Electrolyte precursor solution, electrolyte, preparation method and application thereof

Abstract

The present invention relates to the field of battery technology, and in particular, to an electrolyte precursor solution, an electrolyte, and a preparation method and application thereof. An electrolyte precursor solution comprises a polycyclic ether monomer, a fluorine-containing polycyclic ether monomer, a plasticizer, an initiator, and a lithium salt; the fluorine-containing polycyclic ether monomer is a fluorine-containing five-membered cyclic ether monomer and / or a fluorine-containing six-membered cyclic ether monomer. The electrolyte precursor solution of the present invention can form an electrolyte precursor solution with excellent performance through the coordination of various raw material components, so that the finally obtained polymer electrolyte has both high ionic conductivity and high oxidation potential. The polymer electrolyte of the present invention is formed by in-situ polymerization, can form good interface contact, and effectively reduce interface impedance.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to an electrolyte precursor solution, an electrolyte, and a preparation method and application thereof. Background Art

[0002] Lithium metal anode has the lowest reduction potential (-3.04V vs. standard hydrogen electrode) and extremely high theoretical specific capacity (3860mAh / g), and is considered one of the best choices for the next generation of high-energy-density batteries. The high reactivity of lithium metal anode leads to a large consumption of liquid electrolyte, uncontrollable growth of lithium dendrites, low Coulomb efficiency, and the potential safety hazard of internal short circuit in the battery, which seriously hinders the commercial application of lithium metal batteries.

[0003] In view of the above problems, replacing liquid electrolytes with solid electrolytes is considered to be an effective way to solve the safety of lithium metal batteries. Among different types of solid electrolytes, polymer electrolytes are one of the most promising solid electrolytes due to their high flexibility and excellent processing properties. However, due to their low ionic conductivity and electrochemical instability when paired with Li metal anodes and high-voltage cathodes, polymer electrolytes have not been practically utilized. In order to improve the performance of lithium metal batteries, it is crucial to prepare solid polymer electrolytes with high ionic conductivity, excellent interfacial stability and a wide electrochemical window. In order to improve the ionic conductivity of solid polymer electrolytes, a large number of research works reported in the literature include adding inorganic fillers and cross-linking polymers, etc., but most of the research focuses on improving the ionic conductivity of polymer electrolytes, and less attention is paid to the interfacial stability of solid polymer electrolytes with lithium metal anodes and high-voltage cathodes.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] An object of the present invention is to provide an electrolyte precursor solution, which can obtain an electrolyte having both high conductivity and high oxidation potential.

[0006] Another object of the present invention is to provide an electrolyte comprising an ether segment and a fluoroether segment, and having high electrical conductivity and oxidation potential.

[0007] Another object of the present invention is to provide a method for preparing the electrolyte.

[0008] Another object of the present invention is to provide a battery.

[0009] Another object of the present invention is to provide an electrical device.

[0010] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0011] An electrolyte precursor solution comprises a polycyclic ether monomer, a fluorine-containing polycyclic ether monomer, a plasticizer, an initiator and a lithium salt. The fluorine-containing polycyclic ether monomer is a fluorine-containing five-membered cyclic ether monomer and / or a fluorine-containing six-membered cyclic ether monomer.

[0012] In some embodiments, the volume ratio of the polycyclic ether monomer, the fluorine-containing polycyclic ether monomer and the plasticizer is (2-6):(3-7):1.

[0013] In some embodiments, the total usage ratio of the initiator to the polycyclic ether monomer and the fluorine-containing polycyclic ether monomer is (0.2-0.8) g: 100 mL.

[0014] In some embodiments, the concentration of the lithium salt in the electrolyte precursor solution is 0.8-2 mol / L.

[0015] In some embodiments, the polycyclic ether monomer is selected from 1,3-dioxolane and / or 1,3-dioxane.

[0016] In some embodiments, the fluorinated polycyclic ether monomer is selected from at least one of compounds (I) to (IX):

[0017] (I) (Ⅱ) (III) (IV) (V) (VI) (VII) (VIII) (IX).

