Semi-solid electrolyte, lithium-ion battery containing the same, and preparation method

Abstract

The present invention relates to a semi-solid electrolyte and a lithium-ion battery containing the same, and a preparation method thereof. In order to solve the problem in the prior art that sulfur-containing additives (such as vinyl sulfate) commonly used in semi-solid electrolytes will produce strong side reactions during long-term thermal curing, resulting in deterioration of performance. The present invention provides a semi-solid electrolyte, including a polymer monomer, an initiator, an organic solvent, a lithium salt and an additive, wherein the additive includes one or more compounds shown in formula (I): wherein R1, R2, R3, R4, and R5 are independently selected from one of hydrogen, fluorine, alkyl, fluoroalkyl, alkoxy, and fluoroalkoxy. The lithium-ion battery using the semi-solid electrolyte of the present invention has good chemical stability and takes into account both room temperature and high temperature cycle performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium batteries, and in particular relates to a semi-solid electrolyte, a lithium ion battery containing the semi-solid electrolyte, and a preparation method thereof. Background Art

[0002] In-situ curing technology chemically converts liquid electrolytes into semi-solid electrolytes within the battery. This semi-solid electrolyte can effectively reduce interfacial impedance, improve battery safety, and increase battery energy density, while remaining fully compatible with existing battery production equipment. Thermal curing is a simple and effective method for preparing semi-solid electrolytes within in-situ curing technology. However, prolonged exposure to high temperatures can accelerate the decomposition of vinyl sulfate, deteriorating battery performance.

[0003] Vinyl sulfate is a commonly used anode film-forming additive in liquid electrolytes, effectively improving battery high-temperature storage and high-temperature cycling performance. However, the substance itself is unstable and decomposes at high temperatures, producing large amounts of hydrofluoric acid, which further deteriorates the electrolyte quality. Therefore, the development of a semi-solid electrolyte with excellent stability and balanced room-temperature and high-temperature cycling performance is urgently needed. Summary of the Invention

[0004] The first object of the present invention is to overcome the deficiencies of the prior art and provide a semi-solid electrolyte with good stability and good cycle performance at both room temperature and high temperature.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A semi-solid electrolyte comprises a polymer monomer, an initiator, an organic solvent, a lithium salt and an additive, wherein the additive comprises one or more compounds represented by formula (I):

[0007]

[0008] Wherein, R1, R2, R3, R4, and R5 are independently selected from one of hydrogen, fluorine, alkyl, fluoroalkyl, alkoxy, and fluoroalkoxy.

[0009] Furthermore, in the compound represented by formula (I), R1, R2, and R3 are independently selected from one of hydrogen, fluorine, an alkyl group having 1-3 carbon atoms, and a fluoroalkyl group, and R4 and R5 are independently selected from one of an alkyl group having 1-3 carbon atoms, an alkoxy group having 1-3 carbon atoms, a fluoroalkyl group having 1-3 carbon atoms, and a fluoroalkoxy group having 1-3 carbon atoms.

[0010] Furthermore, the compound represented by formula (I) is selected from one or both of compound A and compound B having the structures shown below:

[0011]

[0012] Compound A and compound B in the present invention can be synthesized according to synthesis methods in the art.

[0013] Preferably, the added mass of the compound represented by formula (I) is 0.01%-5% of the total mass of the semi-solid electrolyte; preferably 0.1%-5%; further preferably 1%-5%, for example 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%; and further preferably 1%-3%.

[0014] Preferably, the additives further include other additives accounting for 0.01%-20% of the total mass of the semi-solid electrolyte.

[0015] Furthermore, the added mass of the other additives accounts for 0.1%-20% of the total mass of the semi-solid electrolyte.

[0016] Furthermore, the added mass of the other additives accounts for 2%-13% of the total mass of the semi-solid electrolyte.

[0017] Furthermore, the added mass of the other additives accounts for 3.5%-10% of the total mass of the semi-solid electrolyte.

