Modified epoxy resin, method for producing the same, insulating composition, method for producing battery case, battery case, secondary battery, and electric device

Abstract

The application provides a 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; ether bond-containing straight-chain alkanes and / or ether bond-containing straight-chain heteroalkanes connected to carbon atoms of the epoxy resin main chain, silicon-containing branched chains and / or fluorine-containing branched chains connected to the carbon atoms of the epoxy resin main chain, and nitrogen-containing chain segments connected to terminal epoxy group carbon atoms on the epoxy resin main chain. The modified epoxy resin provided by the application can improve the insulation performance of the battery shell when applied to the preparation of the battery shell, and further improve the insulation performance of the secondary battery.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, and in particular to a modified epoxy resin and its preparation method, an insulating composition and its application, a battery casing and its preparation method, a secondary battery, and an electrical device. Background Technology

[0002] Rechargeable batteries, represented by lithium-ion batteries, are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools due to their high capacity and long lifespan. As the application range of batteries expands, the performance requirements for rechargeable batteries are becoming increasingly stringent. In existing rechargeable batteries, the adhesion strength between the battery cell and the insulating layer surrounding the cell is not high, making it prone to insulation layer detachment during use, thus affecting the insulation performance of the rechargeable battery. Summary of the Invention

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

[0004] To achieve the above objectives, a first aspect of this application provides a modified epoxy resin, comprising:

[0005] Epoxy resin backbone; and

[0006] The epoxy resin main chain includes ether-bonded straight-chain alkanes and / or ether-bonded straight-chain heteroalkanes connected to carbon atoms of the epoxy resin main chain, silicon-containing branches and / or fluorine-containing branches connected to carbon atoms of the epoxy resin main chain, and nitrogen-containing segments connected to carbon atoms of terminal epoxy groups on the epoxy resin main chain.

[0007] The modified epoxy resin provided in this application modifies the epoxy resin matrix. When this modified epoxy resin is applied to the preparation of the insulating coating for secondary battery casings, the ether-containing straight-chain alkanes and / or ether-containing straight-chain heteroalkanes located on the main chain in its structural formula can act as flexible segments to improve the flexibility of the modified epoxy resin, thereby enhancing the toughness and bending resistance of the insulating coating. Meanwhile, the silicon-containing and / or fluorine-containing branches located on the modified epoxy resin structure can act as hydrophobic segments to improve the resistance to damp heat aging and water resistance of the insulating coating. Therefore, this is beneficial for improving the insulation performance and service life of both the insulating coating and the battery casing.

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

[0009] (1a) The epoxy resin backbone includes the structural formula shown in formula (1):

[0010]

[0011] (1b) The ether-containing straight-chain alkanes and / or ether-containing straight-chain heteroalkanes include the structural formula shown in formula (2) below:

[0012]

[0013] (1c) The silicon-containing branch includes the structure shown in formula (3) below, and the fluorine-containing branch includes the structure shown in formula (4) below:

[0014]

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

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

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

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

[0019]

[0020] In equation (5), R 20 and R 21 Each independently includes one or more of the following: hydrogen atom, alkyl, cycloalkyl, epoxy group, aryl, heteroaryl, heteroalkyl, heterocyclic, amino, alkylene, halogen, hydroxyl, alkylamino and arylalkyl;

[0021] In the above equations (1) to (5), Each of them independently represents C1 to C2. 100 One or more of the alkanes and heteroalkanes, * indicates a linking site.

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

[0023] The ether-containing straight-chain alkanes and / or ether-containing straight-chain heteroalkanes located on the main chain in formula (2) can serve as flexible segments to improve the toughness and bending resistance of the insulating coating, thereby improving the insulation performance of the insulating coating, battery casing and battery.

[0024] In formula (3), the silicon-containing side chains located on the side chains can be used as hydrophobic segments to improve the resistance to humid heat aging and water resistance of the insulating coating, thereby improving the insulation performance and service life of the insulating coating and the battery shell.

[0025] The fluorinated side chains in formula (4) can be used as hydrophobic segments to improve the resistance to humid heat aging and water resistance of the insulating coating, thereby improving the insulation performance and service life of the insulating coating and battery casing.

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

[0027]

[0028] In equation (6), R1 includes At least one of them, wherein R 10 include n is an integer from 0 to 10; R 11 Including fluorinated segments, R 12 Includes one or more of hydrogen atoms, C1-C5 alkyl groups, and carboxyl groups.

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

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

[0031] R3 includes

[0032] Each of them independently represents C1 to C2. 100 One or more of the alkanes and heteroalkanes, * indicates a linking site.

[0033] When the modified epoxy resin in formula (6) is used to prepare the insulating coating for a secondary battery casing, the R3 segment located on the main chain can act 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 thus improving the insulation performance of the insulating coating, the battery casing, and the battery. The R1 segment located on the side chain, due to its lower polarity, can act as a hydrophobic segment to improve the resistance to damp heat aging and water resistance of the insulating coating, thereby improving the insulation performance and service life of the insulating coating and the battery casing. Furthermore, the R2 segment located at the end of the main chain can improve the flexibility of the chain segment and the insulation performance of the coating.

[0034] In some embodiments of this application, the epoxy equivalent of the modified epoxy resin is 500 to 2000, and can be selected as 800 to 1200.

[0035] The epoxy equivalent of the modified epoxy is within the above range. When it is used in the electrophoretic preparation of insulating coatings, 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] A second aspect of this application provides a method for preparing the modified epoxy resin described in the first aspect of this application, comprising:

[0037] Chain extension treatment of epoxy resin using phenolic substances was used to obtain chain extension reactants;

[0038] The chain extender reactant is grafted onto a silicon-containing organic compound and / or a fluorine-containing organic compound to obtain a grafted reactant.

[0039] The modified epoxy resin is obtained by ring-opening treatment of the grafted reactants using amines.

[0040] In the above method, by using phenolic substances to extend the chain of epoxy resin, the segments contained in the phenolic substances can be added to the epoxy resin backbone, thereby lengthening the epoxy resin backbone. By using silicon-containing organic compounds and / or fluorine-containing organic compounds to graft the chain extension reactants, the silicon-containing and / or fluorine-containing segments of the silicon-containing organic compounds and / or fluorine-containing organic compounds can be grafted onto the epoxy resin backbone, giving the resin resistance to damp heat. By using amine substances to perform ring-opening treatment on the grafted reactants, some of the epoxy groups contained in the epoxy resin can be ring-opened, generating a certain number of hydroxyl groups. When the modified epoxy resin is subsequently applied to 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 this 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] It can be selected as one or both of bisphenol A type epoxy resin and bisphenol F type epoxy resin;

[0044] (2b) The phenolic substances include one or more of phenol and alkylphenols.

[0045] Optionally, the phenolic substances include one or more of bisphenol A, bisphenol F, butylphenol, pentylphenol, heptaphenol, octylphenol, nonylphenol, decylphenol, and dodecylphenol;

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

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

[0048] Optionally, the fluorinated acrylic acid includes one or more of 2-fluoroacrylic acid, hexafluorobutyl acrylate and hexafluorobutyl methacrylate, and is further optionally 2-fluoroacrylic acid;

[0049] (2d) The amines include one or more of methylamine, aniline, diethylamine, ethylenediamine, diisopropylamine, diethanolamine, triethanolamine and tetrabutylammonium bromide, and may be selected as diethylamine.

