A polymer binder and its preparation method, a ceramic membrane coating slurry, a ceramic membrane, and a battery.

Abstract

This invention provides a polymer binder and its preparation method, a ceramic separator coating slurry, a ceramic separator, and a battery. The polymer binder comprises a core polymer and a shell polymer; the shell polymer coats a portion of the outer surface of the core polymer, and the glass transition temperature of the shell polymer is greater than that of the core polymer. The preparation method comprises (1) mixing a first raw material monomer and a first auxiliary agent, dispersing them, and then polymerizing them at a higher temperature to obtain a dispersion containing core polymer particles; (2) swelling the dispersion containing core polymer particles, a second raw material monomer, and a second auxiliary agent, and then polymerizing them at a higher temperature to obtain the polymer binder. The polymer binder of this invention possesses both high thermal stability and high adhesion, and the battery prepared thereby exhibits good thermal stability and electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material technology, specifically relating to a polymer binder and its preparation method, a ceramic separator coating slurry, a ceramic separator, and a battery. Background Technology

[0002] Among numerous energy storage devices, lithium batteries are widely used in digital products, automobiles, and everyday consumer goods due to their advantages such as light weight, long lifespan, and high energy density. Typically, each lithium battery consists of a cathode, anode, separator, and electrolyte. While the separator does not directly participate in the battery's electrochemical reaction, it is an indispensable part of current liquid lithium-ion batteries. Its main function is to physically isolate the positive and negative electrodes, preventing direct contact and short circuits. Therefore, the separator should not curl or shrink at high temperatures. This requires the separator to have sufficient mechanical strength to withstand the stress during manufacturing and assembly, as well as sufficient thermal stability to maintain structural integrity at high temperatures and prevent direct contact between the positive and negative electrodes.

[0003] Currently, polyolefin materials are commonly used as separators due to their high chemical stability and high porosity. However, polyolefin materials also have certain drawbacks. First, they have poor thermal stability, a low melting point, and a high thermal shrinkage rate at high temperatures, which can cause the positive and negative electrodes to come into direct contact and short-circuit due to separator shrinkage. Second, they have poor wettability to the electrolyte, affecting ion transport and negatively impacting battery rate performance and cycle life.

[0004] In recent years, technologies such as surface grafting, surface coating, and multifunctional manufacturing have been used to develop high-safety, high-performance lithium-ion battery separators. Among these, surface coating modification of traditional polyolefin separators using ceramic materials and organic polymers is one of the most effective methods to improve the thermal stability of the separator. High-heat-resistant and mechanically strong ceramic particles are used as modifiers, and organic polymers are used as binders. The resulting mixture is coated onto the polyolefin separator, improving its thermal stability and electrolyte wettability. During the ceramic coating modification process, the binder is used to bond the ceramic particles, ensuring they do not detach from the separator. Simultaneously, the binder can also directly bond the separator and electrodes, maintaining the stability of the separator / electrode interface during battery cycling, thereby suppressing the increase in impedance. Currently, the most commonly used binder in ceramic coating is polyvinylidene fluoride (PVDF) and its copolymers.

[0005] PVDF's adhesive network, formed by weak van der Waals forces, provides only limited bonding strength. Furthermore, oil-soluble adhesives like PVDF require expensive and environmentally unfriendly organic solvents such as N-methylpyrrolidone during application. Water-based adhesives, such as sodium carboxymethyl cellulose, styrene-butadiene rubber (SBR), and polyvinyl alcohol (PVA), are environmentally friendly. However, SBR and PBR, like PVDF, are linear in shape, forming a dense film after coating. While SBR is granular, its nanoscale size poses a risk of clogging the pores of the nanomembrane. In addition, polymer adhesives are prone to deformation at higher temperatures, resulting in a loss of bonding performance and significantly reduced adhesive strength; while high-heat-resistant polymer adhesives offer limited bonding strength.

[0006] In summary, current polymer binders suffer from problems such as insufficient adhesion leading to an increased distance between the diaphragm and the electrode, and the difficulty in simultaneously achieving high thermal stability and high adhesion. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this application is to provide a polymer binder with both high thermal stability and high adhesion, as well as a preparation method thereof, a ceramic membrane coating slurry with good thermal stability and electrochemical performance, a ceramic membrane, and a battery.

[0008] To achieve this objective, the present invention employs the following technical solution:

[0009] In a first aspect, this application provides a polymer binder applicable to battery separators. The polymer binder comprises a core polymer and a shell polymer; the shell polymer coats a portion of the outer surface of the core polymer, and the glass transition temperature of the shell polymer is greater than that of the core polymer.

[0010] In this application, the polymer binder used in a battery separator includes a core polymer and a shell polymer. The core polymer is approximately spherical, and the shell polymer is distributed on the outer surface of the core polymer, partially coating the outer surface of the core polymer. That is, there are gaps between adjacent shell polymer particles. Overall, the polymer binder resembles the shape of a raspberry. Figure 1The glass transition temperature of the shell polymer is higher than that of the core polymer, meaning the polymer binder exhibits a structure with a softer core and a harder outer shell. During the separator winding process, the shell polymer particles hinder the adhesion of the core to the separator, effectively preventing contact between separators and thus avoiding adhesion between them during winding, facilitating subsequent use of the separator. During battery hot pressing, the core overflows to achieve bonding, and the polymer binder firmly adheres to the separator and electrode. Simultaneously, the outer shell undergoes slight deformation due to compression, causing the shell polymer particles to move closer together, forming a support structure. Furthermore, the shell polymer does not swell with the electrolyte, increasing the overall strength of the polymer particles and preventing deformation of the polymer binder under high temperature and pressure, which would affect its bonding performance. The raspberry-like structure enables the binder to provide high adhesion strength, with a hot-press peel strength exceeding 20 N / m, while also maintaining high thermal stability, with a thermal decomposition temperature above 280°C. This demonstrates that the polymer binder of this application effectively resolves the contradiction between high adhesion strength and high thermal stability.

[0011] In this application, the polymer binder has a particle size of 1-10 μm. With a particle size greater than 1 μm, the polymer binder ensures it will not clog the nanoscale pores of the separator, while simultaneously allowing direct adhesion between the separator and electrode within a ceramic coating of a few micrometers, thus better maintaining the stability of the separator / electrode interface and suppressing the increase in impedance during cycling. With a particle size less than 10 μm, the polymer binder will not increase the ion transport path due to excessively large spacing between the separator and electrode, thereby affecting ion transport efficiency.

[0012] In this application, the mass ratio of the shell polymer to the core polymer is 1:(0.1-1). A mass ratio of 1:0.1 or higher ensures sufficient adhesive force. A mass ratio of 1:1 or lower ensures sufficient strength. However, if the mass ratio of the shell polymer to the core polymer is too large, the bonding area will be insufficient, affecting the bonding performance; if it is too small, the strength of the polymer adhesive will be insufficient.

[0013] In this application, the particle size ratio of the shell polymer to the core polymer is (0.05-0.5):(1-10). A ratio of 0.05:10 or higher ensures sufficient strength of the polymer binder; a ratio of 0.5:1 or lower ensures sufficient bonding area. If the particle size ratio of the shell polymer to the core polymer is too large, the bonding area will be insufficient, affecting the bonding performance; if it is too small, the strength of the polymer binder will be insufficient.

