CN114122578A - Power battery - Google Patents

Abstract

The invention provides a power battery which comprises a shell and a battery core arranged in the shell, wherein the inner surface and/or the outer surface of the shell is/are coated with a polyimide coating. The inner surface and/or the outer surface of the shell of the power battery provided by the application are/is coated with the polyimide coating, the coating is uniform in thickness, and the appearance is attractive; the insulating material has excellent insulating property, the withstand voltage reaches 20kV, the insulating resistance DC 1kV and 5s are more than 15G omega, and the leakage current DC 2.7kV and 60s are less than 0.2 muA; the high-temperature-resistant material has excellent high-temperature-resistant performance, and can resist temperature for more than 1h at 350 ℃; the heat dissipation performance is good, and the heat conductivity coefficient is larger than 0.2W/m.K; the adhesive force with the shell is excellent and reaches 100/100 level; the hardness is high and reaches the 2H level.

Description

Power battery

Technical Field

The invention relates to the technical field of batteries, in particular to a power battery.

Background

With the development of human civilization, the energy problem is increasingly prominent. As a convenient vehicle for people to go out, automobiles are rapidly developing from traditional fuel automobiles to new energy automobiles. The various countries and regions of the world also release political directives on the foreseeable future of the gradual cancellation of the use of fuel vehicles. In view of this, power batteries have also been rapidly developed as important parts of new energy vehicles. However, strict safety standards require that the power battery be insulated and protected correspondingly inside and outside the power battery.

For the interior of the power battery, the exterior of the battery core is usually wrapped with a plastic insulating film for insulating protection between the battery core and the metal shell. The plastic insulating film often used in the market is a pure PP film with a thickness of up to 100 μm. Power battery manufacturers generally punch holes in the plastic insulating film, so that electrolyte can be conveniently permeated through the micropores to achieve balance, and the electrolyte injection efficiency of the electrolyte is improved.

For the exterior of the power battery, the metal casing is usually wrapped with a pressure-sensitive insulating tape for insulating protection between the power battery and the exterior. The thickness of the pressure-sensitive insulating adhesive tape frequently used in the market is about 100-300 μm. In order to make the pressure-sensitive insulating tape have good adhesion and insulation properties to a metal shell, the pressure-sensitive insulating tape has a complex structure, usually consists of a multi-layer structure of a release layer/a PET film layer/an acrylic acid glue layer, needs to be prepared through technological processes of multi-step coating, drying, rolling, rewinding and the like, and has a complex process; in addition, the adhesive tape is attached and wrapped, and particularly, corners and deformed portions of the housing are not favorable for adhering the adhesive tape, which may reduce yield.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a power battery, wherein the inner surface and/or the outer surface of the shell of the power battery is coated with a polyimide coating, so that the shell has good insulating property and high temperature resistance, and finally, the inside and/or the outside of the power battery has good insulating temperature-resistant protection.

In view of the above, the present application provides a power battery, which includes a casing and a battery cell disposed inside the casing, wherein an inner surface and/or an outer surface of the casing is coated with a polyimide coating.

Preferably, the shell is an aluminum alloy shell.

Preferably, the thickness of the polyimide coating is 1-60 μm.

Preferably, the inner surface of the shell is coated with a polyimide coating, and the surface of the battery core is not coated with a plastic insulating film.

Preferably, the outer surface of the case is coated with a polyimide coating, and the outer surface of the case is not wrapped with a pressure sensitive insulating tape.

Preferably, the inner surface and the outer surface of the shell are both coated with polyimide coatings, the surface of the battery core is not coated with a plastic insulating film, and the outer surface of the shell is not coated with a pressure-sensitive insulating tape.

Preferably, the polyimide coating is obtained by electrophoretic deposition of an electrophoretic solution of polyimide and drying to form a film.

Preferably, the electrophoretic fluid of the polyimide comprises polyimide, an alkaline compound, a heat-conducting filler, alcohol or ketone, a water-soluble polar solvent and deionized water.

Preferably, the electrophoresis solution of the polyimide is weakly alkaline, and the neutralization rate of the alkaline compound is 50-200% based on the theoretical amount of the anionic group of the polyimide.

Preferably, based on the electrophoresis solution of the polyimide, the content of the polyimide is 1 to 15 wt%, the content of the alcohol or ketone is 10 to 50 wt%, the content of the water-soluble polar solvent is 20 to 60 wt%, the content of the heat-conducting filler is 0.1 to 50 wt%, and the content of the deionized water is 10 to 40 wt%.

Preferably, the polyimide is obtained by reacting a tetracarboxylic dianhydride compound and a diamine compound according to a molar ratio of 1 (0.95-1.05), and the weight average molecular weight of the polyimide is 20000-150000;

the tetracarboxylic dianhydride compound is one or more of a tetracarboxylic dianhydride compound containing acetylene groups and an aromatic tetracarboxylic dianhydride compound, and is specifically selected from 4,4 '- (acetylene-1, 2-diyl) diphthalic anhydride, pyromellitic dianhydride, 3', 4,4 '-biphenyltetracarboxylic dianhydride, bis (3, 4-dicarboxyphenyl) ether dianhydride, 3', 4,4 '-benzophenone tetracarboxylic dianhydride, bicyclo [2,2,2] oct-7-ene-2, 3,5, 6-tetracarboxylic dianhydride, 2, 2' -bis (3, 4-dicarboxyphenyl) hexafluoropropane dianhydride and 3,3 ', 4, 4' -biphenylsulfone tetracarboxylic dianhydride; the diamine compound is a compound containing a diamine compound having a siloxane bond and an aromatic diamine compound selected from the group consisting of a polysiloxane diamine compound, m-phenylenediamine, p-phenylenediamine, 2, 4-diaminotoluene, 4 '-diamino-3, 3' -dimethyl-1, 1 '-biphenyl, 4' -diamino-3, 3 '-dihydroxy-1, 1' -biphenyl, 3,4 '-diaminodiphenyl ether, 4' -diaminodiphenyl ether, 3 '-diaminodiphenyl sulfone, 4' -diaminodiphenyl sulfide, 2 '-bis (4-aminophenyl) propane, 2' -bis (4-aminophenyl) hexafluoropropane, 1, 3-bis (4-aminophenoxy) benzene, 1, 4-bis (4-aminophenoxy) benzene, 4 '-bis (4-aminophenoxy) biphenyl, 1, 3-bis [2- (4-aminophenyl) -2-propyl ] benzene, 1, 4-bis [2- (4-aminophenyl) -2-propyl ] benzene, 2' -bis [4- (4-aminophenoxy) phenyl ] propane, 2 '-bis [4- (4-aminophenoxy) phenyl ] hexafluoropropane, bis [4- (3-aminophenoxy) phenyl ] sulfone, bis [4- (4-aminophenoxy) phenyl ] sulfone, 2, 6-diaminopyridine, 2, 6-diamino-4-methylpyridine, N-methyl-pyridine, N-methyl-phenyl-ethyl-phenyl-methyl-phenyl-sulfone, N-methyl-phenyl-2, N-propyl-phenyl-2, 2' -bis [4- (4-aminophenoxy) phenyl ] sulfone, N-methyl-pyridine, N-methyl-phenyl-2, N-propyl-phenyl-sulfone, N-2, N-bis [4- (4-aminophenoxy) phenyl ] propane, N-phenyl-propane, N-phenyl-sulfone, N-methyl-pyridine, N-phenyl-2, N-methyl-pyridine, N-phenyl-2, N-pyridine, N-phenyl-methyl-pyridine, N-phenyl-2, N-phenyl-pyridine, N-phenyl-2, N-pyridine, N-phenyl-2, N-phenyl-pyridine, N-phenyl-pyridine, N-phenyl-2, N-phenyl-2, one or more of 4, 4' - (9-fluorenylidene) diphenylamine and α, α -bis (4-aminophenyl) -1, 3-diisopropylbenzene;