[0050] The application selects the above-mentioned amines for ring-opening of epoxy resin mainly by taking advantage of the nucleophilicity of amines; the ammonium salts formed are hydrophilic and soluble in water to form an aqueous solution, which is conducive to the reaction.

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

[0052] (3a) The temperature of the chain extension treatment is 120℃~150℃;

[0053] (3b) The grafting treatment temperature is 100℃~120℃;

[0054] (3c) The temperature of the open-loop treatment is 60℃~80℃;

[0055] (3d) 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).

[0056] The mass ratio of the four reactants is within the range described above. When combined with the corresponding reaction temperatures for chain extension, grafting, and ring-opening treatments, the reactions at each step can be carried out fully, which is beneficial for obtaining the modified epoxy described in the first aspect of this application.

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

[0058] The insulating composition provided in this application includes a modified epoxy resin and a curing agent. When applied to the preparation of an insulating coating for a battery casing, the curing agent reacts with the modified epoxy resin and crosslinks and cures it into a modified epoxy resin polymer with a three-dimensional network structure. The three-dimensional network structure of the polymer is beneficial to improving the insulating coating's insulation withstand voltage, mechanical strength, and adhesion strength to the battery casing substrate.

[0059] In some embodiments of this application, the insulating composition further includes a protic acid and an organic solvent.

[0060] Optionally, the protic acid includes one or more of lactic acid, acetic acid, and hydrochloric acid, and is further optionally hydrochloric acid;

[0061] Optionally, the organic solvent includes ether-based organic solvents;

[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 solvents used in this application have good hydrophilicity and can exist stably in insulating compositions.

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

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

[0066] (2) The curing agent includes hydroxyl-terminated isocyanate, which may be one or more of fully hydroxyl-terminated isocyanate and half hydroxyl-terminated isocyanate, and may be further selected as fully hydroxyl-terminated 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-mentioned range, which is conducive to the acidification (ionization) of the modified epoxy resin, making it positively charged. Therefore, when the insulating composition is used as a raw material for the preparation of battery insulating coating by electrophoresis, it is beneficial to achieve its deposition on the surface of the battery shell substrate, which serves as the negative electrode, thereby obtaining an insulating coating and improving the bonding force between the insulating coating and the battery shell substrate.

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

[0070] A fifth aspect of this application provides a battery casing, comprising:

[0071] Shell substrate; and

[0072] An insulating coating is disposed on at least a portion of the surface of the housing substrate, the insulating coating comprising a modified epoxy resin polymer, the raw materials for preparing the modified epoxy resin polymer comprising the insulating composition according to any one of claims 8-10.

[0073] A sixth aspect of this application provides a battery casing, comprising:

[0074] Shell substrate; and

[0075] An insulating coating is disposed on at least a portion of the surface of the housing substrate, the insulating coating comprising a modified epoxy resin polymer, the structural units of the modified epoxy resin polymer comprising:

[0076] The epoxy resin main chain includes ether-bonded straight-chain alkanes and / or ether-bonded straight-chain heteroalkanes connected to carbon atoms of the epoxy resin main chain, silicon-containing branches and / or fluorine-containing branches connected to carbon atoms of the epoxy resin main chain, nitrogen-containing segments connected to carbon atoms of terminal epoxy groups on the epoxy resin main chain, and isocyanate-containing segments connected to carbon atoms of the epoxy resin main chain by ether bonds.

[0077] An insulating coating is provided on the substrate of the battery casing. The modified epoxy resin polymer contained in the insulating coating has a dense three-dimensional network structure. This three-dimensional network structure is beneficial to improving the insulating coating's insulation resistance, mechanical strength, and adhesion strength to the casing substrate.

[0078] In some embodiments of this application, the modified epoxy resin polymer comprises structural units as shown in formula (7):

[0079]

[0080] In equation (7), R1 includes At least one of them, wherein R 10 include n is an integer from 0 to 10; R11 Including fluorinated segments, R 12 Includes one or more of hydrogen atoms, C1-C5 alkyl groups, and carboxyl groups.

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

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

[0083] R3 includes

[0084] R4 includes

[0085] Each of them independently represents C1 to C2. 100 One or more of the alkanes and heteroalkanes, * indicates a linking site.

[0086] The modified epoxy resin polymer includes the structural unit shown in formula (7). In this structural unit, the R3 segment located on the main chain, due to the ether bond, allows the molecular chain to rotate and wiggle to a certain extent, thus possessing a certain bending ability and flexibility. Therefore, it can serve 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 insulation performance of the insulating coating, battery casing, and battery. The R1 segment located on the side chain, due to its low polarity, can serve as a hydrophobic segment to improve the resistance to humid heat aging and water resistance of the insulating coating, thereby improving the insulation performance and service life of the insulating coating and battery casing. In addition, the R2 segment located at the end of the main chain is easily ionized under acidic conditions, making the modified epoxy resin positively charged. This can be used for subsequent electrophoretic preparation of the insulating coating; it can also play a chain extension role, improving the flexibility of the chain segment and the insulation performance of the coating.

[0087] In some embodiments of this application, the battery casing 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 120°C is 10,000 to 25,000.

[0091] The modified epoxy resin polymer has a weight-average molecular weight within the above range, which is beneficial to improving the polymer's viscosity and surface energy, thereby enhancing the adhesion strength between the insulating coating and the outer shell substrate, as well as the water resistance of the insulating coating.

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

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

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

[0095] The thickness of the insulating coating is within the above range, which ensures the insulation performance of the battery casing without affecting the performance of the battery cell itself (such as capacity, cycle performance, etc.).

[0096] The seventh aspect of this application provides a method for preparing the battery casing described in the sixth aspect of this application, comprising:

[0097] The outer shell substrate is subjected to electrophoretic treatment using the insulating composition as the electrophoretic solution to form a deposition layer on at least a portion of the surface of the outer shell substrate;

[0098] The outer casing substrate covered with the deposited layer is cured to form the insulating coating, thus obtaining the battery casing.

[0099] Compared with existing methods that directly coat insulating materials onto the battery casing substrate, the method provided in this application can improve the adhesion strength (bonding force) between the insulating coating and the casing substrate, and its curing temperature is lower and energy consumption is lower, which is conducive to large-scale production.

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

[0101] (1) The voltage for the electrophoretic treatment is 200V to 250V.

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

[0103] (2) The curing temperature is 150℃~190℃.

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

[0105] When the curing temperature is within the above range, the hydroxyl groups in the hydroxyl-terminated isocyanate curing agent can be unblocked, thereby realizing and promoting the cross-linking curing reaction between the modified epoxy resin and the curing agent.

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

[0107] The ninth aspect of this application provides an electrical device including the secondary battery described in the eighth aspect of this application.

[0108] The electrical device of this application includes the secondary battery provided in this application, and therefore has at least the same advantages as the secondary battery. Attached Figure Description

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

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

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

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

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

[0114] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0115] Explanation of reference numerals in the attached figures:

[0116] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0117] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the modified epoxy resin and its preparation method, the insulating composition and its application, the battery casing and its preparation method, the secondary battery, and the electrical device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for a full understanding of this application by those skilled in the art and are not intended to limit the subject matter of the claims.