[0014] In this application, the glass transition temperature of the core polymer is between -70°C and 50°C. Below 50°C, the formation of a raspberry-like structure is favorable; above -70°C, sufficient thermal stability is ensured. However, if the glass transition temperature of the core polymer is too high, the formation of a raspberry-like structure is unfavorable; if it is too low, thermal stability is insufficient.

[0015] In this application, the swelling degree of the core polymer is 20%-150%. Above 20% ensures sufficient electrolyte retention to achieve good ionic conductivity; below 150% prevents the polymer binder from over-expanding due to excessive swelling, which would affect bonding performance. If the swelling degree of the core polymer is too low, the electrolyte retention and ionic conductivity will be insufficient; if it is too high, the polymer binder will over-expand due to excessive swelling, affecting bonding performance.

[0016] In this application, the glass transition temperature of the shell polymer is between 80°C and 250°C. Below 250°C, it prevents the core from overflowing during the battery hot-pressing process, thus affecting the bonding performance; above 80°C, it is conducive to the formation of a raspberry-like structure. However, if the glass transition temperature of the shell polymer is too high, it will hinder the core from overflowing during the battery hot-pressing process, affecting the bonding performance; if it is too low, it will be detrimental to the formation of a raspberry-like structure.

[0017] In this application, the swelling degree of the shell polymer is 1%-20%. Above 1% ensures sufficient electrolyte retention to achieve good ionic conductivity; below 20% prevents the polymer binder from excessively expanding due to excessive swelling, thus affecting adhesion performance. If the swelling degree of the shell polymer is too low, it affects ionic conductivity; if it is too high, the shell polymer will excessively expand due to excessive swelling, affecting adhesion performance.

[0018] Secondly, this application also provides a method for preparing a polymer adhesive, comprising the following steps:

[0019] (1) The first raw material monomer and the first auxiliary agent are mixed and dispersed, and then heated and polymerized to obtain a dispersion containing polymer particles with a core.

[0020] (2) The dispersion containing the polymer particles in the core, the second raw material monomer, and the second auxiliary agent are swollen and polymerized by heating to obtain a polymer binder.

[0021] The preparation method of the polymer binder in this application includes two steps. The first step is the preparation of the core polymer particles. The polymer particles prepared in this step can be immediately carried out in the second step, or they can be stored for a period of time after adding a stabilizer before carrying out the second step, which makes the production more flexible. The second step is the preparation of the raspberry-like polymer binder. This step involves adding the second raw material monomer and the second auxiliary agent at one time. Unlike the traditional continuous feeding, it does not require strict control of the feeding rate and time period. The feeding time and reaction time are more flexible and save production costs.

[0022] In this application, the rotation speed during the dispersion process in step (1) is 4000-15000 rpm, and the time is 10-20 min. This dispersion step can obtain monomer droplets of 1-10 μm, which, after polymerization, form core polymer particles of 1-10 μm. If the rotation speed is too high, the obtained monomer droplets will be too small, resulting in the core polymer particles being too small; if the rotation speed is too low, the obtained monomer droplets will be too large, resulting in the core polymer particles being too large. If the dispersion time is too short, the obtained monomer droplets will have an excessively large particle size distribution, resulting in the core polymer particles having an excessively large particle size distribution; if the dispersion time is too long, the obtained monomer droplets will contain many small-diameter droplets, resulting in the core polymer particles containing many small-diameter particles.

[0023] In this application, the polymerization temperature in step (1) is 70-85℃, and the time is 2-6 hours. Within this temperature range, the reaction can proceed at a suitable rate. If the temperature is too high, the reaction system is prone to explosive polymerization, posing a safety risk; if the temperature is too low, the reaction time is too long, resulting in low production efficiency. If the polymerization time is too short, the reaction will not proceed completely, and monomers will remain in the system; if the polymerization time is too long, the later reaction will be almost complete, the conversion rate will increase slowly, and the production efficiency will be low.

[0024] In this application, during the swelling process described in step (2), the second raw material monomer and the second auxiliary agent are embedded in the surface of the core polymer particles, partially coating the surface of the core polymer particles. The coating ratio is controlled by controlling the concentration of the crosslinking agent in step (1) and the amount of the second raw material monomer added in step (2). The higher the concentration of the crosslinking agent, the more surface shell particles there are, and the higher the coating ratio; at the same time, the more second raw material monomer is used, the more surface shell particles there are, and the higher the coating ratio.

[0025] In this application, the swelling temperature in step (2) is 10-30℃, and the time is 4-12h. If the swelling temperature is too low, the second raw material monomer will have difficulty entering the core polymer; if the swelling temperature is too high, the second raw material monomer will polymerize before entering the core polymer. If the swelling time is too low, the second raw material monomer cannot completely enter the core polymer particles; if the swelling time is too long, the swelling will reach equilibrium in the later stages, resulting in excessive time costs.

[0026] In this application, the polymerization temperature in step (2) is 65-80℃, and the time is 5-10h. The polymerization temperature is required to be higher than the core glass transition temperature and lower than the shell glass transition temperature. If the polymerization temperature is too high, the reaction system is prone to explosive polymerization, which poses a safety risk; if the polymerization temperature is too low, the reaction time is too long, resulting in low production efficiency. If the polymerization time is too low, the reaction will not proceed completely, and monomers will remain in the system; if the polymerization time is too long, the later reaction will be basically complete, the conversion rate will increase slowly, and the production efficiency will be low.

[0027] Preferably, after dispersion in step (1), deoxygenation is performed before polymerization at a higher temperature; the deoxygenation time is at least 30 minutes. More preferably, after swelling in step (2), deoxygenation is performed before polymerization at a higher temperature; the deoxygenation time is at least 30 minutes. The purpose of deoxygenation is to prevent free radicals released from the initiator during the reaction from combining with oxygen, thus hindering the polymerization of monomers initiated by free radicals and delaying the polymerization process.

[0028] In this application, the first raw material monomer includes a first monomer or a first crosslinking monomer. The first raw material monomer is used to prepare the core polymer and can be a monomer with a glass transition temperature and electrolyte swelling degree within a defined range, or a crosslinking monomer having at least two or more polymerization reactive functional groups.

[0029] Preferably, the first monomer is one or more selected from acrylates, methacrylates, vinyl chloride, vinyl acetate, acrylamide, methacrylamide, acrylonitrile, and methacrylonitrile.

[0030] More preferably, the acrylates include at least one of methyl acrylate, ethyl acrylate, butyl acrylate, and isooctyl acrylate;

[0031] More preferably, the methacrylates include at least one of methyl methacrylate and ethyl methacrylate;

[0032] Preferably, the first crosslinking monomer is one or more of diethyl methacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and divinylbenzene.

[0033] In this application, the second monomer may be a monomer with a glass transition temperature and electrolyte swelling degree within a defined range, and may be one or more of methyl methacrylate, ethyl methacrylate, and aromatic vinyl groups.

[0034] In this application, the first auxiliary agent includes an initiator, emulsifier, stabilizer, crosslinking agent, dispersant, and solvent; by mass parts, the first raw material monomer is 100 parts, the initiator is 0.5-2 parts, the emulsifier is 0.1-3 parts, the stabilizer is 0.1-10 parts, the crosslinking agent is 0.1-10 parts, the dispersant is 5-30 parts, and the solvent is 600-800 parts. According to the above proportions, a relatively stable pre-dispersion can be obtained after dispersion, and the polymerization reaction can proceed stably at a suitable rate during the reaction process.

