Polymer electrolyte and its preparation method and application

Abstract

This application provides a polymer electrolyte, a preparation method, and applications thereof. The polymer electrolyte comprises a polymer and an electrolyte salt. The polymer comprises a first structural unit and a second structural unit, wherein R1, R2, R3, R4, R5, and R6 are identical or different polyether groups. The polymer electrolyte provided herein has both high mechanical properties and excellent ionic conductivity, which is beneficial for improving the cycle performance and structural reliability of the battery.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to polymer electrolytes and their preparation methods and applications. Background Art

[0002] As the industry's demands for higher capacity and safety performance in energy storage devices continue to rise, polymer electrolytes are required to possess both high mechanical properties and excellent ionic conductivity. Previously, ionic conductivity could be improved by modifying the polymer structure, but this would lower the polymer's glass transition temperature, resulting in a decrease in crystallinity and, consequently, reduced mechanical properties. Therefore, a polymer electrolyte with both high mechanical strength and high ionic conductivity is needed. Summary of the Invention

[0003] In view of this, the present application provides a polymer electrolyte, a preparation method and an application thereof, wherein the polymer electrolyte includes a polymer with short-range order and long-range disorder. The short-range order and long-range disorder structure can improve the mechanical strength of the polymer electrolyte, and the disordered structure of the long-range chain segments can promote ion migration and improve the ionic conductivity of the polymer electrolyte.

[0004] In a first aspect, the present application provides a polymer electrolyte,

[0005] The polymer electrolyte comprises a polymer and an electrolyte salt, and the polymer comprises a structural formula

[0006] The first structural unit and structural formula are The second structural unit, wherein R1, R2, R3, R4, R5 and R6 are the same or different polyether groups.

[0007] Optionally, the polyether group includes M1 and M2 are selected from hydrogen atoms or alkyl groups, and n1 and n2 are selected from integers ranging from 1 to 100.

[0008] Optionally, the molar percentage of the first structural unit is 10%-90%, and the molar percentage of the second structural unit is 10%-90%.

[0009] Optionally, the weight average molecular weight of the polymer is 6×10 5 g / mol-2×10 6 g / mol.

[0010] Optionally, the polymer has a crystallinity of 30%-50%.

[0011] Optionally, the electrolyte salt includes a lithium salt.

[0012] Optionally, the lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorosilicate, lithium tetraphenylborate, lithium chloride, lithium bromide, lithium chloroaluminate, lithium fluoroalkylsulfonate, lithium methanesulfonate, lithium bis(trifluoromethanesulfonyl)imide and lithium bis(pentafluoroethylsulfonyl)imide.

[0013] Optionally, the ratio of the number of lithium ions in the lithium salt to the number of oxygen atoms in the polymer is 1:(6-40).

[0014] Optionally, in the polymer electrolyte, the mass percentage of the polymer is 35%-45%, and the mass percentage of the electrolyte salt is 25%-35%.

[0015] Optionally, the polymer electrolyte further comprises an inorganic filler and a plasticizer. Optionally, the inorganic filler comprises one or more of silicon dioxide, aluminum oxide, and titanium dioxide; and the plasticizer comprises a carbonate solvent.

[0016] Optionally, the mass percentage of the plasticizer is 25%-35%, and the mass percentage of the inorganic filler is 1.5%-2.5%.

[0017] Optionally, the ionic conductivity of the polymer electrolyte is greater than or equal to 10 -6 .

[0018] The polymer electrolyte provided in this application includes short-range ordered and long-range disordered polymers. The short-range ordered and long-range disordered structure can improve the mechanical strength of the polymer electrolyte, and the disordered long-range chain segments can promote ion migration and improve the ionic conductivity of the polymer electrolyte, so that the polymer has both high ionic conductivity and excellent mechanical properties.

[0019] In a second aspect, the present application provides a method for preparing a polymer electrolyte, comprising:

[0020] The polymer and electrolyte salt solution are mixed and dried to obtain a polymer electrolyte.

[0021] Optionally, the preparation method of the polymer includes:

[0022] The structural formula is The first structural unit monomer and the structural formula are The second structural unit monomers are mixed and polymerized to obtain a polymer; wherein R1, R2, R3, R4, R5 and R6 are the same or different polyether groups.

[0023] Optionally, the molar ratio of the first structural unit monomer to the second structural unit monomer is (4-6):(3-5).

[0024] Optionally, the polymerization reaction temperature is 100°C-150°C.

[0025] The preparation method of the polymer electrolyte provided in this application is novel, the preparation process is simple, and the prepared product has excellent performance.

[0026] In a third aspect, the present application provides a composite electrode, which includes the polymer electrolyte described in the first aspect or the polymer electrolyte prepared by the preparation method described in the second aspect.