[0018] In some embodiments, the plasticizer is selected from at least one of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, succinonitrile and ethylene glycol bis(propionitrile) ether.

[0019] In some embodiments, the lithium salt is selected from at least one of lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium difluorooxalatoborate and lithium nitrate.

[0020] In some embodiments, the initiator is selected from one or more of benzoyl peroxide, potassium persulfate, ammonium persulfate, azobisisobutyronitrile or azobisisoheptanenitrile.

[0021] In some embodiments, the method for preparing the electrolyte precursor solution includes: mixing a polycyclic ether monomer, a fluorine-containing polycyclic ether monomer, a plasticizer, an initiator, and a lithium salt.

[0022] An electrolyte is obtained by heat treating the electrolyte precursor solution; the electrolyte comprises a fluorine-containing ether polymer, a plasticizer and a lithium salt, and the fluorine-containing ether polymer is formed by in-situ polymerization of a polycyclic ether monomer and a fluorine-containing polycyclic ether monomer.

[0023] The method for preparing the electrolyte as described above comprises the following steps:

[0024] The polycyclic ether monomer, the fluorine-containing polycyclic ether monomer, the plasticizer, the initiator and the lithium salt are mixed to obtain an electrolyte precursor solution; and the electrolyte precursor solution is heat-treated to obtain an electrolyte.

[0025] In some embodiments, the mixing process specifically includes: first mixing the polycyclic ether monomer, the fluorine-containing polycyclic ether monomer and the plasticizer, and then second mixing with the initiator and the lithium salt.

[0026] In some embodiments, the heat treatment temperature is 40-70° C., and the heat treatment time is 12-48 hours.

[0027] In some implementations, the electrolyte precursor solution is injected into the battery cell before the heat treatment is performed.

[0028] A battery comprises the electrolyte or the electrolyte prepared by the electrolyte preparation method.

[0029] An electrical device comprises the battery.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The electrolyte precursor solution of the present invention can form an electrolyte precursor solution with excellent performance through the coordinated combination of various raw material components, so that the finally obtained polymer electrolyte can have both high ionic conductivity and high oxidation potential.

[0032] (2) The polymer electrolyte of the present invention comprises an ether segment and a fluoroether segment, wherein the ether segment and Li + The coordination effect is strong and has a similar solvent effect, while the fluoroether and Li + The coordination effect is weak and has a similar diluent effect. The advantages of this structure include: 1) Based on the weak solvation ability of fluoroether, it divides the electrolyte into multiple grid structures to form a locally aggregated solvation structure. The change in the solvation structure reduces the LUMO energy level of the lithium salt anion. At the same time, Li +It tends to carry more anions to the negative electrode surface, so the lithium salt anions are preferentially reduced on the lithium metal surface, forming an SEI film dominated by anion decomposition, which has a protective effect on the lithium metal negative electrode; the ether-containing chain segment is used as a solvent component, and most of the lone pairs of electrons are given to participate in coordination, and the uncoordinated ether structure is reduced, thereby improving the oxidation stability of the electrolyte. 2) The ether-containing chain segment has a strong coordination ability with lithium ions, and the fluorinated ether has a strong coordination ability with Li + The coordination effect is weak, and strong coordination sites and weak coordination sites alternate, which is conducive to the conduction of lithium ions along the polymer chain. At the same time, with the assistance of the plasticizer, a continuous and fast lithium ion conduction channel can be formed to enhance the ionic conductivity of the polymer electrolyte. 3) The polycyclic ether monomers used in the present invention are five-membered rings and six-membered rings. Compared with the three-membered ring ethylene oxide, the number of methylene groups between adjacent oxygen elements after polymerization is more, and it has higher oxidation stability. The polymer electrolyte provided by the present invention is formed by in-situ polymerization. Through the coordinated cooperation of various components, the electrolyte has high ionic conductivity and high electrochemical stability window, and also has good compatibility with the lithium metal negative electrode, effectively reducing the interfacial impedance and improving the cycle performance.

