Battery separator slurry, thermally responsive safety separator and its application, thermally responsive safety lithium ion battery

Abstract

The present application relates to the technical field of lithium ion batteries, and discloses a slurry for a battery separator, a thermally responsive safety separator, application of the thermally responsive safety separator, and a thermally responsive safety lithium ion battery.The slurry contains microspheres A, microspheres B, a thickening agent, and a binder; wherein, based on the total weight of the slurry, the content of microspheres A is 30-50 wt%, and the content of microspheres B is 25-48 wt%; the material forming microspheres A includes initiator A; the material forming microspheres B includes initiator B; initiator A is a peroxide; and initiator B is selected from at least one of oxalic acid, glucose, N,N-dimethylaniline, a naphthenate, n-dodecanethiol, triethylaluminum, and triethylboron.The thermally responsive safety separator formed from the slurry for a battery separator according to the present application is applied to a lithium ion battery containing a thermally polymerizable monomer, can operate normally under conventional working conditions, and can cut off the internal ion channel during thermal runaway of the battery, thereby avoiding smoking, fire, and explosion of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a slurry for battery separator, a thermally responsive safety separator and its application, and a thermally responsive safety lithium ion battery. BACKGROUND

[0002] Due to the advantages of high energy density and long cycle life, lithium ion batteries have been widely used in many fields since their inception. In recent years, due to the shortage of fossil energy and other reasons, the development of renewable energy technologies such as photovoltaic and wind power has been increasingly valued, which has once again promoted the large-scale application of lithium ion batteries in the energy storage field.

[0003] For cost, safety and environmental considerations, lithium iron phosphate batteries are the most widely used energy storage batteries. Despite this, they may still have safety accidents under external heat, mechanical and electrical misuse, posing a huge challenge to the safe and stable operation of energy storage systems.

[0004] By using an electrolyte containing an initiator and a thermal polymerization monomer, a lithium ion battery with thermal response function can be prepared, which can initiate electrolyte polymerization before the battery is severely out of control, thereby cutting off the ion channel inside the battery, and also relieving the problem of gas production of liquid electrolyte. However, due to the lack of long-term stability of the initiator used in the thermally responsive electrolyte under light and room temperature, it has a serious impact on the energy efficiency and cycle life of the battery, and there is currently no good solution.

[0005] CN112615107A discloses a microsphere containing a microsphere, a separator containing the microsphere and a lithium ion battery containing the separator, the microsphere has a core-shell structure, the average particle size is 0.01-10 microns, the material forming the shell layer includes a heat-sensitive polymer, and the material forming the core includes a conductive material; wherein the heat-sensitive polymer is selected from polyethylene, polypropylene and the like, the conductive material is an electron acceptor doped and / or undoped polymer material, and the microsphere also contains ceramic particles such as silicon dioxide. That is, the technical solution is to use a polymer directional design coating method to screen a heat-sensitive polymer coated conductive material, coat the microsphere containing the heat-sensitive polymer coated conductive material on the surface of the separator without affecting the performance of the lithium ion battery, which can effectively improve the high-temperature safety performance of the lithium ion battery, but it mainly ensures the safety of the battery by slowly releasing energy through internal micro-short circuit of the battery, which cannot effectively cut off the ion channel inside the battery, and thus cannot guarantee the safety of the battery in extreme conditions such as needle puncture or rapid temperature rise, and also has the defect of increasing the risk of internal short circuit of the battery. SUMMARY

[0006] The purpose of the present application is to overcome the defects of low energy efficiency and short cycle life of the prior art thermally responsive safety lithium ion battery.

[0007] To achieve the above object, a first aspect of the present application provides a slurry for battery separator, which contains microspheres A, microspheres B, a thickening agent and a binder;

[0008] wherein the content of the microspheres A is 30-50wt%, the content of the microspheres B is 25-48wt%, the content of the thickening agent is 5-15wt%, and the content of the binder is 3-17wt%, based on the total weight of the slurry;

[0009] The material forming the microspheres A comprises initiator A; the material forming the microspheres B comprises initiator B;

[0010] The initiator A is a peroxide;

[0011] The initiator B is selected from at least one of oxalic acid, glucose, N,N-dimethylaniline, naphthenate, n-dodecanethiol, triethylaluminum and triethylboron;

[0012] The particle size D 50 Each independently is 0.05-5μm.

