Composition for local high-concentration electrolyte, local high-concentration electrolyte, preparation method and application of local high-concentration electrolyte, and lithium secondary battery

Abstract

The invention relates to the technical field of lithium secondary batteries, and discloses a local high-concentration electrolyte composition, a local high-concentration electrolyte, a preparation method and application of the local high-concentration electrolyte, and a lithium secondary battery. The composition contains a lithium salt, a solvent, a diluent and 2-(diphenylphosphino) ethylamine tetrafluoroborate, the molar content ratio of the lithium salt to the solvent to the diluent is 1: (1-6): (4-8); on the basis of the total mass of the composition, the content of the 2-(diphenylphosphino) ethylamine tetrafluoroborate is 0.1 to 0.5 weight percent. The local high-concentration electrolyte provided by the invention can inhibit the anion loss in the cycle process, improve the coulombic efficiency of the battery and prolong the cycle life of the battery; and a low-impedance electrode / electrolyte interface can be formed, battery polarization is reduced, and the energy efficiency of the battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium secondary batteries, and in particular to a local high-concentration electrolyte composition, a local high-concentration electrolyte, a preparation method and application thereof, and a lithium secondary battery. Background Art

[0002] As an important component of electrochemical energy storage systems, lithium secondary batteries play a vital role in new energy systems. Lithium secondary batteries typically use commercial carbonate electrolytes, which are prone to combustion and explosion in extreme conditions and have poor low-temperature performance. To expand the functions of lithium secondary batteries (such as wide temperature range and flame retardancy), solvents such as carboxylates and phosphates are usually required. However, these solvents have poor compatibility with the negative electrode and can easily lead to severe degradation of battery performance.

[0003] Improving the stability of the electrolyte by designing a local high-concentration electrolyte is an effective means. For example, CN114361587A discloses a local high-concentration electrolyte additive and application for lithium metal secondary batteries. The additive is an aromatic compound composed of a benzene ring and a substituent group, at least two hydrogen atoms on the benzene ring are replaced by fluorine atoms, and the remaining hydrogen atoms are retained or replaced by alkyl, halogenated alkyl, or halogen atoms; the additive is used to be added to the local high-concentration electrolyte of the lithium metal secondary battery, and can be highly miscible with the local high-concentration electrolyte without changing the original solvation structure of the local high-concentration electrolyte; it can also weaken the interaction between lithium ions and organic solvents and anions, thereby improving the ionic conductivity of the local high-concentration electrolyte. When the additive in this scheme is added to the existing local high-concentration electrolyte, it not only has excellent thermal stability, but can also form a component that stabilizes the interface between the positive and negative electrodes of the battery, greatly improving the coulombic efficiency and cycle life of the battery under high voltage conditions.

[0004] CN118472391A discloses a locally concentrated electrolyte and lithium metal battery containing a phenyl diluent. The locally concentrated electrolyte comprises a solvent, a solute, and a phenyl fluorine-free diluent. The solvent is ethylene glycol dimethyl ether, the solute is an inorganic or organic lithium salt, and the phenyl fluorine-free diluent is benzene or a benzene homologue. The electrolyte provided by this solution has a stable solvation structure and can induce a stable solid electrolyte interface film on the lithium metal negative electrode, helping to improve the reversibility of lithium deposition and dissolution. At the same time, it can induce a thin and dense positive electrode and electrolyte interface film on the high-nickel positive electrode side, effectively avoiding the risk of electrolyte decomposition under high pressure and significantly improving the cycle performance of the lithium metal battery.

[0005] The above technical solutions all improve the stability of the electrolyte through local high-concentration design, and are even compatible with lithium metal negative electrodes with extremely high reaction activity. However, the above solutions still have problems such as rapid lithium salt anion loss, low coulombic efficiency, and insufficient cycle life. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems of fast lithium salt anion loss, low coulombic efficiency, insufficient cycle life, etc. existing in the local high-concentration electrolyte of the prior art.

