Electrolyte, preparation method and lithium secondary battery containing electrolyte

Abstract

The invention provides an electrolyte, which comprises a lithium salt and an organic solvent, and the organic solvent comprises a cyclic non-coordination solvent represented by the following formula (I) # imgabs0 # (I), in the formula (I), R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 are respectively and independently selected from a hydrogen atom, a chlorine atom, a bromine atom, a fluorine atom, a C1-C3 alkyl group, a C1-C3 alkoxy group, a fluorine-substituted C1-C3 alkyl group or a fluorine-substituted C1-C3 alkoxy group. The electrolyte provided by the invention can be applied to the lithium metal secondary battery, and can significantly improve the cycle stability and safety of the battery and prolong the cycle life of the battery; meanwhile, decomposition of the coordination type solvent can be effectively inhibited, and uniform deposition of metal lithium dendrites is realized, so that the stability of the electrolyte is improved; and moreover, the high-temperature storage gas production inhibition effect is obvious.

Description

Technical Field

[0001] The present application relates to the field of lithium secondary battery electrolytes, and in particular, to an electrolyte and a lithium secondary battery containing the electrolyte. Background Art

[0002] At present, the design of metal lithium electrolyte formula has basically abandoned the use of carbonate solvents, and the combination of coordinated ethers and non-coordinating diluents is currently the preferred combination. However, this electrolyte system can achieve good circulation in the early stage, but after hundreds of cycles, it begins to consume a lot of electrolyte, and finally the electrolyte dries up and causes a drop in the electrolyte.

[0003] For example, in the Chinese patent with application number "202311849057.4", an electrolyte and a lithium battery containing the electrolyte are disclosed, which specifically discloses: the electrolyte includes a fluorinated ether solvent, a co-solvent and a diluent, the fluorinated ether solvent has an ether main chain and -F, -CH2F, -CHF2 or -CF3 are introduced at both ends of the ether main chain, which can increase the Highest Occupied Molecular Orbital (HOMO) level and ultimately improve the oxidation capacity of the electrolyte; the co-solvent is a nitrile solvent, a sulfone solvent or a phenyl ether with a DN value of 10-13 kcal / mol; the diluent is an aromatic or halogenated compound with a DN value of less than 10 kcal / mol; the relative dielectric constants of the solvent, co-solvent and diluent are all >3.6. This patent adopts lithium salt, fluorinated ether solvent, nitrile solvent with DN value of 10-13kcal / mol as auxiliary solvent and aromatic or halogenated compound with DN value less than 10kcal / mol as diluent and limits the relative dielectric constant of the three reagents. At the same time, it can significantly improve the overall high temperature resistance and high voltage resistance of the electrolyte within a specific range. Even at a lithium salt concentration of less than or equal to 1M, the proportion of contact ion pairs (CIP) and aggregates (AGG) in the electrolyte is relatively high, which promotes the production of anion-derived SEI / CEI substances without affecting the dissolution of lithium salts, promoting the dissociation of solvated Li+, and greatly improving the cycle stability of the battery.

[0004] The solution structure of the electrolyte is closely related to the DN value of the introduced diluent. When the DN value of the introduced solvent is less than 10, a local high concentration electrolyte (LHCE) can be obtained, which is independent of the type of lithium salt and coordination solvent of the electrolyte. In the Chinese patent with application number "202311849057.4", the diluent used is an aromatic or halogenated compound with a DN value of less than 10kcal / mol. Therefore, this local high concentration electrolyte system can achieve good circulation in the early stage, but when it is circulated for hundreds of weeks, it will begin to consume a lot of electrolyte, and finally the electrolyte will dry up and cause a plunge; and the diluent fluorobenzene used in it is easy to cause the battery cell to produce gas during the circulation process of the lithium battery, thereby causing the battery cell to fail. Summary of the invention

[0005] The purpose of the embodiments of the present application is to provide an electrolyte, a preparation method and a lithium secondary battery containing the electrolyte, so as to solve the technical problem in the prior art that when the electrolyte is circulated for hundreds of cycles, a large amount of electrolyte begins to be consumed, and finally the electrolyte dries up and causes a water drop.