the alkaline compound is selected from one or more of primary amine, secondary amine, tertiary amine, pyrrole, imidazole, oxazole, pyrazole, isoxazole, thiazole, isothiazole, pyridine, pyridazine, pyrimidine, pyrazine, piperidine, piperazine and morpholine such as N, N-dimethylaminoethanol, triethylamine, triethanolamine, N-dimethylbenzylamine and ammonia; the alcohol is selected from one or more of benzyl alcohol, 4-methyl benzyl alcohol, 4-methoxy benzyl alcohol, ethylene glycol monophenyl ether, phenoxy-2-ethanol, cinnamyl alcohol, furfuryl alcohol, naphthyl methanol, 1-propanol, isopropanol, glycols and propylene glycol, and the ketone is selected from acetophenone; the water-soluble polar solvent is one or more selected from N, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, gamma-butyrolactone, gamma-valerolactone and sulfolane.

Preferably, the voltage of the electrophoresis is 20-80V, and the charge quantity is 0.01-100C; the drying is divided into 3 stages, the temperature of the first stage is 70-110 ℃, the time is 10-60 min, the temperature of the second stage is 160-180 ℃, the time is 10-60 min, the temperature of the third stage is 240-260 ℃, and the time is 30-60 min.

The application provides a power battery, which comprises a shell and a battery cell arranged in the shell, wherein the inner surface and/or the outer surface of the shell are/is coated with a polyimide coating. The inner surface and/or the outer surface of the shell of the power battery are/is coated with the polyimide coating, the thickness of the coating is uniform, and the appearance is attractive; the insulating property and the voltage resistance of the insulating material can reach 20kV, the insulating resistance DC 1kV and 5s are more than 15G omega, and the leakage current DC 2.7kV and 60s are less than 0.2 muA; the high-temperature-resistant material has excellent high-temperature-resistant performance, and can resist temperature for more than 1h at 350 ℃; the heat dissipation performance is good, and the heat conductivity coefficient is larger than 0.2W/m.K; the adhesive force with the shell is excellent and reaches 100/100 level; the hardness is high and reaches the 2H level. Therefore, the inner part and/or the outer part of the shell have good insulating performance, and plastic insulating films and/or pressure-sensitive insulating tapes commonly used in the industry at present can be effectively replaced, so that the assembly process is optimized, the assembly efficiency is improved, and the corresponding cost input such as equipment labor is saved.

On the other hand, due to the existence of the polyimide coating, the use of a plastic insulating film can be omitted in the shell, the balance of the electrolyte is not required to be achieved through slow permeation of micropores, and the electrolyte injection efficiency of the electrolyte can be further improved; the use of a pressure-sensitive insulating tape can be omitted outside the shell, and compared with the pressure-sensitive insulating tape, the thickness of the polyimide coating is thinner, the thermal resistance is lower, and the heat dissipation of the power battery module is facilitated; in addition, the plastic insulating film and/or the pressure-sensitive insulating tape are replaced inside and/or outside the shell, and due to the superior insulating property of the polyimide coating, the thickness of the polyimide coating can be greatly reduced relative to the thickness of the plastic insulating film and/or the pressure-sensitive insulating tape, so that considerable battery using space is saved, the battery using space is fully utilized, and the energy density of the power battery can be effectively improved.

Detailed Description

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.

Aiming at the problems that the inside and the outside of a power battery in the prior art need insulation protection, the insulation protection process in the prior art is complex and the like, the applicant carries out deep research on a polyimide coating and obtains the following conclusion: the use of plastic insulating film can be replaced if the inner surface of the housing can be directly insulated with a polyimide coating. By reducing the use of plastic insulating films, on one hand, the assembly procedures such as cell wrapping and the like can be reduced, so that the assembly efficiency is well improved, and the corresponding cost input such as equipment labor and the like is saved; on the other hand, the electrolyte is balanced without slowly permeating through micropores, and the electrolyte injection efficiency of the electrolyte can be further improved. The use of pressure sensitive insulating tape can be replaced if the housing outer surface can be insulated with a polyimide coating. By reducing the use of the pressure-sensitive insulating adhesive tape, on one hand, the assembly procedures such as wrapping and the like can be reduced, so that the assembly efficiency is well improved, and the corresponding cost investment such as equipment labor and the like is saved; on the other hand, compared with the pressure-sensitive insulating adhesive tape, the thickness of the polyimide coating is thinner, the thermal resistance is lower, and the heat dissipation of the power battery module is facilitated. In addition, if the inner surface and/or the outer surface of the shell are insulated by the polyimide coating, the plastic insulating film and/or the pressure-sensitive insulating tape are replaced, and the thickness of the polyimide coating can be greatly reduced relative to the plastic insulating film and the pressure-sensitive insulating tape due to the more excellent insulating property of the polyimide, so that considerable battery using space is saved, the using space of the battery is fully utilized, and the energy density of the power battery can be effectively improved.

In view of the foregoing analysis, an embodiment of the present invention discloses a power battery, which includes a casing and a battery cell disposed inside the casing, wherein an inner surface and/or an outer surface of the casing is coated with a polyimide coating.

The power battery provided by the application comprises a shell and a battery cell arranged in the shell, wherein the inner surface and/or the outer surface of the shell are/is coated with a polyimide coating. On the basis, in order to obtain a better effect, under the condition that the polyimide coating exists, the application provides a scheme, specifically, the polyimide coating is coated on the inner surface of the shell, and the surface of the battery cell is not coated with a plastic insulating film; the application also provides a scheme, in particular to a polyimide coating is coated on the outer surface of the shell, and the outer surface of the shell is not wrapped by a pressure-sensitive insulating tape; the application also provides a scheme, specifically the internal surface and the surface of casing all coat and have the polyimide coating, just the surface of electricity core does not wrap up plastic insulation film, the surface of casing does not wrap up pressure sensitive insulation sticky tape. According to the scheme, the power battery has good insulation on the inside and/or the outside, so that plastic insulation films and/or pressure-sensitive insulation tapes commonly used in the industry at present can be effectively replaced.

In the invention, the housing of the power battery can be in various structures, such as common square, round and the like, and the shape and size of the housing are not particularly limited; the material of the case is not particularly limited, and from the viewpoint of formability and strength, copper, aluminum, iron, silver, gold, nickel, titanium, tungsten, and the like can be used.

In the application, the polyimide coating is obtained by electrophoretic deposition of an electrophoretic solution of polyimide and drying to form a film.

The electrophoresis solution of the polyimide is an electrophoresis solution mixture obtained by dispersing solvent-soluble polyimide macromolecules into an aqueous mixed solvent, is alkalescent, has a neutralization rate of 50-200%, and is preferably 70-150%, so that a polyimide coating can be uniformly and continuously coated on the surface of a shell; wherein, the neutralization rate refers to the theoretical proportion of the alkaline compound and the anionic group in the polyimide high molecular polymer.

Specifically, the electrophoresis solution of the polyimide is prepared by mixing a plurality of components including polyimide, an alkaline chemical, a heat-conducting filler, alcohol or ketone, a water-soluble polar solvent and deionized water.

