Diaphragm coating slurry composition and preparation method thereof, diaphragm and preparation method thereof, and lithium battery

Abstract

The invention relates to a diaphragm coating slurry composition and a preparation method thereof, a diaphragm and a preparation method thereof, and a lithium battery. The diaphragm coating slurry composition comprises the following components in parts by mass: 5-10 parts of PAA microspheres; 2 to 15 parts of a conductive carbon-based material; 0.01 to 1 part of a first dispersant; 0.01 to 1 part of a second dispersant; 1 to 2 parts of a defoaming agent; 12 to 20 parts of a binder; and 80 to 90 parts of a solvent. The combination of the components and the mass fraction range of each component are determined through a large number of tests, and the combination and the mass fraction range enable a diaphragm coating formed by the diaphragm coating slurry composition to effectively improve the cycling stability and the safety performance of a lithium battery, so that the diaphragm coating slurry composition is beneficial to wide application.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a diaphragm coating slurry composition and a preparation method thereof, a diaphragm and a preparation method thereof, and a lithium battery. Background Art

[0002] In recent years, due to resource and environmental issues, lithium batteries have become the focus of development in the field of new energy. As one of the core components of lithium batteries, lithium battery separators can prevent short circuits between the positive and negative electrodes of the battery on the one hand, and transmit free ions on the other hand. The performance of the separator will greatly affect the rate performance, charge and discharge function, cycle life, etc. of the battery, so the separator is required to have good insulation performance, mechanical strength, chemical stability, and thermal stability.

[0003] At present, the research on improving the performance of lithium battery diaphragms is mainly focused on diaphragm surface modification and the development of new diaphragm materials. Coating diaphragms is considered to be an effective way to improve the safety of lithium batteries and has been widely used in 3C, power and energy storage battery fields. PVDF coated diaphragms have good wettability and liquid retention. At the same time, they can improve the adhesion between the diaphragm and the pole piece during the manufacturing process, and can enhance the cycle stability, electrochemical stability and battery safety of the diaphragm. Considering the cost and controllability, the parallel replacement of PVDF with PAA microspheres has become an effective way. However, PAA microspheres have good insulation properties, which is not conducive to the transfer of potential. Therefore, the cycle stability and safety performance of lithium batteries that only use PAA microspheres as diaphragm coating materials are poor. Summary of the invention

[0004] Based on this, it is necessary to provide a diaphragm coating slurry composition and a preparation method thereof, a diaphragm and a preparation method thereof, and a lithium battery in order to improve the cycle stability and safety performance of lithium batteries.

[0005] A diaphragm coating slurry composition, which comprises the following components in parts by mass:

[0006]

[0007] Compared with the traditional PAA microsphere coating slurry, the above-mentioned diaphragm coating slurry composition of the technical solution of the present invention also includes a conductive carbon material, which helps to form an effective conductive path; in addition, the first dispersant helps to disperse the PAA microspheres, the second dispersant helps to disperse the conductive carbon material, the defoamer helps to prevent the generation of foam in the system, the binder helps to bond the components, and the solvent is used to dissolve the components. The combination of these components and the above-mentioned mass fraction range of each component are determined through a large number of tests. The above-mentioned combination and mass fraction range enable the diaphragm coating formed by the diaphragm coating slurry composition of the present invention to effectively improve the cycle stability and safety performance of lithium batteries, which is conducive to wide application.

[0008] In a feasible implementation, the conductive carbon material is selected from at least one of ordinary carbon black, acetylene black, Ketjen black, superconductive carbon black, graphite, conductive carbon fiber, graphene and carbon nanotubes; and / or

[0009] The first dispersant and the second dispersant are independently selected from at least one of maleic anhydride, methacrylic acid, polyacrylate, vinylbenzenesulfonic acid, polystyrene maleic anhydride copolymer ammonium salt, polyoxyethylene ether and naphthylphenol polyoxyethylene ether; and / or

[0010] The defoamer is selected from at least one of silicone defoamers, polyether defoamers and polyvinyl alcohol defoamers; and / or

[0011] The binder is selected from at least one of polyacrylates, polyacrylonitrile, polyvinyl alcohol and styrene-butadiene rubber; and / or

[0012] The solvent is deionized water.

