Positive electrode binder, positive electrode plate, battery and electric equipment

Abstract

The invention discloses a positive electrode binder, a positive plate, a battery and electric equipment, the positive electrode binder comprises modified polyimide, the main chain and / or side chain of the modified polyimide has crown ether groups, the crown ether groups comprise 3n-crown-n groups, and n is a positive integer greater than or equal to 4. According to the positive electrode binder disclosed by the invention, the crown ether group is introduced into the modified polyimide, so that the diffusivity of metal ions in an electrode is effectively improved, and the obstruction of the metal ions in a positive electrode active material intercalation and deintercalation reaction is reduced, so that the battery impedance is effectively reduced, and the battery performance is improved.

Description

Technical Field

[0001] The present application belongs to the field of batteries, and specifically relates to a positive electrode binder, a positive electrode sheet, a battery and an electrical device. Background Art

[0002] At present, the majority of binders used in the positive electrode of commercial lithium-ion batteries are polyvinylidene fluoride (PVDF) polymers. During the long-term use of lithium-ion batteries, PVDF polymers show relatively excellent comprehensive properties, such as excellent electrolyte resistance, mechanical properties, long-term stability, etc. However, in order to achieve more stringent electrode manufacturing processes and use conditions, and with the continuous development of secondary batteries such as sodium ions, potassium ions and even zinc ions, and to avoid the restrictions of fluorine-containing products in corresponding regulations and policies, various types of non-fluorine binder products such as hydrogenated nitrile rubber (HNBR), polyacrylonitrile (PAN), polyimide (PI), polyacrylic acid (PAA), etc. are used as positive electrode binders. Among them, PI binders are widely concerned for their excellent slurry and electrode manufacturing process characteristics.

[0003] However, while providing bonding ability, the binder will exist as an electrochemically inert material in the pores of the positive electrode active material and form a coating layer on the surface of the active material, which will inhibit the diffusion of metal cations to a certain extent and hinder the embedding and extraction reactions of metal cations in the positive electrode active material, increasing the battery impedance, thereby causing the battery's rate performance to deteriorate. At the same time, due to the excellent film-forming properties of PI polymers, the coating layer formed will be more complete and dense, and the hindrance to the embedding and extraction of metal ions will be more significant than that of PVDF, which will further increase the battery's impedance and thus deteriorate the battery performance. Summary of the invention

[0004] The present application aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the purpose of the present application is to provide a positive electrode binder, a positive electrode sheet, a battery and an electrical device. The positive electrode binder of the present application effectively improves the diffusion capacity of metal ions in the electrode by introducing crown ether groups into the modified polyimide, reduces the hindrance of metal ion embedding and extraction reactions in the positive electrode active material, thereby effectively reducing the battery impedance and improving the battery performance.

[0005] In a first aspect, the present application provides a positive electrode binder. According to an embodiment of the present application, the positive electrode binder includes a modified polyimide, the modified polyimide has a crown ether group on the main chain and / or side chain, and the crown ether group includes a 3n-crown-n group, wherein n is a positive integer greater than or equal to 4.

[0006] The positive electrode binder of the above-mentioned embodiment of the present application has a matrix of modified polyimide. The modified polyimide is modified with crown ether groups so that the positive electrode binder provided by the present application contains crown ether groups, and different metal ions are complexed according to the size of the crown ether ring to construct metal ion channels, promote the dissociation of metal salts and the desolvation of metal ions, improve the diffusion capacity of metal ions in the electrode, reduce the obstacles to the embedding and extraction reactions of metal ions in the positive electrode active material, thereby reducing the battery impedance and improving the battery performance.

[0007] In addition, the positive electrode binder according to the above embodiment of the present application may also have the following additional technical features:

[0008] In some embodiments of the present application, the crown ether group includes at least one of a 12-crown-4 group, a 15-crown-5 group, and a 18-crown-6 group;

[0009] The structural formula of the 12-crown-4 group is Among them, R1~R 16 At least one of A1 to A4 independently includes at least one of oxygen, nitrogen, sulfur, and phosphorus atoms;

[0010] The structural formula of the 15-crown-5 group is Among them, R'1~R' 20 At least one of them includes at least one of carbon atom, nitrogen atom, sulfur atom, oxygen atom, phosphorus atom and boron atom; D1-D5 each independently include at least one of oxygen atom, nitrogen atom, sulfur atom and phosphorus atom;

[0011] The structural formula of the 18-crown-6 group is Among them, M1~M 24 At least one of E1 to E6 independently includes at least one of carbon, nitrogen, sulfur, oxygen, phosphorus and boron atoms; E1 to E6 each independently include at least one of oxygen, nitrogen, sulfur and phosphorus atoms.

[0012] In some embodiments of the present application, the modified polyimide includes an aromatic group, and the mass of the aromatic group accounts for less than 40% of the mass of the modified polyimide.

[0013] In some embodiments of the present application, the modified polyimide is formed by polymerizing a polyanhydride monomer, a polyamine monomer and a crown ether monomer containing a bonding group, and the polyanhydride monomer and / or the polyamine monomer have a chemically reactive group.

[0014] In some embodiments of the present application, the chemically reactive groups include at least one of a carbon-carbon double bond, a carbon-carbon triple bond, a hydroxyl group, a thiol group, a carboxyl group, an epoxy group, an ester group, an aldehyde group, a halogen atom, and an isocyanate group; and / or, the bonding groups of the crown ether monomers include at least one of a carbon-carbon double bond, a carbon-carbon triple bond, a hydroxyl group, an amino group, a thiol group, a carboxyl group, an epoxy group, an ester group, an aldehyde group, a halogen atom, an anhydride group, and an isocyanate group.

[0015] In some embodiments of the present application, based on the total mass of the polyanhydride monomer, the polyamine monomer and the crown ether monomer being 100%, the mass proportion of the crown ether monomer is 3% to 25%.

