Gel-like ionic liquid electrolyte, method for preparing the same, and lithium ion battery

Abstract

This invention belongs to the field of lithium-ion battery technology, and particularly relates to a gel-state ionic liquid electrolyte for lithium-ion batteries and its preparation method. It includes an ionic liquid matrix, a lithium salt, a non-solventizing diluent, a polymer matrix, and an initiator. The ionic liquid matrix comprises cations and anions of the ionic liquid matrix, and the anions include a first anion and a second anion. The polymer matrix is ​​a network structure formed by in-situ polymerization of a polymer precursor. The bi-anionic gel-state ionic liquid electrolyte prepared in this application solves the problems of conventional solvents participating in the solvation sheath of lithium ions, resulting in an unstable SEI film, increased interfacial impedance, and poor rate performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and particularly relates to a gel-state ionic liquid electrolyte for lithium-ion batteries and its preparation method. Background Technology

[0002] With the increasing demand for longer driving range in new energy vehicles and 3C electronic products, lithium-ion batteries are developing towards higher energy density, and the application of high-voltage cathode materials (such as NCM811 and high-voltage lithium cobalt oxide) is becoming increasingly widespread. However, traditional carbonate-based liquid electrolytes are prone to oxidation and decomposition at high voltages (>4.3V), producing gas and increasing interfacial impedance. At the same time, liquid electrolytes pose safety hazards such as flammability and leakage, making it difficult to meet the stringent safety requirements of high-energy-density batteries.

[0003] Ionic liquids are considered an ideal choice for improving battery safety due to their flame-retardant, low-volatility, and wide electrochemical window properties. However, conventional ionic liquid electrolytes face two major bottlenecks: first, their high viscosity and poor wettability result in low ionic conductivity and poor rate performance; second, their poor interfacial compatibility with lithium / graphite anodes makes it difficult to form a stable solid electrolyte interfacial (SEI) film.

[0004] Currently, existing technologies often involve dilution with organic solvents, but this frequently compromises the flame-retardant properties of ionic liquids. Furthermore, conventional solvents participate in the solvation sheath of lithium ions, resulting in an unstable SEI film at the interface, leading to increased interfacial impedance, poor rate performance, and reduced overall electrolyte oxidation resistance. Another approach is to prepare all-solid-state polymer electrolytes, but their room-temperature ionic conductivity is typically too low (<10). -5 The S / cm ratio is insufficient to meet the requirements for normal temperature operation.

[0005] Therefore, there is an urgent need to develop an electrolyte system that can maintain the high safety and high pressure resistance of ionic liquids while solving the problems of high viscosity and poor interface. Summary of the Invention

[0006] In view of this, this application provides a gel-state ionic liquid electrolyte for lithium-ion batteries and a method for preparing the same, in order to overcome the defects of the prior art.

[0007] To achieve the above objectives, the technical solution adopted in this application is as follows: In a first aspect, this application provides a gel-state ionic liquid electrolyte, comprising an ionic liquid matrix, a lithium salt, a non-solventizing diluent, a polymer matrix, and an initiator; the ionic liquid matrix comprises cations and anions of the ionic liquid matrix, the anions of the ionic liquid matrix comprising a first anion and a second anion, and the polymer matrix being a network structure formed by in-situ polymerization of a polymer precursor.

[0008] It should be noted that: in the ionic liquid matrix, the bi-anion system and lithium salt form a lithium-ion solvation structure with anion participation as the main component; the dielectric constant of the non-solventizing diluent is less than 5 and does not participate in the first solvation sheath of lithium ions, and is used to reduce electrolyte viscosity and weaken ion association; the polymer matrix is ​​a network structure formed by in-situ polymerization of polymer precursor monomers, which runs through the electrolyte.

[0009] Furthermore, the first anion is difluorosulfonyl imide (FSI). - DFOB (difluorooxalate borate) - Tetrafluoroborate (BF4) - One or more of the following; the second anion is bis(trifluoromethanesulfonyl)imide (TFSI). - Trifluoromethanesulfonate OTF - Perfluorobutyl sulfonate (PFBS) - One or more of them.