[0006] In a first aspect, the present application provides an electrolyte solution, comprising a lithium salt and an organic solvent, wherein the organic solvent comprises a cyclic non-coordinating solvent represented by the following formula (I): (I); In formula (I), R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 are each independently selected from a hydrogen atom, a chlorine atom, a bromine atom, a fluorine atom, a C1-C3 alkyl group, a C1-C3 alkoxy group, a fluorine-substituted C1-C3 alkyl group or a fluorine-substituted C1-C3 alkoxy group.

[0007] Furthermore, in formula (I), R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 are each independently selected from a hydrogen atom, a chlorine atom, or a fluorine atom.

[0008] Furthermore, the cyclic non-coordinating solvent is selected from at least one of Compound 1 to Compound 11: .

[0009] Furthermore, the organic solvent also includes a linear non-coordinating solvent, and the linear non-coordinating solvent includes 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, 1-(1,1,2,2-tetrafluoroethoxy)propane, 2-methyl-1-(1,1,2,2-tetrafluoroethoxy)propane, bis(2,2 Any one or more of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 2,2,2-trifluoroethyl-1,1,2,3,3,3-hexafluoropropyl ether, dichloromethane, hexafluoroisopropyl methyl ether, n-hexane, 2H,3H-decafluoropentane and methyl nonafluorobutyl ether; And / or, the organic solvent further comprises a coordination solvent, and the coordination solvent comprises any one or more of ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,2-diethoxyethane, acetonitrile, trimethyl phosphate, cyclopentane, tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, dimethyl sulfite, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, fluoroethylene carbonate and methyl propyl carbonate; And / or, the lithium salt includes any one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium hexafluoroaluminate, lithium tetrafluoroborate, lithium fluorosulfonate, lithium nitrate, lithium trifluoromethanesulfonate and lithium perchlorate; And / or, the electrolyte further includes an additive, and the additive includes any one or more of vinylene carbonate, 1,3-propane sultone, fluoroethylene carbonate, vinyl ethylene sulfate, vinyl sulfate, methylene methanedisulfonate, vinylene carbonate, tris(trimethylsilane) phosphate and tris(trimethylsilane) borate.

[0010] Further, the linear non-coordinating solvent includes any one or any two of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether; And / or, the coordination solvent includes any one or any two of ethylene glycol dimethyl ether and triethylene glycol dimethyl ether; And / or, the lithium salt includes any one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate and lithium tetrafluoroborate; And / or, the additive includes any one of vinylene carbonate and 1,3-propane sultone; Furthermore, based on the total mass of the electrolyte, the sum of the mass percentages of the linear non-coordinating solvent and the cyclic non-coordinating solvent is 35.5%-84.9%.

[0011] Furthermore, the molar ratio of the linear non-coordinating solvent to the cyclic non-coordinating solvent is (1-3): (1-2).

[0012] Further, based on the total mass of the electrolyte, the mass percentage of the coordination solvent is 10%-25%; And / or, based on the total mass of the electrolyte, the mass percentage of the lithium salt is 5%-35%; And / or, based on the total mass of the electrolyte, the mass percentage of the additive is 0.1%-4.5%.

[0013] In a second aspect, the present application provides a method for preparing an electrolyte, comprising the following steps: S1. Under the protection of inert gas, add a coordination solvent into a configuration container, then add a lithium salt into the configuration container and mix well; S2, adding a linear non-coordinating solvent and a cyclic non-coordinating solvent into a configuration container and mixing them evenly; S3. Add additives to the preparation container and mix evenly to obtain an electrolyte.

[0014] In a third aspect, the present application provides a lithium secondary battery, comprising the above-mentioned electrolyte; or, comprising the electrolyte prepared by the above-mentioned preparation method.