In the electrophoresis solution of the polyimide, the polyimide is a solvent-soluble polyimide high molecular polymer and can be prepared by a condensation polymerization reaction of a tetracarboxylic dianhydride compound and a diamine compound.

The tetracarboxylic dianhydride compound is a tetracarboxylic dianhydride compound containing an acetylene group, preferably 4, 4' - (acetylene-1, 2-diyl) diphthalic anhydride; in addition, other tetracarboxylic dianhydride compounds are also included, and aromatic tetracarboxylic dianhydride compounds are generally used to improve the effects of heat resistance, adhesion to an electrophoretic material, polymerization degree, and the like of polyimide, and examples of such compounds include pyromellitic dianhydride, 3 ', 4,4 ' -biphenyltetracarboxylic dianhydride, bis (3, 4-dicarboxyphenyl) ether dianhydride, 3 ', 4,4 ' -benzophenonetetracarboxylic dianhydride, bicyclo [2,2,2] oct-7-ene-2, 3,5, 6-tetracarboxylic dianhydride, 2,2 ' -bis (3, 4-dicarboxyphenyl) hexafluoropropane dianhydride, and 3,3 ', 4,4 ' -biphenylsulfone tetracarboxylic dianhydride; from the viewpoint of heat resistance of polyimide, adhesion to an electrophoretic material, and compatibility with a diamine compound, 3 ', 4, 4' -biphenyltetracarboxylic dianhydride, bis (3, 4-dicarboxyphenyl) ether dianhydride, 3 ', 4, 4' -benzophenonetetracarboxylic dianhydride, bicyclo [2,2,2] oct-7-ene-2, 3,5, 6-tetracarboxylic dianhydride, and 3,3 ', 4, 4' -biphenylsulfone tetracarboxylic dianhydride are preferable; the above-mentioned compounds may be used in combination of 2 or more.

The diamine compound is not particularly limited as long as it can be imidized with a tetracarboxylic dianhydride compound, but in order to improve the heat resistance, adhesion to an electrophoretic material, polymerization degree, and other properties of the polyimide, the diamine compound is preferably an aromatic diamine compound in the present application, and the compound may be, for example, m-phenylenediamine, p-phenylenediamine, 2, 4-diaminotoluene, 4 '-diamino-3, 3' -dimethyl-1, 1 '-biphenyl, 4' -diamino-3, 3 '-dihydroxy-1, 1' -biphenyl, 3,4 '-diaminodiphenyl ether, 4' -diaminodiphenyl ether, 3 '-diaminodiphenyl sulfone, 4' -diaminodiphenyl sulfone, and the like, 4,4 '-diaminodiphenylsulfide, 2' -bis (4-aminophenyl) propane, 2 '-bis (4-aminophenyl) hexafluoropropane, 1, 3-bis (4-aminophenoxy) benzene, 1, 4-bis (4-aminophenoxy) benzene, 4' -bis (4-aminophenoxy) biphenyl, 1, 3-bis [2- (4-aminophenyl) -2-propyl ] benzene, 1, 4-bis [2- (4-aminophenyl) -2-propyl ] benzene, 2 '-bis [4- (4-aminophenoxy) phenyl ] propane, 2' -bis [4- (4-aminophenoxy) phenyl ] hexafluoropropane, bis [4- (3-aminophenoxy) phenyl ] sulfone, One or more of bis [4- (4-aminophenoxy) phenyl ] sulfone, 2, 6-diaminopyridine, 2, 6-diamino-4-methylpyridine, 4' - (9-fluorenylidene) diphenylamine and α, α -bis (4-aminophenyl) -1, 3-diisopropylbenzene. These aromatic diamine compounds are suitably used in combination from the viewpoint of solubility in a solvent and heat resistance. Specifically, the aromatic diamine compound having a double bond structure, an isopropyl structure, an ether bond structure, a sulfo structure, and the like in the molecule is preferable from the viewpoint of solubility in a solvent, and specifically, may be one or more of bis [4- (3-aminophenoxy) phenyl ] sulfone, bis [4- (4-aminophenoxy) phenyl ] sulfone, 1, 3-bis [2- (4-aminophenyl) -2-propyl ] phenyl, and 1, 4-bis [2- (4-aminophenyl) -2-propyl ] benzene. From the viewpoint of heat resistance and flexibility, 2' -bis [4- (4-aminophenoxy) phenyl ] propane is preferable. The diamine compound may also contain a diamine compound having a silicon-oxygen bond, and by introducing a silicon-oxygen bond into the main molecular chain, the flexibility of the polyimide coating can be improved, and the problems such as peeling and chapping of the polyimide coating can be effectively prevented. Such a compound can be purchased commercially, for example, polysiloxane diamine compound KF-8010 (available from shin-Etsu chemical industries, Ltd.) or the like.

The tetracarboxylic dianhydride compound and the diamine compound are added in a nearly equal molar ratio, preferably 1: (0.95-1.05) to ensure the temperature resistance of the polyimide polymer and finally ensure the high temperature resistance of the polyimide coating.

The basic compound is not particularly limited as long as it can neutralize an anionic group in a polyimide molecule, and is preferably a basic nitrogen-containing compound, exemplified by a basic compound selected from primary amines such as N, N-dimethylaminoethanol, triethylamine, triethanolamine, N-dimethylbenzylamine, ammonia, secondary amines, tertiary amines, and the like; further, there may be mentioned five-or six-membered heterocyclic compounds such as pyrrole, imidazole, oxazole, pyrazole, isoxazole, thiazole, isothiazole, pyridine, pyridazine, pyrimidine, pyrazine, piperidine, piperazine, morpholine and the like; from the viewpoint of toxicity, nitrogen-containing heterocyclic compounds are preferable, and piperidine is more preferable. The amount of the basic compound used (neutralization rate) is based on the theoretical amount of the anionic group in the polyimide molecule, and is preferably 50 to 200% by mole, more preferably 70 to 150% by mole, and still more preferably 120 to 150% by mole; when the using amount is less than 50%, the polyimide microparticles are not easy to disperse in the process of dispersing with water; when the amount is more than 200%, the solubility of polyimide is greatly increased, and a part or all of polyimide is dissolved during the dispersion process, so that a suspension of the polyimide electrodeposition coating in a stable state cannot be obtained. In addition, especially when the molar ratio is 120-150%, the suspension has good stability and is not easy to settle in the storage process.

The heat-conducting filler is an insulating heat-conducting filler and can be selected from inorganic materials such as silicon oxide, aluminum oxide, zinc oxide, boron nitride, silicon nitride, aluminum nitride and the like, and the addition amount of the heat-conducting filler is 0.1-50 wt%. The power battery is extremely sensitive to temperature, the heat conducting performance of the polyimide coating can be well improved by adding the heat conducting filler, the internal heat dissipation efficiency of the power battery pack is convenient to improve, and the heat conducting filler has important significance for fully exerting the battery performance and prolonging the service life of the battery.