[0027] The composite electrode provided in this application has high electrical conductivity, good mechanical properties and excellent comprehensive performance.

[0028] In a fourth aspect, the present application provides a battery, comprising the polymer electrolyte described in the first aspect, or the polymer electrolyte prepared by the preparation method described in the second aspect, or the composite electrode described in the third aspect.

[0029] The battery provided in this application has high capacity, excellent electrochemical performance and long cycle life.

[0030] In a fifth aspect, the present application provides an electrical device, which includes the battery described in the fourth aspect.

[0031] The electrical equipment provided by this application has strong comprehensive competitiveness, long service life and high safety performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0033] Figure 1 Schematic diagram of the cross-sectional structure of a battery according to one embodiment of the present application. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0035] The present application provides a polymer electrolyte, including a polymer and an electrolyte salt, wherein the polymer includes a structural formula The first structural unit and structural formula are The second structural unit, wherein R1, R2, R3, R4, R5 and R6 are the same or different polyether groups.

[0036] The structural units have similar conjugated structures, so that the short-range chain segments of the polymer form short-range ordered crystalline structures through physical cross-linking, thereby improving the crystallinity of the short-range chain segments, ensuring that the crystallinity is not destroyed during stretching and compression, ensuring that the polymer electrolyte has deformation resistance, and improving the mechanical properties of the polymer electrolyte; after the first structural unit and the second structural unit are combined to form a polymer, R1, R2, R3, R4, R5 and R6 of the side chains are the same or different polyether groups, which are long-range disordered, reduce the crystallinity of the long-range chain segments, and are amorphous, which can prevent the polymer electrolyte from breaking during stretching and compression, reduce the permanent deformation of the polymer electrolyte caused by the destruction of the short-range crystalline structure, and inhibit the fracture deformation of the polymer electrolyte; at the same time, the conjugated structure in the first structural unit and the second structural unit has sulfur atoms, which can further increase the electron density of the conjugated structure, facilitate the flow of electrons, increase the attraction to ions, improve the complex strength between the flexible side chains and the electrolyte salt, facilitate the rapid migration of electrolyte ions, and improve the ionic conductivity of the polymer electrolyte. The polymer electrolyte provided in this application has both high mechanical properties and excellent ionic conductivity, which is beneficial to improving the cycle performance and structural reliability of the battery and extending the service life of the battery.

[0037] In one embodiment of the present application, the structural formula of the polymer is Wherein, k is 0.1-0.9. Specifically, the value of k can be, but is not limited to, 0.1, 0.2, 0.4, 0.6, 0.8, or 0.9. In one embodiment of the present application, k can be 0.2, and 1-k is 0.8. In another embodiment of the present application, k can be 0.6, and 1-k is 0.4.

[0038] In one embodiment of the present application, the mole percentage of the first structural unit is 10%-90%, and the mole percentage of the second structural unit is 10%-90%. The appropriate mole percentages enable the polymer to have both high mechanical properties and excellent ionic conductivity. Specifically, the mole percentage of the first structural unit can be, but is not limited to, 10%, 20%, 30%, 50%, 70%, 80%, or 90%, etc.; the mole percentage of the second structural unit can be, but is not limited to, 10%, 20%, 30%, 50%, 70%, 80%, or 90%, etc. In one embodiment of the present application, the mole percentage of the first structural unit can be 10%-60%, and the mole percentage of the second structural unit can be 40%-90%. In another embodiment of the present application, the mole percentage of the first structural unit can be 50%-90%, and the mole percentage of the second structural unit can be 10%-50%.

[0039] In one embodiment of the present application, R1, R2, R3, R4, R5 and R6 are the same or different polyether groups, which can promote the flow of electrolytes in the electrolyte salt in the polymer and improve the ionic conductivity of the polymer electrolyte. R1, R2, R3, R4, R5 and R6 can have the same structure, or R1, R2, R3, R4, R5 and R6 can have different structures. Specifically, the polyether group can be, but is not limited to, selected from In one embodiment of the present application, R1, R2, R3, R4, R5 and R6 can be In another embodiment of the present application, R1 can be (copolymer of propylene oxide and ethylene oxide), R2 and R3 can be R4, R5 and R6 can be

[0040] In one embodiment of the present application, M1 and M2 are independently selected from hydrogen atoms or alkyl groups, and n1 and n2 are independently selected from integers between 1 and 100. Specifically, M1 may be, but is not limited to, a hydrogen atom or an alkyl group, and M2 may be, but is not limited to, a hydrogen atom or an alkyl group; n1 may be, but is not limited to, 1, 10, 20, 40, 60, 80, or 100, and n2 may be, but is not limited to, 1, 10, 20, 40, 60, 80, or 100, and the like. In one embodiment of the present application, M1 may be a hydrogen atom, and n1 may be an integer between 3 and 60, which may further improve the bonding between the electrolyte salt and the side chain. In another embodiment of the present application, M2 may be an alkyl group, and n2 may be an integer between 50 and 100.

