Nitrile fast-charging polymer electrolyte and secondary lithium battery

Abstract

The invention provides a nitrile fast-charging polymer electrolyte and a secondary lithium battery, and relates to the technical field of secondary batteries. The nitrile fast-charging polymer electrolyte comprises an electrolyte matrix and a lithium salt, wherein the electrolyte matrix comprises a polymeric monomer, a nitrile compound, a functional additive and other plasticizers; the polymeric monomer comprises at least one of compounds shown in a formula (I): # imgabs0 #, wherein X is N or O; when X is N, R1, R2 and R3 are independently selected from hydrogen atoms, halogen, cyano groups or alkyl groups with 1-8 carbon atoms, alkoxy groups and fluoroalkyl groups; and when X is O, R1, R2 and R3 are independently selected from hydrogen atom, halogen, cyano group or alkyl group with 1-8 carbon atoms, alkoxy group and fluoroalkyl group. The nitrile compound is added into the nitrile polymer as a plasticizer, so that the plasticizing effect of the polymer is more easily broken, the generation of nitrogen-containing species on positive and negative electrode interfaces is facilitated, the overall polarity of the electrolyte is improved, and the long cycle performance of the lithium battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary batteries, and particularly to a nitrile-based fast-charging polymer electrolyte and a secondary lithium battery. Background Art

[0002] Solid polymer lithium batteries are expected to replace liquid lithium-ion batteries due to their advantages such as high specific energy and high safety. The earliest research on solid polymer electrolytes was the complex of polyethylene oxide (PEO) and alkali metal ions, whose ionic conductivity reached 10 -5 S / cm at 40 - 60 °C, and it had good film-forming properties and could be used as a lithium-ion battery electrolyte. Subsequently, a series of new polymer electrolytes have been gradually developed, such as polyvinyl chloride (PVC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVDF), vinylidene fluoride hexafluoropropylene copolymer (PVDF-HFP), polyethylene oxide (PEO), polymethyl methacrylate (PMMA), etc. However, there are supramolecular interactions similar to hydrogen bonds and van der Waals forces between such polymer segments, resulting in a relatively high crystallinity, which in turn reduces the ionic conductivity of the polymer electrolyte. Therefore, how to solve this problem of polymer electrolytes has become the research focus in lithium-ion batteries.

[0003] Plasticizers can be inserted between polymer molecular chains, thereby weakening the stress between polymer molecular chains, increasing the mobility of polymer molecular chains and reducing their crystallinity. The existing polymer electrolyte plasticizers are mainly carbonate and ether compounds. However, the polarity of C=O in carbonates and C-O in ether solvents is relatively low, resulting in poor plasticizing effects on the target polymer and limited improvement in ionic conductivity, making it difficult to achieve the improvement of battery fast-charging performance. Therefore, it is necessary to develop a new polymer electrolyte. Summary of the Invention

[0004] The purpose of the present invention is to provide a nitrile-based fast-charging polymer electrolyte and a secondary lithium battery for the deficiencies of the existing technology.

[0005] To achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0006] On the one hand, a nitrile-based fast-charging polymer electrolyte, comprising: an electrolyte matrix and a lithium salt; wherein, the electrolyte matrix comprises the following raw materials in parts by weight:

[0007] (a) 1 - 60 parts of a polymerization monomer, and the polymerization monomer is selected from at least one of the compounds shown in the structural formula as formula (I):

[0008]

[0009] In formula (I), X is N or O; when X is N, R1, R2, and R3 are independently selected from a hydrogen atom, a halogen, a cyano group, or an alkyl group, an alkoxy group, a fluoroalkyl group having 1 to 8 carbon atoms; when X is O, there is no R1, and R2 and R3 are independently selected from a hydrogen atom, a halogen, a cyano group, or an alkyl group, an alkoxy group, a fluoroalkyl group having 1 to 8 carbon atoms;

[0010] (b) 1 to 30 parts of a nitrile compound, and the nitrile compound is selected from at least one of the compounds represented by the structural formula (II):

[0011]

[0012] In formula (II), n = 0 to 4, and R1, R2, and R3 are independently selected from a hydrogen atom, a cyano group, or an alkyl group having 1 to 8 carbon atoms;

[0013] (c) 0.1 to 5 parts of a functional additive;

[0014] (d) 0.1 to 20 parts of other plasticizers.