[0013] A method for preparing the above-mentioned diaphragm coating slurry composition comprises the following steps:

[0014] The PAA microspheres, the first dispersant, the defoamer and the solvent are uniformly mixed according to the weight ratio to obtain a first slurry;

[0015] Evenly mixing the first slurry, the conductive carbon-based material and the second dispersant to obtain a second slurry; and

[0016] The second slurry is mixed evenly with the binder, filtered and demagnetized to obtain a diaphragm coating slurry composition.

[0017] The preparation method of the diaphragm coating slurry composition is simple in process, and the diaphragm coating formed by the prepared diaphragm coating slurry composition can effectively improve the cycle stability and safety performance of lithium batteries, which is conducive to wide application.

[0018] A separator, comprising a base film, at least one surface of the base film being covered with a coating, the coating being prepared from the above-mentioned separator coating slurry composition.

[0019] It has been proven through experiments that the separator of the technical solution of the present invention is beneficial to improving the cycle stability and safety performance of lithium batteries.

[0020] In a feasible implementation, an inorganic layer is further provided between the base film and the coating.

[0021] In a feasible implementation, the material of the inorganic layer is selected from at least one of inorganic ceramic materials and solid electrolyte materials;

[0022] The inorganic ceramic materials are selected from at least one of Al2O3, SiO2, TiO2, AlO(OH)n, CeO2, MgO, ZrO2, MgAl2O4, molecular sieve, BaTiO3, MFI zeolite, LiTi2(PO4)3, LiAlO2 and Li 0.1 Ca 0.9 TiO3;

[0023] The solid electrolyte material is selected from oxide solid electrolytes and halide solid electrolytes; the oxide solid electrolytes are selected from LiM x O y type solid electrolytes and phosphate type solid electrolytes Li a N b PO c R d wherein M is selected from at least one of B, C, N, Al, P, S, I, Si, Ge, Zr, Ti, Zn, Fe, Ta, As, V, Cr and La, 0.6 < x < 10, 1 < y < 8; wherein N is selected from Al, Ti, V, Fe, Co or Zr, R is selected from F, Cl, Br or I, 0.1 < a < 3, 0.5 < b < 4, 3 < c < 5, 0 ≤ d ≤ 2; the chemical formula of the halide solid electrolyte is Li3MX6, wherein X is selected from Cl, Br or I, and M is selected from Y, In, Mg or Zr.

[0024] A method for preparing a separator, comprising the following steps:

[0025] Coat the above-mentioned separator coating slurry composition on at least one surface of the base film, and obtain the separator after drying.

[0026] The method for preparing the separator of the above implementation has a simple process. It has been proven through experiments that the separator obtained by the method for preparing the separator of the technical solution of the present invention is beneficial to improving the cycle stability and safety performance of lithium batteries.

[0027] In a feasible implementation, the following steps are included:

[0028] An inorganic layer is formed on at least one side of the base film, and then the above-mentioned diaphragm coating slurry composition is coated on the inorganic layer, and then the diaphragm is obtained after drying.

[0029] A lithium battery comprises any one of the above-mentioned separators.

[0030] Experiments have shown that the lithium battery of the present invention has good cycle stability and safety performance.

[0031] In a feasible implementation, the lithium battery further includes a negative electrode, and the side of the separator having the coating is opposite to the negative electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flow chart of a method for preparing the above-mentioned diaphragm coating slurry composition according to one embodiment of the present invention;

[0033] Figure 2 is a schematic diagram of a diaphragm according to one embodiment of the present invention;

[0034] Figure 3 It is a schematic diagram of a diaphragm according to another embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0037] The diaphragm coating slurry composition of one embodiment includes the following components in parts by mass:

[0038]

[0039] Among them, PAA microspheres refer to polyacrylic acid microspheres. PAA microspheres can be in an emulsion state or a powder state, preferably in an emulsion state, in which case the PAA microspheres are better dispersed in the entire slurry composition. Preferably, the D50 of the PAA microspheres is 200nm to 1μm. It is understood that the size of the PAA microspheres is not limited thereto. In addition, the PAA microspheres can be homemade or purchased.

