Separators and batteries

Abstract

The application relates to the technical field of batteries, in particular to a separator and a battery. The separator comprises a base film and a ceramic layer; the ceramic layer is arranged on at least one side surface of the base film; the ceramic layer comprises ceramic and an adhesive, the adhesive is in a solid state at normal temperature, can be molten at a temperature greater than 130 DEG C, and has re-adhesion. When thermal abuse occurs, the ceramic layer can expand and fall off and transfer, the expansion can expand the spacing between the positive electrode and the negative electrode, the transfer to the positive electrode or the negative electrode can cover the positive electrode and the negative electrode, the occurrence of the short-circuit problem of the positive electrode and the negative electrode caused by the natural thermal shrinkage of the separator is compensated, and the thermal abuse passing rate of the high-voltage or high-energy-density battery is increased.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to separators and batteries. Background Technology

[0002] With the widespread use of lithium-ion batteries, separators are now mostly made of PE material, with melting points between 130 and 155°C. To increase the heat resistance of the separator, a ceramic layer is usually coated on one or both sides as a heat-resistant layer. The heat-resistant layer usually uses inorganic particles to increase the heat resistance temperature of the separator carrier, enabling the battery to withstand thermal abuse at 130°C or higher. However, as the voltage system increases to 4.45V, 4.48V, 4.5V or even higher 4.53V, and the volumetric energy density of the battery reaches 780Wh / L or above, the failure rate or complete failure of the battery increases during the 130°C thermal abuse test.

[0003] Research has found that when a battery is exposed to temperatures above 100°C, the separator inside the battery will undergo thermal shrinkage due to continuous heating. As the SEI and electrolyte decompose, an even greater heat source is generated, which can cause a short circuit between the positive and negative electrodes when the separator shrinks. This further amplifies the thermal runaway phenomenon, leading to open flames and combustion in the lithium-ion battery, followed by violent combustion. Summary of the Invention

[0004] In view of this, the present invention provides a separator and a battery. This separator can compensate for the short-circuiting problem of the positive and negative electrodes caused by the natural thermal shrinkage of the separator, and increase the thermal abuse pass rate of high-voltage or high-energy-density batteries.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] The present invention provides a diaphragm, the diaphragm comprising a base membrane and a ceramic layer; the ceramic layer is disposed on at least one surface of the base membrane;

[0007] The ceramic layer comprises ceramic and an adhesive that is solid at room temperature but melts at temperatures above 130°C and has re-adhesive properties.

[0008] The technical principle of this invention is as follows:

[0009] The ceramic layer of this invention comprises ceramic and an adhesive. The ceramic in the ceramic layer has a melting point above 1000°C, and will not melt even if the battery catches fire. When the battery reaches a certain temperature, the adhesive between the ceramics is kept at 130°C or above for a period of time (more than 30 minutes). Due to continuous heating, the adhesive between the ceramics undergoes a morphological transformation, changing from a solid to a liquid state. The ceramic layer of the separator expands and detaches, resulting in a larger gap between the positive and negative electrodes, thereby increasing the porosity between the positive and negative electrodes of the battery. This reduces the heat generated by internal self-discharge and promptly transports the heat generated inside the battery (such as the heat generated by electrolyte and SEI decomposition) to the battery cavity or directly to the outside of the battery through the battery opening for emergency heat dissipation. This compensates for the short circuit problem caused by the natural thermal shrinkage of the separator, increasing the thermal abuse pass rate of high-voltage or high-energy-density batteries, so as to achieve a 100% thermal abuse pass rate.

[0010] Preferably, the adhesive includes polyacrylate hot melt adhesive.

[0011] Preferably, the adhesive is polymerized from soft monomers, hard monomers, crosslinking monomers, flexible elastomers, a first tackifying resin, and a second tackifying resin.

[0012] Among them, soft monomers provide flexibility in adhesives, with a glass transition temperature below 0°C. The longer the carbon chain, the better the flexibility. Examples of long carbon chains include butyl acrylate and isooctyl acrylate. Hard monomers provide a rigid skeleton in adhesives (benzene rings and nitrile groups provide rigidity), with a glass transition temperature above 40°C. Both have very strong electrolyte adsorption capabilities, which is beneficial for increasing the Li ion passage rate in the ceramic layer, further improving the ionic conductivity of the separator, and enhancing the battery's performance related to rate charging / discharging. Crosslinking monomers provide crosslinking carboxylic acid groups, providing crosslinking points, crosslinking functional monomers, and also have very strong electrolyte resistance. Flexible elastomers provide both flexibility and skeletal rigidity, providing viscoelasticity and acting as skeletal chains. SBS has an electrolyte adsorption effect (soft polymer, unsaturated carbon-carbon double bonds adsorb electrolyte), which is beneficial for improving the ionic conductivity of the separator; SEBS has an electrolyte resistance effect (soft polymer, this polymer is all saturated bonds, resistant to electrolyte) and has good chemical and electrochemical stability. The working principle of the first and second tackifying resins: They have relatively small molecular weights, less than 1000, and mainly rely on hydrogen bonds, phenolic hydroxyl groups, carboxymethyl groups, carboxyl groups, ether bonds, etc. to form a hydrogen bond network structure with resins, rubbers, etc., thereby obtaining better adhesion. The addition of the first and second tackifying resins can further improve the adhesion of the composite membrane.

