Paint for electrode coating, preparation method of electrode and lithium ion battery

Abstract

The invention provides a paint for an electrode coating, a preparation method of an electrode and a lithium ion battery. The coating for the electrode coating is prepared from the following components in parts by weight: 5 to 20 parts of inorganic nanoparticles, 20 to 80 parts of oligomer, 5 to 20 parts of organic micromolecular monomer, 0.01 to 5 parts of initiator and 5 to 20 parts of organic solvent, wherein the inorganic nanoparticles are selected from any one or more of metal oxides, phosphates containing metal elements, silicon-containing compounds and aluminum-containing minerals; the oligomer is an acrylate oligomer; the organic micromolecular monomer is an acrylate monomer; the organic solvent is a carbonic ester compound and / or a carboxylic ester compound. The electrode coating formed by the coating for the electrode coating can be compounded with a ceramic coating of a diaphragm to form an integral structure, the ceramic coating is firmly adhered to the surface of a pole piece, and the inorganic nanoparticles can improve the heat resistance of the electrode coating, so that the safety performance of a battery cell is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a coating for electrode coating, a method for preparing an electrode, and a lithium ion battery. Background Art

[0002] With the rapid development of electric vehicles and energy storage power stations, the demand for high-safety lithium batteries is increasing. Traditional lithium-ion batteries (LIBs) are difficult to meet the above needs due to the limitations of flammable organic electrolytes and polyolefin separators that are easily shrunk at high temperatures. Among them, the flammable organic electrolyte has a low flash point, is easy to leak, is easy to gasify and is easy to burn, which increases the safety risks of the battery during use. The thermal shrinkage and melting temperature of the polyolefin-based film in the ceramic coating are low (around 130°C), and the softening temperature of the adhesive is low (around 110°C), which causes the ceramic coating separator to shrink easily at high temperatures, break the film, and the ceramic layer is easy to break. The use of in-situ condensed electrolytes can form a condensed electrolyte after the monomer gel is polymerized, thereby forming a three-dimensional network structure to lock the organic electrolyte, making the electrolyte no longer fluid, avoiding problems such as leakage. At the same time, the three-dimensional network structure formed by the polymer in the condensed electrolyte bonds the ceramic coating of the diaphragm into an integral structure, so that the ceramic coating is firmly bonded to the surface of the electrode. The condensed electrolyte polymer has high temperature resistance, which avoids the thermal shrinkage of the polyolefin diaphragm and the breakage of the ceramic coating, thereby improving the safety performance of the battery.

[0003] Currently, the preparation process for in-situ condensed electrolytes involves adding the small organic monomer vinylene carbonate, a crosslinker, and an initiator to the electrolyte, injecting the electrolyte into the battery cell, and then heating the cell to trigger a gelation reaction of the organic monomers to form an in-situ condensed electrolyte. However, this method directly introduces multiple organic monomers into the battery, which presents the following problems:

[0004] 1) The concentration of the small molecule organic monomer vinylene carbonate in the electrolyte inside the battery cell is low, resulting in a low reaction rate.

[0005] 2) In the gelation reaction of the small-molecule organic monomer vinylene carbonate, the organic and inorganic components within the battery cell are mostly impurities, which lead to quenching of the initiator and active free radicals, termination of the reaction, or chain transfer, thereby further reducing the gelation reaction rate of the small-molecule organic monomer. At the same time, the residual small-molecule organic monomer and initiator both contain active functional groups, which are very likely to react in the battery, thereby increasing the occurrence of side reactions during battery use, causing problems such as gas production and active lithium consumption, thereby reducing the battery's electrical performance and even creating safety hazards.

[0006] 3) The small molecule organic monomer vinylene carbonate has a serious dissolving and softening effect on the adhesive in the positive and negative electrode coatings, which causes the internal structure of the positive and negative electrode slurry coatings to be destroyed, thereby increasing their internal resistance and decreasing their bonding strength, thereby reducing the electrochemical performance of the battery cell.

[0007] Therefore, there is an urgent need to develop an electrode coating that can better protect the electrode. Summary of the Invention

[0008] The main purpose of the present invention is to provide a coating for electrode coating, a method for preparing an electrode, and a lithium-ion battery, so as to solve the problems that when the existing in-situ condensed electrolyte is used, the organic small molecule monomers introduced into the battery dissolve the adhesive of the positive and negative electrode coatings, soften and destroy the positive and negative electrode coating structures, and the in-situ gelation reaction is incomplete, and the monomer residual rate is high, resulting in an increase in side reactions inside the battery cell.

[0009] To achieve the above-mentioned object, according to one aspect of the present invention, there is provided a coating for electrode coating, which comprises, in parts by weight: 5 to 20 parts of inorganic nanoparticles, 20 to 80 parts of oligomers, 5 to 20 parts of organic small molecule monomers, 0.01 to 5 parts of initiators, and 5 to 20 parts of organic solvents; wherein the inorganic nanoparticles are selected from any one or more of metal oxides, phosphates containing metal elements, silicon-containing compounds, and aluminum-containing minerals; the oligomers are acrylate oligomers; the organic small molecule monomers are acrylate monomers; and the organic solvent is a carbonate compound and / or a carboxylate compound.

