Modified epoxy resin and preparation method thereof, insulating composition, battery case and preparation method thereof, secondary battery and electric device

Abstract

The invention provides modified epoxy resin and a preparation method thereof, an insulating composition and application thereof, a battery shell and a preparation method thereof, a secondary battery and an electric device. The modified epoxy resin comprises an epoxy resin main chain; the ether-bond-containing straight-chain alkane and / or the ether-bond-containing straight-chain heteroalkane are / is connected with a carbon atom of a main chain of the epoxy resin, the silicon-containing branched chain and / or the fluorine-containing branched chain are / is connected with the carbon atom of the main chain of the epoxy resin, and the nitrogen-containing chain segment is connected with an epoxy-terminated carbon atom on the main chain of the epoxy resin. When the modified epoxy resin provided by the invention is applied to preparation of a battery shell, the insulating property of the battery shell can be improved, so that the insulating property of a secondary battery is improved.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and in particular to a modified epoxy resin and a preparation method thereof, an insulating composition and an application thereof, a battery casing and a preparation method thereof, a secondary battery and an electrical device. Background Art

[0002] Secondary batteries represented by lithium-ion batteries have the characteristics of high capacity and long life, so they are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes and electric tools, etc. As the application range of batteries becomes wider and wider, the requirements for the performance of secondary batteries are becoming increasingly stringent. In existing secondary batteries, the bonding strength between the battery cell and the insulating layer that wraps the battery cell shell is not high, and the insulating layer is prone to fall off during use, affecting the insulation performance of the secondary battery. Summary of the invention

[0003] The purpose of the present application is to provide a modified epoxy resin and a preparation method thereof, an insulating composition and an application thereof, a battery casing and a preparation method thereof, a secondary battery and an electrical device, which can improve the insulation performance of the secondary battery.

[0004] In order to achieve the above object, the first aspect of the present application provides a modified epoxy resin, comprising:

[0005] Epoxy resin backbone; and

[0006] Ether bond-containing straight-chain alkanes and / or ether bond-containing straight-chain heteroalkanes connected to the carbon atoms of the epoxy resin main chain, silicon-containing side chains and / or fluorine-containing side chains connected to the carbon atoms of the epoxy resin main chain, and nitrogen-containing segments connected to the terminal epoxy carbon atoms on the epoxy resin main chain.

[0007] The modified epoxy resin provided in the present application has been subjected to a modification treatment on the epoxy resin body. When the modified epoxy resin is applied to the preparation of the insulating coating of the secondary battery shell, the ether bond-containing straight-chain alkane and / or ether bond-containing straight-chain heteroalkane on the main chain included in the structural formula thereof can be used as a flexible segment to improve the flexibility of the modified epoxy resin, thereby improving the toughness and bending resistance of the insulating coating. The silicon-containing side chain and / or fluorine-containing side chain on the structural formula of the modified epoxy resin can be used as a hydrophobic segment to improve the resistance to wet heat aging and water resistance of the insulating coating, thereby helping to improve the insulating performance and service life of the insulating coating and the battery shell.

[0008] In some embodiments of the present application, the modified epoxy resin satisfies at least one of the following conditions:

[0009] (1a) The epoxy resin main chain comprises the structural formula shown in the following formula (1):

[0010]

[0011] (1b) The ether bond-containing straight-chain alkane and / or ether bond-containing straight-chain heteroalkane includes a structural formula as shown in the following formula (2):

[0012]

[0013] (1c) The silicon-containing side chain comprises a structural formula as shown in the following formula (3), and the fluorine-containing side chain comprises a structural formula as shown in the following formula (4):

[0014]

[0015] In formula (3), R 10 include n is an integer from 0 to 10;

[0016] In formula (4), R 11 Including fluorinated segments, R 12 including one or more of hydrogen atoms and C1-C5 alkyl groups,

[0017] Optionally, the fluorine-containing segment comprises fluorine atoms and One or more of;

[0018] (1d) The nitrogen-containing segment comprises the structural formula shown in the following formula (5):

[0019]

[0020] In formula (5), R 20 and R 21 Each independently comprises one or more of a hydrogen atom, an alkyl group, a cycloalkyl group, an epoxy group, an aryl group, a heteroaryl group, a heteroalkyl group, a heterocyclic group, an amino group, an alkylene group, a halogen group, a hydroxyl group, an alkylamino group and an arylalkyl group;

[0021] In the above formulas (1) to (5), Each independently represents C1 to C 100 One or more of the chain alkanes and chain heteroalkanes, * represents the connection site.

[0022] The epoxy resin main chain in formula (1) mainly provides the main chain segment or main skeleton for the modified epoxy resin, so as to facilitate the cross-linking and curing of the modified epoxy resin when it is subsequently applied to the insulating coating of the battery shell.

[0023] The ether bond-containing straight-chain alkane and / or ether bond-containing straight-chain heteroalkane on the main chain in formula (2) can serve as a flexible segment to improve the toughness and bending resistance of the insulating coating, thereby improving the insulating properties of the insulating coating, the battery casing and the battery.

[0024] The silicon-containing side chain located on the side chain in formula (3) can serve as a hydrophobic segment to improve the heat and moisture aging resistance and water resistance of the insulating coating, thereby improving the insulating performance and service life of the insulating coating and the battery casing.

[0025] The fluorine-containing side chains in formula (4) can serve as hydrophobic segments to improve the heat and moisture aging resistance and water resistance of the insulating coating, thereby improving the insulating properties and service life of the insulating coating and the battery casing.

[0026] In some embodiments of the present application, the modified epoxy resin comprises a structural formula as shown in the following formula (6):

[0027]

[0028] In formula (6), R1 includes At least one of the following, where R 10 include n is an integer from 0 to 10; R 11 Including fluorinated segments, R 12 including one or more of a hydrogen atom, a C1-C5 alkyl group and a carboxyl group,

[0029] Optionally, the fluorine-containing segment comprises fluorine atoms and One or more of;

[0030] R2 includes Among them, R 20 and R 21 Each independently comprises one or more of a hydrogen atom, an alkyl group, a cycloalkyl group, an epoxy group, an aryl group, a heteroaryl group, a heteroalkyl group, a heterocyclic group, an amino group, an alkylene group, a halogen group, a hydroxyl group, an alkylamino group and an arylalkyl group;

[0031] R3 includes

[0032] Each independently represents C1 to C 100 One or more of the chain alkanes and chain heteroalkanes, * represents the connection site.

[0033] When the modified epoxy resin in formula (6) is used to prepare the insulating coating of the secondary battery shell, the R3 segment located on the main chain can be used as a flexible segment to improve the flexibility of the modified epoxy resin, thereby improving the toughness and bending resistance of the insulating coating, and then improving the insulating properties of the insulating coating, the battery shell and the battery. The R1 segment located on the side chain can be used as a hydrophobic segment to improve the resistance to wet heat aging and water resistance of the insulating coating due to its lower polarity, thereby improving the insulating properties and service life of the insulating coating and the battery shell. In addition, the R2 segment located at the end of the main chain can improve the flexibility of the segment and the insulating properties of the coating.

[0034] In some embodiments of the present application, the epoxy equivalent of the modified epoxy resin is 500-2000, and can be optionally 800-1200.

[0035] The epoxy equivalent weight of the modified epoxy is within the above range. When it is subsequently used for the electrophoretic preparation of the insulating coating, it is beneficial to improve the electrophoretic efficiency and the leveling performance of the insulating coating and make the thickness of the insulating coating uniform.

[0036] The second aspect of the present application provides a method for preparing the modified epoxy resin described in the first aspect of the present application, comprising:

[0037] Utilizing phenolic substances to carry out chain extension treatment on epoxy resin to obtain chain extension reactants;

[0038] Performing a grafting treatment on the chain extension reactant using a silicon-containing organic compound and / or a fluorine-containing organic compound to obtain a grafted reactant;

[0039] The grafting reactant is subjected to ring-opening treatment by using an amine substance to obtain the modified epoxy resin.

[0040] In the above method, by using phenolic substances to perform chain extension treatment on epoxy resin, the chain segments contained in the phenolic substances can be added to the main chain of the epoxy resin, so that the main chain of the epoxy resin can be extended; by using silicon-containing organic matter and / or fluorine-containing organic matter to perform grafting treatment on the chain extension reactant, the silicon-containing and / or fluorine-containing chain segments in the silicon-containing organic matter and / or fluorine-containing organic matter can be grafted onto the main chain of the epoxy resin, giving the resin moisture and heat resistance; by using amine substances to perform ring-opening treatment on the grafted reactant, part of the epoxy groups contained in the epoxy resin can be opened and a certain number of hydroxyl groups can be generated; when the modified epoxy resin is subsequently used in the preparation of battery insulating coatings, these hydroxyl groups are conducive to cross-linking and curing with the curing agent, thereby forming a dense three-dimensional network structure.

[0041] In some embodiments of the present application, the method satisfies at least one of the following conditions:

[0042] (2a) The epoxy resin includes one or more of glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, linear aliphatic epoxy resin and alicyclic epoxy resin,

[0043] One or both of bisphenol A epoxy resin and bisphenol F epoxy resin can be selected;

[0044] (2b) the phenolic substance comprises one or more of phenol and alkylphenol,

[0045] Optionally, the phenolic substance includes one or more of bisphenol A, bisphenol F, butylphenol, pentylphenol, heptylphenol, octylphenol, nonylphenol, decylphenol and dodecylphenol;

[0046] (2c) the silicon-containing organic compound includes polydimethylsiloxane, and the fluorine-containing organic compound includes fluorine acrylic acid;

[0047] Optionally, the polydimethylsiloxane includes one or both of vinyl polydimethylsiloxane and amino polydimethylsiloxane, and may further be vinyl polydimethylsiloxane;

[0048] Optionally, the fluorine-containing acrylic acid includes one or more of 2-fluoroacrylic acid, hexafluorobutyl acrylate and hexafluorobutyl methacrylate, and may further be 2-fluoroacrylic acid;

[0049] (2d) The amine substance includes one or more of methylamine, aniline, diethylamine, ethylenediamine, diisopropylamine, diethanolamine, triethanolamine and tetrabutylammonium bromide, and diethylamine can be selected.

[0050] The present application selects the above-mentioned amine substances for ring-opening of epoxy resin, mainly utilizing the nucleophilicity of the amine substances; the ammonium salt formed is hydrophilic and soluble in water to form an aqueous solution, thereby facilitating the reaction.