[0040] Among them, the conductive carbon-based material refers to a carbon-based material with conductive function, and the conductive carbon-based material helps to form an effective conductive path.

[0041] In addition, in the above-mentioned diaphragm coating slurry composition, the first dispersant helps to disperse the PAA microspheres, the second dispersant helps to disperse the conductive carbon-based material, the defoamer helps to prevent the generation of foam in the system, the binder helps to bond the components, and the solvent is used to dissolve the components.

[0042] The combination of the components in the above-mentioned diaphragm coating slurry composition and the above-mentioned mass fraction range of each component are determined through a large number of experiments. The above-mentioned combination and mass fraction range enable the diaphragm coating formed by the diaphragm coating slurry composition of the present invention to effectively improve the cycle stability and safety performance of the lithium battery, which is conducive to wide application.

[0043] On the basis of the aforementioned implementation manner, the conductive carbon-based material is selected from at least one of ordinary carbon black, acetylene black, Ketjen black, superconductive carbon black, graphite, conductive carbon fiber, graphene and carbon nanotubes.

[0044] Based on the above embodiment, the first dispersant and the second dispersant are independently selected from at least one of maleic anhydride, methacrylic acid, polyacrylate, vinylbenzenesulfonic acid, polystyrene maleic anhydride copolymer ammonium salt, polyoxyethylene ether and naphthylphenol polyoxyethylene ether.

[0045] Based on the above embodiment, the defoaming agent is selected from at least one of a silicone defoaming agent, a polyether defoaming agent and a polyvinyl alcohol defoaming agent.

[0046] Based on the above-mentioned embodiment, the binder is selected from at least one of polyacrylates, polyacrylonitrile, polyvinyl alcohols and styrene-butadiene rubber.

[0047] Based on the above embodiment, the solvent is deionized water.

[0048] Experiments have shown that the above combination and mass fraction range enable the diaphragm coating formed by the diaphragm coating slurry composition of the present invention to effectively improve the cycle stability and safety performance of lithium batteries, which is conducive to wide application.

[0049] See also Figure 1The method for preparing the above-mentioned diaphragm coating slurry composition according to one embodiment of the present invention comprises the following steps:

[0050] S10. Evenly mix the PAA microspheres, the first dispersant, the defoaming agent and the solvent according to their weight fractions to obtain a first slurry.

[0051] In step S10, the operation of uniformly mixing the PAA microspheres, the first dispersant, the defoamer and the solvent is as follows: the PAA microspheres, the first dispersant, the defoamer and the solvent are stirred in a disperser, and the stirring time is maintained at 10 min to 60 min, and the stirring speed is 1000 r / min to 2000 r / min. After the above mixing operation, a first slurry with good dispersion is obtained.

[0052] S20, uniformly mixing the first slurry obtained in step S10, the conductive carbon-based material and the second dispersant to obtain a second slurry.

[0053] In step S20, the first slurry, the conductive carbon material and the second dispersant obtained in step S10 are uniformly mixed by stirring the first slurry, the conductive carbon material and the second dispersant in a disperser, maintaining the stirring time for 30 min to 120 min and the stirring speed for 2000 r / min to 3000 r / min. After the above mixing operation, a second slurry with good dispersion is obtained.

[0054] S30, mixing the second slurry obtained in step S20 with a binder uniformly, filtering and demagnetizing the mixture, and obtaining a diaphragm coating slurry composition.

[0055] In step S30, filtering can remove large solid particles in the slurry, and conventional demagnetization means can be used for demagnetization. After the above filtering and demagnetization operations, a well-dispersed diaphragm coating slurry composition is obtained.

[0056] The preparation method of the diaphragm coating slurry composition is simple in process, and the diaphragm coating formed by the prepared diaphragm coating slurry composition can effectively improve the cycle stability and safety performance of lithium batteries, which is conducive to wide application.

