A polymer for electrolyte and its preparation method and application

Abstract

The present invention provides a polymer for electrolyte and a preparation method and application thereof, which is a homopolymer and / or alternating polymer and / or block polymer and / or grafted polymer and / or random polymer composed of repeating units shown in formula (1). The electrolyte containing the polymer of the present invention has higher segment mobility than general polyether electrolytes, thereby significantly improving the ionic conductivity of the polymer electrolyte. At the same time, the ionic conductivity of the polymer electrolyte can be further improved by using a lithium salt that is more easily dissociated. #imgabs0#

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolyte materials, and in particular relates to a polymer for electrolyte, a polymer electrolyte and a preparation method thereof, a composite solid electrolyte, a composite electrolyte, a composite electrolyte solution and a secondary battery. Background Art

[0002] The growing development of new energy industries such as consumer electronics, electric vehicles, and power station energy storage has put forward higher requirements for the safety and energy density of secondary batteries. At present, the liquid electrolytes in secondary batteries are flammable, explosive, and easy to erupt under conditions of failure or abuse, causing certain safety issues when using secondary batteries. Therefore, how to improve the safety performance of liquid electrolytes is a problem that needs to be solved. Solid electrolytes have the characteristics of higher thermal decomposition temperature and less prone to eruption, so they are one of the current research directions to significantly improve the safety of lithium batteries.

[0003] Common solid electrolytes are divided into oxides, sulfides and polymer electrolytes. Among them, polymer electrolytes have better performance than oxide and sulfide electrolytes, mainly in the following aspects: 1. The interface contact performance of polymer electrolytes is significantly better than that of oxide and sulfide electrolytes, so its interface impedance is small; 2. Polymers do not react in the air and have stable performance; and unlike sulfide solid electrolytes and garnet oxide solid electrolytes, polymer electrolytes are not easy to decompose when exposed to water, so they have higher safety performance; 3. Polymer electrolytes have good mechanical properties and are easy to process, which is conducive to large-scale production and application; 4. Polymer electrolytes have high stability to low-potential negative electrodes (such as metal lithium negative electrodes).

[0004] However, currently commonly used polymer electrolyte materials such as polyethylene oxide and polyether polymers not only have poor oxidation resistance, but are also not suitable for high-voltage battery systems (including lithium cobalt oxide positive electrode materials, ternary positive electrode materials, nickel manganese positive electrode materials, lithium-rich positive electrode materials and other positive electrode systems), resulting in low energy density of secondary batteries containing polymer electrolytes, which is not conducive to commercial use.

[0005] An existing polyalkylene ether polymer has improved compatibility with lithium cobalt oxide high-voltage positive electrode materials, but is not suitable for charging to high voltage, so the positive electrode capacity cannot be fully utilized. As for polymer electrolyte materials of polyacrylonitrile, polyvinyl carbonate and polyvinyl ethylene carbonate, although the oxidation resistance is improved compared with the commonly used polyethylene oxide and polyether polymers, there are still problems such as low ion conductivity, low solubility of lithium salts and / or sodium salts, and / or fewer types of matching lithium salts. Therefore, the above unfavorable factors limit the application of polymer solid electrolytes. Summary of the invention

[0006] In view of the performance deficiencies of the current polymer electrolytes, the technical problem to be solved by the present invention is to overcome the defects of the prior art polymer electrolytes such as poor oxidation resistance, unsuitability for high-voltage battery systems, low ionic conductivity, low solubility of lithium salts and / or sodium salts, and / or a small number of matching lithium salt types, and to provide a polymer for electrolyte, a polymer electrolyte and its preparation method, a composite solid electrolyte, a composite electrolyte, a composite electrolyte and a secondary battery with better performance.

[0007] 1. Polymers for Electrolytes

[0008] The first aspect of the present invention provides a polymer for electrolyte, which is a homopolymer and / or alternating polymer and / or block polymer and / or grafted polymer and / or random polymer composed of repeating units represented by formula (1):

[0009]

[0010] in:

[0011] R 1 , R 2 , R 3 , R 4 , R 5 and R 6 Each independently selected from C1-C20 alkylene, C1-C20 alkylene fully or partially substituted by halogen, C1-C20 alkylene fully or partially substituted by silicon

[0012] Atom-substituted C1-C20 alkylene, where R 1 , R 2 , R 3 , R 4 , R 5 and R 6 At least one of the comprises a halogen atom;

[0013] k, l, m, n, o and p are each independently an integer from 0 to 100, q is an integer from 1 to 300000, and (k+l+m+n+o+p)×q>3.

[0014] Preferably, (k+l+m+n+o+p)×q is between 3000 and 3000000; more preferably, (k+l+m+n+o+p)×q is between 10000 and 2000000; particularly preferably, (k+l+m+n+o+p)×q is between 30000 and 1500000.

[0015] In the repeating unit represented by formula (1), * represents an end group. In the polymer provided by the present invention, the end group may be one or more of ether, alcohol, ester, carbonate, carboxylic acid, aldehyde, ketone, C1-C20 alkyl, C1-C20 alkenyl, C1-C20 halogenated hydrocarbon group.

[0016] In a preferred embodiment of the present invention, q is an integer of 3,000 to 300,000.

[0017] In some embodiments of the present invention, R 1 , R 2 , R 3 , R 4 , R 5 and R 6 Each is independently selected from the structures of formula (1a) to formula (1j):

[0018]

[0019] Among them, each R x Each is independently silicon or carbon, and each X is independently hydrogen, a halogen or a repeating unit represented by formula (1).

[0020] In a preferred embodiment of the present invention, R 1 , R 2 , R 3 , R 4 , R 5 and R 6 The total molar percentage of X being halogen is between 1% and 50%, that is, among the total X substituents, 1% to 50% by mole of X is halogen.

[0021] In the structures of Formula (1a) to (1j), the dashed lines represent dangling bonds to the polymer backbone.

[0022] In some embodiments of the present invention, the polymer has one of the structures shown in formula (2a) to formula (2h):

[0023]

[0024]

[0025] wherein X is selected from hydrogen or halogen, and

[0026] In formula (2a), k×q is greater than 3; in formula (2b) and formula (2d) to formula (2h), (k+l)×q is greater than 3; in formula (2c), (k+l+m)×q is greater than 3.

[0027] In a preferred embodiment of the present invention, in formula (2a), k×q is between 3000 and 3000000; in formula (2b) and formula (2d) to formula (2h), (k+l)×q is between 3000 and 3000000; in formula (2c), (k+l+m)×q is between 3000 and 3000000.

[0028] In a more preferred embodiment of the present invention, in formula (2a), k×q is between 10,000 and 2,000,000; in formulas (2b) and (2d) to (2h), (k+l)×q is between 10,000 and 2,000,000; and in formula (2c), (k+l+m)×q is between 10,000 and 2,000,000.

[0029] In a particularly preferred embodiment of the present invention, in formula (2a), k×q is between 30,000 and 1,500,000; in formulas (2b) and (2d) to (2h), (k+l)×q is between 30,000 and 1,500,000; and in formula (2c), (k+l+m)×q is between 30,000 and 1,500,000.

[0030] In other embodiments of the present invention, the polymer has one of the structures shown in formula (3a) to formula (3f):

[0031]

[0032]

[0033] Among them, k, l, and m are not 0 at the same time, and

[0034] In formula (3a), k×q is greater than 3; in formula (3b) and formula (3d) to formula (3h), (k+l)×q is greater than 3; in formula (3c), (k+l+m)×q is greater than 3.

[0035] In a preferred embodiment of the present invention, in formula (3a), k×q is between 3000 and 3000000; in formula (3b) and formula (3d) to formula (3h), (k+l)×q is between 3000 and 3000000; in formula (3c), (k+l+m)×q is between 3000 and 3000000.

[0036] In a more preferred embodiment of the present invention, in formula (3a), k×q is between 10,000 and 2,000,000; in formulas (3b) and (3d) to (3h), (k+l)×q is between 10,000 and 2,000,000; and in formula (3c), (k+l+m)×q is between 10,000 and 2,000,000.

[0037] In a particularly preferred embodiment of the present invention, in formula (3a), k×q is between 30,000 and 1,500,000; in formulas (3b) and (3d) to (3h), (k+l)×q is between 30,000 and 1,500,000; and in formula (3c), (k+l+m)×q is between 30,000 and 1,500,000.