[0007] In order to achieve the above object, the first aspect of the present invention provides a composition for local high-concentration electrolyte, which contains a lithium salt, a solvent, a diluent and 2-(diphenylphosphino)ethylamine tetrafluoroborate;

[0008] The molar ratio of the lithium salt, the solvent and the diluent is 1:1-6:4-8;

[0009] Based on the total mass of the composition, the content of the 2-(diphenylphosphino)ethylamine tetrafluoroborate is 0.1-0.5 wt %.

[0010] The second aspect of the present invention provides a method for preparing a local high-concentration electrolyte, which is carried out using the composition for the local high-concentration electrolyte described in the first aspect, and comprises: mixing a mixture containing the composition for the local high-concentration electrolyte to obtain the local high-concentration electrolyte.

[0011] The third aspect of the present invention provides a local high-concentration electrolyte prepared by the method described in the second aspect.

[0012] The fourth aspect of the present invention provides use of the local high-concentration electrolyte described in the third aspect in a lithium secondary battery.

[0013] A fifth aspect of the present invention provides a lithium secondary battery, comprising: a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator; the electrolyte is the local high-concentration electrolyte described in the third aspect.

[0014] Compared with the prior art, the present invention has at least the following beneficial effects:

[0015] (1) The local high-concentration electrolyte provided by the present invention can suppress anion loss during the cycle and improve the battery coulombic efficiency and cycle life;

[0016] (2) The local high-concentration electrolyte provided by the present invention can form a low-impedance electrode / electrolyte interface, reduce battery polarization, and improve the energy efficiency of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 1 is a graph showing the cycling performance of lithium-ion batteries using the electrolytes obtained in Example 1 and the comparative example provided by the present invention;

[0018] Figure 2 This is a coulombic efficiency test chart of the electrolyte obtained in Example 1 and the comparative example provided by the present invention when applied to a lithium-copper half-cell. DETAILED DESCRIPTION

[0019] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0020] As mentioned above, the first aspect of the present invention provides a composition for local high-concentration electrolyte, which contains a lithium salt, a solvent, a diluent and 2-(diphenylphosphino)ethylamine tetrafluoroborate;

[0021] The molar ratio of the lithium salt, the solvent and the diluent is 1:1-6:4-8;

[0022] Based on the total mass of the composition, the content of the 2-(diphenylphosphino)ethylamine tetrafluoroborate is 0.1-0.5 wt %.

[0023] The composition for local high-concentration electrolyte provided by the present invention can induce anions to remain in the solvation layer of lithium ions in the electrolyte system, thereby forming a low-impedance electrode / electrolyte interface layer rich in inorganic substances, thereby suppressing the continuous loss of anions during the cycle.

[0024] It should be noted that the localized high-concentration electrolyte described in this invention, in the art, refers to an electrolyte in which the salt concentration is high in certain localized areas, while the overall salt concentration of the electrolyte is relatively low. This design modifies the physicochemical properties of the electrolyte by adding a non-solvating diluent. Typically, the localized high-concentration electrolyte consists of a lithium salt, a solvent, and a non-solvating diluent.

[0025] Preferably, the content of 2-(diphenylphosphino)ethylamine tetrafluoroborate is 0.2-0.3 wt % based on the total mass of the composition. The inventors have found that under this preferred embodiment, the electrolyte provided by the present invention has better cycle performance and coulombic efficiency after application in batteries.

[0026] Preferably, the molar ratio of the lithium salt, the solvent and the diluent is 1: 2-4: 5-7. The inventors have found that under this preferred embodiment, the electrolyte provided by the present invention has better cycle performance and coulombic efficiency after application in batteries.

[0027] Preferably, the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium nitrate, and lithium difluoroborate.

[0028] Preferably, the solvent is selected from at least one of triethyl phosphate, trimethyl phosphate, dimethyl sulfoxide, sulfolane, propylene carbonate, methyl acetate, propyl acetate, and butyl acetate.