[0013] The adhesive of this invention has the function of expanding and transferring at high temperatures. When applied to the ceramic layer of the separator, it increases the distance between the positive and negative electrodes in the event of thermal abuse, which can quickly dissipate heat, prevent battery thermal runaway, and improve battery safety performance.

[0014] In embodiments of the present invention, the ceramic includes at least one selected from alumina, aluminum hydroxide, boehmite, silicon oxide, titanium oxide, and barium sulfate. The ceramic can improve the heat resistance of the separator, prevent thermal abuse, and enhance the safety performance of the battery.

[0015] Preferably, the ceramic has a melting point >1000℃.

[0016] In embodiments of the present invention, the adhesive further includes one or more of acrylic groups, acrylates, amide groups, carboxylic acid groups, and C=O double bonds.

[0017] In embodiments of the present invention, the mass of C=O double bonds in the adhesive accounts for 1% to 30% of the total mass of the adhesive. Exemplary values ​​are 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, and 30%. The C=O double bond content in the adhesive of the present invention falls within this range, enabling the adhesive to expand and transfer at high temperatures. In the event of thermal abuse, this increases the distance between the positive and negative electrodes, allowing for rapid heat dissipation, preventing battery thermal runaway, and improving battery safety performance. The preferred concentration is 1% to 25%.

[0018] Preferably, the mass ratio of ceramic to adhesive is (88%–97%).

[0019] (3%–12%). When the adhesive content exceeds 12%, the ceramic coating has a significant pore-blocking effect; when the adhesive content is less than 3%, the ceramic layer is prone to peeling off.

[0020] Preferably, the mass ratio of ceramic to adhesive is (90%–96%):(4%–10%).

[0021] Preferably, the diaphragm also includes an adhesive layer disposed on both sides of the base membrane; a ceramic layer is disposed between the base membrane and the adhesive layer.

[0022] In embodiments of the present invention, the adhesive layer includes at least one of PVDF (polyvinylidene fluoride), PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene), PMMA (polymethyl methacrylate), and PVA (polyvinyl alcohol), or a mixture thereof with inorganic substances. Because the molecular chains of oil-based coatings such as PVDF are in an extended state, compared to the coiled state in water-based coatings, they are easier to make thinner and have higher peel strength. This adhesive layer can effectively improve the adhesion of the separator and also has good wettability with the electrolyte, which can greatly improve battery performance.

[0023] Preferably, the thickness of the ceramic layer is 1–5 μm; within this range, the separator has good heat resistance, which can effectively prevent thermal abuse and improve the safety performance of the battery.

[0024] Preferably, the raw materials for the adhesive include soft monomers, hard monomers, crosslinking monomers, flexible elastomers, first tackifying resins, second tackifying resins, reactive emulsifiers, non-reactive emulsifiers, initiators, and reaction mediators.

[0025] In embodiments of the present invention, the soft monomer includes, but is not limited to, at least one of butyl acrylate, isooctyl acrylate, and methyl acrylate.

[0026] In embodiments of the present invention, the hard monomer includes at least one of methyl methacrylate, methyl acrylate, ethyl acrylate, styrene, and acrylonitrile.

[0027] In embodiments of the present invention, the crosslinking monomer includes at least one of acrylic acid, methacrylic acid, itaconic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, glycidyl acrylate, and glycidyl methacrylate.

[0028] In embodiments of the present invention, the flexible elastomer includes, but is not limited to, at least one of SBS, SEBS, EVA, polyacrylate rubber, nitrile rubber, and natural rubber.

[0029] In embodiments of the present invention, the first tackifying resin includes, but is not limited to, at least one of terpene phenolic resin, rosin resin, rosin pentaerythritol resin, phenolic resin, and hydrogenated rosin.

[0030] In embodiments of the present invention, the second tackifying resin includes, but is not limited to, at least one of hydrogenated petroleum resin, hydrogenated C9 petroleum resin, and hydrogenated C5 petroleum resin.

[0031] As a preferred embodiment, the mass percentage of each component in the adhesive raw material is as follows:

[0032]

[0033] Preferably, the mass percentage of each component in the adhesive raw material is as follows:

[0034]

[0035]

[0036] Under the specific proportions of the above components, the adhesive in the separator ceramic layer has a better expansion and transfer effect at high temperatures. In the event of thermal abuse, the gap between the positive and negative electrodes increases, which can quickly dissipate heat, prevent battery thermal runaway, and improve battery safety performance.