[0018] Preferably, the other additives are selected from one or more of fluoroethylene carbonate, 1,3-propane sultone, lithium difluorophosphate, and lithium bis(fluorosulfonyl)imide; more preferably, they are one or more of 1,3-propane sultone, lithium difluorophosphate, and lithium bis(fluorosulfonyl)imide.

[0019] According to some specific and preferred embodiments, the other additives are 1,3-propane sultone, lithium difluorophosphate and lithium bis(fluorosulfonyl)imide.

[0020] Furthermore, the feed mass ratio of the 1,3-propane sultone, lithium difluorophosphate and lithium bis(fluorosulfonyl)imide is 1:(0.1-0.5)(0.5-1.5); more preferably 1:(0.2-0.3):(0.7-0.8).

[0021] Preferably, the polymerizable monomer is selected from one or more of pentaerythritol tetraacrylate, pentaerythritol triacrylate, polydipentaerythritol pentaacrylate, polydipentaerythritol hexaacrylate, and vinylene carbonate; more preferably, pentaerythritol tetraacrylate and / or pentaerythritol triacrylate.

[0022] Preferably, the added mass of the polymerized monomer is 1%-10% of the total mass of the semi-solid electrolyte; preferably 1.5%-7%; more preferably 2%-6%; and even more preferably 2%-4%.

[0023] Preferably, the initiator is a thermal initiator.

[0024] Furthermore, the initiator is selected from one or more of azobisisobutyronitrile, dimethyl azobisisobutyrate, and di-tert-butyl azodicarboxylate.

[0025] Furthermore, the initiator is azobisisobutyronitrile.

[0026] Preferably, the added mass of the initiator is 0.1%-5% of the added mass of the polymerization monomer; more preferably 0.3%-4%; even more preferably 0.5%-3%; and even more preferably 1%-2%.

[0027] Preferably, the organic solvent is selected from cyclic carbonates and / or chain carbonates; preferably cyclic carbonates and chain carbonates.

[0028] Furthermore, the cyclic carbonate is ethylene carbonate (EC) and / or propylene carbonate (PC); the chain carbonate is selected from one or more of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC).

[0029] According to some specific and preferred embodiments, the organic solvent is diethyl carbonate, ethylene carbonate and ethyl methyl carbonate.

[0030] Furthermore, the volume ratio of diethyl carbonate, ethylene carbonate and ethyl methyl carbonate is 1:(1-2):(2-4); preferably 1:(1.2-1.7):(2-3).

[0031] Preferably, the lithium salt is one or more of lithium hexafluorophosphate (LiPF6), lithium bis(oxalatoborate), lithium tetrafluoroborate, and lithium perchlorate; preferably lithium hexafluorophosphate.

[0032] Furthermore, the molar concentration of the lithium salt is 1-1.8 mol / L; more preferably 1-1.5 mol / L.

[0033] The second object of the present invention is to provide a lithium-ion battery comprising a positive electrode, a negative electrode, the semi-solid electrolyte and a separator.

[0034] A third object of the present invention is to provide a method for preparing a lithium-ion battery, comprising uniformly mixing the polymer monomer, initiator, organic solvent, lithium salt, and additives and injecting the mixture into a battery comprising a positive electrode, a negative electrode, and a separator to complete the liquid injection and sealing, and finally in-situ curing to obtain the lithium-ion battery.

[0035] Preferably, the in-situ curing temperature is 50° C.-80° C., and the curing time is 3 h-24 h.

[0036] Furthermore, the in-situ curing temperature is 55° C.-65° C., and the curing time is 8 h-12 h.

[0037] Preferably, during the in-situ curing process, a 0.5KG / cm 2 -3KG / cm 2 Pressure; preferably 0.5KG / cm 2 -2KG / cm 2 ; More preferably 0.8KG / cm 2 -1.5KG / cm 2 .