[0029] Preferably, the diluent is selected from at least one of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, trifluoromethoxybenzene, fluorobenzene, p-fluorotoluene, 1,3,5-trifluorobenzene, and m-fluorotoluene.

[0030] More preferably, the lithium salt is a combination of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide in a molar ratio of 1:0.8-1.2. The inventors have found that under this preferred embodiment, the electrolyte provided by the present invention has better cycle performance and coulombic efficiency after application in batteries.

[0031] More preferably, the solvent is triethyl phosphate.

[0032] Particularly preferably, the diluent is trifluoromethoxybenzene.

[0033] As mentioned above, the second aspect of the present invention provides a method for preparing a local high-concentration electrolyte, which is performed using the composition for the local high-concentration electrolyte described in the first aspect, and comprises: mixing a mixture containing the composition for the local high-concentration electrolyte to obtain the local high-concentration electrolyte.

[0034] Preferably, the mixing conditions include: temperature of 20-40° C. and time of 2-10 h.

[0035] As mentioned above, the third aspect of the present invention provides a local high-concentration electrolyte prepared by the method described in the second aspect.

[0036] As mentioned above, the fourth aspect of the present invention provides the use of the local high-concentration electrolyte described in the third aspect in a lithium secondary battery.

[0037] As mentioned above, the fifth aspect of the present invention provides a lithium secondary battery, which includes: a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator; the electrolyte is the local high-concentration electrolyte described in the third aspect.

[0038] It should be noted that the present invention has no special requirements for the assembly process of the above-mentioned lithium secondary battery, and it can be assembled using methods known in the art. The present invention will not describe them one by one here, and those skilled in the art should not understand this as a limitation of the present invention.

[0039] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, all raw materials used are commercially available and all solvents used are of analytical grade.

[0040] raw material:

[0041] 2-(Diphenylphosphino)ethylamine tetrafluoroborate: CAS No. 1222630-32-1, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0042] Lithium hexafluorophosphate: CAS number 21324-40-3, purchased from Suzhou Duoduo Reagent Co., Ltd.

[0043] Lithium difluorooxalatoborate: CAS number 409071-16-5, purchased from Suzhou Duoduo Reagent Co., Ltd.

[0044] Lithium nitrate: CAS number 7790-69-4, purchased from Suzhou Duoduo Reagent Co., Ltd.

[0045] Lithium bis(fluorosulfonyl)imide: CAS number 171611-11-3, purchased from Suzhou Duoduo Reagent Co., Ltd.

[0046] Ethylene carbonate: CAS number 96-49-1, purchased from Suzhou Duoduo Reagent Co., Ltd.

[0047] Triethyl phosphate: CAS number 78-40-0, purchased from Suzhou Duoduo Reagent Co., Ltd.

[0048] Trimethyl phosphate: CAS number 512-56-1, purchased from Suzhou Duoduo Reagent Co., Ltd.

[0049] Dimethyl sulfoxide: CAS number 67-68-5, purchased from Suzhou Duoduo Reagent Co., Ltd.

[0050] Propylene carbonate: CAS number 108-32-7, purchased from Suzhou Duoduo Reagent Co., Ltd.

[0051] Methyl acetate: CAS number 79-20-9, purchased from Suzhou Duoduo Reagent Co., Ltd.

[0052] Propyl acetate: CAS number 109-60-4, purchased from Suzhou Duoduo Reagent Co., Ltd.

[0053] Butyl acetate: CAS number 123-86-4, purchased from Suzhou Duoduo Reagent Co., Ltd.

[0054] Polyolefin separator: Celgard 2400 separator, 25 μm thick, single-layer PP material, 41% porosity, purchased from Celgard Company, USA;

[0055] Commercial lithium iron phosphate cathode: surface density of 13.5 mg / cm 2 , active material accounts for 95.3wt%, purchased from Shenzhen Kejing Zhida Technology Co., Ltd.;

[0056] Commercial single-particle graphite anode: surface density 6.3 mg / cm 2 , active material accounts for 95.3wt% and is purchased from Hunan Rongli New Material Technology Co., Ltd.

