; one or more catalysts, wetting agents, defoamers, flowing agents, release agents, slip agents, antiblocking agents, additives for masking sulfide contamination, pigment wetting / dispersing agents, antisettling agents; one or more cosolvents, such as glycols, glycol ethers, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, alcohols, mineral spirits, aromatic solvents, and benzoic acid esters; one or more dispersants, such as amino alcohols and polycarboxylates; one or more surfactants; one or more preservatives, such as biocides, fungicides, bactericides, algaecides, and combinations thereof; or one or more additional neutralizing agents, such as hydroxides, amines, ammonia, and carbonates; and optionally one or more solvents or fusion aids. In specific examples, the shutdown composition may contain a highly branched secondary alcohol ethoxylate surfactant in an amount ranging from 0.1% to 1% by weight, or 0.2% to 0.8% by weight, or 0.3% to 0.5% by weight, based on the total weight of the shutdown composition. A commercially available example of a highly branched secondary alcohol ethoxylate surfactant is TRITON® HW-1000, manufactured by The Dow Chemical Company (Midland Michigan). In another specific example, the shutdown composition may contain a highly branched secondary alcohol ethoxylate surfactant in an amount ranging from 0.05% to 1% by weight, or 0.1% to 0.5% by weight, or 0.15% to 0.3% by weight, based on the total weight of the shutdown composition.

[0048] The shutdown composition may be applied to a substrate (e.g., a separator) by various methods. For example, the shutdown layer can be formed by roller coating, spray coating, powder coating, dip coating, electrodeposition coating, printing, wash coating, flow coating, curtain coating, etc. The thickness of the shutdown layer may be in the range of 1 micrometer (μm) to 25 μm. For example, the thickness of the shutdown layer may be 1 μm or more, or 2 μm or more, or 3 μm or more, or 4 μm or more, or 5 μm or more, or 10 μm or more, or 15 μm or more, or 20 μm or more, while at the same time being 25 μm or less, or 20 μm or less, or 15 μm or less, or 10 μm or less, or 5 μm or less, or 4 μm or less, or 3 μm or less, or 2 μm or less.

[0049] The shutdown composition may be applied to the separator and then dried by a conventional drying method to form a shutdown layer. Such conventional drying methods include, but are not limited to, air drying, convection oven drying, hot air drying, and / or infrared oven drying. [Examples]

[0050] material The following materials were used to form the comparative example ("CE") and the embodiment of the present invention ("IE").

[0051] Polyethylene is a polyethylene resin with a density of 0.91 g / cc and a melt index (190°C / 2.16 kg) of 15 g / 10 min, and is commercially available from The Dow Chemical Company (Midland, MI) as Dow ELITE® 5815.

[0052] EMAA is ethylene methacrylic acid with a methacrylic acid content of 15% by weight, a density of 0.94 g / cc, a melt index (190°C / 2.16 kg) of 60 g / 10 min, and a neutralization rate of 0%. It is commercially available from The Dow Chemical Company (Midland, MI) as Dow NUCREL® 960.

[0053] The fatty acids used have 18 or more carbon atoms, a melting point of 80°C, and an acid value (mgKOH / g sample) of 135-160. They are commercially available from Voelpker Co. (Volpke, Germany) under the trade name WARADUR® Montan wax.

[0054] KOH is analytical grade potassium hydroxide available from Sinopharm Chemical Reagent Co. (Shanghai, China).

[0055] SBR is a styrene-butadiene rubber latex binder, and is commercially available as BM-451B (Zeon Corp. (Tokyo, Japan)).

[0056] The thickening agent solution is 1.5 wt% copolymer in water (EA, MAA, and functional monomer copolymer containing 49.9 wt% EA, 39.9 wt% MAA, and 10.2 wt% structure(I) [wherein m has an average value of 20 and n has an average value of 16-18]) based on the total weight of the thickening agent solution neutralized to a pH of about 8 using LiOH.

[0057] WA is a highly branched wetting agent marketed as TRITON® HW-1000 by The Dow Chemical Company (Midland, Michigan, USA).

[0058] HDPE is a 12 μm thick high-density polyethylene separator available from Shenzhen Senior Technology Material Co., Ltd. (Shenzhen, China).

[0059] The cathode material was Ni-Co-Mn(NCM)S740B, purchased from Rongbai Company (Yuyao, China).

[0060] The anode material was graphite FSN-1 purchased from Shanshan Company (Shanghai, China).

[0061] The electrolyte was a 9:1 mixture of carbonate solvent and LiPF6, purchased from Guangzhou Tianci Company (Guangdong, China).

[0062] Sample preparation Preparation and application of shutdown coatings Polyolefin dispersions were prepared by feeding polyethylene and fatty acids into a specially designed twin-screw extruder ("TSE") with a back pressure of approximately 2 megapascals ("MPa"). Polyethylene and dispersant (83.33 g / min of HDPE DMDA8965 and 4.58 g / min of montanic acid) were melted and blended with injected KOH solution (30% by weight, 1.74 mL / min, 100% neutralization of montanic acid) and a small amount of initial water (1.9 mL / min) in the TSE at a temperature of 160°C and a screw rotation speed of 400 rpm ("rpm"). A high internal phase emulsion (HIPE) was formed during this process, and was then diluted with water (120 mL / min) to a solid content of approximately 50% by weight. After cooling the dispersion to below 100°C, a polyolefin dispersion with a particle size of 0.7–1 μm and a solid content of 50% by weight was recovered.