[0118] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0119] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0120] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0121] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

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

[0123] "Alkyl" refers to a saturated hydrocarbon containing a primary (normal) carbon atom, or a secondary carbon atom, or a tertiary carbon atom, or a quaternary carbon atom, or a combination thereof. Phrases containing this term, such as "C1-C9 alkyl," refer to alkyl groups containing 1 to 9 carbon atoms, and each time it appears, it can independently be 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( CH3)CH2CH3), 4-methyl-2-pentyl (-CH(CH3)CH2CH(CH3)2), 3-methyl-3-pentyl (-C(CH3)(CH2CH3)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 a ring of carbon atoms, which can be monocycloalkyl, spirocycloalkyl, or bridged cycloalkyl. Phrases containing this term, such as "C3-C9 cycloalkyl," refer to cycloalkyl compounds containing 3 to 9 carbon atoms, and each occurrence can independently be C3, C4, C5, C6, C7, C8, or C9 cycloalkyl. Suitable examples include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cycloheptyl. Additionally, "cycloalkyl" may contain one or more double bonds; representative examples of cycloalkyl compounds containing double bonds include cyclopentenyl, cyclohexenyl, cyclohexadienyl, and cyclobutadienyl.

[0125] "Epoxy group" refers to a group having an -O-alkyl group, i.e., an alkyl group as defined above connected to the parent nucleus via an oxygen atom. Phrases containing this term, such as "C1-C9 alkoxy," refer to alkyl moieties containing 1 to 9 carbon atoms, and each time it appears, it 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 one hydrogen atom. It can be a monocyclic aryl, a fused-ring aryl, or a polycyclic aryl. For polycyclic compounds, at least one ring must be an aromatic ring system. For example, "C5~C5..." 20 "Aryl" refers to an aryl group containing 5 to 20 carbon atoms. Each time it appears, it can independently be C5 aryl, C6 aryl, C7 aryl, C8 aryl, etc. 10 Aryl, C 14 Aryl, C 18 Aryl or C 20 Aryl groups. Suitable examples include, but are not limited to: benzene, biphenyl, naphthalene, anthracene, phenanthrene, dinaphthalene, triphenylene and their derivatives.

[0127] "Heteroaryl" refers to an aryl group in which at least one carbon atom is replaced by a non-carbon atom, which can be a nitrogen atom, an oxygen atom, a sulfur atom, etc. For example, "C3~C 10"Heteroaryl" refers to a heteroaryl group containing 3 to 10 carbon atoms, which can be independently C3, C4, C5, C6, C7, or C8 heteroaryl each time it appears. Suitable examples include, but are not limited to: furan, benzofuran, thiophene, benzothiophene, pyrrole, pyrazole, triazole, imidazole, oxazole, oxadiazole, thiazole, tetrazolium, indole, carbazole, pyrroloimidazol, pyrrolopyrrole, thiophenolopyrrole, thiophenolothiophene, furanolopyrrole, furanolofuran, thiophenolofuran, benzoisoxazole, benzoisothiazolium, benzimidazole, pyridine, pyrazine, pyridazine, pyrimidine, triazine, quinoline, isoquinoline, o-diazonyl, quinoxaline, phenanthridine, primidine, quinazoline, and quinazolineone.

[0128] "Heteroalkyl" refers to an alkyl group in which at least one carbon atom is replaced by a non-carbon atom, such as a nitrogen (N), oxygen (O), sulfur (S), etc. For example, if a carbon atom in an alkyl group is replaced by a non-carbon atom, the resulting heteroalkyl group is an alkoxy group (e.g., -OCH3), an amine (e.g., -NHCH3, -N(CH3)2), or a thioalkyl group (e.g., -SCH3). If no carbon atom in an alkyl group is replaced by a non-carbon atom, the resulting heteroalkyl group is an alkyl ether (e.g., -CH2CH2-O-CH3), an alkylamine (e.g., -CH2NHCH3, -CH2N(CH3)2), or a thioalkyl ether (e.g., -CH2-S-CH3). If the terminal carbon atom of an 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 alkyl mercapto group (e.g., -CH2CH2-SH). Phrases containing this term, such as “C1-C9 heteroalkyl”, refer to heteroalkyl groups containing 1 to 9 carbon atoms, and each time they appear, they can be independently C2 heteroalkyl, C3 heteroalkyl, C4 heteroalkyl, C5 heteroalkyl, C7 heteroalkyl, C8 heteroalkyl, or C9 heteroalkyl.

[0129] "Heterocyclic group" refers to a cycloalkyl group in which at least one carbon atom is replaced by a non-carbon atom. The non-carbon atom can be an N atom, O atom, S atom, etc., and can be a saturated ring or a partially unsaturated ring. Phrases containing this term, such as "C4-C9 heterocyclic group," refer to heterocyclic groups containing 4 to 9 carbon atoms, and each occurrence can be independently C4, C6, C7, C8, or C9 heteroalkyl. Suitable examples include, but are not limited to: dihydropyridyl, tetrahydropyridyl (piperidinyl), tetrahydrothiophenyl, sulfur-oxidized tetrahydrothiophenyl, tetrahydrofuranyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl, and dihydroindolyl.

[0130] "Amino" refers to a derivative of ammonia, possessing the structural characteristic of the formula -N(X)2, where each "X" is independently H, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted heterocyclic group, etc. Non-limiting amorphous amino groups include -NH2, -N(alkyl)2, -NH(alkyl), -N(cycloalkyl)2, -NH(cycloalkyl), -N(heterocyclic)2, -NH(heterocyclic), -N(aryl)2, -NH(aryl), -N(alkyl)(aryl), -N(alkyl)(heterocyclic), -N(cycloalkyl)(heterocyclic), -N(aryl)(heteroaryl), -N(alkyl)(heteroaryl), etc.

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

[0132] "Alkylene" refers to a hydrocarbon group derived from an alkyl group by removing one hydrogen atom, forming a group with two monovalent groups. It can be a saturated branched alkyl group or a saturated straight-chain alkyl group. For example, "C1-C9 alkylene" refers to an alkyl group containing 1 to 9 carbon atoms, and each occurrence can be independently C1, C4, C5, C6, C7, C8, 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 with 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 by replacing at least one hydrogen atom bonded to a carbon atom on an alkyl group with an aryl group. The aryl moiety may include 5 to 20 carbon atoms, and the alkyl moiety 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 carbide ring structure in their molecules. Suitable examples may include, but are not limited to: -CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2-, and -CH2CH2CH2CH2CH2CH2-.

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

[0137] Currently, in rechargeable batteries, the insulation protection of the battery cells (including the outer casing) is mostly achieved by wrapping the cells with PET blue film. The cells and PET blue film are bonded using an adhesive coating method, which results in low bonding strength. Furthermore, structural adhesive is required to fix the cells together, but the bonding strength between the blue film and the structural adhesive is insufficient, leading to easy detachment of the blue film. In addition, the PET blue film wrapping process is complex and prone to defects such as air bubbles and wrinkles. The blue film itself is easily damaged, affecting the insulation performance between the cell and the external structure. Moreover, the wrapping film needs to be repeatedly applied at the edges and corners of the cells, affecting the subsequent module assembly dimensions. Additionally, during battery pack use, condensation can easily seep in through the blue film splicing areas, connecting the cell outer casing and the external structure, causing the blue film to lose its insulating properties and resulting in a decrease in the insulation performance of the rechargeable battery.

[0138] To address the aforementioned technical problems, this application proposes a modified epoxy resin that, when used in the preparation of an insulating coating for a battery casing, can improve the bonding strength between the insulating coating and the casing substrate, enhance the insulating withstand voltage of the battery casing, and thus improve the insulating performance of the secondary battery.