[0037] In a specific embodiment provided by the present invention, the soft monomer is butyl acrylate, the hard monomer is methyl methacrylate, the crosslinking monomer includes acrylic acid and acrylamide, the flexible elastomer includes SBS and SEBS, the first tackifying resin is terpene phenolic resin, and the second tackifying resin is hydrogenated petroleum resin.

[0038] As a preferred embodiment, the mass percentage of each component in the adhesive raw material is as follows:

[0039]

[0040] Preferably, the mass percentage of each component in the adhesive raw material is as follows:

[0041]

[0042]

[0043] More preferably, the mass percentage of each component in the adhesive raw material is as follows:

[0044]

[0045] In embodiments of the present invention, reactive emulsifiers include, but are not limited to, at least one of SE-10N, allyl ether sulfonates, acrylamide sulfonates, maleic acid derivatives, and allyl succinate alkyl ester sulfonates. The function of reactive emulsifiers is to disperse oil-soluble monomers in water, allowing the monomers to participate more effectively in the polymerization reaction.

[0046] In embodiments of the present invention, non-reactive emulsifiers include, but are not limited to, at least one of OP-10, OP-20, OP-S-25, Tween 80, and Tween 85. The function of non-reactive emulsifiers is to disperse oil-soluble monomers in water, allowing the monomers to participate more effectively in the polymerization reaction, but they themselves do not participate in the polymerization reaction.

[0047] In embodiments of the present invention, the initiator includes, but is not limited to, at least one of ammonium persulfate, sodium persulfate, and potassium persulfate. Upon heating, the initiator can provide free radicals to initiate the polymerization reaction of the monomers.

[0048] In this embodiment of the invention, the reaction medium includes water. The reaction medium serves to provide a site for the polymerization reaction.

[0049] The present invention also provides a battery comprising the above-described separator.

[0050] The present invention also provides a battery, including a positive electrode, a negative electrode, and a separator; the separator is disposed between the positive electrode and the negative electrode, and the separator includes a base film and a ceramic layer; the ceramic layer is disposed on at least one surface of the base film;

[0051] The ceramic layer comprises ceramic and an adhesive, the adhesive comprising acrylic groups and / or acrylates;

[0052] After the battery undergoes a thermal abuse test, the separator ceramic layer is transferred to the electrode, and the ceramic layer coverage on the electrode is ≥80%.

[0053] The ceramic layer coverage of the electrode is:

[0054]

[0055] Wherein, S1 is the area of ​​the positive or negative electrode; S2 is the area of ​​the ceramic layer covering the surface of the positive or negative electrode after the battery undergoes thermal abuse test, and the ceramic layer is the ceramic layer transferred from the separator ceramic layer to the electrode.

[0056] With this level of ceramic layer coverage, either the positive or negative electrode can be covered to form a dense protective film. This compensates for the short circuit problem caused by the natural thermal shrinkage of the separator, increasing the thermal abuse pass rate of high-voltage or high-energy-density batteries. Furthermore, it can minimize the surface reduction reaction of the carbon electrode, significantly reducing heat generation on the negative electrode surface and achieving the technical effect of passing thermal abuse tests.

[0057] In an embodiment of the present invention, the method for testing the coverage of the ceramic layer includes:

[0058] (1) The area of ​​the positive or negative electrode is denoted as S1;

[0059] After the thermal abuse test, the ceramic area on the surface of the positive or negative electrode is measured and denoted as S2. This ceramic is the ceramic transferred from the separator ceramic layer to the electrode.

[0060] (2) Calculate the ceramic layer coverage of the electrode according to the ceramic layer coverage formula.

[0061] In this embodiment of the invention, the temperature of the thermal abuse test is 130°C or higher, and the duration of the thermal abuse test is 30 minutes or higher.

[0062] In an embodiment of the present invention, the method for thermal abuse testing includes:

[0063] (1) Charge the battery at a constant current and constant voltage at 25°C with a certain rate (e.g., 0.7C). When the voltage reaches the cutoff voltage, switch to constant voltage mode for charging. Cut off charging when the cutoff current (generally 0.02C) is reached.

[0064] (2) Increase the temperature from room temperature (25°C) to 130°C or above at a rate of 5°C / min, and maintain the temperature for 30 minutes or more.

[0065] In a specific embodiment of the present invention, the temperature of the thermal abuse test is 130-140°C, and the duration of the thermal abuse test is 30-60 minutes.

[0066] Preferably, the expansion coefficient of the electrode assembly in the battery is 20% to 55%. Under the above expansion coefficient of the electrode assembly, the separator ceramic layer increases the distance between the positive and negative electrodes, which can quickly dissipate heat, prevent battery thermal runaway, and improve the safety performance of the battery.