[0010] Furthermore, the molar ratio of the first anion to the second anion is 1:(0.2-3.0), preferably, the molar ratio of the first anion to the second anion is 2:1.

[0011] Furthermore, the lithium ions Li in the gel-state ionic liquid electrolyte + The molar ratio of Li to total anions is 1:X, where 1.8 ≤ X ≤ 2.2. Preferably, Li + The molar ratio of lithium salt to total anions is 1:2; preferably, the concentration of lithium salt is 0.5-2.0 mol / L. The non-solvent diluent accounts for 20%-60% of the total volume of the ionic liquid matrix, lithium salt, and non-solvent diluent mixture; The polymer precursor accounts for 1%-10% of the total mass of the mixture of ionic liquid, lithium salt, and non-solventized diluent; The mass of the initiator is 0.1%-1% of the mass of the polymer precursor.

[0012] Furthermore, the coordination ability of the first anion is greater than that of the second anion.

[0013] It is important to note that the coordination ability of an ion is usually reflected by the donor number DN, meaning the first anion donor number DN > the second anion donor number DN. The higher the DN, the stronger the coordination ability. A larger DN also indicates a stronger electron-donating ability, and thus a stronger affinity for Li. + The tighter the bond, the easier it is for Li to enter. +The first solvation sheath implies that the first anion has strong coordination and strong binding, and can enter the solvation sheath, while the second anion has weak coordination and weak binding, and is not easy to enter the solvation sheath. The first anion with high DN can preferentially form a stable SEI film at the electrode interface, while the second anion with low DN has weaker coordination, which helps to improve the ion transport efficiency of the system, thus obtaining a stable interface without sacrificing conductivity.

[0014] Furthermore, the cation of the ionic liquid matrix is ​​one or more of imidazole, pyrrolidone, piperidinium, quaternary ammonium, or quaternary phosphorus cations, preferably N-methyl-N-butylpyrrolidone (Pyr). 14 + Or 1-ethyl-3-methylimidazolium (EMIM) + .

[0015] Furthermore, the non-solvent diluent is selected from hydrofluoroether compounds (HFE), preferably 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) or 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether.

[0016] Furthermore, the lithium salt is lithium bisfluorosulfonylimide (LiFSI) or lithium bistrifluoromethylsulfonylimide (LiTFSI); The polymer precursor is selected from one or more of polyethylene glycol diacrylate (PEGDA), pentaerythritol tetraacrylate (PETEA), and trimethylolpropane triacrylate (TMPTA). The initiator is azobisisobutyronitrile (AIBN).

[0017] It should be noted that this application incorporates azobisisobutyronitrile (AIBN) as a thermal initiator. The thermal initiation temperature is mild, which will not damage the electrode or electrolyte. The decomposition is uniform, with few side reactions, and it has good compatibility with ionic liquids and lithium salts (LiFSI, LiTFSI).

[0018] In a second aspect, this application provides a method for preparing the gel-state ionic liquid electrolyte described above, comprising the following steps: mixing an ionic liquid matrix and a lithium salt, stirring to form a homogeneous solution, adding a non-solventizing diluent and mixing evenly, adding a polymer precursor, simultaneously adding an initiator and heating to cause the polymer precursor to undergo in-situ polymerization, thereby forming a gel-state ionic liquid electrolyte.

[0019] A third aspect of this application provides a lithium-ion battery comprising the aforementioned gel-state ionic liquid electrolyte, a positive electrode, a negative electrode, and a separator. Preferably, the active material of the positive electrode has an operating voltage of not less than 4.3V vs. Li / Li. + .