[0016] In some embodiments of the present application, the modified polyimide is formed by polymerizing a polyacid anhydride monomer containing a crown ether group and a polyamine monomer; or, the modified polyimide is formed by polymerizing a polyacid anhydride monomer and a polyamine monomer containing a crown ether group.

[0017] In some embodiments of the present application, based on the total mass of the polyacid anhydride monomer containing a crown ether group and the polyamine monomer being 100%, the mass of the polyacid anhydride monomer containing a crown ether group accounts for 3% to 25%; or, based on the total mass of the polyacid anhydride monomer and the polyamine monomer containing a crown ether group being 100%, the mass of the polyamine monomer containing a crown ether group accounts for 3% to 25%.

[0018] The second aspect of the present application proposes a positive electrode sheet. According to an embodiment of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer formed on at least one side of the positive electrode current collector, and the positive electrode active material layer includes the positive electrode binder described in the first aspect. Thus, the positive electrode binder in the positive electrode sheet contains crown ether groups, which can produce complexation with metal ions, construct metal ion channels, promote the dissociation of metal salts and the desolvation of metal ions, improve the diffusion capacity of metal ions in the positive electrode sheet, and reduce the obstacles to the embedding and extraction reactions of metal ions in the positive electrode active material, thereby reducing the battery impedance and improving the battery performance.

[0019] In addition, the positive electrode sheet according to the above embodiment of the present application may also have the following additional technical features:

[0020] In some embodiments of the present application, the positive electrode active material layer includes a positive electrode active material, the positive electrode binder and a conductive agent, and the mass ratio of the positive electrode active material, the positive electrode binder and the conductive agent is 100:(1-20):(1-20).

[0021] The third aspect of the present application provides a battery. According to an embodiment of the present application, the battery includes the positive electrode sheet of the second aspect. Thus, the battery impedance can be effectively reduced and the battery performance can be improved.

[0022] The fourth aspect of the present application provides an electric device. According to an embodiment of the present application, the electric device includes the battery of the third aspect. As a result, the electric device has excellent service life and safety performance. It should be noted that the features and advantages described above for the battery are also applicable to the electric device, and will not be repeated here.

[0023] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. DETAILED DESCRIPTION

[0024] The embodiments of the present application are described in detail below, which are intended to be used to explain the present application but should not be construed as limiting the present application.

[0025] In a first aspect, the present application provides a positive electrode binder. According to an embodiment of the present application, the positive electrode binder includes a modified polyimide, the modified polyimide has a crown ether group on the main chain and / or side chain, and the crown ether group includes a 3n-crown-n group, wherein n is a positive integer greater than or equal to 4, for example, n can be 4, 5, 6, 7, 8, 9, 10, etc.

[0026] Therefore, the positive electrode binder provided by the present application includes modified polyimide, and the crown ether group is modified on the modified polyimide so that the positive electrode binder provided by the present application contains the crown ether group, and produces complexation on different metal ions according to the size of the crown ether ring, constructs metal ion channels, promotes the dissociation of metal salts and the desolvation of metal ions, improves the diffusion capacity of metal ions in the electrode, reduces the obstacles to the embedding and extraction reactions of metal ions in the positive electrode active material, thereby reducing the battery impedance and improving the battery performance.

[0027] The modified PI binder in the present application is suitable for a variety of secondary batteries such as lithium ions, sodium ions, potassium ions, etc., and crown ether structures of different ring sizes can be selected according to different metal ions to form a transmission channel for specific metal ions.

[0028] The following is a detailed description of the principle by which the positive electrode binder proposed in this application can achieve the above beneficial effects:

[0029] According to some specific embodiments of the present application, the crown ether group includes at least one of a 12-crown-4 group, a 15-crown-5 group, an 18-crown-6 group, a 21-crown-7 group, a 24-crown-8 group, and a 27-crown-9 group;

[0030] The structural formula of the 12-crown-4 group is Among them, R1~R 16 At least one of the above mentioned monomers includes at least one of carbon atoms, nitrogen atoms, sulfur atoms, oxygen atoms, phosphorus atoms and boron atoms, and the at least one of the above mentioned monomers can be formed by bonding the bonding groups in the crown ether monomers with the chemically reactive groups on the acid anhydride monomers or the amine monomers, or can be contained in the polyacid anhydride monomers containing the crown ether groups. The remaining R1 to R 16 Each of A1 to A4 independently includes at least one of an oxygen atom, a nitrogen atom, a sulfur atom, and a phosphorus atom, preferably an oxygen atom.

[0031] The structural formula of the 15-crown-5 group is Among them, R'1~R' 20 At least one of the above mentioned monomers includes at least one of carbon atoms, nitrogen atoms, sulfur atoms, oxygen atoms, phosphorus atoms and boron atoms, and the at least one of the above mentioned monomers can be formed by bonding the bonding groups in the crown ether monomers with the chemically reactive groups on the acid anhydride monomers or the amine monomers, or can be contained in the polyanhydride monomers containing the crown ether groups. The remaining R'1 to R' 20 Each of D1 to D5 independently includes at least one of an oxygen atom, a nitrogen atom, a sulfur atom and a phosphorus atom, preferably an oxygen atom.

[0032] The structural formula of the above 18-crown-6 group is Among them, M1~M 24 At least one of the above mentioned monomers includes at least one of carbon atoms, nitrogen atoms, sulfur atoms, oxygen atoms, phosphorus atoms and boron atoms, and the at least one of the above mentioned monomers can be formed by bonding the bonding groups in the crown ether monomers with the chemically reactive groups on the acid anhydride monomers or the amine monomers, or can be contained in the polyacid anhydride monomers containing the crown ether groups. The remaining M1 to M 24 Each of E1 to E6 independently includes at least one of an oxygen atom, a nitrogen atom, a sulfur atom, and a phosphorus atom, preferably an oxygen atom.