[0010] Furthermore, the electrode coating material comprises, by weight, 8 to 17 parts of inorganic nanoparticles, 25 to 75 parts of oligomers, 5 to 15 parts of organic small molecule monomers, 0.01 to 3 parts of initiators, and 5 to 15 parts of organic solvents.

[0011] Furthermore, the mass ratio of the inorganic nanoparticles to the oligomers is 10-15:30-70, and / or the mass ratio of the oligomers to the organic small molecule monomers is 30-70:5-10.

[0012] Furthermore, the metal oxide is selected from any one or more of aluminum oxide, lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide and lithium lanthanum tantalum oxide; and / or the phosphate containing the metal element is lithium aluminum germanium phosphate and / or lithium aluminum titanium phosphate; and / or the silicon-containing compound is silicon dioxide; and / or the aluminum-containing mineral is boehmite.

[0013] Furthermore, the oligomer is selected from any one or more of polyurethane acrylate, polyester acrylate and polyester cyanoacrylate, and the molecular weight of the oligomer is 200 to 5000.

[0014] Furthermore, the organic small molecule monomer is selected from any one or more of ethoxyethyl acrylate, ethoxyethyl methacrylate and ethoxylated phenoxy acrylate; and / or the initiator is selected from any one or more of phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, benzophenone, thioxanthone, ethyl 4-(N,N-dimethylamino)benzoate, octyl 4-(N,N-dimethylamino)benzoate, 2-hydroxy-2-methyl-1-phenyl-1-propanone and 1-hydroxy-cyclohexyl-phenyl ketone.

[0015] Furthermore, the carbonate compound is selected from any one or more of dimethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate and diethyl carbonate; and / or the carboxylate compound is methyl propionate and / or ethyl acetate; and / or the solid content of the electrode coating is 70-90%.

[0016] According to another aspect of the present invention, a method for preparing an electrode is provided, which comprises: step S1, mixing raw materials corresponding to the above-mentioned electrode coating paint to obtain a slurry; and step S2, coating the slurry on the surface of the electrode, and then curing and drying the slurry in sequence to obtain an electrode having an electrode coating on the surface.

[0017] Furthermore, in the above step S1, stirring is performed during the mixing process, the stirring speed is 100 to 500 rpm, and / or the stirring time is 30 to 120 min; and / or, in the above step S2, the coating method is inkjet printing and / or air gun spraying; and / or, ultraviolet light is used for curing, and the curing time is 0.5 to 5 min; and / or, the drying temperature is 60 to 100° C., and the drying time is 1 to 5 min.

[0018] According to another aspect of the present invention, a lithium-ion battery is provided, comprising an electrode, a separator and an electrolyte, wherein the electrode is prepared by the above-mentioned preparation method.

[0019] Compared to the in-situ condensed electrolyte solution, the present invention preferably controls the composition and content of the electrode coating within the above ranges. In particular, the content of oligomers and small organic molecule monomers in the coating is increased, which can increase the reaction rate of oligomers and small organic molecule monomers, thereby reducing their residual amount and, in turn, the degree of their side reactions within the battery. Simultaneously, oligomers and organic solvents can replace most of the small molecule organic monomers, effectively reducing the dissolution and softening of the adhesive in the positive and negative electrode active coatings, as well as the degree of damage to the internal structure of the positive and negative electrode active coatings caused by the small molecule monomers. Introducing the aforementioned inorganic nanoparticles into the electrode coating can increase the softening temperature of the electrode coating (approximately 250°C), thereby increasing the thermal shrinkage temperature and reducing the thermal shrinkage rate of the electrode coating. Furthermore, the introduction of inorganic nanoparticles can reduce the crystallinity of the electrode coating, increase its free volume, and thus improve the ionic conductivity of the electrode coating. The use of an initiator can induce polymerization of the electrode coating under ultraviolet irradiation conditions, thereby better forming the electrode coating on the electrode surface. In addition, the electrode coating formed by the electrode coating of the present application can be composited with the ceramic coating of the diaphragm into an integral structure, and the ceramic coating is firmly bonded to the surface of the electrode piece. At the same time, the introduction of inorganic nanoparticles further improves the heat resistance of the electrode coating, so that the diaphragm ceramic coating is not easy to break and pulverize at high temperatures of the battery cell, thereby improving the safety performance of the battery cell. The use of the above-mentioned types of small molecule organic monomers can reduce the cross-linking density of the three-dimensional skeleton of the oligomer, thereby increasing the liquid absorption rate and ionic conductivity of the oligomer. In addition, the electrode coating and the electrolyte fuse with each other to form a gel state, which can lock the liquid organic electrolyte inside the battery cell, increase the flash point and vaporization temperature of the organic electrolyte, and thus reduce the risk of leakage and combustion of the organic electrolyte. DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0021] As analyzed in the background technology of this application, when in-situ condensed state electrolytes are used in the prior art, the organic small molecule monomers introduced inside the battery have the problem of dissolving the adhesives of the positive and negative electrode coatings, softening and destroying the positive and negative electrode coating structures, as well as incomplete in-situ gelation reactions and a high monomer residual rate leading to an increase in side reactions inside the battery cell. In order to solve the above problems, the present application provides a coating for electrode coating, a method for preparing an electrode, and a lithium-ion battery.