[0013] A second aspect of the present application provides a heat-responsive safety separator, which comprises a base film and a heat-responsive safety coating layer coated on the upper and lower surfaces of the base film;

[0014] The heat-responsive safety coating layer is formed by the slurry for battery separator of the first aspect.

[0015] A third aspect of the present application provides the use of the heat-responsive safety separator of the second aspect in a lithium ion battery.

[0016] A fourth aspect of the present application provides a heat-responsive safety lithium ion battery, which comprises a positive electrode sheet, a negative electrode sheet, a heat-responsive electrolyte and a heat-responsive safety separator; the heat-responsive electrolyte contains a heat-polymerizable monomer;

[0017] The heat-responsive safety separator is the heat-responsive safety separator of the second aspect.

[0018] By the above technical solution, the present application has at least the following advantages:

[0019] The heat-responsive safety separator coated by the slurry for battery separator of the present application is applied in a lithium ion battery containing a heat-polymerizable monomer, which can normally operate under a conventional working environment, but the internal liquid electrolyte will rapidly change into solid state during the thermal runaway process of the battery, thereby cutting off the internal ion channel and avoiding the battery from smoking, fire and explosion. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a battery cycle performance test result graph of a thermal response safety lithium ion battery prepared in an application example of the present application;

[0021] Figure 2 is a battery rate performance test result graph of a thermal response safety lithium ion battery prepared in an application example of the present application;

[0022] Figure 3 is a battery energy efficiency test result graph of a thermal response safety lithium ion battery prepared in an application example of the present application;

[0023] Figure 4 is a battery thermal response safety test result graph of a thermal response safety lithium ion battery prepared in an application example of the present application;

[0024] Figure 5 is a scanning electron microscope graph of microspheres A prepared in Preparation Example 1 at different magnifications. DETAILED DESCRIPTION

[0025] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are understood to be approximate values. The exact numerical values of the endpoints of the ranges and the separate numerical values are not to be construed as limiting. Ranges can be expressed as from one value and / or to another value. When two values are expressed as a range, e.g. 0.1 to 10, this is intended to include both the lower value and the higher value, and to also include the individual values physiologically between the lower and higher values, i.e. any value from 0.1 to 10. When three values are expressed as a range, e.g. 0.5 to 10 to 15, this is intended to include each value from 0.5 and 15 inclusive, and to also include each value physiologically between the lower and higher values, i.e. any value from 0.5 to 15. The use of "between" and "and / or" with respect to a range includes the values that are expressly identified as the end points of the range. The use of "between" and "and / or" as to a range includes the individual values that are expressly identified as the end points of the range. The use of "between" and "and / or" as to a range includes the individual values that are expressly identified as the end points of the range.

[0026] In the present application, "EC" refers to ethylene carbonate, "DMC" refers to dimethyl carbonate, and "EMC" refers to ethyl methyl carbonate.

[0027] In the present application, 1M refers to "1 mol / L".

[0028] As described above, the first aspect of the present application provides a slurry for a battery separator, the slurry containing microspheres A, microspheres B, a thickening agent, and a binder;

[0029] wherein the content of the microspheres A is 30-50 wt%, the content of the microspheres B is 25-48 wt%, the content of the thickening agent is 5-15 wt%, and the content of the binder is 3-17 wt%, based on the total weight of the slurry;

[0030] The material forming the microspheres A includes an initiator A, and the material forming the microspheres B includes an initiator B;

[0031] The initiator A is a peroxide;

[0032] The initiator B is selected from at least one of oxalic acid, glucose, N,N-dimethylaniline, naphthenate, n-dodecanethiol, triethylaluminum, and triethylboron.

[0033] The particle size D of the microspheres A and the microspheres B 50 Each independently is 0.05-5 μm.

[0034] Preferably, the peroxide is selected from at least one of cumene hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, di-t-butyl peroxide, dibenzoyl peroxide, dilauryl peroxide, t-butyl benzene peroxide, t-amyl peroxide, diisopropyl peroxydicarbonate and dicyclohexyl peroxydicarbonate, more preferably at least one of dicumyl peroxide, cumene hydroperoxide and di-t-butyl peroxide, further preferably dicumyl peroxide.

[0035] Preferably, the initiator B is selected from at least one of N,N-dimethylaniline, n-dodecanethiol and glucose, preferably N,N-dimethylaniline.