[0038] 2. Preparation method of polymer for electrolyte

[0039] The second aspect of the present invention provides a method for preparing the above polymer for electrolyte, the method comprising preparing or preparing a precursor, and obtaining the polymer by a gas phase synthesis method.

[0040] In some embodiments of the present invention, the preparation method comprises the following steps:

[0041] (1) mixing the precursors and optionally activating them by preheating;

[0042] (2) The precursor obtained in step (1) is heated to perform gas phase synthesis, and the polymer for electrolyte is obtained after drying.

[0043] Preferably, the preheating temperature in step (1) is 40-400°C, for example, it can be 40°C, 60°C, 80°C, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, 220°C, 240°C, 260°C, 280°C, 300°C, 320°C, 340°C, 360°C, 380°C, 400°C; the preheating time is 1-30min, for example, it can be 1min, 2min, 4min, 6min, 8min, 10min, 12min, 14min, 16min, 18min, 20min, 22min, 24min, 26min, 28min, 30min.

[0044] In various embodiments of the present invention, the precursor may include, but is not limited to, any one or more combinations of amide compounds, cycloalkane compounds, alkylene oxide compounds, cyclic ketone compounds, cyclic vinyl ester compounds, fluorine-containing compounds, chlorine-containing compounds, silicate compounds, ether compounds, cyclic ether compounds, cyclic ester compounds, silicate compounds, and acid compounds.

[0045] In some specific embodiments of the present invention, the precursor may include but is not limited to: 1,3-dioxolane, 1,3-cyclopentanedione, 1,4-dioxane, 1,4-dioxacyclo-2,5-hexanedione, 1,4-cyclohexanedione, 2-fluoroethylene oxide, 2,2-difluoroethylene oxide, 2,3-difluoroethylene oxide, epifluoropropane, difluoroethylene carbonate, diethylaminosulfur trifluoride, trifluoropropyltrichlorosilane, tetrafluoroboric acid, A combination of two or more of hexafluorophosphoric acid, hexafluorotitanic acid, fluoroethylene carbonate, ethylene oxide, thionyl chloride, phosphoric acid, sulfuric acid, boric acid, polytetrafluoroethylene powder, fluorosilicic acid, hydrofluoric acid, trifluoromethyl carbonate, stannous octoate, ethylene glycol dimethyl ether, glycolaldehyde dimer, glycolide, N-fluorobisbenzenesulfonamide, 1-chloromethyl-4-fluoro-1,4-diazobicyclo-2.2.2octane bis(tetrafluoroborate), silicon dioxide, and sulfur tetrafluoride.

[0046] According to the preparation method provided by the present invention, the heating temperature in step (2) can be 40-400°C, for example, it can be 40°C, 60°C, 80°C, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, 220°C, 240°C, 260°C, 280°C, 300°C, 320°C, 340°C, 360°C, 380°C, or 400°C.

[0047] Preferably, the gas phase synthesis in step (2) comprises vacuum evaporation or vapor deposition. In some embodiments of the present invention, a gas is introduced during the vacuum evaporation or vapor deposition process. The gas includes but is not limited to ethylene oxide-containing gas, halogen-containing gas or ozone.

[0048] Preferably, the halogen-containing gas includes but is not limited to 1,1-dichloro-2,2-difluoroethylene, 2-chloro-1,2-dibromo-1,1,2-trifluoroethane, chlorotrifluoroethylene, nitrogen trifluoride, trifluoromethyl trifluorovinyl ether, carbon tetrafluoride, sulfur hexafluoride, hexafluoropropylene oxide, octafluorocyclobutane, trans-1,1,1,3-tetrafluoropropylene, fluorine gas, sulfuryl fluoride, hydrogen chloride gas, chlorine gas, hydrofluoric acid gas, isoflurane and one or more combinations thereof.

[0049] Preferably, a solid catalyst is used in the process of vacuum evaporation or vapor deposition. The solid catalyst may include one or more of oxides, silicic acid compounds, boric acid compounds, and metal catalysts.

[0050] Preferably, the solid catalyst includes but is not limited to a combination of one or more of silicon dioxide, manganese dioxide, aluminum oxide, boron oxide, lithium tetraborate, sodium tetraborate, silicic acid, silicates, boric acid, borates, cobalt oxide, copper oxide, zinc oxide, iron oxide, nickel oxide, manganese oxide, calcium oxide, silver, platinum, gold, iron, cobalt, nickel, molybdenum, niobium, magnesium, aluminum, titanium, zinc, and calcium.

[0051] 3. Electrolyte polymer

[0052] The third aspect of the present invention provides a polymer electrolyte, which comprises the polymer provided by the present invention or the polymer obtained according to the preparation method of the present invention, and a lithium salt and / or a sodium salt, wherein the mass percentage of the polymer in the polymer electrolyte is 5% to 99%, and the mass percentage of the lithium salt and / or the sodium salt in the polymer electrolyte is 1% to 95%.

[0053] In various embodiments of the present invention, the mass percentage of the polymer in the polymer electrolyte can vary in the range of 5% to 99%, for example, 5%, 7%, 10%, 12%, 15%, 17%, 20%, 22%, 25%, 27%, 30%, 32%, 35%, 37%, 40%, 42%, 45%, 47%, 50%, 52%, 55%, 57%, 60%, 62%, 65%, 67%, 70%, 72%, 75%, 77%, 80%, 82%, 85%, 87%, 90%, 92%, 95%, 97%, 99%; the mass percentage of the lithium salt in the polymer electrolyte can vary in the range of 1% to 95%, for example, it can be 1%, 3%, 5%, 7%, 10%, 12%, 15%, 17%, 20%, 22%, 25%, 27%, 30%, 32%, 35%, 37%, 40%, 42%, 45%, 47%, 50%, 52%, 55%, 57%, 60%, 62%, 65%, 67%, 70%, 72%, 75%, 77%, 80%, 82%, 85%, 87%, 90%, 92%, 95%.

[0054] According to the polymer electrolyte provided by the present invention, the lithium salt may be a combination of one or more of an organic lithium salt and an inorganic lithium salt; the sodium salt may be a combination of one or more of an organic sodium salt and an inorganic sodium salt.

[0055] Preferably, the organic lithium salt can be selected from one or more of 1,2,3,4,5-pentatrifluoromethylcyclopentadiene lithium, difluorooxalato lithium borate, N-trifluoromethyl-trifluoroacetamide lithium, bisoxalato lithium borate, bistrifluoromethylsulfonyl imide lithium, bisfluorosulfonyl imide lithium, trifluoromethylsulfonate, trinitromethyl lithium, tetrakis((trifluoromethyl)sulfonyl)borate lithium, tetrakis(trifluoromethyl)borate lithium, tetramethyl lithium borate, tetrakis(perfluoro-tert-butoxy)aluminate lithium, tetraethyl lithium borate, tetranitrile lithium borate, hexa(trifluoromethyl)aluminate lithium, hexa(trifluoromethyl)phosphate lithium, and dodecafluorododecanoate lithium; the inorganic lithium salt can be selected from one or more of lithium tetrafluoroborate, lithium hexafluorophosphate, and lithium perchlorate.

[0056] According to the polymer electrolyte provided by the present invention, the sodium salt may be one or more of an organic sodium salt and an inorganic sodium salt.

[0057] Preferably, the organic sodium salt can be selected from one or more of sodium bis(trifluoromethylsulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium bis(oxalatoborate), sodium difluorooxalatoborate; the inorganic sodium salt can be selected from one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, and sodium iodide.

[0058] 4. Preparation method of electrolyte polymer

[0059] A fourth aspect of the present invention provides a method for preparing a polymer electrolyte, comprising:

[0060] Mixing the polymer with lithium salt and / or sodium salt, dissolving the mixture in a solvent to obtain a solid electrolyte slurry, and drying the mixture to obtain the polymer electrolyte; or

[0061] The polymer electrolyte is prepared by electrospinning the polymer and lithium salt and / or sodium salt.

[0062] The polymer is the polymer provided by the present invention or the polymer obtained according to the preparation method of the present invention.

[0063] In a preferred embodiment of the present invention, the polymer electrolyte is in the form of a film.