[0022] In a typical embodiment of the present application, a coating for electrode coating is provided, which comprises, in parts by weight: 5 to 20 parts of inorganic nanoparticles, 20 to 80 parts of oligomers, 5 to 20 parts of organic small molecule monomers, 0.01 to 5 parts of initiators, and 5 to 20 parts of organic solvents; wherein the inorganic nanoparticles are selected from any one or more of metal oxides, phosphates containing metal elements, silicon-containing compounds, and aluminum-containing minerals; the oligomers are acrylate oligomers; the organic small molecule monomers are acrylate monomers; and the organic solvent is a carbonate compound and / or a carboxylate compound.

[0023] Compared with the technical solution of in-situ condensed electrolyte, the present application preferably controls the composition and content of the electrode coating within the above range, especially increases the content of oligomers and organic small molecule monomers in the coating, which can increase the reaction rate of oligomers and organic small molecule monomers, thereby reducing the residual amount of the two, and thus reducing the degree of their side reactions inside the battery. At the same time, oligomers and organic solvents can replace most of the small molecule organic monomers, which can effectively reduce the dissolution and softening of the adhesive in the positive and negative electrode active coatings by the small molecule monomers, as well as the degree of damage to the internal structure of the positive and negative electrode active coatings. Introducing the above-mentioned types of inorganic nanoparticles into the electrode coating coating can increase the softening temperature of the electrode coating (about 250°C), thereby increasing the thermal shrinkage temperature of the electrode coating and reducing the thermal shrinkage rate. At the same time, the introduction of inorganic nanoparticles can reduce the crystallinity of the electrode coating, increase its free volume, and thus improve the ionic conductivity of the electrode coating. The use of an initiator can induce the polymerization of the electrode coating coating under ultraviolet irradiation conditions, thereby better forming an electrode coating on the electrode surface. In addition, the electrode coating formed by the electrode coating of the present application can be composited with the ceramic coating of the diaphragm into an integral structure, and the ceramic coating is firmly bonded to the surface of the electrode piece. At the same time, the introduction of inorganic nanoparticles further improves the heat resistance of the electrode coating, so that the diaphragm ceramic coating is not easy to break and pulverize at high temperatures of the battery cell, thereby improving the safety performance of the battery cell. The use of the above-mentioned types of small molecule organic monomers can reduce the cross-linking density of the three-dimensional skeleton of the oligomer, thereby increasing the liquid absorption rate and ionic conductivity of the oligomer. In addition, the electrode coating and the electrolyte fuse with each other to form a gel state, which can lock the liquid organic electrolyte inside the battery cell, increase the flash point and vaporization temperature of the organic electrolyte, and thus reduce the risk of leakage and combustion of the organic electrolyte.

[0024] In addition, the weight proportion of the inorganic nanoparticles can be 5 parts, 8 parts, 12 parts, 15 parts, 17 parts or 20 parts. Of course, the weight proportion of the inorganic nanoparticles can be any value between 5 and 20 parts, which will not be described in detail here.

[0025] The weight proportion of the oligomer can be 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts or 80 parts. Of course, the weight proportion of the oligomer can be any point value between 20 and 80 parts, which will not be repeated here.

[0026] The weight proportion of the organic small molecule monomer can be 5 parts, 7 parts, 13 parts, 15 parts, 18 parts or 20 parts. Of course, the weight proportion of the organic small molecule monomer can be any value between 5 and 20 parts, which will not be described in detail here.

[0027] The weight proportion of the organic small molecule monomer can be 5 parts, 7 parts, 13 parts, 15 parts, 18 parts or 20 parts. Of course, the weight proportion of the organic small molecule monomer can be any value between 5 and 20 parts, which will not be described in detail here.

[0028] The weight fraction of the initiator can be 0.01 parts, 0.5 parts, 1 parts, 2 parts, 3 parts, 4 parts, or 5 parts. Of course, the weight fraction of the organic small molecule monomer can be any point value from 0.01 to 5 parts, which will not be repeated here.

[0029] The weight proportion of the organic solvent may be 5 parts, 8 parts, 13 parts, 15 parts, 17 parts or 20 parts. Of course, the weight proportion of the organic solvent may be any value between 5 and 20 parts, which will not be described in detail here.

[0030] In order to further improve the heat resistance of the electrode coating and the protective effect on the electrode, in one embodiment of the present application, the above-mentioned electrode coating includes, by weight: 8 to 17 parts of inorganic nanoparticles, 25 to 75 parts of oligomers, 5 to 15 parts of organic small molecule monomers, 0.01 to 3 parts of initiator and 5 to 15 parts of organic solvent.