[0041] In one embodiment of the present application, the number of carbon atoms in the alkyl group is 1-18. Specifically, the number of carbon atoms in the alkyl group may be, but is not limited to, 1, 2, 4, 6, 8, 10, 12, 14, 16, or 18. In one embodiment of the present application, the number of carbon atoms in the alkyl group may be 1-12. In another embodiment of the present application, the number of carbon atoms in the alkyl group may be 10-18.

[0042] In one embodiment of the present application, the polymer can be capped with a common capping agent in the art. In one embodiment of the present application, the capping group includes a phenyl group. In this case, the structural formula of the polymer is In another embodiment of the present application, the capping group may be a phenyl substituted derivative.

[0043] In one embodiment of the present application, the weight average molecular weight of the polymer is 6×10 5 g / mol-2×10 6 g / mol, and a suitable weight average molecular weight is beneficial to improving the ionic conductivity and ion transference number of the polymer electrolyte. Specifically, the weight average molecular weight of the polymer can be, but is not limited to, 6×10 5g / mol, 7×10 5 g / mol, 8×10 5 g / mol, 9×10 5 g / mol, 1×10 6 g / mol or 2×10 6 In one embodiment of the present application, the weight average molecular weight of the polymer may be 6×10 5 g / mol-9×10 5 In another embodiment of the present application, the weight average molecular weight of the polymer can be 8×10 5 g / mol-2×10 6 g / mol.

[0044] In one embodiment of the present application, the crystallinity of the polymer is 30%-50%. A lower crystallinity can improve the deformation ability of the polymer electrolyte and ensure that the polymer electrolyte does not break during stretching and compression. Specifically, the crystallinity of the polymer can be, but is not limited to, 30%, 35%, 40%, 45%, or 50%. In one embodiment of the present application, the crystallinity of the polymer can be 30%-40%. In another embodiment of the present application, the crystallinity of the polymer can be 40%-50%.

[0045] In one embodiment of the present application, the mass percentage of the polymer in the polymer electrolyte is 35%-45%. The appropriate polymer content can improve the mechanical properties of the polymer electrolyte, which is beneficial to improving the safety of the battery. Specifically, the mass percentage of the polymer in the polymer electrolyte can be, but is not limited to, 35%, 38%, 40%, 42%, 44% or 45%. In one embodiment of the present application, the mass percentage of the polymer in the polymer electrolyte can be 35%-42%. In another embodiment of the present application, the mass percentage of the polymer in the polymer electrolyte can be 40%-45%.

[0046] In one embodiment of the present application, the electrolyte salt may include, but is not limited to, a lithium salt, which can improve the electrochemical performance of the lithium-ion battery. Specifically, the lithium salt may include, but is not limited to, one or more of lithium fluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium hexafluorosilicate (LiSiF6), lithium tetraphenylborate (LiB(C6H5)4), lithium chloride (LiCl), lithium bromide (LiBr), lithium chloroaluminate (LiAlCl4), lithium fluoroalkylsulfonate (LiC(SO2CF3)3), lithium methanesulfonate (LiCH3SO3), lithium bis(trifluoromethanesulfonyl)imide (LiN(SO2CF3)2), and lithium bis(pentafluoroethylsulfonyl)imide (LiN(SO2C2F5)2). In one embodiment of the present application, the lithium salt may be lithium bis(pentafluoroethylsulfonyl)imide, which can further improve the room temperature ionic conductivity of the polymer electrolyte. In another embodiment of the present application, the lithium salt may be lithium hexafluorophosphate.

[0047] In one embodiment of the present application, when the electrolyte salt is a lithium salt, the numerical ratio of the lithium ions in the lithium salt to the oxygen atoms in the polymer is 1:(6-40). The lithium ions react with the oxygen atoms in the polymer, especially the oxygen atoms in the side chain position, so that the oxygen atoms migrate in the polymer, thereby improving the ionic conductivity of the polymer electrolyte. The numerical ratio of the lithium ions in the suitable lithium salt to the oxygen atoms in the polymer can have both high carrier density and low impedance of the polymer electrolyte, which is beneficial to improving the ionic conductivity of the polymer electrolyte. Specifically, the numerical ratio of the lithium ions in the lithium salt to the oxygen atoms in the polymer can be, but is not limited to, 1:6, 1:6, 1:8, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35 or 1:40, etc. In one embodiment of the present application, the numerical ratio of the lithium ions in the lithium salt to the oxygen atoms in the polymer can be 1:(8-10), which is beneficial to further improve the ionic conductivity of the polymer electrolyte.

