Capsule binder, binder composition, diaphragm and battery

Abstract

The invention provides a capsule binder, a binder composition, a diaphragm and a battery in order to solve the problems of easy powder falling and poor thermal safety of a diaphragm binder in the prior art. The capsule binder comprises a core body and a polymer layer which is arranged on the outer surface of the core body and at least partially covers the core body, and the core body comprises a phase change material; the polymer layer comprises a polymer, and the polymer comprises an acrylate structural unit, a hydrophilic functional structural unit and a crosslinking structural unit; the mass ratio of the phase change material to the acrylate structural unit to the hydrophilic functional structural unit to the crosslinking structural unit is (40-60): (20-40): (1-5): (5-20). According to the capsule binder provided by the invention, the phase-change material is introduced into the core body, and when the internal temperature of the battery rapidly rises to the phase-change temperature of the core body, the phase-change material absorbs heat to slow down the temperature rise, so that the possibility of a thermal runaway accident is reduced, and the safety performance of the secondary battery is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of secondary batteries, and in particular relates to a capsule binder, a binder composition, a diaphragm and a battery. Background Art

[0002] Lithium-ion batteries are mainly composed of positive electrode, negative electrode, separator, electrolyte and battery shell. When charging, external voltage is applied to the two poles of the battery. + Lithium ions are deintercalated from the positive electrode material, enter the electrolyte, and then pass through the separator to the negative electrode, reversing the path during discharge. As a crucial component of lithium-ion batteries, the separator separates the positive and negative electrodes to prevent short circuits while allowing lithium ions to move freely during charge and discharge, ensuring energy storage and release. The performance of the separator directly impacts battery performance, including internal resistance, cycle life, and safety. Currently, separators in lithium-ion power batteries are mostly made of polyolefins, such as polypropylene / polyethylene double-layer composite separators or polypropylene / polyethylene / polypropylene three-layer composite separators. However, these separators have limited high-temperature resistance. Lithium-ion batteries generate heat during charge and discharge, especially at high rates or in extreme ambient temperatures. When abnormal heat release occurs, the separator can shrink, leading to a short circuit between the positive and negative electrodes and potentially causing safety hazards such as thermal runaway. Uneven temperatures or sustained temperature rise during charge and discharge can accelerate electrode material aging and thicken the SEI film, potentially leading to capacity fade and shortened battery life.

[0003] In existing technologies, heat-resistant coatings are applied to one or both sides of polyolefin separators to improve the heat resistance of the separator, thereby enhancing the safety performance of lithium-ion batteries. However, the binders in the heat-resistant coatings have problems such as easy powder shedding and poor heat resistance. Secondly, phase change materials (PCMs) have become ideal materials for battery thermal management due to their unique characteristics of latent heat storage and isothermal regulation. Phase change materials absorb or release large amounts of latent heat during the phase change process without causing changes in the ambient temperature. They can achieve passive temperature control without the need for external energy and can absorb large amounts of heat in the early stages of thermal runaway in lithium-ion batteries, buying time for the safety system to respond.

[0004] Therefore, there is an urgent need to provide an adhesive with good heat resistance, strong bonding strength and high phase change latent heat to improve the thermal safety performance of the diaphragm. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the problem that the existing diaphragm adhesive is easy to shed powder and has poor thermal safety. The present invention provides a capsule adhesive, an adhesive composition, a diaphragm and a battery.

[0006] In order to solve the above technical problems, the present invention provides a capsule binder, which includes a core body and a polymer layer arranged on the outer surface of the core body and at least partially covering the core body, wherein the core body includes a phase change material; the polymer layer includes a polymer, and the polymer includes an acrylate structural unit, a hydrophilic functional structural unit and a cross-linked structural unit; the mass ratio of the phase change material, the acrylate structural unit, the hydrophilic functional structural unit and the cross-linked structural unit is (40~60):(20~40):(1~5):(5~20).

[0007] Preferably, the phase change temperature of the capsule binder is 25-90° C.; the phase change latent heat value of the capsule binder is greater than 150 KJ / kg.

[0008] Preferably, the electrolyte mass swelling rate of the capsule binder is less than 40%.