[0031] In one embodiment of the present application, the mass ratio of the inorganic nanoparticles to the oligomers is 10-15:30-70, and / or the mass ratio of the oligomers to the organic small molecule monomers is 30-70:5-10.

[0032] The preferred control of the mass ratio of inorganic nanoparticles to oligomers within the above range helps to increase the softening temperature of the electrode coating (around 250°C), thereby increasing the thermal shrinkage temperature and reducing the thermal shrinkage rate of the electrode coating. Simultaneously, the introduction of inorganic nanoparticles helps to reduce the crystallinity of the electrode coating, increasing its free volume, and thus improving the ionic conductivity of the electrode coating. The preferred control of the mass ratio of oligomers to organic small molecule monomers within the above range can reduce the crosslinking density of the oligomer three-dimensional skeleton, thereby improving the coating's electrolyte absorption rate and ionic conductivity.

[0033] In one embodiment of the present application, the metal oxide is selected from any one or more of aluminum oxide, lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide and lithium lanthanum tantalum oxide; and / or, the phosphate containing the metal element is lithium aluminum germanium phosphate and / or lithium aluminum titanium phosphate; and / or, the silicon-containing compound is silicon dioxide; and / or, the aluminum-containing mineral is boehmite.

[0034] The type of metal oxide is preferably within the above range. The metal oxide has high ionic conductivity, which helps to improve the ionic conductivity of the coating while enhancing its thermal stability and strength. The phosphate containing the metal element is preferably within the above range. The phosphate has good thermal stability and strength, and also has high ionic conductivity, which helps to promote the rapid transmission of lithium ions, while maintaining the stability of the electrolyte interface, reducing the side reactions of the battery during the charge and discharge process, thereby improving the cycle performance and safety of the battery. The silicon-containing compound of the above type has high porosity and good thermal stability, which helps to increase the porosity of the coating, thereby improving its liquid absorption rate and ionic conductivity. At the same time, the high chemical stability and electrical insulation of the silicon-containing compound help to protect the battery from corrosion, thereby reducing the risk of internal short circuits. The aluminum-containing mineral of the above type has good chemical stability and high ionic conductivity, which helps to improve the interface characteristics between the electrode and the electrolyte, thereby improving the strength and thermal stability of the coating, while providing additional fire resistance, thereby enhancing the safety of the battery as a whole.

[0035] Preferably, the inorganic nanoparticles are a combination of lithium aluminum titanium phosphate and aluminum oxide, with a mass ratio of lithium aluminum titanium phosphate to aluminum oxide of 80-90:20-10, which helps to improve the thermal stability of the coating while reducing the coating impedance, thereby increasing the thermal shrinkage temperature of the electrode coating and reducing the thermal shrinkage rate.

[0036] In one embodiment of the present application, the oligomer is selected from any one or more of polyurethane acrylate, polyester acrylate and polyester cyanoacrylate; and / or the molecular weight of the oligomer is 200 to 5000.

[0037] The type and molecular weight of the oligomer are preferably within the above range, which helps to reduce the dissolution and softening of the adhesive of the positive and negative electrode slurry coating by the organic small molecule monomer, reduce the damage to the positive and negative electrode coating structure, thereby reducing the internal resistance of the battery cell and improving the cycle stability of the battery cell.

[0038] In one embodiment of the present application, the organic small molecule monomer is selected from any one or more of ethoxyethyl acrylate, ethoxyethyl methacrylate and ethoxylated phenoxy acrylate; and / or the initiator is selected from any one or more of phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, benzophenone, thioxanthone, ethyl 4-(N,N-dimethylamino)benzoate, octyl 4-(N,N-dimethylamino)benzoate, 2-hydroxy-2-methyl-1-phenyl-1-propanone and 1-hydroxy-cyclohexyl-phenyl ketone.

[0039] The above-mentioned small molecule organic monomers are preferably helpful in improving the flexibility and chemical stability of the electrode coating, thereby facilitating the bonding between the coating and the electrode.

[0040] The preferred organic small molecule monomer is a combination of ethoxyethyl methacrylate and ethoxylated phenoxy acrylate, and the mass ratio of ethoxyethyl methacrylate to ethoxylated phenoxy acrylate is 70-80:30-20, which helps to better reduce the crosslinking density of the three-dimensional skeleton of the oligomer, thereby improving the liquid absorption rate and ionic conductivity of the coating.

[0041] The above-mentioned initiators are preferred because they help to better initiate the polymerization of the coating material for the electrode coating, thereby better forming the electrode coating on the electrode surface.

[0042] In one embodiment of the present application, the carbonate solvent is selected from any one or more of dimethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate and diethyl carbonate; and / or the carboxylate solvent is methyl propionate and / or ethyl acetate; and / or the solid content of the coating for electrode coating is 70-90%.

[0043] The type of organic solvent is preferably within the above range, which helps to evenly disperse inorganic nanoparticles, oligomers and organic small molecule monomers in the organic solvent, thereby improving the uniformity and porosity of the coating. It also helps to adjust the solid content of the electrode coating paint within the above range, so that it has good fluidity and coating uniformity.