[0048] In one embodiment of the present application, the mass percentage of the electrolyte salt in the polymer electrolyte is 25%-35%. Suitable electrolyte salts can improve the ionic conductivity of the polymer electrolyte. Specifically, the mass percentage of the electrolyte salt in the polymer electrolyte can be, but is not limited to, 25%, 28%, 30%, 32%, 34% or 35%. In one embodiment of the present application, the mass percentage of the electrolyte salt in the polymer electrolyte can be 25%-33%. In another embodiment of the present application, the mass percentage of the electrolyte salt in the polymer electrolyte can be 30%-35%.

[0049] In one embodiment of the present application, the polymer electrolyte further comprises a plasticizer, and the mass percentage of the plasticizer is 25%-35%. An appropriate amount of plasticizer can reduce the crystallinity of the polymer and improve the ionic conductivity and mechanical strength of the polymer electrolyte. Specifically, the plasticizer can include, but is not limited to, one or more of ethylene carbonate, propylene carbonate, and vinylene carbonate, and the mass percentage of the plasticizer can be, but is not limited to, 25%, 28%, 30%, 32%, 34%, or 35%, etc. In one embodiment of the present application, the plasticizer can be vinylene carbonate, and the mass percentage of the plasticizer can be 25%-33%. In another embodiment of the present application, the plasticizer can be propylene carbonate, and the mass percentage of the plasticizer can be 30%-35%.

[0050] In one embodiment of the present application, the polymer electrolyte further comprises an inorganic filler, and the mass percentage of the inorganic filler is 1.5%-2.5%. Suitable inorganic fillers can reduce the crystallinity of the polymer, thereby improving the ionic conductivity of the polymer electrolyte. Specifically, the inorganic filler can include, but is not limited to, one or more of silicon dioxide, aluminum oxide, and titanium dioxide, and the mass percentage of the inorganic filler can be, but is not limited to, 1.5%, 1.8%, 2%, 2.1%, 2.3%, or 2.5%. In one embodiment of the present application, the inorganic filler can be silicon dioxide, and the mass percentage of the inorganic filler can be 1.5%-2%. In another embodiment of the present application, the inorganic filler can be titanium dioxide, and the mass percentage of the inorganic filler can be 1.9%-2.5%.

[0051] In one embodiment of the present application, the ionic conductivity of the polymer electrolyte is greater than or equal to 10 -4 S / cm, at this time, the ionic conductivity is the ionic conductivity of the polymer electrolyte at 25°C. Specifically, the ionic conductivity of the polymer electrolyte can be, but is not limited to, greater than or equal to 10 -4 S / cm, greater than or equal to 2×10 -4 S / cm, greater than or equal to 4×10 -4 S / cm, greater than or equal to 6×10 -4 S / cm, greater than or equal to 8×10 -4 S / cm, greater than or equal to 10 -3 S / cm or greater than or equal to 4×10 -3 S / cm, etc. In one embodiment of the present application, the ionic conductivity of the polymer electrolyte is greater than or equal to 2×10 -4 In another embodiment of the present application, the ionic conductivity of the polymer electrolyte is greater than or equal to 8×10 -4 S / cm.

[0052] In one embodiment of the present application, when the polymer electrolyte is a film-like solid electrolyte, the polymer electrolyte can be used as a battery separator, and the strain recovery rate of the polymer electrolyte is 75%-85%. The strain recovery rate is the percentage of the maximum deformation under stress that is recovered after the stress disappears when the polymer electrolyte deforms under stress. Specifically, the strain recovery rate of the polymer electrolyte can be, but is not limited to, 75%, 77%, 79%, 80%, 82%, 84% or 85%. In one embodiment of the present application, the strain recovery rate of the polymer electrolyte can be 75%-82%. In another embodiment of the present application, the strain recovery rate of the polymer electrolyte can be 78%-85%.

[0053] This application provides a method for preparing a polymer electrolyte, comprising: mixing a polymer and an electrolyte salt solution, and drying to obtain the polymer electrolyte. The method for preparing the polymer electrolyte provided herein is novel and simple in preparation. The resulting polymer electrolyte exhibits high ionic conductivity and excellent mechanical properties, thereby improving battery safety and cycle stability.

[0054] In one embodiment of the present application, the preparation method of the polymer comprises: mixing a first structural unit monomer and a second structural unit monomer, and obtaining a polymer after polymerization reaction, wherein the structural formula of the first structural unit monomer is The structural formula of the second structural unit monomer is Wherein, R1, R2, R3, R4, R5 and R6 are the same or different polyether groups. The similar structure of the first structural unit monomer and the second structural unit monomer can cause the chain segments to aggregate in the short-range space, and do not aggregate in the long-range space due to the irregularity of the main chain structure, thereby forming a polymer with short-range order and long-range disorder, reducing the crystallinity of the polymer and improving the deformation resistance of the polymer. In one embodiment of the present application, the first structural unit monomer can be benzothiophene-p-thiophene polyvinyl ether, and the second structural unit monomer can be thiophene-p-benzoquinone-thiophene polyvinyl ether. The structural formula of the formed polymer is R1, R2, R3, R4, R5 and R6 are the same or different polyether groups.