[0020] Compared with the prior art, the beneficial effects of the present invention are: This application solves the problems of unstable SEI films formed by conventional solvents participating in the solvation sheath of lithium ions, leading to increased interfacial impedance and poor rate performance, by preparing a dual-anion gel-state ionic liquid electrolyte. Specifically: (1) Adding a non-solventizing diluent to the ionic liquid matrix solves the problem of high viscosity in ionic liquids. Furthermore, the non-solventizing diluent does not dissolve lithium salts and does not participate in the solvation sheath of lithium ions. Simultaneously, it works synergistically with dianionization (FSI). - With TFSI - ) and Li + Coordination, i.e., FSI - Strong coordination and TFSI - The synergy of weak coordination greatly improves the poor interface defects.

[0021] (2) The three-dimensional network structure is formed by in-situ polymerization of polymer, which makes the structure more stable and further improves the interfacial stability and cycle life of electrolyte under high voltage conditions.

[0022] (3) It maintains good ion transport performance under gel conditions. The ionic conductivity at 25℃ is ≥2.8mS / cm, which significantly reduces the viscosity of the system and battery polarization. It also has both high safety and high energy density, making it suitable for energy storage and 3C lithium-ion batteries. Among them, the high safety is reflected in the fact that the battery system is non-flammable and leak-proof, which significantly improves the thermal safety performance of the battery. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the microstructure of the gel-state ionic liquid electrolyte prepared in Example 1 of this application, wherein the figure shows the distribution of the polymer network, the bis-anionic solvation structure and the non-solvent diluent; Figure 2 This is a bar chart comparing the ionic conductivity of the electrolytes in Examples 1-2 and Comparative Examples 1-3 of this application at 25°C. Figure 3 This is a comparison curve of the cycling performance of NCM811 / Li half-cells of Example 1 and Comparative Example 1 under a high voltage condition of 4.5V. Figure 4 This is a comparison of the electrochemical impedance spectroscopy (EIS) spectra of Example 1 and Comparative Example 1 after cycling. Detailed Implementation

[0024] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments.

[0025] Example 1: Preparation of Pyr 14-FSI / TFSI system gel-state ionic liquid electrolyte, wherein, FSI - :TFSI - Molar ratio 1:1 1. Construction of gel-state ionic liquid electrolyte system (1) Bianionic liquid matrix: N-methyl-N-butylpyrrolidone onion (Pyr 14 + ) was selected as the organic cation. Difluorosulfonylimide (FSI) was chosen. - ) was selected as the first anion (its strong coordination is beneficial for SEI film formation), and bis(trifluoromethanesulfonyl)imide (TFSI) was chosen. - As the second anion (its weak coordination is beneficial for high stability). Both (FSI) - TFSI - The molar ratio of Pyr is 1:1. Specific dosage: Pyr 14 The mass of FSI is 16.12 g (where the molar mass is approximately 322.4 g / mol and the molar mass is 0.05 mol), and the mass of Pyr is... 14 The mass of TFSI is 21.12 g (where the molar mass is approximately 422.42 g / mol and the molar mass is 0.05 mol). After mixing, the total mass of the ionic liquid matrix formed is 36.95 g, the volume is approximately 30 mL, and the density is 1.23 g / cm³. 3 calculate).

[0026] (2) Lithium salt dissolution: Add 18.71 g of lithium salt LiFSI to the above mixture (wherein, molar mass ≈ 187.07 g / mol, molar amount = 0.1 mol). Stir until completely dissolved, forming a high-concentration dianion / lithium salt complex. At this point, Li + The molar ratio of total anions to total anions is 1:2.

[0027] (3) Dilution and gelation formulation: A non-solventizable diluent, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), was added to the above bianionic / lithium salt complex. The volume ratio of TTE added to the ionic liquid mixture was 1:1 (approximately 30 mL), and its density was approximately 1.53 g / mL, corresponding to a mass of 45.9 g, meaning that the volume percentage of TTE in the total mixture was 50%. Polyethylene glycol diacrylate (PEGDA, Mn=400) was then added, at a rate of 3.83 wt% of the total mass of the mixture (corresponding to a mass of 3.90 g); simultaneously, azobisisobutyronitrile (AIBN) was added, at a rate of 0.038 g (approximately 1% of the mass of PEGDA).