[0033] (3) The electrolyte preparation method of the present invention is simple, easy, environmentally friendly, and can obtain a polymer electrolyte with high ionic conductivity and high oxidation potential.

[0034] (4) The battery of the present invention has excellent cycle performance and safety performance. DETAILED DESCRIPTION

[0035] The embodiments of the present invention will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conditions are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0036] According to one aspect of the present invention, the present invention relates to an electrolyte precursor solution, comprising a polycyclic ether monomer, a fluorine-containing polycyclic ether monomer, a plasticizer, an initiator and a lithium salt, wherein the fluorine-containing polycyclic ether monomer is a fluorine-containing five-membered cyclic ether monomer and / or a fluorine-containing six-membered cyclic ether monomer.

[0037] The electrolyte precursor solution of the present invention can form an electrolyte precursor solution with excellent performance through the coordination of various raw material components, and can make the finally obtained polymer electrolyte have high ion conductivity and oxidation potential.

[0038] In some embodiments, the volume ratio of the polycyclic ether monomer, the fluorinated polycyclic ether monomer and the plasticizer is (2-6): (3-7): 1, such as 2:3:1, 2:4:1, 3:4:1, 4:5:1, 5:6:1, etc. Preferably, the volume ratio of the polycyclic ether monomer, the fluorinated polycyclic ether monomer and the plasticizer is (3-4): (5-6): 1. The polycyclic ether monomer, the fluorinated polycyclic ether monomer and the plasticizer of the present invention adopt a suitable volume ratio, which is more conducive to ensuring that the subsequently obtained polymer electrolyte has both high ionic conductivity and high oxidation potential.

[0039] In some embodiments, the total amount ratio of the initiator to the polycyclic ether monomer and the fluorine-containing polycyclic ether monomer is (0.2-0.8) g: 100 mL, such as 0.2 g: 100 mL, 0.3 g: 100 mL, 0.4 g: 100 mL, 0.5 g: 100 mL, 0.6 g: 100 mL, 0.7 g: 100 mL or 0.8 g: 100 mL, etc. Preferably, the mass of the initiator is (0.4-0.6) g: 100 mL of the total mass of the polycyclic ether monomer and the fluorine-containing polycyclic ether monomer. The present invention uses an appropriate amount of initiator, which is more conducive to the in-situ polymerization of the polycyclic ether monomer and the fluorine-containing polycyclic ether monomer, and ensures the performance of the final polymer electrolyte.

[0040] In some embodiments, the concentration of the lithium salt in the electrolyte precursor solution is 0.8-2 mol / L, such as 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.2 mol / L, 0.151.4 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, etc. Preferably, the concentration of the lithium salt in the electrolyte precursor solution is 0.9-1.5 mol / L.

[0041] In some embodiments, the polycyclic ether monomer is selected from 1,3-dioxolane and / or 1,3-dioxane.

[0042] In some embodiments, the fluorinated polycyclic ether monomer is selected from at least one of compounds (I) to (IX):

[0043] Compound (I), CAS: 76492-96-1: ; Compound (II), CAS: 62999-58-0: ; Compound (III), CAS: 60010-41-5: , Compound (IV), CAS: 21297-65-4: 、Compound (V), CAS: 50607-96-0: 、Compound (VI), CAS: 64499-65-6 、Compound (VII), CAS: 675-22-9 、Compound (VIII), CAS: 35878-04-7: 、Compound (IX), CAS: 36301-44-7: .

[0044] In some embodiments, the plasticizer is selected from at least one of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, succinonitrile and ethylene glycol bis (propionitrile) ether. The plasticizer of the present invention can be any one of the above, or a variety of combinations, such as a combination of ethylene glycol dimethyl ether and ethylene glycol diethyl ether, a combination of succinonitrile and ethylene glycol bis (propionitrile) ether, etc.