[0051] In some embodiments of the present application, the method satisfies at least one of the following conditions:

[0052] (3a) The temperature of the chain extension treatment is 120°C to 150°C;

[0053] (3b) The temperature of the grafting treatment is 100° C. to 120° C.;

[0054] (3c) The temperature of the ring-opening treatment is 60° C. to 80° C.;

[0055] (3d) The mass ratio of the epoxy resin, the phenolic substance, the silicon-containing organic matter and / or the fluorine-containing organic matter to the amine substance is 10:(3-5):(2-7):(0.1-0.3).

[0056] The mass ratio of the above four reactants is within the above range, and the corresponding reaction temperatures of the chain extension treatment, grafting treatment and ring opening treatment are used at the same time, so that the reaction of each step can be fully carried out, which is conducive to the acquisition of the modified epoxy described in the first aspect of the present application.

[0057] The third aspect of the present application provides an insulating composition, comprising the modified epoxy resin described in the first aspect of the present application or the modified epoxy resin prepared according to the method described in the second aspect of the present application, and a curing agent.

[0058] The insulating composition provided in the present application includes a modified epoxy resin and a curing agent. When it is used in the preparation of an insulating coating for a battery casing, the curing agent reacts with the modified epoxy resin and cross-links and cures it into a modified epoxy resin polymer having a three-dimensional network structure. The three-dimensional network structure of the polymer is beneficial to improving the insulating pressure resistance, mechanical strength and bonding strength of the insulating coating to the battery casing substrate.

[0059] In some embodiments of the present application, the insulating composition further comprises a protonic acid and an organic solvent.

[0060] Optionally, the protonic acid includes one or more of lactic acid, acetic acid and hydrochloric acid, and may further be hydrochloric acid;

[0061] Optionally, the organic solvent includes an ether organic solvent;

[0062] Further optionally, the ether organic solvent includes one or more of ethylene glycol butyl ether, ethylene glycol methyl ether, diethylene glycol butyl ether and diethylene glycol ethyl ether.

[0063] The ether solvent selected in the present application has good hydrophilicity and can exist stably in the insulating composition.

[0064] In some embodiments of the present application, the insulating composition satisfies at least one of the following conditions:

[0065] (1) The molar ratio of the epoxy group in the modified epoxy resin to the curing agent is 1:(1-0.7);

[0066] (2) The curing agent includes a hydroxyl-terminated isocyanate, which may be one or more of a hydroxyl-fully blocked isocyanate and a hydroxyl-half-blocked isocyanate, and may further be a hydroxyl-fully blocked isocyanate;

[0067] (3) The pH value of the insulating composition is 5.8 to 6.6.

[0068] The pH value of the insulating composition is within the above range, which is conducive to the acidification (ionization) of the modified epoxy resin to make it positively charged. Therefore, when the insulating composition is used as a raw material for the electrophoretic preparation of a battery insulating coating, it is conducive to its deposition on the surface of the battery casing substrate serving as the negative electrode, thereby obtaining an insulating coating, and is conducive to improving the bonding strength between the insulating coating and the battery casing substrate.

[0069] The fourth aspect of the present application provides a use of the insulating composition described in the third aspect of the present application in the preparation of a battery casing.

[0070] A fifth aspect of the present application provides a battery housing, comprising:

[0071] a housing substrate; and

[0072] An insulating coating is provided on at least part of the surface of the housing substrate, wherein the insulating coating comprises a modified epoxy resin polymer, and the raw material for preparing the modified epoxy resin polymer comprises the insulating composition according to any one of claims 8-10.

[0073] A sixth aspect of the present application provides a battery housing, comprising:

[0074] a housing substrate; and

[0075] An insulating coating is provided on at least part of the surface of the housing substrate, wherein the insulating coating comprises a modified epoxy resin polymer, and the structural unit of the modified epoxy resin polymer comprises:

[0076] Ether bond-containing straight-chain alkanes and / or ether bond-containing straight-chain heteroalkanes connected to the carbon atoms of the epoxy resin main chain, silicon-containing side chains and / or fluorine-containing side chains connected to the carbon atoms of the epoxy resin main chain, nitrogen-containing segments connected to the terminal epoxy carbon atoms on the epoxy resin main chain, and isocyanate-containing segments connected to the carbon atoms of the epoxy resin main chain by ether bonds.

[0077] An insulating coating is provided on the shell substrate of the battery shell. The modified epoxy resin polymer contained in the insulating coating has a dense three-dimensional network structure, which is beneficial to improving the insulation pressure resistance, mechanical strength and bonding strength of the insulating coating with the shell substrate.

[0078] In some embodiments of the present application, the modified epoxy resin polymer includes a structural unit shown in the following formula (7):

[0079]

[0080] In formula (7), R1 includes At least one of the following, where R 10 include n is an integer from 0 to 10; R11 Including fluorinated segments, R 12 including one or more of a hydrogen atom, a C1-C5 alkyl group and a carboxyl group,

[0081] Optionally, the fluorine-containing segment comprises fluorine atoms and One or more of;

[0082] R2 includes Among them, R 20 and R 21 Each independently comprises one or more of a hydrogen atom, an alkyl group, a cycloalkyl group, an epoxy group, an aryl group, a heteroaryl group, a heteroalkyl group, a heterocyclic group, an amino group, an alkylene group, a halogen group, a hydroxyl group, an alkylamino group and an arylalkyl group;

[0083] R3 includes

[0084] R4 includes

[0085] Each independently represents C1 to C 100 One or more of the chain alkanes and chain heteroalkanes, * represents the connection site.

[0086] The modified epoxy resin polymer includes a structural unit shown in formula (7), in which the R3 segment located on the main chain has a certain bending ability and softness due to the ether bond that allows the molecular chain to rotate and swing freely to a certain extent, so it can be used as a flexible segment to improve the flexibility of the modified epoxy resin polymer, thereby improving the toughness and bending resistance of the insulating coating, and further improving the insulating properties of the insulating coating, battery casing and battery. The R1 segment located on the side chain has a lower polarity, so it can be used as a hydrophobic segment to improve the wet heat aging resistance and water resistance of the insulating coating, thereby improving the insulating properties and service life of the insulating coating and battery casing. In addition, the R2 segment located at the end of the main chain is easy to ionize under acidic conditions to make the modified epoxy resin positively charged, so it can be used for the subsequent preparation of insulating coatings by electrophoresis; it can also play a chain extension effect, improving the flexibility of the segment and the insulating properties of the coating.

[0087] In some embodiments of the present application, the battery housing satisfies at least one of the following conditions:

[0088] (1) The weight average molecular weight of the modified epoxy resin polymer is 1000 to 4000;

[0089] (2) The degree of polymerization of the modified epoxy resin polymer is 1 to 10;

[0090] (3) The viscosity of the modified epoxy resin polymer at a temperature of 120° C. is 10,000 to 25,000.

[0091] The weight average molecular weight of the modified epoxy resin polymer is within the above range, which is beneficial to improving the viscosity and surface energy of the polymer, thereby improving the bonding strength between the insulating coating and the shell substrate, and the water resistance of the insulating coating.

[0092] In some embodiments of the present application, the battery housing satisfies at least one of the following conditions:

[0093] (1) The thickness of the insulating coating is 20 μm to 70 μm, and can be 40 μm to 50 μm;

[0094] (2) The breakdown voltage of the insulating coating is 500V to 8000V, and can be optionally 2700V to 7500V.

[0095] The thickness of the insulating coating is within the above range, which ensures the insulation performance of the battery shell while not affecting the performance of the battery cell itself (such as capacity, cycle performance, etc.).

[0096] The seventh aspect of the present application provides a method for preparing the battery casing according to the sixth aspect of the present application, comprising:

[0097] Performing electrophoresis treatment on the shell substrate using the insulating composition as an electrophoretic liquid to form a deposition layer on at least a portion of the surface of the shell substrate;

[0098] The outer shell substrate covered with the deposition layer is cured to form the insulating coating to obtain the battery outer shell.

[0099] Compared with the existing method of directly coating insulating materials on the battery casing substrate, the above method provided in the present application can improve the bonding strength (binding force) between the insulating coating and the casing substrate, and its curing temperature is low and the energy consumption is low, which is conducive to large-scale production.

[0100] In some embodiments of the present application, the method satisfies at least one of the following conditions:

[0101] (1) The voltage of the electrophoresis treatment is 200V to 250V,

[0102] Optionally, the temperature of the electrophoresis treatment is 29°C to 35°C;

[0103] (2) The curing temperature is 150°C to 190°C.

[0104] The voltage of the electrophoresis treatment is within the above range, which is conducive to the deposition of the positively charged modified epoxy resin on the surface of the shell substrate and reaches a certain film thickness.

[0105] The curing temperature is within the above range, which can unblock the hydroxyl groups in the hydroxyl-terminated isocyanate curing agent, thereby achieving and promoting the cross-linking curing reaction between the modified epoxy resin and the curing agent.

[0106] The eighth aspect of the present application provides a secondary battery, comprising the battery casing described in the sixth aspect of the present application or the battery casing prepared according to the method described in the seventh aspect of the present application.

[0107] The ninth aspect of the present application provides an electrical device, comprising the secondary battery described in the eighth aspect of the present application.

[0108] The electric device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0109] Figure 1 is a schematic diagram of a secondary battery according to one embodiment of the present application.

[0110] Figure 2 yes Figure 1 An exploded view of a secondary battery according to an embodiment of the present application is shown.

[0111] Figure 3 is a schematic diagram of a secondary battery according to another embodiment of the present application.

[0112] Figure 4 is a schematic diagram of a secondary battery according to another embodiment of the present application.

[0113] Figure 5 yes Figure 4 An exploded view of a secondary battery according to an embodiment of the present application is shown.

[0114] Figure 6 FIG. 1 is a schematic diagram of an electric device using a secondary battery according to an embodiment of the present application as a power source.