The alcohol or ketone may be an alcohol or ketone having a phenyl group, a furfuryl group or a naphthyl group, and exemplified by the ketone or alcohol being acetophenone, benzyl alcohol, 4-methylbenzyl alcohol, 4-methoxybenzyl alcohol, ethylene glycol monophenyl ether, phenoxy-2-ethanol, cinnamyl alcohol, furfuryl alcohol, naphthyl methanol, or the like, respectively. From the viewpoint of solvent toxicity, aliphatic alcohol solvents having an ether bond are preferable, and the alcohol is specifically selected from 1-propanol, isopropanol, glycols, and propylene glycols, and among these, dipropylene glycol, tripropylene glycol, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol methyl ether acetate, and the like are exemplified. These solvents may be used alone or in combination of 2 or more. The amount of the alcohol or ketone to be used may be determined according to the state of precipitation of the polyimide fine particles in the subsequent dilution process, and is preferably 10 to 50 wt%, more preferably 10 to 40 wt%, and still more preferably 10 to 35 wt% based on the total amount of the coating mixture. When the addition amount of the alcohol or ketone is less than 10%, the solubility of the polyimide is greatly increased, and a suspension of the polyimide electrophoretic paint in a stable state cannot be obtained; if the amount exceeds 50%, the dispersion tends not to be easily carried out during the dispersion with water.

The water-soluble polar solvent is exemplified by one or more selected from the group consisting of N, N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), γ -butyrolactone, γ -valerolactone and sulfolane, and is preferably NMP. The content of the water-soluble polar solvent is 20-60 wt%, and preferably, the content of the water-soluble polar solvent is 30-55 wt%.

The weight average molecular weight (Mw) of the polyimide high molecular polymer is preferably 20000 to 150000, and more preferably 30000 to 100000. When the molecular weight is less than 20000, the polyimide coating obtained by electrophoresis tends to have low flexibility and low heat resistance, and further, the appearance tends to be rough and the voltage resistance tends to be low; when the molecular weight is more than 150000, the solubility of the polyimide polymer is lowered, and dispersion tends to be difficult in the subsequent process for preparing a suspension. The weight average molecular weight of the present invention is measured by a GPC instrument and converted to a standard high molecular weight polyethylene. The content of the polyimide is 1-15 wt%, preferably 5-10 wt%.

The electrophoresis solution of the polyimide is a mixed solution of the polyimide, an alkaline compound, a heat-conducting filler, alcohol or ketone, a water-soluble polar solvent and deionized water.

The shell of the power battery is obtained by performing electrophoresis on the shell, and the method comprises the following specific steps: firstly, the surface of a shell is cleaned in an alkali cleaning mode, an acid cleaning mode, a solvent cleaning mode, a laser cleaning mode, a plasma cleaning mode and the like, then the cleaned shell is completely immersed into an electrophoresis solution, at the moment, the shell serves as an anode, a voltage of 20-80V is applied, and electrophoresis is carried out by electrifying. The electric charge amount is controlled through current and electrifying time, so that the electric charge amount is 0.01-100 ℃, the polyimide coating can slowly grow on the surface of the shell through the control of the electric charge amount, and the polyimide coating is finally obtained. And taking out the material after electrophoresis, blowing off the residual electrophoresis liquid on the surface by using airflow, and carrying out programmed heating drying film-forming treatment on the electrophoresed material to obtain the final polyimide coating.

The purpose of the temperature programming drying is to ensure that the surface coating solvent is orderly and completely volatilized, so that the thickness of the coating is more uniform, the appearance is more attractive, and the adhesion to the shell is better. In a specific embodiment, the drying process is performed in3 stages, wherein the first stage is drying at 70-110 ℃ for 10-60 min, drying at 160-180 ℃ for 10-60 min, and further drying at 240-260 ℃ for 30-60 min.

The invention provides a power battery, wherein the inside and/or the outside of a shell of the power battery has good insulating property, and a plastic insulating film and/or a pressure-sensitive insulating tape commonly used in the industry at present can be effectively replaced, so that the assembly process is optimized, the assembly efficiency is improved, and the cost investment of corresponding equipment labor and the like is saved. On the other hand, the use of a plastic insulating film is omitted in the shell, the balance of the electrolyte is achieved without slow permeation through micropores, and the electrolyte injection efficiency can be further improved; the use of a pressure-sensitive insulating tape is omitted outside the shell, and compared with the pressure-sensitive insulating tape, the thickness of the polyimide coating is thinner, the thermal resistance is lower, and the heat dissipation of the power battery module is facilitated; in addition, the inside and/or outside use of replacing plastic insulating film and/or pressure sensitive insulating tape of casing, because the more superior insulating properties of polyimide, the thickness of polyimide coating can attenuate by a wide margin for the thickness of plastic insulating film and pressure sensitive insulating tape to save considerable battery usage space, make full use of this battery usage space, can effectively promote power battery's energy density.

The power battery provided by the invention has the advantages that the power battery shell has excellent temperature resistance, the temperature resistance can exceed 1h at 350 ℃, the power battery shell has higher temperature resistance compared with the conventional pressure-sensitive insulating tape, and the conventional pressure-sensitive insulating tape can only resist about 180 ℃; the coating has good adhesive force, and is not easy to peel off; has excellent surface hardness, and can effectively prevent the shell from being damaged in the battery assembling process.

For further understanding of the present invention, the following detailed description of the power battery provided by the present invention is provided with reference to the following examples, and the scope of the present invention is not limited by the following examples.

The performance detection of the power battery is carried out according to the following modes:

1) withstand voltage characteristic test

Preparing tinfoils with the width of 1cm, clamping a sample to be detected between the two tinfoils, switching on a circuit, gradually increasing the voltage, and reading the voltage during damage, wherein the voltage application speed is 100V/s;

2) insulation resistance test

Clamping a sample between a positive electrode and a negative electrode, switching on a power supply without touching any other substance in the middle, gradually increasing the voltage to 1kV at a voltage rising speed of not more than 100V per second, and testing the insulation impedance of the sample;

3) leakage current test

Clamping a sample between a positive electrode and a negative electrode, switching on a power supply without contacting any other substance in the middle, gradually increasing the voltage to 2.7kV at a voltage rising speed of not more than 100V per second, keeping the voltage for 60s, and testing the leakage current of the sample;

4) thermal conductivity test

Testing by using a thermal conductivity tester according to JIS A1412 standard;

5) adhesion test

Testing by the Baige method according to JIS K5600;

6) hardness test

Testing according to JIS K5600 standard;

7) film thickness test

Measuring by using an eddy current type film thickness meter;

8) high temperature resistance test

Selecting a shell to be subjected to a high temperature resistance test, placing the shell in a blast type oven, heating the shell to 350 ℃, keeping the temperature for a certain time, taking out the shell, cooling the shell to room temperature, observing the appearance of the shell, and carrying out a voltage resistance characteristic test, an insulation impedance test, a leakage current test, a heat conductivity coefficient test, an adhesion test and a hardness test;

note: in the above items of the performance tests 1) to 8), the contents of the performance tests of the various cases in the following examples and comparative examples are described as follows, in view of the limitations of the test methods:

description 1: respectively testing the voltage resistance, the insulation resistance, the leakage current and the heat conduction characteristic of the shell only the outer surface of which is coated with the polyimide coating and the shell only the inner surface of which is coated with the polyimide coating;

description 2: adhesion and hardness tests were performed on the cases having both the inner and outer surfaces coated with the polyimide coating.