[0035] The initiator is an oil-soluble initiator, which includes one or more of azodiethylbutyronitrile, benzoyl peroxide, and dilauryl peroxide.

[0036] The emulsifier includes one or more of sulfates, carboxylates, and sulfonates.

[0037] The stabilizer includes one or more of hexadecyl alcohol, hexadecane, and octadecyl methacrylate.

[0038] The crosslinking agent may be a monomer having at least two polymerization functional groups, and the monomer includes one or more of diethyl methacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and divinylbenzene.

[0039] The dispersant is one or more of polyvinyl alcohol, sodium hydroxymethyl cellulose, and polyacrylonitrile.

[0040] The solvent is water.

[0041] Preferably, the mass ratio of the second raw material monomer to the second auxiliary agent is (5-40):(0.05-0.4).

[0042] Preferably, the second auxiliary agent is a second initiator, which is one or more of azodiethylbutyronitrile, benzoyl peroxide, and dilauryl peroxide.

[0043] As a preferred technical solution of the present invention, the preparation method of the polymer binder includes the micro-suspension polymerization reaction in step (1) and the seed swelling polymerization reaction in step (2), and the specific steps are as follows:

[0044] Step (1) Mix the first raw material monomer, initiator, emulsifier, stabilizer, crosslinking agent, dispersant and solvent in a mass ratio of 100:(0.5-2):(0.1-3):(0.1-10):(0.1-10):(5-30):(600-800). Disperse the mixture in a homogenizer at a speed of 4000-15000 rpm for 10-20 min to obtain a pre-emulsion. Transfer the pre-emulsion to a container with a stirrer and pass an inert gas through it for at least 30 min under stirring. Heat the mixture to 70-85℃ and start polymerization. Maintain the reaction for 2-6 h to obtain a dispersion containing polymer particles with a core.

[0045] Step (2) Mix the dispersion containing the core polymer particles prepared in the first step, the second raw material monomer, and the second auxiliary agent. Stir and swell at 10-30℃ for 4-12 hours, then transfer to a container with a stirrer. Under stirring, introduce an inert gas to remove oxygen for at least 30 minutes. After heating to 65-80℃, start polymerization and maintain the reaction for 5-10 hours to obtain the polymer binder.

[0046] This application does not limit the inert gas; for example, the inert atmosphere may be at least one of argon and nitrogen.

[0047] Thirdly, this application also provides a ceramic diaphragm coating slurry, comprising a polymer binder and ceramic particles as described in the first aspect; or comprising a polymer binder and ceramic particles obtained by the preparation method described in the second aspect.

[0048] The ceramic particles in the ceramic diaphragm coating slurry provide heat resistance; the core polymer of the polymer binder has a high degree of swelling and the carbonyl groups it contains have a good affinity for the solvent in the electrolyte, thus exhibiting high ionic conductivity; the shell polymer of the polymer binder has high strength and does not swell in the electrolyte, thus providing high thermal stability and electrochemical stability.

[0049] Preferably, the mass ratio of polymer binder to ceramic particles is (5-20):(80-95). A mass ratio of 5:95 or higher ensures sufficient binder in the coating to guarantee the structural stability of the ceramic coating; a mass ratio of 20:80 or lower ensures sufficient porosity in the coating to achieve good ion transport.

[0050] Preferably, the ceramic particles have a particle size of 1-5 μm. A particle size of 1 μm or larger ensures that the ceramic particles will not clog the membrane pores; a particle size of less than 5 μm allows for better control of the ceramic coating thickness.

[0051] Preferably, the ceramic particles include one or more of alumina, silicon dioxide, silicon carbide, silicon nitride, magnesium silicate, magnesium hydroxide, barium titanate, and boehmite.

[0052] Fourthly, this application also provides a ceramic-coated diaphragm, comprising a polymer binder as described in the first aspect; or a polymer binder obtained by the preparation method described in the second aspect; or a ceramic diaphragm coating slurry as described in the third aspect.

[0053] Fifthly, this application also provides a battery comprising a polymer binder as described in the first aspect; or a polymer binder obtained by the preparation method described in the second aspect; or a ceramic membrane coating slurry as described in the third aspect; or a ceramic-coated membrane as described in the fourth aspect.

[0054] Compared with the prior art, this application has the following advantages:

[0055] This application provides a polymer binder for use in battery separators, having a raspberry-like shape, comprising a core polymer and a shell polymer, with the shell polymer partially coating the outer surface of the core polymer. The core is relatively soft and possesses good adhesion, while the shell is relatively hard and can improve the overall strength of the polymer particles. The polymer binder of this application can effectively resolve the contradiction between high adhesion and high thermal stability. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the raspberry-structured polymer binder in this application;

[0057] Figure 2 Scanning electron microscope (SEM) images of the polymer binders prepared in Examples 1-3 and Comparative Example 1 before heat treatment and after heat treatment at 100°C for 1.5 h.

[0058] Figure 3 Scanning electron microscope images of the polymer binders prepared in Examples 4-5 and Comparative Example 3;

[0059] Figure 4 Scanning electron microscope images of the polymer adhesives of Examples 6-9;

[0060] Figure 5 The cycling performance graphs are for the batteries prepared in Examples 18, 21, 5, and 6. Detailed Implementation

[0061] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0062] Example 1

[0063] A polymeric binder for membranes includes a core polymer and a shell polymer; the shell polymer coats a portion of the outer surface of the core polymer. The polymeric binder has a particle size of 3.83 μm; the mass ratio of the shell polymer to the core polymer is 0.25; the particle size ratio of the shell polymer to the core polymer is 0.24:3.59; the glass transition temperature of the core polymer is -40°C; the swelling degree of the core polymer is 100%; the glass transition temperature of the shell polymer is 100°C; and the swelling degree of the shell polymer is 3%.

[0064] The preparation method of the above polymer binder includes the micro-suspension polymerization reaction in step (1) and the seed swelling polymerization reaction in step (2), specifically:

[0065] Step (1) Take 100 parts of butyl acrylate as monomer, 1 part of benzoyl peroxide as initiator, 1 part of alkyl alcohol ether sulfate containing double bonds as emulsifier, 5 parts of octadecyl methacrylate as stabilizer, 5 parts of ethylene glycol dimethacrylate as crosslinking agent, 15 parts of polyvinyl alcohol as dispersant, and 700 parts of deionized water. Mix them and add them to a high-efficiency homogenizer. Disperse them at 10,000 rpm for 15 min. After uniform dispersion, transfer the dispersion to a pressure-resistant container with a stirring paddle. Purge with nitrogen for 0.5 h and then heat to 80 °C. React at a constant temperature for 6 h to obtain a seed emulsion (i.e., a dispersion containing polymer particles in the core).

[0066] Step (2) Take 100 parts of the above seed emulsion, add 3.4 parts of styrene as monomer and 0.034 parts of benzoyl peroxide as initiator at 30°C, stir and swell for 4 hours, then transfer to a pressure-resistant container with a stirring paddle, purge with nitrogen for 0.5 hours to raise the temperature to 65°C, and react at a constant temperature for 10 hours to obtain a polymer binder emulsion.