[0033] It should be noted that R1 to R 16 and R1 to R2 in the above 15-crown-5 group 16 They may be the same or different. R1 to R 20 and R1 to R2 in the above 18-crown-6 group 20 Can be the same or different.

[0034] In the embodiments of the present application, the above-mentioned positive electrode binder can be applied to a variety of secondary batteries such as lithium ions, sodium ions, potassium ions, etc., and crown ether structures of different ring sizes can be selected according to different metal ions to form a transmission channel for specific metal ions. Specifically, when the positive electrode material is a positive electrode active material for lithium batteries such as lithium iron phosphate (LFP), lithium iron manganese phosphate (LFMP), nickel cobalt manganese lithium oxide (NCM), nickel cobalt aluminum lithium oxide (NCA), lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium-rich manganese-based materials, etc., the modified crown ether structure can be selected from 12-crown-4, 15-crown-5, 18-crown-6 and larger ring structures. + Excellent complexation with 12-crown-4, 12-crown-4 modified binder is preferred.

[0035] When the positive electrode material is a sodium battery positive electrode active material such as layered oxides (such as NaFeO2, NaCoO2, NaMnO2, Na x Mn y Ni 1-y O2、Na x Fe y Mn 1-y O2, etc.), polyanions (such as NaFePO4, Na3V2(PO4)3, Na2FeP2O7, etc.), Prussian blue (such as NaMn[Fe(CN)6], NaFe[Fe(CN)6], etc.) and organic compounds, the modified crown ether structure can choose 15-crown-5, 18-crown-6 and larger ring structures. + Excellent complexation with 15-crown-5, 15-crown-5 modified binder is preferred.

[0036] When the positive electrode material is a potassium battery positive electrode active material such as layered oxides (such as NaFeO2, KCoO2, KMnO2, KNi x Mn y Ni 1-x-y O2、KFe y Mn 1-y O2, etc.), polyanions (such as KFePO4, K3V2(PO4)3, KVP2O7, KFeSO4F, etc.), Prussian blue (such as KMn[Fe(CN)6], KFe[Fe(CN)6], etc.) and organic compounds, the modified crown ether structure can choose 18-crown-6 and larger ring structures. + Excellent complexation with 18-crown-8, 18-crown-8 modified binder is preferred.

[0037] Other metal ion secondary batteries, such as Zn 2+ 、Al 3+ Mg 2+ , Ca2+ Etc., the crown ether structure-modified binder of appropriate size can be selected according to the size of the metal ions.

[0038] According to some specific embodiments of the present application, the above-mentioned modified polyimide includes aromatic groups, and the mass of the aromatic groups accounts for less than 40% of the mass of the modified polyimide. Thus, it can ensure that the modified polyimide is better dissolved in the positive electrode solvent, thereby improving the dispersion performance of the positive electrode slurry, which is conducive to the formation of a positive electrode sheet with uniform and stable performance.

[0039] According to some specific embodiments of the present application, the modified polyimide can be formed by polymerizing a polyanhydride monomer, a polyamine monomer and a crown ether monomer containing a bonding group, and the anhydride monomer and / or the amine monomer have a chemically reactive group so as to react with the crown ether monomer containing a bonding group, and the crown ether group is grafted onto the side chain of the modified polyimide. That is, the polyanhydride monomer and the polyamine monomer are firstly polymerized to form the matrix of the modified polyimide, and then the crown ether group is grafted onto the side chain of the modified polyimide.

[0040] It should be noted that the above-mentioned polyanhydride monomers include dianhydride monomers and other polyanhydride monomers. The above-mentioned polyamine monomers include diamine monomers and other polyamine monomers.

[0041] The crown ether monomer containing a bonding group includes at least one of 12-crown-4, 15-crown-5 and 18-crown-6;

[0042] The structural formula of the above 12-crown-4 is Among them, R1~R 16 At least one of them is the above-mentioned reactive bonding group, and the others can be hydrogen atoms or any groups; A1 to A4 each independently include at least one of oxygen atoms, nitrogen atoms, sulfur atoms, and phosphorus atoms, preferably oxygen atoms.

[0043] The structural formula of the above 15-crown-5 is Among them, R'1~R' 20 At least one of them is the above-mentioned reactive bonding group, and the others can be hydrogen atoms or any groups; D1 to D5 each independently include at least one of oxygen atoms, nitrogen atoms, sulfur atoms, and phosphorus atoms, preferably oxygen atoms.

[0044] The structural formula of the above 18-crown-6 is Among them, M1~M 24 At least one of them is the above-mentioned reactive bonding group, and the others can be hydrogen atoms or any groups; E1 to E6 each independently include at least one of oxygen atoms, nitrogen atoms, sulfur atoms, and phosphorus atoms, preferably oxygen atoms.

[0045] It should be noted that R1 to R 16 R'1~R' in the above 15-crown-5 16 They may be the same or different. R'1 to R' in the above 15-crown-5 20 Compared with M1~M in the above 18-crown-6 20 Can be the same or different.

[0046] In the embodiments of the present application, the chemically reactive groups contained in the above-mentioned anhydride monomers and / or amine monomers are not particularly limited. As some specific examples, the chemically reactive groups contained in the anhydride monomers and / or amine monomers include at least one of carbon-carbon double bonds, carbon-carbon triple bonds, hydroxyl groups, sulfhydryl groups, carboxyl groups, epoxy groups, ester groups, aldehyde groups, halogen atoms and isocyanate groups. The chemically reactive groups of the above-mentioned types can react with the bonding groups in the crown ether monomers so as to graft the crown ether groups onto the side chains of the modified polyimide. Preferably, the chemically reactive groups contained in the anhydride monomers and / or amine monomers include sulfhydryl groups, epoxy groups, carboxyl groups, hydroxyl groups, isocyanate groups and carbon-carbon double bonds.