[0067] The expansion coefficient of the pole group is:

[0068]

[0069] Wherein, a is the thickness of the electrode assembly single layer before the thermal abuse test, and b is the thickness of the electrode assembly single layer after the thermal abuse test; the thickness of the electrode assembly single layer is the sum of the thicknesses of the single-layer positive electrode, the single-layer separator, and the single-layer negative electrode.

[0070] In this embodiment of the invention, the method for testing the coefficient of thermal expansion is as follows:

[0071] (1) Measure the thickness a of the single layer of the electrode assembly before the thermal abuse test (after the battery is hot-pressed or activated);

[0072] (2) Measure the thickness b of the single layer of the electrode group after the thermal abuse test;

[0073] (3) Calculate the expansion coefficient of the electrode assembly in the battery according to the expansion coefficient formula.

[0074] In one embodiment of the present invention, the thermal expansion performance of the diaphragm containing the adhesive is evaluated as follows:

[0075] (1) A separator with a single ceramic layer is obtained by bonding a ceramic layer containing a binder to one side surface (single layer) of the base film. Then, the separator with a single ceramic layer is placed between the positive and negative electrodes, with the side of the separator with the ceramic layer in contact with the negative electrode. The expansion coefficient of the battery after thermal abuse test is recorded as the first expansion coefficient.

[0076] (2) A ceramic layer containing binder is composited with one side surface (single layer) of the base film to obtain a separator with a single ceramic layer. Then the separator with a single ceramic layer is placed between the positive and negative electrodes, with the side of the separator with the ceramic layer in contact with the positive electrode. The expansion coefficient of the battery after thermal abuse test is recorded as the second expansion coefficient.

[0077] (3) The ceramic layer containing binder is combined with the two sides of the base film (two layers) to obtain a separator with two ceramic layers. Then the separator with two ceramic layers is placed between the positive and negative electrodes. The expansion coefficient of the battery after thermal abuse test is recorded as the third expansion coefficient.

[0078] The thermal expansion performance of the electrode group is evaluated as follows: third expansion coefficient > first expansion coefficient > second expansion coefficient.

[0079] In this embodiment of the invention, the expansion coefficients at different locations of the battery vary due to different heating conditions.

[0080] Figure 7 It shows the positional relationship between the top, middle, and bottom of the pole group;

[0081] Top: The area from the cell tab to one-third of the way from the top of the cell body is collectively referred to as the top of the electrode assembly;

[0082] Middle section: The area from 1 / 3 of the distance from the top of the cell body to 2 / 3 of the distance from the top of the cell body is collectively referred to as the middle section of the electrode group;

[0083] Bottom: The area from the top 2 / 3 of the cell body to the bottom of the cell body is collectively referred to as the bottom of the electrode assembly.

[0084] In the above embodiments, the "expansion coefficient" can be the expansion coefficient of the top, middle or bottom of the electrode group, or it can be the average of the expansion coefficients of the top, middle and bottom of the electrode group.

[0085] The expansion coefficients of the top, middle, and bottom of the pole group are as follows:

[0086] In a specific embodiment of the present invention, the first expansion coefficients of the top, middle and bottom of the electrode assembly are 40% to 55%, 33% to 48% and 20% to 35%, respectively.

[0087] In a specific embodiment of the present invention, the second expansion coefficients of the top, middle and bottom of the electrode assembly are 25% to 40%, 20% to 35% and 15% to 25%, respectively.

[0088] In a specific embodiment of the present invention, the third expansion coefficients of the top, middle and bottom of the electrode assembly are 50% to 70%, 38% to 55%, and 25% to 40%, respectively.

[0089] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0090] This invention utilizes acrylic groups and / or acrylates to prepare a ceramic layer. Using this acrylate adhesive and ceramic, ceramic particles can be bonded to one or both sides of a PE substrate. A key performance indicator achieved by this adhesive is that when the battery temperature reaches 130°C or higher and is continuously heated for more than 30 minutes, the adhesive expands and detaches, transferring to either the positive or negative electrode. This expansion widens the gap between the positive and negative electrodes, allowing for coverage of both. For example, when the battery temperature reaches 130°C, the SEI film on the surface of the carbon negative electrode decomposes, exposing the highly active carbon electrode surface for unnecessary reduction reactions and releasing a large amount of heat. However, once heated to 130°C, the ceramic layer of this invention expands and transfers to the negative electrode, forming a dense protective film. This minimizes the surface reduction reaction of the carbon electrode, significantly reducing heat generation on the negative electrode surface and enabling the battery to pass thermal abuse tests. Attached Figure Description

[0091] Figure 1 Example 1: Schematic diagram of the layered structure of the battery electrode;

[0092] Figure 2 Example 2: Schematic diagram of the layered structure of the battery electrode sheet;

[0093] Figure 3 Example 3: Schematic diagram of the layered structure of the battery electrode sheet;

[0094] Among them, 1 is the negative electrode, 2 is the ceramic layer, 3 is the base film, and 4 is the positive electrode.