[0045] In some embodiments, the lithium salt is selected from lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium difluorooxalatoborate (LiDFOB) and lithium nitrate (LiNO 3 In some embodiments, the lithium salt may be selected from lithium bis(fluorosulfonyl)imide) and lithium hexafluorophosphate, lithium tetrafluoroborate and lithium difluorooxalatoborate, lithium difluorooxalatoborate and lithium nitrate, etc.

[0046] In some embodiments, the initiator is selected from one or more of benzoyl peroxide, potassium persulfate, ammonium persulfate, azobisisobutyronitrile or azobisisoheptanitrile. In some embodiments, the initiator is selected from benzoyl peroxide and potassium persulfate, or potassium persulfate and ammonium persulfate, or azobisisobutyronitrile and azobisisoheptanitrile, etc.

[0047] In some embodiments, the preparation method of the electrolyte precursor solution includes: mixing the polycyclic ether monomer, the fluorinated polycyclic ether monomer, the plasticizer, the initiator and the lithium salt. In some embodiments, the mixing process specifically includes: mixing the polycyclic ether monomer, the fluorinated polycyclic ether monomer and the plasticizer, and then mixing with the initiator and the lithium salt.

[0048] According to another aspect of the present invention, the present invention also relates to an electrolyte obtained by heat treating the above-mentioned electrolyte precursor solution; the electrolyte includes a fluorine-containing ether polymer, a plasticizer and a lithium salt, and the fluorine-containing ether polymer is formed by in-situ polymerization of a polycyclic ether monomer and a fluorine-containing polycyclic ether monomer.

[0049] The polymer electrolyte of the present invention comprises an ether segment and a fluoroether segment, wherein the ether segment and Li + The coordination effect is strong and has a similar solvent effect, while the fluoroether and Li +The coordination effect is weak and has a similar diluent effect. The advantages of this composition structure include: 1) Based on the weak solvation ability of fluoroether, it divides the electrolyte into multiple grid structures to form a locally aggregated solvation structure. Compared with conventional electrolytes, the solvation structure of the polymer electrolyte provided by the present invention has many advantages. On the one hand, due to the reduction in the number of solvent components, a large amount of lithium salt cannot be completely dissociated, which prompts more lithium salt anions to participate in the solvation structure. The change in the solvation structure reduces the LUMO energy level of the lithium salt anions, and at the same time, Li + It tends to carry more anions to the negative electrode surface, so the lithium salt anions are preferentially reduced on the lithium metal surface, forming an SEI film dominated by anion decomposition, which has a protective effect on the lithium metal negative electrode. On the other hand, as a solvent component, most of the lone pairs of electrons in the ether-containing chain segment are given to participate in coordination, and the uncoordinated ether structure is reduced, thereby improving the oxidation stability of the electrolyte. 2) The ether-containing chain segment has a strong coordination ability with lithium ions, while the fluorinated ether has a strong coordination ability with Li + The coordination effect is weak, and strong coordination sites and weak coordination sites alternate, which is conducive to the conduction of lithium ions along the polymer chain. At the same time, with the assistance of the plasticizer, a continuous and fast lithium ion conduction channel can be formed to enhance the ionic conductivity of the polymer electrolyte. 3) The polycyclic ether monomer used in the present invention is a five-membered ring and / or a six-membered ring. Compared with the three-membered ring ethylene oxide, the number of methylenes between adjacent oxygen elements after polymerization is more, and it has higher oxidation stability. The polymer electrolyte provided by the present invention is formed by in-situ polymerization, which can form a good interface contact and effectively reduce the interface impedance.

[0050] A method for preparing an electrolyte comprises the following steps:

[0051] The polycyclic ether monomer, the fluorine-containing polycyclic ether monomer, the plasticizer, the initiator and the lithium salt are mixed to obtain an electrolyte precursor solution; and the electrolyte precursor solution is heat-treated to obtain an electrolyte.

[0052] The electrolyte preparation method of the invention is simple and easy to implement, is environmentally friendly, and can obtain a polymer electrolyte with high ionic conductivity and high oxidation potential.