[0047] In the embodiments of the present application, the bonding groups of the crown ether monomers are not particularly limited. As some specific examples, the bonding groups of the crown ether monomers include at least one of a carbon-carbon double bond, a carbon-carbon triple bond, a hydroxyl, an amino group, a sulfhydryl group, a carboxyl group, an epoxy group, an ester group, an aldehyde group, a halogen atom, an anhydride group, and an isocyanate group. The bonding groups of the above types can react with the chemically reactive groups contained in the anhydride monomers and / or the amine monomers so as to graft the crown ether groups onto the side chains of the modified polyimide. Preferably, the bonding groups of the crown ether monomers include a sulfhydryl group, an epoxy group, a carboxyl group, a hydroxyl group, an isocyanate group, and a carbon-carbon double bond.

[0048] According to some further specific embodiments of the present application, based on the total mass of the polyacid anhydride monomer, the polyamine monomer and the crown ether monomer being 100%, the mass proportion of the crown ether monomer is 3% to 25%, for example, 3%, 5%, 7.5%, 10%, 12.5%, 15%, 17.5%, 20%, 22.5%, 25%, etc., the positive electrode binder thus formed can further improve the diffusion ability of metal ions in the electrode, further reduce the hindrance of the embedding and extraction reaction of metal ions in the positive electrode active material, further reduce the battery impedance, and improve the battery performance.

[0049] According to some other specific embodiments of the present application, the above-mentioned modified polyimide can be prepared by directly polymerizing a polyacid anhydride monomer containing a crown ether group and a polyamine monomer so that the crown ether group is formed on the main chain of the modified polyimide; or, the above-mentioned modified polyimide can be prepared by directly polymerizing a polyacid anhydride monomer and a polyamine monomer containing a crown ether group so that the crown ether group is formed on the main chain of the modified polyimide.

[0050] According to some other specific embodiments of the present application, based on the total mass of the polyacid anhydride monomers and polyamine monomers containing crown ether groups being 100%, the mass proportion of the polyacid anhydride monomers containing crown ether groups is 3% to 25%, for example, 3%, 5%, 7.5%, 10%, 12.5%, 15%, 17.5%, 20%, 22.5%, 25%, etc. The positive electrode binder thus formed can further improve the diffusion ability of metal ions in the electrode, further reduce the hindrance of the embedding and extraction reaction of metal ions in the positive electrode active material, further reduce the battery impedance, and improve the battery performance.

[0051] Alternatively, the total mass of the polyamine monomers based on the polyacid anhydride monomers and the crown ether group-containing polyamine monomers is 100%, and the mass proportion of the polyamine monomers containing the crown ether group is 3% to 25%, for example, 3%, 5%, 7.5%, 10%, 12.5%, 15%, 17.5%, 20%, 22.5%, 25%, etc. The positive electrode binder thus formed can further improve the diffusion ability of metal ions in the electrode, further reduce the hindrance of the metal ion embedding and extraction reaction in the positive electrode active material, further reduce the battery impedance, and improve the battery performance.

[0052] The second aspect of the present application proposes a positive electrode sheet. According to an embodiment of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer formed on at least one side of the positive electrode current collector, and the positive electrode active material layer includes the positive electrode binder described in the above embodiment. Thus, the positive electrode binder in the positive electrode sheet contains crown ether groups, which can produce complexation with metal ions, construct metal ion channels, promote the dissociation of metal salts and the desolvation of metal ions, improve the diffusion capacity of metal ions in the positive electrode sheet, and reduce the obstacles to the embedding and extraction reactions of metal ions in the positive electrode active material, thereby reducing the battery impedance and improving the battery performance.

[0053] According to some specific embodiments of the present application, the positive electrode active material layer includes a positive electrode active material, a positive electrode binder and a conductive agent, and the mass ratio of the positive electrode active material, the positive electrode binder and the conductive agent is 100:(1-20):(1-20). Thus, the diffusion capacity of metal ions in the positive electrode sheet can be further improved, the hindrance of metal ion embedding and extraction reaction in the positive electrode active material can be further reduced, the battery impedance can be further reduced, and the battery performance can be improved.

[0054] In some embodiments of the present application, the positive electrode current collector may include a metal foil or a composite positive electrode current collector. For example, the metal foil may be aluminum foil. The composite positive electrode current collector may include a polymer material base and a metal layer formed on at least one side of the polymer material base. For example, the composite negative electrode current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and other substrates).

[0055] In some embodiments of the present application, the positive electrode active material layer further includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0056] In some embodiments of the present application, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet (such as positive electrode active material, conductive agent, positive electrode binder) are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0057] The third aspect of the present application provides a battery. According to an embodiment of the present application, the battery includes the positive electrode sheet of the second aspect. Thus, the battery impedance can be effectively reduced and the battery performance can be improved.

[0058] In the embodiments of the present application, the above-mentioned positive electrode binder can be applicable to various secondary batteries such as lithium ion batteries, sodium ion batteries, potassium ion batteries, etc., and crown ether structures of different ring sizes can be selected according to different metal ions to form a transmission channel for specific metal ions.

[0059] The following is an example of lithium-ion batteries:

[0060] Generally, lithium-ion batteries include a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery charge and discharge process, active lithium ions are embedded and removed between the positive electrode and the negative electrode. The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The separator is set between the positive electrode and the negative electrode, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0061] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0062] In some embodiments of the present application, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0063] In some embodiments of the present application, the negative electrode active material may be a negative electrode active material for a battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, etc. The silicon-based material may include at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may include at least one of elemental tin, tin-oxygen compounds, and tin alloys.