[0015] The lithium secondary battery in the present application can be a lithium metal negative electrode battery or a negative electrode-free lithium metal battery. Since it contains the electrolyte in the present application, under the synergistic effect of the linear non-coordinating solvent and the cyclic non-coordinating solvent, it can achieve better reversible deintercalation, inhibit the growth of lithium dendrites, reduce the deposition of lithium dendrites, and significantly improve the cycle stability, safety and cycle life of the battery; at the same time, it can effectively inhibit the decomposition of the coordination solvent, achieve uniform deposition of metallic lithium dendrites, thereby improving the stability of the electrolyte; and, the high-temperature storage gas production inhibition effect is obvious, the vapor pressure is lower at the same temperature, and the operating temperature range of the lithium metal battery is broadened.

[0016] Beneficial effects of the embodiments of the present application: (1) The electrolyte in the present application can be applied to lithium secondary batteries, which can be lithium metal anode batteries or anode-free lithium metal batteries. The coordination solvent achieves the dissociation of lithium salts through its own high polarity, but the viscosity of the electrolyte is too high due to the high concentration, which is not conducive to ion movement. The introduced linear non-coordinating solvent can be used to adjust the overall viscosity and solvation structure of the electrolyte to form a solvation model of more anion and cation aggregates, but the linear non-coordinating solvent has limited control over the solvation structure and cannot suppress the chemical reaction activity of lithium metal and the coordination solvent. Through the introduction of cyclic non-coordinating solvents, a specific constrained conformation is exhibited, and the electron cloud density around the oxygen atom is low, which minimizes the coordination with lithium ions. Therefore, under the synergistic effect of cyclic non-coordinating solvents and linear non-coordinating solvents, anion-based interface regulation can be achieved, so that the interface is rich in inorganic components such as LiF and Li3N, the ion diffusion kinetics are improved, and better reversible deintercalation can be achieved, the growth of lithium dendrites is inhibited, and the deposition of lithium dendrites is reduced. Its application can significantly improve the cycle stability, safety and cycle life of the battery.

[0017] (2) The electrolyte in the present application cannot achieve good chemical and electrochemical stability due to the strong reducing property of lithium alkali metal. However, the use of linear non-coordinating solvents and cyclic non-coordinating solvents can achieve better reaction inertness, reduce the decomposition of the highly polar coordinating solvent in the first solvation sheath, effectively inhibit the decomposition of the coordinating solvent, and achieve uniform deposition of metallic lithium dendrites, thereby improving the stability of the electrolyte.

[0018] (3) Compared with the fluorobenzene family of similar cyclic diluents, which are prone to cause gas production in the battery cell during the cycle of the lithium battery, thereby causing the battery cell to fail; the electrolyte in the present application, which uses a cyclic non-coordinating solvent, has a significant effect of inhibiting gas production during high-temperature storage, and can inhibit gas production during the cycle of the lithium secondary battery, which can significantly improve the battery's cycle stability, safety and cycle life; and, at the same temperature, the vapor pressure is lower, which broadens the high-temperature temperature range for the use of lithium metal batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 Schematic diagram of the cycle capacity retention rate of lithium secondary batteries in Example 1, Example 2 and Comparative Example 1. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0022] 1. Embodiment: Embodiment 1: 1.1. An electrolyte comprising: Lithium salt, using lithium bis(fluorosulfonyl)imide (LiFSI), the mass percentage of which is 20%; The additive is vinylene carbonate, and its mass percentage is 2%; The coordination solvent is ethylene glycol dimethyl ether (DME), with a mass percentage of 23%. A linear non-coordinating solvent using 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE); The cyclic non-coordinating solvent is a compound 2 of the following formula (1); (1) The sum of the mass percentages of the linear non-coordinating solvent and the cyclic non-coordinating solvent is 55%, and the molar ratio of the linear non-coordinating solvent to the cyclic non-coordinating solvent is 1:1.