[0015] Preferably, the nitrile compound is a compound A and a compound B with a volume ratio of (0.5:9.5) to (9.5:0.5), preferably 1:1; wherein, both the compound A and the compound B are selected from the compounds represented by the structural formula (I); the compound A is selected from at least one of acetonitrile, propionitrile, isobutyronitrile, trimethylacetonitrile, butyronitrile, and succinonitrile; the compound B is selected from at least one of valeronitrile, glutarodinitrile, adiponitrile, 2-methylmalononitrile, 1,3,5-cyclohexanetricarbonitrile, and 1,3,6-hexanetricarbonitrile.

[0016] Preferably, the polymerization monomer is selected from any one of the following compounds;

[0017]

[0018] Furthermore, the polymerization monomer further includes other polymerization monomers; optionally, the other polymerization monomers are selected from any one or a combination of a carbonate, a carboxylate, a fluorocarbonate, a fluorocarboxylate, a sulfonate, a sulfate, an ether, a fluoroether, and an imide containing a carbon-carbon double bond or an epoxy structure.

[0019] Preferably, the other polymerizable monomers are selected from one or a combination of more than one of acrylate, acrylonitrile, vinyl phosphate, 2-methylene butyrolactone, diethyl itaconate, itaconate ester, vinyl acetate, allyl acetate, ethyl allyl carbonate, propynyl methanesulfonate, vinyl sulfate, maleimides, vinyl sulfite, glycidyl acrylate, glycidyl 4-hydroxybutyl acrylate ether, tris(propylene glycol) glycerol diacrylate, acrylonitrile, 2-cyanoethyl acrylate, allyl cyanoacetate, 2-ethoxyethyl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, 1,4-butanediol diacrylate, 2-methylene butyrolactone, diethyl itaconate, dimethyl vinyl phosphate, diethyl vinyl phosphate, tetrahydrofurfuryl acrylate, methyl methacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, n-butyl acrylate, polyethylene glycol dimethacrylate, ethyl cyanoacrylate, 2-hydroxyethyl 2-methyl-2-propenoate phosphate, ethoxylated trimethylolpropane triacrylate, trifluoroethyl acrylate, 2-(perfluorooctyl)ethyl methacrylate, hexafluorobutyl methacrylate, vinyl acetate, allyl acetate, ethyl allyl carbonate, propynyl methanesulfonate, vinyl sulfate, maleimides, vinyl sulfite.

[0020] More preferably, the other polymerizable monomers are selected from any one of glycidyl acrylate, glycidyl 4-hydroxybutyl acrylate ether, acrylonitrile, 2-ethoxyethyl methacrylate, 1,4-butanediol diacrylate, dimethyl vinyl phosphate, ethoxylated trimethylolpropane triacrylate, 2-(perfluorooctyl)ethyl methacrylate, hexafluorobutyl methacrylate, allyl acetate.

[0021] More preferably, the polymerizable monomers comprise the compound shown in formula (I) and other polymerizable monomers in a molar ratio of (5 - 9.5):(0.5 - 5).

[0022] Furthermore, the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium tetrafluoroborate, lithium difluoro(oxalato)borate. The weight content of the lithium salt in the electrolyte is 10% - 35%.

[0023] Further, the functional additive is selected from any one or more combinations of organic lithium phosphate salts, lithium sulfonimide salts, organic lithium borate salts, carbonates, phosphates, and inorganic lithium compounds; preferably, the functional additive is selected from any one or more combinations of lithium difluorophosphate, lithium difluorobisoxalate phosphate, lithium tetrafluorooxalate phosphate, lithium bisoxalate borate, fluoroalkoxy lithium trifluoroborate, lithium bis(perfluoropinacolyl)borate, fluoroethylene carbonate, vinylene carbonate, 1,3-propane sultone, tris(trimethylsilyl) phosphate, tris(trimethylsilyl) phosphite, lithium fluoride, lithium oxide, lithium nitride, lithium carbonate, and lithium nitrate.

