A polymer electrolyte, a preparation method thereof and an application thereof

Abstract

The present invention provides a polymer electrolyte, a preparation method thereof and an application thereof. The polymer electrolyte is formed by in-situ polymerization of a precursor solution containing a polymerizable monomer, a lithium salt, an organic solvent and an initiator, wherein the polymerizable monomer includes a polymerizable monomer A represented by formula (I). In the present invention, the phosphorus-based highly safe polymerizable monomer A is applied to a lithium battery. Through in-situ polymerization, a highly safe lithium battery prepared by in-situ curing is obtained, effectively improving the battery safety. The electrolyte prepared by the method of in-situ curing greatly improves the interfacial contact between the electrolyte and the electrode sheet, reduces polarization and interfacial impedance. The preparation process is simple, safe, environmentally friendly, reduces the use and emission of organic solvents, and is compatible with the existing liquid battery process.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a highly safe polymer electrolyte prepared by in-situ curing, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium-ion batteries (LIBs) have been widely used in various fields such as portable devices, electric vehicles, and power grids. For each application field of the battery, the electrochemical performance, safety, and cost of the battery need to be considered. In any case, it is imperative to use batteries with higher energy density and longer lifespan to meet the growing energy demand.

[0003] On the one hand, with the increasing requirements for battery safety, traditional LIBs, due to the use of liquid electrolytes and containing a large amount of flammable organic carbonate solvents, are prone to a series of safety problems such as electrolyte leakage, thermal runaway, or explosion. Given the disadvantages of traditional LIBs, solid-state batteries composed of polymer solid electrolytes or inorganic solid electrolytes can greatly improve the safety performance of LIBs because they do not have liquid electrolytes.

[0004] Currently, all-solid-state electrolytes generally include inorganic solid electrolytes and polymer solid electrolytes. Among them, polymer solid electrolytes have a series of problems such as low ionic conductivity and increased interfacial impedance. Therefore, gel polymer electrolytes (GPEs) that can balance interfacial contact and ionic conductivity have attracted more and more attention. Generally, the preparation methods of GPEs mainly include the following several: solution casting method, ultraviolet curing method, in-situ polymerization method, etc. Among them, the in-situ polymerization method can significantly reduce the interfacial resistance, and the preparation process is simple and environmentally friendly.

[0005] On the other hand, with the improvement of the high energy density of the battery, the accompanying problem is battery safety. For the electrolyte, the common solution is to add a cathode additive that can form a CEI on the surface of the cathode particles or an anode additive that can form an SEI on the surface of the anode. However, the currently used additives have single performance and need to be used in combination with multiple additives; in addition, in order not to affect the electrical performance, the amount of additives used is small, and the role played is limited, so it is difficult to completely solve the safety problem of high energy density batteries. Summary of the Invention

[0006] Therefore, the purpose of the present invention is to provide a new polymer electrolyte, a preparation method thereof, and an application thereof, which can improve the electrochemical performance of the battery while improving the battery safety.

[0007] For the convenience of description, some names or terms in this article are defined and explained as follows.

[0008] The term "optional" or "optionally" means that the subsequently described substance, step or situation may or may not exist or occur.

[0009] The term "heteroatom-containing" means that one or more carbon atoms in a carbon chain or carbon ring are replaced by heteroatoms, and the heteroatoms can be P, S, Si, N or O. For example, "heteroatom-containing C 1-18 hydrocarbyl" means a group in which one or more carbon atoms in the C 1-18 hydrocarbyl are replaced by heteroatoms.

[0010] As used herein, "halogen" means fluorine, chlorine, bromine or iodine, preferably fluorine or chlorine, more preferably fluorine.

[0011] The term "hydrocarbyl" means a monovalent group derived by removing a hydrogen atom from a hydrocarbon. The term "hydrocarbylene" means a divalent group derived by removing two hydrogen atoms from a hydrocarbon. In the present invention, the (hydrocarbyl) group can be linear (straight-chain or branched-chain) or cyclic (monocyclic or polycyclic), and can include (hydrocarbyl)alkyl, (hydrocarbyl)alkenyl and (hydrocarbyl)alkynyl. The (hydrocarbyl) group described in the present invention usually has 1 to 18 carbon atoms. Preferably, the (hydrocarbyl) group can be a C 1-15 chain (hydrocarbyl) or a C 3-18 cyclic (hydrocarbyl), more preferably a C 1-10 chain (hydrocarbyl) or a C 3-10 cyclic (hydrocarbyl), most preferably a C 1-6 chain (hydrocarbyl) or a C 3-8 cyclic (hydrocarbyl).

[0012] The term "alkyl" means a monovalent group derived from an alkane by removing a hydrogen atom from any carbon atom. The alkyl can be straight-chain, branched-chain or cyclic. In the present invention, the alkyl has 1 to 15 carbon atoms (C 1-15 alkyl), preferably 1 to 10 carbon atoms (C 1-10 alkyl), more preferably 1 to 6 carbon atoms (C 1-6 alkyl).

[0013] In the present invention, the ring can include a monocyclic ring, a fused ring, a spiro ring, a bridged ring or a spiro ring. In addition, the ring can include a saturated carbon ring, an unsaturated carbon ring, a saturated heterocyclic ring, an unsaturated heterocyclic ring, an aromatic ring, an aromatic heterocyclic ring, etc.

[0014] It should be noted that any type of numerical range disclosed in the present application is intended to separately disclose each possible number that can be reasonably covered within the range, as well as any sub-range and combination of sub-ranges covered therein. In particular, the carbon number ranges herein are equivalent to separately disclosing each possible carbon value and / or sub-range covered therein. For example, C 1-10The carbon number range is equivalent to disclosing C1, C2, C3, C4, C5, C6, C7, C8, C9, and C 10 , and the sub-ranges covered therein, such as C 2-9 , C 3-8 , C 1-6 , C 1-4 and so on.

[0015] On the one hand, the present invention provides a polymer electrolyte, wherein the polymer electrolyte is in-situ polymerized from a precursor solution containing a polymerizable monomer, a lithium salt, an organic solvent, and an initiator, and the polymerizable monomer includes a polymerizable monomer A represented by formula (I):

[0016]

[0017] Wherein, L 1 and L 2 are independently selected from none (i.e., a single bond), C 1-18 alkylene or heteroatom-containing C 1-18 alkylene, wherein the C 1-18 alkylene is optionally substituted by one or more R a ;

[0018] R 1 is selected from H, C 1-18 hydrocarbyl or heteroatom-containing C 1-18 hydrocarbyl, wherein the C 1-18 hydrocarbyl is optionally substituted by one or more R a ;

[0019] R 2 and R 3 are independently selected from C 1-15 alkyl, and the C 1-15 alkyl is optionally substituted by one or more R a ;

[0020] R a is selected from halogen, C 1-10 hydrocarbyl or heteroatom-containing C 1-10 hydrocarbyl, hydroxyl, =O, =S, aldehyde group, carbonate group, formyl group, carboxyl group, ester group, peroxy group, amine group (primary amine, secondary amine, tertiary amine, quaternary ammonium salt), imino group (C=N), imide group (C(=O)NC(=O)), azo group, nitrate group (RONO2), phosphate group, thioether group, disulfide group, cyano group, sulfonic acid group, sulfonyl group, amide group, nitro group, pyridyl group, acyloxy group, phenyl group, phenoxy group, benzyl group, benzyloxy group, acetyl group, benzoyl group, benzyloxycarbonyl group, and groups in which one or more H thereof are substituted by halogen.

[0021] According to the polymer electrolyte provided by the present invention, preferably, in the polymerizable monomer A represented by formula (I), L 1 and L 2 are independently selected from none, C 1-10 chain alkylene, heteroatom-containing C 1-10 chain alkylene, C 3-10 cycloalkylene or heteroatom-containing C 3-10 cycloalkylene, and these groups are optionally substituted by one or more R a ; more preferably, L 1 and L 2 are independently selected from none, C 1-6 chain alkylene, heteroatom-containing C 1-6 chain alkylene, C 3-8 cycloalkylene or heteroatom-containing C 3-8 cycloalkylene, and these groups are optionally substituted by one or more R a .

[0022] According to the polymer electrolyte provided by the present invention, preferably, in the polymerizable monomer A represented by formula (I), R 1 is selected from H, C 1-10 chain hydrocarbon group, heteroatom-containing C 1-10 chain hydrocarbon group, C 3-10 cyclic hydrocarbon group or heteroatom-containing C 3-10 cyclic hydrocarbon group, and these groups are optionally substituted by one or more R a ; more preferably, R 1 is selected from H, C 1-6 chain hydrocarbon group, heteroatom-containing C 1-6 chain hydrocarbon group, C 3-8 cyclic hydrocarbon group or heteroatom-containing C 3-8 cyclic hydrocarbon group, and these groups are optionally substituted by one or more R a .

[0023] According to the polymer electrolyte provided by the present invention, preferably, in the polymerizable monomer A represented by formula (I), R 2 and R 3 are independently selected from C 1-10 alkyl, and the C 1-10 alkyl is optionally substituted by one or more R a ; more preferably, R 2 and R 3 are independently selected from C 1-6 alkyl.