[0095] Figure 4 : Schematic diagram of the layered structure of battery electrode before and after battery thermal abuse test; where 4-1 shows the expansion and transfer of battery electrode with ceramic layer coated on the side of the base film near the negative electrode; 4-2 shows the expansion and transfer of battery electrode with ceramic layer coated on the side of the base film near the positive electrode; 4-3 shows the expansion and transfer of battery electrode with ceramic layer coated on both sides of the base film.

[0096] Figure 5 Schematic diagram of the area of ​​the positive and negative electrode plates covered by the ceramic layer before and after the thermal abuse test;

[0097] Figure 6 SEM images of the area of ​​the electrode covered by the ceramic layer before and after the thermal abuse test. The circled areas in the image are the electrode parts not covered by the ceramic layer. This image is of a battery after the furnace temperature test. After disassembly, some electrode sheets were taken for inspection and SEM testing. It was found that the black circles are inside the exposed electrode sheets, indicating that the ceramic in this part has not been transferred. This part is not counted in the transferred part.

[0098] Figure 7 Schematic diagram of the pole group. Detailed Implementation

[0099] This invention discloses a separator and a battery. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can obviously make modifications or appropriate alterations and combinations to the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0100] Chinese Names and English Abbreviations Comparison Table:

[0101] English abbreviations Chinese name SBS Styrene-butadiene-styrene block copolymer SEBS Hydrogenated styrene-butadiene block copolymer EVA Ethylene-vinyl acetate copolymer PVDF polyvinylidene fluoride PE polyethylene SBR Styrene-butadiene rubber CMC-Na Sodium carboxymethyl cellulose

[0102] The reagents, instruments, and materials used in this invention can all be obtained through commercial channels.

[0103] The present invention will be further illustrated below with reference to the embodiments:

[0104] Example 1: Preparation of the battery

[0105] 1. Preparation of the diaphragm:

[0106] (1) The adhesive formulation is as follows:

[0107] Table 1

[0108]

[0109]

[0110] (2) Mix the ceramic powder (alumina) with the above adhesive at a ratio of ceramic:adhesive = 92%: 8% to obtain a ceramic adhesive mixture for later use;

[0111] (3) Apply the ceramic layer of the diaphragm according to the ceramic adhesive mixture prepared above, with a coating thickness of 2μm; then apply the PVDF adhesive layer. The overall design scheme is 1+5+2+1, where 5 represents a 5μm PE base film, 2 represents a ceramic coating with a thickness of 2μm on one side, and 1 represents an adhesive layer with a thickness of 1μm on both sides (the adhesive can be PVDF).

[0112] 2. Positive electrode structure:

[0113] The foil material is aluminum foil, 10μm; the positive electrode coating includes: positive electrode active material is LiCoO2, accounting for 97.8%; conductive agent is conductive carbon black, accounting for 1.2%; binder is polyvinylidene fluoride, accounting for 1.0%.

[0114] 3. Negative electrode structure:

[0115] The foil material is high-strength copper foil, 5μm; the negative electrode coating includes: the negative electrode active material is mesophase carbon microspheres, accounting for 96.70%; the conductive agent is carbon nanotubes, accounting for 0.70%; the binder is SBR, accounting for 1.30%; and the dispersant is sodium carboxymethyl cellulose (CMC), accounting for 1.30%.

[0116] 4. Electrolyte:

[0117] EC:EMC:DEC = 3:5:2, LiPF6 is 1.2 mol / L.

[0118] 5. Battery assembly:

[0119] Then the diaphragm is used in combination with the positive and negative electrodes, such as... Figure 1 As shown, the ceramic layer of the separator is used to produce the core of the negative electrode, followed by encapsulation, liquid injection, formation, secondary sealing, sorting, OCV, and finally, the battery is subjected to electrical performance testing.

[0120] Example 2: Battery Preparation

[0121] The battery assembly differs from that in Example 1:

[0122] The diaphragm is used in conjunction with the positive and negative electrodes, such as... Figure 2 As shown, the ceramic layer of the separator is used to produce the core of the positive electrode, followed by encapsulation, liquid injection, formation, secondary sealing, sorting, OCV, and finally, the battery is subjected to electrical performance testing.

[0123] Example 3: Preparation of the battery

[0124] The differences from Example 1 lie in the preparation of the separator and the assembly of the battery:

[0125] The ceramic layer of the diaphragm was coated according to the ceramic adhesive mixture of Example 1, with a coating thickness of 2μm. Then, the PVDF adhesive layer was coated. The overall design scheme is 1+1+5+1+1, where 5 indicates that the base membrane is a 5μm PE base membrane, the double-sided 1 next to 5 indicates that both sides of the 5μm base membrane are coated with a 1μm thick ceramic layer, and the outermost 1 indicates that both sides have an adhesive layer with a 1μm thickness (this adhesive can be PVDF adhesive).