[0036] Preferably, the particle size D of the microspheres A and the microspheres B 50 Each independently is 1-2 μm.

[0037] Preferably, the material forming the microspheres A and the microspheres B further comprises a hollow mesoporous material and a phase change material; wherein,

[0038] The hollow mesoporous material is selected from at least one of silica and / or a high molecular polymer I with a weight average molecular weight of 100,000-1,000,000, the high molecular polymer I being selected from at least one of polymethyl acrylate, polymethyl methacrylate, polyamide and polystyrene, more preferably at least one of silica, polymethyl methacrylate and polystyrene, further preferably polymethyl methacrylate.

[0039] The phase change material is selected from at least one of hydrated sulfate, n-dodecanethiol, n-docosane, 6-methyldodecane, 8-methyldocosane and a high molecular polymer II with a weight average molecular weight of 50,000-200,000, the high molecular polymer II being selected from at least one of polyethylene, polypropylene, polyethylene glycol and polyformaldehyde.

[0040] In the above preferred cases, the technical solution provided by the present application can obtain a lithium ion battery with more superior cycle performance, rate capability, energy efficiency and safety performance.

[0041] Preferably, the hydrated sulfate is magnesium sulfate heptahydrate and / or sodium sulfate decahydrate.

[0042] Further preferably, the phase change material is at least one of polyethylene, polypropylene and polyformaldehyde, most preferably polyethylene.

[0043] Preferably, the particle size D of the hollow mesoporous material 500.05-5 μm, preferably 1-2 μm.

[0044] According to a preferred embodiment, the microsphere A is prepared by a method comprising the following steps:

[0045] (1) contacting and mixing phase change material and initiator A in the presence of ethanol to obtain a mixed solution;

[0046] (2) contacting and mixing the mixed solution with hollow mesoporous material to obtain the microsphere A.

[0047] Preferably, the weight ratio of the phase change material, the initiator A and the hollow mesoporous material is 1:0.2-0.7:0.05-0.15.

[0048] Preferably, the amount of ethanol is 2-8 mL relative to 1 g of the phase change material.

[0049] Preferably, the contacting and mixing I is performed at a temperature of 30-60 °C for 5-15 min.

[0050] Preferably, the contacting and mixing II is performed at a temperature of 30-60 °C for 45-75 min.

[0051] According to a particularly preferred embodiment, the preparation of the microsphere A further comprises, after drying the product obtained from the contacting and mixing II in step (2), sequentially performing centrifugation and washing.

[0052] The present application does not have special requirements for the conditions of drying, centrifugation and washing, and those skilled in the art can use conventional operation means.

[0053] According to a preferred embodiment, the microsphere B is prepared by a method comprising the following steps:

[0054] (1) contacting and mixing phase change material and initiator B in the presence of ethanol to obtain a mixed solution;

[0055] (2) contacting and mixing the mixed solution with hollow mesoporous material to obtain the microsphere B.

[0056] Preferably, the weight ratio of the phase change material, the initiator B and the hollow mesoporous material is 1:0.2-0.7:0.05-0.15.

[0057] Preferably, the amount of ethanol is 2-8 mL relative to 1 g of the phase change material.

[0058] Preferably, the mixing condition of the contact mixture I includes a temperature of 30-60℃ and a time of 5-15 min.

[0059] Preferably, the mixing condition of the contact mixture II includes a temperature of 30-60℃ and a time of 45-75 min.

[0060] According to a particularly preferred embodiment, the preparation step of the microspheres B further includes, after drying the product obtained from the contact mixture II in step (2), sequentially performing centrifugation and washing.

[0061] As mentioned above, the second aspect of the present application provides a thermal response safety separator, which comprises a base film and a thermal response safety coating layer coated on the upper and lower surfaces of the base film.

[0062] The thermal response safety coating layer is formed from the battery separator slurry of the first aspect.

[0063] Preferably, the thermal response safety separator is prepared by a method comprising the following steps:

[0064] (S1) mixing the microspheres A, the microspheres B, a thickening agent (hydroxymethyl cellulose) and a binder (styrene-butadiene rubber) to obtain the battery separator slurry;

[0065] (S2) coating the battery separator slurry on a base film and drying to obtain the thermal response safety separator.