[0139] In a first aspect, this application provides a modified epoxy resin comprising an epoxy resin backbone, and ether-bonded straight-chain alkanes and / or ether-bonded straight-chain heteroalkanes connected to carbon atoms of the epoxy resin backbone, silicon-containing branches and / or fluorine-containing branches connected to carbon atoms of the epoxy resin backbone, and nitrogen-containing segments connected to carbon atoms of terminal epoxy groups on the epoxy resin backbone.

[0140] In this application, unless otherwise specified, ether-containing straight-chain alkanes refer to straight-chain alkanes whose main chain contains ether bonds, meaning that at least one carbon atom in a segment is replaced by an oxygen atom. Ether-containing straight-chain heteroalkanes refer to straight-chain alkanes whose main chain contains ether bonds, meaning that at least one carbon atom in a segment is replaced by an oxygen atom, and that at least one carbon atom in a segment is replaced by a carbon ring or a non-carbon atom. The non-carbon atom can be an N atom, an S atom, etc.; the carbon ring can be a benzene ring, etc.

[0141] In this application, unless otherwise specified, silicon-containing branches refer to side branches contained in the main chain, wherein at least one carbon atom of the side branch is replaced by at least one of silicon atoms and silicon-containing segments. Fluorine-containing branches refer to side branches contained in the main chain, wherein at least one carbon atom of the side branch is replaced by at least one of fluorine atoms and fluorine-containing segments. Wherein, a silicon-containing segment refers to a molecular chain segment containing at least silicon atoms, and a fluorine-containing segment refers to a molecular chain segment containing at least fluorine atoms.

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

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

[0144] The modified epoxy resin provided in this application modifies the epoxy resin matrix. When this modified epoxy resin is applied to the preparation of the insulating coating for secondary battery casings, the ether-bonded straight-chain alkanes and / or ether-bonded straight-chain heteroalkanes in its structural formula are located on the main chain. Since the ether bonds allow the molecular chains to rotate and oscillate freely to a certain extent, the molecular chains possess a certain degree of bending ability and flexibility. Therefore, they can serve as flexible segments to enhance the flexibility of the modified epoxy resin, thereby improving the toughness and bending resistance of the insulating coating. Consequently, during battery processing and use, the insulating coating exhibits good toughness and bending resistance, making it less prone to damage. Compared to conventional insulating films (such as PET blue film), this modified epoxy resin is beneficial for improving the insulating performance of the insulating coating, battery casing, and battery itself. The silicon-containing and / or fluorine-containing branches located in the modified epoxy resin structure, due to the low polarity of silicon and / or fluorine and their poor solubility in water, can act as hydrophobic segments, thereby improving the resistance to damp heat aging and water resistance of the insulating coating. This benefits the insulation performance and lifespan of both the insulating coating and the battery casing. Furthermore, the nitrogen-containing segments located at the ends of the main chain can act as chain extenders, thereby improving the flexibility of the modified epoxy resin and the insulation performance of the insulating coating.

[0145] In some embodiments, the epoxy resin backbone comprises the structure shown in formula (1):

[0146]

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

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

[0149]

[0150] The ether-containing straight-chain alkanes and / or ether-containing straight-chain heteroalkanes located on the main chain in formula (2) can serve as flexible segments to improve the toughness and bending resistance of the insulating coating, thereby improving the insulation performance of the insulating coating, battery casing and battery.

[0151] In some embodiments, the silicon-containing side chains include the structural formula shown in formula (3):

[0152]

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

[0154] In equation (3), the silicon-containing branches located on the side chains can act as hydrophobic segments, thereby improving the resistance to humid heat aging and water resistance of the insulating coating, and thus improving the insulation performance and service life of the insulating coating and the battery casing. The value of n within the above range is beneficial for further improving the resistance to humid heat aging and water resistance of the insulating coating.

[0155] In some embodiments, the fluorinated branched chain comprises the structural formula shown in formula (4):

[0156]

[0157] In equation (4), R 11 Including fluorinated segments, R 12 It includes one or more of hydrogen atoms, C1 to C5 alkyl groups, and carboxyl groups.

[0158] The fluorinated side chains in formula (4) can be used as hydrophobic segments to improve the resistance to humid heat aging and water resistance of the insulating coating, thereby improving the insulation performance and service life of the insulating coating and battery casing.

[0159] In some embodiments, the fluorinated segment comprises fluorine atoms and One or more of them.

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

[0161]

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

[0163] In some embodiments, in equations (1) to (5) above, Indicates C1~C 100 One or more of the alkanes and heteroalkanes, * indicates a linking site.

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

[0165]

[0166] In equation (6), R1 includes At least one of them, wherein R 10 include n is an integer from 0 to 10; R 11 Including fluorinated segments, R 12 Includes one or more of hydrogen atoms, C1-C5 alkyl groups, and carboxyl groups;

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

[0168] R3 includes

[0169] Each of them independently represents C1 to C2. 100 One or more of the alkanes and heteroalkanes, * indicates a linking site.

[0170] When the modified epoxy resin in formula (6) is used to prepare the insulating coating for a secondary battery casing, the R3 segment on the main chain, due to the ether bond, allows the molecular chain to rotate and wiggle to a certain extent, thus possessing a certain bending ability and flexibility. Therefore, it can serve 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 further improving the insulation performance of the insulating coating, the battery casing, and the battery. The R1 segment on the side chain, due to its low polarity, can serve as a hydrophobic segment to improve the resistance to damp heat aging and water resistance of the insulating coating, thereby improving the insulation performance and service life of the insulating coating and the battery casing. In addition, the R2 segment at the end of the main chain is easily ionized under acidic conditions, making the modified epoxy resin positively charged, which can be used for subsequent electrophoretic preparation of the insulating coating; at the same time, it can also play a chain extension role, improving the flexibility of the chain segment and the insulation performance of the coating.

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

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

[0173] The epoxy equivalent 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 used in the electrophoretic preparation of insulating coatings, 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] Secondly, this application provides a method for preparing the modified epoxy resin described in the first aspect of this application, which may include the following steps:

[0175] S10. Chain extension treatment of epoxy resin using phenolic substances to obtain chain extension reactants;

[0176] S20. Grafting the chain extension reactant with silicon-containing organic compounds and / or fluorine-containing organic compounds to obtain the grafted reactant.

[0177] S30. The grafted reactant is subjected to ring-opening treatment using amines to obtain the modified epoxy resin.

[0178] In the above method, by using phenolic substances to extend the chain of epoxy resin, the segments contained in the phenolic substances can be added to the epoxy resin backbone, thereby lengthening the epoxy resin backbone. By using silicon-containing organic compounds and / or fluorine-containing organic compounds to graft the chain extension reactants, the silicon-containing and / or fluorine-containing segments of the silicon-containing organic compounds and / or fluorine-containing organic compounds can be grafted onto the epoxy resin backbone, giving the resin resistance to damp heat. By using amine substances to perform ring-opening treatment on the grafted reactants, some of the epoxy groups contained in the epoxy resin can be ring-opened, generating a certain number of hydroxyl groups. When the modified epoxy resin is subsequently applied to 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 during the processes described in steps S10 to S30, all reactants can be dissolved in an organic solvent for the reaction. This organic solvent may include ether-based organic solvents, which may include, but are 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-based organic solvents have relatively high boiling points, making them suitable for use in chain extension and grafting processes.

[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 type epoxy resin and bisphenol F type epoxy resin.