[0038] Preferably, before the in-situ curing, the battery after injection is placed at 25° C.-50° C. for 12 h-48 h.

[0039] Furthermore, before the in-situ curing, the battery after injection is placed at 30° C.-40° C. for 24 h-48 h.

[0040] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0041] The semi-solid electrolyte in the present invention comprises at least one compound represented by formula (I) as an additive, which acts together with the polymerizable monomer, initiator, organic solvent, and lithium salt in the system to promote the formation of the SEI film and improve the stability and cycle performance of the battery. In addition, the semi-solid electrolyte has few side reactions. The lithium-ion battery containing the semi-solid electrolyte of the present invention has good chemical stability and good room-temperature and high-temperature cycle performance. DETAILED DESCRIPTION

[0042] All features disclosed in this specification, or all steps in methods or processes disclosed, except for mutually exclusive features or steps, may be combined in any manner.

[0043] In view of the shortcomings of the prior art, the inventors of this case, after long-term research and extensive practice, have proposed the technical solution of the present invention. The following will further explain this technical solution, its implementation process and principles.

[0044] In the present invention, at least one of the compounds represented by formula (I) is selected as an additive, particularly an additive comprising compound A or compound B, which synergistically acts with the polymerizable monomer, initiator, organic solvent, and lithium salt to provide a semi-solid electrolyte obtained by the in-situ curing reaction with good stability and is less likely to discolor when heated. This may be because the additive not only contains a cyclic sulfate functional group, which has excellent SEI film-forming properties and improves the cycle performance of the battery, but also contains an amide functional group, which can adsorb free H in the electrolyte.+ OH - , HF, PF5 and PF6 - , inhibiting a series of side reactions in the semi-solid electrolyte, thereby better improving the stability of the semi-solid electrolyte and enhancing its room-temperature and high-temperature cycle stability, so that the resulting lithium-ion battery has both good room-temperature and high-temperature cycle stability and a low DCR growth rate.

[0045] The present invention is further described below with reference to the following examples. However, the present invention is not limited to the following examples. The implementation conditions used in the examples may be further adjusted according to the specific requirements of the application. Unspecified implementation conditions are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention may be combined with each other as long as they do not conflict with each other.

[0046] The experimental methods in the following examples are conventional methods unless otherwise specified; the experimental materials used are purchased from conventional biochemical reagent manufacturers unless otherwise specified.

[0047] It should be noted that, in the examples and comparative examples, the percentage of each substance refers to the mass percentage of the mass of each substance to the total mass of the semi-solid electrolyte.

[0048] Example 1

[0049] This embodiment provides a semi-solid electrolyte: a mixed solvent of DEC / EC / EMC in a volume ratio of 2 / 3 / 5 is weighed and fully dissolved with lithium hexafluorophosphate to a molar concentration of 1.2 mol / L. Then, 1.5% of lithium bis(fluorosulfonyl)imide, 0.5% of lithium difluorophosphate, 2% of 1,3-propane sultone, and 2% of compound A are added to the solution, respectively. Finally, 3% of a polymerizable monomer pentaerythritol tetraacrylate and 0.045% of an initiator azobisisobutyronitrile are added.

[0050] Wherein, the synthesis method of compound A is:

[0051] (1) Dissolve 16.82 mmol of N,N-dimethylacrylamide in 136 mL of a mixed solvent of acetone / water (volume ratio 4:1), cool to 0°C, and begin to dropwise add 84.1 mmol of N-methylmorpholine oxide and 1.68 mmol of osmium tetroxide (2.5%) solution. Heat to room temperature and react for 24 h. Stop the reaction, evaporate the acetone, add 140 mL of ethyl acetate to extract the aqueous layer, combine and concentrate the organic phases, and distill to obtain an oily diol as the first reaction product.

[0052] (2) Dissolve 65.6 mmol of the first-step product in 120 mL of carbon tetrachloride, add 85.2 mmol of thionyl chloride, heat to 76°C, and reflux for 4 h before stopping the reaction. Concentrate and remove low-boiling substances, then distill to obtain a colorless liquid as the second-step reaction product.