[0064] In some embodiments of the present application, the negative electrode active material layer may further optionally include a positive electrode binder. The positive electrode binder may include 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).

[0065] In some embodiments of the present application, the negative electrode active material layer may further include a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0066] In some embodiments of the present application, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0067] In some embodiments of the present application, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet (such as negative electrode active material, conductive agent, positive electrode binder and any other components) are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0068] The present application has no particular restrictions on the type of isolation membrane, and any known porous isolation membrane with good chemical stability and mechanical stability can be selected. In some embodiments of the present application, the isolation membrane may be made of at least one of glass fiber, non-woven fabric, polyethylene, polypropylene or polyvinylidene fluoride.

[0069] The lithium-ion battery of the present application may include a battery cell form, a battery module form and a battery pack form. In some embodiments, the battery cells may be assembled into a battery module, and the number of battery cells contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module. In some embodiments, the battery modules may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0070] The fourth aspect of the present application provides an electric device. According to an embodiment of the present application, the electric device includes the battery of the third aspect. As a result, the electric device has excellent service life and safety performance. It should be noted that the features and advantages described above for the battery are also applicable to the electric device, and will not be repeated here.

[0071] Battery cells, battery modules, and battery packs can be used as power sources for electrical devices or as energy storage units for electrical devices. Electrical devices may include, but are 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, satellites, energy storage systems, etc.

[0072] As an electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0073] As an embodiment, the electric device may be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electric device for high power and high energy density of the battery, a battery pack or a battery module may be used.

[0074] As another embodiment, the device may be a mobile phone, a tablet computer, a notebook computer, etc. The device is usually required to be light and thin, and a battery cell may be used as a power source.

[0075] It should be noted that the features and advantages described above for the battery are also applicable to the electrical device and will not be described in detail here.

[0076] The embodiments of the present application are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. In addition, unless otherwise explicitly stated, all reagents used in the following embodiments are commercially available or can be synthesized according to this article or known methods, and the reaction conditions not listed are also easily available to those skilled in the art.

[0077] Example 1

[0078] 1) Preparation of positive electrode

[0079] The positive electrode active material lithium iron phosphate LiFePO4, the positive electrode binder, and the conductive agent carbon black are mixed in a mass ratio of 100:5:5, and a certain amount of N-methylpyrrolidone (NMP) is added, and the positive electrode slurry is obtained by stirring evenly under the action of a vacuum mixer; the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil and dried; then transferred to a vacuum oven and dried at 120°C for 24 hours, and then rolled and cut to obtain a positive electrode sheet.

[0080] The matrix of the positive electrode binder is polyimide PI, wherein the amine monomer is Accounting for 29.6wt%; anhydride monomers are The proportion is 65.4wt%; the modified monomer is The modified monomer accounts for 5.0 wt %. First, the amine monomer and the anhydride monomer are reacted to obtain polyimide PI, and then the modified monomer is grafted onto the side chain of the polyimide PI to obtain the above-mentioned positive electrode binder.

[0081] 2) Preparation of negative electrode

[0082] The negative electrode active material artificial graphite, the conductive agent carbon black, the binder styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) are mixed in a mass ratio of 94:2:2:2, a certain amount of deionized water is added, and the mixture is stirred evenly under the action of a vacuum mixer to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil and dried; then the mixture is transferred to a vacuum oven and dried at 120°C for 24 hours, and then rolled and cut to obtain a negative electrode sheet.

[0083] 3) Preparation of electrolyte

[0084] In a nitrogen atmosphere glove box with a water content of <1ppm and an oxygen content of <1ppm, organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a mass ratio of EC:EMC=3:5 as a mixed solvent, and then lithium salt LiPF6 is slowly dissolved in the mixed organic solvent, wherein the mass percentage of the lithium salt LiPF6 is 16% based on the total mass of the electrolyte.

[0085] 4) Isolation film

[0086] The diaphragm is a PE-coated ceramic diaphragm with a thickness of 12 μm.

[0087] 5) Lithium-ion battery preparation

[0088] In a glove box, under an Ar gas atmosphere, the positive electrode sheets, separators, and negative electrode sheets were alternately stacked, and an electrolyte was injected to prepare a soft-pack lithium-ion battery.

[0089] Example 2

[0090] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0091] The positive electrode active material is nickel cobalt manganese lithium oxide NCM811;

[0092] The matrix of the positive electrode binder is polyimide PI, in which the amine monomer is The proportion is 8.6wt%; The proportion is 25.6wt%; the anhydride monomer is The proportion is 53.8wt%; the modified monomer is The modified monomer accounts for 12.0 wt %. First, the amine monomer and the anhydride monomer are reacted to obtain polyimide PI, and then the modified monomer is grafted onto the side chain of the polyimide PI to obtain the above-mentioned positive electrode binder.

[0093] Example 3

[0094] 1) Preparation of positive electrode

[0095] The positive electrode active material NaMn 0.5 Ni 0.5 O2, positive electrode binder, and conductive agent carbon black are mixed in a mass ratio of 100:5:5, and a certain amount of N-methylpyrrolidone (NMP) is added, and the positive electrode slurry is obtained by stirring evenly under the action of a vacuum mixer; the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil and dried; then transferred to a vacuum oven and dried at 120°C for 24 hours, and then rolled and cut to obtain a positive electrode sheet.

[0096] The matrix of the positive electrode binder is polyimide PI, wherein the amine monomer is The proportion is 20.0wt%, The proportion is 13.1wt%, and the anhydride monomer is The proportion is 66.9 wt %. The amine monomer and the anhydride monomer are directly polymerized so as to form the crown ether group on the main chain of the modified polyimide to obtain the positive electrode binder.