[0182] In some embodiments, the phenolic substances include, but are not limited to, one or more of phenol and alkylphenols.

[0183] In some embodiments, the alkylphenol includes one or more of butylphenol, pentylphenol, heptaphenol, 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 fluorinated organic compound includes fluoroacrylic acid.

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

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

[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 may be selected as diethylamine.

[0188] In some embodiments, a catalyst may be added to each of the steps S10 to S30 described 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 application selects the above-mentioned amines for ring-opening of epoxy resin mainly by taking advantage of the nucleophilicity of amines; the ammonium salts formed are hydrophilic and soluble in water to form an aqueous solution, which is conducive to the reaction.

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

[0192]

[0193] If the chain-extending reactant obtained from reaction (10) is denoted as R1', then the reaction in step S20 can be exemplified as follows:

[0194]

[0195] If the grafted reactant obtained from reaction (20) is denoted as R2', then the reaction in step S30 can be exemplified as follows:

[0196]

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

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

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

[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 any range of the above values.

[0201] The mass ratio of the four reactants is within the range described above. When combined with the corresponding reaction temperatures for chain extension, grafting, and ring-opening treatments, the reactions at each step can be carried out fully, which is beneficial for obtaining the modified epoxy described in the first aspect of this application.

[0202] Thirdly, this application provides an insulating composition comprising the modified epoxy resin described in the first aspect of this application or the modified epoxy resin prepared according to the method described in the second aspect of this application, and a curing agent.

[0203] The insulating composition provided in this application includes a modified epoxy resin and a curing agent. When applied to the preparation of an insulating coating for a battery casing, the curing agent reacts with the modified epoxy resin and crosslinks and cures it into a modified epoxy resin polymer with a three-dimensional network structure. The three-dimensional network structure of the polymer is beneficial to improving the insulating coating's insulation withstand voltage, mechanical strength, and adhesion strength to the battery casing substrate.

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

[0205] In some embodiments, the protic acid may be one or more of lactic acid, acetic acid, and hydrochloric acid, with hydrochloric acid being an option.

[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 any range of the above values.

[0207] The pH value of the insulating composition is within the above-mentioned range, which is conducive to the acidification (ionization) of the modified epoxy resin, making it positively charged. Therefore, when the insulating composition is used as a raw material for the preparation of battery insulating coating by electrophoresis, it is beneficial to achieve its deposition on the surface of the battery shell substrate, which serves as the negative electrode, thereby obtaining an insulating coating and improving the bonding force between the insulating coating and the battery shell substrate.

[0208] In some embodiments, the organic solvent includes ether-based organic solvents.

[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 solvents used in this application have good hydrophilicity and can exist stably in insulating compositions.

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

[0212] The molar ratio of epoxy groups to curing agents in modified epoxy resin is within the above range, which is beneficial for the curing agent and modified epoxy resin to react more fully and for the modified epoxy resin to achieve more complete cross-linking and curing. This improves the density of the three-dimensional network structure of the modified epoxy resin polymer, and further enhances the insulation withstand voltage, mechanical strength, and adhesion strength of the insulating coating to the battery casing substrate.

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

[0214] In some embodiments, the hydroxy-terminated isocyanate includes one or more of fully hydroxy-terminated isocyanates and partially hydroxy-terminated isocyanates, and may be selected as fully hydroxy-terminated isocyanates.

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

[0216] In this application, unless otherwise specified, hydroxyl-terminated isocyanates refer to isocyanates whose isocyanate groups contain hydroxyl groups. Fully hydroxyl-terminated isocyanates refer to isocyanates in which all isocyanate groups contain hydroxyl groups; partially hydroxyl-terminated isocyanates refer to isocyanates in which a portion (not less than 50%) of the isocyanate groups contain hydroxyl groups.

[0217] Modified epoxy resins, after ring-opening treatment, contain a large number of hydroxyl groups. The isocyanate groups in the curing agent readily react with the hydroxyl groups in the modified epoxy resin to crosslink and form a film, creating a modified epoxy resin polymer with a three-dimensional network structure. This application uses hydroxyl-terminated isocyanates, which avoids the failure of the insulation composition caused by the modified epoxy resin reacting with the curing agent before the insulating composition is applied to the electrophoretic coating of the battery casing.

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

[0219] When this insulating composition is applied to the preparation of battery casings, it can improve the insulation resistance, water resistance, mechanical strength, and adhesion between the battery casing insulating coating and the battery casing substrate.

[0220] Fifthly, this 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, the insulating coating comprising a modified epoxy resin polymer, the raw materials for preparing the modified epoxy resin polymer comprising the insulating composition described in the third aspect of this application.

[0221] The insulating composition, as a raw material for the preparation of modified epoxy resin polymer, plays a similar role in the preparation of battery casings as described above, and will not be repeated here.

[0222] In a sixth aspect, this 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. The insulating coating comprises a modified epoxy resin polymer, wherein the structural units of the modified epoxy resin polymer include: an epoxy resin backbone, ether-bonded straight-chain alkanes and / or ether-bonded straight-chain heteroalkanes connected to carbon atoms of the epoxy resin backbone, silicon-containing branches and / or fluorine-containing branches connected to carbon atoms of the epoxy resin backbone, nitrogen-containing segments connected to terminal epoxy carbon atoms of the epoxy resin backbone, and isocyanate-containing segments connected to carbon atoms of the epoxy resin backbone by ether bonds.

[0223] An insulating coating is provided on the substrate of the battery casing. The modified epoxy resin polymer contained in the insulating coating has a dense three-dimensional network structure. This three-dimensional network structure is beneficial to improving the insulating coating's insulation resistance, mechanical strength, and adhesion strength to the casing substrate.

[0224] Furthermore, in the structural units of the modified epoxy resin polymer, the ether-containing straight-chain alkanes and / or ether-containing straight-chain heteroalkanes linked to the epoxy resin backbone can act as flexible segments, enhancing the flexibility of the modified epoxy resin polymer and thus improving the toughness and bending resistance of the insulating coating. Consequently, during battery processing and use, the insulating coating, possessing good toughness and bending resistance, is less prone to damage. Compared to conventional insulating films (such as PET blue film), this is beneficial for further improving the insulation performance of the insulating coating, battery casing, and battery itself. Meanwhile, the silicon-containing and / or fluorine-containing branches linked to the epoxy resin backbone can act as hydrophobic segments, improving the insulating coating's resistance to damp heat aging and water resistance. This, in turn, is beneficial for improving the insulation performance and service life of the insulating coating and battery casing.

[0225] In some embodiments, the modified epoxy polymer comprises structural units as shown in formula (7):

[0226]

[0227] In equation (7), R1 includes At least one of them, wherein R 10 include n is an integer from 0 to 10; R 11 Including fluorinated segments, R 12 Includes one or more of hydrogen atoms, C1-C5 alkyl groups, and carboxyl groups.

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

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

[0230] R3 includes

[0231] R4 includes

[0232] Each of them independently represents C1 to C2. 100 One or more of the alkanes and heteroalkanes, * indicates a linking site.