[0115] Description of reference numerals:

[0116] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0117] Hereinafter, the modified epoxy resin and its preparation method, insulating composition and its application, battery casing and its preparation method, secondary battery and electric device of the present application are described in detail with appropriate reference to the accompanying drawings, and the embodiments are specifically disclosed. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0118] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0119] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0120] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0121] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0122] In this application, unless otherwise specified, the terms or phrases used have the following meanings:

[0123] "Alkyl" refers to a saturated hydrocarbon containing primary (normal) carbon atoms, or secondary carbon atoms, or tertiary carbon atoms, or quaternary carbon atoms, or a combination thereof. Phrases containing this term, for example, "C1-C9 alkyl" refers to an alkyl group containing 1 to 9 carbon atoms, each occurrence of which can be independently C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, C8 alkyl or C9 alkyl. Suitable examples include, but are not limited to, methyl (Me, -CH3), ethyl (Et, -CH2CH3), 1-propyl (n-Pr, n-propyl, -CH2CH2CH3), 2-propyl (i-Pr, i-propyl, -CH(CH3)2), 1-butyl (n-Bu, n-butyl, -CH2CH2CH2CH3), 2-methyl-1-propyl (i-Bu, i-butyl, -CH2CH(CH3)2), 2-butyl (s-Bu, s-butyl, -CH(C H3)CH2CH3), 2-methyl-2-propyl (t-Bu, t-butyl, -C(CH3)3), 1-pentyl (n-pentyl, -CH2CH2CH2CH2CH3), 2-pentyl (-CH(CH3)CH2CH2CH3), 3-pentyl (-CH(CH2CH3)2), 2-methyl-2-butyl (-C(CH3)2CH2CH3), 3-methyl-2-butyl (-CH(CH3)CH(CH3)2), 3-methyl-1-butyl (- CH2CH2CH(CH3)2), 2-methyl-1-butyl (-CH2CH(CH3)CH2CH3), 1-hexyl (-CH2CH2CH2CH2CH2CH3), 2-hexyl (-CH(CH3)CH2CH2CH2CH3), 3-hexyl (-CH(CH2CH3)(CH2CH2CH3)), 2-methyl-2-pentyl (-C(CH3)2CH2CH2CH3), 3-methyl-2-pentyl (-CH(CH3)CH( 2), 2-methyl-3-pentyl (-CH(CH2CH3)CH(CH3)2), 2,3-dimethyl-2-butyl (-C(CH3)2CH(CH3)2), 3,3-dimethyl-2-butyl (-CH(CH3)C(CH3)3 and octyl (-(CH2)7CH3).

[0124] "Cycloalkyl" refers to a non-aromatic hydrocarbon containing ring carbon atoms, which can be a monocyclic alkyl, a spirocyclic alkyl, or a bridged cycloalkyl. Phrases containing this term, for example, "C3-C9 cycloalkyl" refers to a cycloalkyl containing 3 to 9 carbon atoms, each occurrence of which can be independently C3 cycloalkyl, C4 cycloalkyl, C5 cycloalkyl, C6 cycloalkyl, C7 cycloalkyl, C8 cycloalkyl or C9 cycloalkyl. Suitable examples include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and cycloheptyl. In addition, "cycloalkyl" may also contain one or more double bonds, and representative examples of cycloalkyl containing double bonds include cyclopentenyl, cyclohexenyl, cyclohexadienyl and cyclobutadienyl.

[0125] "Epoxy" refers to a group having an -O-alkyl group, i.e., an alkyl group as defined above connected to a parent core structure via an oxygen atom. Phrases containing this term, for example, "C1-C9 alkoxy" means that the alkyl portion contains 1 to 9 carbon atoms, and each occurrence can be independently C1 alkoxy, C4 alkoxy, C5 alkoxy, C6 alkoxy, C7 alkoxy, C8 alkoxy or C9 alkoxy. Suitable examples include, but are not limited to, methoxy (-O-CH3 or -OMe), ethoxy (-O-CH2CH3 or -OEt) and tert-butoxy (-OC(CH3)3 or -OtBu).

[0126] "Aryl" refers to an aromatic hydrocarbon group derived from an aromatic ring compound by removing a hydrogen atom. It can be a monocyclic aromatic group, a condensed aromatic group, or a polycyclic aromatic group. For polycyclic rings, at least one is an aromatic ring system. For example, "C5-C 20 "Aryl" refers to an aromatic group containing 5 to 20 carbon atoms, and each occurrence can be independently C5 aromatic group, C6 aromatic group, C 10 Aryl, C 14 Aryl, C 18 Aryl or C 20 Suitable examples include, but are not limited to, benzene, biphenyl, naphthalene, anthracene, phenanthrene, perylene, triphenylene, and derivatives thereof.

[0127] "Heteroaryl" means that at least one carbon atom in an aryl group is replaced by a non-carbon atom, such as a nitrogen atom, an oxygen atom, or a sulfur atom. 10The term "heteroaryl" refers to a heteroaryl group containing 3 to 10 carbon atoms, which, at each occurrence, may be independently C3 heteroaryl, C4 heteroaryl, C5 heteroaryl, C6 heteroaryl, C7 heteroaryl or C8 heteroaryl. Suitable examples include, but are not limited to, furan, benzofuran, thiophene, benzothiophene, pyrrole, pyrazole, triazole, imidazole, oxazole, oxadiazole, thiazole, tetrazole, indole, carbazole, pyrroloimidazole, pyrrolopyrrole, thienopyrrole, thienothiophene, furopyrrole, furanofuran, thienofuran, benzisoxazole, benzisothiazole, benzimidazole, pyridine, pyrazine, pyridazine, pyrimidine, triazine, quinoline, isoquinoline, o-naphthyridine, quinoxaline, phenanthridine, primary idine, quinazoline and quinazolinone.

[0128] "Heteroalkyl" means that at least one carbon atom is replaced by a non-carbon atom on the basis of an alkyl group, and the non-carbon atom can be an N atom, an O atom, an S atom, etc. For example, if the carbon atom connected to the parent core structure in the alkyl group is replaced by a non-carbon atom, the resulting heteroalkyl group is an alkoxy group (e.g., -OCH3, etc.), an amine (e.g., -NHCH3, -N(CH3)2, etc.) or a thioalkyl group (e.g., -SCH3). If the carbon atom not connected to the parent core structure in the alkyl group is replaced by a non-carbon atom, the resulting heteroalkyl group is an alkyl ether (e.g., -CH2CH2-O-CH3, etc.), an alkylamine (e.g., -CH2NHCH3, -CH2N(CH3)2, etc.) or a thioalkyl ether (e.g., -CH2-S-CH3). If the terminal carbon atom of the alkyl group is replaced by a non-carbon atom, the resulting heteroalkyl group is a hydroxyalkyl group (e.g., -CH2CH2-OH), an aminoalkyl group (e.g., -CH2NH2) or an alkylthiol group (e.g., -CH2CH2-SH). Phrases containing this term, for example, "C1-C9 heteroalkyl" refers to heteroalkyl groups containing 1 to 9 carbon atoms, and each occurrence can be independently C2 heteroalkyl, C3 heteroalkyl, C4 heteroalkyl, C5 heteroalkyl, C7 heteroalkyl, C8 heteroalkyl or C9 heteroalkyl.

[0129] "Heterocyclyl" means that at least one carbon atom on the basis of a cycloalkyl group is replaced by a non-carbon atom, and the non-carbon atom can be an N atom, an O atom, an S atom, etc., and can be a saturated ring or a partially unsaturated ring. Phrases containing this term, for example, "C4-C9 heterocyclyl" means a heterocyclyl group containing 4 to 9 carbon atoms, each occurrence of which can be independently C4 heteroalkyl, C6 heteroalkyl, C7 heteroalkyl, C8 heteroalkyl or C9 heteroalkyl. Suitable examples include, but are not limited to: dihydropyridyl, tetrahydropyridyl (piperidyl), tetrahydrothienyl, sulfur-oxidized tetrahydrothienyl, tetrahydrofuranyl, tetrahydroquinolyl, tetrahydroisoquinolyl, dihydroindole.

[0130] "Amino" refers to a derivative of ammonia having the structural features of the formula -N(X)2, wherein each "X" is independently H, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocyclyl, etc. Non-limiting examples of amino include -NH2, -N(alkyl), -NH(alkyl), -N(cycloalkyl), -NH(cycloalkyl), -N(heterocyclyl), -NH(heterocyclyl), -N(aryl), -NH(aryl), -N(alkyl)(aryl), -N(alkyl)(heterocyclyl), -N(cycloalkyl)(heterocyclyl), -N(aryl)(heteroaryl), -N(alkyl)(heteroaryl), etc.

[0131] "Halogen" or "halo" refers to F, Cl, Br or I.

[0132] "Alkylene" refers to a hydrocarbon group with two monovalent radical centers derived from an alkyl group by removing a hydrogen atom, which can be a saturated branched alkyl group or a saturated straight-chain alkyl group. For example, "C1-C9 alkylene" means that the alkyl portion contains 1 to 9 carbon atoms, and each occurrence can be independently C1 alkylene, C4 alkylene, C5 alkylene, C6 alkylene, C7 alkylene, C8 alkylene or C9 alkylene. Suitable examples include, but are not limited to, methylene (-CH2-), 1,1-ethyl (-CH(CH3)-), 1,2-ethyl (-CH2CH2-), 1,1-propyl (-CH(CH2CH3)-), 1,2-propyl (-CH2CH(CH3)-), 1,3-propyl (-CH2CH2CH2-) and 1,4-butyl (-CH2CH2CH2CH2-).

[0133] "Alkylamino" refers to an amino group substituted by at least one alkyl group. Suitable examples include, but are not limited to, -NH2, -NH(CH3), -N(CH3)2, -NH(CH2CH3), -N(CH2CH3)2.

[0134] "Arylalkyl" refers to a hydrocarbon group derived from an alkyl group in which at least one hydrogen atom bonded to a carbon atom is replaced by an aryl group. The aryl portion may include 5 to 20 carbon atoms, and the alkyl portion may include 1 to 9 carbon atoms. Suitable examples include, but are not limited to, benzyl, 2-phenylethyl-1-yl, naphthylmethyl, 2-naphthylethyl-1-yl, naphthobenzyl, and 2-naphthophenylethyl-1-yl.

[0135] "Alkanes" refer to saturated hydrocarbons that do not contain a carbon ring structure in the molecule. Suitable examples may include, but are not limited to: -CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2CH2-.

[0136] "Alkanes" refer to alkanes in which at least one carbon atom is replaced by a non-carbon atom or a carbon ring. The non-carbon atom may be an N atom, an O atom, an S atom, etc.; the carbon ring may be a benzene ring, etc. Suitable examples may include, but are not limited to: -CH2CH2CH2O-, -CH2CH2CH2CH2S-, -CH2CH2CH2NH- and wait.

[0137] At present, in secondary batteries, the insulation protection of the battery cell (including the shell) is mostly coated with PET blue film. The battery cell and the PET blue film are bonded by gluing, and the bonding strength is low. In addition, the battery cells need to be bonded and fixed with structural adhesive. The bonding strength between the blue film and the structural adhesive cannot be met, and the blue film is prone to fall off. In addition, the coating process of the PET blue film is complicated, and it is easy to have defects such as bubbles and wrinkles during the coating process. The blue film itself is easy to break, which affects the insulation performance of the battery cell and the outside; and the coating film needs to be repeatedly laminated at the edges and corners of the battery cell, which affects the subsequent module assembly size. In addition, the battery pack condenses water dew during use, which is easy to penetrate from the blue film splicing area, connecting the battery cell shell and the external structure, causing the blue film to lose its insulation performance, resulting in a decrease in the insulation performance of the secondary battery.