[0028] 2. Battery assembly and in-situ polymerization The polymer precursor solution obtained above was injected into the NCM811 positive electrode (loading 12 mg / cm³). 2 It is incorporated into CR2032 coin cells with lithium metal anodes. After standing and soaking for 2 hours, it is placed in a 60°C oven and heated for 12 hours to allow PEGDA to polymerize in situ, forming a gel-like bi-anionic liquid electrolyte.

[0029] 3. Performance Testing Tests showed that the gel-state ionic liquid electrolyte has an ionic conductivity of 2.8 mS / cm at 25℃, a capacity retention of 92.5% after 200 cycles at 4.5V, an interfacial impedance of Rct=45Ω, and is non-flammable, combining high ion transport performance with high voltage stability.

[0030] Example 2: Preparation of Pyr 14 -FSI / TFSI system gel-state ionic liquid electrolyte, adjusting the dianion ratio (FSI) - :TFSI - (Molar ratio 2:1) The only difference from Example 1 is the adjustment of the anion ratio: weigh Pyr 14 The mass of FSI was 21.49 g (0.067 mol) and Pyr 14 The mass of TFSI is 14.08 g (0.033 mol). At this point, the first anion (FSI) - ) and the second anion (TFSI) - The molar ratio of ) was adjusted to 2:1. The amounts of the remaining components were as follows: 18.71 g (0.1 mol) of LiFSI, 30 mL of TTE, 3.85 g of PEGDA, and 0.039 g of AIBN, with the others remaining unchanged.

[0031] 2. Battery assembly and in-situ polymerization Same as Example 1.

[0032] 3. Performance Testing Tests showed that adding the first anion FSI... - After adjusting the content, a denser LiF-based SEI film is formed on the negative electrode surface, the ionic conductivity at 25℃ increases to 3.1 mS / cm, the capacity retention rate is 94.1% after 200 cycles at 4.5V, the interface impedance Rct=38Ω, and the high voltage stability is further improved, verifying that adjusting the ratio of dual anions further optimizes the performance of lithium-ion batteries.

[0033] Comparative Example 1: Preparation of monoanion ionic liquid electrolytes (FSI-free) - ) Using pure Pyr14 The mass of TFSI is 41.65 g (molar amount = 0.1 mol) as the ionic liquid matrix (without FSI). - The lithium salt was still LiFSI with a mass of 18.71 g (molar amount = 0.1 mol), and the other components (TTE volume of 30 mL, PEGDA mass of 3.8 g, AIBN mass of 0.038 g) and in-situ polymerization conditions were the same as in Example 1.

[0034] Performance testing: Tests showed that it lacked highly active FSI. - The SEI film, which participates in the solvation layer, exhibits poor stability, with an ionic conductivity of only 1.9 mS / cm at 25°C, a capacity retention of 81.2% after 200 cycles at 4.5V, and an interfacial impedance of Rct = 85 Ω. Its polarization is significantly greater than in the previous example. Overall, this is due to the lack of highly active and strongly coordinated FSIs in the ionic liquid system. - It failed to effectively bind with lithium ions and participate in the formation of the solvation layer, affecting the formation of the SEI film or the stability of the SEI film. At the same time, the migration of lithium ions was hindered, affecting the ionic conductivity of the system.

[0035] Comparative Example 2: Preparation of ionic liquid electrolytes without added non-solvent diluents The preparation process is the same as in Example 1, but without the addition of TTE diluent.

[0036] Performance Testing: The ionic liquid electrolyte exhibits extremely high viscosity (>200 mPa·s), severe ion association, and an ionic conductivity of only 0.5 mS / cm at 25°C. After 200 cycles at 4.5V, the capacity retention is 85.3%, and the interfacial impedance Rct = 120 Ω. Both rate performance and cycle stability are significantly deteriorated. This is primarily due to the ionic liquid matrix (Pyr... 14 FSI+Pyr 14 TFSI is a room-temperature ionic liquid. Due to the strong interionic forces, the viscosity of this type of ionic liquid is higher than that of ordinary organic solvents. After adding PEGDA (polymer precursor), the viscosity of the system will increase further, which will inevitably lead to the obstruction of ion migration and thus affect the ionic conductivity.