[0233] The modified epoxy resin polymer includes the structural unit shown in formula (7). In this structural unit, the R3 segment located on the main chain, due to the ether bond, allows the molecular chain to rotate and wiggle to a certain extent, thus possessing a certain bending ability and flexibility. Therefore, it can serve 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 insulation performance of the insulating coating, battery casing, and battery. The R1 segment located on the side chain, due to its low polarity, can serve as a hydrophobic segment to improve the resistance to humid heat aging and water resistance of the insulating coating, thereby improving the insulation performance and service life of the insulating coating and battery casing. In addition, the R2 segment located at the end of the main chain is easily ionized under acidic conditions, making the modified epoxy resin positively charged. This can be used for subsequent electrophoretic preparation of the insulating coating; it can also play a chain extension role, improving the flexibility of the chain segment and the insulation performance 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 within any range of the above values.

[0235] The weight-average molecular weight of modified epoxy resin polymers has a well-known meaning in the art and can be tested using methods known in the art. For example, a Waters 2695 Isocratic HPLC gel electrophoresis system (differential refractive index detector 2141) was used, with a 3.0% (w / w) polystyrene solution sample as a reference, and a matched column (oil-based: Styragel HT5DMF7.8×300mm + Styragel HT4) was selected. A 3.0% modified epoxy resin polymer solution was prepared using purified N-methylpyrrolidone (NMP) solvent and allowed to stand for one day. For testing, tetrahydrofuran was first drawn into a syringe and used to rinse the solution, repeated several times. Then, 5 ml of the experimental solution was drawn, air was expelled from the syringe, and the needle tip was dried. Finally, the sample solution was slowly injected into the injection port. After the reading stabilized, the data was acquired, and the weight-average molecular weight was read.

[0236] The modified epoxy resin polymer has a weight-average molecular weight within the above range, which is beneficial to improving the polymer's viscosity and surface energy, thereby enhancing the adhesion strength between the insulating coating and the outer shell substrate, as well as 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 within any range of the above values.

[0238] The degree of polymerization of the modified epoxy resin polymer has a meaning known in the art and can be tested using methods known in the art. For example, it can be tested using NMR (nuclear magnetic resonance) methods.

[0239] When the structural unit shown in formula (7) forms the molecular chain of the polymer, its molecular chain has a high degree of symmetry and the polymer has good crystallization properties, which can contribute to the adhesive properties of the polymer. Therefore, when the number of structural units shown in formula (7), i.e. the degree of polymerization of the modified epoxy resin polymer, is within the above range, the polymer can have high adhesiveness, thereby making the insulating coating have high adhesiveness.

[0240] In some embodiments, the viscosity of the modified epoxy resin polymer is 10,000 to 25,000. For example, the viscosity of the modified epoxy resin polymer may be 10,000, 13,000, 16,000, 19,000, 22,000, 25,000, or within any range of the above values.

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

[0242] The viscosity of modified epoxy resin polymers is a well-known concept in the art and can be tested using methods known in the art. For example, the viscosity of modified epoxy resin polymers can be measured using a rotational viscometer. Select a suitable rotor, fix the viscometer rotor, and place an ether solution of the modified epoxy resin polymer at 120°C below the viscometer rotor, ensuring the solution just submerges the rotor's scale. Instrument model: Shanghai Fangrui NDJ-5S; rotor: 63# (2000-10000 mPa·s), 64# (10000-50000 mPa·s); rotation speed: 12 rpm; test temperature: 25°C; test time: 5 minutes; read the data after the reading stabilizes.

[0243] The viscosity of the modified epoxy resin polymer is within the above range, which enables the insulating coating to have high adhesion and prevents it from falling off during battery use, thereby ensuring that the battery casing has good insulation properties during long-term use.

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

[0245] The thickness of the insulating coating has a meaning known in the art and can be tested using methods known in the art. For example, it can be measured using a micrometer.

[0246] The thickness of the insulating coating is within the above range, which ensures the insulation performance of the battery casing without 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 can be 500V, 1000V, 2000V, 3000V, 4000V, 5000V, 6000V, 7000V, 8000V, or any range of the above values. Optionally, it is 2700V to 7500V.

[0248] The breakdown voltage of the insulating coating has a meaning known in the art and can be tested using methods known in the art. For example, it can be tested using a withstand voltage test method (insulation withstand voltage tester).

[0249] The breakdown voltage of the insulating coating within the aforementioned range is due to the modified epoxy resin polymer. A breakdown voltage within this range ensures the battery meets the withstand voltage requirements of the battery casing during use, maintaining high insulation withstand voltage performance throughout long-term operation.

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

[0251] S10' The outer shell substrate is subjected to electrophoretic treatment with an electrophoretic solution containing the insulating composition to form a deposition layer on at least a portion of the surface of the outer shell substrate;

[0252] S20': The outer casing substrate covered with the deposited layer is cured to form the insulating coating, thereby obtaining the battery casing.

[0253] Understandably, the aforementioned electrophoretic treatment uses the outer shell substrate as the cathode, allowing 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 outer shell substrate. Further, under the influence of an electric field, the positively charged modified epoxy resin ions in the electrophoretic solution migrate to the cathode of the outer shell substrate and react with the alkaline substances generated by ionization on the cathode surface to form an insoluble substance, which is then deposited on the surface of the outer shell substrate. Subsequent curing treatment allows the modified epoxy resin to cross-link and cure, forming a modified epoxy resin polymer with a three-dimensional network structure, thus creating an insulating coating.

[0254] Compared with existing methods that directly coat insulating materials onto the battery casing substrate, the method provided in this application can improve the adhesion strength (bonding force) between the insulating coating and the casing substrate, and its curing temperature is lower and energy consumption is lower, which is conducive to large-scale production.

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

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

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

[0258] When the curing temperature is within the above range, the hydroxyl groups in the hydroxyl-terminated isocyanate curing agent can be unblocked, thereby realizing 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 power device of this application will be described below with appropriate reference to the accompanying drawings.

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

[0261] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0262] [Positive electrode plate]

[0263] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the positive electrode active material of the first aspect of this application.

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

[0265] In some embodiments, the positive 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 substrate and a metal layer formed on at least one surface of the polymer substrate. 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 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 be a known battery positive electrode active material. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0267] It should be noted that during the charging and discharging process of the battery, Li undergoes insertion / extraction and consumption, resulting in different molar contents of Li at different discharge states. In the examples of positive electrode active materials in this application, the molar contents of Li refer to the initial state of the material, i.e., the state before feeding. When the positive electrode active material is applied to the battery system, the molar contents of Li will change after charge-discharge cycles.

[0268] In the examples of positive electrode active materials in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal 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 oxides, polyanionic compounds, and Prussian blue compounds. However, this application is not limited to these materials, and other conventional 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 in this application, the transition metal in the sodium transition metal oxide includes at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. For example, the sodium transition metal oxide is Na. x MO2, where 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 in this application, the polyanionic compound can be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. 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- The price state.

[0272] Polyanionic compounds can also contain sodium ions, transition metal ions, or tetrahedral (YO4) ions. n-A class of compounds containing anionic units and halide anions. 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, where n represents (YO4). n- The valence state; halogens include at least one of F, Cl and Br.

[0273] Polyanionic compounds can also be sodium-containing tetrahedral (YO4) compounds. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y includes at least one of P, S, and Si, and n represents (YO4). n- The valence state; Z represents a transition metal, including at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, and m represents (ZO). y ) m+ The valence state; halogens include at least one of F, Cl and Br.

[0274] Polyanionic compounds include, for example, 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 compounds containing sodium ions, transition metal ions, and cyanide ions (CN). - A class of compounds. Transition metals include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue compounds include, 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 optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0277] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from 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 by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0279] The positive electrode sheet of this application does not exclude other additional functional layers besides the positive electrode film layer. For example, in some embodiments, the positive electrode sheet of this application further includes a conductive undercoat layer (e.g., composed of a conductive agent and a binder) sandwiched between the positive current collector and the positive electrode film layer and disposed on the surface of the positive current collector. In other embodiments, the positive electrode sheet of this application further includes a protective layer covering the surface of the positive electrode film layer.