[0053] (3) 5.56 mmol of the second-step product was dissolved in 70 mL of a mixed solution of carbon tetrachloride, water, and acetonitrile (volume ratio 1:1:1.5), and 10.84 mmol of sodium periodate and 0.1 mmol of ruthenium trichloride (2%) solution were added. The temperature was raised to 40°C and the reaction was allowed to proceed for 7 h. The reaction was then stopped and cooled to room temperature. 150 mL of ether was added for extraction. The organic phase was concentrated and distilled to obtain a colorless liquid, compound A.

[0054] This embodiment also provides a lithium-ion battery: comprising a positive electrode, a negative electrode, the above-mentioned semi-solid electrolyte, and a separator, wherein.

[0055] Positive Electrode: Weigh the positive electrode material lithium nickel manganese cobalt oxide, the conductive agent acetylene black, and the binder PVDF in a mass ratio of 95:2.5:2.5, add an appropriate amount of N-methylpyrrolidone, and mix thoroughly to prepare the positive electrode slurry. The positive electrode slurry is coated on aluminum foil, dried, and then rolled and cut to obtain positive electrode sheets. The positive electrode compaction density is 4.15g / cm 3 .

[0056] Negative electrode: Weigh graphite, conductive agent acetylene black, carboxymethyl cellulose, and styrene-butadiene rubber in a mass ratio of 95:2.5:2:0.5, add an appropriate amount of deionized water, and stir thoroughly to obtain a negative electrode slurry. Apply the negative electrode slurry onto copper foil, dry it, and then roll and cut it into negative electrode sheets. The negative electrode compaction density is 1.65g / cm 3 .

[0057] This embodiment also provides a method for preparing a lithium-ion battery: using the above-mentioned positive electrode, negative electrode and semi-solid electrolyte, selecting a 12-micron thick PE separator, and using a lamination process to manufacture a soft-pack battery with a designed capacity of 5000 mAh. After the battery is filled with electrolyte and sealed, it is left at 35°C for 36 hours to ensure that the electrolyte completely penetrates the positive and negative electrode materials. It is then placed in a 60°C environment for 10 hours and subjected to a 1 kg / cm 2 The pressure is used to convert the liquid electrolyte into a semi-solid electrolyte in situ to obtain a lithium-ion battery.

[0058] Example 2

[0059] This embodiment further provides a semi-solid electrolyte, which is different from that of Example 1 in that the amount of compound A added to the semi-solid electrolyte is 1%.

[0060] A lithium ion battery was manufactured in the same manner as in Example 1.

[0061] Example 3

[0062] This embodiment further provides a semi-solid electrolyte, which is different from that of embodiment 1 in that the amount of compound A added to the semi-solid electrolyte is 3%.

[0063] A lithium ion battery was manufactured in the same manner as in Example 1.

[0064] Example 4

[0065] This embodiment also provides a semi-solid electrolyte, which is different from the embodiment 1 in that the amount of compound A added to the semi-solid electrolyte is 5%.

[0066] A lithium ion battery was manufactured in the same manner as in Example 1.

[0067] Example 5

[0068] This embodiment further provides a semi-solid electrolyte, which is different from Example 1 in that compound A is replaced by compound B in the semi-solid electrolyte, and the addition amount of compound B is 1%.

[0069] Wherein, the synthesis method of compound B is:

[0070] (1) 16.82 mmol of N-methoxy-N-methylacetamide was dissolved in 136 mL of a mixed solvent of tert-butanol / water (volume ratio 1:1), cooled to 0°C, and 84.1 mmol of methanesulfonamide and 1.68 mmol of AD-mixβ were added dropwise. The reaction was allowed to proceed for 12 h, and the reaction was stopped. The tert-butanol was evaporated, and 140 mL of ethyl acetate was added to extract the aqueous layer. The organic phases were combined and concentrated, and distilled to obtain an oily diol as the first reaction product.