[0024] Further, the other plasticizer is selected from at least one of carbonate, γ-butyrolactone, cyclopentane, and organic acid esters with 1 to 4 carbon atoms; optionally, the carbonate can be propylene carbonate, ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, etc., and the organic acid esters with 1 to 4 carbon atoms can be methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, etc.; preferably, the other plasticizer is selected from at least one of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and γ-butyrolactone.

[0025] Furthermore, the nitrile fast-charging polymer electrolyte also contains an initiator and a catalyst.

[0026] Optionally, the initiator includes but is not limited to any one of azo, peroxide, N,N-dimethylbenzene, n-butyl lithium, lithium powder, and sodium naphthalene; the azo may be azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, etc., the peroxide may be dibenzoyl peroxide, diisopropyl peroxide, di-tert-butyl peroxide, isopropyl hydroperoxide, tert-butyl hydroperoxide, diisopropyl peroxydicarbonate, potassium persulfate, etc.; the amount of the initiator used is 0 to 5% of the total mass of the polymerization monomer.

[0027] Optionally, the catalyst includes but is not limited to at least one of dibutyltin dilaurate, bis(dimethylaminoethyl)ether, pentamethyldiethylenetriamine, dimethylcyclohexylamine, organic bismuth or triazine trimerization; the amount of the catalyst used is 0 to 5% of the total mass of the polymerized monomers.

[0028] On the other hand, a secondary lithium battery comprises the nitrile fast-charging polymer electrolyte described above.

[0029] Furthermore, the secondary lithium battery also includes a positive electrode and a negative electrode.

[0030] Preferably, the positive electrode active material includes, but is not limited to, any one of lithium iron phosphate, lithium manganate, NCA, NCM ternary material, lithium cobaltate, and lithium nickel manganate.

[0031] Further, the negative electrode active material includes, but is not limited to, any one of graphite, hard carbon, molybdenum disulfide, lithium titanate, graphene, and silicon carbon.

[0032] On the other hand, the preparation method of the above secondary lithium battery includes two polymerization methods, in-situ and non-in-situ, and the optimal one is the in-situ polymerization method; the steps of the preparation method of the secondary lithium battery are as follows:

[0033] (1) Mix a nitrile polymer monomer, a nitrile compound, a lithium salt, a functional additive, and other plasticizers and stir evenly to prepare a homogeneous solid polymer precursor solution;

[0034] (2) Add an initiator and a catalyst to the precursor solution and mix evenly, and inject it into a lithium-ion battery containing positive and negative electrodes; then place the battery in an incubator for in-situ polymerization to prepare a solid electrolyte; or scrape the precursor solution onto a porous support material, and then place it in an incubator for non-in-situ polymerization to prepare a solid electrolyte membrane.

[0035] Further, in step (2), during the in-situ polymerization process, the constant temperature time is 8-48 h and the temperature is 20-80 °C; during the non-in-situ polymerization, the constant temperature time is 8-48 h and the temperature is 20-80 °C.

[0036] Further, in step (2), the porous support material is one or more of polyimide, aramid, poly(arylene sulfone amide), glass fiber, flame-retardant cellulose, and alginate.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. The present invention provides a nitrile fast-charging polymer electrolyte, which uses a nitrile compound as a plasticizer and introduces a nitrile polymer, achieving an order-of-magnitude increase in ionic conductivity and improving the fast-charging and rate performance of the solid polymer electrolyte.

[0039] 2. In the nitrile fast-charging polymer electrolyte of the present invention, by adding two nitrile compounds as plasticizers, the cyano group C≡N in the nitrile compound belongs to an sp hybrid group, which is more easily polarized than C=O and C-O, and is more likely to break the polymer plasticization effect as a plasticizer; it is beneficial to the formation of nitrogen-containing species at the positive and negative electrode interfaces, is beneficial to improving the overall polarity of the electrolyte, and enhances the long-cycle performance of the battery.

[0040] 3. In the nitrile fast-charging polymer electrolyte of the present invention, by adding a nitrile polymer monomer and polymerizing it into a nitrile polymer in-situ or non-in-situ, it helps to improve the safety performance of the lithium secondary battery.