[0064] Preferably, the drying is vacuum drying, and the temperature of the vacuum drying is 40-400°C, for example, 40°C, 60°C, 80°C, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, 220°C, 240°C, 260°C, 280°C, 300°C, 320°C, 340°C, 360°C, 380°C, 400°C.

[0065] According to the preparation method of the polymer electrolyte provided by the present invention, the solvent may be an organic solvent and / or an inorganic solvent. Preferably, the organic solvent includes but is not limited to one or more of N,N-dimethylformamide, dichloromethane, dimethyl sulfoxide, carbon tetrachloride, methyl isobutyl ketone, ethanol, acetonitrile, ethyl acetate, butyl acetate, acetone, pentane, cyclohexane, petroleum ether, isopropanol, and n-heptane. The inorganic solvent may be deionized water.

[0066] According to the method for preparing the polymer electrolyte provided by the present invention, the electrospinning method may include the following steps:

[0067] The polymer and the solution are stirred and mixed to form a spinning solution, and the spinning solution is transferred to a syringe;

[0068] Voltage is applied between the syringe needle and the substrate to slowly extrude the spinning solution to form a thin film on the substrate.

[0069] The solution comprises lithium salt and / or sodium salt, a solvent and an optional thickener.

[0070] 5. Composite solid electrolyte

[0071] The fifth aspect of the present invention provides a composite solid electrolyte, which comprises the polymer provided by the first aspect of the present invention, the polymer obtained by the preparation method provided by the second aspect of the present invention, the polymer electrolyte provided by the third aspect of the present invention, or the polymer electrolyte obtained by the preparation method provided by the fourth aspect of the present invention, and at least one additional inorganic solid electrolyte and / or organic solid electrolyte.

[0072] The mass percentage of the polymer or polymer electrolyte of the present invention in the composite solid electrolyte can be 0.5% to 99%, and the mass percentage of the inorganic solid electrolyte and / or organic solid electrolyte in the composite solid electrolyte can be 0.5% to 99%. Preferably, the mass percentage of the polymer electrolyte in the composite solid electrolyte is 1% to 98%, and the mass percentage of the inorganic solid electrolyte and / or organic solid electrolyte in the composite solid electrolyte is 1% to 98%.

[0073] Preferably, when the composite solid electrolyte comprises the polymer electrolyte provided in the third aspect of the present invention or the polymer electrolyte obtained by the preparation method provided in the fourth aspect of the present invention, the mass percentage of the lithium salt and / or sodium salt in the polymer electrolyte in the composite solid electrolyte may be 0.5% to 99%.

[0074] According to the composite solid electrolyte provided by the present invention, in some embodiments, the inorganic solid electrolyte can be an inorganic nano-oxide, for example, one or more of silicon dioxide, manganese dioxide, cerium dioxide, titanium dioxide, lanthanum trioxide, and aluminum trioxide.

[0075] In other embodiments, the inorganic solid electrolyte may be one or more of a NASICON-type solid electrolyte, a perovskite-type solid electrolyte, or a garnet-type solid electrolyte. Preferably, the NASICON-type solid electrolyte includes but is not limited to Li 1.3 A1 0.3 Ti 1.7 (PO 4 ) 3 , Li 1.4 A1 0.4 Ti 1.6 (PO 4 ) 3 and Li1.5 A1 0.5 Ge 1.5 (PO 4 ) 3 ; The perovskite solid electrolyte includes but is not limited to Li 0.33 La 0.56 TiO 3 and / or Li 0.25 La 0.583 TiO 3 ; The garnet-type solid electrolyte includes but is not limited to Li 7 La 3 Zr 2 O 12 , Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 or Li 6.25 Al 0.25 La 3 Zr 2 O 12 One or more of .

[0076] According to the composite solid electrolyte provided by the present invention, the organic solid electrolyte includes one or more of an ether-based polymer electrolyte, an ester-based polymer electrolyte, a carbonate-based polymer electrolyte, a nitrile-based polymer electrolyte, and an alkyl-based polymer electrolyte.

[0077] Among them, the ether-based polymer electrolyte includes but is not limited to polyethylene oxide and polyethylene oxide; the ester-based polymer electrolyte includes but is not limited to polymethacrylate; the carbonate-based polymer electrolyte includes but is not limited to aliphatic polycarbonate; the nitrile-based polymer electrolyte includes but is not limited to polyacrylonitrile; the alkyl-based polymer electrolyte includes but is not limited to polyvinylidene fluoride, polytetrafluoroethylene, poly(vinylidene fluoride-co-hexafluoropropylene), and polyvinyl chloride.

[0078] According to the composite solid electrolyte provided by the present invention, the mass percentage of the polymer of the present invention in the composite solid electrolyte can vary in the range of 0.5% to 95%, for example, it can be 0.5%, 1%, 3%, 5%, 7%, 10%, 12%, 15%, 17%, 20%, 22%, 25%, 27%, 30%, 32%, 35%, 37%, 40%, 42%, 45%, 47%, 50%, 52%, 55%, 57%, 60%, 62%, 65%, 67%, 70%, 72%, 75%, 77%, 80%, 82%, 85%, 87%, 90%, 92%, 95%.

[0079] In addition, the mass percentage of the inorganic solid electrolyte or the organic solid electrolyte other than the polymer in the composite solid electrolyte can vary in the range of 0.5% to 95%, for example, it can be 0.5%, 1%, 3%, 5%, 7%, 10%, 12%, 15%, 17%, 20%, 22%, 25%, 27%, 30%, 32%, 35%, 37%, 40%, 42%, 45%, 47%, 50%, 52%, 55%, 57%, 60%, 62%, 65%, 67%, 70%, 72%, 75%, 77%, 80%, 82%, 85%, 87%, 90%, 92%, 95%.

[0080] The mass percentage of the lithium salt and / or sodium salt in the composite solid electrolyte can vary in the range of 0.5% to 95%, for example, it can be 0.5%, 1%, 3%, 5%, 7%, 10%, 12%, 15%, 17%, 20%, 22%, 25%, 27%, 30%, 32%, 35%, 37%, 40%, 42%, 45%, 47%, 50%, 52%, 55%, 57%, 60%, 62%, 65%, 67%, 70%, 72%, 75%, 77%, 80%, 82%, 85%, 87%, 90%, 92%, 95%.

[0081] Preferably, the mass percentage of the lithium salt and / or sodium salt in the composite solid electrolyte is 10% to 90%.

[0082] In a preferred embodiment of the present invention, the composite solid electrolyte is in the form of a film. Preferably, the composite solid electrolyte in the form of a film is prepared using a method including but not limited to a dissolution film forming method, a casting method, an electrostatic spinning method or a 3D printing casting method.

[0083] In one embodiment of the present invention, the preparation of the composite solid electrolyte membrane by the dissolution film forming method includes the preparation of a mixed solution, stirring and ultrasonic dispersion, and volatilization and drying.

[0084] Preferably, the preparation of the mixed solution comprises mixing the polymer of the present invention with a lithium salt or a sodium salt, and one or more other inorganic solid electrolytes and / or organic solid electrolytes in a solvent. Preferably, the solvent can be selected from one or more of N,N-dimethylformamide, dichloromethane, dimethyl sulfoxide, carbon tetrachloride, methyl isobutyl ketone, ethanol, acetonitrile, ethyl acetate, butyl acetate, acetone, pentane, cyclohexane, petroleum ether, isopropanol, n-heptane, and deionized water.

[0085] Preferably, the stirring and ultrasonic dispersion comprises using an ultrasonic cell pulverizer to simultaneously ultrasonicate and stir the mixed solution.

[0086] Preferably, the volatilization drying comprises pouring the mixed solution into a flat mold for volatilization, air drying and drying. Preferably, the drying comprises vacuum drying.

[0087] 6. Composite Electrolyte

[0088] The sixth aspect of the present invention provides a composite electrolyte, which comprises the polymer electrolyte provided by the third aspect of the present invention or the polymer electrolyte obtained by the preparation method provided by the fourth aspect of the present invention, and a plasticizer.

[0089] Wherein, the mass percentage of the plasticizer in the composite electrolyte is 0.1% to 50%.

[0090] According to the composite electrolyte provided by the present invention, the plasticizer can be selected from one or more of amide-based plasticizers, ether-based plasticizers, ester-based plasticizers, cyclic ester-based plasticizers, carbonate-based plasticizers, nitrile-based plasticizers, and cycloalkane-based plasticizers.