[0071] (2) Dissolve 65.6 mmol of the first-step product in 120 mL of carbon tetrachloride, add 85.2 mmol of thionyl chloride, heat to 76°C, and reflux for 4 h before stopping the reaction. Concentrate and remove low-boiling substances, then distill to obtain a colorless liquid as the second-step reaction product.

[0072] (3) 5.56 mmol of the second-step product was dissolved in 70 mL of a mixed solution of carbon tetrachloride, water, and acetonitrile (volume ratio 1:1:1.5), and 10.84 mmol of sodium periodate and 0.1 mmol of ruthenium trichloride (2%) solution were added. The temperature was raised to 40°C and the reaction was allowed to proceed for 7 h. The reaction was then stopped and cooled to room temperature. 150 mL of ether was added for extraction. The organic phase was concentrated and distilled to obtain a colorless liquid, compound B.

[0073] A lithium ion battery was manufactured in the same manner as in Example 1.

[0074] Example 6

[0075] This embodiment also provides a semi-solid electrolyte, which is different from that of embodiment 5 in that the amount of compound B added to the semi-solid electrolyte is 2%.

[0076] A lithium ion battery was manufactured in the same manner as in Example 1.

[0077] Example 7

[0078] This embodiment also provides a semi-solid electrolyte, which is different from that of embodiment 5 in that the amount of compound B added to the semi-solid electrolyte is 3%.

[0079] A lithium ion battery was manufactured in the same manner as in Example 1.

[0080] Example 8

[0081] This embodiment also provides a semi-solid electrolyte, which is different from that of embodiment 5 in that the amount of compound B added to the semi-solid electrolyte is 5%.

[0082] A lithium ion battery was manufactured in the same manner as in Example 1.

[0083] Comparative Example 1

[0084] This embodiment also provides a semi-solid electrolyte, which is different from Example 1 in that compound A is replaced with vinyl sulfate in the semi-solid electrolyte, and the added amount of vinyl sulfate is 1%.

[0085] A lithium ion battery was manufactured in the same manner as in Example 1.

[0086] Comparative Example 2

[0087] This embodiment also provides a semi-solid electrolyte, which is different from Example 1 in that compound A is replaced with vinyl sulfate in the semi-solid electrolyte, and the added amount of vinyl sulfate is 2%.

[0088] A lithium ion battery was manufactured in the same manner as in Example 1.

[0089] Comparative Example 3

[0090] This embodiment also provides a semi-solid electrolyte, which is different from Example 1 in that compound A is replaced with vinyl sulfate in the semi-solid electrolyte, and the amount of vinyl sulfate added is 3%.

[0091] A lithium ion battery was manufactured in the same manner as in Example 1.

[0092] Comparative Example 4

[0093] This embodiment also provides a semi-solid electrolyte, which is different from Example 1 in that compound A is replaced with vinyl sulfate in the semi-solid electrolyte, and the added amount of vinyl sulfate is 5%.

[0094] A lithium ion battery was manufactured in the same manner as in Example 1.

[0095] Comparative Example 5

[0096] This embodiment also provides a semi-solid electrolyte, which is different from Example 1 in that: Compound A in the semi-solid electrolyte is replaced by N,N-dimethylacetamide, and the added amount of N,N-dimethylacetamide is 1%.

[0097] A lithium ion battery was manufactured in the same manner as in Example 1.

[0098] Comparative Example 6

[0099] This embodiment also provides a semi-solid electrolyte, which is different from Example 1 in that: Compound A in the semi-solid electrolyte is replaced by N,N-dimethylacetamide, and the added amount of N,N-dimethylacetamide is 2%.

[0100] A lithium ion battery was manufactured in the same manner as in Example 1.