[0053] In some embodiments, the mixing process specifically includes: first mixing the polycyclic ether monomer, the fluorine-containing polycyclic ether monomer and the plasticizer, and after mixing them evenly, second mixing them with the initiator and the lithium salt to make the materials more fully mixed.

[0054] In some embodiments, the heat treatment temperature is 40-70°C, such as 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, etc., or any range between the two. The heat treatment time is 12-48h, such as 12h, 13h, 15h, 16h, 18h, 20h, 25h, 30h, 35h, 430h, 45h or 48h, etc., or any range between the two. The present invention adopts a suitable heat treatment temperature and time to ensure the electrochemical properties of the obtained polymer electrolyte.

[0055] In some embodiments, the electrolyte precursor solution is subjected to the above-mentioned heat treatment during the preparation of the battery, that is, the heat treatment is performed after the solution is injected.

[0056] According to another aspect of the present invention, the present invention also relates to a battery, comprising the above-mentioned electrolyte or the electrolyte prepared by the above-mentioned method for preparing the electrolyte.

[0057] The battery of the present invention has high capacity retention rate, good cycle performance and good safety performance.

[0058] In some embodiments, the battery includes a lithium metal battery, and the lithium metal battery includes a positive electrode sheet, a negative electrode sheet, a separator, and the above-mentioned electrolyte.

[0059] According to another aspect of the present invention, the present invention also relates to an electric device, comprising the above-mentioned battery. The electric device includes a portable device, an electric car, and the like.

[0060] The following is further explained in conjunction with specific embodiments and comparative examples.

[0061] Example 1

[0062] A method for preparing a polymer electrolyte precursor solution comprises the following steps:

[0063] Weigh 40 mL of 1,3-dioxolane, 50 mL of compound (I) and 10 mL of ethylene glycol dimethyl ether and mix them evenly. Then add 0.5 g of azobisisobutyronitrile and 0.12 mol of LiFSI and stir until they are completely dissolved to obtain a polymer electrolyte precursor solution.

[0064] The method for preparing the battery in this embodiment comprises the following steps:

[0065] (1) Preparation of negative electrode sheet: The lithium-copper composite strip with a lithium layer thickness of 20 μm was cut into a size of (60 mm × 100 mm) for later use.

[0066] (2) Preparation of positive electrode sheet: LiNi 0.8 Co 0.1 Mn 0.1 O2 , conductive carbon black (SuperP), polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 96:2:2, and an appropriate amount of N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 75%, and stirred evenly. The slurry is evenly coated on the positive electrode current collector aluminum foil, dried at 90°C to obtain a positive electrode sheet, and the positive electrode sheet is cut into (60mm×100mm) specifications for standby use.

[0067] (3) Preparation of lithium metal battery: A polyethylene (PE) diaphragm with a thickness of 12 μm was selected, and a Z-shaped lamination method was adopted. The positive electrode sheet and the negative electrode sheet were respectively formed on both sides of the diaphragm, and the diaphragm was formed between the electrode sheets. After the lamination was completed, the tabs were welded, and then placed in an aluminum-plastic film, top and side sealed, the polymer precursor solution prepared in this embodiment was injected, encapsulated, soaked at room temperature, and heated and cured at a temperature of 55°C for 24 hours, and finally a lithium metal soft-pack battery was obtained.

[0068] Example 2

[0069] A method for preparing a polymer electrolyte precursor solution comprises the following steps:

[0070] Weigh 20 mL of 1,3-dioxolane, 70 mL of compound (I) and 10 mL of ethylene glycol dimethyl ether and mix them evenly. Then add 0.5 g of azobisisobutyronitrile and 0.12 mol of LiFSI and stir until they are completely dissolved to obtain a polymer electrolyte precursor solution.

[0071] The preparation method of the battery in this embodiment is the same as that in Example 1 except that the polymer electrolyte precursor solution mentioned above is used in this embodiment.