[0091] Preferably, the amide-based plasticizer includes, but is not limited to, one or more of acetamide, thioacetamide, sulfonamide, N,N-dimethylformamide, and formamide.

[0092] Preferably, the ether-based plasticizer includes, but is not limited to, one or more of dimethyl ether, diethyl ether, dipropyl ether, ethylene glycol dimethyl ether or methyl ethyl ether.

[0093] Preferably, the ester-based plasticizer includes, but is not limited to, one or more of ethylene glycol dimethacrylate, dimethyl oxalate, diethyl oxalate, methyl glycolate, ethylene glycol diacetate, ethylene glycol ethyl ether acetate or ethylene glycol diacrylate.

[0094] Preferably, the cyclic ester-based plasticizer includes, but is not limited to, one or more of hydroxymethyldioxolanone, 4-ethyl-1,3-dioxane-2-one or butyrolactone.

[0095] Preferably, the carbonate-based plasticizer includes, but is not limited to, one or more of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, methylpropyl carbonate, dibutyl carbonate, vinylene carbonate, fluoroethylene carbonate, vinylethylene carbonate, ethylene carbonate, propylene carbonate, isopropyl methyl carbonate, methyl acetate or ethyl acetate.

[0096] Preferably, the nitrile-based plasticizer includes but is not limited to acrylonitrile and succinonitrile.

[0097] Preferably, the cycloalkane-based plasticizer includes, but is not limited to, one or more of 1,3-dioxolane, 1,4-dioxane, and 1,4-dioxacyclo-2,5-hexanedione.

[0098] The mass percentage of the plasticizer in the composite electrolyte can vary in the range of 0.1% to 50%, for example, it can be 0.1%, 0.2%, 0.5%, 1%, 2%, 5%, 7%, 10%, 12%, 15%, 17%, 20%, 22%, 25%, 27%, 30%, 32%, 35%, 37%, 40%, 42%, 45%, 47%, 50%.

[0099] In some embodiments of the present invention, the method for preparing the composite electrolyte may include: during the process of using the polymer electrolyte provided by the third aspect of the present invention or the polymer electrolyte obtained by the preparation method provided by the fourth aspect of the present invention for battery assembly, dripping the plasticizer on the polymer electrolyte.

[0100] In other embodiments of the present invention, the method for preparing the composite electrolyte may include: after the polymer electrolyte provided by the third aspect of the present invention or the polymer electrolyte obtained by the preparation method provided by the fourth aspect of the present invention is used for battery assembly, before the battery is packaged, the plasticizer is injected into the battery.

[0101] 7. Composite electrolyte

[0102] The seventh aspect of the present invention provides a composite electrolyte, which comprises the polymer electrolyte provided by the third aspect of the present invention or the polymer electrolyte obtained by the preparation method provided by the fourth aspect of the present invention as an additive, and a main component of the electrolyte.

[0103] Preferably, the mass percentage of the polymer electrolyte in the composite electrolyte can be 0.1% to 50%, for example, it can be 0.1%, 0.2%, 0.5%, 1%, 2%, 5%, 7%, 10%, 12%, 15%, 17%, 20%, 22%, 25%, 27%, 30%, 32%, 35%, 37%, 40%, 42%, 45%, 47%, or 50%.

[0104] According to the composite electrolyte provided by the present invention, the main component of the electrolyte may include common electrolyte components such as carbonate-based electrolytes and ether-based electrolytes.

[0105] Preferably, the carbonate-based electrolyte can be selected from one of the following electrolytes: 1M LiPF 6 EC:DMC=1:1, 1M LiPF 6 EC:DMC:FEC=1:1:0.025, 1M LiPF 6 EC:DMC:VC=1:1:0.005, 1M LiPF 6EC:DMC:FEC:VC=1:1:0.025:0.005, 1M LiPF 6 EC: DMC: FEC: VC: PS: PST: LiDFOB=1: 1: 0.075: 0.025: 0.025: 0.025, 1M LiPF 6 EC:DMC=3:7, 1M LiPF 6 EC:DMC:FEC=3:7:0.025,1MLiPF 6 EC:DMC:DEC=1:1:1, 1M LiPF 6 EC: DMC: EMC=1:1:1, 1M LiPF 6 EC:DEC:EMC=1:1:1, 1M LiPF 6 EC:EMC=3:7、1M LiPF 6 EC:DEC=1:1.

[0106] Preferably, the ether-based electrolyte can be selected from one of the following electrolytes: 1M LiTFSI tetraethylene glycol dimethyl ether, 1M LiFSI tetraethylene glycol dimethyl ether, 1M LiTFSI diethylene glycol dimethyl ether, 1M LiFSI diethylene glycol dimethyl ether, 1M LiTFSIDOL:DME=1:1, 1MLiFSIDOL:DME=1:1, 0.5M LiCF 3 SO 3 0.5M LiNO 3 DME:DOL=1:1.

[0107] 8. Secondary batteries

[0108] The eighth aspect of the present invention provides a secondary battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte is at least one of the polymer electrolyte provided by the third aspect of the present invention, the polymer electrolyte obtained by the preparation method provided by the fourth aspect of the present invention, the composite solid electrolyte provided by the fifth aspect of the present invention, the composite electrolyte provided by the sixth aspect of the present invention, and the composite electrolyte provided by the seventh aspect of the present invention.

[0109] Preferably, the secondary battery is a lithium battery and / or a sodium battery.

[0110] Preferably, the positive electrode includes one or more of a lithium iron phosphate positive electrode, a ternary positive electrode, a lithium cobalt oxide positive electrode, a nickel manganese positive electrode, a lithium-rich positive electrode, a lithium manganate positive electrode, sodium vanadium phosphate, and sodium vanadium fluorophosphate.

[0111] In some embodiments of the present invention, the positive electrode can be a composite positive electrode composed of one or more of the polymer electrolyte provided by the third aspect of the present invention, the polymer electrolyte obtained by the preparation method provided by the fourth aspect of the present invention, the composite solid electrolyte provided by the fifth aspect of the present invention, the composite electrolyte provided by the sixth aspect of the present invention, and the composite electrolyte provided by the seventh aspect of the present invention and one or more of the above-mentioned positive electrode materials.

[0112] Preferably, the negative electrode includes one or more of a carbon negative electrode, a silicon negative electrode, a lithium negative electrode, a lithium titanate negative electrode, and an alloy negative electrode.

[0113] In some embodiments of the present invention, the negative electrode can be a composite negative electrode composed of one or more of the polymer electrolyte provided by the third aspect of the present invention, the polymer electrolyte obtained by the preparation method provided by the fourth aspect of the present invention, the composite solid electrolyte provided by the fifth aspect of the present invention, the composite electrolyte provided by the sixth aspect of the present invention, and the composite electrolyte provided by the seventh aspect of the present invention and one or more of the above-mentioned negative electrode materials.

[0114] Preferably, the carbon negative electrode comprises at least one of a graphite negative electrode and a non-graphite negative electrode. Preferably, the non-graphite negative electrode comprises at least one of a hard carbon negative electrode and a soft carbon negative electrode.

[0115] In some embodiments of the present invention, the surface of at least one of the positive electrode and the negative electrode also includes a coating layer formed by one or more of the polymer electrolyte provided by the third aspect of the present invention, the polymer electrolyte obtained by the preparation method provided by the fourth aspect of the present invention, the composite solid electrolyte provided by the fifth aspect of the present invention, the composite electrolyte provided by the sixth aspect of the present invention, and the composite electrolyte provided by the seventh aspect of the present invention.