[0057] See also Figure 2 A diaphragm 100 according to an embodiment includes a base film 110 , one side of the base film 110 is covered with a coating 120 , and the coating 120 is prepared from the above-mentioned diaphragm coating slurry composition.

[0058] On the basis of the above-mentioned embodiment, the base film 110 is a polyethylene film or a polypropylene film; the thickness of the base film 110 is 9 μm to 12 μm; the thickness of the coating layer 120 is 1 μm to 4 μm.

[0059] It should be noted that, in the diaphragm of the present invention, at least one side of the base film is covered with a coating, which means that one side or both sides of the base film are covered with a coating. When both sides of the base film are covered with a coating, the thickness of the coating on both sides may be the same or different.

[0060] See also Figure 3 In another embodiment, the diaphragm 200 includes a base film 210 and a coating layer 220 covering one side of the base film 210 . In addition, an inorganic layer 230 is disposed between the base film 210 and the coating layer 220 .

[0061] In addition, when both sides of the base film 210 are covered with the coating 220 , the inorganic layer 230 can be coated between the base film 210 and the coating 220 on both sides, or the inorganic layer 230 can be coated on one side of the base film 210 .

[0062] In the above embodiment of the diaphragm 200, the base film 210, the inorganic layer 230 and the coating 220 are stacked in sequence, which is more conducive to improving the cycle stability and safety performance of the lithium battery. In addition, the base film 210 such as polyethylene film and polypropylene film are all non-polar polymer films, which have poor compatibility with polar electrolytes. By covering with the above inorganic layer 230, the lyophilicity of the base film 210 and the electrolyte can be increased, so that the liquid holding rate of the diaphragm is greatly increased.

[0063] Based on the above-mentioned embodiment, the thickness of the inorganic layer 230 is 1 μm to 4 μm.

[0064] On the basis of the above-mentioned embodiments, the material of the inorganic layer 230 is selected from at least one of an inorganic ceramic material and a solid electrolyte material.

[0065] Based on the above embodiments, the inorganic ceramic material is selected from Al2O3, SiO2, TiO2, AlO(OH)n, CeO2, MgO, ZrO2, MgAl2O4, molecular sieve, BaTiO3, MFI zeolite, LiTi2(PO4)3, LiAlO2 and Li 0.1 Ca 0.9 At least one of TiO3.

[0066] On the basis of the above-mentioned embodiment, the solid electrolyte material is selected from oxide solid electrolyte and halide solid electrolyte; the oxide solid electrolyte is selected from LiM x O y Type solid electrolyte and phosphate type solid electrolyte Li a N b PO c R dat least one of them, where M is selected from at least one of B, C, N, Al, P, S, I, Si, Ge, Zr, Ti, Zn, Fe, Ta, As, V, Cr and La, 0.6 < x < 10, 1 < y < 8; where N is selected from Al, Ti, V, Fe, Co or Zr, R is selected from F, Cl, Br or I, 0.1 < a < 3, 0.5 < b < 4, 3 < c < 5, 0 ≤ d ≤ 2; the chemical formula of the halide solid electrolyte is Li3MX6, where X is selected from Cl, Br or I, and M is selected from Y, In, Mg or Zr.

[0067] It has been proven through experiments that the separator of the technical solution of the present invention is beneficial to improving the cycle stability and safety performance of lithium batteries.

[0068] A method for preparing a separator according to an embodiment includes the following steps:

[0069] Coat the above-mentioned separator coating slurry composition on at least one surface of the base film, and obtain the separator after drying.

[0070] Among them, the separator coating slurry composition can be coated on the film to be coated by methods such as roll coating or spin coating, preferably roll coating. Among them, the film to be coated can be a base film or a separator pre-coated with an inorganic layer.

[0071] A method for preparing a separator according to an embodiment includes the following steps:

[0072] Form an inorganic layer on at least one surface of the base film, and then coat the above-mentioned separator coating slurry composition on the inorganic layer, and obtain the separator after drying.