[0024] According to the polymer electrolyte provided by the present invention, in the precursor solution, the mass fraction of the polymerizable monomer can be 0.5% to 50%, preferably 1% to 20%; the mass fraction of the lithium salt can be 5% to 30%, preferably 8% to 20%; the mass fraction of the organic solvent can be 1% to 92%, preferably 50% to 90%; the mass fraction of the initiator can be 0.001% to 0.5%, preferably 0.005% to 0.3%; preferably, the mass fraction of the polymerizable monomer A in the polymerizable monomer can be 5% to 100%, preferably 50% to 100%.

[0025] According to the polymer electrolyte provided by the present invention, wherein the lithium salt can be selected from one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalate borate, lithium bis(oxalate) borate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium trifluoromethylbenzenesulfonate, lithium difluorophosphate, lithium difluorobis(oxalate) phosphate, and lithium tetrafluorooxalate phosphate.

[0026] The organic solvent can be selected from one or more of ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, ethylene glycol vinyl ether carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl formate, ethyl formate, propyl formate, butyl formate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, δ-valerolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 2-methyl-1,3-dioxolane, ethylene glycol dimethyl ether, polyethylene glycol, sulfolane, triethylene glycol dimethyl ether, fluorinated 1,4-dimethoxybutane, bis(2,2,2-trifluoroethyl) ether, tetramethylsilane, and tetraethylene glycol dimethyl ether.

[0027] The initiator can be selected from one or more of azobisisobutyronitrile (AIBN), azobisisoheptonitrile (ABVN), dimethyl azobisisobutyrate (AIBME), benzoyl peroxide (BPO), tert-butyl perbenzoate (BPB), and methyl ethyl ketone peroxide. In some embodiments of the present invention, a composite initiator system can be used, such as AIBN-ABVN or BPO-BPB, etc.

[0028] According to the polymer electrolyte provided by the present invention, wherein the polymerizable monomer may further include a polymerizable monomer B represented by formula (II):

[0029]

[0030] Wherein, R 6 is selected from

[0031] R 4 and R7 to R 10 are independently selected from H, C 1-18 hydrocarbyl or heteroatom-containing C 1-18 hydrocarbyl, wherein said C 1-18 hydrocarbyl is optionally substituted by one or more R a substituents.

[0032] R 5 is selected from none, C 1-18 alkylene or heteroatom-containing C 1-18 alkylene, wherein said C 1-18 alkylene is optionally substituted by one or more R a substituents.

[0033] wherein said R a is as defined above.

[0034] Preferably, in the polymerizable monomer B represented by formula (II):

[0035] R 4 and R7 to R 10 are independently selected from H, C 1-10 alkyl, heteroatom-containing C 1-10 alkyl, C 3-10 cycloalkyl or heteroatom-containing C 3-10 cycloalkyl, and these groups are optionally substituted by one or more R a substituents; preferably, R 4 and R7 to R 10 are independently selected from H, C 1-6 alkyl, heteroatom-containing C 1-6 alkyl, C 3-8 cycloalkyl or heteroatom-containing C 3-8 cycloalkyl, and these groups are optionally substituted by one or more R a substituents;

[0036] R 5 is selected from none, C 1-10 alkylene, heteroatom-containing C 1-10 alkylene, C 3-10 cycloalkylene or heteroatom-containing C 3-10 cycloalkylene, and these groups are optionally substituted by one or more R a substituents; preferably, R 5 is selected from none, C 1-6 alkylene, heteroatom-containing C 1-6 alkylene, C 3-8 cycloalkylene or heteroatom-containing C 3-8A cycloalkylene group, and these groups are optionally substituted by one or more R a substituents.

[0037] When the polymerizable monomer B is included, the mass ratio of the polymerizable monomer B to the polymerizable monomer A can be greater than 0 to 20, preferably greater than 0 to 1.

[0038] In the polymer electrolyte of the present invention, the polymerizable monomer includes: polymerizable monomer A, or a mixture of polymerizable monomer A and polymerizable monomer B.

[0039] The polymerizable monomer A and polymerizable monomer B used in the present invention can be commercially available or synthesized. Those skilled in the art can determine their preparation methods according to the chemical structure of the polymerizable monomer to be synthesized and in accordance with the basic concepts and experimental methods of organic synthesis.

[0040] According to the polymer electrolyte provided by the present invention, preferably, the polymer electrolyte may further include an electrolyte additive. The electrolyte additive can be a commercial additive, for example, it can be selected from one or more of fluoroethylene carbonate, vinylene carbonate, trimethyl phosphate, triethyl phosphate, succinic anhydride, 18-crown-6, triphenyl phosphite, ethylene ethylene carbonate, trimethyl borate, lithium difluorobis(oxalato)phosphate, lithium tetrafluoroborate, tributyl phosphate, biphenyl, ethylene sulfite, difluorodiphenylsilane, lithium bis(fluorosulfonyl)imide, tributyl borate, ethoxypentafluorocyclotriphosphazene, ethylene sulfate, lithium nitrate, 1,3-propane sultone, lithium difluorophosphate, diethyl sulfite, and succinonitrile.

[0041] On the other hand, the present invention also provides a preparation method of the above polymer electrolyte, and the preparation method includes:

[0042] (1) Under a humidity with a dew point lower than -45°C, mixing the polymerizable monomer, lithium salt, organic solvent, initiator, and optionally the electrolyte additive to obtain a precursor solution; or mixing the polymerizable monomer and initiator with a lithium secondary battery electrolyte to obtain a precursor solution;

[0043] (2) Subjecting the precursor solution obtained in step (1) to in-situ polymerization at 45 to 85°C to form the polymer electrolyte.

[0044] According to the preparation method provided by the present invention, wherein the time of the in-situ polymerization can be 2 to 24 h.

[0045] According to the preparation method provided by the present invention, wherein the polymerizable monomer, lithium salt, organic solvent, initiator, and electrolyte additive are as defined above. The lithium secondary battery electrolyte refers to a commercially available electrolyte currently used in lithium secondary batteries, and the present invention has no particular limitation on its composition and ratio.

[0046] On the other hand, the present invention also provides a lithium secondary battery, which includes an electrode assembly, an electrolyte, and a packaging case. Among them, the electrolyte is the polymer electrolyte provided by the present invention or the polymer electrolyte prepared according to the method of the present invention.

[0047] Among them, the electrode assembly includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode.

[0048] According to the lithium secondary battery provided by the present invention, among them, the positive electrode active material used in the positive electrode may include one or more of lithium iron phosphate, lithium iron manganese phosphate, lithium cobaltate, lithium manganate, lithium nickel manganate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, and lithium-rich manganese; the negative electrode may be one or more of graphite, silicon, soft carbon, hard carbon, silicon-carbon composite material, silicon-oxygen-carbon, lithium titanate, mesophase carbon microspheres, molybdenum disulfide, silicon monoxide, silicon, metallic lithium, or metallic lithium alloy; the separator may be one of a polyolefin separator, a cellulose separator, a polyimide separator, a polyamide separator, an aramid separator, a PET non-woven fabric separator, a ceramic-coated separator, a solid electrolyte-coated separator, and a PVDF-coated separator; the packaging case may be one of a soft-pack aluminum-plastic film, a steel case, an aluminum case, and a cylinder.

[0049] On another hand, the present invention also provides a preparation method of a lithium secondary battery, and the preparation method includes:

[0050] Manufacturing an electrode assembly by laminating or winding a positive electrode sheet, a negative electrode sheet, and a separator, and placing the electrode assembly in a packaging case;

[0051] Injecting the precursor solution of the present invention into the packaging case, and after fully infiltrating the electrode assembly, in-situ polymerizing at 45-85 °C to form the polymer electrolyte, thus obtaining the lithium secondary battery.

[0052] The highly safe polymer electrolyte obtained by in-situ polymerization provided by the present invention can be used to replace part of the traditional electrolyte solution, effectively improving the battery safety. The highly safe polymer electrolyte obtained by in-situ polymerization of the present invention can be used in small amounts or in increased amounts, and can be applied to gel batteries and quasi-solid-state batteries. The highly safe polymer electrolyte obtained by in-situ polymerization of the present invention can be applied to both high-energy density battery (≥280 Wh / kg) systems and low-energy density battery (<280 Wh / kg) systems, improving the gas generation problem of the battery and enhancing safety problems such as thermal box, extrusion, overcharge, and pinprick. The polymer electrolyte, its preparation method, and application provided by the present invention mainly have the following beneficial effects:

[0053] 1. The present invention applies a phosphorus-based high-safety polymerizable monomer (polymerizable monomer A) to a lithium battery. After being injected into the battery cell, it is polymerized in situ to obtain a high-safety electrolyte prepared by in-situ curing, and then a high-safety lithium battery prepared by in-situ curing is obtained, which effectively improves the safety of the battery.