[0116] The technical solution of the present invention has the following advantages:

[0117] The polymer for electrolyte provided by the first aspect of the present invention, by replacing the hydrogen atoms on the polyether segment with halogen atoms, can form a significant electron-withdrawing effect due to the strong electronegativity of the halogen atoms, that is, the above structure can reduce the mutual repulsion between different electrons of adjacent oxygen atoms, thereby reducing the energy of the molecular orbital energy level on the oxygen atom, and can improve the oxidation resistance of the polymer; when the silicon structure substituted by the halogen atoms contained in the polymer main chain can significantly enhance the above electron-withdrawing effect, it can significantly improve the oxidation resistance of the polymer material, so the electrolyte containing the polymer material can be suitable for the high-voltage positive electrode system in the secondary battery. The voltage resistance characteristics of the high-voltage system of the electrolyte containing the polymer material are manifested in a wider electrochemical window on the linear sweep voltammetric characteristic curve. It can be used with high-voltage high-capacity positive electrode materials such as lithium cobalt oxide positive electrode materials, ternary positive electrode materials, nickel-manganese positive electrode materials, lithium-rich positive electrode materials, etc., to play the high capacity of high-capacity positive electrode materials at high voltage in secondary batteries, and improve the energy density of secondary batteries. In addition, the electrolyte containing the polymer can also be used with high-capacity negative electrode materials to further significantly improve the energy density of secondary batteries.

[0118] The polymer of the present invention can also weaken the van der Waals attraction between polyether polymer segments by replacing halogen atoms, which can promote the mobility of the segments, thereby greatly improving the ionic conductivity of the polymer electrolyte. In addition, the present invention can form a silicon-oxygen bond or a carbon-silicon bond by introducing silicon elements into the polymer main chain. The silicon-oxygen bond or the carbon-silicon bond has good rotatability and can also greatly reduce the resistance to segment movement. When silicon-oxygen bonds and carbon-silicon bonds exist at the same time, their effects will be more significant. Therefore, the electrolyte containing the polymer of the present invention has a higher segment mobility than general polyether electrolytes, thereby significantly improving the ionic conductivity of the polymer electrolyte. At the same time, the ionic conductivity of the polymer electrolyte can be further improved by using a lithium salt that is more easily dissociated.

[0119] In addition, in the polymer of the present invention, by appropriately controlling the substitution ratio of halogen atoms in the polymer, that is, forming a comprehensive design of halogen atom content and flexible rotation bonds of the chain segment, the ability of the polymer to form a solvation structure with lithium ions can be guaranteed, that is, the solvation structure has a more negative solvation free energy, so the polymer has the advantage of good solubility for lithium salts. Further, the present invention preferably controls the substitution ratio of halogen atoms between 0.1% and 50%, which can further improve the solubility of lithium salts in polymers on the premise of improving the oxidation resistance of such polymers. This is because a large number of halogen atoms replacing hydrogen atoms on polyether segments can improve the oxidation resistance of polyether polymers, but a large number of hydrogen atoms replaced by halogens will lead to insufficient negative electronegativity of oxygen atoms on polyether segments, and the Coulomb attraction of oxygen atoms to lithium ions and / or sodium ions will be weakened, which will prevent the dissociation equilibrium of lithium salts and / or lithium salts to a certain extent. Therefore, by controlling the ratio of halogen atoms replacing hydrogen atoms, the solubility of lithium salts and / or sodium salts in polymers can be effectively improved, and more types of lithium salts and / or lithium salts can be matched. Furthermore, the present invention preferably uses a lithium salt that is more easily dissociated and the polymer of the present invention to form a polymer electrolyte, thereby greatly improving the solubility of the lithium salt and greatly improving the ionic conductivity of the electrolyte.

[0120] The composite solid electrolyte provided in the fifth aspect of the present invention has higher mechanical strength and can also effectively reduce the possibility of damage to the composite solid electrolyte and piercing of lithium dendrites. In addition, higher mechanical strength is also conducive to further processing the composite solid electrolyte into a thin film that is not easily damaged, thereby reducing the thickness of the composite solid electrolyte, thereby increasing the energy density of the battery. On the other hand, the composite solid electrolyte can regulate the uniformity of interfacial ion transport, which is conducive to improving ion migration ability and interface performance.

[0121] The sixth aspect of the present invention can further improve ion conductivity by forming a composite electrolyte, and the seventh aspect of the present invention can improve interface performance by forming a composite electrolyte.

[0122] In addition, the electrolyte of the present invention can also be mixed into the electrode plate or coated on the surface of the electrode plate, which is beneficial to improve the contact between the electrolyte and the electrode particles and reduce the interface ion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0123] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, wherein:

[0124] Figure 1 is an X-ray photoelectron spectrum of the polymer material represented by formula (3a);

[0125] Figure 2 is the infrared transmission and absorption spectrum of the polymer material represented by formula (3a);

[0126] Figure 3 is a scanning electron microscope photograph of the polymer material represented by formula (3a);

[0127] Figure 4 The figure is a comparison diagram of the linear sweep voltammetric characteristic curves of the polymers represented by formula (3a), formula (3b) and formula (3c) and polyethylene oxide. DETAILED DESCRIPTION

[0128] The present invention is further described in detail below in conjunction with specific embodiments. The given examples are only for illustrating the present invention, but not for limiting the scope of the present invention.

[0129] If no specific experimental steps or conditions are specified in the experimental examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be purchased commercially.

[0130] In the present invention, the explanations of relevant technical terms are as follows:

[0131] The "solubility" of salt in polymer refers to the situation in which the polymer and salt are dissolved in the solvent during the preparation of the polymer electrolyte membrane, and the crystallized salt is precipitated on the membrane surface after the solvent is dried or extruded and dried by spinning. When no crystallized salt is found on the surface of the polymer electrolyte membrane within the visible range of the naked eye, it means that the solubility is good; when a small amount of crystallized salt is present, it means that the solubility is average; when a large amount of crystallized salt appears, it means that the solubility is poor.

[0132] The "composite solid electrolyte" refers to a solid electrolyte that is a composite of the polymer and / or polymer electrolyte of the present invention, another inorganic solid electrolyte and / or organic solid electrolyte, and a lithium salt and / or a sodium salt.

[0133] The term "composite electrolyte" refers to an electrolyte formed by combining the polymer electrolyte of the present invention with a lithium salt or sodium salt and a plasticizer. As for the plasticizer, any substance that can be used together with the polymer electrolyte of the present invention to play a plasticizing role is within the scope of the present invention.

[0134] The "composite electrolyte" refers to an electrolyte formed by combining the polymer electrolyte of the present invention with various common electrolytes.

[0135] “Oxidation resistance” refers to resistance to chemical oxidation and resistance to electrochemical oxidation at high potential on the positive electrode side of the battery.

[0136] The polyethylene oxide and solvent used in the following comparative examples were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., and LiTFSI was purchased from Suzhou Duoduo Chemical Technology Co., Ltd.; the plasticizer and solvent used in the examples were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; LiB(CN)4 It was prepared according to the method described in J.Am.Chem.Soc.2000,122,32,7735-7741; the ultrasonic cell pulverizer model was Shinji JY92-IIN.

[0137] Example 1

[0138] This example prepares a polymer represented by formula (3a):

[0139]

[0140] The specific preparation method is as follows:

[0141] (1) mixing fluoroethylene carbonate, tetrafluoroboric acid, and fluorosilicic acid in a mass ratio of 98:1:1 in a container to form a precursor mixture;

[0142] (2) preheating the precursor mixture at 200°C for 15 minutes;

[0143] (3) heating the precursor mixture to 200° C. under vacuum conditions;

[0144] (4) After the temperature rise is complete, slowly introduce hydrogen fluoride and sulfur tetrafluoride gas and keep the temperature for 180 minutes;

[0145] (5) Cooling to room temperature and drying to obtain a polymer represented by formula (3a) on a substrate.

[0146] Example 2

[0147] This example prepares a polymer represented by formula (3b):

[0148]

[0149] The specific preparation method is as follows:

[0150] (1) mixing fluoroethylene carbonate, tetrafluoroboric acid, and fluorosilicic acid in a mass ratio of 98:1:1 in a container to form a precursor mixture;

[0151] (2) preheating the precursor mixture at 160°C for 10 minutes;

[0152] (3) heating the precursor mixture to 160° C. under vacuum conditions;

[0153] (4) After the temperature rise is complete, slowly introduce hydrogen fluoride and sulfur tetrafluoride gas and keep the temperature for 60 minutes;

[0154] (5) Cooling to room temperature and drying to obtain a polymer represented by formula (3b) on a substrate.