[0280] [Negative electrode plate]

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

[0282] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either 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, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer 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 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 be a negative electrode active material known in the art for use in batteries. 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, and 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, this application is not limited to these materials, and other conventional 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 optionally 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 may optionally include a conductive agent. The conductive agent 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 may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0288] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0289] The negative electrode sheet of this application does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of this application further includes a conductive undercoat layer (e.g., composed of a conductive agent and an adhesive) 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 other embodiments, the negative electrode sheet of this application further includes a protective layer covering the surface of the negative electrode film layer.

[0290] [Electrolytes]

[0291] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0292] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution 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 difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

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

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

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

[0297] [Isolation membrane]

[0298] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

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

[0300] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0301] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

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

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

[0304] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 The example shown is a square-structured battery cell 5.

[0305] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0306] In some embodiments, the secondary battery may also be a battery module assembled from multiple battery cells. The number of battery cells in the battery module may be multiple, 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 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0308] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

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

[0310] In some implementations, the aforementioned battery cells can also be directly assembled into a battery pack, and the number of battery cells contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0311] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0312] In addition, this application also provides an electrical device, which includes the secondary battery provided in this application. The secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., 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.

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

[0314] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0315] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0316] Example

[0317] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0318] Example 1

[0319] Preparation of modified epoxy resin

[0320] Add 500 mL of ethylene glycol butyl ether, 1 g of dibutyltin dilaurate catalyst, 100 g of bisphenol A epoxy resin, and 35 g of bisphenol A to a 1000 mL four-necked round-bottom flask equipped with a reflux condenser, stirrer, constant pressure funnel, and oil bath temperature control heating device. Stir and heat to 135 °C, and maintain the temperature for 180 min.

[0321] Then add 25g 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℃, and keep warm and stir for 120min.

[0322] Finally, add 2g 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℃, keep warm and stir for 120min to obtain modified epoxy resin.

[0323] Preparation of insulating compositions

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

[0325] Preparation of battery casing

[0326] (1) Preparation of electrophoresis solution

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

[0328] (2) Preparation of insulating coating

[0329] The electrophoresis solution was placed in the electrophoresis tank, the working voltage was adjusted to 230V, the pre-treated shell substrate was connected to the cathode, and after electrophoresis for 3 minutes, it was taken out and cleaned with deionized water to obtain a shell substrate with a deposition layer. Then, the substrate was subjected to gradient heating to 170℃ and held for 30 minutes to form an insulating coating of about 40μm on the surface of the battery shell substrate, thus obtaining the battery shell.

[0330] Preparation of positive electrode sheet

[0331] The positive electrode active material, conductive carbon black SP, and binder PVDF prepared in Example 1 were dispersed in NMP solvent at a weight ratio of 98:1:1 and mixed evenly to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated onto a positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained, with a coating weight of 0.27 g / 1540.25 mm². 2 .

[0332] Preparation of negative electrode sheet

[0333] Graphite (negative electrode active material), sodium carboxymethyl cellulose (thickener), styrene-butadiene rubber (binder), and acetylene black (conductive agent) were mixed in a mass ratio of 97:1:1:1. Deionized water was added, and the mixture was stirred under vacuum to obtain a negative electrode slurry. The negative electrode slurry was then uniformly coated onto copper foil. After the copper foil was dried at room temperature, it was transferred to a 120°C oven and dried for 1 hour. The foil was then cold-pressed and slit to obtain negative electrode sheets with a coating weight of 0.17 g / 1540.25 mm². 2 .

[0334] Preparation of the separating membrane

[0335] A 12μm thick polypropylene separator membrane was selected.

[0336] Preparation of electrolyte

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

[0338] Battery manufacturing

[0339] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. After being wound into a square bare cell, it is installed into the battery casing described above in this application. Then, it is baked at 80°C to remove water, 10g of the corresponding non-aqueous electrolyte is injected, and the cell is sealed. After processes such as standing, hot and cold pressing, formation, clamping, and capacity testing, a finished battery with a capacity of 4000mAh is obtained.

[0340] Examples 2-30

[0341] The preparation methods for 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 have been adjusted. Specific parameters are detailed in Table 1 below. " / " indicates that the corresponding parameter does not exist.

[0342] Example 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, a coating method is used instead of an electrophoresis method, that is, the electrophoretic solution is coated onto the casing substrate.

[0344] Comparative Example 1

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

[0346] Comparative Example 2

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

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

[0349] Table 1

[0350]

[0351]

[0352]

[0353]

[0354] In addition, performance tests were conducted on the insulating coatings and battery casings of Examples 1-31 and Comparative Examples 1-2. 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 for 60s, repeat 25 times, and ensure leakage current ≤0.1mA.

[0358] (2) Toughness

[0359] According to GB / T 1732 (≥5J), it meets the requirements of no paint peeling, cracks or other defects under 1x and 4x magnification; and meets the above insulation withstand voltage requirements.

[0360] (3) Bending resistance

[0361] According to GB / T 6742-86, shafts with different radii of curvature should be bent 180° to meet the following requirements: ① no paint film peeling or cracking; ② adhesion grade 0 to 1; ③ insulation withstand voltage requirements as described above.

[0362] (4) Adhesion

[0363] Prepare coating@structural adhesive@coating test samples according to GBT 7124. Test temperature: 25℃, tensile speed: 5mm / min, adhesive layer thickness: 0.2mm.

[0364] (5) Resistance to damp heat aging

[0365] The bonding strength, insulation withstand voltage performance, and adhesion were tested in an 85℃, 85%RH damp heat aging chamber for 1000 hours.

[0366] (6) Water resistance

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

[0368] (7) Adhesion

[0369] ISO 2409 cross-cutting test.

[0370] Table 2

[0371]

[0372]

[0373] As can be seen from the comparison of the examples with Comparative Example 1 in Table 2 above, the insulation properties of the insulating coating and battery casing provided in this application are significantly improved compared with conventional PET blue film; in addition, the bending resistance, adhesion, resistance to damp heat aging, water resistance and adhesion of the insulating coating are also significantly improved.

[0374] Comparing the examples 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 this application has significantly higher insulation, resistance to damp heat aging, and water resistance, indicating that the modified epoxy resin is beneficial to improving the above-mentioned properties of the insulating coating.

[0375] Comparing Example 31 with Example 1, it can be seen that after using the conventional coating method instead of the electrophoresis method to prepare the insulating coating, 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 in Example 20 using the unsealed curing agent is significantly lower than that in Example 1, indicating that whether or not the curing agent is sealed has a significant impact on the preparation process of the insulating coating.