[0101] Comparative Example 7

[0102] This embodiment also provides a semi-solid electrolyte, which is different from Example 1 in that: Compound A in the semi-solid electrolyte is replaced by N,N-dimethylacetamide, and the added amount of N,N-dimethylacetamide is 3%.

[0103] A lithium ion battery was manufactured in the same manner as in Example 1.

[0104] Comparative Example 8

[0105] This embodiment also provides a semi-solid electrolyte, which is different from Example 1 in that compound A is replaced with N-methoxy-N-methylacetamide in the semi-solid electrolyte, and the added amount of N-methoxy-N-methylacetamide is 1%.

[0106] A lithium ion battery was manufactured in the same manner as in Example 1.

[0107] Comparative Example 9

[0108] This embodiment also provides a semi-solid electrolyte, which is different from Example 1 in that compound A is replaced with N-methoxy-N-methylacetamide in the semi-solid electrolyte, and the added amount of N-methoxy-N-methylacetamide is 2%.

[0109] A lithium ion battery was manufactured in the same manner as in Example 1.

[0110] Comparative Example 10

[0111] This embodiment also provides a semi-solid electrolyte, which is different from Example 1 in that compound A is replaced with N-methoxy-N-methylacetamide in the semi-solid electrolyte, and the added amount of N-methoxy-N-methylacetamide is 3%.

[0112] A lithium ion battery was manufactured in the same manner as in Example 1.

[0113] Comparative Example 11

[0114] This embodiment also provides a semi-solid electrolyte, which differs from Example 1 in that: Compound A is not added to the semi-solid electrolyte, but vinyl sulfate and N,N-dimethylacetamide are added, and the addition amount of vinyl sulfate and N,N-dimethylacetamide is 1%.

[0115] A lithium ion battery was manufactured in the same manner as in Example 1.

[0116] Comparative Example 12

[0117] This embodiment also provides a semi-solid electrolyte, which differs from Example 1 in that: instead of adding compound A, vinyl sulfate and N-methoxy-N-methylacetamide are added to the semi-solid electrolyte, and the addition amount of vinyl sulfate and N-methoxy-N-methylacetamide is 1%.

[0118] A lithium ion battery was manufactured in the same manner as in Example 1.

[0119] Comparative Example 13

[0120] This embodiment also provides a semi-solid electrolyte, which is different from Example 1 in that compound A, compound B and vinyl sulfate are not added to the semi-solid electrolyte.

[0121] A lithium ion battery was manufactured in the same manner as in Example 1.

[0122] Performance Testing

[0123] 1. Color change experiment:

[0124] The semi-solid electrolytes prepared in the examples and comparative examples were placed in a 60°C temperature for 24 hours to observe whether they changed color. The test results are shown in Table 1.

[0125] Table 1 Discoloration of the semi-solid electrolytes of Examples 1-8 and Comparative Examples 1-13

[0126]

[0127]

[0128] 2. Battery performance test:

[0129] Battery charge and discharge tests were conducted at 25°C and 45°C, with a voltage range of 2.75-4.25V. The battery was cycled at a 1C rate, and capacity retention was measured after 1000 cycles. The battery's DC internal resistance (DCR) was measured after every 50 cycles of 1C discharge for 30 seconds to 50% state of charge.

[0130] Capacity retention (%) = (discharge capacity after 1000 cycles / discharge capacity after the first cycle) × 100%.

[0131] 1000-week DCR growth rate (%) = (DCR of 1000 cycles - DCR of the first week) / DCR of the first week × 100%.

[0132] The test results are shown in Table 2-3.