[0041] 4. The nitrile-based fast-charging polymer electrolyte of the present invention has a lithium ion conductivity of up to 8×10 -3 S / cm or more. Description of the Drawings

[0042] Figure 1 It is a schematic diagram of the rate performance test results of the NCM811 / / Gr full cell assembled in Example 1;

[0043] Figure 2 It is a fast-charging long cycle diagram of the NCM811 / / Gr full cell assembled in Example 1 under 8C conditions;

[0044] Figure 3 It is a long cycle diagram of the NCM811 / / Gr full cell assembled in Example 1 under 1C conditions;

[0045] Figure 4 It is a long cycle diagram of the LiCoO2 / / Gr full cell assembled in Example 13 under 8C conditions;

[0046] Figure 5 It is the long cycle diagram of the LiNi 0.90 Co 0.05 Mn 0.05 O2 / / SC650 (silicon carbon 650) full cell under 8C conditions. Detailed Embodiments

[0047] The following non-limiting examples can enable those of ordinary skill in the art to more comprehensively understand the present invention, but do not limit the present invention in any way. The following content is only an exemplary illustration of the scope claimed by the present invention. Those skilled in the art can make various changes and modifications to the invention of the present invention based on the disclosed content, and it should also fall within the scope claimed by the present invention.

[0048] In the specific embodiments of the present invention, the polymerization monomer preparation reaction formula is as follows:

[0049]

[0050] Among them, R1, R2, and R3 are independently selected from a hydrogen atom, a halogen, a cyano group, or an alkyl group, an alkoxy group, or a fluoroalkyl group having 1 to 8 carbon atoms;

[0051] Or

[0052]

[0053] Among them, R2 and R3 are independently selected from a hydrogen atom, a halogen, a cyano group, or an alkyl group, an alkoxy group, or a fluoroalkyl group having 1 to 8 carbon atoms.

[0054] In the following specific embodiments, the polymerization monomers are 2a, 2b, and 2c with the following structural formulas in sequence:

[0055] This does not limit the present application.

[0056] The present invention will be further described below by way of specific embodiments. All the various chemical reagents used in the embodiments of the present invention are obtained through conventional commercial channels unless otherwise specified.

[0057] Example 1

[0058] Under anhydrous and anaerobic conditions, 0.035 mol of the polymerization monomer compound 2a, 0.005 mol of glycidyl acrylate, and 5.1 g of lithium bis(fluorosulfonyl)imide were mixed and added to a mixed solution of 3 mL of ethylene carbonate, 3 mL of dimethyl carbonate, 6 mL of isobutyronitrile, and 6 mL of 2-methylmalononitrile. After mixing evenly, a homogeneous solution was obtained; then 1,3-propanesultone (the addition amount is 1% of the mass of the homogeneous solution) as a functional additive was added to the homogeneous solution to obtain a precursor solution, and azobisisobutyronitrile (0.5% of the mass of the polymerization monomer) and dibutyltin dilaurate (0.5% of the mass of the polymerization monomer) were added. After the solution was stirred evenly, the electrolyte was assembled into a LiNi 0.8 Co 0.1 Mn 0.1 / Gr battery and a steel sheet (SS) / steel sheet (SS) symmetric battery. The assembled battery was placed in a constant temperature oven at 60 °C for in-situ polymerization for 8 h to obtain an NCM811 / / Gr full battery.

[0059] Example 2

[0060] Under anhydrous and anaerobic conditions, 0.02 mol of the polymerization monomer compound 2b, 0.02 mol of glycidyl acrylate, and 5.3 g of lithium bis(trifluoromethylsulfonyl)imide were mixed and added to a mixed solution of 3 mL of ethylene carbonate, 3 mL of dimethyl carbonate, 0.6 mL of acetonitrile, and 11.4 mL of 1,3,5-cyclohexanetricarbonitrile. After mixing evenly, a homogeneous solution was obtained; then 1,3-propanesultone (the addition amount is 1% of the mass of the homogeneous solution) was added to the homogeneous solution to obtain a precursor solution, and potassium persulfate (0.5% of the mass of the polymerization monomer) and pentamethyldiethylenetriamine (0.5% of the mass of the polymerization monomer) were added. After the solution was stirred evenly, the electrolyte was assembled into a LiNi 0.8 Co 0.1 Mn 0.1 / Gr battery and a steel sheet (SS) / steel sheet (SS) symmetric battery. The assembled battery was placed in a constant temperature oven at 60 °C for in-situ polymerization for 8 h to obtain an NCM811 / / Gr full battery.