[0073] Based on the foregoing embodiment, the operation of forming an inorganic layer on at least one surface of the base film is: coat an inorganic layer slurry on at least one surface of the base film, and form an inorganic layer after the slurry dries. Among them, the coating speed of the inorganic layer slurry is 40 m / min to 120 m / min.

[0074] Based on the foregoing embodiment, the coating speed of the separator coating slurry composition is 40 m / min to 120 m / min; the drying temperature is 40 °C to 120 °C, and the drying time is 1 min to 100 min. Among them, the drying operation can be carried out in a vacuum oven.

[0075] The method for preparing the separator according to the above embodiment has a simple process. It has been proven through experiments that the separator obtained by the method for preparing the separator of the technical solution of the present invention is beneficial to improving the cycle stability and safety performance of lithium batteries.

[0076] A lithium battery according to an embodiment includes the separator according to any one of the above.

[0077] On the basis of the above-mentioned embodiment, the lithium battery further includes a negative electrode, and the side of the separator having the coating is opposite to the negative electrode. In this case, it is more conducive to improving the cycle stability and safety performance of the lithium battery.

[0078] Experiments have shown that the lithium battery of the present invention has good cycle stability and safety performance.

[0079] With reference to the above implementation contents, in order to make the technical solution of the present application more specific, clear and easy to understand, the technical solution of the present application is now exemplified. However, it should be noted that the contents to be protected by the present application are not limited to the following embodiments 1 to 5.

[0080] Example 1

[0081] Add 0.125 kg of sodium vinylbenzene sulfonate and 0.11 kg of fluorinated alkyl phosphate to 37.02 kg of deionized water, stir well and then add 6.0 kg of PAA microspheres (particle size of 1 μm to 10 μm) powder, stir well and disperse to obtain a first slurry;

[0082] Then, 0.25 kg of polystyrene maleic anhydride copolymer ammonium salt was added to the first slurry, and then 2.5 kg of conductive carbon black Super P was added, and the mixture was further stirred and dispersed to obtain a second slurry;

[0083] Then, 4.0 kg of polyacrylate polymer was added to the second slurry, and the mixture was stirred and mixed thoroughly, and then filtered through a high-mesh filter and demagnetized to obtain the diaphragm coating slurry composition of Example 1;

[0084] Then, the membrane coating slurry composition was coated on one side of the PP base film by an anilox roller coating process, and baked in an oven at 50° C. for 1 min to form a coating of 1.5 μm, thereby obtaining the membrane of Example 1.

[0085] The diaphragm obtained in Example 1 was prepared into a lithium battery, the positive electrode material of the lithium battery was lithium iron phosphate, the negative electrode material was graphite, wherein one side of the diaphragm was coated with a PAA microsphere coating and the side was opposite to the negative electrode sheet. After hot pressing, the bonding effect between the diaphragm and the negative electrode sheet of the lithium battery was good, and the peeling strength was high.

[0086] Example 2

[0087] Add 0.125 kg of sodium vinylbenzene sulfonate and 0.11 kg of fluorinated alkyl phosphate to 37.52 kg of deionized water, stir well and then add 6.0 kg of PAA microsphere powder, stir well and disperse to obtain a first slurry;

[0088] Then, 0.25 kg of polystyrene maleic anhydride copolymer ammonium salt was added to the first slurry, and then 2.0 kg of conductive carbon black Super P was added, and the mixture was further stirred and dispersed to obtain a second slurry;

[0089] Then, 4.0 kg of polyacrylate polymer was added to the second slurry, and the mixture was stirred and mixed thoroughly, and then filtered through a high-mesh filter and demagnetized to obtain the diaphragm coating slurry composition of Example 2;

[0090] Then, the diaphragm coating slurry composition was coated on the PP base film pre-coated with LATP solid electrolyte by an anilox roller coating process, and baked in an oven at 50° C. for 1 min to form a 1.5 μm coating to obtain the diaphragm of Example 2.

[0091] The diaphragm obtained in Example 2 was prepared into a lithium battery, the positive electrode material of the lithium battery was lithium iron phosphate, and the negative electrode material was graphite, wherein one side of the diaphragm was coated with a PAA microsphere coating and the side was opposite to the negative electrode sheet.