[0097] 2) Preparation of negative electrode

[0098] The negative electrode active material hard carbon, the conductive agent carbon black, the binder styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) are mixed in a mass ratio of 94:2:2:2, a certain amount of deionized water is added, and the mixture is stirred evenly under the action of a vacuum mixer to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil and dried; then the mixture is transferred to a vacuum oven and dried at 120°C for 24 hours, and then rolled and cut to obtain a negative electrode sheet.

[0099] 3) Preparation of electrolyte

[0100] In a nitrogen atmosphere glove box with a water content of <1ppm and an oxygen content of <1ppm, organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethylene glycol dimethyl ether are mixed in a mass ratio of EC:EMC:diethylene glycol dimethyl ether=1:1:1 as a mixed solvent as an organic solvent, and then sodium hexafluorophosphate is slowly dissolved in the above organic solvent, wherein the mass percentage of sodium hexafluorophosphate based on the total mass of the electrolyte is 16%.

[0101] 4) Isolation film

[0102] The diaphragm is a PE-coated ceramic diaphragm with a thickness of 12 μm.

[0103] 5) Preparation of sodium ion batteries

[0104] In a glove box, under an Ar gas atmosphere, the positive electrode sheets, separators, and negative electrode sheets were alternately stacked, and an electrolyte was injected to prepare a soft-pack sodium-ion battery.

[0105] Example 4

[0106] The preparation method of this embodiment is basically the same as that of embodiment 3, except that:

[0107] The positive electrode active material is selected as NaMn[Fe(CN)6];

[0108] The matrix of the positive electrode binder is polyimide PI, wherein the amine monomer is The proportion is 19.2wt%, and the anhydride monomer is The proportion is 55.8wt%, and the modified monomer is The modified monomer accounts for 25.0 wt %. First, the amine monomer and the anhydride monomer are reacted to obtain polyimide PI, and then the modified monomer is grafted onto the side chain of the polyimide PI to obtain the positive electrode binder.

[0109] Example 5

[0110] 1) Preparation of positive electrode

[0111] The positive electrode active material KFe 0.5 Mn 0.5 O2, positive electrode binder, and conductive agent carbon black are mixed in a mass ratio of 100:5:5, and a certain amount of N-methylpyrrolidone (NMP) is added, and the positive electrode slurry is obtained by stirring evenly under the action of a vacuum mixer; the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil and dried; then transferred to a vacuum oven and dried at 120°C for 24 hours, and then rolled and cut to obtain a positive electrode sheet.

[0112] The matrix of the positive electrode binder is polyimide PI, wherein the amine monomer is The proportion is 38.5wt%, and the anhydride monomer is The proportion is 45.5wt%, and the modified monomer is The modified monomer accounts for 16.0 wt %. The amine monomer and the anhydride monomer are directly polymerized so as to form a crown ether group on the main chain of the modified polyimide to obtain the positive electrode binder.

[0113] 2) Preparation of negative electrode

[0114] The negative electrode active material artificial graphite, the conductive agent carbon black, the binder styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) are mixed in a mass ratio of 94:2:2:2, a certain amount of deionized water is added, and the mixture is stirred evenly under the action of a vacuum mixer to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil and dried; then the mixture is transferred to a vacuum oven and dried at 120°C for 24 hours, and then rolled and cut to obtain a negative electrode sheet.

[0115] 3) Preparation of electrolyte

[0116] In a nitrogen atmosphere glove box with a water content of <1ppm and an oxygen content of <1ppm, ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) are mixed in a mass ratio of EC:DMC:EMC=1:1:1 as an organic solvent, and then potassium hexafluorophosphate is slowly dissolved in the above organic solvent, wherein the mass percentage of potassium hexafluorophosphate based on the total mass of the electrolyte is 16%.

[0117] 4) Isolation film

[0118] The diaphragm is a PE-coated ceramic diaphragm with a thickness of 12 μm.

[0119] 5) Preparation of potassium ion batteries

[0120] In a glove box, under an Ar gas atmosphere, the positive electrode sheets, separators, and negative electrode sheets were alternately stacked, and an electrolyte was injected to prepare a soft-pack potassium ion battery.

[0121] Example 6

[0122] The preparation method of this embodiment is basically the same as that of embodiment 5, except that:

[0123] The positive electrode active material is K3V2(PO4)3;

[0124] The matrix of the positive electrode binder is polyimide PI, wherein the amine monomer is The proportion is 30.8wt%, and the anhydride monomer is The proportion is 3.0wt%, The proportion is 66.2 wt %. The amine monomer and the anhydride monomer are directly polymerized so as to form the crown ether group on the main chain of the modified polyimide to obtain the above-mentioned positive electrode binder.

[0125] Example 7

[0126] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0127] The mass ratio of the positive electrode active material lithium iron phosphate LiFePO4, the positive electrode binder, and the conductive agent carbon black is 100:1:5.

[0128] Example 8

[0129] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0130] The mass ratio of the positive electrode active material lithium iron phosphate LiFePO4, the positive electrode binder, and the conductive agent carbon black is 100:10:5.

[0131] Example 9

[0132] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0133] The mass ratio of the positive electrode active material lithium iron phosphate LiFePO4, the positive electrode binder, and the conductive agent carbon black is 100:15:5.

[0134] Example 10

[0135] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0136] The mass ratio of the positive electrode active material lithium iron phosphate LiFePO4, the positive electrode binder, and the conductive agent carbon black is 100:20:5.

[0137] Comparative Example 1

[0138] The preparation method of this comparative example is basically the same as that of Example 1. The positive electrode active material of this comparative example is the same lithium iron phosphate LiFePO4 as that in Example 1, with the only difference being:

[0139] The structure of the binder is similar to that in Example 1, wherein the amine monomer is Accounting for 26.6wt%, anhydride monomers are It accounts for 73.4wt%.