[0067] Example 2

[0068] A polymeric binder for membranes includes a core polymer and a shell polymer; the shell polymer coats a portion of the outer surface of the core polymer. The polymeric binder has a particle size of 3.80 μm; the mass ratio of the shell polymer to the core polymer is 0.15; the particle size ratio of the shell polymer to the core polymer is 0.21:3.59; the glass transition temperature of the core polymer is -40°C; the swelling degree of the core polymer is 100%; the glass transition temperature of the shell polymer is 100°C; and the swelling degree of the shell polymer is 3%.

[0069] The preparation method of the above polymer binder differs from that of Example 1 only in that: in step (2), 2 parts of styrene as a monomer and 0.02 parts of benzoyl peroxide as an initiator are added.

[0070] Example 3

[0071] A polymeric binder for membranes includes a core polymer and a shell polymer; the shell polymer coats a portion of the outer surface of the core polymer. The polymeric binder has a particle size of 3.71 μm; the mass ratio of the shell polymer to the core polymer is 0.08; the particle size ratio of the shell polymer to the core polymer is 0.12:3.59; the glass transition temperature of the core polymer is -40°C; the swelling degree of the core polymer is 100%; the glass transition temperature of the shell polymer is 100°C; and the swelling degree of the shell polymer is 3%.

[0072] The preparation method of the above polymer binder differs from that of Example 1 only in that: in step (2), 1 part of styrene as a monomer and 0.01 part of benzoyl peroxide as an initiator are added.

[0073] Comparative Example 1

[0074] A polymer binder for diaphragms comprises only a core polymer; wherein the particle size of the polymer binder is 3.59 μm; the glass transition temperature of the core polymer is -40°C; and the swelling degree of the core polymer is 110%.

[0075] The preparation method of the above polymer adhesive is as follows:

[0076] Take 100 parts of butyl acrylate as a monomer, 1 part of benzoyl peroxide as an initiator, 1 part of alkyl alcohol ether sulfate containing double bonds as an emulsifier, 5 parts of octadecyl methacrylate as a stabilizer, 5 parts of ethylene glycol dimethacrylate as a crosslinking agent, 15 parts of polyvinyl alcohol as a dispersant, and 700 parts of deionized water. Mix them and add them to a high-efficiency homogenizer. Disperse at 10,000 rpm for 15 min. After uniform dispersion, transfer the dispersion to a pressure-resistant container with a stirrer. Purge with nitrogen for 0.5 h and then heat to 80 °C. React at this temperature for 2 h to obtain a seed emulsion, i.e., a polymer binder emulsion.

[0077] Comparative Example 2

[0078] PVDF is used as the polymer binder.

[0079] The performance of the polymer adhesives prepared in Examples 1-3 and Comparative Example 1, and the PVDF adhesive in Comparative Example 2 were tested, and the data are shown in Table 1. The polymer adhesives prepared in Examples 1-3 and Comparative Example 1 were subjected to electron microscopy before heat treatment and after heat treatment at 100°C for 1.5 h, and the results are as follows. Figure 2 The image shown is a scanning electron microscope image.

[0080] Table 1. Performance test data of the polymer binders prepared in Examples 1-3 and Comparative Example 1, and the PVDF binder in Comparative Example 2.

[0081]

[0082] As can be seen from the data results of Examples 1-3 and Comparative Example 1 in Table 1, the polymer binder provided in this example exhibits the following effects: with the increase of the amount of the second raw material monomer added, the coating ratio of the shell polymer increases, the particle size of the binder slightly increases, the swelling degree decreases, the adhesion tends to weaken, the electrochemical window range increases, the degree of deformation after heat treatment decreases, and the thermal stability improves. The swelling degree, adhesion strength, and electrochemical stability of the PVDF binder in Comparative Example 2 are all lower than those of the polymer binders in Examples 1-3.

[0083] from Figure 2The data results of Examples 1-3 and Comparative Example 1 show that the polymer binders before heat treatment are all regular spheres. After heat treatment, the polymer binders of Examples 1 and 2 can maintain the spherical shape well, the polymer binder of Example 3 shows slight deformation, and the polymer binder of Comparative Example 1 shows obvious deformation. It can be seen that the shell polymer on the surface of the polymer binder can improve the spherical retention rate of the binder, and the more shell polymer there is, the higher the spherical retention rate of the polymer binder.

[0084] Example 4

[0085] A polymeric binder for membranes includes a core polymer and a shell polymer; the shell polymer coats a portion of the outer surface of the core polymer. The polymeric binder has a particle size of 2.50 μm; the mass ratio of the shell polymer to the core polymer is 0.15; the particle size ratio of the shell polymer to the core polymer is 0.10:2.40; the glass transition temperature of the core polymer is -40°C; the swelling degree of the core polymer is 100%; the glass transition temperature of the shell polymer is 100°C; and the swelling degree of the shell polymer is 3%.

[0086] The preparation method of the above polymer binder includes the micro-suspension polymerization reaction in step (1) and the seed swelling polymerization reaction in step (2), specifically:

[0087] Step (1) Take 100 parts of methyl methacrylate as monomer, 1 part of azodiethylbutadiene nitrile as initiator, 1 part of carboxylate as emulsifier, 5 parts of hexadecane as stabilizer, 5 parts of ethylene glycol dimethacrylate as crosslinking agent, 15 parts of sodium carboxymethyl cellulose as dispersant, and 700 parts of deionized water. Mix them and add them to a high-efficiency homogenizer. Disperse them at 13000 rpm for 10 min. After uniform dispersion, transfer the dispersion to a pressure-resistant container with a stirring paddle. Purge with nitrogen for 1 h and then heat to 80℃. React at a constant temperature for 2 h to obtain a seed emulsion (i.e., a dispersion containing polymer particles in the core).

[0088] Step (2) Take 100 parts of the above seed emulsion, add 2 parts of methyl methacrylate as monomer and 0.02 parts of benzoyl peroxide as initiator at 20°C, stir and swell for 6 hours, then transfer to a pressure-resistant container with a stirring paddle, purge with nitrogen for 0.5 hours to raise the temperature to 70°C, and react at a constant temperature for 5 hours to obtain a polymer binder emulsion.

[0089] Example 5

[0090] A polymeric binder for membranes includes a core polymer and a shell polymer; the shell polymer coats a portion of the outer surface of the core polymer. The polymeric binder has a particle size of 2.45 μm; the mass ratio of the shell polymer to the core polymer is 0.15; the particle size ratio of the shell polymer to the core polymer is 0.05:2.40; the glass transition temperature of the core polymer is -40°C; the swelling degree of the core polymer is 100%; the glass transition temperature of the shell polymer is 100°C; and the swelling degree of the shell polymer is 3%.

[0091] The preparation method of the above polymer adhesive differs from that of Example 4 only in that 2 parts of ethylene glycol dimethacrylate are added as a crosslinking agent.

[0092] Comparative Example 3

[0093] A polymeric binder for membranes includes a core polymer and a shell polymer; the shell polymer coats a portion of the outer surface of the core polymer. The polymeric binder has a particle size of 2.40 μm; the mass ratio of the shell polymer to the core polymer is 0.15; the particle size ratio of the shell polymer to the core polymer is 0:2.4; the shell polymer is contained within the core polymer, and there is no shell polymer on the surface of the core polymer; the glass transition temperature of the core polymer is -40°C; the swelling degree of the core polymer is 100%; the glass transition temperature of the shell polymer is 100°C; and the swelling degree of the shell polymer is 3%.