[0057] Example 1

[0058] This example is used to illustrate that the local high-concentration electrolyte provided by the present invention is prepared using the following steps:

[0059] In an argon-protected glove box (H2O and O2 contents are both less than 0.1 ppm), 0.5 mol of lithium hexafluorophosphate, 0.5 mol of lithium bis(fluorosulfonyl)imide, 2 mol of triethyl phosphate, 6 mol of trifluoromethoxybenzene and 2-(diphenylphosphino)ethylamine tetrafluoroborate were stirred at 25°C for 6 h (stirring speed of 600 rpm) to obtain the locally high-concentration electrolyte S1;

[0060] Based on the total weight of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, triethyl phosphate, trifluoromethoxybenzene and 2-(diphenylphosphino)ethylamine tetrafluoroborate, the added amount of the 2-(diphenylphosphino)ethylamine tetrafluoroborate is 0.3 wt %.

[0061] Example 2

[0062] In an argon-protected glove box (H2O and O2 contents are both less than 0.1 ppm), 0.8 mol of lithium hexafluorophosphate, 0.2 mol of lithium bis(fluorosulfonyl)imide, 3 mol of triethyl phosphate, 5 mol of trifluoromethoxybenzene and 2-(diphenylphosphino)ethylamine tetrafluoroborate were stirred at 25°C for 8 h (stirring speed is 600 rpm) to obtain the local high-concentration electrolyte S2;

[0063] Based on the total weight of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, triethyl phosphate, trifluoromethoxybenzene and 2-(diphenylphosphino)ethylamine tetrafluoroborate, the added amount of the 2-(diphenylphosphino)ethylamine tetrafluoroborate is 0.25 wt %.

[0064] Example 3

[0065] This example is carried out using a process similar to that of Example 1, except that, in this example, the amount of 2-(diphenylphosphino)ethylamine tetrafluoroborate added is 0.5 wt %, based on the total weight of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, triethyl phosphate, trifluoromethoxybenzene, and 2-(diphenylphosphino)ethylamine tetrafluoroborate.

[0066] The rest are the same as in Example 1.

[0067] A locally high-concentration electrolyte S3 is prepared.

[0068] Example 4

[0069] This example is carried out using a process similar to that of Example 1, except that, in this example, the amount of 2-(diphenylphosphino)ethylamine tetrafluoroborate added is 0.1 wt %, based on the total weight of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, triethyl phosphate, trifluoromethoxybenzene, and 2-(diphenylphosphino)ethylamine tetrafluoroborate.

[0070] The rest are the same as in Example 1.

[0071] A locally high-concentration electrolyte S4 is prepared.

[0072] Example 5

[0073] This example was carried out using a process similar to that of Example 1, except that, in this example, the amount of trifluoromethoxybenzene used was 8 mol, and the amount of 2-(diphenylphosphino)ethylamine tetrafluoroborate added was 0.3 wt %, based on the total mass of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, triethyl phosphate, trifluoromethoxybenzene, and 2-(diphenylphosphino)ethylamine tetrafluoroborate.

[0074] The rest are the same as in Example 1.

[0075] A locally high-concentration electrolyte S5 is prepared.

[0076] Example 6

[0077] In an argon-protected glove box (H2O and O2 contents are both less than 0.1 ppm), 0.5 mol of lithium hexafluorophosphate, 0.5 mol of lithium bis(fluorosulfonyl)imide, 2 mol of tripropyl phosphate, 8 mol of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and 2-(diphenylphosphino)ethylamine tetrafluoroborate were stirred at 25°C for 6 h (stirring speed of 800 rpm) to obtain the locally high-concentration electrolyte S6;

[0078] Based on the total weight of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, tripropyl phosphate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and 2-(diphenylphosphino)ethylamine tetrafluoroborate, the added amount of the 2-(diphenylphosphino)ethylamine tetrafluoroborate is 0.25 wt%.