[0126] Then the diaphragm is used in combination with the positive and negative electrodes, such as... Figure 3 As shown, the process involves producing the core, encapsulation, electrolyte injection, formation, secondary sealing, sorting, OCV, and finally, battery electrical performance testing.

[0127] Example 4: Preparation of the battery

[0128] The composition of the ceramic adhesive mixture differs from that of Example 1:

[0129] Table 2

[0130] type Element weight percentage Soft monomers Butyl acrylate 20％ Hard monomers Methyl methacrylate 14.5％ Crosslinking monomer 1 acrylic acid 7.2％ Crosslinking monomer 2 Acrylamide 6.4％ Flexible elastomer 1 SBS 1.2％ Flexible elastomer 2 SEBS 1.3％ reactive emulsifiers SE-10N 0.35％ emulsifier OP-10 0.35％ Initiator ammonium persulfate 0.1％ Tackifying resin 1 Terpene phenolic resin 2.3％ Tackifying resin 2 Hydrogenated petroleum resin 1.6％ Reaction medium Deionized water 44.70％

[0131] Example 5: Preparation of the battery

[0132] The composition of the ceramic adhesive mixture differs from that of Example 1:

[0133] Table 3

[0134] type Element weight percentage Soft monomers Butyl acrylate 1％ Hard monomers Methyl methacrylate 1％ Crosslinking monomer 1 acrylic acid 0.5％ Crosslinking monomer 2 Acrylamide 0.5％ Flexible elastomer 1 SBS 14.2％ Flexible elastomer 2 SEBS 17.8％ reactive emulsifiers SE-10N 0.35％ emulsifier OP-10 0.35％ Initiator ammonium persulfate 0.1％ Tackifying resin 1 Terpene phenolic resin 6.3％ Tackifying resin 2 Hydrogenated petroleum resin 3.2％ Reaction medium Deionized water 54.70％

[0135] Example 6: Preparation of the battery

[0136] The composition of the ceramic adhesive mixture differs from that of Example 1:

[0137] Table 4

[0138] type Element weight percentage Soft monomers Butyl acrylate 10％ Hard monomers Methyl methacrylate 12.5％ Crosslinking monomer 1 acrylic acid 13.2％ Crosslinking monomer 2 Acrylamide 16.4％ Flexible elastomer 1 SBS 1.2％ Flexible elastomer 2 SEBS 1.3％ reactive emulsifiers SE-10N 0.35％ emulsifier OP-10 0.35％ Initiator ammonium persulfate 0.1％ Tackifying resin 1 Terpene phenolic resin 1.3％ Tackifying resin 2 Hydrogenated petroleum resin 1.6％ Reaction medium Deionized water 41.70％

[0139] Example 7: Preparation of the battery

[0140] The difference from Example 1 is:

[0141] The soft monomer is isooctyl acrylate.

[0142] The hard monomer is methyl acrylate.

[0143] Crosslinking monomer 1 is itaconic acid.

[0144] Crosslinking monomer 2 is hydroxyethyl acrylate.

[0145] Flexible elastomer 1 is EVA.

[0146] Flexible elastomer 2 is polyacrylate rubber.

[0147] Tackifying resin 1 is rosin resin.

[0148] Tackifying resin 2 is hydrogenated C9 petroleum resin.

[0149] The reactive emulsifier is an allyl ether sulfonate.

[0150] The emulsifier is OP-20.

[0151] The initiator is sodium persulfate.

[0152] Example 8: Preparation of the battery

[0153] The difference from Example 1 is:

[0154] The type of soft monomer is methyl acrylate.

[0155] The type of hard monomer is ethyl acrylate.

[0156] Crosslinking monomer 1 is hydroxyethyl methacrylate.

[0157] Crosslinking monomer 2 is hydroxypropyl acrylate.

[0158] Flexible elastomer 1 is nitrile rubber.

[0159] Flexible elastomer 2 is natural rubber.

[0160] Tackifying resin 1 is rosin pentaerythritol resin.

[0161] Tackifying resin 2 is hydrogenated C5 petroleum resin.

[0162] The reactive emulsifier is acrylamide sulfonate.

[0163] The emulsifier is OP-S-25.

[0164] The initiator is potassium persulfate.

[0165] Example 9: Preparation of the battery

[0166] The difference from Example 1 is:

[0167] The type of soft monomer is methyl acrylate.

[0168] The rigid monomers are styrene and acrylonitrile (1:1).

[0169] Crosslinking monomer 1 is glycidyl acrylate.

[0170] Crosslinking monomer 2 is glycidyl methacrylate.

[0171] Flexible elastomer 1 is SBS.

[0172] Flexible elastomer 2 is EVA.

[0173] Tackifying resin 1 is hydrogenated rosin.

[0174] Tackifying resin 2 is hydrogenated C5 petroleum resin.

[0175] The reactive emulsifier is allyl succinate alkyl ester sulfonate.