[0138] In order to solve the above technical problems, the present application proposes a modified epoxy resin, which, when used in the preparation of an insulating coating for a battery shell, can improve the bonding strength between the insulating coating and the shell substrate, enhance the insulation pressure resistance of the battery shell, and thereby enhance the insulation performance of the secondary battery.

[0139] In a first aspect, the present application provides a modified epoxy resin, which includes an epoxy resin main chain, and ether-bonded straight-chain alkanes and / or ether-bonded straight-chain heteroalkanes connected to carbon atoms of the epoxy resin main chain, silicon-containing side chains and / or fluorine-containing side chains connected to carbon atoms of the epoxy resin main chain, and nitrogen-containing segments connected to terminal epoxy carbon atoms on the epoxy resin main chain.

[0140] In this application, unless otherwise specified, a straight-chain alkane containing an ether bond refers to a straight-chain alkane having an ether bond in its main chain, i.e., at least one carbon atom on its chain segment is replaced by an oxygen atom. A straight-chain heteroalkane containing an ether bond refers to a straight-chain alkane having an ether bond in its main chain, i.e., at least one carbon atom on its chain segment is replaced by an oxygen atom, and at least one carbon atom on its chain segment is replaced by a carbon ring or a non-carbon atom, wherein the non-carbon atom may be an N atom, an S atom, etc.; the carbon ring may be a benzene ring, etc.

[0141] In this application, unless otherwise specified, a silicon-containing side chain refers to a side branch contained in the main chain, and at least one carbon atom on the side branch is replaced by at least one of a silicon atom and a silicon-containing segment. A fluorine-containing side chain refers to a side branch contained in the main chain, and at least one carbon atom on the side branch is replaced by at least one of a fluorine atom and a fluorine-containing segment. Among them, a silicon-containing segment refers to a molecular segment containing at least a silicon atom, and a fluorine-containing segment refers to a molecular segment containing at least a fluorine atom.

[0142] In the present application, unless otherwise specified, a nitrogen-containing segment refers to a molecular segment that at least contains a nitrogen atom.

[0143] In the present application, unless otherwise specified, an isocyanate segment refers to a molecular segment that at least contains an isocyanate group.

[0144] The modified epoxy resin provided by the present application has been modified to treat the epoxy resin body. When the modified epoxy resin is applied to the preparation of the insulating coating of the secondary battery shell, the ether bond-containing straight-chain alkane and / or the ether bond-containing straight-chain heteroalkane included in its structural formula are located on the main chain, and because the ether bond can make the molecular chain rotate and swing freely to a certain extent, the molecular chain can have a certain bending ability and flexibility, so it can be used as a flexible segment to improve the flexibility of the modified epoxy resin, thereby improving the toughness and bending resistance of the insulating coating. Thus, in the process of battery processing, preparation and use, since the insulating coating has good toughness and bending resistance, it is not easy to break, and compared with conventional insulating films (such as PET blue films), the modified epoxy resin is conducive to improving the insulating properties of insulating coatings, battery shells and batteries. The silicon-containing side chain and / or fluorine-containing side chain in the modified epoxy resin structure can be used as a hydrophobic segment to improve the heat and moisture aging resistance and water resistance of the insulating coating, as silicon and / or fluorine have low polarity and are not easily soluble in water. This helps improve the insulating properties and service life of the insulating coating and the battery housing. In addition, the nitrogen-containing segment at the end of the main chain can play a role in chain extension, thereby improving the flexibility of the modified epoxy resin and the insulating properties of the insulating coating.

[0145] In some embodiments, the epoxy resin main chain comprises the structural formula shown in the following formula (1):

[0146]

[0147] The epoxy resin main chain in formula (1) mainly provides the main chain segment or main skeleton for the modified epoxy resin, so as to facilitate the cross-linking and curing of the modified epoxy resin when it is subsequently applied to the insulating coating of the battery shell.

[0148] In some embodiments, the straight-chain alkane containing an ether bond or the straight-chain heteroalkane containing an ether bond comprises a structural formula as shown in the following formula (2):

[0149]

[0150] The ether bond-containing straight-chain alkane and / or ether bond-containing straight-chain heteroalkane on the main chain in formula (2) can serve as a flexible segment to improve the toughness and bending resistance of the insulating coating, thereby improving the insulating properties of the insulating coating, the battery casing and the battery.

[0151] In some embodiments, the silicon-containing side chain comprises a structural formula as shown in the following formula (3):

[0152]

[0153] In formula (3), R 10 include n is an integer of 0 to 10. For example, n can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0154] The silicon-containing side chain on the side chain in formula (3) can be used as a hydrophobic segment to improve the heat and moisture aging resistance and water resistance of the insulating coating, thereby improving the insulation performance and service life of the insulating coating and the battery casing. Wherein, the value of n is within the above range, which is conducive to further improving the heat and moisture aging resistance and water resistance of the insulating coating.

[0155] In some embodiments, the fluorine-containing side chain comprises a structural formula as shown in the following formula (4):

[0156]

[0157] In formula (4), R 11 Including fluorinated segments, R 12 It includes one or more of a hydrogen atom, a C1-C5 alkyl group and a carboxyl group.

[0158] The fluorine-containing side chains in formula (4) can serve as hydrophobic segments to improve the heat and moisture aging resistance and water resistance of the insulating coating, thereby improving the insulating properties and service life of the insulating coating and the battery casing.

[0159] In some embodiments, the fluorine-containing segment includes fluorine atoms and One or more of .

[0160] In some embodiments, the nitrogen-containing segment comprises the structural formula shown in the following formula (5):

[0161]

[0162] In formula (5), R 20 and R 21Each independently includes one or more of a hydrogen atom, an alkyl group, a cycloalkyl group, an epoxy group, an aryl group, a heteroaryl group, a heteroalkyl group, a heterocyclic group, an amino group, an alkylene group, a halogen, a hydroxyl group, an alkylamino group, and an arylalkyl group.

[0163] In some embodiments, in the above formulas (1) to (5), Indicates C1~C 100 One or more of the chain alkanes and chain heteroalkanes, * represents the connection site.

[0164] In some embodiments, the modified epoxy resin comprises the structural formula shown in the following formula (6):

[0165]

[0166] In formula (6), R1 includes At least one of the following, where R 10 include n is an integer from 0 to 10; R 11 Including fluorinated segments, R 12 Includes one or more of a hydrogen atom, a C1-C5 alkyl group, and a carboxyl group;

[0167] R2 includes Among them, R 20 and R 21 Each independently comprises one or more of a hydrogen atom, an alkyl group, a cycloalkyl group, an epoxy group, an aryl group, a heteroaryl group, a heteroalkyl group, a heterocyclic group, an amino group, an alkylene group, a halogen group, a hydroxyl group, an alkylamino group and an arylalkyl group;

[0168] R3 includes

[0169] Each independently represents C1 to C 100 One or more of the chain alkanes and chain heteroalkanes, * represents the connection site.

[0170] When the modified epoxy resin in formula (6) is applied to the preparation of the insulating coating of the secondary battery shell, the R3 segment located on the main chain has a certain bending ability and softness due to the ether bond that allows the molecular chain to rotate and swing freely to a certain extent, so it can be used as a flexible segment to improve the flexibility of the modified epoxy resin, thereby improving the toughness and bending resistance of the insulating coating, and then improving the insulating properties of the insulating coating, the battery shell and the battery. The R1 segment located on the side chain has a lower polarity, so it can be used as a hydrophobic segment to improve the wet heat aging resistance and water resistance of the insulating coating, thereby improving the insulating properties and service life of the insulating coating and the battery shell. In addition, the R2 segment located at the end of the main chain is easy to ionize under acidic conditions to make the modified epoxy resin positively charged, so it can be used for the subsequent preparation of the insulating coating by electrophoresis; it can also play a chain extension effect, improving the flexibility of the segment and the insulating properties of the coating.

[0171] In some embodiments, the epoxy equivalent of the modified epoxy resin is 500 to 2000. For example, the epoxy equivalent can be 500, 800, 1100, 1400, 1700, 2000 or any range thereof. Optionally, the epoxy equivalent is 800 to 1200.

[0172] The epoxy equivalent of epoxy resin is a well-known meaning in the art and can be measured by methods known in the art. For example, the epoxy equivalent can be tested by quaternary ammonium bromide titration.

[0173] The epoxy equivalent weight of the modified epoxy resin is within the above range, that is, the number of epoxy groups in the modified epoxy resin is within a certain range. When it is subsequently used for the electrophoretic preparation of the insulating coating, it is beneficial to improve the electrophoretic efficiency and the leveling performance of the insulating coating, and make the thickness of the insulating coating uniform.

[0174] In a second aspect, the present application provides a method for preparing the modified epoxy resin described in the first aspect of the present application, which may include the following steps:

[0175] S10, using a phenolic substance to perform chain extension treatment on the epoxy resin to obtain a chain extension reactant;

[0176] S20, performing a grafting treatment on the chain extension reactant using a silicon-containing organic compound and / or a fluorine-containing organic compound to obtain a grafted reactant;

[0177] S30, performing a ring-opening treatment on the grafting reactant using an amine substance to obtain the modified epoxy resin.

[0178] In the above method, by using phenolic substances to perform chain extension treatment on epoxy resin, the chain segments contained in the phenolic substances can be added to the main chain of the epoxy resin, so that the main chain of the epoxy resin can be extended; by using silicon-containing organic matter and / or fluorine-containing organic matter to perform grafting treatment on the chain extension reactant, the silicon-containing and / or fluorine-containing chain segments in the silicon-containing organic matter and / or fluorine-containing organic matter can be grafted onto the main chain of the epoxy resin, giving the resin moisture and heat resistance; by using amine substances to perform ring-opening treatment on the grafted reactant, part of the epoxy groups contained in the epoxy resin can be opened and a certain number of hydroxyl groups can be generated; when the modified epoxy resin is subsequently used in the preparation of battery insulating coatings, these hydroxyl groups are conducive to cross-linking and curing with the curing agent, thereby forming a dense three-dimensional network structure.

[0179] It is understood that when performing the treatment in each step of S10 to S30, each reactant can be dissolved in an organic solvent for reaction. The organic solvent may include an ether organic solvent, and the ether organic solvent may include but is not limited to one or more of ethylene glycol butyl ether, ethylene glycol methyl ether, diethylene glycol butyl ether and diethylene glycol ethyl ether. Ether organic solvents have a relatively high boiling point and are suitable for use in chain extension and branching treatment.

[0180] In some embodiments, the epoxy resin includes, but is not limited to, one or more of glycidyl ether epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, linear aliphatic epoxy resins, and alicyclic epoxy resins.