[0037] Comparative Example 3: Prepare a traditional liquid electrolyte as a blank control. Construction of liquid electrolyte system: Commercially available conventional liquid electrolytes were used as a reference: 1.0 mol / L LiPF6 was dissolved in a mixed solvent of EC:EMC:DMC=1:1:1 (volume ratio), which did not contain ionic liquid matrix (bis-anion) or polymer matrix.

[0038] The battery assembly followed conventional processes, injecting the electrolyte into the same CR2032 coin cell as in Example 1, without an in-situ polymerization step.

[0039] Performance testing: Tests showed that the ionic conductivity at 25℃ was 8.5 mS / cm (an inherent advantage of liquid systems), but it was easily oxidized and decomposed under a high voltage of 4.5V. After 200 cycles, the capacity retention rate was only 76.4%, and it was flammable. Its safety was far lower than that of the gel-state ionic liquid electrolyte of this application.

[0040] Performance test results and analysis of Examples 1-2 and Comparative Examples 1-3: The electrolytes obtained in Examples 1, 2, and Comparative Examples 1–3 were applied to lithium-ion batteries, and performance tests were conducted under the same conditions, including ionic conductivity testing, AC impedance testing, and high-voltage cycling performance testing. The results are shown in Table 1 below: Table 1

[0041] Test results show that the gel-state dual-anionic ionic liquid electrolyte prepared in this application significantly improves high-voltage stability and safety while maintaining good ion transport performance, and also possesses flame retardancy. Its overall performance is far superior to that of single-anionic gel-state ionic liquid electrolytes, gel-state ionic liquid electrolytes without added diluents, and traditional liquid electrolytes, fully verifying that the use of dual-anionic ionic liquid electrolytes and the addition of non-solvent diluents to form a gel network structure through in-situ polymerization achieves a synergistic effect.

[0042] Figure 1 This is a microstructure diagram of the gel-state ionic liquid electrolyte of this application. The gray network structure represents the PEGDA polymer network formed by in-situ polymerization. It constructs a three-dimensional spatially confined framework, physically locking the liquid components and achieving gelation of the electrolyte, effectively preventing leakage. The core lithium-ion solvation cluster consists of a central lithium ion (purple sphere) and its tightly coordinated FSI. - (Blue) and TFSI - (Green) Bi-anionic composition, in which the blue ellipse (FSI) - The first anion surrounds the lithium ion, forming a strong coordination with it, and enhances the stability of the solvation structure through the interaction of charge with the lithium ion; the green ellipse (TFSI) -The second anion, further encircling the blue ellipse, represents the second anion. While its coordination with lithium ions is weaker, it still supports the solvation structure, enhancing the overall stability. This "anion-dominated solvation structure" is a key foundation for forming a highly stable LiF-rich interface film (SEI). Importantly, the dispersed yellow squares in the figure represent non-solvable diluents (TTEs). These are distributed in the voids outside the solvation clusters and do not participate in the first solvation sheath layer of lithium ions, thus maintaining the structural integrity of the lithium-ion solvation sheath. This distribution pattern demonstrates that the diluents only serve to physically fill and reduce the system viscosity without disrupting the coordination environment between lithium ions and anions, thereby ensuring the high voltage stability of the electrolyte.

[0043] Figure 2 The graph shows a comparison of the ionic conductivity of the electrolytes in Examples 1-2 and Comparative Examples 1-3 at 25°C. Although the conventional liquid electrolyte (Comparative Example 3) has the highest ionic conductivity (8.5 mS / cm) due to its intrinsic liquid properties, the gel electrolytes in Examples 1 and 2 of this application have conductivity values ​​of 2.8 mS / cm and 3.1 mS / cm, respectively. This value is significantly better than that of Comparative Example 2 (0.5 mS / cm without diluent) and the single anion liquid electrolyte of Comparative Example 1 (1.9 mS / cm).