[0140] Comparative Example 2

[0141] The preparation method of this comparative example is basically the same as that of Example 1. The positive electrode active material of this comparative example is the same lithium iron phosphate LiFePO4 as that in Example 1, with the only difference being:

[0142] The binder is PVDF.

[0143] Comparative Example 3

[0144] The preparation method of this comparative example is basically the same as that of Example 2. The positive electrode active material of this comparative example is the same nickel cobalt manganese lithium oxide NCM811 as that in Example 2, with the only difference being:

[0145] The structure of the binder is similar to that in Example 6, wherein the amine monomer is The proportion is 9.0wt%, Accounting for 26.9wt%, anhydride monomers are It accounts for 64.1wt%.

[0146] Comparative Example 4

[0147] The preparation method of this comparative example is basically the same as that of Example 2. The positive electrode active material of this comparative example is the same nickel cobalt manganese lithium oxide NCM811 as that in Example 2, with the only difference being:

[0148] The binder is PVDF.

[0149] Comparative Example 5

[0150] The preparation method of this comparative example is basically the same as that of Example 3. The positive electrode active material of this comparative example is the same NaMn as that in Example 3. 0.5 Ni 0.5 O2, the only difference is:

[0151] The binder matrix is ​​polyimide PI, in which the amine monomer is The proportion is 13.2wt%, The proportion is 14.2wt%, and the anhydride monomer is It accounts for 72.6wt%.

[0152] Comparative Example 6

[0153] The preparation method of this comparative example is basically the same as that of Example 3. The positive electrode active material of this comparative example is the same NaMn as that in Example 3. 0.5 Ni 0.5 O2, the only difference is:

[0154] The binder is PVDF.

[0155] Comparative Example 7

[0156] The preparation method of this comparative example is basically the same as that of Example 4. The positive electrode active material of this comparative example is the same NaMn[Fe(CN)6] as that in Example 4, with the only difference being:

[0157] The structure of the binder is similar to that in Example 4, wherein the amine monomer is The proportion is 25.6wt%, and the anhydride monomer is It accounts for 74.4wt%.

[0158] Comparative Example 8

[0159] The preparation method of this comparative example is basically the same as that of Example 4. The positive electrode active material of this comparative example is the same NaMn[Fe(CN)6] as that in Example 4, with the only difference being:

[0160] The binder is PVDF.

[0161] Comparative Example 9

[0162] The preparation method of this comparative example is basically the same as that of Example 5. The positive electrode active material of this comparative example is KFe, which is the same as that in Example 5. 05 Mn 05 O2, the only difference is:

[0163] The structure of the binder is similar to that in Example 5, wherein the amine monomer is The proportion is 41.1wt%, and the anhydride monomer is It accounts for 58.9wt%.

[0164] Comparative Example 10

[0165] The preparation method of this comparative example is basically the same as that of Example 5. The positive electrode active material of this comparative example is KFe, which is the same as that in Example 5. 0.5 Mn 0.5 O2, the only difference is:

[0166] The binder is PVDF.

[0167] Comparative Example 11

[0168] The preparation method of this comparative example is basically the same as that of Example 6. The positive electrode active material of this comparative example is K3V2(PO4)3, which is the same as that in Example 6. The only difference is that:

[0169] The structure of the binder is similar to that in Example 6, wherein the amine monomer is The proportion is 31.0wt%, and the anhydride monomer is The proportion is 2.1wt%, It accounts for 66.9wt%.

[0170] Comparative Example 12

[0171] The preparation method of this comparative example is basically the same as that of Example 6. The positive electrode active material of this comparative example is K3V2(PO4)3, which is the same as that in Example 6. The only difference is that:

[0172] The binder is PVDF.

[0173] The direct current internal resistance (DCIR) and rate performance at 50% SOC of the batteries prepared in Examples 1-10 and Comparative Examples 1-12 were tested respectively, and the results are shown in Table 1.

[0174] DC internal resistance (DCIR) at 50% SOC: The state of charge (SOC) of the above soft-pack batteries was adjusted to 50% SOC at 25°C, and then discharged at 1C for 30s respectively, and the voltage drop of each soft-pack battery was recorded to calculate the DC impedance.

[0175] Rate performance: The discharge capacity of each soft-pack battery at different rates of 0.2C, 1C, and 3C was tested at 25°C, and the ratio of the discharge capacity at 1C and 3C to the discharge capacity at 0.2C was calculated.

[0176] Table 1

[0177]

[0178]

[0179] It can be seen from Table 1 that, compared with Comparative Examples 1-2, the discharge DCIR of Example 1 is significantly reduced, and the 1C / 0.2C discharge capacity ratio and 3C / 0.2C discharge capacity ratio of Example 1 are significantly improved. It can be seen that the introduction of crown ether groups into polyimide PI can improve the diffusion capacity of metal ions in the electrode and reduce the hindrance of metal ion embedding and extraction reactions in the positive electrode active material, thereby reducing the impedance of the battery and improving the discharge capacity ratio of the battery.

[0180] It can also be seen from Table 1 that, compared with Comparative Examples 3-4, the discharge DCIR of Example 2 is significantly reduced, and the 1C / 0.2C discharge capacity ratio and 3C / 0.2C discharge capacity ratio of Example 2 are significantly improved. It can be seen that the introduction of crown ether groups into polyimide PI can improve the diffusion capacity of metal ions in the electrode and reduce the hindrance of metal ion embedding and extraction reactions in the positive electrode active material, thereby reducing the impedance of the battery and improving the discharge capacity ratio of the battery.

[0181] It can also be seen from Table 1 that, compared with Comparative Examples 5-6, the discharge DCIR of Example 3 is significantly reduced, and the 1C / 0.2C discharge capacity ratio and 3C / 0.2C discharge capacity ratio of Example 3 are significantly improved. It can be seen that the introduction of crown ether groups into polyimide PI can improve the diffusion capacity of metal ions in the electrode, reduce the hindrance of metal ion embedding and extraction reactions in the positive electrode active material, thereby reducing the impedance of the battery and improving the discharge capacity ratio of the battery.