[0009] Preferably, the glass transition temperature of the polymer is -40~20°C.

[0010] Preferably, the phase change material includes one or more of C18~C50 straight-chain alkanes, C12~C20 fatty acids, and C12~C30 fatty alcohols; and the hydrophilic functional structural units include one or more of acrylic structural units or hydroxy acrylate structural units.

[0011] The present invention also provides a binder composition comprising a heat-resistant binder and the capsule binder as described above, wherein the mass ratio of the heat-resistant binder to the capsule binder is (30-50): (50-70).

[0012] Preferably, the binder composition has a tensile strength of 0.5-40 MPa, an elongation at break of 50%-500%, and an electrolyte mass swelling ratio of less than 30%.

[0013] Preferably, the glass transition temperature of the heat-resistant adhesive is greater than 100°C.

[0014] The present invention also provides a diaphragm, comprising a base film and a functional layer disposed on at least one side of the base film, wherein the functional layer comprises ceramic particles and the binder composition as described above.

[0015] The present invention also provides a battery comprising the separator as described above.

[0016] The capsule binder provided in this application incorporates a phase-change material within the core. When the internal temperature of the battery rapidly rises to the core's phase-change temperature, the phase-change material absorbs heat and slows the temperature rise, reducing the possibility of thermal runaway accidents and improving the safety performance of the secondary battery. The capsule binder's adhesive properties are enhanced by introducing acrylate structural units, hydrophilic functional structural units, and cross-linking structural units into the polymer layer.

[0017] In particular, the combined use of an encapsulated binder and a heat-resistant binder ensures that the functional layer of the resulting separator has high adhesion while also improving the separator's resistance to heat shrinkage. Furthermore, the binder composition, through the introduction of the encapsulated binder, also possesses thermal buffering properties, absorbing heat during battery charging and discharging, reducing the possibility of thermal runaway accidents and improving battery safety. Furthermore, no organic solvents are added during the separator preparation process, making the binder composition environmentally friendly and harmless. DETAILED DESCRIPTION

[0018] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0019] One embodiment of the present application provides a capsule binder, which includes a core body and a polymer layer arranged on the outer surface of the core body and at least partially covering the core body, wherein the core body includes a phase change material; the polymer layer includes a polymer, and the polymer includes an acrylate structural unit, a hydrophilic functional structural unit, and a cross-linked structural unit; the mass ratio of the phase change material, the acrylate structural unit, the hydrophilic functional structural unit, and the cross-linked structural unit is (40~60):(20~40):(1~5):(5~20).

[0020] The capsule binder provided in this application incorporates a phase-change material within the core. When the internal temperature of the battery rapidly rises to the phase-change temperature of the core, the phase-change material absorbs heat and slows the temperature rise, reducing the possibility of thermal runaway accidents and improving the safety performance of the secondary battery. The capsule binder's adhesive properties are enhanced by introducing acrylate structural units, hydrophilic functional structural units, and cross-linked structural units into the polymer layer. By limiting the mass ratio of the phase-change material to the structural units in the polymer layer, the capsule binder's heat absorption capacity is increased. By limiting the mass ratio of the various structural units in the polymer layer, the capsule binder's adhesive properties are improved.

[0021] Specifically, the mass ratio of the phase change material, the acrylate structural unit, the hydrophilic functional structural unit and the cross-linking structural unit includes but is not limited to 40:20:1:5, 60:40:5:20, 40:40:5:20, 40:40:5:20, 40:20:5:20, 40:40:1:20, 40:40:5:5, 50:30:3:10, 40:30:5:20, 40:40:3:10, 40:30:3:20 or 40:40:3:20.

[0022] In some embodiments, the phase change temperature of the capsule binder is 25-90° C.; and the phase change latent heat value of the capsule binder is greater than 150 KJ / kg.

[0023] Specifically, the phase change temperature of the capsule binder includes but is not limited to 25° C., 30° C., 40° C., 50° C., 60° C., 70° C., 80° C., and 90° C. The phase change latent heat value of the capsule binder is 150-250 KJ / kg.