[0044] The above comparison results show that high viscosity is the main bottleneck limiting ion transport in pure ionic liquid systems. This application, by introducing a non-solventizing diluent with a low dielectric constant, significantly reduces the system viscosity while maintaining the gel network structure, increasing ionic conductivity by 5-6 times. This successfully solves the problem of low room-temperature conductivity (<10) of traditional polymer electrolytes. -5 The problem of S / cm was solved, and the requirement for the battery to operate at room temperature was met.

[0045] Figure 3 This section compares the cycling performance of Examples 1-2 and Comparative Examples 1-3 at a high voltage of 4.5V. It also shows the long-term cycling stability of the half-cell with the NCM811 cathode at a high cutoff voltage of 4.5V.

[0046] The above comparison results show that: Traditional liquid electrolyte (Comparative Example 3, gray dotted line): The cycling curve shows a rapid downward trend, and the capacity retention rate is only 76.4% after 200 cycles. This is mainly attributed to the severe oxidative decomposition of the carbonate solvent under high voltage.

[0047] The embodiments of this application (black / red solid lines) exhibit superior cycling stability, with Examples 1 and 2 showing capacity retention of 92.5% and 94.1%, respectively, after 200 cycles. This is attributed to the dual anion (FSI) - / TFSI- A robust and dense SEI film is formed on the negative electrode side, while the antioxidant properties of the non-solvent diluent prevent the decomposition of solvent molecules on the positive electrode surface, thus achieving dual protection of the positive and negative electrode interfaces.

[0048] The single-anion ionic liquid electrolyte (Comparative Example 1, blue dashed line): its capacity retention rate after 200 cycles at 4.5V was 81.2%, significantly lower than that of the dual-anion system, proving that FSI... - With TFSI - The synergistic effect of these components plays an irreplaceable role in constructing stable interfacial membranes and improving cycle life.

[0049] Figure 4 To compare the AC impedance spectra (EIS) of the lithium-ion batteries in the examples and comparative examples, the diameter of the semicircle of the Nyquist curve is used to reflect the charge transfer impedance (Rct) of the battery.

[0050] The above comparison results show that: Examples 1 and 2 (black / red lines): The Rct values ​​are the smallest, at 45Ω and 38Ω respectively, which are very close to the level of conventional liquid electrolytes. Comparative Example 3 (gray line) has an Rct value of 35Ω. This shows that although the gel-state ionic liquid electrolyte of this application is quasi-solid, through dilution and in-situ polymerization, a low-resistance interface channel with excellent wettability is formed on the electrode surface.

[0051] The gel-state ionic liquid electrolyte without added diluent (Comparative Example 2, orange line): its maximum Rct value is 120Ω, indicating that the high viscosity leads to poor contact between the electrolyte and the electrode and huge interfacial transport resistance.

[0052] The monoanion gel-state ionic liquid electrolyte (Comparative Example 1, blue line): with an Rct value of 85 Ω, is significantly higher than that of Examples 1 and 2, confirming the lack of a highly active FSI. - Participation in film formation can lead to the degradation of SEI film properties, thereby increasing interfacial impedance.

[0053] In summary, this application obtains a gel-state ionic liquid electrolyte through a technical route of "dual anion synergy + non-solventizing diluent + in-situ polymerization gelation". The added non-solventizing diluent successfully overcomes the high viscosity of the ionic liquid, and since it does not dissolve lithium salts and does not participate in the solvation sheath of lithium ions, the dual anion synergy (FSI)... - With TFSI - ), i.e., FSI - Strong coordination and TFSI -The synergistic effect of weak coordination greatly improves the interface defect, achieving higher voltage stability (≥4.5V) and safety (with flame retardancy) than traditional liquid electrolytes. Moreover, the gel-state ionic liquid electrolyte is suitable for lithium-ion batteries with a working voltage of not less than 4.3V, making it a high-energy-density battery electrolyte solution with great application prospects.