[0054] 2. In a preferred embodiment of the present invention, a highly safe polymerizable monomer A and a polymerizable monomer B containing a film-forming functional group are simultaneously introduced into a lithium battery to improve the safety of the battery while improving the electrochemical performance of the battery.

[0055] 3. Compared with the traditional polymer battery preparation technology, the electrolyte prepared by the in-situ solidification method of the present invention greatly improves the interface contact between the electrolyte and the electrode, reduces the polarization and interface impedance, and thus the electrical performance (such as energy density and cycle times) is comparable to that of conventional liquid batteries.

[0056] 4. The present invention adopts in-situ curing technology, the preparation process is simple, safe and environmentally friendly, greatly reduces the use and emission of organic solvents, and is compatible with existing liquid battery processes, making it easy to quickly promote industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, wherein:

[0058] Figures 1 to 5 The NMR proton spectra of polymerizable monomers A3, B3, A4, B4 and A8 are shown in order;

[0059] Figure 6 The figure is a comparison of the puncture results of battery 2 (left) and battery 2a (right). DETAILED DESCRIPTION

[0060] 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.

[0061] The materials and performance tests used in the examples are described as follows:

[0062] 1. English abbreviations and corresponding substance descriptions: Ethyl methyl carbonate (EMC), Dimethyl carbonate (DMC), Diethyl carbonate (DEC), Ethylene carbonate (EC); Lithium nitrate (LiNO3), Fluoroethylene carbonate (FEC), Divinyl sulfite (DTD), Lithium bis(oxalato)phosphate tetrafluoride (LiPC2O2F4), 1,4-Dimethoxybutane difluoride (FDMB), 1,3-Propane sultone (1,3-PS), Lithium difluorophosphate (LiPO2F2), Vinylene carbonate (VC), 1,3,6-Hexanetricarbonitrile (HTCN); Lithium difluoro(oxalato)borate (LiODFB), Lithium tetrafluoroborate (LiBF4), Lithium bis(oxalato)borate (LiBOB), Lithium hexafluorophosphate (LiPF6), Lithium bis(fluoromethylsulfonyl)imide (LiFSI); 2,2'-Azobis(2-methylpropionitrile) (AIBN), Benzoyl peroxide (BPO).

[0063] 2. The polymerizable monomers A1 - A8 and polymerizable monomers B1 - B8 used in the examples are prepared by synthesis. Among them, the polymerizable monomer A is obtained by reacting X-NCO containing -NCO group and Y-OH containing -OH group to obtain X-NH-(C=O)O-Y-. Exemplarily, Figures 1 to 5 1H NMR spectra of polymerizable monomers A3, B3, A4, B4 and A8 are given in sequence.

[0064] 3. 0.5C / 1C means charging at a rate of 0.5C and discharging at a rate of 1C; 0.3C / 0.3C means charging at a rate of 0.3C and discharging at a rate of 0.3C.

[0065] Example 1

[0066] 0.012 mol of diethyl hydroxymethylphosphonate, 0.012 mol of vinyl isocyanate and 25 ml of toluene were mixed and added to a 50 ml three-necked flask, stirred for 2 hours, and a toluene solution containing 0.014 g of stannous octoate was added dropwise through a constant pressure funnel, controlling the temperature at 0 - 5 °C, reacting for 6 hours, and then the solvent was removed by vacuum distillation at 60 °C to obtain the polymerizable monomer A1.

[0067] (Polymerizable monomer A1)

[0068] (1) Preparation of the positive electrode sheet

[0069] The positive electrode active material lithium cobaltate, the electronic conductive additive (carbon nanotubes and Super P), and PVDF were added to N-methylpyrrolidone in a mass ratio of 95:3:2, and the solvent accounted for 65% of the total slurry mass. After mixing and stirring evenly, a positive electrode slurry with certain fluidity was obtained. The positive electrode slurry was coated on aluminum foil, dried, compacted and cut to obtain a usable lithium cobaltate positive electrode sheet.

[0070] (2) Preparation of the negative electrode sheet

[0071] The negative active material silicon oxycarbide 450 (SiOC, specific capacity 450 mAh / g), electronic conductive additives (carbon nanotubes and Super P), and binders (carboxymethyl cellulose and styrene-butadiene rubber) were added to deionized water as a solvent in a mass ratio of 95:2.5:2.5. The solvent accounted for 42% of the total slurry. After mixing and stirring evenly, a negative electrode slurry with certain fluidity was obtained. The negative electrode slurry was coated on copper foil, dried, compacted, and cut to obtain a usable silicon oxycarbide negative electrode sheet.

[0072] (3) Preparation of the battery cell

[0073] The positive electrode sheet prepared in step (1), the negative electrode sheet prepared in step (2), and a PE / Al2O3 (12μm + 2μm) separator were assembled into an 8 Ah soft-pack battery cell, which was stacked, encapsulated, and baked for standby.

[0074] (4) In-situ polymerization to form a polymer electrolyte

[0075] In an environment with a dew point lower than -45°C, 0.5 g of polymerizable monomer A1, 0.162 g of additives (0.032 g of FEC, 0.048 g of VC, 0.032 g of LiPC2O2F4, 0.05 g of HTCN), 0.01 g of AIBN initiator, 2.92 g of lithium salt LiPF6, 6.26 g of EC, and 8.82 g of EMC were mixed evenly to obtain a precursor solution. The precursor solution was injected into the battery cell prepared in step (3) and allowed to stand for 8 hours, and then cured at 60°C for 8 hours to form an in-situ polymerized electrolyte.

[0076] Then, through processes such as formation, secondary sealing, and grading, an in-situ solidified battery was obtained, denoted as: Battery 1a, with an energy density of 288 Wh / kg.

[0077] Example 2

[0078] 0.010 mol of 5-fluoro-4-hydroxymethyl-1,3-dioxolane-2-one, 0.011 mol of methacrylic acid, and 25 ml of xylene were mixed and added to a three-necked flask. After stirring for 3 hours, the temperature was then raised to 110°C, and then 0.148 g of concentrated sulfuric acid was added dropwise through a constant pressure funnel. The reaction was carried out at 110°C for 6 hours, and then the solvent was removed by vacuum distillation to obtain polymerizable monomer B1.

[0079] (Polymerizable monomer B1)

[0080] The battery 1b was prepared in a manner parallel to Example 1, except that: in step (4), "0.5 g of polymerizable monomer A1" was changed to "0.35 g of polymerizable monomer A1 and 0.15 g of polymerizable monomer B1". The prepared battery was denoted as: battery 1b, and its energy density was 290 Wh / kg.

[0081] Comparative Example 1

[0082] The comparative battery 1 was prepared in a manner parallel to Example 1, except that: in step (4), the polymerizable monomer A1 and the AIBN initiator were not added. The prepared battery was denoted as: comparative battery 1, and its energy density was 291 Wh / kg.

[0083] Electrical Property Test 1

[0084] The cycling voltage range was 2.75 - 4.45 V, and the cycling mode was 0.5C / 1C.

[0085] The number of cycles when the capacity of battery 1a decayed to 80% of the initial capacity was 351 cycles.

[0086] The number of cycles when the capacity of battery 1b decayed to 80% of the initial capacity was 392 cycles.

[0087] The number of cycles when the capacity of comparative battery 1 decayed to 80% of the initial capacity was 153 cycles.

[0088] Example 3

[0089] 0.014 mol of dimethyl hydroxymethylphosphonate, 0.017 mol of vinyl isocyanate, and 25 ml of dichloromethane were added to a 50 - ml three - necked flask, stirred for 2 hours, and a dichloromethane solution containing 0.0318 g of triethylamine was added dropwise through a constant - pressure funnel. The reaction was carried out at room temperature for 6 hours, and then the solvent was removed by distillation under reduced pressure at 25°C to obtain the polymerizable monomer A2.

[0090] (Polymerizable monomer A2)

[0091] (1) Preparation of the positive electrode plate

[0092] The positive electrode active material ternary NCM811 (commercialized layered lithium nickel cobalt manganate), the electronic conductive additive (carbon nanotubes and Super P), and PVDF were added to N - methylpyrrolidone in a mass ratio of 95:3:2. The solvent accounted for 65% of the total slurry mass. After mixing and stirring evenly, a positive electrode slurry with certain fluidity was obtained. The positive electrode slurry was coated on aluminum foil, dried, compacted, and cut to obtain a usable NCM811 positive electrode plate.

[0093] (2) Preparation of the negative electrode sheet

[0094] The negative active material silicon oxycarbide 600 (SiOC, specific capacity 600 mAh / g), electronic conductive additives (carbon nanotubes and Super P), and binders (carboxymethyl cellulose and styrene-butadiene rubber) are added to deionized water as a solvent in a ratio of 95:2.5:2.5. The solvent accounts for 42% of the total slurry. After mixing and stirring evenly, a negative electrode slurry with certain fluidity is obtained. The negative electrode slurry is coated on a copper foil, dried, compacted, and cut to obtain a usable silicon oxycarbide negative electrode sheet.