[0094] The preparation method of the above polymer adhesive differs from that of Example 4 only in that 0 parts of ethylene glycol dimethacrylate are added as a crosslinking agent.

[0095] Electron microscopy was performed on the polymer binders prepared in Examples 4-5 and Comparative Example 3 to obtain the following results: Figure 3 The image shown is a scanning electron microscope image. From Figure 3 As can be seen, during the preparation of seed emulsion, the higher the concentration of crosslinking agent, the more obvious the raspberry-like structure of the polymer binder.

[0096] Example 6

[0097] A polymer binder for membranes includes a core polymer and a shell polymer; the shell polymer coats a portion of the outer surface of the core polymer. The polymer binder has a particle size of 4.48 μm; the mass ratio of the shell polymer to the core polymer is 0.15; the particle size ratio of the shell polymer to the core polymer is 0.28:4.2; the glass transition temperature of the core polymer is -40°C; the swelling degree of the core polymer is 100%; the glass transition temperature of the shell polymer is 100°C; and the swelling degree of the shell polymer is 20%.

[0098] The preparation method of the above polymer binder includes the micro-suspension polymerization reaction in step (1) and the seed swelling polymerization reaction in step (2), specifically:

[0099] Step (1) Take 100 parts of methacrylamide as a monomer, 1 part of dilauryl peroxide as an initiator, 1 part of vinyl sulfonate as an emulsifier, 5 parts of cetyl alcohol as a stabilizer, 5 parts of diethylene glycol dimethacrylate as a crosslinking agent, 15 parts of polyacrylonitrile as a dispersant, and 700 parts of deionized water. Mix them and add them to a high-efficiency homogenizer. Disperse them at 8000 rpm for 20 min. After the dispersion is uniform, transfer the dispersion to a pressure-resistant container with a stirrer. Purge with nitrogen for 0.5 h and then heat to 80 °C. React at a constant temperature for 2 h to obtain a seed emulsion.

[0100] Step (2) Take 100 parts of the above seed emulsion, add 2 parts of p-methylstyrene as monomer and 0.02 parts of benzoyl peroxide as initiator at 10°C, stir and swell for 12 hours, then transfer to a pressure-resistant container with a stirring paddle, purge with nitrogen for 0.5 hours to raise the temperature to 80°C, and react at a constant temperature for 5 hours to obtain a polymer binder emulsion.

[0101] Example 7

[0102] A polymer binder for membranes includes a core polymer and a shell polymer; the shell polymer coats a portion of the outer surface of the core polymer. The polymer binder has a particle size of 4.48 μm; the mass ratio of the shell polymer to the core polymer is 0.15; the particle size ratio of the shell polymer to the core polymer is 0.28:4.2; the glass transition temperature of the core polymer is -40°C; the swelling degree of the core polymer is 100%; the glass transition temperature of the shell polymer is 100°C; and the swelling degree of the shell polymer is 20%.

[0103] The preparation method of the above polymer binder differs from that of Example 6 only in that the polymerization reaction temperature after swelling in step (2) is 70°C.

[0104] Example 8

[0105] A polymer binder for membranes includes a core polymer and a shell polymer; the shell polymer coats a portion of the outer surface of the core polymer. The polymer binder has a particle size of 4.48 μm; the mass ratio of the shell polymer to the core polymer is 0.15; the particle size ratio of the shell polymer to the core polymer is 0.28:4.2; the glass transition temperature of the core polymer is -40°C; the swelling degree of the core polymer is 100%; the glass transition temperature of the shell polymer is 100°C; and the swelling degree of the shell polymer is 20%.

[0106] The difference between the above-mentioned polymer adhesive preparation method and Example 6 is only that the swelling temperature in step (2) is 20°C and the time is h.

[0107] Example 9

[0108] A polymer binder for membranes includes a core polymer and a shell polymer; the shell polymer coats a portion of the outer surface of the core polymer. The polymer binder has a particle size of 4.48 μm; the mass ratio of the shell polymer to the core polymer is 0.15; the particle size ratio of the shell polymer to the core polymer is 0.28:4.2; the glass transition temperature of the core polymer is -40°C; the swelling degree of the core polymer is 100%; the glass transition temperature of the shell polymer is 100°C; and the swelling degree of the shell polymer is 20%.

[0109] The preparation method of the above polymer binder differs from that of Example 6 only in that the swelling temperature in step (2) is 20°C, the time is 6h, and the polymerization reaction temperature after swelling is 70°C.

[0110] Example 10

[0111] A polymer binder for membranes includes a core polymer and a shell polymer; the shell polymer coats a portion of the outer surface of the core polymer. The polymer binder has a particle size of 4.48 μm; the mass ratio of the shell polymer to the core polymer is 0.15; the particle size ratio of the shell polymer to the core polymer is 0.28:4.2; the glass transition temperature of the core polymer is -40°C; the swelling degree of the core polymer is 100%; the glass transition temperature of the shell polymer is 100°C; and the swelling degree of the shell polymer is 20%.

[0112] The preparation method of the above polymer binder differs from that of Example 6 only in that the polymerization temperature after dispersion in step (1) is 70°C.

[0113] Example 11

[0114] A polymer binder for membranes includes a core polymer and a shell polymer; the shell polymer coats a portion of the outer surface of the core polymer. The polymer binder has a particle size of 4.48 μm; the mass ratio of the shell polymer to the core polymer is 0.15; the particle size ratio of the shell polymer to the core polymer is 0.28:4.2; the glass transition temperature of the core polymer is -40°C; the swelling degree of the core polymer is 100%; the glass transition temperature of the shell polymer is 100°C; and the swelling degree of the shell polymer is 20%.

[0115] The preparation method of the above polymer binder differs from that of Example 6 only in that the polymerization temperature after dispersion in step (1) is 85°C.

[0116] The conversion rate data for each stage in the preparation process of the polymer binders in Examples 6-11 are shown in Table 2. Electron microscopy was performed on the polymer binders in Examples 6-9, and the results are as follows: Figure 4 The image shown is a scanning electron microscope image.

[0117] Table 2. Conversion rate data at each stage of the preparation process of the polymer binders in Examples 6-11.

[0118]

[0119] As shown in Table 2, decreasing the reaction temperature during the seed swelling stage reduces the reaction rate and the conversion rate achieved within the same time period, while changes in swelling temperature have a relatively small impact on the conversion rate. A comparison of the data from Examples 6, 10, and 11 shows that increasing the reaction temperature during the micro-suspension polymerization stage increases the reaction rate and the conversion rate achieved within the same time period.

[0120] from Figure 4 It can be seen that Example 7 lowered the polymerization reaction temperature after swelling in step (2) compared to Example 6, while Example 8 increased the swelling temperature in step (2) compared to Example 6. The results show that the small-diameter particles around the polymer binder obtained in Examples 7 and 8 were effectively reduced. Compared to Example 6, Example 9 simultaneously lowered the polymerization reaction temperature after swelling and increased the swelling temperature in step (2). The results show that there were almost no small-diameter particles around the polymer binder, and the purity of the product was greatly improved.