[0024] In some embodiments, the electrolyte mass swelling ratio of the capsule binder is less than 40%.

[0025] In some embodiments, the phase change temperature of the phase change material is between 25°C and 90°C; and / or the phase change latent heat of the phase change material is greater than 150 kJ / kg. By limiting the phase change temperature to this range, the binder has a wide temperature buffering and control capability, improving the reliability of the capsule binder in complex temperature environments. By limiting the phase change latent heat of the phase change material to this range, the capsule binder can achieve a significant thermal buffering effect with a relatively small amount of use.

[0026] In some embodiments, the phase change material includes one or more of C18~C50 straight-chain alkanes, C12~C20 fatty acids, and C12~C30 fatty alcohols; and the hydrophilic functional structural units include one or more of acrylic structural units or hydroxy acrylate structural units.

[0027] Specifically, the phase change material includes at least one of phase change wax, palmitic acid, stearic acid, and n-tetradecanol.

[0028] In some embodiments, the hydrophilic functional structural units include one or more of acrylic acid units or hydroxyacrylate units. These units are derived from the polymerization of hydrophilic monomers. Specifically, the hydrophilic monomers include acrylic acid monomers or hydroxyacrylate monomers. Specifically, the hydrophilic monomers include at least one of acrylic acid, methacrylic acid, vinyl acrylic acid, β-acryloxypropionic acid, maleic acid, itaconic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, and hydroxybutyl acrylate. By selecting these hydrophilic monomers in the polymer layer, the bonding strength between the polymer layer and the metal oxide or ceramic particles is enhanced, while also promoting the dispersion and dissolution of the capsule binder in water.

[0029] In a preferred embodiment, the hydrophilic monomer is selected from at least one of acrylic acid, maleic acid, and hydroxyethyl acrylate.

[0030] In some embodiments, the polymer has a glass transition temperature (Tg) of -40°C to 20°C. By limiting the glass transition temperature of the polymer, the adhesive strength of the capsule binder can be regulated. When the glass transition temperature of the polymer is higher than 20°C, the adhesive performance of the capsule binder decreases.

[0031] In some embodiments, the acrylate structural unit is a structural unit obtained by polymerization of an acrylate monomer, and the acrylate monomer includes at least one of n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, isooctyl acrylate, isobornyl acrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate, and isobornyl methacrylate. By selecting the above acrylate monomers, the adhesive properties of the polymer layer are improved, the peel strength of the separator is further enhanced, and the flexibility of the polymer layer is adjusted.

[0032] In a preferred embodiment, the acrylic acid ester monomer is selected from at least one of isooctyl acrylate, n-butyl acrylate, isooctyl methacrylate, and isobornyl acrylate.

[0033] In some embodiments, the cross-linking structural unit is a structural unit obtained by polymerization of a cross-linking monomer. Specifically, the number of functional groups in the cross-linking monomer is at least 2.

[0034] The crosslinking monomer includes at least one of divinyl aromatic hydrocarbon compounds, diol diacrylate compounds, bisphenol A diacrylate, azacycloalkane diacrylate compounds, diol dimethacrylate compounds, bisphenol A dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, and pentaerythritol tetraacrylate. The selection of these crosslinking monomers allows for the formation of a three-dimensional network structure within the polymer layer, thereby increasing the tensile strength of the capsule binder, reducing the mass swelling rate of the capsule binder in the electrolyte, and improving solvent resistance.

[0035] Furthermore, the divinyl aromatic hydrocarbon compound includes at least one of divinylbenzene, divinyltoluene and divinylxylene.

[0036] The diol diacrylate compound includes at least one of ethylene glycol diacrylate, polyethylene glycol diacrylate, propylene glycol diacrylate, dipropylene glycol diacrylate, polyethylene glycol monomethyl ether acrylate, ethylene glycol dicyclopentenyl ether acrylate, and 1,4-butanediol diacrylate.

[0037] Bisphenol A diacrylate includes ethoxylated bisphenol A diacrylate.

[0038] The azacycloalkane diacrylate compounds include 1,4-diacryloylpiperazine.