[0092] Example 3

[0093] 0.125 kg of sodium vinylbenzene sulfonate and 0.11 kg of fluorinated alkyl phosphate were added to 38.02 kg of deionized water, and after fully stirring, 6.0 kg of PAA microsphere powder was added, and after fully stirring and dispersing, a first slurry was obtained;

[0094] Then, 0.25 kg of polystyrene maleic anhydride copolymer ammonium salt was added to the first slurry, and then 1.5 kg of conductive carbon black Super P was added, and the mixture was further stirred and dispersed to obtain a second slurry;

[0095] Then, 4.0 kg of polyacrylate polymer was added to the second slurry, and the mixture was stirred and mixed thoroughly, and then filtered through a high-mesh filter and demagnetized to obtain the diaphragm coating slurry composition of Example 3;

[0096] Then, the membrane coating slurry composition was coated on the PP base film pre-coated with an aluminum oxide coating (coating thickness was 2 μm) by an anilox roller coating process, and baked in a 50° C. oven for 1 min to form a 1.5 μm coating, thereby obtaining the membrane of Example 3.

[0097] The diaphragm obtained in Example 3 was prepared into a lithium battery, the positive electrode material of the lithium battery was lithium iron phosphate, and the negative electrode material was graphite, wherein one side of the diaphragm was coated with a PAA microsphere coating and the side was opposite to the negative electrode sheet.

[0098] Example 4

[0099] Add 0.125 kg of sodium vinylbenzene sulfonate and 0.11 kg of fluorinated alkyl phosphate to 37.52 kg of deionized water, stir well and then add 6.0 kg of PAA microsphere powder, stir well and disperse to obtain a first slurry;

[0100] Then, 0.25 kg of polystyrene maleic anhydride copolymer ammonium salt was added to the first slurry, and then 1.5 kg of conductive carbon black Super P and 0.5 kg of carbon nanotubes were added, and the mixture was further stirred and dispersed to obtain a second slurry;

[0101] Then, 4.0 kg of polyacrylate polymer was added to the second slurry, and the mixture was stirred and mixed thoroughly, and then filtered through a high-mesh filter and demagnetized to obtain the diaphragm coating slurry composition of Example 4;

[0102] Then, the membrane coating slurry composition was coated on one side of the PP base film by an anilox roller coating process, and baked in an oven at 50° C. for 1 min to form a coating of 1.5 μm, thereby obtaining the membrane of Example 4.

[0103] The diaphragm obtained in Example 4 was prepared into a lithium battery, the positive electrode material of the lithium battery was lithium iron phosphate, and the negative electrode material was graphite, wherein one side of the diaphragm was coated with a PAA microsphere coating and the side was opposite to the negative electrode sheet.

[0104] Example 5

[0105] Add 0.125 kg of sodium vinylbenzene sulfonate and 0.11 kg of fluorinated alkyl phosphate to 37.52 kg of deionized water, stir well and then add 6.0 kg of PAA microsphere powder, stir well and disperse to obtain a first slurry;

[0106] Then, 0.25 kg of polystyrene maleic anhydride copolymer ammonium salt was added to the first slurry, and then 1.0 kg of conductive carbon black Super P and 1.0 kg of carbon nanotubes were added, and the mixture was further stirred and dispersed to obtain a second slurry;

[0107] Then, 4.0 kg of polyacrylate polymer was added to the second slurry, and the mixture was stirred and mixed thoroughly, and then filtered through a high-mesh filter and demagnetized to obtain the diaphragm coating slurry composition of Example 5;

[0108] Then, the membrane coating slurry composition was coated on one side of the PP base film by an anilox roller coating process, and baked in an oven at 50° C. for 1 min to form a coating of 1.5 μm, thereby obtaining the membrane of Example 5.

[0109] The diaphragm obtained in Example 5 was prepared into a lithium battery, the positive electrode material of the lithium battery was lithium iron phosphate, and the negative electrode material was graphite, wherein one side of the diaphragm was coated with a PAA microsphere coating and the side was opposite to the negative electrode sheet.