[0121] Examples 12-17

[0122] The preparation methods of the polymer binders in Examples 12-17 differ from those in Example 1 only in the amount of emulsifier, stabilizer and dispersant used in step (1). The specific amounts are detailed in Table 3, and all are parts by mass.

[0123] Table 3. Amounts of materials used in the preparation methods of polymer adhesives in Examples 12-17.

[0124] monomer Initiator emulsifier stabilizer Crosslinking agent dispersant Example 1 100 1 1 5 5 15 Example 12 100 1 0.1 5 5 15 Example 13 100 1 3 5 5 15 Example 14 100 1 1 0.1 5 15 Example 15 100 1 1 10 5 15 Example 16 100 1 1 5 5 5 Example 17 100 1 1 5 5 30

[0125] The performance of the polymer binders prepared in Examples 12-17 was tested, and the data are shown in Table 4. Table 4 shows that a comparison of the data from Examples 1, 12, and 13 indicates that increasing the emulsifier content reduces the particle size of the polymer seeds prepared in the micro-suspension polymerization stage. A comparison of the data from Examples 1, 14, and 15 shows that increasing the stabilizer content increases the stability of the dispersion in the micro-suspension polymerization stage, making it less prone to stratification. A comparison of the data from Examples 1, 16, and 17 shows that increasing the dispersant content increases the stability of the polymer seed emulsion prepared in the micro-suspension polymerization stage, making the polymer seeds less prone to sedimentation.

[0126] Table 4 Performance test data of the polymer binders prepared in Examples 12-17

[0127]

[0128]

[0129] Example 18

[0130] A ceramic diaphragm coating slurry comprises alumina particles and the polymer binder of Example 1, with a mass ratio of 90:10; wherein the alumina particles have a particle size of 3 μm. The preparation method involves mixing the polymer binder emulsion of Example 1, Al2O3 particles, and an appropriate amount of water, and mixing at 1000 rpm for 5 min to obtain the ceramic diaphragm coating slurry.

[0131] The above-mentioned ceramic diaphragm coating slurry was applied to the diaphragm surface by scraping and drying to obtain a ceramic-coated diaphragm. The polymer binder constituted 10% of the ceramic coating by weight, and the Al2O3 particles constituted 90% of the ceramic coating by weight.

[0132] Lithium-ion half-cells were prepared using the aforementioned ceramic-coated separator: CR2025 coin cells were assembled in a glove-shaped container filled with high-purity argon gas, stacking the electrode shell, graphite negative electrode, ceramic-coated separator, lithium metal counter electrode, and nickel foam in that order. A suitable amount of electrolyte was then added, and finally the counter electrode shell was placed on top and compacted. The electrolyte composition was 1 mol·L⁻¹ -1 The LiPF6 was dissolved in a solvent with a volume ratio of EC:DMC:EMC of 1:1:1. After battery assembly, the cells were allowed to stand for 12 hours before testing.

[0133] Examples 19-20

[0134] The ceramic diaphragm coating slurry in Examples 19-20 includes alumina particles and the polymer binder from Example 1, with mass ratios of 80:20 and 95:5, respectively; wherein the alumina particles have a particle size of 3 μm. The preparation method is the same as in Example 18.

[0135] The preparation methods for the ceramic-coated separator and the lithium-ion half-cell are the same as those in Example 18.

[0136] Example 21

[0137] A ceramic diaphragm coating slurry comprises magnesium hydroxide particles and the polymer binder of Example 2, with a mass ratio of 90:10; wherein the magnesium hydroxide particles have a particle size of 3 μm. The preparation method is the same as in Example 18.

[0138] The preparation methods for the ceramic-coated separator and the lithium-ion half-cell are the same as those in Example 18.

[0139] Example 22

[0140] A ceramic diaphragm coating slurry comprises silicon carbide particles and the polymer binder of Example 3, with a mass ratio of 90:10; wherein the silicon dioxide particles have a particle size of 3 μm. The preparation method is the same as in Example 18.

[0141] The preparation methods for the ceramic-coated separator and the lithium-ion half-cell are the same as those in Example 18.

[0142] Comparative Example 4

[0143] A ceramic diaphragm coating slurry comprises alumina particles and a polymer binder of Comparative Example 1, with a mass ratio of 90:10; wherein the alumina particles have a particle size of 3 μm. The preparation method is the same as in Example 18.

[0144] The preparation methods for the ceramic-coated separator and the lithium-ion half-cell are the same as those in Example 18.

[0145] Comparative Example 5

[0146] A ceramic diaphragm coating slurry comprises alumina particles and a polymer binder of Comparative Example 2, with a mass ratio of 90:10; wherein the alumina particles have a particle size of 3 μm. The preparation method is the same as in Example 18.

[0147] The preparation methods for the ceramic-coated separator and the lithium-ion half-cell are the same as those in Example 18.

[0148] Comparative Example 6

[0149] Lithium-ion half-cells were prepared using a PE separator: CR2025 coin cells were assembled in a glove-shaped container filled with high-purity argon gas, stacking the electrode shell, graphite negative electrode, PE separator, lithium metal counter electrode, and nickel foam in that order. A suitable amount of electrolyte was then added, and finally the counter electrode shell was placed on top and compacted. The electrolyte composition was 1 mol·L⁻¹ -1 The LiPF6 was dissolved in a solvent with a volume ratio of EC:DMC:EMC of 1:1:1. After battery assembly, the cells were allowed to stand for 12 hours before testing.

[0150] The ceramic-coated separators prepared in Examples 18-22 and Comparative Examples 4-5, as well as the batteries prepared in Examples 18-22 and Comparative Examples 4-6, were subjected to performance tests, and the data are shown in Table 5. Figure 5 The cycling performance graphs are for the batteries prepared in Examples 18, 21, 5, and 6.

[0151] Table 5 Performance test data of the batteries prepared in Examples 18-22 and Comparative Examples 4-6

[0152]

[0153] As can be seen from the data in Table 5, when the binder content in the separator coating is low, the thermal shrinkage rate, electrolyte retention rate, and ionic conductivity of the ceramic-coated separator all decrease, and the cycle stability of the battery decreases, with a very low capacity retention rate. A comparison of the data from Examples 19, 21, and 22 shows that when the proportion of shell polymer on the binder surface increases, i.e., the mass ratio of shell polymer to core polymer increases, the thermal shrinkage rate of the separator is effectively reduced, and the thermal stability is improved. However, the electrolyte retention rate and ionic conductivity decrease, and the initial capacity and capacity retention rate of the battery also decrease. A comparison of the data from Example 21, Comparative Example 5, and Comparative Example 6 shows that the ceramic-coated separator using the polymer binder described in this invention exhibits better thermal shrinkage rate, electrolyte retention rate, and ionic conductivity performance than the pure PE separator and the ceramic-coated separator using PVDF binder.

[0154] from Figure 5 The data shows that the battery cycle performance of Examples 18 and 21 is better than that of Comparative Examples 5 and 6. It can be seen that the ceramic-coated separator using the polymer binder in this example has better battery performance than the PE separator and the ceramic-coated separator using the PVDF binder.

[0155] Example 23

[0156] A ceramic diaphragm coating slurry comprises silica particles and the polymer binder of Example 6, with a mass ratio of 90:10; wherein the alumina particles have a particle size of 5 μm.