[0039] The diol dimethacrylate compound includes at least one of polyethylene glycol dimethacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, and dipropylene glycol dimethacrylate.

[0040] In a preferred embodiment, the crosslinking monomer is selected from divinylbenzene.

[0041] One embodiment of the present invention further provides a method for preparing a capsule binder, comprising the following steps: Add phase change material, vinyl monomer, acrylate monomer, hydrophilic monomer, crosslinking monomer and initiator into a reactor, heat, the difference between the heating temperature and the phase change temperature of the phase change material is greater than 5°C, and stir until the phase change wax is completely dissolved to obtain an oil phase mixture; Add polyvinyl alcohol (PVA) or polyvinyl pyrrolidone (PVP) dispersant and water into a reactor, heat and stir at 85°C until completely dissolved, and obtain an aqueous phase mixture. The oil phase mixture is mixed with the water phase mixture and dispersed into a suspension at high speed by a homogenizer; The suspension was heated to 80° C. under a nitrogen atmosphere to carry out polymerization reaction for 6 h to obtain a capsule binder.

[0042] As known to those skilled in the art, the reactions in the above steps are conventional free radical polymerization, etc., and the specific methods and reaction conditions are free radical polymerization methods commonly used in the prior art, which will not be described in detail in the present invention.

[0043] The initiator includes one or more of sodium persulfate, ammonium persulfate, potassium persulfate, tert-butyl hydroperoxide, azobisisobutyronitrile, benzoyl peroxide (BPO), benzoyl peroxide / sucrose, tert-butyl hydroperoxide / rongalite, tert-butyl hydroperoxide / sodium metabisulfite, benzoyl peroxide / N,N-dimethylaniline, ammonium persulfate / sodium bisulfite, potassium persulfate / sodium bisulfite, hydrogen peroxide / tartaric acid, hydrogen peroxide / rongalite, ammonium persulfate / ferrous sulfate, hydrogen peroxide / ferrous sulfate, benzoyl peroxide / N,N-diethylaniline, benzoyl peroxide / ferrous pyrophosphate, potassium persulfate / silver nitrate, persulfate / thiol, cumene hydroperoxide / ferrous chloride, potassium persulfate / ferrous chloride, hydrogen peroxide / ferrous chloride, and cumene hydroperoxide / tetraethyleneimine.

[0044] One embodiment of the present invention further provides an adhesive composition comprising a heat-resistant adhesive and any of the above-described capsule adhesives, wherein the mass ratio of the heat-resistant adhesive to the capsule adhesive is (30-50):(50-70). The heat-resistant adhesive comprises one or more of polyacrylic acid, polyacrylonitrile, polyacrylamide, and polyvinyl alcohol. By limiting the mass ratio of the heat-resistant adhesive to the capsule adhesive to within the above range, the adhesive composition exhibits high bonding strength, high temperature resistance, and good thermal buffering properties.

[0045] In some embodiments, the binder composition has a tensile strength of 0.5-40 MPa, an elongation at break of 50%-500%, and an electrolyte mass swelling ratio of less than 30%.

[0046] The combined use of an encapsulated binder and a heat-resistant binder imparts high adhesion to the functional layer of the resulting separator while also improving the separator's resistance to heat shrinkage. Furthermore, the binder composition, through the introduction of the encapsulated binder, also possesses thermal buffering properties, absorbing heat during battery charging and discharging, reducing the likelihood of thermal runaway accidents and improving battery safety. Furthermore, no organic solvents are added during the separator preparation process, making the binder composition environmentally friendly and harmless.

[0047] Furthermore, the glass transition temperature of the heat-resistant adhesive is greater than 100°C.

[0048] It can be understood that, based on 100% of the binder composition, the mass content of the heat-resistant binder is 30% to 50%, and the mass content of the capsule binder is 50% to 70%.

[0049] One embodiment of the present invention further provides a separator, comprising a base film and a functional layer disposed on at least one side of the base film, wherein the functional layer comprises ceramic particles and the binder composition as described above. Specifically, the base film is a polyolefin film.