[0110] Comparative Example 1

[0111] This comparative example is a comparative example of Example 1, and provides a diaphragm coating slurry composition and a preparation method thereof, a diaphragm and a preparation method thereof, and a battery cell and a preparation method thereof. The specific production process is as follows:

[0112] To 39.52 kg of deionized water, 0.125 kg of sodium vinylbenzene sulfonate and 0.11 kg of fluorinated alkyl phosphate were added, and after fully stirring, 6.0 kg of PAA microsphere powder was added. After fully stirring and dispersing, 0.25 kg of polystyrene maleic anhydride copolymer ammonium salt was added, and 4.0 kg of polyacrylate polymer was added. After fully stirring and mixing, the mixture was filtered through a high-mesh filter and demagnetized to obtain the diaphragm coating slurry composition of Comparative Example 1.

[0113] The above-mentioned diaphragm coating slurry composition was coated on one side of the PP base film by an anilox roller coating process, and baked in a 50° C. oven for 1 min to form a 1.5 um coating, thereby obtaining the diaphragm of Comparative Example 1.

[0114] The diaphragm obtained in Comparative Example 1 was prepared into a lithium battery, the positive electrode material of the lithium battery was lithium iron phosphate, the negative electrode material was graphite, wherein one side of the diaphragm was coated with a PAA microsphere coating and the side was opposite to the positive electrode sheet. After hot pressing, the bonding effect between the diaphragm and the positive electrode sheet of the lithium battery was good, and the peeling strength was high.

[0115] Performance Testing:

[0116] (1) The separators of Examples 1 to 5 and Comparative Example 1 were subjected to a hot press peeling force test. The test method is as follows. The test results are shown in Table 1.

[0117] Hot pressing peeling force test: hot pressing machine, 100℃ / 1min, hot pressing the diaphragm and the positive electrode sheet with a pressure of 1MPa before peeling test. Sample preparation: Cut the diaphragm with an area of ​​1.5cm and 20cm, and use the peeling test machine to perform the peeling test at an angle of 180° and a speed of 300mm / min.

[0118] (2) The capacity retention rate and safety performance of the battery cells of Examples 1 to 5 and Comparative Example 1 were tested. The test method is as follows. The test results are shown in Table 1.

[0119] Capacity retention rate test: The battery is first charged and discharged three times in a standard manner to obtain the standard capacity C1 of the battery, and then charged in a standard manner. After charging, it is stored at a certain temperature (room temperature 25°C) for 28 days, and then discharged at a standard discharge rate to obtain the discharge capacity C2. The capacity retention rate = C2 / C1.

[0120] Safety performance test: Charge the battery in a standard way, and use a φ5mm~φ8mm high temperature resistant steel needle to penetrate the battery plate perpendicularly at a speed of 25±5mm / s. Observe for 1 hour. If the battery does not catch fire or explode, it passes the test. Perform 10 sets of tests in parallel. If the pass rate is >95%, it is excellent; if the pass rate is >80%, it is excellent; if the pass rate is >50%, it is good.

[0121] Table 1 Performance test results of the diaphragms and cells of Examples 1 to 5 and Comparative Example 1

[0122] project Hot press peeling force Capacity retention rate Safety performance Comparative Example 1 16.8N / m 84.46％ good Example 1 9.8N / m 88.45％ excellent Example 2 8.3N / m 91.45％ excellent Example 3 8.5N / m 88.56％ excellent Example 4 7.6N / m 84.65％ excellent Example 5 7.9N / m 84.47％ good

[0123] It can be seen from Table 1 that the hot pressing bonding force between the diaphragm of Comparative Example 1 and the negative electrode sheet is relatively strong, while after the carbon-based materials are added to the diaphragms of Examples 1 to 5, a certain contact potential of the coating is occupied by the carbon material, and effective bonding force cannot be provided during the hot pressing process; on the other hand, compared with the battery cell of Comparative Example 1, the addition of conductive carbon or carbon nanotubes to the battery cells of Examples 1 to 5 can enhance the cycle stability of the battery cells to a certain extent, especially for solid electrolyte pre-coated diaphragms, the addition of carbon-based conductive materials can significantly improve the cycle stability and safety performance of the battery cells.