[0063] An EMAA dispersion was prepared by injecting EMAA into a TSE at a rate of 33.33 g / min under a back pressure of approximately 2 MPa. The TSE was operated at a temperature of 150°C and a screw rotation speed of 500 rpm. The melted EMAA was blended several times in the TSE with the injected KOH solution (30% by weight, 2.61 mL / min, resulting in an EMAA dispersion with a neutralization rate of 31%) and a small amount of initial water (14.3 mL / min) at a temperature of 150°C and a screw rotation speed of 500 rpm. A high internal phase emulsion (HIPE) was formed during this process and then diluted to approximately 20% by weight with water (120 mL / min). After cooling the emulsion to below 100°C, a 20% by weight solids EMAA dispersion with a particle size of 0.2–0.3 μm was collected.

[0064] The shutdown dispersion was prepared according to the composition shown in Table 1, by adding the polyolefin dispersion, EMAA dispersion, thickener, binder, and water in the order shown. The mixture was prepared in a 150 mL plastic vial with a cap and mixed in a SpeedMixer DAC 150 mixer at 1500 rpm for 5 minutes.

[0065] [Table 1]

[0066] Lithium-ion battery assembly A replica of a pouch-cell type LIB with a capacity of 100 milliampere-hours was selected, and its thermal response performance was evaluated. The cathode, separator, and anode were manually stacked and then placed in a plastic-aluminum bag. Connectors were attached separately to the cathode and anode. This sample was transferred to a vacuum oven and dehydrated at 80°C for 24 hours. Two milliliters of electrolyte were injected, and the plastic-aluminum bag was then sealed in a heat compressor. The battery was mounted on a Landian battery charge / discharge unit, and the battery formation process was performed to start the battery.

[0067] Test method Thermal response performance test: Lithium-ion battery samples were tested for electrical resistance using a Hioki Battery HiTester BT 3562 before and after being placed in a 115°C oven.

[0068] Calculation of neutralization rate: The neutralization rate ("DoN") of EMAA in the repair dispersion can be determined by the following formula.

[0069]

number

[0070] result The results of the thermal response performance test are shown in Table 2.

[0071] [Table 2]

[0072] Referring to Table 2, CE1 and IE1-IE3 clearly show that the introduction of a shutdown layer fabricated from the composition can effectively shut down lithium ion transport within the battery, as evidenced by the significant increase in resistance despite no large difference in the resistance of the sample before heating. CE1 shows that when EMAA is not included in the formation of the shutdown layer, the resistance after heating is only a fraction of the value obtained by IE1-IE3, which includes EMAA. Such results indicate that defects and holes are not effectively sealed. IE1 shows that including EMAA in the composition reduces Li ion transport during heating and creates an effective shutdown layer. IE2 and IE3 show that the electrical resistance increased to 127.6 ohms and 257 ohms, respectively, after heating, indicating that EMAA content affects electrical resistance, with higher EMAA content resulting in higher electrical resistance during heating.

Claims

1. A composition, A polyolefin dispersion of one or more polyolefins having a melting point of 80°C to 130°C and an average particle size of 0.5 microns to 5 microns, A repair dispersion comprising an ethylene methacrylate copolymer ("EMAA") having a melting point of 80°C to 120°C and an average particle size of 0.1 microns to 1 micron, wherein the EMAA copolymer is neutralized to a degree of 0% to 40%, Furthermore, the composition wherein the weight ratio of the EMAA to the polyolefin in the composition is 1:100 to 10:

100.

2. The composition according to claim 1, wherein the polyolefin and the EMAA are each dispersed in water.

3. The composition according to any one of claims 1 and 2, wherein the repair dispersion has a solid content of 5% to 40% by weight based on the total weight of the repair dispersion, and the polyolefin dispersion has a solid content of 30% to 70% by weight based on the total weight of the polyolefin dispersion.

4. The composition according to any one of claims 1 to 3, wherein the polyolefin is selected from the group consisting of ethylene, ethylene-propylene copolymer, ethylene-butylene copolymer, ethylene-hexene copolymer, and ethylene-octene copolymer.

5. The composition according to any one of claims 1 to 4, wherein the polyolefin exhibits a melting temperature of 100°C to 120°C.

6. The composition according to any one of claims 1 to 5, wherein the weight ratio of the EMAA to the polyolefin in the composition is 3:100 to 5:

100.

7. The composition according to any one of claims 1 to 6, wherein the polyolefin exhibits a melting temperature of 100°C to 110°C.

8. The composition according to any one of claims 1 to 7, wherein the EMAA contains 4% to 20% by weight of methacrylic acid based on the total weight of the EMAA.

9. The composition according to claim 8, wherein the EMAA copolymer is neutralized by 20% to 40%.

10. A composition according to any one of claims 1 to 9, Binder and, Wetting agent, A shutdown composition comprising a thickening agent.

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