[0061] Example 3

[0062] Under anhydrous and anaerobic conditions, 0.038 mol of compound 2c as the polymerization monomer, 0.002 mol of glycidyl acrylate, and 5.2 g of lithium hexafluorophosphate were mixed and added to a mixed solution of 3 mL of ethylene carbonate, 3 mL of dimethyl carbonate, 11.4 mL of trimethylacetonitrile, and 0.6 mL of glutarodinitrile to obtain a homogeneous solution; then 1,3-propane sultone (the addition amount was 1% of the mass of the homogeneous solution) was added to the homogeneous solution to obtain a precursor solution, and potassium persulfate (0.5% of the polymerization monomer) and pentamethyldiethylenetriamine (0.5% of the mass of the polymerization monomer) were added. After the solution was stirred evenly, the electrolyte was assembled into a LiNi 0.8 Co 0.1 Mn 0.1 / Gr battery and a steel sheet (SS) / steel sheet (SS) symmetric battery. The assembled battery was placed in a constant temperature oven at 60 °C for in-situ polymerization for 8 h to prepare an NCM811 / / Gr full battery.

[0063] Example 4

[0064] The difference from Example 1 was that the nitrile compound was 0.2 mL of isobutyronitrile and 11.8 mL of 2-methylpropanedinitrile.

[0065] Example 5

[0066] The difference from Example 1 was that the nitrile compound was 11.8 mL of isobutyronitrile and 0.2 mL of 2-methylpropanedinitrile.

[0067] Example 6

[0068] The difference from Example 1 was that the nitrile compound was only isobutyronitrile, and the total amount of the nitrile compound remained unchanged.

[0069] Example 7

[0070] The difference from Example 1 was that the nitrile compound was only 2-methylpropanedinitrile, and the total amount of the nitrile compound remained unchanged.

[0071] Example 8

[0072] The difference from Example 1 was that the nitrile compound 2-methylpropanedinitrile was not added.

[0073] Example 9

[0074] The difference from Example 1 was that the polymerization monomer was 0.016 mol of compound 2a and 0.024 mol of glycidyl acrylate.

[0075] Example 10

[0076] The difference from Example 1 is that the polymerization monomers are 0.039 mol of Compound 2a and 0.001 mol of glycidyl acrylate.

[0077] Example 11

[0078] The difference from Example 1 is that the polymerization monomer is only Compound 2a.

[0079] Example 12

[0080] The difference from Example 1 is that the polymerization monomer is only glycidyl acrylate.

[0081] Example 13

[0082] The difference from Example 1 is that an electrolyte is used to assemble a LiCoO₂ / / Gr battery, and the assembled battery is placed in an incubator at 60 °C for 8 h of polymerization to obtain a LiCoO₂ / / Gr full battery.

[0083] Example 14

[0084] The difference from Example 1 is that an electrolyte is used to assemble a LiNi 0.90 Co 0.05 Mn 0.05 O₂ / / SC650 battery, and the assembled battery is placed in an incubator at 60 °C for 8 h of polymerization to obtain a LiNi 0.90 Co 0.05 Mn 0.05 O₂ / / SC650 (silicon-carbon 650) full battery.

[0085] Example 15

[0086] The difference from Example 1 is that the preparation process of the secondary lithium battery is non-in-situ polymerization, and the specific steps are as follows: Pour the homogeneous solid electrolyte precursor solution onto a polyimide porous membrane and subject it to vacuum at 50 °C for 12 h to form a solid electrolyte membrane with a thickness of 15 μm. Cut the solid electrolyte membrane into corresponding sizes for the positive electrode (NCM811) and the negative electrode (graphite), and assemble an NCM811 / / Gr full battery and a steel sheet (SS) / steel sheet (SS) symmetric battery.