[0072] Example 3

[0073] A method for preparing a polymer electrolyte precursor solution comprises the following steps:

[0074] Weigh 60 mL of 1,3-dioxolane, 30 mL of compound (I) and 10 mL of ethylene glycol dimethyl ether and mix them evenly. Then add 0.5 g of azobisisobutyronitrile and 0.12 mol of LiFSI and stir until they are completely dissolved to obtain a polymer electrolyte precursor solution.

[0075] The preparation method of the battery in this embodiment is the same as that in Example 1 except that the polymer electrolyte precursor solution mentioned above is used in this embodiment.

[0076] Example 4

[0077] A method for preparing a polymer electrolyte precursor solution comprises the following steps:

[0078] Weigh 40 mL of 1,3-dioxolane, 50 mL of compound (IV) and 10 mL of ethylene glycol dimethyl ether and mix them evenly. Then add 0.5 g of azobisisobutyronitrile and 0.12 mol of LiFSI and stir until they are completely dissolved to obtain a polymer electrolyte precursor solution.

[0079] The preparation method of the battery in this embodiment is the same as that in Example 1 except that the polymer electrolyte precursor solution mentioned above is used in this embodiment.

[0080] Example 5

[0081] A method for preparing a polymer electrolyte precursor solution comprises the following steps:

[0082] 40 mL of 1,3-dioxane, 50 mL of compound (IX) and 10 mL of ethylene glycol dimethyl ether were weighed and mixed evenly, and then 0.5 g of azobisisobutyronitrile and 0.12 mol of LiFSI were added and stirred until they were completely dissolved to obtain a polymer electrolyte precursor solution.

[0083] The preparation method of the battery in this embodiment is the same as that in Example 1 except that the polymer electrolyte precursor solution mentioned above is used in this embodiment.

[0084] Example 6

[0085] A method for preparing a polymer electrolyte precursor solution comprises the following steps:

[0086] Weigh 40 mL of 1,3-dioxolane, 50 mL of compound (I) and 10 mL of ethylene glycol dimethyl ether and mix them evenly. Then add 0.5 g of azobisisobutyronitrile and 0.20 mol of LiFSI and stir until they are completely dissolved to obtain a polymer electrolyte precursor solution.

[0087] The preparation method of the battery in this embodiment is the same as that in Example 1 except that the polymer electrolyte precursor solution mentioned above is used in this embodiment.

[0088] Example 7

[0089] A method for preparing a polymer electrolyte precursor solution comprises the following steps:

[0090] Weigh 40 mL of 1,3-dioxolane, 50 mL of compound (I) and 10 mL of ethylene glycol dimethyl ether and mix them evenly. Then add 0.5 g of azobisisobutyronitrile and 0.08 mol of LiFSI and stir until they are completely dissolved to obtain a polymer electrolyte precursor solution.

[0091] The preparation method of the battery in this embodiment is the same as that in Example 1 except that the polymer electrolyte precursor solution mentioned above is used in this embodiment.

[0092] Example 8

[0093] A method for preparing a polymer electrolyte precursor solution comprises the following steps:

[0094] Weigh 40 mL of 1,3-dioxolane, 50 mL of compound (I) and 10 mL of ethylene glycol dimethyl ether and mix them evenly. Then add 0.5 g of azobisisobutyronitrile, 0.08 mol of LiFSI and 0.04 mol of LiPF6 and stir until they are completely dissolved to obtain a polymer electrolyte precursor solution.

[0095] The preparation method of the battery in this embodiment is the same as that in Example 1 except that the polymer electrolyte precursor solution mentioned above is used in this embodiment.

[0096] Comparative Example 1

[0097] A method for preparing a polymer electrolyte precursor solution comprises the following steps:

[0098] 90 mL of 1,3-dioxolane and 10 mL of ethylene glycol dimethyl ether were weighed and mixed evenly, and 0.5 g of azobisisobutyronitrile and 0.12 mol of LiFSI were added and stirred until they were completely dissolved to obtain a polymer electrolyte precursor solution.

[0099] The preparation method of the battery in this comparative example is the same as that in Example 1 except that the polymer electrolyte precursor solution mentioned above in this example is used.