[0023] 1.2: Preparation method: The steps include: S1. In a glove box filled with argon, first add lithium salt to the weighed coordination solvent and mix well; S2, then add a linear non-coordinating solvent and a cyclic non-coordinating solvent and mix them evenly; S3. Finally, add additives and mix well to prepare a clear and transparent electrolyte.

[0024] Embodiment 2: The electrolyte in this embodiment is different from that in Embodiment 1 in that the lithium salt used is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and the rest is the same as in Embodiment 1.

[0025] Embodiment 3: The electrolyte in this embodiment is different from that in Embodiment 1 in that the cyclic non-coordinating solvent used is compound 1 of the following formula (2), and the rest is the same as in Embodiment 1.

[0026] (2) Embodiment 4: The electrolyte in this embodiment is different from that in Embodiment 1 in that the cyclic non-coordinating solvent used is compound 3 of the following formula (3), and the rest is the same as in Embodiment 1.

[0027] (3) Embodiment 5: The electrolyte in this embodiment is different from that in Embodiment 1 in that the cyclic non-coordinating solvent used is compound 4 of the following formula (4), and the rest is the same as in Embodiment 1.

[0028] (4) Embodiment 6: The electrolyte in this embodiment is different from that in Embodiment 1 in that the cyclic non-coordinating solvent used is compound 5 of the following formula (5), and the rest is the same as in Embodiment 1.

[0029] (5) Embodiment 7: The electrolyte in this embodiment is different from that in Embodiment 1 in that the cyclic non-coordinating solvent used is compound 6 of the following formula (6), and the rest is the same as in Embodiment 1.

[0030] (6) Embodiment 8: The electrolyte in this embodiment is different from that in Embodiment 1 in that the cyclic non-coordinating solvent used is compound 7 of the following formula (7), and the rest is the same as in Embodiment 1.

[0031] (7) Embodiment 9: The electrolyte in this embodiment is different from that in Embodiment 1 in that the cyclic non-coordinating solvent used is compound 8 of the following formula (8), and the rest is the same as in Embodiment 1.

[0032] (8) Embodiment 10: The electrolyte in this embodiment is different from that in Embodiment 1 in that the cyclic non-coordinating solvent used is compound 9 of the following formula (9), and the rest is the same as in Embodiment 1.

[0033] (9) Embodiment 11: The electrolyte in this embodiment is different from that in Embodiment 1 in that the cyclic non-coordinating solvent used is compound 10 of the following formula (10), and the rest is the same as in Embodiment 1.

[0034] (10) Embodiment 12: The electrolyte in this embodiment is different from that in Embodiment 1 in that the cyclic non-coordinating solvent used is compound 11 of the following formula (11), and the rest is the same as in Embodiment 1.

[0035] (11) Embodiment 13: The electrolyte in this embodiment is different from that in Embodiment 1 in that: the linear non-coordinating solvent used is 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether; the cyclic non-coordinating solvent used is compound 3 of the following formula (12); the rest is the same as in Embodiment 1.

[0036] (12) Embodiment 14: The electrolyte in this embodiment is different from that in Embodiment 1 in that: the coordination solvent used is triethylene glycol dimethyl ether; the cyclic non-coordinating solvent used is compound 6 of the following formula (13); and the rest is the same as in Embodiment 1.

[0037] (13) Embodiment 15: 15.1. An electrolyte comprising: Lithium salt, using lithium hexafluorophosphate, the mass percentage of which is 25%; The additive is 1,3-propane sultone, and its mass percentage is 1%; The coordination solvent is 1,2-diethoxyethane, with a mass percentage of 15%. A linear non-coordinating solvent, 1-(1,1,2,2-tetrafluoroethoxy)propane, is used; The cyclic non-coordinating solvent is a compound 1 of the following formula (14); (14) The sum of the mass percentages of the linear non-coordinating solvent and the cyclic non-coordinating solvent is 59%, and the molar ratio of the linear non-coordinating solvent to the cyclic non-coordinating solvent is 2:1.

[0038] 15.2. Preparation method is the same as in Example 1.