[0055] In one embodiment of the present application, the molar ratio of the first structural unit monomer and the second structural unit monomer is (4-6): (3-5), a suitable molar ratio, so that the polymer has both higher mechanical properties and excellent ionic conductivity. Specifically, the molar ratio of the first structural unit monomer and the second structural unit monomer can be, but is not limited to, 4:3, 4:4, 4:5, 5:3, 5:4, 5:5, 6:3, 6:4 or 6:5, etc. In one embodiment of the present application, the molar ratio of the first structural unit monomer and the second structural unit monomer can be 5:4. In another embodiment of the present application, the molar ratio of the first structural unit monomer and the second structural unit monomer can be 5:5.

[0056] In one embodiment of the present application, the polymerization reaction temperature is 100°C-150°C. A suitable reaction temperature can promote the formation of the polymer. Specifically, the polymerization reaction temperature can be, but is not limited to, 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C. In one embodiment of the present application, the polymerization reaction temperature can be 100°C-130°C. In another embodiment of the present application, the polymerization reaction temperature can be 130°C-150°C.

[0057] In one embodiment of the present application, the polymer and the electrolyte salt solution are mixed for a mixing time of 1 hour to 36 hours and a drying temperature of 45°C to 75°C. Appropriate mixing time and drying temperature can allow the electrolyte salt to fully contact the polymer, which is beneficial to improving the ionic conductivity of the polymer electrolyte. Specifically, the mixing time can be, but is not limited to, 1 hour, 5 hours, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, or 36 hours; the drying temperature can be, but is not limited to, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, or 75°C. In one embodiment of the present application, the mixing time can be 1 hour to 28 hours, the drying temperature can be 45°C to 60°C, and the electrolyte salt solution can be an ethyl acetate solution of a lithium salt. In another embodiment of the present application, the mixing time can be 20 hours to 36 hours, and the drying temperature can be 55°C to 75°C.

[0058] In one embodiment of the present application, before mixing the polymer and the electrolyte salt solution, the polymer and the inorganic filler are further stirred and mixed to form a mixture, and the stirring temperature is 100°C-150°C, which can improve the ionic conductivity and mechanical properties of the polymer electrolyte. Specifically, the stirring temperature can be, but is not limited to, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C. In one embodiment of the present application, the stirring temperature can be 100°C-130°C. In another embodiment of the present application, the stirring temperature can be 130°C-150°C. After stirring, the mixture is poured onto a glass sheet and dried in a vacuum oven at 120°C to obtain a first film.

[0059] In one embodiment of the present application, after mixing the polymer and the electrolyte salt solution, a plasticizer is added and the polymer electrolyte is obtained after swelling. The swelling time is greater than or equal to 2 hours, which is beneficial to improving the mechanical properties of the polymer electrolyte. Specifically, the swelling time can be, but is not limited to, greater than or equal to 2 hours, greater than or equal to 2.5 hours, greater than or equal to 3 hours, greater than or equal to 3.5 hours, greater than or equal to 4 hours, or greater than or equal to 5 hours. In one embodiment of the present application, the swelling time is greater than or equal to 3 hours. In another embodiment of the present application, the swelling time can be 4 hours.

[0060] The present application also provides a composite electrode, comprising the polymer electrolyte provided by any of the above embodiments. The composite electrode provided by the present application has a polymer electrolyte with high ionic conductivity and good mechanical properties, which improves the structural reliability and electrochemical performance of the composite electrode.

[0061] In one embodiment of the present application, a composite electrode sheet includes a current collector and an active material layer disposed on the surface of the current collector. The active material layer includes a polymer electrolyte, an active material, a conductive agent, and a binder. Specifically, the active material is a positive electrode active material or a negative electrode active material. The positive electrode active material may include, but is not limited to, one or more of LiFePO4, LiMnO2, LiNiO2, LiCoO2, LiVPO4F, LiFeO2, and ternary positive electrode active materials. The negative electrode active material may include, but is not limited to, one or more of natural graphite, artificial graphite, hard carbon, soft carbon, and lithium titanate. The conductive agent may include, but is not limited to, one or more of graphite, carbon fiber, carbon black, metal powder, metal oxide, and fiber. The binder may include, but is not limited to, one or more of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, and polyacrylate. In one embodiment of the present application, the polymer electrolyte has excellent mechanical strength and elasticity. During battery cycling, it can adapt to the volume change of the battery, inhibit the shedding of the active material layer, improve the structural stability of the composite electrode sheet, and can replace part or all of the binder in the active material layer.