[0100] Comparative Example 2

[0101] A method for preparing a polymer electrolyte precursor solution comprises the following steps:

[0102] 90 mL of compound (I) and 10 mL of ethylene glycol dimethyl ether were weighed and mixed evenly, and 0.5 g of azobisisobutyronitrile and 0.12 mol of LiFSI were added and stirred until completely dissolved to obtain a polymer electrolyte precursor solution.

[0103] The preparation method of the battery in this comparative example is the same as that in Example 1 except that the polymer electrolyte precursor solution mentioned above in this example is used.

[0104] Comparative Example 3

[0105] A method for preparing a polymer electrolyte precursor solution comprises the following steps:

[0106] Weigh 40 mL of propylene oxide, 50 mL of hexafluoropropylene oxide and 10 mL of ethylene glycol dimethyl ether and mix them evenly, then add 0.5 g of azobisisobutyronitrile and 0.12 mol of LiFSI and stir until they are completely dissolved to obtain a polymer electrolyte precursor solution.

[0107] The preparation method of the battery in this comparative example is the same as that in Example 1 except that the polymer electrolyte precursor solution mentioned above in this example is used.

[0108] Experimental example

[0109] 1. Determination of ionic conductivity

[0110] A 12 μm thick PE diaphragm was cut into 19 mm diameter discs, which were placed between two stainless steel sheets (16 mm diameter), and the polymer electrolyte precursor solutions prepared in the embodiments and comparative examples were dripped onto the diaphragms. After soaking at room temperature for 12 h, the diaphragms were cured at 55 °C for 24 h. The resistance at different temperatures was tested by AC impedance using an electrochemical workstation, and then the proton conductivity of the membrane at different temperatures was calculated by formula (1): σ = t / R × S, where σ is the ion conductivity (S / cm), t is the thickness of the ion exchange membrane (cm), R is the in-plane resistance perpendicular to the membrane surface (Ω), and S is the effective membrane area (cm 2 ).

[0111] 2. Determination of oxidation potential

[0112] A 12 μm thick PE diaphragm was cut into 19 mm diameter discs, which were placed between a metal lithium sheet (16 mm in diameter) and a carbon-coated aluminum foil sheet (16 mm in diameter), and the polymer electrolyte precursor solutions prepared in the embodiments and comparative examples were respectively dripped onto the diaphragms. After soaking at room temperature for 12 h, the diaphragms were cured at 55 ° C for 24 h. The voltage was scanned by cyclic voltammetry using an electrochemical workstation, first from the open circuit voltage to 6 V, with a scan rate of 0.1 mV / s.

[0113] 3. Cycle performance test

[0114] The lithium metal battery cycle test prepared in each embodiment and comparative example was carried out on the Xinwei test system. The battery adopted constant current-constant potential charge / constant current discharge (CC-CV / DC) mode. The charge and discharge cut-off voltages were 4.2V and 2.8V, respectively. The cut-off current of the constant potential was 0.05C. The charge and discharge were allowed to stand for 5 minutes between each cycle. The battery was cycled at a charge and discharge rate of 0.2 / 1C at 25°C.

[0115] The performance test results of the polymer electrolytes of various embodiments and comparative examples are shown in Table 1.

[0116] The performance test results of the lithium metal batteries of various embodiments and comparative examples are shown in Table 2.

[0117] Table 1 Performance test results of polymer electrolyte

[0118]

[0119] Table 2 Performance test results of lithium metal batteries

[0120]

[0121] As can be seen from Table 1, the polymer electrolyte provided by the present invention has both high ionic conductivity and oxidation potential. As can be seen from Table 2, the battery prepared by using the polymer electrolyte provided by the present invention can form a stable interface with both the lithium metal negative electrode and the high-voltage positive electrode, slowing down the redox consumption of the electrolyte, thereby obtaining a longer cycle life.

[0122] By comparing Example 1 with Comparative Example 1, it can be seen that since Comparative Example 1 only uses a single polycyclic ether monomer, the formed polymer electrolyte has good ion conductivity but insufficient oxidation resistance, showing a poor cycle life.