Example 1

In a stainless steel reactor with 3 ports, a stirring device with stirring blades is arranged, a reflux condenser pipe which can be used for reflux cooling is arranged, and a thermometer is arranged; 40.33g (0.13mol) of bis- (3, 4-dicarboxyphenyl) ether dianhydride (hereinafter, ODPA), 54.86g (0.065mol) of polysiloxane diamine compound KF-8010 (hereinafter, KF-8010), 7.83g (0.078mol) of γ -valerolactone, 12.38g (0.157mol) of pyridine, 504.6g of N-methyl-2-pyrrolidone (hereinafter, NMP) were charged in this order, and after stirring at a stirring rate of 200RMP for 30min at room temperature, the mixture was heated to 180 ℃ and kept at 2h, water was removed during the reaction, 39.56g (0.26mol) of 3, 5-diaminobenzoic acid (hereinafter, 3,5-DABA), 39.2-bis [4- (4-aminophenoxy) phenyl ] propane (hereinafter, BAPP), 53.37g (0.13mol) of 1, 3-bis [2- (4-aminophenyl) -2-propyl ] benzene (hereinafter, 1, 3-bis [2- (4-aminophenyl) -2-propyl ] benzene, were charged in this order Hereinafter referred to as bisanaline M)111.96g (0.325mol), bicyclo [2,2,2] oct-7-ene-2, 3,5, 6-tetracarboxylic dianhydride (hereinafter referred to as BTA)32.26g (0.13mol), 4' - (acetylene-1, 2-diyl) diphthalic anhydride (hereinafter referred to as EBPA)124.90g (0.393mol), ODPA40.33g (0.13mol), NMP 590.6g, stirring and reacting for 7 hours under the conditions of 180 ℃ and 200RMP, removing a water reflux during the reaction, cooling, adding 312.9g of NMP continuously for dilution to obtain a polyimide solution with a solid content of 25 wt%, and testing the molecular weight of the obtained polyimide polymer to 57000 in terms.

Taking 1000g of the prepared polyimide solution, putting the polyimide solution into a 3-port stainless steel stirring kettle, adding 580g of NMP and 17.7g of piperidine (the neutralization rate is 150%), stirring the mixture for 30min at room temperature, gradually dropwise adding 747g of propylene glycol monomethyl ether until the mixture is white and turbid, and continuously stirring the mixture for 1h to obtain 2344g of an intermediate of the polyimide electrophoretic paint, wherein the solid content of the intermediate is 10.7 wt%; and (3) taking the intermediate to be dispersed and mixed with water according to the ratio of 4:1 to obtain the electrophoresis liquid of the polyimide electrophoresis paint with the solid content of 8.5 wt%.

Immersing the square aluminum shell subjected to surface acid and alkali washing treatment into the electrophoresis solution to serve as a positive electrode, starting electrophoresis by electrifying direct current voltage of 40V, controlling the electrophoresis time to be 3min and 20s (the electric charge is 45C) by the current magnitude, and slowly growing the polyimide coating on the surface of the shell to obtain the polyimide coating on the inner surface and/or the outer surface of the shell.

In the process, the electrophoretic deposition of different parts of the shell is realized through the contact position of the electrophoretic liquid and the shell, and finally three different shells are obtained, namely the shell of which the inner surface and the outer surface are respectively coated with the polyimide coating, the shell of which only the outer surface is coated with the polyimide coating and the shell of which only the inner surface is coated with the polyimide coating.

Taking out after the electrophoretic deposition is finished, blowing off the residual electrophoretic liquid on the surface by using airflow, and carrying out programmed heating and drying treatment on the electrophoresed material: the first stage is drying at 80 deg.C for 20min, heating to 160 deg.C for 20min, and further heating to 240 deg.C for 60 min.

The case in which the inner surface and the outer surface were coated with the polyimide coating, the case in which only the outer surface was coated with the polyimide coating, and the case in which only the inner surface was coated with the polyimide coating, which were prepared in the above manner, were respectively subjected to a film thickness test, and the results of the film thickness tests of the portions, particularly the corners and other irregular portions, showed 40 ± 3 μm, indicating that the coating thicknesses were uniform.

And respectively testing the voltage resistance, the insulation resistance, the leakage current and the heat conduction characteristic of the shell only coated with the polyimide coating on the outer surface and the shell only coated with the polyimide coating on the inner surface, wherein the voltage resistance reaches 10kV, the insulation resistance reaches 17G omega under DC 1kV and 5s, the leakage current reaches 0.1 muA under DC 2.7kV and 60s, and the heat conduction coefficient is 0.25W/m.K.

Adhesion and hardness tests are carried out on the shell with the polyimide coating on the inner surface and the outer surface, and the results show that the adhesion with the shell reaches 100/100 level and the hardness reaches 2H level.

Example 2

Taking 1000g of the polyimide solution prepared in example 1, putting the polyimide solution into a 3-port stainless steel stirring kettle, adding 531g of NMP and 12g of piperidine (the neutralization rate is 100%), stirring the mixture at room temperature for 30min, gradually dropwise adding 716g of propylene glycol monomethyl ether until the mixture is turbid white, and continuing stirring the mixture for 1h to obtain 2259g of an intermediate of the polyimide electrophoretic paint, wherein the solid content of the intermediate is 11.1 wt%; and (3) taking the intermediate to be dispersed and mixed with water according to the ratio of 4:1 to obtain the electrophoresis liquid of the polyimide electrophoresis paint with the solid content of 10 wt%.

Immersing the round aluminum shell subjected to surface acid and alkali washing treatment into the electrophoresis solution to serve as a positive electrode, electrifying a direct current voltage of 40V to start electrophoresis, controlling the electrophoresis time to be 3s (the electric charge amount is 0.1C) through the current magnitude to enable the polyimide coating to slowly grow on the surface of the electrophoresed substance, and finally obtaining the polyimide coating on the inner surface and/or the outer surface of the shell.

In the process, the electrophoretic deposition of different parts of the shell is realized by controlling the contact position of the electrophoretic liquid and the shell, and finally three different shells are obtained, namely the shell with the inner surface and the outer surface both coated with the polyimide coating, the shell with the outer surface only coated with the polyimide coating and the shell with the inner surface only coated with the polyimide coating. Taking out after the electrophoretic deposition is finished, blowing off the residual electrophoretic liquid on the surface by using airflow, and carrying out programmed heating and drying treatment on the electrophoresed material: the first stage is drying at 80 deg.C for 10min, heating to 160 deg.C for 30min, and further heating to 260 deg.C for 40 min.

The case in which the inner surface and the outer surface were coated with the polyimide coating, the case in which only the outer surface was coated with the polyimide coating, and the case in which only the inner surface was coated with the polyimide coating, which were prepared in the above manner, were respectively subjected to a film thickness test, and the results of the film thickness tests of the portions, particularly the corners and other irregular portions, showed 10 ± 3 μm, indicating that the coating thicknesses were uniform.

And respectively carrying out voltage resistance, insulation resistance, leakage current and heat conduction characteristic tests on the shell only coated with the polyimide coating on the outer surface and the shell only coated with the polyimide coating on the inner surface, wherein the voltage resistance reaches 3kV, the insulation resistance reaches 15G omega under DC 1kV and 5s, the leakage current reaches 0.16 mu A under DC 2.7kV and 60s, and the heat conduction coefficient is 0.28W/m.K.

Adhesion and hardness tests are carried out on the shell with the polyimide coating on the inner surface and the outer surface, and the results show that the adhesion with the shell reaches 100/100 level and the hardness reaches 2H level.

Example 3

The battery core without being wrapped by the insulating plastic PP film is directly placed into the casing with the polyimide coating coated on the inner surface in the embodiment 1, and the battery assembly, the liquid injection, the charge and discharge operation and the like are performed according to the conventional method in the prior art, wherein 1000 test samples are obtained, and the number of the samples with poor short circuit and the like is counted to be zero, so that the insulating coating on the inner surface of the aluminum shell well plays a role in insulating the battery core and the aluminum shell.