[0066] The amounts of the thermal response microspheres A, the thermal response microspheres B, the thickening agent and the binder are the same as the contents of the components in the battery separator slurry of the first aspect, which will not be repeated here.

[0067] Preferably, the mixing condition includes a rotation speed of 400-600 rpm and a time of 4-6 h.

[0068] Preferably, the drying condition includes a temperature of 40-70 rpm and a time of 10-14 h.

[0069] Preferably, the coating method is a doctor blade method.

[0070] Preferably, the base film is a polyolefin separator.

[0071] As mentioned above, the third aspect of the present application provides the use of the thermal response safety separator of the second aspect in a lithium ion battery.

[0072] As mentioned above, the fourth aspect of the present application provides a thermal response safety lithium ion battery, which comprises a positive electrode sheet, a negative electrode sheet, a thermal response electrolyte and a thermal response safety separator; the thermal response electrolyte contains a thermal polymerization monomer.

[0073] The heat-responsive safety diaphragm is the heat-responsive safety diaphragm of the second aspect.

[0074] Preferably, the heat polymerizable monomer is selected from at least one of methyl acrylate, methyl methacrylate, styrene, vinylene carbonate, butadiene, chlorobutadiene and acrylonitrile, and more preferably is vinylene carbonate.

[0075] The application will be described in detail below by way of examples. In the following examples, if not specifically stated, the raw materials and equipment used are commercially available, and the solvents used are of analytical purity.

[0076] Polyethylene: CAS No. 9002-88-4, weight average molecular weight 0.2-0.3 million, purchased from Shanghai Macklin Biochemical Technology Co., Ltd.;

[0077] Polypropylene: CAS No. 9003-07-0, weight average molecular weight 0.6-0.8 million, purchased from Shanghai Macklin Biochemical Technology Co., Ltd.;

[0078] Polyformaldehyde: CAS No. 9002-81-7, weight average molecular weight 1-1.2 million, purchased from Shanghai Titan Science and Technology Co., Ltd.;

[0079] Cumene hydroperoxide: CAS No. 80-15-9, purchased from Shanghai Macklin Biochemical Technology Co., Ltd.;

[0080] Dicumyl peroxide: CAS No. 80-43-3, purchased from Shanghai Macklin Biochemical Technology Co., Ltd.;

[0081] Di-tert-butyl peroxide: CAS No. 110-05-4, purchased from Shanghai Macklin Biochemical Technology Co., Ltd.;

[0082] Glucose: CAS No. 50-99-7, purchased from Shanghai Macklin Biochemical Technology Co., Ltd.;

[0083] N,N-dimethylaniline: CAS No. 121-69-7, purchased from Shanghai Macklin Biochemical Technology Co., Ltd.;

[0084] N-dodecanethiol: CAS No. 112-55-0, purchased from Shanghai Macklin Biochemical Technology Co., Ltd.;

[0085] Silicon dioxide: purchased from Jiangsu Xianfeng Nanometer Material Technology Co., Ltd.;

[0086] Polymethyl methacrylate: weight average molecular weight 1-1.5 million, purchased from Jiangsu Xianfeng Nanometer Material Technology Co., Ltd.;

[0087] Polystyrene: weight average molecular weight of 10,000-15,000, purchased from Jiangsu Xianfeng Nanometer Material Technology Co., Ltd.;

[0088] Methyl methacrylate: CAS number 80-62-6, purchased from Shanghai Aladdin Bio-Chem Technology Co., Ltd.;

[0089] Vinylene carbonate: CAS number 872-36-6, purchased from Shanghai Macklin Biochemical Technology Co., Ltd.;

[0090] Dibenzoyl peroxide: CAS number 94-36-0, purchased from Shanghai Macklin Biochemical Technology Co., Ltd.;

[0091] Commercial lithium-ion battery electrolyte: specific composition of 1M LiPF6 combined with EC, DMC, EMC (V EC :V DMC :V EMC =1:1:1), purchased from Fane New Energy Technology Co., Ltd.;

[0092] Polyolefin separator: Celgard 2400 separator, thickness 25 μm, single-layer PP material, 41% porosity, purchased from Celgard, USA;

[0093] Commercial lithium iron phosphate positive electrode: areal density of 12 mg / cm 2 , active material ratio of 95.4wt%, purchased from Shenzhen Keyou Zhida Technology Co., Ltd.;

[0094] Commercial graphite negative electrode: areal density of 5.8 mg / cm 2 , active material ratio of 95.5wt%, purchased from Shenzhen Keyou Zhida Technology Co., Ltd.