[0181] Optionally, the epoxy resin is one or both of bisphenol A epoxy resin and bisphenol F epoxy resin.

[0182] In some embodiments, the phenolic substance includes, but is not limited to, one or more of phenol and alkylphenol.

[0183] In some embodiments, the alkylphenol includes one or more of butylphenol, pentylphenol, heptylphenol, octylphenol, nonylphenol, decylphenol, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 4,4-dihydroxydiphenylmethane (bisphenol F), and dodecylphenol.

[0184] In some embodiments, the silicon-containing organic compound includes polydimethylsiloxane, and the fluorine-containing organic compound includes fluorine acrylic acid.

[0185] In some embodiments, the polydimethylsiloxane includes but is not limited to one or both of vinyl polydimethylsiloxane and amino polydimethylsiloxane, and vinyl polydimethylsiloxane may be selected.

[0186] In some embodiments, the fluorine-containing acrylic acid includes, but is not limited to, one or more of 2-fluoroacrylic acid, hexafluorobutyl acrylate, and hexafluorobutyl methacrylate, and 2-fluoroacrylic acid may be selected.

[0187] In some embodiments, the amine substance includes, but is not limited to, one or more of methylamine, aniline, diethylamine, ethylenediamine, diisopropylamine, diethanolamine, triethanolamine and tetrabutylammonium bromide, and diethylamine may be selected.

[0188] In some embodiments, a catalyst may be added in each of the steps S10 to S30 above.

[0189] In some embodiments, the catalyst may include, but is not limited to, one or more of dibutyltin dilaurate, stannous octoate, chelated tin, and metal salt catalysts.

[0190] The present application selects the above-mentioned amine substances for ring-opening of epoxy resin, mainly utilizing the nucleophilicity of the amine substances; the ammonium salt formed is hydrophilic and soluble in water to form an aqueous solution, thereby facilitating the reaction.

[0191] As a non-limiting example, the reactions in the above steps S10 to S30 can be expressed as the following reaction formulas (10) to (30), wherein the reaction in step S10 can be exemplified as:

[0192]

[0193] The chain extension reactant obtained by reaction formula (10) is recorded as R1', and the reaction in step S20 can be exemplified as:

[0194]

[0195] The grafted reactant obtained by reaction formula (20) is recorded as R2', and the reaction in step S30 can be exemplified as:

[0196]

[0197] In some embodiments, the temperature of the chain extension treatment is 120° C. to 150° C. For example, the temperature of the chain extension treatment can be 120° C., 130° C., 140° C., 150° C. or any range thereof.

[0198] In some embodiments, the temperature of the grafting treatment is 100° C. to 120° C. For example, the temperature of the grafting treatment can be 100° C., 105° C., 110° C., 115° C., 120° C. or any range thereof.

[0199] In some embodiments, the temperature of the ring-opening treatment is 60° C. to 80° C. For example, the temperature of the ring-opening treatment can be 60° C., 65° C., 70° C., 75° C., 80° C. or any range thereof.

[0200] In some embodiments, the mass ratio of the epoxy resin, the phenolic substance, the silicon-containing organic compound and / or the fluorine-containing organic compound to the amine substance is 10:(3-5):(2-7):(0.1-0.3). For example, the mass ratio of the epoxy resin, the phenolic substance, the silicon-containing organic compound and / or the fluorine-containing organic compound to the amine substance can be 10:4:2:0.2, 10:4:3:0.2, 10:4:4:0.2, 10:4:5:0.2, 10:4:6:0.2, 10:4:7:0.2 or within the range of any of the above values.

[0201] The mass ratio of the above four reactants is within the above range, and the corresponding reaction temperatures of the chain extension treatment, grafting treatment and ring opening treatment are used at the same time, so that the reaction of each step can be fully carried out, which is conducive to the acquisition of the modified epoxy described in the first aspect of the present application.

[0202] In a third aspect, the present application provides an insulating composition, which includes the modified epoxy resin described in the first aspect of the present application or the modified epoxy resin prepared according to the method described in the second aspect of the present application, and a curing agent.

[0203] The insulating composition provided in the present application includes a modified epoxy resin and a curing agent. When it is used in the preparation of an insulating coating for a battery casing, the curing agent reacts with the modified epoxy resin and cross-links and cures it into a modified epoxy resin polymer having a three-dimensional network structure. The three-dimensional network structure of the polymer is beneficial to improving the insulating pressure resistance, mechanical strength and bonding strength of the insulating coating to the battery casing substrate.

[0204] In some embodiments, the insulating composition further includes a protonic acid and an organic solvent.

[0205] In some embodiments, the protonic acid may include but is not limited to one or more of lactic acid, acetic acid and hydrochloric acid, and may be hydrochloric acid.

[0206] In some embodiments, the pH value of the insulating composition is 5.8 to 6.6. For example, the pH value of the insulating composition can be 5.8, 6, 6.2, 6.4, 6.6, or within a range consisting of any of the above values.

[0207] The pH value of the insulating composition is within the above range, which is conducive to the acidification (ionization) of the modified epoxy resin to make it positively charged. Therefore, when the insulating composition is used as a raw material for the electrophoretic preparation of a battery insulating coating, it is conducive to its deposition on the surface of the battery casing substrate serving as the negative electrode, thereby obtaining an insulating coating, and is conducive to improving the bonding strength between the insulating coating and the battery casing substrate.

[0208] In some embodiments, the organic solvent comprises an ether organic solvent.

[0209] In some embodiments, the ether organic solvent may include, but is not limited to, one or more of ethylene glycol butyl ether, ethylene glycol methyl ether, diethylene glycol butyl ether, and diethylene glycol ethyl ether.

[0210] The ether solvent selected in the present application has good hydrophilicity and can exist stably in the insulating composition.

[0211] In some embodiments, the molar ratio of the epoxy group in the modified epoxy resin to the curing agent is 1:(1-0.7). For example, the molar ratio of the epoxy group to the curing agent can be 1:1, 1:0.9, 1:0.8, 1:0.7 or within the range of any of the above values.

[0212] The molar ratio of the epoxy group to the curing agent in the modified epoxy resin is within the above range, which is conducive to a more complete reaction between the curing agent and the modified epoxy resin and a more complete cross-linking and curing of the modified epoxy resin, thereby improving the compactness of the three-dimensional network structure of the modified epoxy resin polymer, and further improving the insulation pressure resistance, mechanical strength and bonding strength of the insulating coating to the battery casing substrate.

[0213] In some embodiments, the curing agent includes a hydroxyl-terminated isocyanate.

[0214] In some embodiments, the hydroxyl-terminated isocyanate includes one or more of hydroxyl-fully blocked isocyanate and hydroxyl-half blocked isocyanate, and may be hydroxyl-fully blocked isocyanate.

[0215] In some embodiments, the hydroxyl fully blocked isocyanate may include, but is not limited to, one or more of hydroxyl fully blocked toluene diisocyanate (TDI), hydroxyl fully blocked isophorone diisocyanate (IPDI), hydroxyl fully blocked diphenylmethane diisocyanate (MDI), hydroxyl fully blocked dicyclohexylmethane diisocyanate (HMDI), hydroxyl fully blocked hexamethylene diisocyanate (HDI), and hydroxyl fully blocked lysine diisocyanate (LDI).

[0216] In this application, unless otherwise specified, hydroxyl-terminated isocyanate means that the isocyanate group of the isocyanate contains a hydroxyl group. Hydroxyl-fully-terminated isocyanate means that all isocyanate groups in the isocyanate contain a hydroxyl group; hydroxyl-half-terminated isocyanate means that part of the isocyanate groups (not less than 50%) in the isocyanate contain a hydroxyl group.

[0217] The modified epoxy resin has a large number of hydroxyl groups after the ring-opening treatment. The isocyanate in the curing agent is easy to react with the hydroxyl groups in the modified epoxy resin to form a cross-linked film, forming a modified epoxy resin polymer with a three-dimensional network structure. The present application uses hydroxyl-terminated isocyanate, which can avoid the failure of the insulating composition caused by the reaction of the modified epoxy resin with the curing agent at the insulating composition stage, that is, before the insulating composition is applied to the electrophoresis method preparation of the battery shell insulating coating.

[0218] In a fourth aspect, the present application provides a use of the insulating composition described in the third aspect of the present application in the preparation of a battery casing.

[0219] When the insulating composition is used in the preparation of a battery shell, the insulating pressure resistance, water resistance, and mechanical strength of the insulating coating of the battery shell, as well as the bonding strength between the insulating coating of the battery shell and the battery shell substrate can be improved.

[0220] In a fifth aspect, the present application provides a battery casing, comprising a casing substrate and an insulating coating disposed on at least a portion of the surface of the casing substrate, wherein the insulating coating comprises a modified epoxy resin polymer, and the raw materials for preparing the modified epoxy resin polymer include the insulating composition described in the third aspect of the present application.

[0221] The insulating composition is used as a raw material for preparing the modified epoxy resin polymer. When preparing the battery shell, its role is similar to the above, which will not be described in detail here.

[0222] In a sixth aspect, the present application provides a battery casing, comprising a casing substrate and an insulating coating provided on at least a portion of the surface of the casing substrate, wherein the insulating coating comprises a modified epoxy resin polymer, and the structural units of the modified epoxy resin polymer comprise: an epoxy resin main chain, ether-bonded straight-chain alkanes and / or ether-bonded straight-chain heteroalkanes connected to the carbon atoms of the epoxy resin main chain, silicon-containing side chains and / or fluorine-containing side chains connected to the carbon atoms of the epoxy resin main chain, a nitrogen-containing chain segment connected to the terminal epoxy carbon atom on the epoxy resin main chain, and an isocyanate-containing chain segment connected to the carbon atoms of the epoxy resin main chain by an ether bond.

[0223] An insulating coating is provided on the shell substrate of the battery shell. The modified epoxy resin polymer contained in the insulating coating has a dense three-dimensional network structure, which is beneficial to improving the insulation pressure resistance, mechanical strength and bonding strength of the insulating coating with the shell substrate.

[0224] In addition, in the structural unit of the modified epoxy resin polymer, the ether-bonded straight-chain alkane and / or ether-bonded straight-chain heteroalkane connected to the epoxy resin main chain can be used as a flexible segment to improve the flexibility of the modified epoxy resin polymer, thereby improving the toughness and bending resistance of the insulating coating; thus, in the process of battery processing, preparation and use, since the insulating coating has good toughness and bending resistance, it is not easy to break, and compared with conventional insulating films (such as PET blue films), it is conducive to further improving the insulating properties of the insulating coating, battery casing and battery. The silicon-containing side chain and / or fluorine-containing side chain connected to the epoxy resin main chain can be used as a hydrophobic segment to improve the wet heat aging resistance and water resistance of the insulating coating, thereby helping to improve the insulating properties and service life of the insulating coating and the battery casing.