[0087] Comparative Example 1

[0088] The difference from Example 1 is that the polymerization monomer is acrylonitrile, and its total amount remains unchanged.

[0089] Comparative Example 2

[0090] The difference from Example 1 is that the polymerization monomer is methyl methacrylate, and its total amount remains unchanged.

[0091] Test Example:

[0092] 1. Ionic conductivity: The ionic conductivity of the batteries assembled in the above examples and comparative examples was tested using an electrochemical workstation. The test results are shown in Table 1. It can be seen from the results that the ionic conductivity of Example 1 is 8.2×10 -3 S / cm, which is better than most current solid electrolytes.

[0093] 2. The full batteries assembled in the above examples were subjected to rate performance testing on a charge-discharge tester. The voltage range was 3.0 - 4.2V, and the rate test range was 0.2C / 0.2C to 15C / 15C. The test results are as Figure 1 shown. Table 1 shows the discharge capacity at a rate of 8C / 8C. Combining Figure 1 with Table 1, it can be seen that the rate performance of Examples 1 - 3 is excellent.

[0094] 3. The batteries assembled in the above examples were subjected to fast charge and long cycle performance testing on a charge-discharge tester. The voltage range was 3.0 - 4.2V, and the rate was 8C / 8C. The test results are as Figure 2 shown. Combining Figure 2 with Table 1, it can be seen that Examples 1 - 3 have high ionic conductivity and excellent fast charge and long cycle performance. In Example 8, the nitrile compound 2-methylmalononitrile was not added, and in Examples 6 and 7, only one nitrile compound was added. Their fast charge and long cycle performance was improved compared to Example 8. The fast charge and long cycle performance of Examples 1 - 3 was further improved compared to Examples 6 and 7. Thus, it shows that in the electrolyte of the present application, using nitrile compounds as plasticizers and introducing nitrile polymers improves the fast charge and long cycle performance of the battery. When two nitrile compounds are added in a specific ratio, the fast charge and long cycle performance of the battery can be further improved. The capacity retention rates of Examples 9, 10, and 12 after 100 cycles were lower than those of Example 1 and Example 11. In particular, the capacity retention rate of Example 12 was the lowest, indicating that adding nitrile polymer monomers in combination with nitrile compounds and in-situ or non-in-situ polymerizing them into nitrile polymers can improve the fast charge and long cycle performance of the battery.

[0095] 4. The batteries assembled in the above examples were subjected to long cycle performance testing on a charge-discharge tester. The voltage range was 3.0 - 4.2V, and the rate was 1C / 1C. The test results are as Figure 2 shown. Combining Figure 2As can be seen from Table 1, the long cycle performance of Examples 1-3 is excellent. After 100 cycles, the capacity retention rates of Examples 4-8 are significantly lower than that of Example 1. Especially for Example 8, it can be seen that adding a specific nitrile compound to the polymer as a plasticizer helps to improve its slow charge long cycle performance. After 100 cycles, the capacity retention rates of Examples 9, 10, and 12 are lower than those of Example 1 and Example 11. Especially, the capacity retention rate of Example 12 is the lowest, indicating that adding a nitrile polymerization monomer and in-situ or non-in-situ polymerizing it into a nitrile polymer can improve the slow charge long cycle performance of the battery.

[0096] Table 1

[0097]

[0098] In the embodiments of the present application, only several of the polymerization monomers are exemplified. It can be understood that as long as all the polymerization monomers satisfy their structural general formulas, the technical effects of the present application can be achieved. However, since there are many polymerization monomers that satisfy the shown structure, the present application will not list them one by one. Those skilled in the art can infer that the polymerization monomers of the above structure can all achieve the above functions and thus achieve the above effects on the basis of clarifying the technical concept of the present application. In addition, only one or several of other polymerization monomers, other plasticizers, and functional additives are exemplified in the implementation, which does not constitute a limitation to the present application. It can be understood that replacing them with any one or several defined in the present application can all prepare a nitrile fast charge polymer electrolyte and thus achieve the technical effects of the present application. However, since there are many types to choose from, the present application will not list them one by one either. Although only several of them are exemplified in the above embodiments, it does not constitute a limitation to the present application.