[0176] The emulsifier is Tween 80.

[0177] The initiator is ammonium persulfate.

[0178] Example 10: Preparation of the battery

[0179] The ceramic adhesive mixture differs from Example 1 in that it is prepared by mixing ceramic and adhesive in a ratio of 88% to 12%.

[0180] Example 11: Preparation of the battery

[0181] The ceramic adhesive mixture differs from Example 1 in that it is prepared by mixing ceramic and adhesive in a ratio of 97% to 3%.

[0182] Example 12: Preparation of the battery

[0183] The ceramic adhesive mixture differs from Example 1 in that it is prepared by mixing ceramic and adhesive in a ratio of 90% to 10%.

[0184] Comparative Example 1: Preparation of the battery

[0185] The composition of the ceramic adhesive mixture differs from that of Example 1:

[0186] Table 5

[0187]

[0188] Comparative Example 2: Preparation of the battery

[0189] Unlike Example 2, the ceramic adhesive mixture of Comparative Example 1 was used.

[0190] Preparation of Comparative Example 3 Battery

[0191] Unlike Example 3, the ceramic adhesive mixture of Comparative Example 1 was used.

[0192] Preparation of Comparative Example 4 Battery

[0193] Unlike Example 1, SBR & CMC (1:1) were used as the adhesive.

[0194] Preparation of Comparative Example 5 Battery

[0195] The ceramic adhesive mixture differs from Example 1 in that it is prepared by mixing ceramic and adhesive in a ratio of 80% to 20%.

[0196] Battery performance test

[0197] The batteries of Examples 1-12 and Comparative Examples 1-5 were tested as follows:

[0198] 1. Thermal abuse test:

[0199] Battery full charge procedure: constant current and constant voltage charging is performed in a constant temperature chamber at 25℃ at a certain rate (0.7C). When the voltage reaches the cutoff voltage, the charging will switch to constant voltage mode. Charging is considered to be completed when the cutoff current (generally 0.02C) is reached. Then, furnace temperature test is performed.

[0200] The temperature is increased from room temperature (25℃) to a specified temperature (130℃ / 135℃ / 140℃) at a rate of 5℃ / min, and then held at that temperature for 60 minutes. After the time is up, the temperature chamber is opened to check the battery. If the battery does not catch fire, explode, or emit smoke, it is considered to have passed the furnace temperature test.

[0201] 2. Coefficient of thermal expansion:

[0202] like Figure 4 As shown, the single-layer thickness of the electrode assembly (the sum of the thicknesses of the single-layer positive electrode, single-layer separator, and single-layer negative electrode) after the battery undergoes hot-pressing formation or activation is 'a'. After the battery is subjected to thermal abuse (generally 130℃ for 60 minutes), the single-layer thickness of the electrode assembly is 'b' (b can be b1, b2, or b3, where b1 refers to the thickness of the battery electrode with ceramic layers coated on both sides of the base film after expansion, b2 refers to the thickness of the battery electrode with ceramic layers coated on the side of the base film closest to the negative electrode after expansion, and b3 refers to the thickness of the battery electrode with ceramic layers coated on the side of the base film closest to the positive electrode after expansion). This thickness data comes from test results obtained under full CT scanning of the battery. The expansion coefficient formula is:

[0203]

[0204] 3. Coverage:

[0205] like Figure 5 As shown, the coverage of the electrode ceramic layer in the battery is as follows:

[0206]

[0207] For example, the area of ​​the positive electrode taken in a single measurement is S1, where S1 is the area of ​​the entire electrode at that magnification; the ceramic area on its surface is measured as S2, which is obtained by subtracting the area of ​​the exposed electrode in that region from the area of ​​the positive electrode. The formula for calculating the coverage rate of the negative electrode after ceramic transfer is as above. Figure 5 The diagram is for illustrative purposes only and does not represent the actual size and shape of the transfer. After thermal abuse, the electrode should be taken for SEM inspection. The sample should be examined using SEM (e.g., ...). Figure 6 The area is divided into blocks and the area size is calculated and summarized.

[0208] The voltage system in the above experiment was 4.5V and 830Wh / L.

[0209] The test results are as follows:

[0210] Table 6

[0211]

[0212]

[0213] Note: "Dry adhesive" refers to the product obtained after the components in the adhesive formulation react, excluding water.

[0214] Table 7. Expansion coefficient and average expansion coefficient at different locations of the battery.

[0215]

[0216]

[0217] Note: Due to varying degrees of heating, the expansion coefficient of the battery differs at different locations. The area around the tabs is referred to as the top, the middle of the battery as the middle section, and the side of the battery corresponding to the tabs as the bottom. Average expansion coefficient = (Top expansion coefficient + Middle expansion coefficient + Bottom expansion coefficient) ÷ 3, or, Average expansion coefficient = (Average top expansion coefficient + Average middle expansion coefficient + Average bottom expansion coefficient) ÷ 3.