[0123] By comparing Example 1 and Comparative Example 2, it can be seen that since Comparative Example 2 only uses a single fluorinated polycyclic ether monomer, the formed polymer electrolyte has strong antioxidant properties, but low ionic conductivity and also exhibits a poor cycle life.

[0124] By comparing Example 1 and Comparative Example 3, it can be seen that due to the three-membered cyclic ether monomer used in Comparative Example 3, the formed polymer electrolyte has poor oxidation resistance and exhibits poor cycle life.

[0125] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolyte, characterized in that Obtained by heat treatment of an electrolyte precursor solution; The electrolyte precursor solution comprises a polycyclic ether monomer, a fluorine-containing polycyclic ether monomer, a plasticizer, an initiator and a lithium salt, wherein the fluorine-containing polycyclic ether monomer is a fluorine-containing five-membered cyclic ether monomer and / or a fluorine-containing six-membered cyclic ether monomer; and the polycyclic ether monomer is selected from 1,3-dioxolane and / or 1,3-dioxane; The electrolyte comprises a fluorine-containing ether polymer, a plasticizer and a lithium salt. The fluorine-containing ether polymer is formed by in-situ polymerization of a polycyclic ether monomer and a fluorine-containing polycyclic ether monomer.

2. The electrolyte according to claim 1, characterized in that Contains at least one of the following features (1) to (3): (1) The volume ratio of the polycyclic ether monomer, the fluorinated polycyclic ether monomer and the plasticizer is (2-6):(3-7):1; (2) The total amount ratio of the initiator to the polycyclic ether monomer and the fluorinated polycyclic ether monomer is (0.2-0.8) g: 100 mL; (3) The concentration of the lithium salt in the electrolyte precursor solution is 0.8~2 mol / L.

3. The electrolyte according to claim 1, characterized in that Contains at least one of the following features (1) to (4): (1) The fluorinated polycyclic ether monomer is at least one selected from compounds (I) to (IX): （Ⅰ）、 （Ⅱ）、 （Ⅲ）、 （Ⅳ）、 （Ⅴ）、 （Ⅵ）、 （Ⅶ）、 （Ⅷ）、 （Ⅸ）； (2) The plasticizer is at least one selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, succinonitrile and ethylene glycol bis(propionitrile) ether; (3) The lithium salt is at least one selected from lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium difluorooxalatoborate and lithium nitrate; (4) The initiator is selected from one or more of benzoyl peroxide, potassium persulfate, ammonium persulfate, azobisisobutyronitrile or azobisisoheptylnitrile.

4. The electrolyte according to claim 1, characterized in that The method for preparing the electrolyte precursor solution comprises: mixing a polycyclic ether monomer, a fluorine-containing polycyclic ether monomer, a plasticizer, an initiator and a lithium salt.

5. The method for preparing an electrolyte according to any one of claims 1 to 4, characterized in that: The following steps are involved: The polycyclic ether monomer, the fluorine-containing polycyclic ether monomer, the plasticizer, the initiator and the lithium salt are mixed to obtain an electrolyte precursor solution; and the electrolyte precursor solution is heat-treated to obtain an electrolyte.

6. The method for preparing the electrolyte according to claim 5, characterized in that: The mixing process specifically includes: first mixing the polycyclic ether monomer, the fluorine-containing polycyclic ether monomer and the plasticizer, and then second mixing them with the initiator and the lithium salt.

7. The method for preparing the electrolyte according to claim 5, characterized in that: The heat treatment temperature is 40-70°C and the heat treatment time is 12-48h; And / or, injecting the electrolyte precursor solution into the battery cell, and then performing the heat treatment.

8. A battery, characterized in that: An electrolyte comprising the electrolyte described in any one of claims 1 to 4 or an electrolyte prepared by the method for preparing the electrolyte described in any one of claims 5 to 7.

9. An electrical device, characterized in that: A battery comprising the battery of claim 8.

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