[0182] It can also be seen from Table 1 that, compared with Comparative Examples 7-8, the discharge DCIR of Example 4 is significantly reduced, and the 1C / 0.2C discharge capacity ratio and 3C / 0.2C discharge capacity ratio of Example 4 are significantly improved. It can be seen that the introduction of crown ether groups into polyimide PI can improve the diffusion capacity of metal ions in the electrode and reduce the hindrance of metal ion embedding and extraction reactions in the positive electrode active material, thereby reducing the impedance of the battery and improving the discharge capacity ratio of the battery.

[0183] It can also be seen from Table 1 that, compared with Comparative Examples 9-10, the discharge DCIR of Example 5 is significantly reduced, and the 1C / 0.2C discharge capacity ratio and 3C / 0.2C discharge capacity ratio of Example 5 are significantly improved. It can be seen that the introduction of crown ether groups into polyimide PI can improve the diffusion capacity of metal ions in the electrode and reduce the hindrance of metal ion embedding and extraction reactions in the positive electrode active material, thereby reducing the impedance of the battery and improving the discharge capacity ratio of the battery.

[0184] It can also be seen from Table 1 that, compared with Comparative Examples 11-12, the discharge DCIR of Example 6 is significantly reduced, and the 1C / 0.2C discharge capacity ratio and 3C / 0.2C discharge capacity ratio of Example 6 are significantly improved. It can be seen that the introduction of crown ether groups into polyimide PI can improve the diffusion capacity of metal ions in the electrode and reduce the hindrance of metal ion embedding and extraction reactions in the positive electrode active material, thereby reducing the impedance of the battery and improving the discharge capacity ratio of the battery.

[0185] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0186] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A positive electrode binder, characterized in that: The positive electrode binder comprises modified polyimide. The modified polyimide has crown ether groups on its main chain and / or side chain. The crown ether groups comprise 3n-crown-n groups, wherein n is a positive integer greater than or equal to 4.

2. The positive electrode binder according to claim 1, characterized in that The crown ether group includes at least one of a 12-crown-4 group, a 15-crown-5 group, and a 18-crown-6 group; The structural formula of the 12-crown-4 group is Among them, R1~R 16 At least one of A1 to A4 independently includes at least one of oxygen, nitrogen, sulfur, and phosphorus atoms; The structural formula of the 15-crown-5 group is Among them, R'1~R' 20 At least one of them includes at least one of carbon atom, nitrogen atom, sulfur atom, oxygen atom, phosphorus atom and boron atom; D1-D5 each independently include at least one of oxygen atom, nitrogen atom, sulfur atom and phosphorus atom; The structural formula of the 18-crown-6 group is Among them, M1~M 24 At least one of E1 to E6 independently includes at least one of carbon, nitrogen, sulfur, oxygen, phosphorus and boron atoms; E1 to E6 each independently include at least one of oxygen, nitrogen, sulfur and phosphorus atoms.

3. The positive electrode binder according to claim 1 or 2, characterized in that: The modified polyimide includes aromatic groups, and the mass of the aromatic groups accounts for less than 40% of the mass of the modified polyimide.

4. The positive electrode binder according to claim 1 or 2, characterized in that: The modified polyimide is formed by polymerizing a polyanhydride monomer, a polyamine monomer and a crown ether monomer containing a bonding group, and the polyanhydride monomer and / or the polyamine monomer have a chemically reactive group.

5. The positive electrode binder according to claim 4, characterized in that The chemically reactive groups include at least one of a carbon-carbon double bond, a carbon-carbon triple bond, a hydroxyl group, a thiol group, a carboxyl group, an epoxy group, an ester group, an aldehyde group, a halogen atom and an isocyanate group; And / or, the bonding group of the crown ether monomer includes at least one of a carbon-carbon double bond, a carbon-carbon triple bond, a hydroxyl group, an amino group, a thiol group, a carboxyl group, an epoxy group, an ester group, an aldehyde group, a halogen atom, an anhydride group and an isocyanate group.

6. The positive electrode binder according to claim 4, characterized in that Based on the total mass of the polyacid anhydride monomer, the polyamine monomer and the crown ether monomer being 100%, the mass proportion of the crown ether monomer is 3% to 25%.

7. The positive electrode binder according to claim 1 or 2, characterized in that: The modified polyimide is formed by polymerizing a polyacid anhydride monomer containing a crown ether group and a polyamine monomer; Alternatively, the modified polyimide is formed by polymerizing a polyanhydride monomer and a polyamine monomer containing a crown ether group.

8. The positive electrode binder according to claim 7, characterized in that Based on the total mass of the polyacid anhydride monomer containing a crown ether group and the polyamine monomer being 100%, the mass proportion of the polyacid anhydride monomer containing a crown ether group is 3% to 25%; Alternatively, based on the total mass of the polyacid anhydride monomer and the polyamine monomer containing a crown ether group being 100%, the mass proportion of the polyamine monomer containing a crown ether group is 3% to 25%.

9. A positive electrode sheet, characterized in that: The invention comprises a positive electrode current collector and a positive electrode active material layer formed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises the positive electrode binder according to any one of claims 1 to 8.

10. The positive electrode sheet according to claim 9, characterized in that: The positive electrode active material layer includes a positive electrode active material, a positive electrode binder and a conductive agent, and the mass ratio of the positive electrode active material, the positive electrode binder and the conductive agent is 100:(1-20):(1-20).

11. A battery, characterized in that: Including the positive electrode sheet as described in claim 9 or 10.

12. An electrical device, characterized in that: Comprising the battery of claim 11.

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