Example 4

And (3) directly packaging the battery core which is not wrapped by the insulating plastic PP film into the shell of which the inner surface is coated with the polyimide coating in the embodiment 1, wherein the size of the shell is 148 multiplied by 98 multiplied by 28mm, assembling and injecting the battery according to the conventional method in the prior art, and recording the injection time to be less than 5 s.

Example 5

The case of example 1 above, in which only the inner surface was coated with the polyimide coating, and the case of example 1 above, in which only the outer surface was coated with the polyimide coating, were put into a 100 ℃ oven and held for 30min, and then taken out and placed under standard experimental conditions at 23 ℃ x 50% humidity, and the test surface temperatures were all 35 ℃ after 1 min.

The housing of example 1, in which the inner surface and the outer surface were coated with the polyimide coating, was placed in an oven at 100 ℃ for 30min, then taken out, placed under standard experimental conditions at 23 ℃ x 50% humidity, and the test surface temperature was 30 ℃ after 1 min.

Example 6

Taking 1000g of the polyimide solution prepared in the example 1, putting the polyimide solution into a 3-port stainless steel stirring kettle, adding 580g of NMP and 17.7g of piperidine (the neutralization rate is 150%), stirring the mixture at room temperature for 30min, gradually dropwise adding 747g of propylene glycol monomethyl ether until the mixture is white and turbid, and continuously stirring the mixture for 1h to obtain 2395g of an intermediate of the polyimide electrophoretic paint, wherein the solid content of the intermediate is 12.5 wt%; and (3) taking the intermediate to be dispersed and mixed with water according to the ratio of 4:1 to obtain the electrophoresis liquid of the polyimide electrophoresis paint with the solid content of 8.5 wt%.

Immersing the square aluminum shell subjected to surface acid and alkali cleaning treatment into the electrophoresis solution to serve as a positive electrode, starting electrophoresis by electrifying a direct current voltage of 80V, controlling the electrophoresis time to be 5min and 30s (the electric charge is 100C) by the current magnitude, and slowly growing the polyimide coating on the surface of the shell to obtain the polyimide coating on the inner surface and/or the outer surface of the shell.

In the process, the electrophoretic deposition of different parts of the shell is realized by controlling the contact position of the electrophoretic liquid and the shell, and finally three different shells are obtained, namely the shell with the inner surface and the outer surface both coated with the polyimide coating, the shell with the outer surface only coated with the polyimide coating and the shell with the inner surface only coated with the polyimide coating.

Taking out after the electrophoretic deposition is finished, blowing off the residual electrophoretic liquid on the surface by using airflow, and carrying out programmed heating and drying treatment on the electrophoresed material: the first stage is drying at 80 deg.C for 60min, heating to 160 deg.C for 60min, and further heating to 240 deg.C for 60 min.

The case in which the inner surface and the outer surface were coated with the polyimide coating, the case in which only the outer surface was coated with the polyimide coating, and the case in which only the inner surface was coated with the polyimide coating, which were prepared in the above manner, were respectively subjected to a film thickness test, and the results of the film thickness tests of various portions, particularly, the irregular portions such as corners, showed 60 ± 3 μm, indicating that the coating thicknesses were uniform.

And respectively testing the voltage resistance, the insulation resistance, the leakage current and the heat conduction characteristic of the shell only coated with the polyimide coating on the outer surface and the shell only coated with the polyimide coating on the inner surface, wherein the voltage resistance reaches 20kV, the insulation resistance reaches 20G omega under DC 1kV and 5s, the leakage current reaches 0.05 mu A under DC 2.7kV and 60s, and the heat conduction coefficient is 0.3W/m.K.

Adhesion and hardness tests are carried out on the shell with the polyimide coating on the inner surface and the outer surface, and the results show that the adhesion with the shell reaches 100/100 level and the hardness reaches 2H level.

Example 7

The shell with the polyimide coating in the example 1 is taken out, placed into a high-temperature oven at 350 ℃ for 1 hour, then taken out, cooled to room temperature, observed to have good appearance, and subjected to comprehensive performance evaluation.

And respectively testing the voltage resistance, the insulation resistance, the leakage current and the heat conduction characteristic of the shell only coated with the polyimide coating on the outer surface and the shell only coated with the polyimide coating on the inner surface, wherein the voltage resistance reaches 10kV, the insulation resistance reaches 17G omega under DC 1kV and 5s, the leakage current reaches 0.1 muA under DC 2.7kV and 60s, and the heat conduction coefficient is 0.25W/m.K.

Adhesion and hardness tests are carried out on the shell with the polyimide coating on the inner surface and the outer surface, and the results show that the adhesion with the shell reaches 100/100 level and the hardness reaches 2H level.

The results show that the shell coated with the polyimide coating has excellent high-temperature resistance, and can resist temperature for more than 1h at 350 ℃.

Comparative example 1

In a stainless steel reactor with 3 ports, a stirring device with stirring blades is arranged, a reflux condenser pipe which can be used for reflux cooling is arranged, and a thermometer is arranged; 40.33g (0.13mol) of ODPA, 0.065 g (KF-801054.86 g), 7.83g (0.078mol) of gamma-valerolactone, 12.38g (0.157mol) of pyridine and 504.6g of NMP are sequentially added, nitrogen is introduced for replacement at room temperature, the stirring speed is kept at 200RMP, the mixture is stirred for 30min, the temperature is increased to 180 ℃, the mixture is kept for 2h, and water is removed in the reaction process; then, 39.56g (0.26mol) of 3,5-DABA, 53.37g (0.13mol) of BAPP, M111.96 g (0.325mol) of bisazoline, 32.26g (0.13mol) of BTA, 115.63g (0.393mol) of BPDA, 40.33g (0.13mol) of ODPA, 590.6g of NMP, 180 ℃ and 200RMP were added to the mixture to stir the mixture for reaction for 6 hours, and a water reflux during the reaction was removed; cooling, and continuously adding 304g of NMP for dilution to obtain a polyimide solution with the solid content of 25 wt%; the molecular weight of the polyimide polymer obtained was measured and converted to 57000.

Taking 1000g of the prepared polyimide solution, putting the polyimide solution into a 3-port stainless steel stirring kettle, adding 580g of NMP and 17.7g of piperidine (the neutralization rate is 150%), stirring the mixture for 30min at room temperature, gradually dropwise adding 747g of propylene glycol monomethyl ether until the mixture is white and turbid, and continuously stirring the mixture for 1h to obtain 2344g of an intermediate of the polyimide electrophoretic paint, wherein the solid content of the intermediate is 10.7 wt%; and (3) taking the intermediate to be dispersed and mixed with water according to the ratio of 4:1 to obtain the electrophoresis liquid of the polyimide electrophoresis paint with the solid content of 8.5 wt%.

Immersing a square aluminum shell subjected to surface acid and alkali washing treatment into the electrophoresis solution to serve as a positive electrode, electrifying by using 40V direct current to start electrophoresis, controlling the electrophoresis time for 3min and 20s (the electric charge is 45C) through the current magnitude, slowly growing a polyimide coating on the surface of an electrophoresed substance, and finally obtaining the polyimide coating on the inner surface and/or the outer surface of the shell.

In the process, the electrophoretic deposition of different parts of the shell is realized by controlling the contact position of the electrophoretic liquid and the shell, and finally three different shells are obtained, namely the shell with the inner surface and the outer surface both coated with the polyimide coating, the shell with the outer surface only coated with the polyimide coating and the shell with the inner surface only coated with the polyimide coating. Taking out after the electrophoretic deposition is finished, blowing off the residual electrophoretic liquid on the surface by using airflow, and carrying out programmed heating and drying treatment on the electrophoresed material: the first stage is drying at 80 deg.C for 20min, heating to 160 deg.C for 20min, and further heating to 240 deg.C for 60 min.