[0050] Furthermore, the slurry for preparing the functional layer includes ceramic particles, a binder composition, an additive and a solvent, the solvent is water, and the additive includes at least one of a wetting agent, a defoaming agent and an anti-settling agent.

[0051] The wetting agent includes one of sulfate ester salts, sulfonates, and acetylene glycol wetting agents, and is preferably an acetylene glycol wetting agent Surfdol 610.

[0052] The defoaming agent includes one of polyether, silicone and mineral oil defoaming agents, preferably the mineral oil defoaming agent DF691.

[0053] Anti-settling agents include sodium carboxymethylcellulose, preferably CMC1220.

[0054] Specifically, based on weight parts, the slurry for preparing the functional layer includes 800-100 parts of ceramic particles, 5-10 parts of the binder composition, 0.5-3 parts of a wetting agent, 0.5-1 parts of a defoaming agent, 0.5-3 parts of an anti-settling agent and 230-300 parts of water.

[0055] An embodiment of the present invention further provides a battery, comprising the separator as described above.

[0056] The present invention is further described below with reference to the following examples.

[0057] The capsule binder, binder composition, and separator disclosed in the present invention are specifically described.

[0058] Example 1 1) Capsule binder Add 50 parts of phase change wax (Zhongjia, ZJ-PCM-A-62), 30 parts of isooctyl acrylate, 10 parts of divinylbenzene, 3 parts of acrylic acid, and 1 part of BPO initiator into the reactor and stir at 65°C until the phase change wax is completely dissolved to obtain an oil phase mixture; 15 parts of PVA1788 dispersant and water were added to the reactor, heated and stirred at 85°C until completely dissolved to obtain an aqueous phase mixture; The oil phase mixture and the water phase mixture are dispersed into a suspension at high speed by a homogenizer; The suspension was heated to 80° C. under a nitrogen atmosphere to carry out polymerization reaction for 6 h to obtain a capsule binder.

[0059] The mass ratio of the phase change material, the acrylic ester structural unit, the hydrophilic functional structural unit and the cross-linking structural unit in the capsule binder is m1:m2:m3:m4.

[0060] 2) Binder composition The mass ratio of the capsule binder to the polyacrylic acid in the binder composition is 1:1.

[0061] 3) Diaphragm 100 parts of ceramic particles, 250 parts of deionized water, 2 parts of anti-settling agent CMC1220, 1 part of wetting agent Surfdol 610, and 1 part of defoaming agent DF 691 were added to a high-speed mixer. After stirring for 30 minutes, 8 parts of the adhesive composition were added according to the proportion. After 30 minutes, the material was discharged. The obtained slurry was coated on a polyolefin base film and rolled up to obtain a diaphragm.

[0062] Example 2 to Example 12 Most of the steps of Examples 2 to 12 are the same as those of Example 1, except that the components of the capsule binder are different, as shown in Table 1.

[0063] Table 1 Example 13 to Example 15 Most of the steps of Examples 13 to 15 are the same as those of Example 1, except that the components of the adhesive composition are different, as shown in Table 2. The heat-resistant adhesive can be purchased or synthesized.

[0064] Table 2 Comparative Example 1 to Comparative Example 12 Most of the steps of Comparative Examples 1 to 12 are the same as those of Example 1, except that the components of the capsule binder are different, as shown in Table 1.

[0065] Comparative Example 13 to Comparative Example 16 Most of the steps of Comparative Examples 13 to 16 are the same as those of Example 1, except that the binder compositions are different, as shown in Table 2.

[0066] Performance testing: The capsule binders, binder compositions, and diaphragms prepared in the above examples and comparative examples were subjected to the following tests.

[0067] 1) Tensile strength: The capsule binders and binder compositions obtained in the Examples and Comparative Examples were sampled in accordance with the national standard GB / T 528 "Determination of tensile stress-strain properties of vulcanized or thermoplastic rubber". After drying, they were cut into 1A dumbbell-shaped specimens (test length 20.0±0.5 mm, thickness 2.0±0.2 mm). The tensile strength was tested using an electronic tensile testing machine (Dongguan Dazhong Instrument Co., Ltd., Model DZ 101) at a rate of 50 mm / min.