[0079] Example 7

[0080] This example is carried out using a process similar to that of Example 1, except that the molar amount of triethyl phosphate used in this example is 6 mol.

[0081] The rest are the same as in Example 1.

[0082] A locally high-concentration electrolyte S7 was prepared.

[0083] Comparative Example 1

[0084] This comparative example was carried out using a process similar to that of Example 1, except that 2-(diphenylphosphino)ethylamine tetrafluoroborate was not added in this comparative example.

[0085] The rest are the same as in Example 1.

[0086] The electrolyte DS1 was prepared.

[0087] Comparative Example 2

[0088] This comparative example was carried out using a process similar to that of Example 1, except that, in this comparative example, the amount of 2-(diphenylphosphino)ethylamine tetrafluoroborate added was 1 wt %, based on the total mass of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, triethyl phosphate, trifluoromethoxybenzene and 2-(diphenylphosphino)ethylamine tetrafluoroborate.

[0089] The rest are the same as in Example 1.

[0090] A local high-concentration electrolyte DS2 was prepared.

[0091] Comparative Example 3

[0092] This comparative example was carried out using a process similar to that of Example 1, except that, in this comparative example, 3-(dimethylamino)phenylbis(4-(dimethylamino)phenyl)phosphite (CAS No. 41445-40-3, purchased from MacLean Reagent Co., Ltd.) of equal mass was used to replace the 2-(diphenylphosphino)ethylamine tetrafluoroborate in Example 1.

[0093] The rest are the same as in Example 1.

[0094] A locally high-concentration electrolyte DS3 was prepared.

[0095] Comparative Example 4

[0096] This comparative example was carried out using a process similar to that of Example 1, except that, in this comparative example, guanidine tetrafluoroborate (CAS No. 36595-00-3, purchased from MacLean Reagent Co., Ltd.) of equal quality was used to replace 2-(diphenylphosphino)ethylamine tetrafluoroborate in Example 1.

[0097] The rest are the same as in Example 1.

[0098] A locally high-concentration electrolyte DS4 was prepared.

[0099] Test Case

[0100] A commercial lithium iron phosphate positive electrode, a commercial single-particle graphite negative electrode, a commercial separator and the electrolyte prepared in the above example are assembled into a battery to obtain a lithium-ion battery.

[0101] Lithium metal, commercial copper foil, commercial separator and the electrolyte prepared in the above example are assembled into a battery to obtain a lithium-copper half-cell.

[0102] Conducting a cycle performance test on the lithium-ion battery prepared above, and a coulombic efficiency test on the lithium-copper half-cell;

[0103] Cycling performance test: A blue electric charge and discharge tester was used for the cycling test, specifically: (1) charging and discharging three times at a rate of 0.1C in the voltage range of 2.5-3.65V to fully activate the battery; (2) charging and discharging cycle test was performed at a rate of 0.5C in the voltage range of 2.5-3.65V, and the discharge capacity retention rate after 100 cycles was recorded, where the discharge capacity retention rate = 100th cycle discharge capacity / 0.5C first cycle discharge capacity * 100%. The test results are shown in Table 1.

[0104] Coulomb efficiency test: A blue electric charge and discharge tester was used for cycle test, specifically: (1) passing 0.5mAhcm -2 Activation was performed by constant current charge and discharge for 3 weeks, with the discharge cutoff condition being when the capacity reached 1 mAh cm -2 The charging cutoff condition is that the voltage reaches 1.0 V; (2) the current density is increased to 1 mA cm -2 , perform 100 charge and discharge tests, and record the average coulombic efficiency of 100 cycles, where the nth cycle coulombic efficiency = nth cycle charge capacity / nth cycle discharge capacity*100%. The test results are shown in Table 2.