[0044] In another typical embodiment of the present application, a method for preparing an electrode is provided, which includes: step S1, mixing the raw materials corresponding to the above-mentioned electrode coating paint to obtain a slurry; and step S2, coating the slurry on the surface of the electrode, and then curing and drying it in sequence to obtain an electrode with an electrode coating on the surface.

[0045] The present application forms an electrode coating on the surface of the electrode (positive electrode sheet and / or negative electrode sheet) by coating the above-mentioned slurry on the surface of the electrode (positive electrode sheet and / or negative electrode sheet) through curing and drying, which can be combined with the ceramic coating of the diaphragm into an integral structure, and the ceramic coating is firmly bonded to the surface of the electrode sheet. At the same time, the introduction of inorganic nanoparticles further improves the heat resistance of the electrode coating, thereby making the diaphragm ceramic coating less likely to break and pulverize at high temperatures of the battery cell, thereby improving the safety performance of the battery cell. In addition, the electrode coating and the electrolyte fuse with each other to form a gel state, which can lock the liquid organic electrolyte inside the battery cell, increase the flash point and vaporization temperature of the organic electrolyte, and thus reduce the risk of leakage and combustion of the organic electrolyte.

[0046] In one embodiment of the present application, in the above-mentioned step S1, stirring is performed during the mixing process, and the stirring speed is 100-500 rpm, and / or the stirring time is 30-120 min; and / or, in the above-mentioned step S2, the coating method is inkjet printing and / or air gun spraying; and / or, ultraviolet light is used for curing, and the curing time is 0.5-5 min; and / or, the drying temperature is 60-100°C, and the drying time is 1-5 min.

[0047] Preferably, the stirring speed and time are controlled within the above ranges to improve the uniformity of the slurry, thereby facilitating subsequent coating and curing. Preferably, the above coating method is employed, with curing by ultraviolet light irradiation and the curing time controlled within the above range to better initiate polymerization and quickly and efficiently form a uniform, dense, high-strength, and thermally stable electrode coating on the electrode surface.

[0048] In another typical embodiment of the present application, a lithium-ion battery is provided, comprising an electrode, a separator and an electrolyte, wherein the electrode is prepared by the above-mentioned preparation method.

[0049] Lithium-ion batteries containing these electrodes not only have high energy density and long cycle life, but also have excellent safety and environmental adaptability. The electrodes include a positive electrode sheet and a negative electrode sheet. The surface of the positive electrode sheet and / or the negative electrode sheet contains an electrode coating.

[0050] The beneficial effects of the present application will be further illustrated below with reference to examples.

[0051] Example 1

[0052] The raw materials of the electrode coating coating include, by weight, 20 parts of inorganic nanoparticle lithium aluminum titanium phosphate, 60 parts of oligomer polyurethane acrylate, 20 parts of organic small molecule monomer ethoxyethyl acrylate, 5 parts of initiator benzophenone, and 5 parts of organic solvent dimethyl carbonate; among which the molecular weight of the oligomer polyurethane acrylate is 500.

[0053] The raw materials were mixed at 100 rpm for 30 minutes to obtain a slurry with a solid content of 80%. The slurry was then applied to the surfaces of the positive and negative electrodes by inkjet printing, cured under ultraviolet light for 0.5 minutes, and dried at 60°C for 5 minutes to obtain coated positive and negative electrodes.

[0054] The lithium-ion battery is obtained by alternately laminating a positive electrode sheet with a coating on its surface, a negative electrode sheet with a coating on its surface, and a separator to form an electrode assembly, which is then housed in a battery casing. The electrolyte is ethylene carbonate and lithium hexafluorophosphate, and the separator is a polyolefin separator with a ceramic coating on its surface.

[0055] Example 2

[0056] Calculated by weight, the raw materials of the electrode coating include: 5 parts of inorganic nanoparticle lithium aluminum titanium phosphate, 80 parts of oligomer polyurethane acrylate, 7 parts of organic small molecule monomer ethoxyethyl acrylate, 1 part of initiator benzophenone, and 10 parts of organic solvent dimethyl carbonate; among which the molecular weight of the oligomer polyurethane acrylate is 3000.

[0057] The raw materials were mixed at 300 rpm for 75 minutes to obtain a slurry with a solid content of 90%. The slurry was then applied to the surfaces of the positive and negative electrodes by inkjet printing, cured under ultraviolet light for 3.5 minutes, and dried at 80°C for 3 minutes to obtain coated positive and negative electrodes.

[0058] A lithium-ion battery is obtained by alternately laminating coated positive electrode sheets, coated negative electrode sheets, and a separator to form an electrode assembly, which is then housed in a battery casing. The electrolyte is ethylene carbonate and lithium hexafluorophosphate, and the separator is a polyolefin separator with a ceramic coating.