[0068] 2) Electrolyte Swelling Rate: The capsule binders and binder compositions obtained in the Examples and Comparative Examples were each formed into films, cut into pieces, and weighed (m1). The films were then immersed in an electrolyte (EC:EMC:DEC = 3:5:2, 1 mol / L LiPF6) at 60°C for 72 h. The films were removed and the residual electrolyte on the film surface was wiped clean with a cloth. The film was then weighed again (m2), and the change in the test swelling rate was calculated.

[0069] Swelling degree = [(m2-m1) / m1]*100%.

[0070] 3) Testing method for phase transition temperature and phase transition latent heat: The capsule binders obtained in the examples and comparative examples were dried and then tested for phase transition temperature and phase transition latent heat using a DSC 3500 Sirius thermal analyzer.

[0071] 4) Heat Cycle Test: The capsule binders obtained in the Examples and Comparative Examples were sealed and heated 300 times at 25°C for 30 minutes, then at 90°C for 30 minutes, and finally at 25°C for 30 minutes. Samples were then dried and the latent heat of phase change was measured using a DSC 3500 Sirius thermal analyzer.

[0072] 5) Adhesion strength was tested by cutting the separators prepared in the examples and comparative examples into 30×100 mm pieces, using 30 mm wide 3M tape, and testing the adhesion strength using an electronic tensile testing machine (Dongguan Dazhong Instrument Co., Ltd., Model DZ 101).

[0073] 6) Heat shrinkage resistance was tested by cutting the separators prepared in the Examples and Comparative Examples into 100 × 100 mm pieces, placing them between two A4 sheets of paper, and then placing them on an iron plate. The plates were then transferred to a 150°C oven and baked for 1 hour. The changes in the longitudinal width (MD) and transverse width (TD) before and after testing were measured.

[0074] 7) The test method for air permeability time is: use Gurley air permeability instrument for detection.

[0075] The test results obtained from the examples and comparative examples are shown in Table 3 and Table 3.

[0076] Table 3 Table 3 The test results in Table 3 show that the capsule binder prepared from the phase change material, acrylate structural units, hydrophilic functional structural units and cross-linked structural units of the present invention has the characteristics of low swelling, high bonding and high latent heat (>150 J / g). When used as a binder composition with a heat-resistant binder, it has a lower swelling rate and higher tensile strength. When used for coating ceramic diaphragms, it can not only effectively bond the ceramic and the base film (bonding strength >40 N / m), but also improve the heat shrinkage resistance of the diaphragm under high temperature conditions of 150°C (<3%), and does not affect the air permeability of the diaphragm. The air permeability time is maintained within 210s / 100ml. The introduction of phase change materials and heat-resistant binders without affecting the lithium ion transmission of the diaphragm greatly improves the thermal safety performance of the diaphragm.

[0077] It can be seen from the test results in Table 3 that the phase change latent heat of the capsule binder is not only related to the type of phase change material, but also the ratio change between monomers will also have a great influence on the phase change latent heat; from Example 2, Example 3, Comparative Example 5, and Comparative Example 6 to Example 1 and Comparative Example 1, it can be seen that when the proportion of phase change material decreases, the phase change latent heat value of the capsule binder drops to below 150 J / g, which will lead to a decrease in the effect of passive temperature control; and when the proportion of phase change material is too high and the proportion of polymer shell is too small, although the material has a higher latent heat value, the proportion of shell is too low, and the tensile strength of the capsule is poor, resulting in a high risk of shell rupture and phase change material overflow, and the prepared binder composition has poor bonding performance, and there is a risk of material falling when used for ceramic diaphragm coating.

[0078] It can be seen from Example 4, Example 5, Comparative Example 7, Comparative Example 8, Comparative Example 1, and Comparative Example 2 that the acrylate structural unit is mainly used to adjust the Tg and adhesion of the capsule material. If the amount of the acrylate structural unit is too low, the Tg of the capsule is too high, the adhesion performance is reduced, and the thermal shrinkage performance of the diaphragm at 150°C deviates; if the amount of the acrylate structural unit is too high, the latent heat value of the capsule binder is reduced, and the swelling is increased, which will result in additional electrolyte consumption and affect the long-term cycle of the battery.