[0095] In the following examples, room temperature refers to 23±2℃.

[0096] In the following examples, the scanning electron microscope image is tested by GeminiSEM 360 scanning electron microscope of Zeiss type.

[0097] The following preparation example is used to illustrate the preparation method of microspheres A and microspheres B of the present application

[0098] Preparation Example 1

[0099] (1) 400 mg of phase change material and 200 mg of initiator A were dissolved and stirred to contact mix I (temperature 50℃, time 10 min) in the presence of 2 mL of hot ethanol, to obtain a mixed solution;

[0100] (2) 40 mg of hollow mesoporous material was added to the mixed solution to contact mix II (temperature 50℃, time 60 min);

[0101] Subsequently, the product was transferred to a vacuum oven at 50°C and heated for 30 min, and then centrifuged at 8000 rpm for 10 min.

[0102] After centrifugation, the product was washed with ethanol three times, and then dried at room temperature to obtain microspheres A.

[0103] (3) The same amount of initiator B for forming microspheres B was used to replace initiator A in step (1) above, and the same preparation method as microspheres A was used to prepare microspheres B.

[0104] The raw material ratios for preparing microspheres A and microspheres B are shown in Table 1.

[0105] The remaining preparation examples were prepared using a method similar to Preparation Example 1, except that the raw material ratios were different, as shown in Table 1.

[0106] Table 1

[0107]

[0108] The following example is used to illustrate the preparation method of the heat-responsive safety diaphragm of the present application

[0109] Example 1 (1 mg per 1 wt%)

[0110] (1) At room temperature, microspheres A prepared in Preparation Example 1 (40 wt%) and microspheres B prepared in Preparation Example 1 (40 wt%) were mixed with a thickening agent (hydroxymethyl cellulose, 10 wt%) and a binder (butyl rubber, 10 wt%) (at a speed of 500 rpm for 5 h) to obtain a uniform and stable slurry for battery separators;

[0111] (2) The slurry for battery separators was coated on a base film (Celgard 2400 separator) by scalpel coating, and dried at 60°C for 12 h to obtain a thermal response safety separator.

[0112] Examples 2-7

[0113] The same method as in Example 1 was used, except that the microspheres A prepared in Preparation Example 1 were replaced with the same amount of microspheres A prepared in Preparation Examples 2, 3, 4, 5, 6, and 7, respectively.

[0114] The microspheres B prepared in Preparation Example 1 were replaced with the same amount of microspheres B prepared in Preparation Examples 2, 3, 4, 5, 6, and 7, respectively.

[0115] Thermal response safety separators were obtained, respectively.

[0116] Comparative Example 1

[0117] The same method as example 1 was used, except that no microspheres A were added in this comparative example.

[0118] A thermally responsive safety separator was obtained.

[0119] Comparative Example 2

[0120] The same method as example 1 was used, except that no microspheres B were added in this comparative example.

[0121] A thermally responsive safety separator was obtained.

[0122] The following application example is used to illustrate the preparation method of the heat-responsive safety lithium ion battery of the present application

[0123] Application Example 1

[0124] (1) 25wt% of vinylene carbonate was added into 1M LiPF6 electrolyte with a combination of EC, DMC, EMC (V EC :V DMC :V EMC = 1:1:1) to obtain a thermally responsive electrolyte;

[0125] (2) A commercialized lithium iron phosphate positive electrode, a commercialized graphite negative electrode, the thermally responsive electrolyte and the thermally responsive safety separator prepared in example 1 were assembled into a battery to obtain a thermally responsive safety lithium ion battery.

[0126] Application Examples 2-7

[0127] The same method as application example 1 was used, except that in step (2), the thermally responsive safety separator prepared in example 1 was replaced by the thermally responsive safety separator prepared in example 2, example 3, example 4, example 5, example 6, example 7, respectively.

[0128] A thermally responsive safety lithium ion battery was obtained.

[0129] Comparative Application Examples 1-2

[0130] The same method as application example 1 was used, except that in step (2), the thermally responsive safety separator prepared in example 1 was replaced by the thermally responsive safety separator prepared in comparative example 1, comparative example 2, respectively.

[0131] A thermally responsive safety lithium ion battery was obtained.