[0105] Table 1

[0106]

[0107]

[0108] Table 2

[0109] Average Coulombic efficiency (%) Example 1 99.75 Example 2 99.71 Example 3 99.63 Example 4 99.69 Example 5 99.66 Example 6 99.62 Example 7 99.57 Comparative Example 1 99.21 Comparative Example 2 98.53 Comparative Example 3 98.42 Comparative Example 4 98.31

[0110] As can be seen from Tables 1 and 2, the local high concentration electrolyte provided by the present invention has better discharge capacity retention and coulombic efficiency after being applied to lithium-ion batteries and lithium-copper half-cells, which is significantly better than Comparative Example 1 representing a conventional local high concentration electrolyte and Comparative Example 2 with the addition of an excess of 2-(diphenylphosphino)ethylamine tetrafluoroborate, which fully demonstrates that the local high concentration electrolyte provided by the present invention can improve the cycle performance of the battery and can inhibit the loss of local high concentration electrolyte anions during the cycle, and the improvement effect is derived from the addition of 2-(diphenylphosphino)ethylamine tetrafluoroborate in a specific content range provided by the present invention.

[0111] The present invention also provides an exemplary embodiment of the present invention and the electrolyte obtained in Example 1 and Comparative Example 1 for the application of the cycle performance test diagram of lithium ion batteries ( Figure 1 ), it can be seen from the figure that the cycle performance decay of the lithium-ion battery obtained by the application of Example 1 is significantly suppressed, and the cycle life is significantly improved.

[0112] The present invention also provides an exemplary coulombic efficiency test diagram of the electrolyte obtained in Example 1 and Comparative Example 1 applied to a lithium copper half-cell ( Figure 2 ), it can be seen from the figure that the coulombic efficiency stability of the lithium-copper half-cell obtained by the application of Example 1 is significantly improved.

[0113] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A composition for local high-concentration electrolyte, characterized in that: The composition contains lithium salt, solvent, diluent and 2-(diphenylphosphino)ethylamine tetrafluoroborate; The molar ratio of the lithium salt, the solvent and the diluent is 1:1-6:4-8; Based on the total mass of the composition, the content of the 2-(diphenylphosphino)ethylamine tetrafluoroborate is 0.1-0.5 wt %.

2. The composition according to claim 1, characterized in that Based on the total mass of the composition, the content of the 2-(diphenylphosphino)ethylamine tetrafluoroborate is 0.2-0.3 wt %.

3. The composition according to claim 1 or 2, characterized in that The molar content ratio of the lithium salt, the solvent and the diluent is 1:2-4:5-7.

4. The composition according to claim 1 or 2, characterized in that The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium nitrate, and lithium difluoroborate; and / or, the solvent is selected from at least one of triethyl phosphate, trimethyl phosphate, dimethyl sulfoxide, sulfolane, propylene carbonate, methyl acetate, propyl acetate, and butyl acetate; And / or, the diluent is at least one selected from 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, trifluoromethoxybenzene, fluorobenzene, p-fluorotoluene, 1,3,5-trifluorobenzene, and m-fluorotoluene.

5. The composition according to claim 4, characterized in that The lithium salt is a combination of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide in a molar ratio of 1:0.8-1.

2.

6. The composition according to claim 4, characterized in that The solvent is triethyl phosphate; And / or, the diluent is trifluoromethoxybenzene.

7. A method for preparing a local high-concentration electrolyte, characterized in that: The method is carried out using the composition for local high-concentration electrolyte according to any one of claims 1 to 6, and comprises: mixing a mixture containing the composition for local high-concentration electrolyte to obtain the local high-concentration electrolyte.

8. The local high-concentration electrolyte prepared by the method according to claim 7.

9. Use of the local high-concentration electrolyte according to claim 8 in a lithium secondary battery.

10. A lithium secondary battery, characterized in that: The lithium secondary battery comprises: a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator; the electrolyte is the local high-concentration electrolyte according to claim 8.

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