[0218] summary:

[0219] Compared to Comparative Examples 1-5, the ceramic layer adhesive used in Examples 1-12 demonstrates a significant improvement in battery thermal abuse performance. This is due to a substantial change in the interlayer expansion coefficient and a large area transfer of the ceramic layer on the separator, achieving a coverage rate of approximately 98%. The interlayer expansion coefficient can reach a thickness expansion of up to 39%, which are the fundamental reasons for the significant improvement in battery thermal abuse performance. Using the ceramic layer adhesive of this solution elevates battery thermal abuse performance to a new level.

[0220] The coefficient of expansion refers to the ratio of the distance between battery layers to the distance between layers after hot pressing. The expansion of the embodiment is greater than that of the comparative embodiment, indicating that the battery is more conducive to heat dissipation, as demonstrated by furnace temperature testing.

[0221] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A diaphragm, characterized in that, The diaphragm includes a base membrane and a ceramic layer; the ceramic layer is disposed on at least one surface of the base membrane. The ceramic layer comprises ceramic and an adhesive, wherein the adhesive is solid at room temperature and melts at temperatures above 130°C, exhibiting re-adhesive properties; the adhesive further comprises one or more of the following: acrylic groups, acrylates, amide groups, carboxylic acid groups, and C=O double bonds; The adhesive is polymerized from soft monomers, hard monomers, crosslinking monomers, flexible elastomers, a first tackifying resin, and a second tackifying resin. The mass percentage of each component in the adhesive raw material is as follows: Soft monomers 1%~20% Hard monomers 1%~15% Crosslinking monomers 1%~30% Flexible elastomers 2%~35% First tackifying resin: 1%~7% The second tackifying resin is 1% to 4%. Reactive emulsifier 0.05%~1% Non-reactive emulsifier 0.05%~1% Initiator 0.005%~0.5% Reaction medium 40%~60%; The soft monomer includes at least one of butyl acrylate, isooctyl acrylate, and methyl acrylate; The hard monomer includes at least one of methyl methacrylate, methyl acrylate, ethyl acrylate, styrene, and acrylonitrile; The crosslinking monomer includes at least one of acrylic acid, methacrylic acid, itaconic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, glycidyl acrylate, and glycidyl methacrylate. The flexible elastomer includes at least one of SBS, SEBS, EVA, polyacrylate rubber, nitrile rubber, and natural rubber; The first tackifying resin includes at least one of terpene phenolic resin, rosin resin, rosin pentaerythritol resin, phenolic resin, and hydrogenated rosin; The second tackifying resin includes at least one of hydrogenated petroleum resin, hydrogenated C9 petroleum resin, and hydrogenated C5 petroleum resin; The mass ratio of the ceramic to the adhesive is (88~97):(3~12).

2. The diaphragm according to claim 1, characterized in that, The adhesive includes polyacrylate hot melt adhesive.

3. The diaphragm according to claim 1, characterized in that, The ceramic comprises at least one of alumina, aluminum hydroxide, boehmite, silicon dioxide, titanium dioxide, and barium sulfate; The melting point of the ceramic is >1000℃.

4. The diaphragm according to claim 1, characterized in that, The C=O double bond accounts for 1% to 30% of the total mass of the adhesive.

5. The diaphragm according to claim 1, characterized in that, The mass ratio of the ceramic to the adhesive is (90~96):(3~12).

6. The diaphragm according to claim 1, characterized in that, The diaphragm further includes an adhesive layer disposed on both sides of the base membrane; the ceramic layer is disposed between the base membrane and the adhesive layer; The coating layer includes at least one of PVDF, PVDF-HFP, PMMA, and PVA, or a mixture thereof with inorganic substances.

7. The diaphragm according to any one of claims 1-6, characterized in that, The thickness of the ceramic layer is 1~5μm.

8. A battery, characterized in that, The diaphragm includes any one of claims 1-7.

9. A battery, characterized in that, The battery includes a positive electrode, a negative electrode, and a separator; the separator includes the separator according to any one of claims 1 to 7. After the battery undergoes a thermal abuse test, the separator ceramic layer is transferred to the electrode, and the ceramic layer coverage on the electrode is ≥80%. The ceramic layer coverage of the electrode is: ； in, S 1 represents the area of ​​the positive or negative electrode plate; S 2 represents the ceramic layer coverage area on the surface of the positive or negative electrode after the battery undergoes thermal abuse testing.

10. The battery according to claim 8 or 9, characterized in that, After undergoing thermal abuse testing, the expansion coefficient of the electrode assembly in the battery is 20%~55%; the electrode assembly includes a positive electrode, a separator, and a negative electrode. The expansion coefficient of the pole group is: ； Where a represents the thickness of the electrode assembly monolayer before the thermal abuse test, and b represents the thickness of the electrode assembly monolayer after the thermal abuse test.

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