[0099] The above description of the embodiments is to enable those of ordinary skill in the art to understand and use the invention. Obviously, those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A nitrile-based fast-charging polymer electrolyte, characterized in that, Comprising an electrolyte matrix and a lithium salt; wherein, the electrolyte matrix comprises raw materials in the following parts by weight: (a) 1 to 60 parts of a polymerizable monomer, and the polymerizable monomer is selected from at least one of the compounds shown by the structural formula as formula (I): In formula (I), X is N or O; when X is N, R1, R2, and R3 are independently selected from a hydrogen atom, a halogen, a cyano group, or an alkyl group, an alkoxy group, a fluoroalkyl group having 1 to 8 carbon atoms; when X is O, there is no R1, and R2 and R3 are independently selected from a hydrogen atom, a halogen, a cyano group, or an alkyl group, an alkoxy group, a fluoroalkyl group having 1 to 8 carbon atoms; (b) 1 to 30 parts of a nitrile compound, and the nitrile compound is selected from at least one of the compounds shown by the structural formula as formula (II): In formula (II), n = 0 to 4, and R1, R2, and R3 are independently selected from a hydrogen atom, a cyano group, or an alkyl group having 1 to 8 carbon atoms; (c) 0.1 to 5 parts of a functional additive; (d) 0.1 to 20 parts of other plasticizers.

2. The nitrile-based fast-charging polymer electrolyte according to claim 1, wherein The nitrile compound is a compound A and a compound B with a volume ratio of (0.5:9.5) to (9.5:0.5), and both the compound A and the compound B are selected from the compounds shown by the structural formula as formula (II); wherein, The compound A is selected from at least one of acetonitrile, propionitrile, isobutyronitrile, trimethylacetonitrile, butyronitrile, and succinonitrile; The compound B is selected from at least one of valeronitrile, glutarodinitrile, adiponitrile, 2-methylmalononitrile, 1,3,5-cyclohexanetricarbonitrile, and 1,3,6-hexanetricarbonitrile.

3. The nitrile-based fast-charging polymer electrolyte according to claim 1, characterized in that, The polymerizable monomer is selected from any one of the following compounds:

4. The nitrile-based fast-charging polymer electrolyte according to claim 1, wherein The polymerizable monomer further comprises other polymerizable monomers; the other polymerizable monomers are selected from carbonates, carboxylates, fluorinated carbonates, fluorinated carboxylates, sulfonates, phosphates, sulfates, ethers, fluoroethers, and imides containing carbon-carbon double bonds or epoxy structures.

5. The nitrile-based fast-charging polymer electrolyte according to claim 4, wherein, The polymerizable monomer comprises the compound shown by formula (I) and other polymerizable monomers in a molar ratio of (5 to 9.5):(0.5 to 5).

6. The nitrile-based fast-charging polymer electrolyte according to claim 1, characterized in that, The functional additive is selected from any one or a combination of lithium organic phosphates, lithium sulfonimides, lithium organic borates, carbonates, phosphates, and inorganic lithium compounds.

7. The nitrile-based fast-charging polymer electrolyte according to claim 1, wherein The other plasticizers are selected from any one or a combination of carbonates, γ-butyrolactone, sulfolane, and organic acid esters having 1 to 4 carbon atoms.

8. The nitrile-based fast-charging polymer electrolyte according to claim 1, wherein It further comprises an initiator and a catalyst.

9. A secondary lithium battery, characterized in that, Comprising the nitrile-based fast-charging polymer electrolyte according to any one of claims 1-8, and further comprising a positive electrode and a negative electrode.

10. The method for preparing a secondary lithium battery according to claim 9, wherein Including the following steps: (1) Mix and stir evenly the polymerizable monomer, the nitrile compound, the lithium salt, the functional additive, and the other plasticizers to prepare a uniform solid polymer precursor solution; (2) Add the precursor solution to the initiator and the catalyst and mix evenly, and inject it into a lithium-ion battery containing a positive electrode and a negative electrode; then place the battery in an incubator for in-situ polymerization to prepare a solid electrolyte; or scrape the precursor solution onto a porous support material, and then place it in an incubator for non-in-situ polymerization to prepare a solid electrolyte membrane.

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