[0225] In some embodiments, the modified epoxy resin polymer includes a structural unit represented by the following formula (7):

[0226]

[0227] In formula (7), R1 includes At least one of the following, where R 10 include n is an integer from 0 to 10; R 11 Including fluorinated segments, R 12 including one or more of a hydrogen atom, a C1-C5 alkyl group and a carboxyl group,

[0228] Optionally, the fluorine-containing segment comprises fluorine atoms and One or more of;

[0229] R2 includes Among them, R 20 and R 21 Each independently comprises one or more of a hydrogen atom, an alkyl group, a cycloalkyl group, an epoxy group, an aryl group, a heteroaryl group, a heteroalkyl group, a heterocyclic group, an amino group, an alkylene group, a halogen group, a hydroxyl group, an alkylamino group and an arylalkyl group;

[0230] R3 includes

[0231] R4 includes

[0232] Each independently represents C1 to C 100 One or more of the chain alkanes and chain heteroalkanes, * represents the connection site.

[0233] The modified epoxy resin polymer includes a structural unit shown in formula (7), in which the R3 segment located on the main chain has a certain bending ability and softness due to the ether bond that allows the molecular chain to rotate and swing freely to a certain extent, so it can be used as a flexible segment to improve the flexibility of the modified epoxy resin polymer, thereby improving the toughness and bending resistance of the insulating coating, and further improving the insulating properties of the insulating coating, battery casing and battery. The R1 segment located on the side chain has a lower polarity, so it can be used as a hydrophobic segment to improve the wet heat aging resistance and water resistance of the insulating coating, thereby improving the insulating properties and service life of the insulating coating and battery casing. In addition, the R2 segment located at the end of the main chain is easy to ionize under acidic conditions to make the modified epoxy resin positively charged, so it can be used for the subsequent preparation of insulating coatings by electrophoresis; it can also play a chain extension effect, improving the flexibility of the segment and the insulating properties of the coating.

[0234] In some embodiments, the weight average molecular weight of the modified epoxy resin polymer is 1000 to 4000. For example, the weight average molecular weight of the modified epoxy resin polymer can be 1000, 1600, 2200, 2800, 3400, 4000 or any range thereof.

[0235] The weight average molecular weight of the modified epoxy resin polymer is well known in the art and can be tested by methods known in the art. For example, a Waters 2695Isocratic HPLC gel chromatograph (differential refractive index detector 2141) is used, a polystyrene solution sample with a mass fraction of 3.0% is used as a reference, and a matching chromatographic column (oily: Styragel HT5DMF7.8×300mm+Styragel HT4) is selected. A 3.0% modified epoxy resin polymer solution is prepared with purified N-methylpyrrolidone (NMP) solvent, and the prepared solution is allowed to stand for one day for use. During the test, tetrahydrofuran is first drawn with a syringe, rinsed, and repeated several times. Then 5 ml of the experimental solution is drawn, the air in the syringe is removed, and the needle tip is wiped dry. Finally, the sample solution is slowly injected into the injection port. After the indication is stable, the data is obtained and the weight average molecular weight is read.

[0236] The weight average molecular weight of the modified epoxy resin polymer is within the above range, which is beneficial to improving the viscosity and surface energy of the polymer, thereby improving the bonding strength between the insulating coating and the shell substrate, and the water resistance of the insulating coating.

[0237] In some embodiments, the degree of polymerization of the modified epoxy resin polymer is 1 to 10. For example, the degree of polymerization of the modified epoxy resin polymer can be 1, 3, 5, 7, 9, 10 or any range thereof.

[0238] The degree of polymerization of the modified epoxy resin polymer is well known in the art and can be tested by methods known in the art, for example, by NMR (nuclear magnetic resonance) method.

[0239] When the structural units shown in formula (7) constitute the molecular chain of the polymer, the symmetry of the molecular chain is relatively high and the crystallization performance of the polymer is relatively good, which can contribute to the adhesion performance of the polymer; therefore, when the number of structural units shown in formula (7), that is, the degree of polymerization of the modified epoxy resin polymer is within the above range, the polymer can have a higher adhesion, thereby making the insulating coating have a higher adhesion.

[0240] In some embodiments, the viscosity of the modified epoxy resin polymer is 10000 to 25000. For example, the viscosity of the modified epoxy resin polymer can be 10000, 13000, 16000, 19000, 22000, 25000 or any range thereof.

[0241] It should be noted that the viscosity of the modified epoxy digital polymer refers to its viscosity at a temperature of 120°C.

[0242] The viscosity of the modified epoxy resin polymer is well known in the art and can be tested by methods known in the art. For example, a rotary viscometer can be used to measure the viscosity of the modified epoxy resin polymer. Select a suitable rotor, fix the viscometer rotor, place the ether solution of the modified epoxy resin polymer at a temperature of 120°C under the viscometer rotor, and the solution just submerges the scale line of the rotor. Instrument model: Shanghai Fangrui NDJ-5S, rotor: 63# (2000-10000mPa.s), 64# (10000-50000mPa.s), rotation speed: 12 rpm, test temperature: 25°C, test time is 5 minutes, and read the data after the display is stable.

[0243] The viscosity of the modified epoxy resin polymer is within the above range, which can make the insulating coating have higher adhesion and prevent the insulating coating from falling off during the use of the battery, thereby ensuring that the battery shell has good insulation during long-term use.

[0244] In some embodiments, the thickness of the insulating coating is 20 μm to 70 μm, and can be 40 μm to 50 μm. For example, the thickness of the insulating coating can be 20 μm, 40 μm, 60 μm, 70 μm, or any range thereof.

[0245] The thickness of the insulating coating is well known in the art and can be measured by methods known in the art, for example, by using a micrometer.

[0246] The thickness of the insulating coating is within the above range, which ensures the insulation performance of the battery shell while not affecting the performance of the battery cell itself (such as capacity, cycle performance, etc.).

[0247] In some embodiments, the breakdown voltage of the insulating coating is 500V to 8000V. For example, the breakdown voltage of the insulating coating may be 500V, 1000V, 2000V, 3000V, 4000V, 5000V, 6000V, 7000V, 8000V, or any range thereof. Optionally, it is 2700V to 7500V.

[0248] The breakdown voltage of the insulating coating is well known in the art and can be tested by methods known in the art, for example, by a withstand voltage test method (insulation withstand voltage tester).

[0249] The breakdown voltage of the insulating coating within the above range is caused by the modified epoxy resin polymer. The breakdown voltage within the above range can meet the voltage resistance requirements of the battery shell during use, so that the battery shell has a higher insulation voltage resistance performance during long-term use.

[0250] In a seventh aspect, the present application provides a method for preparing the battery casing according to the sixth aspect of the present application, which may include the following steps:

[0251] S10', performing electrophoresis treatment on the shell substrate using an electrophoresis solution containing the insulating composition to form a deposition layer on at least a portion of the surface of the shell substrate;

[0252] S20', curing the shell substrate covered with the deposition layer to form the insulating coating to obtain the battery shell.

[0253] It can be understood that the electrophoresis treatment described above uses the shell substrate as the cathode, and allows the acidified, positively charged modified epoxy resin to react with the alkaline substances generated by ionization on the cathode, thereby achieving the deposition of the modified epoxy resin on the surface of the shell substrate. Furthermore, under the action of the electric field, the positively charged modified epoxy resin ions of the electrophoresis liquid move to the cathode of the shell substrate, and react with the alkaline substances generated by ionization on the cathode surface to form insoluble substances, which are deposited on the surface of the shell substrate; after the curing treatment, the modified epoxy resin can be cross-linked and cured to form a modified epoxy resin polymer with a three-dimensional network structure, thereby forming an insulating coating.

[0254] Compared with the existing method of directly coating insulating materials on the battery casing substrate, the method provided in the present application can improve the bonding strength (binding force) between the insulating coating and the casing substrate, and its curing temperature is low and the energy consumption is low, which is conducive to large-scale production.

[0255] In some embodiments, the voltage of the electrophoresis treatment is 200 V to 250 V. For example, the voltage of the electrophoresis treatment can be 200 V, 210 V, 220 V, 230 V, 240 V, 250 V or any range thereof.

[0256] The voltage of the electrophoresis treatment is within the above range, which is conducive to the deposition of the positively charged modified epoxy resin on the surface of the shell substrate and achieves a certain film thickness.

[0257] In some embodiments, the curing temperature is 150° C. to 190° C. The curing temperature may be 150° C., 160° C., 170° C., 180° C., 190° C. or any range thereof.

[0258] The curing temperature is within the above range, which can unblock the hydroxyl groups in the hydroxyl-terminated isocyanate curing agent, thereby achieving and promoting the cross-linking curing reaction between the modified epoxy resin and the curing agent.

[0259] In addition, the secondary battery, battery module, battery pack, and electric device of the present application will be described below with reference to the drawings as appropriate.

[0260] In one embodiment of the present application, a secondary battery is provided.

[0261] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0262] [Positive electrode]

[0263] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.

[0264] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0265] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0266] In some embodiments, the positive electrode active material may adopt a positive electrode active material for a battery that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05O2) and its modified compounds, etc. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0267] It should be noted that the battery will be accompanied by Li deintercalation and consumption during the charge and discharge process, and the molar content of Li is different when the battery is discharged to different states. In the list of positive electrode active materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system, and the molar content of Li will change after charge and discharge cycles.

[0268] In the list of positive electrode active materials in the present application, the molar content of O is only a theoretical value. The release of oxygen from the lattice will cause the molar content of O to change, and the actual molar content of O will fluctuate.

[0269] In some embodiments, the positive electrode active material may also include at least one of the following materials: sodium transition metal oxide, polyanionic compound and Prussian blue compound. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.

[0270] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. The sodium transition metal oxide is, for example, Na x MO2, wherein M includes one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0<x≤1.

[0271] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. Transition metals include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y includes at least one of P, S and Si; n represents (YO4) n- valence state.

[0272] Polyanionic compounds can also be those with sodium ions, transition metal ions, tetrahedral (YO4) n-A class of compounds containing anion units and halogen anions. The transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y includes at least one of P, S and Si, and n represents (YO4) n- valence state; the halogen includes at least one of F, Cl and Br.

[0273] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n- Anion unit, polyhedral unit (ZO y ) m+ and an optional halogen anion. Y includes at least one of P, S and Si, and n represents (YO4) n- valence state; Z represents a transition metal, including at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; m represents (ZO y ) m+ valence state; the halogen includes at least one of F, Cl and Br.