[0095] (3) Preparation of the battery cell

[0096] The positive electrode sheet prepared in step (1), the negative electrode sheet prepared in step (2), and an Al2O3 / PE / Al2O3 / PVDF (2μm + 12μm + 2μm + 1μm) separator are assembled into an 8Ah soft-pack battery cell, which is stacked, encapsulated, and baked for standby.

[0097] (4) In-situ polymerization to form a polymer electrolyte

[0098] In an environment with a dew point lower than -50°C, 0.8 g of polymerizable monomer A2, 0.159 g of additives (0.035 g of FEC, 0.05 g of VC, 0.04 g of LiPO2F2, 0.014 g of LiODFB, 0.02 g of DTD), 0.015 g of AIBN initiator, 2.5 g of lithium salt LiPF6, 4.43 g of EC, 5.86 g of EMC, and 4.81 g of DEC are mixed evenly to obtain a precursor solution. This precursor solution is injected into the battery cell and left standing for 8 hours, and then cured at 60°C for 6 hours to form an in-situ polymerized electrolyte.

[0099] Then, through processes such as formation, secondary sealing, and grading, an in-situ cured battery 2a is obtained, with an energy density of 332 Wh / kg.

[0100] Example 4

[0101] 0.01 mol of 5-fluoro-4-hydroxymethyl-1,3-dioxolan-2-one (1.35 g), 0.011 mol of isocyanatoethyl methacrylate, and 25 ml of ethyl acetate are mixed and added to a 50 ml three-necked flask. Stirring is started at a speed of 300 rpm, and an ethyl acetate solution containing 0.0557 g of stannous octoate is added dropwise through a constant pressure funnel. The reaction is carried out at 25°C for 8 hours, and then the solvent is removed by vacuum distillation at 40°C to obtain polymerizable monomer B2.

[0102] (Polymerizable monomer B2)

[0103] The battery 2b was prepared in a manner parallel to Example 3, except that: in step (4), "0.8 g of polymerizable monomer A2" was changed to "0.7 g of polymerizable monomer A2 and 0.1 g of polymerizable monomer B2", and the energy density of the prepared battery was 336 Wh / kg.

[0104] Comparative Example 2

[0105] The comparative battery 2 was prepared in a manner parallel to Example 3, except that: in step (4), the polymerizable monomer A2 and the AIBN initiator were not added, and the energy density of the prepared battery was 335 Wh / kg.

[0106] Electrical Property Test 2

[0107] The cyclic voltage range was 2.75 - 4.2 V, and the cycling mode was 0.5C / 1C.

[0108] The number of cycles when the capacity of battery 2a decayed to 80% of the initial capacity was 459 cycles.

[0109] The number of cycles when the capacity of battery 2b decayed to 80% of the initial capacity was 471 cycles.

[0110] The number of cycles when the capacity of the comparative battery 2 decayed to 80% of the initial capacity was 232 cycles.

[0111] Example 5

[0112] 0.012 mol of diethyl hydroxymethylphosphonate, 0.012 mol of isocyanatoethyl methacrylate, and 25 ml of dichloromethane were added to a 50 - ml three - necked flask, stirred for 3 hours, and a dichloromethane solution containing 0.02 g of stannous isooctanoate was added dropwise through a constant - pressure funnel. The reaction was carried out at 5°C for 8 hours, and then the solvent was removed by vacuum distillation at 25°C to obtain the polymerizable monomer A3.

[0113] (Polymerizable monomer A3)

[0114] (1) Preparation of the positive electrode plate

[0115] The positive electrode active material lithium cobaltate, the electronic conductive additive (carbon nanotubes and Super P), and PVDF were added to N - methylpyrrolidone in a mass ratio of 96:2:2. The solvent accounted for 65% of the total slurry mass. After mixing and stirring evenly, a positive electrode slurry with certain fluidity was obtained. The positive electrode slurry was coated on aluminum foil, dried, compacted, and cut to obtain a usable lithium cobaltate positive electrode plate.

[0116] (2) Preparation of the negative electrode plate

[0117] The negative electrode active material graphite, electronic conductive additives (carbon nanotubes and Super P), and binder (carboxymethyl cellulose and styrene-butadiene rubber) are added to the solvent deionized water at a ratio of 96:2:2, with the solvent accounting for 42% of the total slurry, and mixed and stirred evenly to obtain a negative electrode slurry with a certain fluidity. The negative electrode slurry is coated on copper foil, dried, compacted, and cut to obtain a usable graphite negative electrode sheet.

[0118] (3) Preparation of battery cells

[0119] The positive electrode sheet prepared in step (1), the negative electrode sheet prepared in step (2), and the PE / LATP (12 μm+2 μm) separator are assembled into an 8Ah soft-pack battery cell, which is then stacked, packaged, and baked for later use.

[0120] (4) In situ polymerization to form polymer electrolyte

[0121] In an environment with a dew point below -50°C, 0.4g of polymerizable monomer A3, 0.08g of additives (0.03g of FEC, 0.03g of VC, 0.02g of 1,3-PS), 0.01g of AIBN initiator, 2.76g of lithium salt LiODFB, 4.09g of EC, 6.12g of EMC, and 4.03g of DEC were mixed evenly to obtain a precursor solution. This precursor solution was injected into the battery cell and allowed to stand for 7 hours, and cured at 66°C for 8 hours to form an in-situ polymerized electrolyte.

[0122] Then, after the processes of formation, secondary sealing, and capacity division, the in-situ cured battery 3a was obtained, and its energy density was 276Wh / kg.

[0123] Example 6

[0124] 0.01 mol of 5,5-difluoro-4-hydroxy-1,3-dioxolane-2-one, 0.011 mol of acrylic acid and 25 ml of toluene were mixed and added into a 50 ml three-necked flask. After sufficient stirring, the temperature was raised to 100° C., and then 0.0216 g of a toluene solution of methylimidazole was added. The mixture was reacted at 105° C. for 5 hours, and then the solvent was removed by reduced pressure distillation at 100° C. to obtain a polymerizable monomer B3.

[0125] (Polymerizable Monomer B3)

[0126] Battery 3b was prepared in a manner similar to Example 5, except that in step (4), "0.4 g polymerizable monomer A3" was changed to "0.3 g polymerizable monomer A3 and 0.1 g polymerizable monomer B3", and the energy density of the prepared battery was 281 Wh / kg.

[0127] Comparative Example 3

[0128] The comparative cell 3 was prepared in a manner parallel to Example 5, except that: in step (4), the polymerizable monomer A3 and the AIBN initiator were not added. The energy density of the prepared cell was 278 Wh / kg.

[0129] Electrical Property Test 3

[0130] The cyclic voltage range was 2.75 - 4.45 V, and the cycling mode was 0.5C / 1C.

[0131] The number of cycles when the capacity of cell 3a decayed to 80% of the initial capacity was 463 cycles.

[0132] The number of cycles when the capacity of cell 3b decayed to 80% of the initial capacity was 486 cycles.

[0133] The number of cycles when the capacity of the comparative cell 3 decayed to 80% of the initial capacity was 242 cycles.

[0134] Example 7

[0135] 0.014 mol of dimethyl hydroxymethylphosphonate, 0.015 mol of isocyanatoethyl methacrylate, and 25 ml of toluene were mixed and added to a 50 ml three-necked flask, stirred for 3 hours, and a benzene solution containing 0.0217 g of stannous octoate was added dropwise through a constant pressure funnel, reacted at 30 °C for 10 hours, and then the solvent was removed by vacuum distillation at 50 °C to obtain the polymerizable monomer A4.

[0136] (Polymerizable monomer A4)

[0137] (1) Preparation of the positive electrode sheet

[0138] The ternary NCM811 as the positive electrode active material, the electronic conductive additive (carbon nanotubes and Super P), and PVDF were added to N-methylpyrrolidone in a mass ratio of 95:3:2, and the solvent accounted for 65% of the total slurry mass. After mixing and stirring evenly, a positive electrode slurry with certain fluidity was obtained. The positive electrode slurry was coated on aluminum foil, dried, compacted, and cut to obtain a usable NCM811 positive electrode sheet.

[0139] (2) Preparation of the negative electrode sheet

[0140] A 50 μm metal lithium foil was pressed onto a copper foil to serve as a metal lithium negative electrode.

[0141] (3) Preparation of the battery cell

[0142] Assemble the positive electrode sheet prepared in step (1), the negative electrode sheet prepared in step (2), and the PE / Al2O3 (12μm + 2μm) separator into an 8Ah soft-pack battery cell, and stack, package, and bake it for standby.

[0143] (4) In-situ polymerization to form a polymer electrolyte

[0144] In an environment with a dew point lower than -60°C, mix 1 g of polymerizable monomer A4, 0.15 g of additives (0.015 g of FEC, 0.035 g of VC, 0.1 g of LiNO3), 0.01 g of AIBN initiator, 2.90 g of lithium salt LiFSI, 4.43 g of EC, 4.86 g of EMC, and 4.81 g of DEC. After mixing evenly, a precursor solution is obtained. Inject this precursor solution into the battery cell and let it stand for 9 hours, then cure it at 60°C for 6 hours to form an in-situ polymerized electrolyte.