[0155] Example 3

[0156] This example prepares a polymer represented by formula (3c):

[0157]

[0158] The specific preparation method is as follows:

[0159] (1) 1,3-dioxolane, difluoroethylene carbonate, fluoroethylene carbonate, tetrafluoroboric acid, and fluorosilicic acid are uniformly mixed in a container in a mass ratio of 10:44:44:1:1 to prepare a precursor mixture;

[0160] (2) preheating the precursor mixture at 120°C for 15 minutes;

[0161] (3) heating the precursor mixture to 160° C. under vacuum conditions;

[0162] (4) After the temperature rise is complete, slowly introduce hydrogen fluoride, sulfur tetrafluoride, and ethylene oxide gas and keep warm for 60 minutes;

[0163] (5) Cooling to room temperature and drying to obtain a polymer represented by formula (3c) on a substrate.

[0164] Example 4

[0165] The polymer prepared in Example 1 was used to prepare a film-shaped polymer electrolyte.

[0166] (1) In an argon glove box, 0.5 g of lithium bis(trifluoromethylsulfonyl)imide LiTFSI and 2.2 g of the polymer obtained in Example 1 were dissolved in 75 ml of acetonitrile solution;

[0167] (2) Place the prepared solution in a sealed container, heat in an oil bath at 60° C. and mix and stir for 24 hours;

[0168] (3) Cool the container to room temperature, and then place the sealed container in a stirring degassing machine for degassing for 10 minutes at a speed of 1000 rpm;

[0169] (4) The above container was transferred to an argon glove box, and then the sealed container was opened and the solution was poured into a rectangular mold with an inner groove of 11 cm in length, 11 cm in width, and 2 cm in depth. The acetonitrile was allowed to evaporate naturally at room temperature and dried for 24 hours to form a film.

[0170] (5) The mold was placed in a vacuum oven at 55° C. for 24 hours to dry. After cooling, the polymer electrolyte membrane was peeled off in an argon glove box and cut into discs without visible crystalline salt.

[0171] Example 5

[0172] In the same manner as in Example 4, a film-shaped polymer electrolyte was prepared using the polymer prepared in Example 2.

[0173] Example 6

[0174] A film-like polymer electrolyte was prepared using the polymer obtained in Example 3 in a similar manner to Example 4, except that in step (1), 0.22 g of lithium tetranitrile borate LiB(CN) was used. 4 Replace 0.5g LiTFSI.

[0175] Example 7

[0176] The polymer prepared in Example 1 was used to prepare a film-like composite solid electrolyte.

[0177] (1) 1.1 g of the polymer prepared in Example 1, 0.25 g of LiTFSI and 0.2 g of Li 1.3 A1 0.3 Ti 1.7 (PO 4 ) 3 Mix with 30 ml of acetonitrile in a round-bottom flask;

[0178] (2) Add a magnet to the round-bottom flask, and place the round-bottom flask and the heated magnetic stirrer in an ultrasonic cell disruptor. Set the speed of the heated magnetic stirrer to 300 rpm, the heating temperature to 60° C., and the output power of the ultrasonic cell disruptor to 195 W for 15 minutes.

[0179] (3) After the reaction is completed, the round-bottom flask is moved to an argon glove box, and the mixed solution is poured into a rectangular mold with an inner groove of 8 cm in length, 5 cm in width, and 2 cm in depth in the argon glove box, and evaporated to dry;

[0180] (4) The mold was placed in a vacuum oven at 55°C for 24 hours to dry and cool. The polymer electrolyte membrane was then peeled off in an argon glove box and cut into discs. No crystalline salt was visible.

[0181] Example 8

[0182] This example prepares the composite electrolyte of the present invention.

[0183] A film-like polymer electrolyte was prepared in the same manner as in Example 4, except that after step (5), a dimethylformamide plasticizer was added dropwise to the surface of the film in an amount of 20% of the film's own weight.

[0184] Example 9

[0185] A solid-state battery was prepared using the polymer prepared in Example 1 and the polymer electrolyte prepared in Example 4.

[0186] (1) 80% by mass of lithium cobalt oxide, 12% by mass of the polymer of Example 1, 3% by mass of LiTFSI, 3% by mass of carbon nanotubes and 2% by mass of PVDF were dissolved in N-methylpyrrolidone, and stirred and degassed to prepare a positive electrode slurry;

[0187] (2) The positive electrode slurry was coated on the carbon-coated aluminum foil using a 100 μm scraper, dried in an oven at 55 °C for 4 hours, and then cut into discs;

[0188] (3) Assemble and package button cells in the order of lithium sheets, stacking the polymer electrolyte prepared in Example 4, stacking the positive electrode sheets, stacking the stainless steel gaskets, and stacking the stainless steel spring sheets.

[0189] Example 10

[0190] The polymer prepared in Example 1 was used to prepare a liquid battery.

[0191] (1) dissolving 90% by mass of lithium cobalt oxide, 5% by mass of carbon nanotubes and 5% by mass of PVDF in N-methylpyrrolidone, stirring and degassing to prepare a positive electrode slurry;

[0192] (2) The positive electrode slurry was coated on the carbon-coated aluminum foil using a 100 μm scraper, dried in an oven at 55°C for 4 hours, cut into discs, and then dried in a vacuum oven at 120°C for 6 hours;

[0193] (3) Take 0.02 g of the polymer prepared in Example 1 as a liquid electrolyte additive and dissolve it in 1 mol / L LiPF 6 , 5 ml EC and 5 ml DMC electrolyte;

[0194] (4) Assemble and package button cells in the following order: lithium sheet, add 100 μL of the electrolyte containing the polymer additive of step (3), stack the separator, stack the positive electrode sheet, stack the stainless steel gasket, and stack the stainless steel spring.

[0195] Embodiment 11

[0196] A liquid battery was prepared in a similar manner to Example 10, except that in step (4), the button battery was assembled and packaged in the order of lithium sheets, stacking the separator, adding 100 μl of the electrolyte containing the polymer additive, stacking the positive electrode sheets, stacking the stainless steel gaskets, and stacking the stainless steel springs.

[0197] Comparative Example 1

[0198] A polymer electrolyte was prepared in a manner similar to that of Example 4, except that 1.4 g of polyethylene oxide was added in step (1) instead of the polymer of Example 1.

[0199] Comparative Example 2

[0200] A solid-state battery was prepared in a manner similar to that of Example 9, except that, according to the same Li:O ratio, 11% by mass of polyethylene oxide and 4% by mass of LiTFSI were added in step (1) instead of 12% by mass of the polymer of Example 1 and 3% by mass of LiTFSI; and in step (5), the polymer electrolyte made of polyethylene oxide in Comparative Example 1 was stacked instead of the polymer electrolyte prepared in Example 4.

[0201] Comparative Example 3

[0202] A liquid battery was prepared in a similar manner to Example 10, except that 1 mol / L LiPF 6 , 5 ml EC and 5 ml DMC electrolyte instead of the electrolyte to which the polymer of the present invention is added.

[0203] Performance Characterization

[0204] Test Example 1

[0205] For the polymer material synthesized in the present invention, the product of Example 1, i.e., the polymer represented by Formula 3a, was taken as an example, and X-ray photoelectron spectroscopy (XPS) and infrared absorption spectrum were measured to verify the product structure. The molecular weight was roughly calculated by scanning electron microscopy (SEM).

[0206] X-ray photoelectron spectroscopy was measured by Thermo Fisher ESCALAB 250Xi, 150W Al Kα monochromatic X-ray, scanning range 0~1350eV, the results are as follows Figure 1 As shown, through the result analysis, the element composition ratio on the surface of the polymer of formula 3a synthesized according to the synthesis method of the present invention (see Table 1) conforms to the description of the corresponding polymer chemical structure.

[0207] Table 1

[0208] element O F C Si content 17.09 31.32 33.08 18.51

[0209] The infrared absorption spectrum was measured using a BRUKER VERTEX 70V Fourier transform infrared spectrometer with a measurement range of 400–4000 cm -1. The specific operation is: add 1 mg of sample to 30 mg of potassium bromide powder in a drying room and grind it, press it into a mold at 8 MPa for 2 minutes, and then measure the infrared transmission absorption spectrum. Because the infrared spectrum of organic chemistry corresponds to various vibration modes of organic functional groups, the infrared absorption spectrum calculated by density functional theory can be compared with the infrared spectrometer measurement results to verify the structure of the substance. The calculation method is as follows: First, the model in the polymer of formula (3a) with 4 sets of repeating structures is simulated annealing calculated, and the stable structure with the lowest energy is further optimized to the minimum energy at the B3LYP functional and 6-31G (d) basis set levels. Then, the vibration frequency calculation verifies that the optimized energy minimum structure is stable and has no imaginary frequency, and the peak position of the infrared absorption spectrum predicted by the calculation is drawn from the vibration frequency calculation results.