[0274] Polyanionic compounds include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2 (P2O7), NaM'PO4F (M' includes one or more of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0275] Prussian blue compounds can be sodium ions, transition metal ions and cyanide ions (CN - ). The transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Prussian blue compounds are, for example, Na a Me b Me' c (CN)6, wherein Me and Me' each independently include at least one of Ni, Cu, Fe, Mn, Co and Zn, 0<a≤2, 0<b<1, 0<c<1.

[0276] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0277] In some embodiments, the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0278] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0279] The positive electrode sheet of the present application does not exclude other additional functional layers in addition to the positive electrode film layer. For example, in some embodiments, the positive electrode sheet of the present application also includes a conductive primer layer (for example, composed of a conductive agent and a binder) sandwiched between the positive electrode collector and the positive electrode film layer and disposed on the surface of the positive electrode collector. In other embodiments, the positive electrode sheet of the present application also includes a protective layer covering the surface of the positive electrode film layer.

[0280] [Negative electrode]

[0281] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0282] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0283] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0284] In some embodiments, the negative electrode active material may adopt the negative electrode active material for the battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0285] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0286] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0287] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0288] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0289] The negative electrode plate of the present application does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate of the present application also includes a conductive primer layer (for example, composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In some other embodiments, the negative electrode plate of the present application also includes a protective layer covering the surface of the negative electrode film layer.

[0290] [Electrolytes]

[0291] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0292] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0293] In some embodiments, the electrolyte salt may be a lithium salt. As an example, the lithium salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorobis(oxalatophosphate), and lithium tetrafluorooxalatophosphate.

[0294] In some embodiments, the electrolyte salt may also be a sodium salt. As an example, the sodium salt includes but is not limited to at least one of NaPF6, NaClO4, NaBCl4, NaSO3CF3 and Na(CH3)C6H4SO3. The above sodium salts may be used alone or in combination of two or more.

[0295] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0296] In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0297] [Isolation film]

[0298] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0299] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0300] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0301] In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0302] In some embodiments, the outer packaging of the secondary battery may be the battery casing described in the fifth aspect or the sixth aspect of the present application.

[0303] In some embodiments, the outer packaging of the secondary battery may also be other hard shells, such as hard plastic shells, aluminum shells, steel shells, etc. The outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0304] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square or any other shape. Figure 1 The battery cell 5 is a square structure as an example.

[0305] In some embodiments, reference Figure 2 , the outer packaging may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0306] In some embodiments, the secondary battery may also be a battery module composed of a plurality of battery cells. The battery module may contain a plurality of battery cells, and the specific number may be adjusted by those skilled in the art according to the application and capacity of the battery module.

[0307] Figure 3 4 is an example of a battery module. Figure 3 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0308] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0309] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0310] In some embodiments, the battery cells mentioned above may also be directly assembled into a battery pack, and the number of battery cells contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0311] Figure 4 and Figure 5 1 is a battery pack 1 as an example. Figure 4 and Figure 5 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0312] In addition, the present application also provides an electric device, which includes a secondary battery provided in the present application. The secondary battery can be used as a power source for the electric device, or as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0313] As the electrical device, a secondary battery can be selected according to its usage requirements.

[0314] Figure 6 The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the high power and high energy density requirements of the power consumption device for the secondary battery, a battery pack or a battery module can be used.

[0315] Another example of a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.

[0316] Example

[0317] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0318] Example 1

[0319] Preparation of modified epoxy resin

[0320] In a 1000mL four-necked round-bottom flask equipped with a condenser reflux tube, a stirrer, a constant pressure funnel, and an oil bath temperature control and heating device, add 500mL of organic solvent ethylene glycol butyl ether, 1g of catalyst dibutyltin dilaurate, 100g of bisphenol A type epoxy resin, and 35g of bisphenol A (try to ensure that the mass ratio of epoxy resin to phenol is within the range of 10:(3-5)), stir and heat to 135°C, and keep stirring for 180min.

[0321] Then add 25 g of vinyl polydimethylsiloxane (try to ensure that the mass ratio of epoxy resin, phenol and siloxane is within the range of 10:(3-5):(2-7)), stir and heat to 110°C, and keep stirring for 120 minutes.

[0322] Finally, add 2 g of diethylamine (try to ensure that the mass ratio of epoxy resin, phenol, siloxane and amine is within the range of 10:(3-5):(2-7):(0.1-0.3)), stir and heat to 70°C, keep stirring for 120 minutes to obtain a modified epoxy resin.

[0323] Preparation of insulating composition

[0324] The modified epoxy resin and curing agent hydroxyl fully blocked toluene diisocyanate were dissolved in 100 mL of organic solvent ethylene glycol butyl ether, wherein the molar ratio of epoxy groups in the modified epoxy resin to hydroxyl fully blocked toluene diisocyanate was 1:1; and then hydrochloric acid was added to adjust the pH of the solution to 5.8 to obtain an insulating composition.

[0325] Preparation of battery casing

[0326] (1) Preparation of electrophoresis solution

[0327] Take 150 g of the above insulating composition, add 850 mL of deionized water thereto, stir with a shear emulsifier for 3 hours, filter with an 800-mesh punching frame sieve, and stir with an electromagnetic stirrer for 24 hours to obtain an electrophoresis solution.

[0328] (2) Preparation of insulating coating

[0329] The electrophoresis liquid was placed in the electrophoresis tank, the working voltage was adjusted to 230 V, the treated shell substrate was connected to the cathode, taken out after 3 minutes of electrophoresis, and cleaned with deionized water to obtain a shell substrate covered with a deposition layer; then the substrate was gradually heated to 170° C. and kept warm for 30 minutes to form an insulating coating of about 40 μm on the surface of the battery shell substrate to obtain a battery shell.

[0330] Preparation of positive electrode

[0331] The positive electrode active material, conductive carbon black SP and binder PVDF prepared in Example 1 were dispersed in a solvent NMP at a weight ratio of 98:1:1 and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry was evenly coated on a positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained, and the coating amount per unit area was 0.27 g / 1540.25 mm 2 .

[0332] Preparation of negative electrode

[0333] The negative electrode active material graphite, thickener sodium carboxymethyl cellulose, adhesive styrene butadiene rubber, and conductive agent acetylene black are mixed in a mass ratio of 97:1:1:1, and deionized water is added to obtain a negative electrode slurry under the action of a vacuum mixer; the negative electrode slurry is evenly coated on a copper foil; the copper foil is dried at room temperature and then transferred to a 120°C oven for drying for 1 hour, and then supercooled and cut to obtain a negative electrode sheet, and the coating amount per unit area is 0.17g / 1540.25mm 2 .

[0334] Preparation of isolation membrane

[0335] A 12μm thick polypropylene isolation film was selected.

[0336] Preparation of electrolyte

[0337] The organic solvent is a mixed solution containing ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC and DEC is 20:20:60. In an argon atmosphere glove box with a water content of <10ppm, fully dried lithium salt LiPF6 is dissolved in the organic solvent and mixed evenly to obtain an electrolyte. The concentration of the lithium salt is 1 mol / L.

[0338] Preparation of batteries

[0339] The positive electrode sheet, isolation film, and negative electrode sheet are stacked in order, so that the isolation film is placed between the positive and negative electrode sheets to play an isolating role, and then wound into a square bare battery cell, loaded into the battery casing mentioned above in this application, and then baked at 80°C to remove water, 10g of the corresponding non-aqueous electrolyte is injected, and the mouth is sealed. After standing, hot and cold pressing, formation, clamping, capacity division and other processes, a finished battery with a capacity of 4000mAh is obtained.

[0340] Embodiments 2 to 30

[0341] The preparation methods of the modified epoxy resin, insulating composition, insulating coating, battery casing and battery are similar to those in Example 1, except that the relevant parameters in the preparation process are adjusted, and the specific parameters are shown in Table 1 below. Wherein, " / " indicates that the corresponding parameter does not exist.

[0342] Embodiment 31

[0343] The preparation methods of the modified epoxy resin, insulating composition, insulating coating, battery casing and battery are similar to those in Example 1, except that: when preparing the insulating coating, coating is used instead of electrophoresis, that is, the electrophoresis liquid is coated on the casing substrate.

[0344] Comparative Example 1

[0345] Similar to Example 1, the difference is that when preparing the battery shell, a PET blue film of the same thickness is used to replace the insulating coating in Example 1.

[0346] Comparative Example 2

[0347] Similar to Example 1, the difference is that the epoxy resin is not modified, that is, an equal mass of bisphenol A epoxy resin is used to replace the modified epoxy resin in Example 1 to prepare the insulating composition and the insulating coating.

[0348] The relevant parameters of the modified epoxy resin, insulating composition, insulating coating and battery casing of the above-mentioned Examples 1 to 31 and Comparative Examples 1 to 2 are shown in the following Table 1.

[0349] Table 1

[0350]

[0351]

[0352]

[0353]

[0354] In addition, the insulating coatings and battery casings of Examples 1 to 31 and Comparative Examples 1 to 2 were subjected to performance tests. The test results are shown in Table 2 below.

[0355] Test Section

[0356] (1) Insulation withstand voltage

[0357] Set the voltage to DC 0~8000V, test time to 60s, repeat 25 times, and satisfy the leakage current ≤0.1mA.

[0358] (2) Toughness

[0359] According to GB / T 1732 (≥5J), under 1 or 4 times magnifying glass, there shall be no defects such as paint exposure and cracks; and the above insulation withstand voltage requirements shall be met.

[0360] (3) Bending resistance

[0361] According to GB / T 6742-86, the shafts with different curvature radii are bent 180° to meet the following requirements: ① the paint film does not fall off and has no cracks; ② the adhesion meets level 0 to 1; ③ the above insulation withstand voltage requirements are met.

[0362] (4) Adhesion

[0363] According to GBT 7124, the coating @ structural adhesive @ coating test sample was prepared, the test temperature was 25°C, the tensile speed was 5mm / min, and the adhesive layer thickness was 0.2mm.

[0364] (5) Resistance to moisture and heat aging

[0365] 85℃85%RH humidity and heat aging box for 1000h, test the bonding strength, insulation withstand voltage performance and adhesion.

[0366] (6) Water resistance

[0367] Soak in water at 65℃ for 1000h, test adhesion and insulation withstand voltage performance.

[0368] (7) Adhesion

[0369] ISO 2409 100-grid test.

[0370] Table 2

[0371]

[0372]

[0373] In Table 2 above, by comparing the embodiment with comparative example 1, it can be seen that compared with the conventional PET blue film, the insulation properties of the insulating coating and the battery casing provided by the present application are significantly improved; in addition, the bending resistance, adhesion, resistance to moisture and heat aging, water resistance and adhesion of the insulating coating are also significantly improved.