[0145] Then, through processes such as formation, secondary sealing, and grading, the battery 4a prepared by in-situ curing is obtained, and its energy density is 402 Wh / kg.

[0146] Example 8

[0147] Mix 0.019 mol of lithium fluorophosphate, 0.019 mol of isocyanatoethyl methacrylate, and 25 ml of benzene, add them to a 50 ml three-necked flask, stir for 4 hours, dropwise add an ethyl acetate solution containing 0.0990 g of triethylamine through a constant pressure funnel, react at 10°C for 8 hours, and then remove the solvent by vacuum distillation at 40°C to obtain polymerizable monomer B4.

[0148] (Polymerizable monomer B4)

[0149] Prepare battery 4b in a manner parallel to Example 7, with the difference that: in step (4), "1 g of polymerizable monomer A4" is changed to "0.75 g of polymerizable monomer A4 and 0.25 g of polymerizable monomer B4", and the energy density of the prepared battery is 403 Wh / kg.

[0150] Comparative Example 4

[0151] Prepare comparative battery 4 in a manner parallel to Example 7, with the difference that: in step (4), no polymerizable monomer A4 and AIBN initiator are added. The energy density of the prepared battery is 401 Wh / kg.

[0152] Electrical Property Test 4

[0153] The cyclic voltage range is 2.75 - 4.2 V, and the cycling mode is 0.3C / 0.3C.

[0154] The number of cycles when the capacity of battery 4a decays to 80% of its initial capacity is 260 cycles.

[0155] The number of cycles when the capacity of battery 4b decays to 80% of its initial capacity is 266 cycles.

[0156] The number of cycles when the capacity of the comparative battery 4 decays to 80% of its initial capacity is 197 cycles.

[0157] Example 9

[0158] Mix 0.012 mol of diethyl hydroxymethylphosphonate, 0.013 mol of ethyl acrylate isocyanate, and 25 ml of chloroform, add them to a 50 ml three-necked flask, stir for 1 hour, and dropwise add a chloroform solution containing 0.0766 g of stannous octoate through a constant pressure funnel. React at 10 °C for 10 hours, and then remove the solvent by vacuum distillation at 40 °C to obtain polymerizable monomer A5.

[0159] (Polymerizable monomer A5)

[0160] (1) Preparation of the positive electrode plate

[0161] Add the positive active material ternary NCM811, the electronic conductive additive (carbon nanotubes and Super P), and PVDF to N-methylpyrrolidone in a mass ratio of 95.5:2.7:1.8. The solvent accounts for 65% of the total slurry mass. Mix and stir evenly to obtain a positive electrode slurry with a certain fluidity. Coating the positive electrode slurry on aluminum foil, drying, compressing, and cutting to obtain a usable NCM811 positive electrode plate.

[0162] (2) Preparation of the negative electrode plate

[0163] Add the negative active material pure silicon (Si, particle size D50 = 3.5 μm), the electronic conductive additive (carbon nanotubes and Super P), and the binder (carboxymethyl cellulose and styrene-butadiene rubber) to deionized water as the solvent in a ratio of 92:4:4. The solvent accounts for 42% of the total slurry. Mix and stir evenly to obtain a negative electrode slurry with a certain fluidity. Coating the negative electrode slurry on copper foil, drying, compressing, and cutting to obtain a usable pure silicon negative electrode plate.

[0164] (3) Preparation of the battery cell

[0165] Assemble the positive electrode plate prepared in step (1), the negative electrode plate prepared in step (2), and the Al2O3 / PE / Al2O3 / PVDF (2 μm + 12 μm + 2 μm + 1 μm) separator into an 8 Ah soft-pack battery cell, and stack, package, and bake for standby.

[0166] (4) In-situ polymerization to form a polymer electrolyte

[0167] In an environment with a dew point below -50°C, 3g of polymerizable monomer A5, 0.159g of additives (0.035g of FEC, 0.05g of VC, 0.04g of LiPO2F2, 0.014g of LiODFB, 0.02g of DTD), 0.01g of AIBN initiator, 2.90g of lithium salt LiPF6, 1.82g of EC, 4.76g of EMC, and 4.28g of DMC were mixed evenly to obtain a precursor solution. This precursor solution was injected into the battery cell and allowed to stand for 8 hours, and cured at 70°C for 6 hours to obtain an in-situ polymerized electrolyte.

[0168] Then, after the processes of formation, secondary sealing, and capacity division, an in-situ cured battery 5a is obtained, whose energy density is 387Wh / kg.

[0169] Example 10

[0170] 0.019 mol of vinyl phosphate was dissolved in 20 ml of water, and after sufficient stirring, 0.038 mol of lithium hydroxide was added, and the mixture was reacted at 25°C for 2 hours. Water was removed by vacuum distillation at 60°C, and the mixture was dried to obtain polymerizable monomer B5.

[0171] (Polymerizable Monomer B5)

[0172] Battery 5b was prepared in a manner similar to Example 9, except that in step (4), "3 g polymerizable monomer A5" was changed to "2.6 g polymerizable monomer A5 and 0.4 g polymerizable monomer B5", and the energy density of the prepared battery was 363 Wh / kg.

[0173] Comparative Example 5

[0174] Comparative battery 5 was prepared in a manner similar to Example 9, except that no polymerizable monomer A5 and AIBN initiator were added in step (4). The energy density of the prepared battery was 366Wh / kg.

[0175] Electrical Property Test 5

[0176] The cycle voltage range is 2.75~4.2V, and the cycle mode is 0.5C / 1C.

[0177] The number of cycles when the capacity of the battery 5a decayed to 80% of the initial capacity was 274 cycles.

[0178] The number of cycles when the capacity of battery 5b decayed to 80% of the initial capacity was 301 cycles.

[0179] The number of cycles when the capacity of comparative battery 5 decayed to 80% of the initial capacity was 256 cycles.

[0180] Example 11

[0181] 0.012 mol of diethyl hydroxymethylphosphonate, 0.012 mol of 2-(2-methacryloyloxyethoxy)ethyl isocyanate, and 25 ml of chloroform were added to a 50-ml three-necked flask, stirred for 2 hours, and a chloroform solution containing 0.0882 g of stannous octoate was added dropwise through a constant-pressure funnel. The reaction was carried out at 5 °C for 6 hours, and then the solvent was removed by distillation under reduced pressure at 50 °C to obtain polymerizable monomer A6.

[0182] (Polymerizable monomer A6)

[0183] (1) Preparation of the positive electrode plate

[0184] The positive electrode active material, lithium-rich manganese-based Li 1.2 Ni 0.13 Mn 0.54 Co 0.13 O2 (abbreviation: lithium-rich), electronic conductive additives (carbon nanotubes and Super P), and PVDF were added to N-methylpyrrolidone in a mass ratio of 95.5:2.7:1.8. The solvent accounted for 65% of the total slurry by mass. After mixing and stirring evenly, a positive electrode slurry with certain fluidity was obtained. The positive electrode slurry was coated on aluminum foil, dried, compacted, and cut to obtain a usable lithium-rich positive electrode plate.

[0185] (2) Preparation of the battery cell

[0186] The lithium-rich positive electrode plate prepared in step (1), copper foil current collector, and PP (16 μm) separator were assembled into an 8 Ah non-negative soft-pack battery cell, which was stacked, encapsulated, and baked for standby.

[0187] (3) In-situ polymerization to form a polymer electrolyte

[0188] In an environment with a dew point lower than -50 °C, 1 g of polymerizable monomer A6, 0.112 g of additives (0.030 g of FEC, 0.045 g of VC, 0.037 g of LiPO2F2), 0.015 g of AIBN initiator, 2.30 g of lithium salt LiPF6, and 10.02 g of FDMB were mixed evenly to obtain a precursor solution. The precursor solution was injected into the battery cell and allowed to stand for 8 hours, and then cured at 55 °C for 15 hours to form an in-situ polymerized electrolyte.

[0189] Then, through processes such as formation, secondary sealing, and grading, the in-situ cured battery 6a was obtained, and its energy density was 517 Wh / kg.

[0190] Example 12

[0191] 0.01 mol of 1,2-oxathiol-4-ol-2,2-dioxide, 0.011 mol of methacrylic acid and 25 ml of xylene were mixed and added to a 50 ml three-necked flask. The mixture was stirred for 2 hours and then heated to 110 °C. Then, a xylene solution containing 0.0903 g of 4-dimethylaminopyridine was added dropwise through a constant pressure funnel, and the reaction was carried out at 100 °C for 6 hours. The solvent was removed by distillation under reduced pressure at 110 °C to obtain the polymerizable monomer B6.

[0192] (Polymerizable monomer B6)

[0193] Cell 6b was prepared in a manner parallel to Example 11, except that: in step (3), "1 g of polymerizable monomer A6" was changed to "0.6 g of polymerizable monomer A6 and 0.4 g of polymerizable monomer B6", and the energy density of the prepared cell was 514 Wh / kg.