[0039] Embodiment 16: 16.1. An electrolyte comprising: Lithium salt, lithium tetrafluoroborate is used, and its mass percentage is 15%; The additive is fluoroethylene carbonate, and its mass percentage is 1.5%; The coordination solvent is 1,2-diethoxyethane, with a mass percentage of 13%. A linear non-coordinating solvent is 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether; The cyclic non-coordinating solvent is a compound 2 of the following formula (15); (15) The sum of the mass percentages of the linear non-coordinating solvent and the cyclic non-coordinating solvent is 70%, and the molar ratio of the linear non-coordinating solvent to the cyclic non-coordinating solvent is 3:1.

[0040] 16.2. Preparation method is the same as in Example 1.

[0041] Embodiment 17: 17.1. An electrolyte comprising: Lithium salt, using lithium hexafluorophosphate, the mass percentage of which is 25%; The additive is methylene methane disulfonate, and its mass percentage is 3%; The coordination solvent is tetraethylene glycol dimethyl ether, with a mass percentage of 10%. A linear non-coordinating solvent is 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether; The cyclic non-coordinating solvent is a compound 4 of the following formula (16); (16) The sum of the mass percentages of the linear non-coordinating solvent and the cyclic non-coordinating solvent is 62%, and the molar ratio of the linear non-coordinating solvent to the cyclic non-coordinating solvent is 3:2.

[0042] 17.2. Preparation method is the same as in Example 1.

[0043] 2. Comparative ratio: Comparative Example 1: The electrolyte in this comparative example is different from that in Example 1 in that no cyclic non-coordinating solvent is used, and the mass percentage of the linear non-coordinating solvent is 55%. The rest is the same as in Example 1.

[0044] Comparative Example 2: The electrolyte in this comparative example is different from that in Example 1 in that the cyclic non-coordinating solvent used is fluorobenzene; the rest is the same as in Example 1.

[0045] Comparative Example 3: The electrolyte in this comparative example is different from that in Example 1 in that the cyclic non-coordinating solvent used is m-fluorotoluene; the rest is the same as in Example 1.

[0046] 3. Experimental example: 1. The electrolytes in Examples 1-17 and Comparative Examples 1-3 were respectively prepared into lithium secondary batteries, and subjected to a 25° C. cycle performance test, a 55° C. cycle performance test, and a high-temperature storage gas generation test.

[0047] 1.1. The preparation method of a lithium secondary battery comprises the following steps: (1) Preparation of positive electrode: Dissolve polyvinylidene fluoride (PVDF) evenly in N-methylpyrrolidone (NMP). Then add the conductive agent Super P and mix thoroughly. Then, the positive electrode active material LiNi0.8Co0.1Mn0.1O2 powder is gradually added (wherein, the mass ratio of LiNi0.8Co0.1Mn0.1O2 powder, PVDF and conductive agent Super P is 97.4:1.3:1.3, to obtain positive electrode slurry (the solid content of the positive electrode slurry is 65.1%). The positive electrode slurry is coated on the current collector, and then dried, rolled and slit to obtain positive electrode sheets that can be directly stacked.

[0048] (2) Battery cell production: The positive and negative electrodes (lithium electrodes) after stripping are stacked on a stacking machine. The separator is a three-layer material of PP / PE / PP and assembled into a soft-pack battery cell.

[0049] (3) Electrolyte: The electrolytes in Examples 1-17 and Comparative Examples 1-3 were used.

[0050] (4) Liquid injection, formation and aging: After the battery cell is dried at high temperature, the electrolyte of the embodiment and the comparative example is injected into the soft-pack battery cell. After the electrolyte is injected, the lithium battery is packaged for the first time, and the surface is cleaned to complete the preliminary work, and then placed at room temperature for one day. The formation is carried out by a step-by-step formation method. The first step is a formation current of 0.05C, and a constant current is charged for 2h. The second step is a formation current of 0.1C, and a constant current is charged until the voltage reaches 3.85V. After formation, it is aged at 50°C for one day, cooled to room temperature, and finally sealed to obtain a lithium secondary battery.