[0054] The above description is merely an example of the embodiments of the present invention. It should be noted that, for those skilled in the art, various equivalent substitutions or modifications can be made to the present invention without departing from the spirit and essence of the present invention, and such equivalent substitutions or modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A gel-state ionic liquid electrolyte, characterized in that, It includes an ionic liquid matrix, a lithium salt, a non-solventizing diluent, a polymer matrix, and an initiator; the ionic liquid matrix includes cations and anions of the ionic liquid matrix, the anions of the ionic liquid matrix include a first anion and a second anion, and the polymer matrix is ​​a network structure formed by in-situ polymerization of polymer precursors.

2. The gel-state ionic liquid electrolyte according to claim 1, characterized in that, The first anion is bis(fluorosulfonyl)imide (FSI) - DFOB (difluorooxalate borate) - Tetrafluoroborate (BF4) - One or more of the following; the second anion is bis(trifluoromethanesulfonyl)imide (TFSI). - Trifluoromethanesulfonate OTF - Perfluorobutyl sulfonate (PFBS) - One or more of them.

3. The gel-state ionic liquid electrolyte according to claim 1, characterized in that, The molar ratio of the first anion to the second anion is 1:(0.2-3.0), preferably, the molar ratio of the first anion to the second anion is 2:

1.

4. The gel-state ionic liquid electrolyte according to claim 1, characterized in that, Lithium ions (Li) in gel-state ionic liquid electrolyte + The molar ratio of Li to total anions is 1:X, where 1.8 ≤ X ≤ 2.

2. Preferably, Li + The molar ratio of lithium salt to total anions is 1:2; preferably, the concentration of lithium salt is 0.5-2.0 mol / L. The non-solvent diluent accounts for 20%-60% of the total volume of the ionic liquid matrix, lithium salt, and non-solvent diluent mixture; The polymer precursor accounts for 1%-10% of the total mass of the mixture of the ionic liquid matrix, lithium salt, and non-solventized diluent; The initiator accounts for 0.1%-1% of the mass of the polymer precursor.

5. The gel-state ionic liquid electrolyte according to claim 1, characterized in that, The coordination ability of the first anion is greater than that of the second anion.

6. The gel-state ionic liquid electrolyte according to claim 1, characterized in that, The cation of the ionic liquid matrix is ​​one or more of imidazole, pyrrolidine-onium, piperidinium, quaternary ammonium, or quaternary phosphorus cations, preferably N-methyl-N-butylpyrrolidine-onium (Pyr). 14 + Or 1-ethyl-3-methylimidazolium (EMIM) + .

7. The gel-state ionic liquid electrolyte according to claim 1, characterized in that, The nonsolvent diluent is selected from hydrofluoroether compounds (HFE), preferably 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) or 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether.

8. The gel-state ionic liquid electrolyte according to claim 1, characterized in that, The lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI) or lithium bis(trifluoromethyl)sulfonyl)imide (LiTFSI); The polymer precursor is selected from one or more of polyethylene glycol diacrylate (PEGDA), pentaerythritol tetraacrylate (PETEA), and trimethylolpropane triacrylate (TMPTA). The initiator is azobisisobutyronitrile (AIBN).

9. A method for preparing a gel-state ionic liquid electrolyte according to any one of claims 1-8, characterized in that, Includes the following steps: The ionic liquid matrix and lithium salt are mixed and stirred to form a homogeneous solution. A non-solvent diluent is added and mixed evenly. Then, a polymer precursor is added, along with an initiator, and the mixture is heated to allow the polymer precursor to polymerize in situ, forming a gel-like ionic liquid electrolyte.

10. A lithium-ion battery, characterized in that, The lithium-ion battery comprises a gel-state ionic liquid electrolyte as described in any one of claims 1-8, a positive electrode, a negative electrode, and a separator. Preferably, the active material of the positive electrode has an operating voltage of not less than 4.3V vs. Li / Li. + .

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