[0059] Example 3

[0060] The raw materials of the electrode coating coating include, by weight, 5 parts of inorganic nanoparticle lithium aluminum titanium phosphate, 20 parts of oligomer polyurethane acrylate, 5 parts of organic monomer ethoxyethyl acrylate, 0.01 parts of initiator benzophenone, and 20 parts of organic solvent dimethyl carbonate; wherein the molecular weight of the oligomer polyurethane acrylate is 5000.

[0061] The raw materials were mixed at 500 rpm for 120 minutes to obtain a slurry with a solid content of 70%. The slurry was then applied to the surfaces of the positive and negative electrode sheets using inkjet printing, cured under ultraviolet light for 5 minutes, and dried at 100°C for 1 minute to obtain coated positive and negative electrode sheets.

[0062] The lithium-ion battery is obtained by alternately laminating a positive electrode sheet with a coating on its surface, a negative electrode sheet with a coating on its surface, and a separator to form an electrode assembly, which is then housed in a battery casing. The electrolyte is ethylene carbonate and lithium hexafluorophosphate, and the separator is a polyolefin separator with a ceramic coating on its surface.

[0063] Example 4

[0064] The difference from Example 1 is that the total weight of the inorganic nanoparticles aluminum titanium phosphate and the oligomer polyurethane acrylate is 80 parts, and the mass ratio of the inorganic nanoparticles to the polymer oligomer is 10:70. Finally, a positive electrode sheet with a coating on the surface, a negative electrode sheet with a coating on the surface, and a lithium-ion battery are obtained.

[0065] Example 5

[0066] The difference from Example 1 is that the total weight of the inorganic nanoparticles aluminum titanium phosphate and the oligomer polyurethane acrylate is 80 parts, and the mass ratio of the inorganic nanoparticles to the polymer oligomer is 5:75. Finally, a positive electrode sheet with a coating on the surface, a negative electrode sheet with a coating on the surface, and a lithium-ion battery are obtained.

[0067] Example 6

[0068] The difference from Example 1 is that the total weight of the oligomer polyurethane acrylate and the organic small molecule monomer ethoxyethyl acrylate is 80 parts, and the mass ratio of the oligomer to the organic small molecule monomer is 70:10. Finally, a positive electrode sheet with a coating on the surface, a negative electrode sheet with a coating on the surface, and a lithium-ion battery are obtained.

[0069] Example 7

[0070] The difference from Example 1 is that the total weight of the oligomer polyurethane acrylate and the organic small molecule monomer ethoxyethyl acrylate is 80 parts, and the mass ratio of the oligomer to the organic small molecule monomer is 65:15. Finally, a positive electrode sheet with a coating on the surface, a negative electrode sheet with a coating on the surface, and a lithium-ion battery are obtained.

[0071] Example 8

[0072] The difference from Example 1 is that the inorganic particles are a combination of lithium aluminum titanium phosphate and aluminum oxide, and the mass ratio of lithium aluminum titanium phosphate and aluminum oxide is 80:20. Finally, a positive electrode sheet with a coating on the surface, a negative electrode sheet with a coating on the surface and a lithium-ion battery are obtained.

[0073] Example 9

[0074] The difference from Example 1 is that the inorganic particles are a combination of lithium aluminum titanium phosphate and aluminum oxide, and the mass ratio of lithium aluminum titanium phosphate and aluminum oxide is 1:1. Finally, a positive electrode sheet with a coating on the surface, a negative electrode sheet with a coating on the surface and a lithium-ion battery are obtained.

[0075] Example 10

[0076] The difference from Example 1 is that the organic small molecule monomer is a combination of ethoxyethyl methacrylate and ethoxylated phenoxy acrylate, and the mass ratio of ethoxyethyl methacrylate to ethoxylated phenoxy acrylate is 70:30. Finally, a positive electrode sheet with a coating on the surface, a negative electrode sheet with a coating on the surface, and a lithium-ion battery are obtained.

[0077] Example 11

[0078] The difference from Example 1 is that the organic small molecule monomer is a combination of ethoxyethyl methacrylate and ethoxylated phenoxy acrylate, and the mass ratio of ethoxyethyl methacrylate to ethoxylated phenoxy acrylate is 1:1. Finally, a positive electrode sheet with a coating on the surface, a negative electrode sheet with a coating on the surface, and a lithium-ion battery are obtained.

[0079] Comparative Example 1

[0080] The difference from Example 1 is that inorganic nanoparticles of lithium aluminum titanium phosphate are not added, and finally a positive electrode sheet with a coating on the surface, a negative electrode sheet with a coating on the surface and a lithium ion battery are obtained.

[0081] Comparative Example 2

[0082] The difference from Example 1 is that oligomer polyurethane acrylate is not added, and finally a positive electrode sheet with a coating on the surface, a negative electrode sheet with a coating on the surface, and a lithium-ion battery are obtained.

[0083] Comparative Example 3

[0084] The difference from Example 1 is that, in parts by weight, the raw materials for the electrode coating coating include: 20 parts of inorganic nanoparticle lithium aluminum titanium phosphate, 20 parts of oligomer polyurethane acrylate, 60 parts of organic small molecule monomer ethoxyethyl acrylate, 5 parts of initiator benzophenone, and 5 parts of organic solvent dimethyl carbonate, and finally a positive electrode sheet with a coating on the surface, a negative electrode sheet with a coating on the surface, and a lithium-ion battery are obtained.