[0157] The preparation methods of the ceramic membrane coating slurry, the ceramic coated membrane, and the lithium-ion half-cell are all the same as those in Example 18.

[0158] Examples 24-29

[0159] The preparation methods of the polymer binders in Examples 24-29 differ from those in Example 6 only in that the dispersion rates in step (1) are 10000, 13000, 15000, 4000, 18000, and 3000 rpm, respectively.

[0160] The ceramic membrane coating slurry, the preparation method of the ceramic membrane coating slurry, the preparation method of the ceramic coated membrane, and the preparation method of the lithium-ion half-cell are all the same as in Example 23.

[0161] The performance of the batteries prepared in Examples 24-29 was tested, and the data are shown in Table 6. From the data in Table 6, it can be seen that the higher the dispersion rate in the micro-suspension polymerization stage of step (1), the smaller the particle size of the resulting polymer binder. As the dispersion rate in the micro-suspension polymerization stage of step (1) gradually increased from 3000 rpm to 18000 rpm, the particle size of the resulting polymer binder decreased from 12 μm to 0.5 μm. The adhesive force of the polymer binder showed a trend of first increasing and then decreasing. The thermal shrinkage of the obtained ceramic-coated separator first decreased and then increased, the ionic conductivity first increased and then decreased, and the initial capacity of the obtained lithium-ion half-cell first increased and then decreased, while the capacity retention first increased and then decreased. It can be seen that when the particle size of the polymer binder of the present invention is in the range of 1-10 μm, the polymer binder, ceramic-coated separator, and lithium-ion half-cell can exhibit optimal performance.

[0162] Table 6 Performance test data of the batteries prepared in Examples 24-29

[0163]

[0164] The specific testing methods for the data in the above embodiments of this application are as follows:

[0165] [Conversion rate during the reaction process]

[0166] The conversion rates of microsuspension polymerization and seed swelling polymerization were calculated using a gravimetric method. First, the mass of an empty weighing bottle was measured as m0. After the reaction was complete, a small amount of the reaction solution was transferred to the weighing bottle using a sampling needle, and the total weight was measured again as m1. Two drops of hydroquinone (0.5% by mass) as a polymerization inhibitor were added. The weighing bottle was then placed on a 60°C heating plate. After 6 hours, once most of the moisture had dried, it was transferred to a 60°C vacuum oven and dried thoroughly to constant weight. The mass of the dried product was then measured as m2. The conversion rate X was calculated.

[0167]

[0168] Where m mon Indicates the total weight of the added monomers, m all This indicates the total weight of all substances added during the reaction.

[0169] [Particle size of polymer binders]

[0170] The synthesized polymer binder emulsion was dropped into a particle size analyzer to obtain the particle size distribution and volume average particle size D of the polymer binder. 50 .

[0171] Peel strength of polymer adhesives

[0172] A polymer binder coating slurry with a 4% solids content was prepared and coated onto a 12μm thick PE separator using a wire rod and dried to obtain a polymer binder-coated separator (coating thickness 4-6μm). The coated separator was then bonded to the negative electrode and placed in a flatbed hot press at 85℃ and 2MPa for 60s to obtain a sample. One side of the sample was fixed to a steel plate with double-sided tape, and the separator was peeled from the electrode on a tensile testing machine to test the peel strength. The peel angle was 180° and the peel speed was 50mm / min. The maximum, minimum, and average peel forces F within the peel length were recorded, and the corresponding peel strength values ​​were calculated.

[0173]

[0174] In the formula: σ T — Peel strength, N / m; F — Peel force, N; B — Sample width, m.

[0175] During testing, samples from the same batch need to be measured in parallel three times, and the arithmetic mean of the three tests is taken as the test result.

[0176] High-Temperature Sphericity Retention of Polymer Binders

[0177] The synthesized polymer binder emulsion was coated onto the surface of the PE membrane, dried, and then divided into two portions. One portion was left untreated, while the other portion was heat-treated at 100℃ for 1.5 hours. The morphology and structure of the two samples were observed by SEM to compare the degree of deformation of the polymer binder before and after heat treatment.

[0178] [Thermal stability of polymer binders]

[0179] The thermal stability of the polymer was determined using a TA Q500 thermogravimetric analyzer. The tests were conducted under a nitrogen atmosphere, with a temperature range of 50–600 °C and a heating rate of 10 °C / min. -1 .

[0180] [Electrolyte Swelling Degree of Polymer Binders]

[0181] The synthesized polymer binder emulsion was injected into a polytetrafluoroethylene (PTFE) mold for film formation and dried overnight in an oven at 60°C. The resulting film was cut into 10mm round pieces to obtain test pieces, and the mass W1 of each test piece was measured. The test pieces were then immersed in an electrolyte at 25°C for 72 hours. Afterward, the test pieces were removed from the electrolyte, the electrolyte on their surface was wiped off, and the mass W2 of the immersed test pieces was measured. The corresponding electrolyte swelling value U = (W2 - W1) / W1 was calculated.

[0182] The product, used as an electrolyte, is a product in which LiPF6, as the supporting electrolyte, is dissolved relative to the solvent at a concentration of 1 mol / L in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) (volume mixing ratio: EC / EMC / DMC = 1 / 1 / 1).

[0183] [Electrochemical Window of Polymer Binders]

[0184] To evaluate the oxidative decomposition behavior of the polymer binder, Li / Li was subjected to oxidation at 0-6V. + Linear scanning voltammetry was performed within the voltage range at a scan rate of 1 mV·s. -1 Stainless steel is used as the working electrode and lithium metal is used as the counter electrode and reference electrode.

[0185] [Thermal shrinkage rate of ceramic-coated diaphragms]

[0186] The thermal shrinkage rate of the diaphragm was determined by measuring its dimensional change (based on area) after heat treatment at 130°C for 0.5 h.

[0187] [Electrolyte retention rate and ionic conductivity of ceramic-coated diaphragms]

[0188] To measure electrolyte absorption and ionic conductivity, the ceramic-coated separator was immersed in a 1M LiPF6 EC / EMC / DMC solution (volume ratio 1:1:1) at 25°C for 72 hours. Electrochemical impedance spectroscopy (EIS) was performed using an electrochemical workstation with an applied polarization voltage of 5mV, a test temperature of 25°C, and a test frequency range of 0.01–100kHz. The separator was then assembled into a CR2025 coin cell for testing. Both the positive and negative electrodes were stainless steel sheets, and the assembly process was completed in a glove box. During the test, an applied AC signal alternately charged the electrodes, causing lithium ions to move back and forth in the alternating field. The resistance to ion movement is called Re, i.e., bulk resistance. The conductivity of the GPE can be calculated from the measured bulk impedance: σ = d / (Re × S), where d represents the thickness of the coated separator, and S represents the area of ​​the stainless steel electrode.

[0189] [Cycle performance of lithium-ion half-cells]

[0190] A constant current charge-discharge test was performed on the lithium-ion half-cell using a battery testing system at a test temperature of 30°C. The voltage window was set to 0.01–1.5V, and the potential value was the Li / Li+ counter-potential. The number of charge-discharge cycles was set to 100. At 30°C, charge-discharge operations were performed at 0.2C to 0.01V and then at 0.2C to 1.5V, and the initial capacity C1 was measured. Then, at 30°C, the same charge-discharge conditions were repeated to measure the capacity C2 after 100 cycles. The capacity retention rate before and after cycling was then calculated as ΔC(%) = (C2 / C1) × 100%.