[0194] Comparative Example 6

[0195] The comparative cell 6 was prepared in a manner parallel to Example 11, except that: in step (3), the polymerizable monomer A6 and the AIBN initiator were not added. The energy density of the prepared cell was 528 Wh / kg.

[0196] Electrical Property Test 6

[0197] The cyclic voltage range was 2.2 - 4.8 V, and the cycling mode was 0.5C / 1C.

[0198] The number of cycles when the capacity of cell 6a decayed to 80% of the initial capacity was 173 cycles.

[0199] The number of cycles when the capacity of cell 6b decayed to 80% of the initial capacity was 188 cycles.

[0200] The number of cycles when the capacity of the comparative cell 6 decayed to 80% of the initial capacity was 92 cycles.

[0201] Example 13

[0202] 0.012 mol of dimethyl hydroxymethylphosphonate, 0.012 mol of 3-isopropyl-dimethylbenzyl isocyanate, and 25 ml of dichloromethane were added to a 50 ml three-necked flask. The mixture was stirred for 1 hour, and a dichloromethane solution containing 0.041 g of stannous octoate was added dropwise through a constant pressure funnel. The reaction was carried out at 5 °C for 8 hours, and then the solvent was removed by distillation under reduced pressure at 25 °C to obtain the polymerizable monomer A7.

[0203] (Polymerizable monomer A7)

[0204] (1) Preparation of the positive electrode plate

[0205] The lithium-rich manganese-based Li 1.2 Ni 0.13 Mn 0.54 Co 0.13 O2 (referred to as lithium-rich), electronic conductive additives (carbon nanotubes and Super P), and PVDF are added to N-methylpyrrolidone in a mass ratio of 95:2.5:2.5. The solvent accounts for 65% of the total slurry by mass. After mixing and stirring evenly, a positive electrode slurry with certain fluidity is obtained. The positive electrode slurry is coated on aluminum foil, dried, compacted, and cut to obtain a usable lithium-rich positive electrode sheet.

[0206] (2) Preparation of negative electrode sheet

[0207] The negative electrode active material pure silicon (Si, particle size D50 = 3.5 μm), electronic conductive additives (carbon nanotubes and Super P), and binder (carboxymethyl cellulose and styrene-butadiene rubber) are added to deionized water as the solvent in a ratio of 95:2.5:2.5. The solvent accounts for 42% of the total slurry. After mixing and stirring evenly, a negative electrode slurry with certain fluidity is obtained. The negative electrode slurry is coated on copper foil, dried, compacted, and cut to obtain a usable pure silicon negative electrode sheet.

[0208] (3) Preparation of battery cell

[0209] The positive electrode sheet prepared in step (1), the negative electrode sheet prepared in step (2), and a PE / Al2O3 (12 μm + 2 μm) separator are assembled into an 8 Ah soft-pack battery cell, which is stacked, encapsulated, and baked for standby.

[0210] (4) In-situ polymerization to form a polymer electrolyte

[0211] In an environment with a dew point lower than -50 °C, 2 g of polymerizable monomer A7, 0.096 g of additives (0.020 g of FEC, 0.030 g of VC, 0.024 g of LiPO2F2, 0.022 g of LiPC2O2F4), 0.02 g of BPO initiator, 2.4 g of lithium salt LiBF4, 2.8 g of lithium salt LiBOB, 3.27 g of EC, 3.50 g of EMC, and 3.43 g of DEC are mixed evenly to obtain a precursor solution. This precursor solution is injected into the battery cell and left to stand for 5 hours, and then cured at 60 °C for 12 hours to form an in-situ polymerized electrolyte.

[0212] Then, through processes such as formation, secondary sealing, and grading, an in-situ cured battery 7a is obtained, with an energy density of 491 Wh / kg.

[0213] Example 14

[0214] 0.01 mol of 1,3,2-dioxolane-5-methyl 4-methoxyethylene glycol, 0.011 mol of acrylic acid and 25 ml of xylene were mixed and added to a 50 ml three-necked flask. After sufficient stirring, the temperature was raised to 110 °C, and then 0.055 g of concentrated acid was added dropwise through a constant pressure funnel. The reaction was carried out at 110 °C for 6 hours, and then the solvent was removed by distillation under reduced pressure at 110 °C to obtain polymerizable monomer B7.

[0215] (Polymerizable monomer B7)

[0216] Battery 7b was prepared in a manner parallel to Example 13, except that: in step (4), "2 g of polymerizable monomer A7" was changed to "1.8 g of polymerizable monomer A7 and 0.2 g of polymerizable monomer B7", and the energy density of the prepared battery was 488 Wh / kg.

[0217] Comparative Example 7

[0218] Comparative battery 7 was prepared in a manner parallel to Example 13, except that: in step (4), the polymerizable monomer A7 and the BPO initiator were not added. The energy density of the prepared battery was 495 Wh / kg.

[0219] Electrical Property Test 7

[0220] The cyclic voltage range is 2.75 - 4.5 V, and the cycling mode is 0.5C / 1C.

[0221] The number of cycles when the capacity of battery 7a decays to 80% of the initial capacity is 192 cycles.

[0222] The number of cycles when the capacity of battery 7b decays to 80% of the initial capacity is 223 cycles.

[0223] The number of cycles when the capacity of comparative battery 7 decays to 80% of the initial capacity is 179 cycles.

[0224] Example 15

[0225] 0.012 mol of dimethyl hydroxymethylphosphonate, 0.012 mol of 1-isocyanato-4-vinylbenzene, and 25 ml of dichloromethane were added to a 50 ml three-necked flask, stirred for 1 hour, and a dichloromethane solution containing 0.0342 g of stannous octoate was added dropwise through a constant pressure funnel. The reaction was carried out at 5 °C for 8 hours, and then the solvent was removed by distillation under reduced pressure at 25 °C to obtain polymerizable monomer A8.

[0226] (Polymerizable monomer A8)

[0227] (1) Preparation of the positive electrode plate

[0228] Lithium iron phosphate as the positive active material, electronic conductive additives (carbon nanotubes and Super P), and PVDF were added to N-methylpyrrolidone in a mass ratio of 95:2.5:2.5. The solvent accounted for 65% of the total slurry mass. After mixing and stirring evenly, a positive electrode slurry with certain fluidity was obtained. The positive electrode slurry was coated on aluminum foil, dried, compacted, and cut to obtain a usable lithium iron phosphate positive electrode plate.

[0229] (2) Preparation of the negative electrode plate

[0230] Graphite as the negative active material, electronic conductive additives (carbon nanotubes and Super P), and binders (carboxymethyl cellulose and styrene-butadiene rubber) were added to deionized water as the solvent in a ratio of 95:2.5:2.5. The solvent accounted for 42% of the total slurry mass. After mixing and stirring evenly, a negative electrode slurry with certain fluidity was obtained. The negative electrode slurry was coated on copper foil, dried, compacted, and cut to obtain a usable graphite negative electrode plate.

[0231] (3) Preparation of the battery cell

[0232] The positive electrode plate prepared in step (1), the negative electrode plate prepared in step (2), and a PE / Al2O3 (12μm + 2μm) separator were assembled into a 30Ah steel shell battery cell, which was then stacked, encapsulated, and baked for standby.

[0233] (4) In-situ polymerization to form a polymer electrolyte

[0234] In an environment with a dew point lower than -50°C, 2g of polymerizable monomer A8, 0.128g of additives (0.025g of FEC, 0.020g of VC, 0.025g of LiPO2F2, 0.020g of LiPC2O2F4, 0.038g of LiODFB), 0.02g of BPO initiator, 3.9g of lithium salt LiPF6, 4.8g of EC, 6.6g of EMC, and 5.2g of DMC were mixed evenly to obtain a precursor solution. This precursor solution was injected into the battery cell and left to stand for 10 hours, and then cured at 65°C for 12 hours to form an in-situ polymerized electrolyte.

[0235] Then, through processes such as formation, secondary sealing, and grading, an in-situ cured battery 8a was obtained, with an energy density of 176 Wh / kg.

[0236] Example 16

[0237] 0.01 mol of 1,3,2-dioxolane-4-methanol, 0.011 mol of acrylic acid and 25 ml of xylene were added to a 50 ml three-necked flask, stirred for 1 hour, heated to 110 °C, and then 0.0217 g of concentrated sulfuric acid was added dropwise through a constant pressure funnel. The reaction was carried out at 110 °C for 6 hours, and then the solvent was removed by distillation under reduced pressure at 110 °C to obtain the polymerizable monomer B8.

[0238] (Polymerizable monomer B8)

[0239] Battery 8b was prepared in a manner parallel to Example 15, except that: in step (4), "2 g of polymerizable monomer A8" was changed to "1.8 g of polymerizable monomer A8 and 0.2 g of polymerizable monomer B8", and the energy density of the prepared battery was 175 Wh / kg.

[0240] Comparative Example 8

[0241] Comparative battery 8 was prepared in a manner parallel to Example 15, except that: in step (4), the polymerizable monomer A8 and the BPO initiator were not added. The energy density of the prepared battery was 179 Wh / kg.