[0132] Comparative Application Example 3

[0133] The same method as in application example 1, except that in step (2), the thermal response safety separator prepared in example 1 is replaced by commercial Celgard 2400 separator, and the electrolyte used is 1M LiPF6 combined with EC, DMC, EMC (V EC :V DMC :V EMC =1:1:1)+25wt% of vinylene carbonate+1wt% of dibenzoyl peroxide.

[0134] A thermal response safety lithium ion battery is obtained.

[0135] Comparative application example 4

[0136] The same method as in application example 1, except that in step (1), the thermal response electrolyte is replaced by commercial lithium ion battery electrolyte.

[0137] A thermal response safety lithium ion battery is obtained.

[0138] Test example

[0139] The thermal response safety lithium ion battery prepared above is tested for performance, including battery cycle performance test, battery rate performance test, battery energy efficiency test, and battery thermal response safety test. Among them:

[0140] Battery cycle performance test: using Wuhan Lan electric Land charge-discharge tester for charge-discharge test, specifically: in the voltage range of 2.5-3.65V, first activated three times at 0.1C rate, then charged and discharged at 0.5C rate for 50 cycles, the test results are shown in Figure 1 . It can be seen from Figure 1 that the cycle performance of the thermal response safety lithium ion battery prepared in application examples 1-7 of the present application does not deteriorate significantly, and is better than the effect of using commercial Celgard 2400 separator and electrolyte containing initiator and thermal response monomer in comparative application example 3, which shows that the thermal response separator used is compatible with the battery system, and there is no problem of easy cycle performance deterioration in the prior art.

[0141] Battery rate performance test: using Wuhan Lan electric Land charge-discharge tester for test, specifically: after 3 weeks of activation at 0.1C in the voltage range of 2.5-3.65V, then 5 weeks of cycle at 1C, 2C, 3C, 1C rate in turn, the test results are shown in Figure 2 . It can be seen from Figure 2It can be seen that the rate performance of the thermally responsive safe lithium-ion batteries prepared in Application Examples 1-7 of the present invention does not deteriorate significantly, and is significantly better than the effect of the commercial Celgard 2400 separator and electrolyte containing initiator and thermally responsive monomer in Comparative Application Example 3. This indicates that the thermally responsive separator used has good compatibility with the battery system and does not have the problem of deteriorating rate performance that is easily caused by the prior art.

[0142] Battery energy efficiency testing: The Wuhan Land charge / discharge tester was used for testing. Specifically, activation was performed within a voltage range of 2.5-3.65V at 0.5C for three cycles, and the average energy efficiency was calculated. The formula for calculating energy efficiency is: (Total discharge energy of 3 cycles at 0.5C / Total charging energy of 3 cycles at 0.5C) × 100%. Test results are shown below. Figure 3 .Depend on Figure 3 It can be seen that the energy efficiency of the thermally responsive safe lithium-ion batteries prepared in Application Examples 1-7 of the present invention does not decrease significantly and is significantly better than the effect of the commercial Celgard 2400 separator and electrolyte containing initiator and thermally responsive monomer in Comparative Application Example 3. This indicates that the thermally responsive separator used has good compatibility with the battery system and does not have the problem of energy efficiency degradation that is easily caused by the prior art.

[0143] Battery thermal response safety test: The test was conducted using the Wuhan Land charge / discharge tester. Specifically, an external heating test was performed under full charge conditions, and the internal impedance change of the battery was monitored in real time using AC impedance testing. The heating temperature was 120℃, and the heating time was 2 minutes. The test results are shown below. Figure 4 .Depend on Figure 4 It can be seen that the thermally responsive safe lithium-ion batteries prepared in Application Examples 1-7 of the present invention can respond quickly under external overheating conditions, the battery impedance increases earlier and faster, and the final impedance value is also significantly higher than that of Comparative Application Examples 1-4. This shows that the safety performance of the prepared thermally responsive safe lithium-ion batteries is significantly better than that of existing technologies and comparative examples not included in the technical solutions of the present invention.

[0144] The present invention exemplarily in Figure 5 The document provides scanning electron microscope (SEM) images of microspheres A prepared in Example 1 at different magnifications; Figure 5 It can be seen that the microspheres A prepared by method 1 have uniform morphology, intact structure, and no damage, and the particle size D is uniform. 50 The particle size is between 0.05 and 5 μm. This indicates that, in the preferred embodiment of the present invention, when porous and hollow mesoporous material microspheres with a particle size of 0.05-5 μm are used as the core and shell, an initiator is used as the core to fill the hollow mesoporous material, and a phase change material is used to block the pores, thereby preparing microspheres A with a constant particle size.