The case in which the inner surface and the outer surface were coated with the polyimide coating, the case in which only the outer surface was coated with the polyimide coating, and the case in which only the inner surface was coated with the polyimide coating, which were prepared in the above manner, were respectively subjected to a film thickness test, and the results of the film thickness tests of the portions, particularly the corners and other irregular portions, showed 40 ± 3 μm, indicating that the coating thicknesses were uniform.

And respectively testing the voltage resistance, the insulation resistance, the leakage current and the heat conduction characteristic of the shell only coated with the polyimide coating on the outer surface and the shell only coated with the polyimide coating on the inner surface, wherein the voltage resistance reaches 7.5kV, the insulation resistance reaches 15G omega under DC 1kV and 5s, the leakage current reaches 0.2 mu A under DC 2.7kV and 60s, and the heat conduction coefficient is 0.15W/m.K.

Adhesion and hardness tests are carried out on the shell with the polyimide coating on the inner surface and the outer surface, and the results show that the adhesion with the shell reaches 83/100 level and the hardness reaches 1H level.

Comparative example 2

Taking 1000g of the polyimide solution prepared in example 1, putting the polyimide solution into a 3-port stainless steel stirring kettle, adding 531g of NMP and 29.4g of piperidine (the neutralization rate is 250%), stirring the mixture at room temperature for 30min, gradually dropwise adding 686g of propylene glycol monomethyl ether until the mixture is turbid white, and continuing stirring the mixture for 1h to obtain 2246g of an intermediate of the polyimide electrophoretic paint, wherein the solid content of the intermediate is 11.1 wt%; and (3) taking the intermediate to be dispersed and mixed with water according to the ratio of 4:1 to obtain the electrophoresis liquid of the polyimide electrophoresis paint with the solid content of 9 wt%.

And completely immersing the round aluminum shell subjected to surface acid and alkali washing treatment into the electrophoresis solution to serve as a positive electrode, electrifying the round aluminum shell with direct current voltage of 40V to start electrophoresis, and generating a large amount of bubbles on the surface of the shell to prevent normal electrophoretic deposition.

Comparative example 3

The PET blue film adhesive tape (with the thickness of 120-130 mu m) for the power battery is purchased in the market, an adhesive tape laminating test machine is carried out on the outer surface (without a polyimide coating) of the shell by using automatic laminating equipment, 1000 automatic laminating devices are used as basic units, laminating position deviation, laminating bubbles and laminating wrinkles are marked as bad, the final qualification rate of statistics is 99/100, and the adhesive tape laminating is indicated to inevitably lead to poor laminating and rework.

Further, the case to which the PET blue tape was attached was subjected to withstand voltage characteristics, insulation resistance, and leakage current tests, and the results were as follows: the withstand voltage reaches 6kV, the insulation resistance DC 1kV and 5s reach 5G omega, and the leakage current DC 2.7kV and 60s reach 0.02 mA.

Comparative example 4

The method comprises the steps of directly loading a battery core which is not wrapped by an insulating plastic film into a metal shell (the polyimide coating is not coated in the shell), carrying out battery assembly, liquid injection, charge and discharge operation and the like according to a conventional method in the prior art, carrying out 500 test samples, counting samples with poor short circuit and the like, and carrying out short circuit on all results.

Comparative example 5

The commercially available water-based polyester insulating electrophoretic paint is purchased, a square aluminum shell subjected to surface acid and alkali washing treatment is immersed in the electrophoretic solution, electrophoresis is started by electrifying, the polyester coating slowly grows on the surface of an electrophoresed substance by controlling the current magnitude, and the polyester coating is obtained on the inner surface and/or the outer surface of the shell.

In the process, the electrophoretic deposition of different parts of the shell is realized by controlling the contact position of the electrophoretic liquid and the shell, and finally three different shells are obtained, namely the shell with the polyester coating on the inner surface and the outer surface, the shell with the polyester coating on only the outer surface and the shell with the polyester coating on only the inner surface. Taking out after the electrophoretic deposition is finished, blowing off the residual electrophoretic liquid on the surface by using airflow, and carrying out programmed heating and drying treatment on the electrophoresed material: the first stage is drying at 80 deg.C for 30min, and heating to 150 deg.C for 30 min.

The case in which the inner surface and the outer surface were coated with the polyester coating, the case in which only the outer surface was coated with the polyester coating, and the case in which only the inner surface was coated with the polyester coating, which were prepared in the above manner, were respectively subjected to a film thickness test, and the results of the film thickness tests at various portions, particularly at irregular portions such as corners, showed 40 ± 5 μm, indicating that the coating thicknesses were uniform.

And respectively testing the voltage resistance, the insulation resistance, the leakage current and the heat conduction characteristic of the shell only coated with the polyester coating on the outer surface and the shell only coated with the polyester coating on the inner surface, wherein the voltage resistance reaches 4kV, the insulation resistance DC 1kV and 5s reach 3G omega, the leakage current DC 2.7kV and 60s reach 0.1mA, and the heat conduction coefficient is 0.13W/m.K.

The shell with the inner surface and the outer surface both coated with the polyester coating is subjected to heat conduction property, adhesive force and hardness tests, and the result shows that the adhesive force with the shell reaches 100/100 level, and the hardness reaches 1H level.

Comparative example 6

The cell wrapped by the insulating plastic PP film was directly put into the square aluminum case with the polyimide coating on the inner surface in example 1, wherein the size of the case was 148 × 98 × 28mm, and the battery was assembled and injected according to the conventional method of the prior art, and the injection time was recorded as 15 s.

Comparative example 7

The battery case of the same size as in example 5, without polyimide coating, was surface-wrapped with commercially available PET blue film tape, placed in a 100 ℃ oven for 30min, then removed, placed under standard experimental conditions at 23 ℃ x 50% humidity, and tested at a surface temperature of 55 ℃ after 1 min.

Comparative example 8

The shell just after electrophoresis in example 1 was dried by programmed temperature setting of 80 ℃ for 10min in the first stage and 160 ℃ for 30 min.

The case in which the inner surface and the outer surface were coated with the polyimide coating, the case in which only the outer surface was coated with the polyimide coating, and the case in which only the inner surface was coated with the polyimide coating, which were prepared in the above manner, were respectively subjected to a film thickness test, and the results of the film thickness tests of the portions, particularly the corners and other irregular portions, showed 40 ± 3 μm, indicating that the coating thicknesses were uniform.

And respectively carrying out voltage resistance, insulation resistance, leakage current and heat conduction characteristic tests on the shell only coated with the polyimide coating on the outer surface and the shell only coated with the polyimide coating on the inner surface, wherein the voltage resistance reaches 5kV, the insulation resistance reaches 14G omega under DC 1kV and 5s, the leakage current reaches 0.21 muA under DC 2.7kV and 60s, and the heat conduction coefficient is 0.25W/m.K.

The shell with the polyimide coating on the inner surface and the outer surface is subjected to heat conduction property, adhesive force and hardness tests, and the result shows that the adhesive force with the shell reaches 90/100 level, and the hardness reaches F level.

Comparative example 9

A case (without a polyimide coating) having the same size as that of example 7 was taken out, wrapped with a commercially available PET blue tape, placed in a high-temperature oven at 350 ℃ for 1 hour, taken out, cooled to room temperature, and observed for appearance, and the PET blue tape was brittle, and no subsequent test could be performed.