[0062] In one embodiment of the present application, the preparation method of the composite electrode piece may be: the active material, the conductive agent, the solvent and the polymer are uniformly mixed, the mixture is poured on a polytetrafluoroethylene block to form a composite material, the composite material is coated on the surface of the current collector, and the composite electrode piece is obtained by vacuum heating to 120°C-170°C. In one embodiment of the present application, 35% by weight of the active material (lithium iron phosphate), 5% by weight of the conductive agent (single-walled carbon nanotubes), 45% by weight of the polymer and the solvent (N-methylpyrrolidone) are mixed, the mixture is poured on a polytetrafluoroethylene block, and the composite electrode piece is obtained by vacuum heating to 150°C overnight.

[0063] The present application also provides a battery comprising the polymer electrolyte described in any of the above embodiments or the composite electrode described in any of the above embodiments. The battery provided in the present application has excellent electrochemical performance, long cycle life, and high safety performance, which is conducive to the industrial application of the battery.

[0064] See also Figure 1 , is a schematic diagram of the cross-sectional structure of a battery provided in one embodiment of the present application, wherein the battery 100 includes a positive electrode sheet 10 and a negative electrode sheet 12, and a polymer electrolyte 11 disposed between the positive electrode sheet 10 and the negative electrode sheet 12. In one embodiment of the present application, a solution containing a polymer electrolyte can be coated on the surface of the positive electrode sheet and / or the negative electrode sheet, dried to form a polymer electrolyte membrane, and then the positive electrode sheet and / or the negative electrode sheet coated with the polymer electrolyte can be wound or stacked to form a core, and the core can be placed in a battery casing, and sealed, formed, sealed, and packaged to prepare a battery. In another embodiment of the present application, the polymer electrolyte is made into a polymer electrolyte membrane, and the polymer electrolyte membrane is placed on the surface of the positive electrode sheet or the negative electrode sheet, and wound or stacked to prepare a core, and the core can be placed in a battery casing, and sealed, formed, sealed, and packaged to prepare a battery. In another embodiment of the present application, the positive electrode sheet and / or negative electrode sheet coated with a polymer electrolyte can be wound or stacked with a polymer electrolyte membrane to prepare a pole core, and the pole core is placed in a battery casing, sealed, formed, sealed and packaged to prepare a battery.

[0065] The present application also provides an electric device, which includes the battery described in any of the above embodiments. The electric device provided by the present application has good cycle performance, high safety performance, and strong market competitiveness. Electric devices include vehicles, electronic devices, energy storage systems, etc., wherein the electronic devices may include, for example, mobile phones, tablets, watches, VR glasses, etc. In one embodiment of the present application, the battery can be used in vehicles, which can increase the service life and charging rate of the vehicle, increase the widespread application of new energy vehicles, and facilitate the construction of a green and environmentally friendly environment. In another embodiment of the present application, the battery can also be used in mobile phones, which can reduce the preparation cost of the battery and improve the safety of battery use. The above-mentioned battery of the present application can be provided in the electric device in the form of a single cell, a battery module, a battery pack, etc.

[0066] The effects of the technical solution of this application are further illustrated below through specific examples.

[0067] Example 1

[0068] The first structural unit monomer (R1, R2, R3, R4 are all and the second structural unit monomer (R5, R6 and R7 are The mixture is mixed in a chlorobenzene solvent and heated to 120°C to undergo a condensation reaction to obtain a polymer; wherein the first structural unit monomer is generated by the reaction of benzothiophene, a halide of thiophene and an ether monomer in the presence of a catalyst (chloride or hydroxide, etc.) and high temperature, and the second structural unit monomer is generated by the reaction of a halide of benzothiophenedione, a halide of thiophene and an ether monomer in the presence of a catalyst (chloride or hydroxide, etc.) and high temperature.

[0069] The polymer and inorganic filler (silicon dioxide with a particle size of 14 nm) are heated to 120°C and stirred to obtain a mixture, which is then poured onto a glass slide and dried in a vacuum oven at 120°C to obtain a first film. The film is immersed in an electrolyte salt solution (ethyl acetate solution of lithium salt) for 24 hours to swell, and then dried in a vacuum oven at 60°C to obtain a second film. The second film is transferred to a glove box in an argon environment and mixed with a plasticizer (propylene carbonate) to obtain a polymer electrolyte membrane.