[0085] Test method:

[0086] Negative electrode coating adhesion test method:

[0087] ①Cut the electrode to a width of 25mm and a length of 400mm;

[0088] ② Stick a certain width of transparent tape horizontally on the bottom of the non-scaled steel ruler flush with the end surface;

[0089] ③ Then stick the double-sided tape on the transparent tape, with the length being the same as the width of the transparent tape and the position centered. Finally, stick the test sample on the double-sided tape with the end faces flush, and use the pressure wheel to roll back and forth on the surface of the electrode for more than 3 times;

[0090] ④ Fold the unbonded end of the electrode of the experimental sample 180°, clamp it on the upper clamp of the tensile testing machine, and peel the electrode at a speed of 15mm / min. When the electrode collector and the coating are completely separated, read the peel strength test results and use the average value of the stable section as the bonding strength value.

[0091] Monomer reaction rate test method:

[0092] ① Take the coating material and weigh its mass using a balance, recorded as m0;

[0093] ② Soak the weighed coating in a tetrahydrofuran solvent that is 20 times thicker than the original. After soaking for 48 hours, use a solid content meter to test the coating mass after soaking, which is m1. The monomer reaction rate is calculated as: C = m1 / m0*100%.

[0094] Coating liquid absorption test method:

[0095] ① Take the coating material and weigh its mass using a balance, recorded as m0;

[0096] ② Immerse the weighed coating in a solution 20 times larger than the original (the volume ratio of dimethyl carbonate, ethyl methyl carbonate and ethyl carbonate is 40:30:30). After soaking for 48 hours, filter with 40um filter paper, and then weigh the solid mass after filtration and record it as m1. The coating liquid absorption rate is calculated as follows: γ = (m1-m0) / m0*100%.

[0097] Battery cell DC internal resistance (DCIR) test method:

[0098] (1) 25±2℃, battery capacity calibration, the test process is as follows:

[0099] ① Place the battery in a constant temperature box at 25±2℃ and let it stand for 30 minutes;

[0100] ②Discharge the battery to 2.75V with a current of 0.33C;

[0101] ③ Let the battery sit for 5 minutes;

[0102] ④ Charge the battery to 4.25V with a constant current and constant voltage of 0.33C;

[0103] ⑤ Repeat steps ① to ④, and use the capacity of the second discharge as the actual capacity of the battery.

[0104] (2) Battery charging DCIR test method:

[0105] ①Discharge the battery to 2.75V with a current of 0.33C;

[0106] ② Charge the battery to 50% SOC with a current of 0.33C;

[0107] ③ Let the battery rest for 30 minutes and record the voltage V0 at this time as the OCV at the corresponding SOC;

[0108] ④ Charge with a charging current of I2 = 2C for t = 10s, and record the voltage V1 at the ts point;

[0109] ⑤Calculation formula for charging DC internal resistance: DCIR 充 =(V1-V0) / I2

[0110] Battery cell initial efficiency test method:

[0111] 1. The test temperature is 45±3℃ and the restraining force is 0.5MPa.

[0112] 2. Install the battery cell into the fixture of the formation equipment, ensure that the positive and negative poles are in correct contact with the terminals of the charger and discharger, and check whether the battery cell voltage is abnormal. If there is no abnormality, start the test.

[0113] 3. The test steps are as follows:

[0114] ① Set aside for 30 minutes;

[0115] ② Constant current charging, charging current is 0.02C, cut-off voltage is 2.5V;

[0116] ③ Constant current charging, charging current is 0.05C, cut-off voltage is 3V;

[0117] ④ Constant current charging, charging current is 0.33C, cut-off voltage is 4.25V;

[0118] ⑤ Constant voltage charging, voltage is 4.25V, cut-off current is 0.05C;

[0119] ⑥ Set aside for 30 minutes;

[0120] ⑦ Constant current discharge, discharge current is 0.33C, cut-off voltage is 2.5V.

[0121] 4. The calculation formula for the first efficiency is: battery cell first efficiency = battery cell discharge capacity / battery cell charging capacity * 100%

[0122] The above test results are shown in Table 1.