[0210] By comparing the infrared spectrometer measurement results with the theoretical calculation results (such as Figure 2 As shown), it can be seen that there are experimental test peaks corresponding to the peaks predicted by calculation, and within the inevitable error range of calculation, it can be proved that the chemical structure of the synthesized product is consistent with the polymer of the present invention.

[0211] Scanning electron microscopy was measured using a HATACHI S-4800 cold field emission scanning electron microscope. Figure 3 As shown in the SEM photos, the diameter of the spherulites of the synthesized products is mainly distributed in the range of 20 to 60 nm. The volume of a single chain segment of the polymer shown in formula (3a) is about 0.12 nm. 3 Calculation shows that the overall polymerization degree k×q of the synthesized product is mainly distributed between 35000 and 950000. Limited by the resolution limit of the scanning electron microscope, there may be structures with lower molecular weight that are difficult to be observed. According to the above measurement results, it can be seen that the polymer obtained by the synthesis method of the polymer in Example 1 has the same chemical structure as the polymer of formula (3a).

[0212] In addition, the molecular weights of the polymers shown in formulas (3b) and (3c) were roughly calculated by scanning electron microscopy (SEM), and it was found that the overall degree of polymerization (k+l)×q of the product of formula (3b) was mainly distributed between 50,000 and 1,350,000; the overall degree of polymerization (k+l+m)×q of the product of formula (3c) was mainly distributed between 30,000 and 1,300,000.

[0213] Test Example 2

[0214] The electrochemical window of the polymer material of the present invention was measured by three-electrode linear sweep voltammetry. The specific operation was as follows: using acetonitrile as the solvent of the polymer, the polymer materials represented by formula (3a) to formula (3c) and polyethylene oxide were dissolved in acetonitrile at a concentration of 2 g / l, and Ag / AgNO 3As the reference electrode, 0.1M tetrabutylammonium perchlorate as the supporting electrolyte, glassy carbon sheet as the counter electrode, and a narrow strip of double-sided thinly coated lithium cobalt oxide electrode, ternary NCM811 coated electrode, or lithium iron phosphate coated electrode as the working electrode, the stability of the polymers shown in formula (3a)-(3c) and polyethylene oxide to the high voltage positive electrode is measured; the linear sweep voltammetry measurement raises the working electrode voltage to a high potential and measures the oxidation reaction current. The reaction current density is obtained by converting the electrode area extending into the solution surface and the specific surface area of ​​the active particles of the electrode. The linear segments before and after the oxidation starting potential are extended to the intersection, and the potential at the intersection is used as the electrochemical oxidation window of the polymer material.

[0215] The active material coated on the working electrode was purchased from Rongsheng Mengguli New Energy Technology Co., Ltd. 90% of the positive electrode active material, 5% of the carbon nanotubes and 5% of the PVDF were dissolved in N-methylpyrrolidone, stirred and degassed to make a positive electrode slurry, the positive electrode slurry was applied on the carbon-coated aluminum foil using a 50-micron scraper, the positive electrode sheet was dried in a 55°C oven for 4 hours, the positive electrode slurry was applied on the back of the carbon-coated aluminum foil using a 50-micron scraper, the positive electrode sheet was dried in a 55°C oven for 4 hours, and continued to be dried in a 120°C vacuum oven for 6 hours, and the positive electrode sheet was cut into 5 mm wide strips. The counter electrode and reference electrode were purchased from Tianjin Aida Hengsheng Company, tetrabutylammonium perchlorate was purchased from Alfa Aesar (China) Chemical Co., Ltd., acetonitrile was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., and linear sweep voltammetry (linear sweep voltammetry) was measured using Shanghai Chenhua CHI604E electrochemical workstation with a scan rate of 20mV / s.

[0216] like Figure 4 As shown, the electrochemical oxidation window of the polymer represented by formula (3a) of the present invention combined with the lithium cobalt oxide positive electrode is measured to be 4.94V vs.Li + / Li. The electrochemical oxidation window of the polymer shown in formula (3b) with lithium cobalt oxide positive electrode is 4.55Vvs.Li + / Li. The electrochemical oxidation window of the polymer shown in formula (3c) combined with the ternary NCM811 electrode is 4.58V vs.Li + / Li. The electrochemical oxidation window of polyethylene oxide combined with lithium iron phosphate electrode is 3.91V vs.Li + / Li. It can be seen that the battery system composed of the polymer of the present invention can be charged to higher than 4.5V, which is significantly higher than the battery system composed of the existing polymer. Therefore, compared with the existing polymer, the polymer of the present invention has good oxidation resistance. Therefore, the electrolyte formed by the polymer can be matched with a high-voltage positive electrode to give full play to the capacity of the positive electrode material and maintain good interface stability and battery cyclability.

[0217] Test Example 3

[0218] The electrolyte membranes provided in Examples 4 to 8 and Comparative Example 1 were tested for ionic conductivity, and the test method was as follows: The electrolyte membranes provided in Examples 4 to 8 and Comparative Example 1 were respectively sandwiched between two circular stainless steel gaskets of equal area with known thickness, and then encapsulated in button batteries with springs. The samples were placed in a constant temperature oven for more than 4 hours, and then the AC impedance was measured by an external electrochemical workstation. After the measurement, the battery shell was disassembled to measure the overall thickness of the stainless steel gasket and the electrolyte membrane, which was used to convert the ionic conductivity measured by the AC impedance into ionic conductivity.

[0219] The ionic conductivity was tested by the electrochemical impedance spectroscopy (EIS) method using a Zahner IM6 electrochemical workstation in the frequency range of 0.1 Hz to 1 MHz with an amplitude of 10 mV. The results are shown in Table 2.

[0220] Table 2

[0221] Temperature(℃) Ionic conductivity (S / cm) Example 4 60 <![CDATA[7.7x10 -4 ]]> Example 5 60 <![CDATA[1.2x10 -3 ]]> Example 6 60 <![CDATA[1.8x10 -3 ]]> Example 6 30 <![CDATA[5.8x10 -4 ]]> Example 7 60 <![CDATA[9.3x10 -4 ]]> Example 8 30 <![CDATA[6.1x10 -4 ]]> Comparative Example 1 60 <![CDATA[2.3x10 -4 ]]> Comparative Example 1 30 <![CDATA[6.6x10 -6 ]]>

[0222] It can be seen from the data in Table 2 that the ionic conductivity of the electrolyte membrane provided by Examples 4 to 8 of the present invention is not less than 7×10 -4 S / cm, and can reach up to 1.8x10 -3 S / cm, not less than 5x10 at 30℃ -4 S / cm, while the ionic conductivity of the electrolyte membrane of Comparative Example 1 is only 2.3x10 -4 S / cm, 30℃ is only 6.6x10 -6 S / cm, indicating that the ionic conductivity of the polymer electrolyte of the present invention is greatly improved compared with the prior art both at low temperature and high temperature.

[0223] Test Example 4

[0224] The button cells provided in Examples 9-11 and Comparative Examples 2-3 were subjected to a battery cycle capacity life test, and a charge and discharge cycle performance test was performed at a rate of 0.2C. The discharge capacity after 50 cycles was measured to calculate the capacity retention rate. The results are shown in Table 3.

[0225] Table 3

[0226] Temperature(℃) Capacity retention after 50 cycles (%) Example 9 60 92 Example 10 30 75 Embodiment 11 30 87 Comparative Example 2 60 0 Comparative Example 3 30 52

[0227] Among them, "0" means that the battery can no longer work normally at 50 weeks.

[0228] It should be noted that the present invention illustrates the process method of the present invention through the above experimental examples, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to experiment. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A polymer for an electrolyte, which is a homopolymer and / or an alternating polymer and / or a block polymer and / or a graft polymer and / or a random polymer consisting of repeating units represented by formula (1): in: R1, R2, R3, R4, R5 and R6 are each independently selected from C1-C20 alkylene, C1-C20 alkylene fully or partially substituted by halogen, C1-C20 alkylene in which all or part of the carbon atoms are substituted by silicon atoms, and at least one of R1, R2, R3, R4, R5 and R6 contains a halogen atom; k, l, m, n, o and p are each independently an integer from 0 to 100, q is an integer from 1 to 300000, and (k+l+m+n+o+p)×q>3; The polymer main chain contains silicon-oxygen bonds or carbon-silicon bonds.