[0070] Example 2

[0071] The difference from Example 1 is that in the first structural unit monomer, R1, R2, R3, and R4 are all In the second structural unit monomer, R5, R6 and R7 are

[0072] Example 3

[0073] The difference from Example 1 is that in the first structural unit monomer, R1, R2, R3, and R4 are all In the second structural unit monomer, R5, R6 and R7 are

[0074] Example 4

[0075] The difference from Example 1 is that in the first structural unit monomer, R1, R2, R3, and R4 are all In the second structural unit monomer, R5, R6 and R7 are

[0076] Example 5

[0077] The difference from Example 1 is that in the first structural unit monomer, R1, R2, R3, and R4 are all In the second structural unit monomer, R5, R6 and R7 are

[0078] Example 6

[0079] The difference from Example 1 is that in the first structural unit monomer, R1, R2, R3, and R4 are all In the second structural unit monomer, R5, R6 and R7 are

[0080] Example 7

[0081] The difference from Example 1 is that in the first structural unit monomer, R1, R2, R3, and R4 are all In the second structural unit monomer, R5, R6 and R7 are

[0082] Example 8

[0083] The difference from Example 1 is that in the first structural unit monomer, R1, R2, R3, and R4 are all In the second structural unit monomer, R5, R6 and R7 are

[0084] Example 9

[0085] The difference from Example 1 is that in the first structural unit monomer, R1, R2, R3, and R4 are all In the second structural unit monomer, R5, R6 and R7 are

[0086] Example 10

[0087] The difference from Example 1 is that in the first structural unit monomer, R1, R2, R3, and R4 are all In the second structural unit monomer, R5, R6 and R7 are

[0088] Example 11

[0089] The difference from Example 1 is that in the first structural unit monomer, R1, R2, R3, and R4 are all In the second structural unit monomer, R5, R6 and R7 are

[0090] Example 12

[0091] The difference from Example 1 is that in the first structural unit monomer, R1 is R2 and R3 are R4 is In the second structural unit monomer, R5 is R6 is and R7 is

[0092] Comparative Example 1

[0093] The difference from Example 1 is that 0.683 g of electrolyte salt (LiTFSI) and 1 g of polyethylene oxide (weight-average molecular weight of 400,000 g / mol) were added to an appropriate amount of anhydrous acetonitrile, stirred at room temperature for 24 h, cast into a film in polytetrafluoroethylene, and then vacuum-dried at 50°C for 48 h to obtain a polymer electrolyte.

[0094] Performance testing

[0095] The polymer electrolyte membranes prepared in Examples 1-12 and Comparative Example 1 were subjected to thermogravimetric analysis. The test process was as follows: the temperature was raised to 600° C. in a nitrogen atmosphere at a temperature rise rate of 20° C. / min using a TAG-SDTA851 instrument. The test results are shown in Table 1.

[0096] The crystallinity and glass transition temperature of the polymer electrolyte membranes prepared in Examples 1-12 and Comparative Example 1 were measured using a differential scanning calorimeter (DSC-Q2000) with indium standards for calibration. The sample weight ranged from 8 mg to 10 mg, and the temperature range was -70°C to 150°C. Both the heating and cooling rates were 10°C / min. The test results are shown in Table 1.

[0097] The polymer electrolyte membranes prepared in Examples 1-12 and Comparative Example 1 were tested for tensile strength and elongation at break using an Instron 5565 tensile and compression tester at a strain rate of 100% / min. The test results are shown in Table 1.

[0098] The polymer electrolyte membranes prepared in Examples 1-12 and Comparative Example 1 were subjected to electrochemical impedance spectroscopy (EIS) testing. The test frequency ranged from 1 MHz to 100 MHz, with a constant temperature and humidity chamber (20°C to 80°C) and a disturbance signal of 50 mV. The test results are shown in Table 1.

[0099] The conductivity of the polymer electrolyte membranes prepared in Examples 1-12 and Comparative Example 1 was tested. The test process was as follows: 2 A 0.4 mm thick polymer electrolyte membrane was placed between two parallel stainless steel sheets in a glove box to form a 2032 button cell. Testing was performed using a Shanghai Chenhua Instruments CHI660B electrochemical workstation over a frequency range of 1 kHz to 100 kHz at temperatures of -20°C, -15°C, 20°C, 50°C, 80°C, and 110°C. The bulk resistance (Rh) of the polymer electrolyte was calculated as the intersection of the Nyquist plot with the real axis. Ionic conductivity was calculated using the formula σ = I / (A·Rh), where σ is the ionic conductivity, I is the thickness of the polymer electrolyte membrane, and A is the contact area between the polymer electrolyte membrane and the electrode. The test results are shown in Table 1.

[0100] The polymer electrolyte membranes prepared in Examples 1-12 and Comparative Example 1 were subjected to electrochemical stability testing. The following testing procedure was used: In an argon-filled glove box, the polymer electrolyte was placed between parallel lithium metal sheets and stainless steel sheets to form a 2032 button cell. Cyclic voltammetry was performed, with the voltage sweep from the open circuit voltage down to -0.7 V and then up to 5.5 V at a rate of 1 mV / s. The test results are shown in Table 1.