[0123] Table 1

[0124]

[0125]

[0126] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0127] Compared with the technical solution of in-situ condensed electrolyte, the present application preferably controls the composition and content of the electrode coating within the above range, especially increases the content of oligomers and organic small molecule monomers in the coating, which can increase the reaction rate of oligomers and organic small molecule monomers, thereby reducing the residual amount of the two, and thus reducing the degree of their side reactions inside the battery. At the same time, oligomers and organic solvents can replace most of the small molecule organic monomers, which can effectively reduce the dissolution and softening of the adhesive in the positive and negative electrode active coatings by the small molecule monomers, as well as the degree of damage to the internal structure of the positive and negative electrode active coatings. Introducing the above-mentioned types of inorganic nanoparticles into the electrode coating coating can increase the softening temperature of the electrode coating (about 250°C), thereby increasing the thermal shrinkage temperature of the electrode coating and reducing the thermal shrinkage rate. At the same time, the introduction of inorganic nanoparticles can reduce the crystallinity of the electrode coating, increase its free volume, and thus improve the ionic conductivity of the electrode coating. The use of an initiator can induce the polymerization of the electrode coating coating under ultraviolet irradiation conditions, thereby better forming an electrode coating on the electrode surface. In addition, the electrode coating formed by the electrode coating of the present application can be composited with the ceramic coating of the diaphragm into an integral structure, and the ceramic coating is firmly bonded to the surface of the electrode piece. At the same time, the introduction of inorganic nanoparticles further improves the heat resistance of the electrode coating, so that the diaphragm ceramic coating is not easy to break and pulverize at high temperatures of the battery cell, thereby improving the safety performance of the battery cell. The use of the above-mentioned types of small molecule organic monomers can reduce the cross-linking density of the three-dimensional skeleton of the oligomer, thereby increasing the liquid absorption rate and ionic conductivity of the oligomer. In addition, the electrode coating and the electrolyte fuse with each other to form a gel state, which can lock the liquid organic electrolyte inside the battery cell, increase the flash point and vaporization temperature of the organic electrolyte, and thus reduce the risk of leakage and combustion of the organic electrolyte.

[0128] The above are merely embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A coating material for electrode coating, characterized in that: In parts by weight, the electrode coating material comprises: 5 to 20 parts of inorganic nanoparticles; 20-80 parts of oligomers; 5 to 20 parts of organic small molecule monomer; 0.01 to 5 parts of an initiator; and 5-20 parts of organic solvent; Wherein, the inorganic nanoparticles are selected from any one or more of metal oxides, phosphates containing metal elements, silicon-containing compounds and aluminum-containing minerals; The oligomer is an acrylate oligomer; The organic small molecule monomer is an acrylate monomer; The organic solvent is a carbonate compound and / or a carboxylate compound.

2. The electrode coating paint according to claim 1, characterized in that In parts by weight, the electrode coating material comprises: 8 to 17 parts of the inorganic nanoparticles; 25 to 75 parts of the oligomer; 5 to 15 parts of the organic small molecule monomer; 0.01 to 3 parts of the initiator; and 5 to 15 parts of the organic solvent.

3. The electrode coating paint according to claim 1 or 2, characterized in that: The mass ratio of the inorganic nanoparticles to the oligomer is 10-15:30-70, and / or the mass ratio of the oligomer to the organic small molecule monomer is 30-70:5-10.

4. The electrode coating paint according to any one of claims 1 to 3, characterized in that The metal oxide is selected from any one or more of aluminum oxide, lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide and lithium lanthanum tantalum oxide; and / or the phosphate containing the metal element is lithium aluminum germanium phosphate and / or lithium aluminum titanium phosphate; and / or the silicon-containing compound is silicon dioxide; and / or the aluminum-containing mineral is boehmite.

5. The electrode coating paint according to any one of claims 1 to 4, characterized in that The oligomer is selected from any one or more of polyurethane acrylate, polyester acrylate and polyester cyanoacrylate, and the molecular weight of the oligomer is 200 to 5000.

6. The electrode coating paint according to any one of claims 1 to 5, characterized in that The organic small molecule monomer is selected from any one or more of ethoxyethyl acrylate, ethoxyethyl methacrylate and ethoxylated phenoxy acrylate; and / or the initiator is selected from any one or more of phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, benzophenone, thioxanthone, ethyl 4-(N,N-dimethylamino)benzoate, octyl 4-(N,N-dimethylamino)benzoate, 2-hydroxy-2-methyl-1-phenyl-1-propanone and 1-hydroxy-cyclohexyl-phenyl ketone.

7. The electrode coating paint according to any one of claims 1 to 6, characterized in that The carbonate compound is selected from any one or more of dimethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate and diethyl carbonate; and / or the carboxylate compound is methyl propionate and / or ethyl acetate; and / or the solid content of the electrode coating is 70-90%.

8. A method for preparing an electrode, characterized in that: The preparation method comprises: Step S1, mixing raw materials corresponding to the electrode coating material according to any one of claims 1 to 7 to obtain a slurry; and Step S2: After coating the slurry on the surface of the electrode, curing and drying are performed in sequence to obtain an electrode with an electrode coating on the surface.

9. The preparation method according to claim 8, characterized in that In the step S1, stirring is performed during the mixing process, the stirring speed is 100 to 500 rpm, and / or the stirring time is 30 to 120 minutes; And / or, in step S2, the coating method is inkjet printing and / or air gun spraying; and / or, using ultraviolet light for curing, wherein the curing time is 0.5 to 5 minutes; And / or, the drying temperature is 60-100° C., and the drying time is 1-5 minutes.

10. A lithium ion battery comprising an electrode, a separator and an electrolyte, characterized in that: The electrode is prepared by the preparation method according to claim 8 or 9.

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