Through the embodiment and the comparative example, the shell for the power battery provided by the invention has good insulating property, high temperature resistance and heat dissipation performance; the insulating material has excellent insulating property, the withstand voltage reaches 20kV, the insulating resistance DC 1kV and 5s are more than 15G omega, and the leakage current DC 2.7kV and 60s are less than 0.2 muA; the high-temperature-resistant material has excellent high-temperature-resistant performance, and can resist temperature for more than 1h at 350 ℃; the heat dissipation performance is good, and the heat conductivity coefficient is larger than 0.2W/m.K; the adhesive force with the shell is excellent and reaches 100/100 level; the hardness is high and reaches the 2H level. By using the coating, the interior and/or exterior of the shell of the power battery can be subjected to effective coating electrophoresis, and the use of a plastic insulating film in the shell and/or an insulating pressure-sensitive adhesive tape outside the shell can be effectively replaced.

The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (12)

1. The power battery comprises a shell and a battery cell arranged inside the shell, wherein the inner surface and/or the outer surface of the shell is/are coated with a polyimide coating.

2. The power cell of claim 1, wherein the housing is an aluminum alloy housing.

3. The power battery according to claim 1, wherein the polyimide coating has a thickness of 1-60 μm.

4. The power battery of claim 1, wherein the inner surface of the casing is coated with a polyimide coating, and the surface of the cell is not coated with a plastic insulating film.

5. The power cell of claim 1, wherein an outer surface of the housing is coated with a polyimide coating and the outer surface of the housing is not wrapped with a pressure sensitive insulating tape.

6. The power battery of claim 1, wherein the inner surface and the outer surface of the shell are coated with polyimide coatings, the surface of the cell is not coated with a plastic insulating film, and the outer surface of the shell is not coated with a pressure-sensitive insulating tape.

7. The power battery according to claim 1, wherein the polyimide coating is obtained by electrophoretic deposition of an electrophoretic solution of polyimide and drying to form a film.

8. The power battery according to any one of claims 1-7, wherein the electrophoretic fluid of the polyimide comprises polyimide, an alkaline compound, a heat conductive filler, alcohol or ketone, a water-soluble polar solvent and deionized water.

9. The power battery according to claim 8, wherein the electrophoretic solution of the polyimide is weakly alkaline, and the neutralization rate of the basic compound is 50-200% based on the theoretical amount of the anionic group of the polyimide.

10. The power battery according to claim 8, wherein based on the electrophoretic solution of the polyimide, the content of the polyimide is 1 to 15 wt%, the content of the alcohol or the ketone is 10 to 50 wt%, the content of the water-soluble polar solvent is 20 to 60 wt%, the content of the heat-conducting filler is 0.1 to 50 wt%, and the content of the deionized water is 10 to 40 wt%.

11. The power battery according to claim 9 or 10, wherein the polyimide is obtained by reacting a tetracarboxylic dianhydride compound and a diamine compound in a molar ratio of 1 (0.95-1.05), and has a weight average molecular weight of 20000-150000;

the tetracarboxylic dianhydride compound is one or more of a tetracarboxylic dianhydride compound containing acetylene groups and an aromatic tetracarboxylic dianhydride compound, and is specifically selected from 4,4 '- (acetylene-1, 2-diyl) diphthalic anhydride, pyromellitic dianhydride, 3', 4,4 '-biphenyltetracarboxylic dianhydride, bis (3, 4-dicarboxyphenyl) ether dianhydride, 3', 4,4 '-benzophenone tetracarboxylic dianhydride, bicyclo [2,2,2] oct-7-ene-2, 3,5, 6-tetracarboxylic dianhydride, 2, 2' -bis (3, 4-dicarboxyphenyl) hexafluoropropane dianhydride and 3,3 ', 4, 4' -biphenylsulfone tetracarboxylic dianhydride; the diamine compound is a compound containing a diamine compound having a siloxane bond and an aromatic diamine compound selected from the group consisting of a polysiloxane diamine compound, m-phenylenediamine, p-phenylenediamine, 2, 4-diaminotoluene, 4 '-diamino-3, 3' -dimethyl-1, 1 '-biphenyl, 4' -diamino-3, 3 '-dihydroxy-1, 1' -biphenyl, 3,4 '-diaminodiphenyl ether, 4' -diaminodiphenyl ether, 3 '-diaminodiphenyl sulfone, 4' -diaminodiphenyl sulfide, 2 '-bis (4-aminophenyl) propane, 2' -bis (4-aminophenyl) hexafluoropropane, 1, 3-bis (4-aminophenoxy) benzene, 1, 4-bis (4-aminophenoxy) benzene, 4 '-bis (4-aminophenoxy) biphenyl, 1, 3-bis [2- (4-aminophenyl) -2-propyl ] benzene, 1, 4-bis [2- (4-aminophenyl) -2-propyl ] benzene, 2' -bis [4- (4-aminophenoxy) phenyl ] propane, 2 '-bis [4- (4-aminophenoxy) phenyl ] hexafluoropropane, bis [4- (3-aminophenoxy) phenyl ] sulfone, bis [4- (4-aminophenoxy) phenyl ] sulfone, 2, 6-diaminopyridine, 2, 6-diamino-4-methylpyridine, N-methyl-pyridine, N-methyl-phenyl-ethyl-phenyl-methyl-phenyl-sulfone, N-methyl-phenyl-2, N-propyl-phenyl-2, 2' -bis [4- (4-aminophenoxy) phenyl ] sulfone, N-methyl-pyridine, N-methyl-phenyl-2, N-propyl-phenyl-sulfone, N-2, N-bis [4- (4-aminophenoxy) phenyl ] propane, N-phenyl-propane, N-phenyl-sulfone, N-methyl-pyridine, N-phenyl-2, N-methyl-pyridine, N-phenyl-2, N-pyridine, N-phenyl-methyl-pyridine, N-phenyl-2, N-phenyl-pyridine, N-phenyl-2, N-pyridine, N-phenyl-2, N-phenyl-pyridine, N-phenyl-pyridine, N-phenyl-2, N-phenyl-2, one or more of 4, 4' - (9-fluorenylidene) diphenylamine and α, α -bis (4-aminophenyl) -1, 3-diisopropylbenzene;

the alkaline compound is selected from one or more of primary amine, secondary amine, tertiary amine, pyrrole, imidazole, oxazole, pyrazole, isoxazole, thiazole, isothiazole, pyridine, pyridazine, pyrimidine, pyrazine, piperidine, piperazine and morpholine such as N, N-dimethylaminoethanol, triethylamine, triethanolamine, N-dimethylbenzylamine and ammonia; the alcohol is selected from one or more of benzyl alcohol, 4-methyl benzyl alcohol, 4-methoxy benzyl alcohol, ethylene glycol monophenyl ether, phenoxy-2-ethanol, cinnamyl alcohol, furfuryl alcohol, naphthyl methanol, 1-propanol, isopropanol, glycols and propylene glycol, and the ketone is selected from acetophenone; the water-soluble polar solvent is one or more selected from N, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, gamma-butyrolactone, gamma-valerolactone and sulfolane.

12. The power battery according to claim 7, wherein the voltage of the electrophoresis is 20-80V, and the charge amount is 0.01-100C; the drying is divided into 3 stages, the temperature of the first stage is 70-110 ℃, the time is 10-60 min, the temperature of the second stage is 160-180 ℃, the time is 10-60 min, the temperature of the third stage is 240-260 ℃, and the time is 30-60 min.