[0145] It can be seen from the above results that the heat-responsive safety separator formed by the slurry coating provided by the application applied to the lithium ion battery containing thermal polymerization monomers can realize fast heat response on the basis of ensuring cycle performance, rate performance and energy efficiency, significantly improve the safety performance of the battery, and does not have the problem of serious deterioration of the electrical performance in the prior art.

[0146] The preferred embodiments of the application are described in detail above, but the application is not limited thereto. Within the technical concept of the application, various simple modifications can be made to the technical solutions of the application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the application and fall within the protection scope of the application.

Claims

1. A slurry for battery separators, characterized in that, The slurry contains microspheres A and B, thickeners, and binders; Wherein, based on the total weight of the slurry, the content of microsphere A is 30-50 wt%, the content of microsphere B is 25-48 wt%, the content of thickener is 5-15 wt%, and the content of binder is 3-17 wt%; The material forming microsphere A includes initiator A; the material forming microsphere B includes initiator B; The initiator A is a peroxide; The initiator B is selected from at least one of oxalic acid, glucose, N,N-dimethylaniline, naphthenate, n-dodecyl mercaptan, triethylaluminum, and triethylboron; The particle size D of microspheres A and B 50 Each is independently 0.05-5μm; The materials forming microspheres A and B further include hollow mesoporous materials and phase change materials; wherein, The hollow mesoporous material is selected from silica and / or polymer I with a weight-average molecular weight of 10,000 to 1,000,000, wherein polymer I is selected from at least one of polymethyl acrylate, polymethyl methacrylate, polyamide and polystyrene; The phase change material is selected from at least one of hydrated sulfate, n-dodecyl mercaptan, n-docosahexanes, 6-methyldodecane, 8-methyldocosahexanes, and polymer ⅠⅠ with a weight average molecular weight of 0.2 million to 50,000, wherein the polymer ⅠⅠ is selected from at least one of polyethylene, polypropylene, polyethylene glycol, and polyoxymethylene.

2. The slurry according to claim 1, wherein, The peroxide is selected from at least one of cumene hydroperoxide, tert-butyl hydroperoxide, dicumene peroxide, di-tert-butyl peroxide, benzoyl peroxide, dodecyl peroxide, tert-butyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxyvalerate, diisopropyl peroxide, and dicyclohexyl peroxide. And / or, the initiator B is selected from at least one of N,N-dimethylaniline, n-dodecyl mercaptan, and glucose.

3. The slurry according to claim 1, wherein, The particle size D of the hollow mesoporous material 50 It ranges from 0.05 to 5 μm.

4. The slurry according to claim 1 or 3, wherein, The microspheres A are prepared by a method comprising the following steps: (1) In the presence of ethanol, the phase change material and initiator A are contacted and mixed to obtain a mixed solution; (2) The mixed solution is contact-mixed with the hollow mesoporous material to obtain the microsphere A.

5. The slurry according to claim 4, wherein, The weight ratio of the phase change material, the initiator A, and the hollow mesoporous material is 1:0.2-0.7:0.05-0.

15.

6. The slurry according to claim 4, wherein, The conditions for contact mixing I include: a temperature of 30-60℃ and a time of 5-15 min; And / or, the conditions for the contact mixing ⅠⅠ include: a temperature of 30-60℃ and a time of 45-75min.

7. A thermally responsive safety diaphragm, characterized in that, The diaphragm includes a base membrane and a heat-responsive safety coating applied to the upper and lower surfaces of the base membrane; The thermally responsive safety coating is formed from the slurry for battery separators as described in any one of claims 1-6.

8. The application of the thermally responsive safety separator as described in claim 7 in lithium-ion batteries.

9. A thermally responsive, safe lithium-ion battery, characterized in that, The lithium-ion battery includes: a positive electrode, a negative electrode, a thermally responsive electrolyte, and a thermally responsive safety membrane; the thermally responsive electrolyte contains thermally polymerized monomers. The thermally responsive safety diaphragm is the thermally responsive safety diaphragm as described in claim 7.

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