[0133] Table 2 Normal temperature cycle performance of Examples 1-8 and Comparative Examples 1-13

[0134]

[0135]

[0136] Table 3 45°C cycle performance of Examples 1-8 and Comparative Examples 1-13

[0137]

[0138]

[0139] From the comparison of Examples 1-8 and Comparative Examples 1-13, it can be seen that after adding different proportions of vinyl sulfate, the capacity retention rate of the semi-solid electrolyte at room temperature and high temperature is significantly improved, and the DCR growth is suppressed. However, with the addition of vinyl sulfate, the color of the semi-solid electrolyte changes from milky white to light yellow, which indicates that vinyl sulfate undergoes violent side reactions during the long thermal curing process; after adding different proportions of N,N-dimethylacetamide and N-methoxy-N-methylacetamide, the room temperature and high temperature performance of the semi-solid battery is significantly deteriorated. After introducing different proportions of the two chemical substances of the present invention (Compound A and Compound B), the semi-solid electrolyte still maintains a milky white color, and the room temperature and high temperature performance are significantly improved compared to the system with vinyl sulfate, with the best addition amount of 2%. However, adding vinyl sulfate and amide compounds alone will exacerbate the occurrence of side reactions and further deteriorate battery performance. Therefore, the two chemical substances of the present invention can improve the stability of the semi-solid electrolyte through the synergistic effect of the cyclic sulfate and amide functional groups, while also improving the room temperature and high temperature cycling performance.

[0140] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. All equivalent modifications made based on the spirit and essence of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A semi-solid electrolyte, characterized in that: The method comprises a polymerization monomer, an initiator, an organic solvent, a lithium salt and an additive, wherein the additive comprises one or more compounds represented by formula (I): ; wherein R1, R2, and R3 are independently selected from one of hydrogen, fluorine, an alkyl group with 1-3 carbon atoms, and a fluoroalkyl group with 1-3 carbon atoms; R4 and R5 are independently selected from one of an alkyl group with 1-3 carbon atoms, an alkoxy group with 1-3 carbon atoms, a fluoroalkyl group with 1-3 carbon atoms, and a fluoroalkoxy group with 1-3 carbon atoms.

2. The semi-solid electrolyte according to claim 1, characterized in that: The compound represented by formula (I) is selected from one or both of compound A and compound B having the following structures: 。 3. The semi-solid electrolyte according to claim 1, characterized in that: The added mass of the compound represented by formula (I) is 0.01%-5% of the total mass of the semi-solid electrolyte.

4. The semi-solid electrolyte according to claim 3, characterized in that: The added mass of the compound represented by formula (I) is 1%-5% of the total mass of the semi-solid electrolyte.

5. The semi-solid electrolyte according to claim 1, characterized in that: The additives further include other additives accounting for 0.01%-20% of the total mass of the semi-solid electrolyte, and the other additives are selected from one or more of fluoroethylene carbonate, 1,3-propane sultone, lithium difluorophosphate, and lithium bis(fluorosulfonyl)imide.

6. The semi-solid electrolyte according to claim 1, characterized in that: The polymerizable monomer is selected from one or more of pentaerythritol tetraacrylate, pentaerythritol triacrylate, polydipentaerythritol pentaacrylate, polydipentaerythritol hexaacrylate, and vinylene carbonate; and / or the added mass of the polymerizable monomer is 1%-10% of the total mass of the semi-solid electrolyte.

7. The semi-solid electrolyte according to claim 1, characterized in that: The initiator is a thermal initiator.

8. The semi-solid electrolyte according to claim 1, characterized in that: The initiator is selected from one or more of azobisisobutyronitrile, dimethyl azobisisobutyrate, and di-tert-butyl azodicarboxylate.

9. The semi-solid electrolyte according to claim 1, characterized in that: The added mass of the initiator is 0.1%-5% of the added mass of the polymerization monomer.

10. A lithium-ion battery comprising a positive electrode and a negative electrode, characterized in that: It also includes the semi-solid electrolyte and the separator according to any one of claims 1 to 9.

11. A method for preparing a lithium-ion battery according to claim 10, characterized in that: The polymerization monomer, initiator, organic solvent, lithium salt and additive are mixed evenly and then injected into a battery comprising a positive electrode, a negative electrode and a separator to complete the liquid injection and sealing, and finally the lithium ion battery is obtained by in-situ curing.

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