[0079] It can be seen from Example 6, Example 7, Comparative Example 9, Comparative Example 10, Comparative Example 1, and Comparative Example 3 that the introduction of a hydrophilic functional structural unit can improve the reaction and storage stability of the capsule binder. If the dosage is too low, the reaction system is unstable and gelation may occur during storage. If the dosage is too high, excessive viscosity and agglomeration may occur during the synthesis process.

[0080] It can be seen from Example 8, Example 9, Comparative Example 11, Comparative Example 12, Comparative Example 1 and Comparative Example 4 that the cross-linked monomer structural unit has a significant effect on the swelling and tensile strength of the capsule binder; if the amount of the cross-linked monomer structural unit is too low, the tensile strength of the capsule binder is reduced, the swelling is increased, the capsule structure is at risk of damage, and the Tg is too low, the heat resistance of the capsule binder itself is reduced, resulting in an increase in the air permeability time of the diaphragm and a decrease in the heat resistance shrinkage performance at 150°C; if the amount is too high, the cross-linking degree is too high, the capsule bonding performance is reduced, and the comprehensive performance of the diaphragm deviates.

[0081] It can be seen from Examples 13 to 15, Comparative Example 1, and Comparative Examples 13 to 16 that the adhesive composition formed by compounding the heat-resistant adhesive and the capsule adhesive in a certain proportion, as the proportion of the heat-resistant adhesive increases, the prepared ceramic diaphragm has a lower thermal shrinkage rate at 150°C. When the dosage is too high, the bonding performance of the ceramic coating decreases, there is a risk of powder falling, and the air permeability time of the prepared ceramic diaphragm increases significantly, affecting the lithium ion transmission efficiency of the battery; if the dosage of the heat-resistant adhesive is too low, the prepared ceramic diaphragm has a high thermal shrinkage rate at 150°C and the heat resistance of the diaphragm is reduced.

[0082] 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 in the scope of protection of the present invention.

Claims

1. A capsule binder, characterized in that: The capsule binder includes a core body and a polymer layer arranged on the outer surface of the core body and at least partially covering the core body, wherein the core body includes a phase change material; the polymer layer includes a polymer, and the polymer includes an acrylate structural unit, a hydrophilic functional structural unit and a cross-linked structural unit; the mass ratio of the phase change material, the acrylate structural unit, the hydrophilic functional structural unit and the cross-linked structural unit is (40~60): (20~40): (1~5): (5~20).

2. The capsule binder according to claim 1, characterized in that The phase change temperature of the capsule binder is 25-90° C.; the phase change latent heat value of the capsule binder is greater than 150 KJ / kg.

3. The capsule binder according to claim 1, characterized in that The electrolyte mass swelling rate of the capsule binder is less than 40%.

4. The capsule binder according to any one of claims 1 to 3, characterized in that The glass transition temperature of the polymer is -40 to 20°C.

5. The capsule binder according to claim 4, characterized in that The phase change material includes one or more of C18-C50 straight-chain alkanes, C12-C20 fatty acids, and C12-C30 fatty alcohols; the hydrophilic functional structural units include one or more of acrylic structural units or hydroxy acrylate structural units.

6. A binder composition, characterized in that The invention comprises a heat-resistant adhesive and the capsule adhesive according to any one of claims 1 to 5, wherein the mass ratio of the heat-resistant adhesive to the capsule adhesive is (30-50): (50-70).

7. The adhesive composition according to claim 6, characterized in that The binder composition has a tensile strength of 0.5-40 MPa, an elongation at break of 50%-500%, and an electrolyte mass swelling rate of less than 30%.

8. The adhesive composition according to claim 6, characterized in that The glass transition temperature of the heat-resistant adhesive is greater than 100°C.

9. A diaphragm, characterized in that: The invention comprises a base film and a functional layer arranged on at least one side of the base film, wherein the functional layer comprises ceramic particles and the adhesive composition according to any one of claims 6 to 8.

10. A battery, characterized in that: The diaphragm according to claim 9 is included.

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