[0124] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0125] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A membrane coating slurry composition, It is characterized in that The diaphragm coating slurry composition comprises the following components in parts by mass:

2. The diaphragm coating slurry composition according to claim 1, It is characterized in that The conductive carbon material is selected from at least one of ordinary carbon black, acetylene black, Ketjen black, superconductive carbon black, graphite, conductive carbon fiber, graphene and carbon nanotubes; and / or The first dispersant and the second dispersant are independently selected from at least one of maleic anhydride, methacrylic acid, polyacrylate, vinylbenzenesulfonic acid, polystyrene maleic anhydride copolymer ammonium salt, polyoxyethylene ether and naphthylphenol polyoxyethylene ether; and / or The defoamer is selected from at least one of silicone defoamers, polyether defoamers and polyvinyl alcohol defoamers; and / or The binder is selected from at least one of polyacrylates, polyacrylonitrile, polyvinyl alcohol and styrene-butadiene rubber; and / or The solvent is deionized water.

3. A method for preparing the diaphragm coating slurry composition according to claim 1 or 2, It is characterized in that The steps include: The PAA microspheres, the first dispersant, the defoamer and the solvent are uniformly mixed according to the weight ratio to obtain a first slurry; Evenly mixing the first slurry, the conductive carbon-based material and the second dispersant to obtain a second slurry; and The second slurry is mixed evenly with the binder, filtered and demagnetized to obtain a diaphragm coating slurry composition.

4. A diaphragm, It is characterized in that It comprises a base film, at least one side of which is covered with a coating, and the coating is prepared from the diaphragm coating slurry composition according to claim 1 or 2.

5. The diaphragm according to claim 4, It is characterized in that An inorganic layer is also arranged between the base film and the coating layer.

6. The diaphragm according to claim 5, It is characterized in that The material of the inorganic layer is selected from at least one of an inorganic ceramic material and a solid electrolyte material; The inorganic ceramic material is selected from Al 2 O 3 、SiO 2 、TiO 2 、AlO(OH)n、CeO 2 、MgO、ZrO 2 MgAl 2 O 4 , molecular sieve, BaTiO 3 、MFI zeolite、LiTi 2 (PO 4 ) 3 、LiAlO 2 With Li 0.1 Ca 0.9 TiO 3 At least one of; The solid electrolyte material is selected from oxide solid electrolytes and halide solid electrolytes; the oxide solid electrolytes are selected from LiM x O y -type solid electrolytes and phosphate-type solid electrolytes Li a N b PO c R d at least one of them, where M is selected from at least one of B, C, N, Al, P, S, I, Si, Ge, Zr, Ti, Zn, Fe, Ta, As, V, Cr and La, 0.6 < x < 10, 1 < y < 8; where N is selected from Al, Ti, V, Fe, Co or Zr, R is selected from F, Cl, Br or I, 0.1 < a < 3, 0.5 < b < 4, 3 < c < 5, 0 ≤ d ≤ 2; the chemical formula of the halide solid electrolyte is Li 3 MX 6 , where X is selected from Cl, Br or I, and M is selected from Y, In, Mg or Zr.

7. A method for preparing a diaphragm, It is characterized in that The steps include: The diaphragm coating slurry composition according to claim 1 or 2 is coated on at least one side of the base film, and then dried to obtain the diaphragm.

8. The method for preparing the diaphragm according to claim 7, It is characterized in that The steps include: An inorganic layer is formed on at least one surface of the base film, and then the diaphragm coating slurry composition according to claim 1 or 2 is coated on the inorganic layer, and then dried to obtain the diaphragm.

9. A lithium battery, It is characterized in that A separator comprising the separator according to any one of claims 4 to 6.

10. The lithium battery according to claim 9, It is characterized in that The lithium battery further includes a negative electrode, and the side of the separator having the coating layer is opposite to the negative electrode.

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