[0377] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A modified epoxy resin, characterized in that, include: Epoxy resin backbone; and The epoxy resin contains ether-bonded straight-chain alkanes and / or ether-bonded straight-chain heteroalkanes connected to the carbon atoms of the main chain, silicon-containing branches and / or fluorine-containing branches connected to the carbon atoms of the main chain, and nitrogen-containing segments connected to the carbon atoms of the terminal epoxy groups on the main chain. The modified epoxy resin has the following structural formula (6): （6）， In equation (6), R1 includes and At least one of them, wherein R 10 include n is an integer from 0 to 10; R 11 comprising a fluorine-containing segment, R 12 comprising one or more of a hydrogen atom, a C1-C5 alkyl group, and a carboxyl group; The fluorinated segment includes fluorine atoms, and One or more of the following; R2 includes , where R 20 and R 21 Each independently includes one or more of the following: hydrogen atom, alkyl, cycloalkyl, epoxy group, aryl, heteroaryl, heteroalkyl, heterocyclic, amino, alkylene, halogen, hydroxyl, alkylamino and arylalkyl; R3 includes or ; Each of C1~C represents itself independently. 100 One or more of alkanes and heteroalkanes, * indicates a linking site; The epoxy equivalent of the modified epoxy resin is 500~2000.

2. The modified epoxy resin according to claim 1, characterized in that, The epoxy equivalent of the modified epoxy resin is 800~2000.

3. The modified epoxy resin according to claim 1 or 2, characterized in that, The epoxy equivalent of the modified epoxy resin is 800~1200.

4. A method for preparing the modified epoxy resin according to any one of claims 1-3, characterized in that, include: Chain extension treatment of epoxy resin using phenolic substances was used to obtain chain extension reactants; The chain extender reactant is grafted onto a silicon-containing organic compound and / or a fluorine-containing organic compound to obtain a grafted reactant. The modified epoxy resin is obtained by ring-opening treatment of the grafted reactant with amines. The phenolic substances include 2,2-bis(4-hydroxyphenyl)propane and / or 4,4-dihydroxydiphenylmethane; the epoxy resin includes glycidyl ether epoxy resin; the silicon-containing organic matter includes polydimethylsiloxane; the fluorinated organic matter includes fluorinated acrylic acid; and the amine substances include one or more of methylamine, aniline, diethylamine, ethylenediamine, diisopropylamine, diethanolamine, triethanolamine, and tetrabutylammonium bromide.

5. The method according to claim 4, characterized in that, At least one of the following conditions must be met: (2a) The polydimethylsiloxane includes one or both of vinyl polydimethylsiloxane and amino polydimethylsiloxane; (2b) The fluorinated acrylic acid includes one or more of 2-fluoroacrylic acid, hexafluorobutyl acrylate and hexafluorobutyl methacrylate.

6. The method according to claim 4 or 5, characterized in that, The epoxy resin includes one or both of bisphenol A type epoxy resin and bisphenol F type epoxy resin.

7. The method according to any one of claims 4-6, characterized in that, At least one of the following conditions must be met: (3a) The temperature of the chain extension treatment is 120℃~150℃; (3b) The grafting treatment temperature is 100℃~120℃; (3c) The temperature of the open-loop treatment is 60℃~80℃; (3d) 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).

8. An insulating composition, characterized in that, It includes the modified epoxy resin according to any one of claims 1-3 or the modified epoxy resin prepared by the method according to any one of claims 4-7, and a curing agent.

9. The insulating composition according to claim 8, characterized in that, It also includes protic acids and organic solvents.

10. The insulating composition according to claim 9, characterized in that, One or more of the following conditions must be met: (1) The protic acid includes one or more of lactic acid, acetic acid and hydrochloric acid; (2) The organic solvents include ether organic solvents.

11. The insulating composition according to claim 10, characterized in that, The ether organic solvents include one or more of ethylene glycol butyl ether, ethylene glycol methyl ether, diethylene glycol butyl ether, and diethylene glycol ethyl ether.

12. The insulating composition according to any one of claims 8-11, characterized in that, At least one of the following conditions must be met: (1) The molar ratio of epoxy groups in the modified epoxy resin to the curing agent is 1:(1~0.7); (2) The curing agent includes hydroxyl-terminated isocyanates; (3) The pH value of the insulating composition is 5.8~6.

6.

13. The insulating composition according to claim 12, characterized in that, The curing agent is one or more of hydroxyl-terminated isocyanates and hydroxyl-semi-terminated isocyanates.

14. The insulating composition according to claim 12 or 13, characterized in that, The curing agent is a hydroxyl-terminated isocyanate.

15. The use of the insulating composition according to any one of claims 8-14 in the preparation of a battery casing.

16. A battery casing, characterized in that, include: Shell substrate; and An insulating coating is disposed on at least a portion of the surface of the housing substrate, the insulating coating comprising a modified epoxy resin polymer, the raw materials for preparing the modified epoxy resin polymer comprising the insulating composition according to any one of claims 8-14.

17. A battery casing, characterized in that, include: Shell substrate; and An insulating coating is disposed on at least a portion of the surface of the housing substrate, the insulating coating comprising a modified epoxy resin polymer, the structural units of the modified epoxy resin polymer comprising: Ether-containing straight-chain alkanes and / or ether-containing straight-chain heteroalkanes connected to the carbon atoms of the epoxy resin main chain; silicon-containing branches and / or fluorine-containing branches connected to the carbon atoms of the epoxy resin main chain; nitrogen-containing segments connected to the carbon atoms of the terminal epoxy groups on the epoxy resin main chain; and isocyanate-containing segments connected to the carbon atoms of the epoxy resin main chain by ether bonds. The modified epoxy resin polymer comprises the structural unit shown in formula (7): （7）， In equation (7), R1 includes and At least one of them, wherein R 10 include n is an integer from 0 to 10; R 11 Including fluorinated segments, R 12 Includes one or more of hydrogen atoms, C1-C5 alkyl groups, and carboxyl groups. The fluorinated segment includes fluorine atoms, and One or more of the following; R2 includes , where R 20 and R 21 Each independently includes one or more of the following: hydrogen atom, alkyl, cycloalkyl, epoxy group, aryl, heteroaryl, heteroalkyl, heterocyclic, amino, alkylene, halogen, hydroxyl, alkylamino and arylalkyl; R3 includes or ; R4 includes ; Each of C1~C represents itself independently. 100 One or more of alkanes and heteroalkanes, * indicates a linking site; The modified epoxy resin polymer satisfies at least one of the following conditions: (1) The weight-average molecular weight of the modified epoxy resin polymer is 1000~4000; (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 120°C is 10000~25000.

18. The battery casing according to claim 17, characterized in that, At least one of the following conditions must be met: (1) The thickness of the insulating coating is 20μm~70μm; (2) The breakdown voltage of the insulating coating is 500V~8000V.

19. The battery casing according to claim 18, characterized in that, At least one of the following conditions must be met: (1) The thickness of the insulating coating is 40μm~50μm; (2) The breakdown voltage of the insulating coating is 2700V~7500V.

20. A method for preparing a battery casing according to any one of claims 17-19, characterized in that, include: The outer shell substrate is subjected to electrophoretic treatment using the insulating composition according to any one of claims 8-14 as the electrophoretic solution to form a deposition layer on at least a portion of the surface of the outer shell substrate; The outer casing substrate covered with the deposited layer is cured to form the insulating coating, thus obtaining the battery casing.

21. The method according to claim 20, characterized in that, At least one of the following conditions must be met: (1) The voltage of the electrophoretic treatment is 200V~250V; (2) The curing temperature is 150℃~190℃.

22. The method according to claim 21, characterized in that, The electrophoretic treatment temperature is 29℃~35℃.

23. A secondary battery, characterized in that, Includes the battery casing as described in any one of claims 16-19 or the battery casing manufactured by the method described in any one of claims 20-22.

24. An electrical appliance, characterized in that, Includes the secondary battery as described in claim 23.

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