[0191] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A polymer adhesive for ceramic-coated diaphragms, characterized in that, The polymer binder includes a core polymer and a shell polymer; the shell polymer is partially embedded in the core polymer to cover a portion of the outer surface of the core polymer, and the glass transition temperature of the shell polymer is greater than that of the core polymer. The swelling degree of the core polymer is 20%-150%; The swelling degree of the shell polymer is 1%-20%; The mass ratio of the core polymer to the shell polymer is 1:(0.1-1); The preparation method of the polymer binder includes the following steps: (1) The first raw material monomer and the first auxiliary agent are mixed and dispersed, and then heated and polymerized to obtain a dispersion containing polymer particles with a core; (2) The dispersion containing the core polymer particles, the second raw material monomer, and the second auxiliary agent are swollen and polymerized by heating to obtain a polymer binder; During the swelling process described in step (2), the second raw material monomer and the second auxiliary agent are embedded in the surface of the core polymer particles; The first raw material monomer includes a first monomer and a first crosslinking monomer; The first monomer is one or more of the following: acrylates, methacrylates, vinyl chloride, vinyl acetate, acrylamide, methacrylamide, acrylonitrile, and methacrylonitrile; The second raw material monomer is one or more of methyl methacrylate, ethyl methacrylate, and aromatic vinyl groups; The swelling temperature in step (2) is 20-30℃, and the time is 4-12h; The polymerization temperature in step (2) is 65-70℃.

2. The polymer binder according to claim 1, characterized in that, The polymer binder has a particle size of 1-10 μm.

3. The polymer adhesive according to claim 1, characterized in that, The particle size ratio of the shell polymer to the core polymer is (0.05-0.5):(1-10).

4. The polymer adhesive according to claim 1, characterized in that, The glass transition temperature of the core polymer is -70°C to 50°C.

5. The polymer adhesive according to claim 1, characterized in that, The glass transition temperature of the shell polymer is between 80°C and 250°C.

6. The method for preparing the polymer adhesive according to any one of claims 1-5, characterized in that, Includes the following steps: (1) The first raw material monomer and the first auxiliary agent are mixed and dispersed, and then heated and polymerized to obtain a dispersion containing polymer particles with a core. (2) The dispersion containing polymer particles in the core, the second raw material monomer, and the second auxiliary agent are swollen and polymerized by heating to obtain a polymer binder; During the swelling process described in step (2), the second raw material monomer and the second auxiliary agent are embedded in the surface of the core polymer particles; The first raw material monomer includes a first monomer and a first crosslinking monomer; The first monomer is one or more of the following: acrylates, methacrylates, vinyl chloride, vinyl acetate, acrylamide, methacrylamide, acrylonitrile, and methacrylonitrile; The second raw material monomer is one or more of methyl methacrylate, ethyl methacrylate, and aromatic vinyl groups; The swelling temperature in step (2) is 20-30℃, and the time is 4-12h; The polymerization temperature in step (2) is 65-70℃.

7. The method for preparing the polymer adhesive according to claim 6, characterized in that, The rotation speed during the dispersion process in step (1) is 4000-15000 rpm, and the time is 10-20 min.

8. The method for preparing the polymer binder according to claim 6, wherein the polymerization temperature in step (1) is 70-85°C and the time is 2-6 hours.

9. The method for preparing the polymer binder according to claim 6, wherein the polymerization time in step (2) is 5-10 h.

10. The method for preparing the polymer binder according to claim 6, wherein after dispersion in step (1), deoxygenation treatment is performed, followed by heating and polymerization; the deoxygenation time is at least 30 min.

11. The method for preparing the polymer binder according to claim 6, wherein after swelling in step (2), deoxygenation treatment is performed, followed by heating and polymerization; the deoxygenation time is at least 30 min.

12. The method for preparing the polymer binder according to claim 6, wherein the first crosslinking monomer is a monomer having at least two or more polymerization reactive functional groups.

13. The method for preparing the polymer adhesive according to claim 12, wherein the first crosslinking monomer is one or more of diethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and divinylbenzene.

14. The method for preparing the polymer binder according to claim 6, wherein the first auxiliary agent comprises an initiator, an emulsifier, a stabilizer, a crosslinking agent, a dispersant, and a solvent; by mass parts, the first raw material monomer is 100 parts, the initiator is 0.5-2 parts, the emulsifier is 0.1-3 parts, the stabilizer is 0.1-10 parts, the crosslinking agent is 0.1-10 parts, the dispersant is 5-30 parts, and the solvent is 600-800 parts.

15. The method for preparing the polymer binder according to claim 6, wherein the mass ratio of the second raw material monomer to the second auxiliary agent is (5-40):(0.05-0.4).

16. The method for preparing the polymer adhesive according to claim 6, characterized in that, Includes the following steps: (1) Mix the first raw material monomer, initiator, emulsifier, stabilizer, crosslinking agent, dispersant and solvent in a mass ratio of 100:(0.5-2):(0.1-3):(0.1-10):(0.1-10):(5-30):(600-800). Disperse the mixture in a homogenizer at a speed of 4000-15000 rpm for 10-20 min to obtain a pre-emulsion. Transfer the pre-emulsion to a container with a stirrer and pass an inert gas through it for at least 30 min under stirring. Heat the mixture to 70-85℃ and start polymerization. Maintain the reaction for 2-6 h to obtain a dispersion containing polymer particles with a core. (2) Mix the dispersion containing the core polymer particles prepared in the first step, the second raw material monomer, and the second auxiliary agent. Stir and swell at 10-30℃ for 4-12 hours, then transfer to a container with a stirrer. Under stirring, introduce inert gas to remove oxygen for at least 30 minutes. After heating to 65-80℃, start polymerization and maintain the reaction for 5-10 hours to obtain the polymer binder.

17. A ceramic diaphragm coating slurry, characterized in that, Includes the polymer binder and ceramic particles as described in any one of claims 1-5; It may include polymer binders and ceramic particles obtained by the preparation method according to any one of claims 6-16.

18. The ceramic diaphragm coating slurry according to claim 17, characterized in that, The mass ratio of polymer binder to ceramic particles is (5-20):(80-95).

19. The ceramic diaphragm coating slurry according to claim 17, characterized in that, The ceramic particles have a particle size of 1-5 μm.

20. The ceramic diaphragm coating slurry according to claim 17, characterized in that, The ceramic particles include one or more of alumina, silicon dioxide, silicon carbide, silicon nitride, magnesium silicate, magnesium hydroxide, barium titanate, and boehmite.

21. A ceramic-coated diaphragm, characterized in that, Includes the polymer adhesive according to any one of claims 1-5; Or it may include a polymer binder obtained by the preparation method according to any one of claims 6-16; Or it may include the ceramic diaphragm coating slurry as described in any one of claims 17-20.

22. A battery, characterized in that, Includes the polymer adhesive according to any one of claims 1-5; Or it may include a polymer binder obtained by the preparation method according to any one of claims 6-16; Or it may include the ceramic diaphragm coating slurry as described in any one of claims 17-20; Or it may include the ceramic-coated diaphragm as described in claim 21.

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