[0242] Electrical Property Test 8

[0243] The cyclic voltage range is 2.5 - 3.7 V, and the cycling mode is 0.5C / 1C.

[0244] The number of cycles when the capacity of battery 8a decays to 80% of the initial capacity is 3575 cycles.

[0245] The number of cycles when the capacity of battery 8b decays to 80% of the initial capacity is 3692 cycles.

[0246] The number of cycles when the capacity of comparative battery 8 decays to 80% of the initial capacity is 2894 cycles.

[0247] Example 17

[0248] (1) Preparation of the positive electrode sheet

[0249] The positive electrode active material ternary NCM811, the electronic conductive additive (carbon nanotubes and Super P), and PVDF were added to N-methylpyrrolidone in a mass ratio of 95:3:2. The solvent accounted for 65% of the total slurry mass, and the mixture was stirred evenly to obtain a positive electrode slurry with certain fluidity. The positive electrode slurry was coated on aluminum foil, dried, compacted, and cut to obtain a usable NCM811 positive electrode sheet.

[0250] (2) Preparation of the negative electrode sheet

[0251] The negative electrode active material silicon oxycarbide 450 (SiOC, specific capacity 450 mAh / g), electronic conductive additives (carbon nanotubes and Super P), and binder (carboxymethyl cellulose and styrene-butadiene rubber) were added to deionized water as a solvent in a ratio of 95:2.5:2.5. The solvent accounted for 42% of the total slurry. After mixing and stirring evenly, a negative electrode slurry with a certain fluidity was obtained. The negative electrode slurry was coated on a copper foil, dried, compacted, and cut to obtain a usable silicon oxycarbide negative electrode sheet.

[0252] (3) Preparation of the battery cell

[0253] The positive electrode sheet prepared in step (1), the negative electrode sheet prepared in step (2), and an Al2O3 / PE / Al2O3 / PVDF (2μm + 12μm + 2μm + 1μm) separator were assembled into an 8 Ah soft-pack battery cell, which was then stacked, encapsulated, and baked for standby.

[0254] (4) In-situ polymerization to form a polymer electrolyte

[0255] In an environment with a dew point below -50°C, 0.8 g of polymerizable monomer A2, 0.005 g of initiator AIBN, and 24 g of commercial electrolyte (No. 102 electrolyte from Xianghe Kunlun Chemical Products Co., Ltd.) were mixed evenly to obtain a precursor solution. This precursor solution was injected into the battery cell and allowed to stand for 8 hours, and then cured at 60°C for 8 hours to form an in-situ polymerized electrolyte.

[0256] Then, through processes such as formation, secondary sealing, and grading, the battery 9a prepared by in-situ curing was obtained, with an energy density of 282 Wh / kg.

[0257] Example 18

[0258] The battery 9b was prepared in a manner parallel to Example 17, with the difference that in step (4), "0.8 g of polymerizable monomer A2" was changed to "0.7 g of polymerizable monomer A2 and 0.1 g of polymerizable monomer B1". The energy density of the prepared battery was 279 Wh / kg.

[0259] Comparative Example 9

[0260] The comparative battery 9 was prepared in a manner parallel to Example 17, with the difference that in step (4), the polymerizable monomer A2 and the AIBN initiator were not added. The energy density of the prepared battery was 285 Wh / kg.

[0261] Electrical Property Test 9

[0262] The cycling voltage range is 2.75 - 4.2 V, and the cycling mode is 0.5C / 1C.

[0263] The number of cycles when the capacity of battery 9a decays to 80% of its initial capacity is 1379 cycles.

[0264] The number of cycles when the capacity of battery 9b decays to 80% of its initial capacity is 1471 cycles.

[0265] The number of cycles when the capacity of comparative battery 9 decays to 80% of its initial capacity is 1373 cycles.

[0266] Safety Performance Test of Lithium Secondary Battery

[0267] The following safety performance tests were carried out on batteries 1a - 9a and 1b - 9b prepared in Examples 1 - 18 and comparative batteries 1 - 9 prepared in Comparative Examples 1 - 9, and the test results are shown in Table 1.

[0268] Hot box test: The battery was placed in the test chamber when it was fully charged (100% SOC). The test chamber was heated at a heating rate of 5°C / min. When the temperature in the chamber reached 150°C, it was kept constant for 1 h and then cooled to RT. During the whole process, if the battery did not smoke, catch fire, or explode, it passed the test.

[0269] Overcharge test: The battery was charged to 1.5 times the upper cut-off voltage. If the battery did not catch fire or explode, it passed the test.

[0270] Crush test: After the battery was fully charged, it was placed between two planes and crushed perpendicular to the plate direction at a rate of 2 mm / s. The crushing stopped when the voltage reached 0 V or the battery deformation reached 50%. If the battery did not catch fire or explode during the crushing process, it passed the test.

[0271] Penetration test: The test was carried out when the battery was fully charged (100% SOC). A 5 - mm high-temperature resistant steel needle was used to vertically penetrate the center of the battery at a speed of 25 mm / s and stay for 1 h. If the battery did not catch fire or explode, it passed the test. Exemplarily, Figure 6 Comparison photos of the penetration test results of comparative battery 2 (left) and battery 2a (right) are given.

[0272] Table 1

[0273] Battery Hot Box Test Overcharge Test Crush Test Pin Prick Test Result Battery 1a Passed Passed Passed Passed Battery 1b Passed Passed Passed Passed Comparative Battery 1 Failed Failed Passed Failed Battery 2a Passed Passed Passed Passed Battery 2b Passed Passed Passed Passed Comparative Battery 2 Failed Failed Failed Failed Battery 3a Passed Passed Passed Passed Battery 3b Passed Passed Passed Passed Comparative Battery 3 Failed Failed Failed Failed Battery 4a Passed Passed Passed Passed Battery 4b Passed Passed Passed Passed Comparative Battery 4 Failed Failed Failed Failed Battery 5a Passed Passed Passed Passed Battery 5b Passed Passed Passed Passed Comparative Battery 5 Failed Failed Failed Failed Battery 6a Passed Passed Passed Passed Battery 6b Passed Passed Passed Passed Comparative Battery 6 Failed Failed Failed Failed Battery 7a Passed Passed Passed Passed Battery 7b Passed Passed Passed Passed Comparative Battery 7 Failed Failed Failed Failed Battery 8a Passed Passed Passed Passed Battery 8b Passed Passed Passed Passed Comparative Battery 8 Failed Passed Failed Passed Battery 9a Passed Passed Passed Passed Battery 9b Passed Passed Passed Passed Comparative Battery 9 Failed Failed Passed Failed

[0274] From the test results of the electrochemical performance and safety performance of the example batteries and the comparative example batteries, it can be seen that in the battery systems with high-nickel ternary, high-voltage lithium cobaltate, lithium-rich manganese-based, and lithium iron phosphate as the positive electrode, and graphite, SiOC450, SiOC600, metallic lithium, pure silicon, and lithium-free as the negative electrode, compared with the comparative example batteries (i.e., conventional liquid batteries), the energy density of the example batteries (batteries with in-situ cured monomers added) only decreases slightly, but the cycle stability performance of the example batteries is significantly improved; the cycle performance of the example batteries with both monomer A and monomer B in the precursor solution is slightly better than that of the example batteries without monomer B in the precursor solution; in the 150°C hot box test, overcharge test, extrusion test, and pinprick test, all the example batteries passed the test, while the comparative example batteries generally could not pass. This indicates that the electrolyte prepared by in-situ curing of the polymerizable monomer in the present invention has better safety performance, and thus the in-situ cured battery prepared has excellent safety performance.

[0275] It should be noted that the polymerizable monomer A, or the mixture of polymerizable monomer A and polymerizable monomer B in the present invention can also be directly used in combination with commercial electrolytes, and excellent effects can still be obtained (Examples 17-18), indicating that the polymerizable monomers of the present invention have good compatibility with various electrolytes. In addition, although specific combinations such as the combination of polymerizable monomer A1 and polymerizable monomer B1, and the combination of polymerizable monomer A2 and polymerizable monomer B2 are used to prepare the electrolyte in the examples, the combination methods given as examples are not necessary to achieve the purpose of the invention, and any combination methods such as the combination of polymerizable monomer A1 and polymerizable monomer B3, and the combination of polymerizable monomer A4 and polymerizable monomer B2 can also be used.

[0276] In summary, the present invention prepares an electrolyte by in-situ curing of a highly safe polymerizable monomer A or a mixture of polymerizable monomer A and polymerizable monomer B, significantly improving the safety performance of the battery while maintaining the electrochemical performance of the battery.