[0051] 1.2 Test method: (1) 25°C cycle performance test: The batteries prepared in the examples and comparative examples were charged to 4.2V at 0.2C constant current and constant voltage at 25°C, and then discharged to 3.0V at 0.5C constant current. This was considered one cycle, and the number of cycles when the battery reached 80% SOH was recorded.

[0052] (2) 55°C cycle performance test: The batteries prepared in the examples and comparative examples were charged to 4.2V at 0.2C constant current and constant voltage at 25°C, and then discharged to 3.0V at 0.5C constant current. This was considered one cycle, and the number of cycles when the battery reached 80% SOH was recorded.

[0053] (3) High-temperature storage gas generation test: The batteries prepared in the examples and comparative examples were charged to 4.2 V at 0.2 C constant current and constant voltage at 25 ° C, and the cell capacity Qa (in Ah) was recorded. The cell volume V1 (in mL) was tested by the water displacement method. The cells were then placed in a 70 ° C forced air oven for 21 days, and then taken out and restored to room temperature before testing the cell volume V2 (in mL). The formula for calculating gas production is: (V2-V1) / Qa.

[0054] 1.3. Test results are shown in Table 1 below: Table 1 Test results

[0055] From Table 1 we can see that: (1) Through comparative example 1 and examples 1-17, the use of a cyclic non-coordinating solvent in combination with a linear non-coordinating solvent can adjust the solvation structure, so that the coordinating solvent decomposes less in the later stage of the cycle, significantly improving the room temperature and high temperature capacity retention rate of the soft-pack battery cell, significantly improving the cycle stability and cycle life of the battery, and improving the high temperature cycle performance of the battery.

[0056] (2) It is not difficult to find from Comparative Examples 2, 3 and Examples 1-17 that the fluorobenzenes, which are also cyclic non-coordinating solvents, are far less effective than fluorotetrahydropyran non-coordinating solvents in improving circulation. The reason is that the combination of the cyclic non-coordinating solvents and the linear non-coordinating solvents in Examples 1-17 of the present application has a stronger inertness to lithium metal, can reduce the decomposition of the highly polar coordinating solvent in the first solvation sheath, can effectively inhibit the decomposition of the coordinating solvent, achieve uniform deposition of metallic lithium dendrites, and improve the stability of the electrolyte, thereby being more adaptable to the irreversible consumption of the electrolyte caused by the strong reduction activity of the negative electrode.

[0057] (3) Comparing the high-temperature storage gas production of Comparative Examples 1-3 and Examples 1-17, Comparative Example 1 only uses a straight-chain non-coordinating solvent; Comparative Example 2 uses fluorobenzene in combination with a straight-chain non-coordinating solvent, and Comparative Example 3 uses m-fluorotoluene in combination with a straight-chain non-coordinating solvent. In Examples 1-17, the high temperature storage gas production of Examples 5 and 10 is the lowest, 0.9 mL / Ah; the high temperature storage gas production of Example 6 is the highest, 2.7 mL / Ah; compared with Examples 5 and 10, the high temperature storage gas production of Comparative Example 1 is 3.8 times that of Examples 5 and 10, the high temperature storage gas production of Comparative Example 2 is 6.6 times that of Examples 5 and 10, and the high temperature storage gas production of Comparative Example 3 is 10.2 times that of Examples 5 and 10; compared with Example 6, the high temperature storage gas production of Comparative Example 1 is 1.3 times that of Example 6, the high temperature storage gas production of Comparative Example 2 is 2.2 times that of Example 6, and the high temperature storage gas production of Comparative Example 3 is 3.4 times that of Examples 5 and 10. It can be seen from the experimental results that in Examples 1-17 of the present application, the high temperature storage gas production inhibition effect of the cyclic non-coordinating solvent used is obvious, and it can inhibit gas production during the cycle process of lithium secondary batteries, which can significantly improve the cycle stability, safety and cycle life of the battery.