2. The polymer according to claim 1, wherein The terminal groups of the polymer are one or more groups selected from ether, alcohol, ester, carbonate, carboxylic acid, aldehyde, ketone, C1-C20 alkyl, C1-C20 alkenyl, and C1-C20 halogenated hydrocarbon.

3. The polymer according to claim 1, wherein q is an integer from 3,000 to 300,000.

4. The polymer according to claim 1, wherein R1, R2, R3, R4, R5 and R6 are each independently selected from the structures of formula (1a) to formula (1j): Among them, each R x Each is independently silicon or carbon, and each X is independently hydrogen, a halogen or a repeating unit represented by formula (1).

5. The polymer according to claim 4, wherein The total molar percentage of X being halogen in R1, R2, R3, R4, R5 and R6 is between 1% and 50%.

6. The polymer according to any one of claims 1 to 5, wherein The polymer has one of the structures shown in formula (2a) to formula (2h): wherein X is selected from hydrogen or halogen, and In formula (2a), k×q is greater than 3; in formula (2b) and formula (2d) to formula (2h), (k+l)×q is greater than 3; in formula (2c), (k+l+m)×q is greater than 3.

7. The polymer according to claim 6, wherein In formula (2a), k×q is between 3000 and 3000000; in formula (2b) and formula (2d) to formula (2h), (k+l)×q is between 3000 and 3000000; in formula (2c), (k+l+m)×q is between 3000 and 3000000.

8. The polymer according to any one of claims 1 to 5, wherein The polymer has one of the structures shown in formula (3a) to formula (3h): Among them, k, l, and m are not 0 at the same time, and In formula (3a), k×q is greater than 3; in formula (3b) and formula (3d) to formula (3h), (k+l)×q is greater than 3; in formula (3c), (k+l+m)×q is greater than 3.

9. The polymer according to claim 8, wherein In formula (3a), k×q is between 3000 and 3000000; in formula (3b) and formula (3d) to formula (3h), (k+l)×q is between 3000 and 3000000; in formula (3c), (k+l+m)×q is between 3000 and 3000000.

10. A method for preparing a polymer for electrolyte according to any one of claims 1 to 9, comprising preparing or preparing a precursor, and obtaining the polymer by a gas phase synthesis method.

11. The preparation method according to claim 10, comprising the following steps: (1) mixing the precursors and optionally activating them by preheating; (2) The precursor obtained in step (1) is heated to perform gas phase synthesis, and the polymer for electrolyte is obtained after drying.

12. The preparation method according to claim 11, wherein The preheating temperature in step (1) is 40 to 400° C.; the preheating time is 1 to 30 minutes.

13. The preparation method according to claim 10, wherein: The precursor is 1,3-dioxolane, 1,3-cyclopentanedione, 1,4-dioxane, 1,4-dioxane-2,5-hexanedione, 1,4-cyclohexanedione, 2-fluoroethylene oxide, 2,2-difluoroethylene oxide, 2,3-difluoroethylene oxide, epoxyfluoropropane, diethylamino sulfur trifluoride, trifluoropropyl trichlorosilane, tetrafluoroboric acid, hexafluorophosphoric acid, hexafluorotitanic acid, fluoroethylene carbonate A combination of two or more of olefin ester, ethylene oxide, thionyl chloride, phosphoric acid, sulfuric acid, boric acid, polytetrafluoroethylene powder, fluorosilicic acid, hydrofluoric acid, trifluoromethyl carbonate, stannous octoate, ethylene glycol dimethyl ether, glycolaldehyde dimer, glycolide, N-fluorobisbenzenesulfonamide, 1-chloromethyl-4-fluoro-1,4-diazotized bicyclo 2.2.2 octane bis(tetrafluoroborate), silicon dioxide, and sulfur tetrafluoride. The preparation method according to claim 13 , wherein the precursor comprises ethylene difluorocarbonate.

15. The preparation method according to claim 11, wherein The heating temperature in step (2) is 40-400°C.

16. The preparation method according to claim 11, wherein The gas phase synthesis in step (2) includes vacuum evaporation or vapor deposition, and optionally a gas is introduced during the vacuum evaporation or vapor deposition process; wherein the gas is selected from ethylene oxide-containing gas, halogen-containing gas or ozone.

17. The preparation method according to claim 16, wherein: The halogen-containing gas is a combination of one or more of 1,1-dichloro-2,2-difluoroethylene, 2-chloro-1,2-dibromo-1,1,2-trifluoroethane, chlorotrifluoroethylene, nitrogen trifluoride, trifluoromethyl trifluorovinyl ether, carbon tetrafluoride, sulfur hexafluoride, hexafluoropropylene oxide, octafluorocyclobutane, trans-1,1,1,3-tetrafluoropropylene, fluorine gas, sulfuryl fluoride, hydrogen chloride gas, chlorine gas, hydrofluoric acid gas, and isoflurane.

18. The preparation method according to claim 16, wherein: A solid catalyst is used in the process of vacuum evaporation or vapor deposition; the solid catalyst is selected from one or more of oxides, silicic acid compounds, boric acid compounds, and metal catalysts.

19. The preparation method according to claim 18, wherein: The solid catalyst is a combination of one or more of silicon dioxide, manganese dioxide, aluminum oxide, boron oxide, silicic acid, silicate, boric acid, borate, cobalt oxide, copper oxide, zinc oxide, iron oxide, nickel oxide, manganese oxide, calcium oxide, silver, platinum, gold, iron, cobalt, nickel, molybdenum, niobium, magnesium, aluminum, titanium, zinc, and calcium.

20. The preparation method according to claim 19, wherein: The borates include lithium tetraborate and sodium tetraborate.

21. A polymer electrolyte comprising a polymer according to any one of claims 1 to 9 or a polymer prepared according to any one of claims 10 to 20, and a lithium salt and / or a sodium salt, wherein: The mass percentage of the polymer in the polymer electrolyte is 5% to 99%, and the mass percentage of the lithium salt and / or sodium salt in the polymer electrolyte is 1% to 95%.

22. A method for preparing a polymer electrolyte, comprising: The polymer is mixed with lithium salt and / or sodium salt, dissolved in a solvent to obtain a solid electrolyte slurry, and dried to obtain the polymer electrolyte; or The polymer electrolyte is prepared by electrospinning the polymer and lithium salt and / or sodium salt. Wherein, the polymer is the polymer according to any one of claims 1 to 9 or a polymer prepared according to the preparation method according to any one of claims 10 to 20.

23. A composite solid electrolyte comprising a polymer as described in any one of claims 1 to 9; or a polymer prepared by the preparation method as described in any one of claims 10 to 20; or a polymer electrolyte as described in claim 21; or a polymer electrolyte prepared by the preparation method as described in claim 22, and at least one additional inorganic solid electrolyte and / or organic solid electrolyte.

24. A composite electrolyte comprising the polymer electrolyte according to claim 21 or the polymer electrolyte prepared according to the preparation method according to claim 22, and a plasticizer.

25. The composite electrolyte according to claim 24, wherein The mass percentage of the plasticizer in the composite electrolyte is 0.1% to 50%.

26. The composite electrolyte according to claim 24, wherein The plasticizer includes one or more of an amide-based compound, an ether-based compound, an ester-based compound, a nitrile-based compound, and a cycloalkane-based compound.

27. The composite electrolyte according to claim 26, wherein The ester-based compound includes a cyclic ester-based compound.

28. The composite electrolyte according to claim 26, wherein The ester-based compound includes a carbonate-based compound.

29. A composite electrolyte comprising the polymer electrolyte according to claim 21 or the polymer electrolyte prepared according to the preparation method according to claim 22 as an additive, and a main component of the electrolyte.

30. A secondary battery comprising a positive electrode, a negative electrode and an electrolyte, wherein: The electrolyte is at least one of the polymer electrolyte according to claim 21, the polymer electrolyte prepared according to the preparation method according to claim 22, the composite solid electrolyte according to claim 23, the composite electrolyte according to claim 24, and the composite electrolyte according to claim 29.

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