[0101] Table 1 Performance test results

[0102]

[0103] According to Examples 1-12 and Comparative Example 1, it can be seen that the polymer electrolyte provided by this application has a high thermal decomposition temperature, a high glass transition temperature, and a low degree of crystallinity, which improves the tensile strength, elongation at break, and strain recovery rate of the polymer electrolyte, so that the polymer electrolyte has both excellent mechanical properties and high ionic conductivity, thereby improving the electrochemical performance of the battery. According to Examples 1 and 2-12, it can be seen that a suitable side chain structure can further improve the mechanical strength and ionic conductivity of the polymer electrolyte. According to Example 1 and Comparative Example 1, it can be seen that compared with traditional electrolytes, the polymer electrolyte provided by this application has higher ionic conductivity and lower electrochemical impedance, and the mechanical properties are better than those of traditional electrolytes, which is conducive to improving the structural reliability and safety performance of the battery.

[0104] The above is a preferred embodiment of the present application, but it should not be construed as limiting the scope of the present application. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present application, and such improvements and modifications are also considered to be within the scope of protection of the present application.

Claims

1. A polymer electrolyte, characterized in that The polymer electrolyte comprises a polymer and an electrolyte salt, and the polymer has a structural formula of The first structural unit and structural formula are The second structural unit is polymerized, wherein R1, R2, R3, R4, R5 and R6 are the same or different polyether groups, R7 is selected from 、 、 、 、 、 and .

2. The polymer electrolyte according to claim 1, wherein The polyether group is or , M1 and M2 are selected from hydrogen atoms or alkyl groups, and n1 and n2 are selected from integers ranging from 1 to 100.

3. The polymer electrolyte according to claim 1, wherein The molar percentage of the first structural unit is 10%-90%, and the molar percentage of the second structural unit is 10%-90%.

4. The polymer electrolyte according to claim 1, wherein The weight average molecular weight of the polymer is 6×10 5 g / mol-2×10 6 g / mol, and the crystallinity of the polymer is 30%-50%.

5. The polymer electrolyte according to claim 1, wherein The electrolyte salt includes a lithium salt; The lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorosilicate, lithium tetraphenylborate, lithium chloride, lithium bromide, lithium chloroaluminate, lithium fluoroalkylsulfonate, lithium methanesulfonate, lithium bis(trifluoromethanesulfonyl)imide and lithium bis(pentafluoroethylsulfonyl)imide.

6. The polymer electrolyte according to claim 5, wherein The ratio of the number of lithium ions in the lithium salt to the number of oxygen atoms in the polymer is 1:(6-40).

7. The polymer electrolyte according to claim 1, wherein In the polymer electrolyte, the mass percentage of the polymer is 35%-45%, and the mass percentage of the electrolyte salt is 25%-35%.

8. The polymer electrolyte according to claim 1, wherein The polymer electrolyte further comprises an inorganic filler and a plasticizer; The inorganic filler includes one or more of silicon dioxide, aluminum oxide and titanium dioxide; The plasticizer includes one or more of ethylene carbonate, propylene carbonate and vinylene carbonate; The mass percentage of the plasticizer is 25%-35%, and the mass percentage of the inorganic filler is 1.5%-2.5%.

9. The polymer electrolyte according to claim 1, wherein The ionic conductivity of the polymer electrolyte is greater than or equal to 10 -4 S / cm.

10. A method for preparing a polymer electrolyte according to any one of claims 1 to 9, characterized in that: include: The polymer and electrolyte salt solution are mixed and dried to obtain a polymer electrolyte.

11. The preparation method according to claim 10, characterized in that The preparation method of the polymer comprises: The structural formula is The first structural unit monomer and the structural formula are The second structural unit monomers are mixed and polymerized to obtain a polymer; wherein R1, R2, R3, R4, R5 and R6 are the same or different polyether groups, and R7 is selected from 、 、 、 、 、 and .

12. The preparation method according to claim 11, characterized in that The molar ratio of the first structural unit monomer to the second structural unit monomer is (4-6): (3-5); The polymerization reaction temperature is 100°C-150°C.

13. A composite pole piece, characterized in that: The composite electrode comprises the polymer electrolyte described in any one of claims 1 to 9 or the polymer electrolyte prepared by the preparation method described in any one of claims 10 to 12.

14. A battery, characterized in that: The battery comprises the polymer electrolyte according to any one of claims 1 to 9, or the polymer electrolyte prepared by the preparation method according to any one of claims 10 to 12, or the composite electrode according to claim 13.

15. An electrical device, characterized in that: The electric device comprises the battery according to claim 14.

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