[0058] The above description is only an embodiment of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An electrolyte comprising a lithium salt and an organic solvent, characterized in that: The organic solvent includes a cyclic non-coordinating solvent represented by the following formula (I): （Ⅰ）； In formula (I), R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 are each independently selected from a hydrogen atom, a chlorine atom, a bromine atom, a fluorine atom, a C1-C3 alkyl group, a C1-C3 alkoxy group, a fluorine-substituted C1-C3 alkyl group or a fluorine-substituted C1-C3 alkoxy group.

2. The electrolyte according to claim 1, characterized in that In formula (I), R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 are each independently selected from a hydrogen atom, a chlorine atom or a fluorine atom.

3. The electrolyte according to claim 1, characterized in that The cyclic non-coordinating solvent is selected from at least one of the following compounds 1 to 11: 。 4. The electrolyte according to claim 1, characterized in that The organic solvent also includes a linear non-coordinating solvent, and the linear non-coordinating solvent includes any one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, 1-(1,1,2,2-tetrafluoroethoxy)propane, 2-methyl-1-(1,1,2,2-tetrafluoroethoxy)propane, bis(2,2,2-trifluoroethyl) ether, tris(trifluoroethoxy)methane, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 2,2,2-trifluoroethyl-1,1,2,3,3,3-hexafluoropropyl ether, dichloromethane, hexafluoroisopropyl methyl ether, n-hexane, 2H,3H-decafluoropentane and methyl nonafluorobutyl ether; And / or, the organic solvent further comprises a coordination solvent, and the coordination solvent comprises any one or more of ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,2-diethoxyethane, acetonitrile, trimethyl phosphate, cyclopentane, tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, dimethyl sulfite, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, fluoroethylene carbonate and methyl propyl carbonate; And / or, the lithium salt includes any one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium hexafluoroaluminate, lithium tetrafluoroborate, lithium fluorosulfonate, lithium nitrate, lithium trifluoromethanesulfonate and lithium perchlorate; And / or, the electrolyte further includes an additive, and the additive includes any one or more of vinylene carbonate, 1,3-propane sultone, fluoroethylene carbonate, vinyl ethylene sulfate, vinyl sulfate, methylene methanedisulfonate, vinylene carbonate, tris(trimethylsilane) phosphate and tris(trimethylsilane) borate.

5. The electrolyte according to claim 4, characterized in that The linear non-coordinating solvent includes any one or any two of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether; And / or, the coordination solvent includes any one or any two of ethylene glycol dimethyl ether and triethylene glycol dimethyl ether; And / or, the lithium salt includes any one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate and lithium tetrafluoroborate; And / or, the additive includes any one of vinylene carbonate and 1,3-propane sultone.

6. The electrolyte according to claim 4, characterized in that Based on the total mass of the electrolyte, the sum of the mass percentages of the linear non-coordinating solvent and the cyclic non-coordinating solvent is 35.5%-84.9%.

7. The electrolyte according to claim 6, characterized in that The molar ratio of the linear non-coordinating solvent to the cyclic non-coordinating solvent is (1-3): (1-2).

8. The electrolyte according to claim 4, characterized in that Based on the total mass of the electrolyte, the mass percentage of the coordination solvent is 10%-25%; And / or, based on the total mass of the electrolyte, the mass percentage of the lithium salt is 5%-35%; And / or, based on the total mass of the electrolyte, the mass percentage of the additive is 0.1%-4.5%.

9. The method for preparing an electrolyte according to any one of claims 1 to 8, characterized in that: The steps include: S1. Under the protection of inert gas, add a coordination solvent into a configuration container, then add a lithium salt into the configuration container and mix well; S2, adding a linear non-coordinating solvent and a cyclic non-coordinating solvent into a configuration container and mixing them evenly; S3. Add additives to the preparation container and mix evenly to obtain an electrolyte.

10. A lithium secondary battery, characterized in that: An electrolyte comprising any one of claims 1 to 8; or an electrolyte prepared by the preparation method of claim 9.

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