[0277] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments described herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A polymer electrolyte, characterized in that, The polymer electrolyte is formed by in-situ polymerization of a precursor solution containing a polymerizable monomer, a lithium salt, an organic solvent, and an initiator, wherein the polymerizable monomer includes a polymerizable monomer A represented by formula (I): (I) wherein, L 1 and L 2 are independently selected from none, C 1-18 alkylene or heteroatom-containing C 1-18 alkylene, wherein said C 1-18 alkylene is optionally substituted by one or more R a substituents; R 1 selected from H, C 1-18 hydrocarbyl or heteroatom-containing C 1-18 hydrocarbyl, wherein said C 1-18 hydrocarbyl is optionally substituted by one or more R a substituted; R 2 and R 3 are independently selected from C 1-15 alkyl, said C 1-15 alkyl is optionally substituted with one or more R a substituents R a Selected from halogen, C 1-10 hydrocarbyl or heteroatom-containing C 1-10 hydrocarbyl, hydroxyl, =O, =S, aldehyde group, carbonate group, formyl group, carboxyl group, ester group, peroxy group, amino group, imino group, imide group, azo group, nitrate group, phosphate group, thioether group, disulfide group, cyano group, sulfonic acid group, sulfonyl group, amide group, nitro group, pyridyl group, acyloxy group, phenyl group, phenoxy group, benzyl group, benzyloxy group, acetyl group, benzoyl group, benzyloxycarbonyl group, and groups in which one or more H thereof are substituted by halogen.

2. The polymer electrolyte according to claim 1, wherein In the polymerizable monomer A represented by formula (I), L 1 and L 2 are independently selected from none, C 1-10 -chain alkylene, heteroatom-containing C 1-10 -chain alkylene, C 3-10 -cycloalkylene or heteroatom-containing C 3-10 -cycloalkylene, and these groups are optionally substituted by one or more R a substituents; R 1 selected from H, C 1-10 alkyl, heteroatom-containing C 1-10 alkyl, C 3-10 cycloalkyl or heteroatom-containing C 3-10 cycloalkyl, and these groups are optionally substituted by one or more R a substituted.

3. The polymer electrolyte according to claim 1, wherein, In the polymerizable monomer A represented by formula (I), L 1 and L 2 are independently selected from none, C 1-6 chain alkylene, heteroatom-containing C 1-6 chain alkylene, C 3-8 cycloalkylene or heteroatom-containing C 3-8 cycloalkylene, and these groups are optionally substituted by one or more R a substituents; R 1 selected from H, C 1-6 hydrocarbyl, heteroatom-containing C 1-6 hydrocarbyl, C 3-8 cycloalkyl or heteroatom-containing C 3-8 cycloalkyl, and these groups are optionally substituted by one or more R a substituents.

4. The polymer electrolyte according to claim 1, wherein In the polymerizable monomer A represented by formula (I), R 2 and R 3 are independently selected from C 1-10 alkyl, and the C 1-10 alkyl is optionally substituted by one or more R a .

5. The polymer electrolyte according to claim 4, wherein, R 2 and R 3 are independently selected from C 1-6 alkyl groups.

6. The polymer electrolyte according to claim 1, wherein, In the precursor solution, the mass fraction of the polymerizable monomer is 0.5% - 50%; the mass fraction of the lithium salt is 5% - 30%; the mass fraction of the organic solvent is 1% - 92%; the mass fraction of the initiator is 0.001% - 0.5%.

7. The polymer electrolyte according to claim 5, wherein, The mass fraction of the polymerizable monomer is 1% - 20%; the mass fraction of the lithium salt is 8% - 20%; the mass fraction of the organic solvent is 50 - 90%; the mass fraction of the initiator is 0.005% - 0.3%.

8. The polymer electrolyte according to claim 1, wherein The mass fraction of the polymerizable monomer A in the polymerizable monomer is 5% - 100%.

9. The polymer electrolyte according to claim 8, wherein The mass fraction of the polymerizable monomer A in the polymerizable monomer is 50% - 100%.

10. The polymer electrolyte according to claim 1, wherein, The lithium salt is selected from one or more of lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalate borate, lithium bis(oxalate) borate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium trifluoromethylbenzenesulfonate, lithium difluorophosphate, lithium difluorobis(oxalate) phosphate, and lithium tetrafluorooxalate phosphate; The organic solvent is selected from one or more of ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, ethylene vinylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl formate, ethyl formate, propyl formate, butyl formate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, δ-valerolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 2-methyl-1,3-dioxolane, ethylene glycol dimethyl ether, polyethylene glycol, sulfolane, triethylene glycol dimethyl ether, fluorinated 1,4-dimethoxybutane, bis(2,2,2-trifluoroethyl) ether, tetramethylsilane, and tetraethylene glycol dimethyl ether; The initiator is selected from one or more of azobisisobutyronitrile, azobisisoheptonitrile, dimethyl azobisisobutyrate, benzoyl peroxide, tert-butyl perbenzoate, and methyl ethyl ketone peroxide.

11. The polymer electrolyte according to any one of claims 1 to 10, wherein The polymerizable monomer further includes a polymerizable monomer B represented by formula (II): (II) Among them, R 6 is selected from , , , , and ; R 4 and R7 to R 10 are independently selected from H, C 1-18 hydrocarbyl or heteroatom-containing C 1-18 hydrocarbyl, wherein said C 1-18 hydrocarbyl is optionally substituted by one or more R a substituents; R 5 selected from none, C 1-18 alkylene or heteroatom-containing C 1-18 alkylene, wherein said C 1-18 alkylene is optionally substituted by one or more R a substituents.

12. The polymer electrolyte according to claim 11, wherein, In the polymerizable monomer B represented by formula (II): R 4 and R7 to R 10 are independently selected from H, C 1-10 alkyl, heteroatom-containing C 1-10 alkyl, C 3-10 cycloalkyl or heteroatom-containing C 3-10 cycloalkyl, and these groups are optionally substituted by one or more R a substituents; R 5 selected from none, C 1-10 chain alkylene, heteroatom-containing C 1-10 chain alkylene, C 3-10 cycloalkylene or heteroatom-containing C 3-10 cycloalkylene, and these groups are optionally substituted by one or more R a substituents.

13. The polymer electrolyte according to claim 12, wherein, R 4 and R7 to R 10 are independently selected from H, C 1-6 alkyl, heteroatom-containing C 1-6 alkyl, C 3-8 cycloalkyl or heteroatom-containing C 3-8 cycloalkyl, and these groups are optionally substituted by one or more R a substituents.

14. The polymer electrolyte according to claim 12, wherein, R 5 selected from none, C 1-6 chain alkylene, heteroatom-containing C 1-6 chain alkylene, C 3-8 cycloalkylene or heteroatom-containing C 3-8 cycloalkylene, and these groups are optionally substituted by one or more R a substituents.

15. The polymer electrolyte according to claim 11, wherein, The mass ratio of the polymerizable monomer B to the polymerizable monomer A is greater than 0 to 20.

16. The polymer electrolyte according to claim 15, wherein, The mass ratio of the polymerizable monomer B to the polymerizable monomer A is greater than 0 to 1.

17. The polymer electrolyte according to any one of claims 1 to 10, wherein, The polymer electrolyte further includes an electrolyte additive, and the electrolyte additive is selected from one or more of fluoroethylene carbonate, vinylene carbonate, trimethyl phosphate, triethyl phosphate, succinic anhydride, 18-crown-6, triphenyl phosphite, ethylene ethylene carbonate, trimethyl borate, lithium difluorobis(oxalato)phosphate, lithium tetrafluorobis(oxalato)phosphate, tributyl phosphate, biphenyl, ethylene sulfite, difluorodiphenylsilane, lithium bis(fluorosulfonyl)imide, tributyl borate, ethoxypentafluorocyclotriphosphazene, ethylene sulfate, lithium nitrate, 1,3-propane sultone, lithium difluorophosphate, diethyl sulfite, and succinonitrile.

18. A method for preparing the polymer electrolyte according to any one of claims 1 to 17, characterized in that, The preparation method includes: (1) Under a humidity with a dew point lower than -45°C, mixing a polymerizable monomer, a lithium salt, an organic solvent, an initiator, and an optional electrolyte additive to obtain a precursor solution; or mixing the polymerizable monomer and the initiator with a lithium secondary battery electrolyte to obtain a precursor solution; (2) Subjecting the precursor solution obtained in step (1) to in-situ polymerization at 45 to 85°C to form the polymer electrolyte.

19. The preparation method according to claim 18, wherein the time for the in-situ polymerization is 2 to 24 h.

20. A lithium secondary battery, the lithium secondary battery comprising a battery cell, an electrolyte, and a packaging case, the battery cell including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, characterized in that, The electrolyte is the polymer electrolyte according to any one of claims 1 to 17 or the polymer electrolyte prepared by the preparation method according to claim 18 or 19.

21. A method for preparing a lithium secondary battery, characterized in that, The preparation method includes: Manufacturing an electric core by laminating or winding a positive electrode sheet, a negative electrode sheet, and a separator, and placing the electric core in a packaging case; Injecting the precursor solution into the packaging case, fully infiltrating the electric core, and then subjecting it to in-situ polymerization at 45 to 85°C to form the polymer electrolyte according to any one of claims 1 to 17, thereby obtaining the lithium secondary battery, wherein the precursor solution is the precursor solution for in-situ polymerization to generate the polymer electrolyte according to any one of claims 1 to 17.

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