[0374] By comparing the embodiment with comparative example 2, it can be seen that compared with the unmodified epoxy resin, the insulating coating prepared by the modified epoxy resin in the present application has significantly higher insulation, resistance to moisture and heat aging and water resistance, indicating that the modified epoxy resin is beneficial to improving the above-mentioned properties of the insulating coating.

[0375] By comparing Example 31 with Example 1, it can be seen that after the insulating coating is prepared by conventional coating method instead of electrophoresis method, the insulation and adhesion of the insulating coating are significantly reduced, indicating that the electrophoresis method provided in this application is superior to the conventional coating method.

[0376] Comparing Example 20 with Example 1, it can be seen that the performance of the insulating coating prepared using the uncapped curing agent in Example 20 is significantly lower than that in Example 1, indicating that whether the curing agent is capped has a great influence on the preparation process of the insulating coating.

[0377] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A modified epoxy resin, characterized in that: include: Epoxy resin backbone; and Ether bond-containing straight-chain alkanes and / or ether bond-containing straight-chain heteroalkanes connected to the carbon atoms of the epoxy resin main chain, silicon-containing side chains and / or fluorine-containing side chains connected to the carbon atoms of the epoxy resin main chain, and nitrogen-containing segments connected to the terminal epoxy carbon atoms on the epoxy resin main chain.

2. The modified epoxy resin according to claim 1, characterized in that Satisfy at least one of the following conditions: (1a) The epoxy resin main chain comprises the structural formula shown in the following formula (1): (1b) The ether bond-containing straight-chain alkane and / or ether bond-containing straight-chain heteroalkane includes a structural formula as shown in the following formula (2): (1c) The silicon-containing side chain comprises a structural formula as shown in the following formula (3), and the fluorine-containing side chain comprises a structural formula as shown in the following formula (4): In formula (3), R 10 include n is an integer from 0 to 10; In formula (4), R 11 Including fluorinated segments, R 12 including one or more of a hydrogen atom, a C1-C5 alkyl group and a carboxyl group, Optionally, the fluorine-containing segment includes fluorine atoms, One or more of; (1d) The nitrogen-containing segment comprises the structural formula shown in the following formula (5): In formula (5), R 20 and R 21 Each independently comprises one or more of a hydrogen atom, an alkyl group, a cycloalkyl group, an epoxy group, an aryl group, a heteroaryl group, a heteroalkyl group, a heterocyclic group, an amino group, an alkylene group, a halogen group, a hydroxyl group, an alkylamino group and an arylalkyl group; In the above formulas (1) to (5), Each independently represents C1 to C 100 One or more of the chain alkanes and chain heteroalkanes, * represents the connection site.

3. The modified epoxy resin according to claim 1, characterized in that Including the structural formula shown in the following formula (6): In formula (6), R1 includes At least one of the following, where R 10 include n is an integer from 0 to 10; R 11 Including fluorinated segments, R 12 including one or more of a hydrogen atom, a C1-C5 alkyl group and a carboxyl group, Optionally, the fluorine-containing segment includes fluorine atoms, One or more of; R2 includes Among them, R 20 and R 21 Each independently comprises one or more of a hydrogen atom, an alkyl group, a cycloalkyl group, an epoxy group, an aryl group, a heteroaryl group, a heteroalkyl group, a heterocyclic group, an amino group, an alkylene group, a halogen group, a hydroxyl group, an alkylamino group and an arylalkyl group; R3 includes Each independently represents C1 to C 100 One or more of the chain alkanes and chain heteroalkanes, * represents the connection site.

4. The modified epoxy resin according to any one of claims 1 to 3, characterized in that: The epoxy equivalent of the modified epoxy resin is 500-2000, and can be optionally 800-1200.

5. A method for preparing the modified epoxy resin according to any one of claims 1 to 4, characterized in that: include: Utilizing phenolic substances to carry out chain extension treatment on epoxy resin to obtain chain extension reactants; Performing a grafting treatment on the chain extension reactant using a silicon-containing organic compound and / or a fluorine-containing organic compound to obtain a grafted reactant; The grafting reactant is subjected to ring-opening treatment by using an amine substance to obtain the modified epoxy resin.

6. The method according to claim 5, characterized in that Satisfy at least one of the following conditions: (2a) The epoxy resin includes one or more of glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, linear aliphatic epoxy resin and alicyclic epoxy resin, It can be selected from one or both of bisphenol A epoxy resin and bisphenol F epoxy resin; (2b) the phenolic substance comprises one or more of phenol and alkylphenol, Optionally, the phenolic substance includes one or more of butylphenol, pentylphenol, heptylphenol, octylphenol, nonylphenol, decylphenol, 2,2-bis(4-hydroxyphenyl)propane, 4,4-dihydroxydiphenylmethane and dodecylphenol; (2c) the silicon-containing organic compound includes polydimethylsiloxane, and the fluorine-containing organic compound includes fluorine acrylic acid; Optionally, the polydimethylsiloxane includes one or both of vinyl polydimethylsiloxane and amino polydimethylsiloxane, and may further be vinyl polydimethylsiloxane; Optionally, the fluorine-containing acrylic acid includes one or more of 2-fluoroacrylic acid, hexafluorobutyl acrylate and hexafluorobutyl methacrylate, and may further be 2-fluoroacrylic acid; (2d) The amine substance includes one or more of methylamine, aniline, diethylamine, ethylenediamine, diisopropylamine, diethanolamine, triethanolamine and tetrabutylammonium bromide, and diethylamine can be selected.

7. The method according to claim 5 or 6, characterized in that: Satisfy at least one of the following conditions: (3a) The temperature of the chain extension treatment is 120°C to 150°C; (3b) The temperature of the grafting treatment is 100° C. to 120° C.; (3c) The temperature of the ring-opening treatment is 60° C. to 80° C.; (3d) The mass ratio of the epoxy resin, the phenolic substance, the silicon-containing organic matter and / or the fluorine-containing organic matter to the amine substance is 10:(3-5):(2-7):(0.1-0.3).

8. An insulating composition, characterized in that: The invention comprises the modified epoxy resin according to any one of claims 1 to 4 or the modified epoxy resin prepared by the method according to any one of claims 5 to 7, and a curing agent.

9. The insulating composition according to claim 8, characterized in that Also includes protonic acid and organic solvent, Optionally, the protonic acid includes one or more of lactic acid, acetic acid and hydrochloric acid, and may further be hydrochloric acid; Optionally, the organic solvent includes an ether organic solvent; Further optionally, the ether organic solvent includes one or more of ethylene glycol butyl ether, ethylene glycol methyl ether, diethylene glycol butyl ether and diethylene glycol ethyl ether.

10. The insulating composition according to claim 8 or 9, characterized in that: Satisfy at least one of the following conditions: (1) The molar ratio of the epoxy group in the modified epoxy resin to the curing agent is 1:(1-0.7); (2) The curing agent includes a hydroxyl-terminated isocyanate, which may be one or more of a hydroxyl-fully blocked isocyanate and a hydroxyl-half-blocked isocyanate, and may further be a hydroxyl-fully blocked isocyanate; (3) The pH value of the insulating composition is 5.8 to 6.

6.

11. Use of the insulating composition according to any one of claims 8 to 10 in preparing a battery casing.

12. A battery casing, characterized in that: include: Shell substrate; and An insulating coating is provided on at least part of the surface of the housing substrate, wherein the insulating coating comprises a modified epoxy resin polymer, and the raw material for preparing the modified epoxy resin polymer comprises the insulating composition according to any one of claims 8-10.

13. A battery casing, characterized in that: include: Shell substrate; and An insulating coating is provided on at least part of the surface of the housing substrate, wherein the insulating coating comprises a modified epoxy resin polymer, and the structural unit of the modified epoxy resin polymer comprises: Ether bond-containing straight-chain alkanes and / or ether bond-containing straight-chain heteroalkanes connected to the carbon atoms of the epoxy resin main chain, silicon-containing side chains and / or fluorine-containing side chains connected to the carbon atoms of the epoxy resin main chain, nitrogen-containing segments connected to the terminal epoxy carbon atoms on the epoxy resin main chain, and isocyanate-containing segments connected to the carbon atoms of the epoxy resin main chain by ether bonds.

14. The battery housing according to claim 12 or 13, characterized in that: The modified epoxy resin polymer comprises a structural unit as shown in the following formula (7): In formula (7), R1 includes At least one of the following, where R 10 include n is an integer from 0 to 10; R 11 Including fluorinated segments, R 12 including one or more of a hydrogen atom, a C1-C5 alkyl group and a carboxyl group, Optionally, the fluorine-containing segment includes fluorine atoms, One or more of; R2 includes Among them, R 20 and R 21 Each independently comprises one or more of a hydrogen atom, an alkyl group, a cycloalkyl group, an epoxy group, an aryl group, a heteroaryl group, a heteroalkyl group, a heterocyclic group, an amino group, an alkylene group, a halogen group, a hydroxyl group, an alkylamino group and an arylalkyl group; R3 includes R4 includes Each independently represents C1 to C 100 One or more of the chain alkanes and chain heteroalkanes, * represents the connection site.

15. The battery housing according to claim 12 or 13, characterized in that: Satisfy at least one of the following conditions: (1) The weight average molecular weight of the modified epoxy resin polymer is 1000 to 4000; (2) The degree of polymerization of the modified epoxy resin polymer is 1 to 10; (3) The viscosity of the modified epoxy resin polymer at a temperature of 120° C. is 10,000 to 25,000.

16. The battery housing according to claim 12 or 13, characterized in that: Satisfy at least one of the following conditions: (1) The thickness of the insulating coating is 20 μm to 70 μm, and can be 40 μm to 50 μm; (2) The breakdown voltage of the insulating coating is 500V to 8000V, and can be optionally 2700V to 7500V.

17. A method for preparing the battery casing according to claim 12, characterized in that: include: Performing electrophoresis treatment on the shell substrate using the insulating composition as an electrophoretic liquid to form a deposition layer on at least a portion of the surface of the shell substrate; The outer shell substrate covered with the deposition layer is cured to form the insulating coating to obtain the battery outer shell.

18. The battery housing according to claim 17, characterized in that: Satisfy at least one of the following conditions: (1) The voltage of the electrophoresis treatment is 200V to 250V, Optionally, the temperature of the electrophoresis treatment is 29°C to 35°C; (2) The curing temperature is 150°C to 190°C.

19. A secondary battery, characterized in that: A battery shell comprising the battery shell according to any one of claims 12 to 16 or a battery shell made according to the method of claim 17 or 18.

20. An electrical device, characterized in that: Includes the secondary battery as claimed in claim 19.

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