Local high-concentration lithium battery electrolyte and lithium secondary battery

Abstract

The invention discloses a local high-concentration lithium battery electrolyte and a lithium secondary battery, the electrolyte is formed by blending a solvation structure and an interfacial film of a lithium metal battery electrolyte by adopting halogenated pyridine and a hydrofluoroether diluent, and an SEI film rich in lithium fluoride / lithium chloride is formed by introducing halogenated pyridine; by promoting decomposition of anions, an inorganic matter interface is constructed on the surface of the negative electrode, so that growth of lithium dendrites is inhibited, formation of dead lithium is slowed down, conductivity of an SEI membrane is improved, and cycling stability of the lithium negative electrode is improved; n atoms of a pyridine ring in the halogenated pyridine diluent are combined with protons in hydrofluoric acid generated by desorption of the hydrofluoroether diluent to inhibit hydrofluoric acid generated by decomposition of the hydrofluoroether diluent, so that the acidity of the electrolyte is reduced, corrosion of the electrolyte to positive electrode particles and dissolution of transition metal are inhibited, and the cycle life of the positive electrode is prolonged; and stable circulation of the battery is realized.

Description

Technical Field

[0001] The invention belongs to the field of electrochemical energy storage, and specifically relates to a local high-concentration lithium battery electrolyte and a lithium secondary battery. Background Art

[0002] Lithium-ion batteries, which consist of a graphite anode and a lithium iron phosphate / transition metal layered oxide cathode, play an irreplaceable role in our lives due to their zero memory effect and long cycle life. In recent years, with the growing demand for portable electronic products and electric vehicles, the market has put forward higher requirements for secondary batteries. However, the energy density of existing lithium-ion batteries can hardly exceed the upper limit of 300Wh / kg. In contrast, lithium metal anode has become an ideal choice for the next generation of high energy density battery anode due to its extremely high theoretical specific capacity (3860mAh / g) and lowest electrochemical potential (-3.04V vsSHE).

[0003] However, lithium metal anodes face a series of problems, including low coulombic efficiency caused by severe electrode-electrolyte reactions, safety risks caused by the growth of lithium dendrites, and incompatibility with existing carbonate electrolytes. Existing high-concentration electrolytes (salt concentration>3mol / L) can not only improve the compatibility of electrolytes with lithium anodes by forming a stable interface film, but also have the advantages of reducing the flammability of electrolytes and improving the high-voltage resistance of electrolytes. However, the current high-concentration electrolytes still have defects such as high viscosity and poor wettability with pole pieces and diaphragms, which affect the ion transfer rate under actual working conditions and cannot meet the actual application requirements of lithium metal secondary batteries. Although the above problems can be solved by introducing hydrofluoroethers into high-concentration electrolytes, the defluorination and acid production of fluorinated diluents in existing local high-concentration electrolytes and the poor conductivity of the interface film still make it impossible to achieve long-life lithium metal batteries. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a locally high-concentration lithium battery electrolyte and a lithium secondary battery. By adjusting the solvation structure and interface film formation of the lithium metal battery electrolyte, the problems of defluorination and acid production of the fluorinated diluent and poor conductivity of the interface film in the existing locally high-concentration lithium battery electrolyte are solved, thereby improving the cycle life of the positive electrode.

[0005] The present invention is achieved through the following technical solutions:

[0006] A locally high-concentration lithium battery electrolyte comprises a lithium salt, an organic solvent, a hydrofluoroether diluent and a halogenated pyridine diluent.

[0007] Preferably, the hydrofluoroether diluent is at least one of 1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, 1,1,1,2,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether.

[0008] Preferably, the halogenated pyridine diluent has the following general structural formula:

[0009]

[0010] Among them, at least one of R1-R5 is a fluorine atom or a chlorine atom, and the others are hydrogen atoms, alkyl groups, halogenated alkyl groups or halogen atoms.

[0011] Preferably, the halogenated pyridine diluent is at least one of 1-fluoropyridine, 1-chloropyridine, 1-trifluoromethylpyridine, 1-trichloromethylpyridine, 2,3,5,6-tetrafluoropyridine and pentafluoropyridine.

[0012] Preferably, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalatoborate), lithium difluorooxalatoborate and lithium nitrate.

[0013] Preferably, the organic solvent is at least one of an ester solvent, an ether solvent, a nitrile solvent and a sulfone solvent.

[0014] Preferably, the concentration of the lithium salt is 0.5-4 mol / L, the molar ratio of the lithium salt to the organic solvent is 1:(1-20); the molar ratio of the total amount of the hydrofluoroether diluent and the halogenated pyridine diluent to the lithium salt is (1-20):1.

[0015] Preferably, the molar ratio of the hydrofluoroether diluent to the halogenated pyridine diluent is (0.1-10):1.

[0016] A lithium secondary battery comprises a positive electrode, a negative electrode, a separator and the locally high-concentration lithium battery electrolyte according to any one of claims 1 to 7.

[0017] Preferably, the negative electrode material is lithium metal, and the positive electrode material is lithium iron phosphate (LiFePO4), lithium iron manganese phosphate (LiFe x Mn y PO4), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium nickel cobalt manganese oxide (LiNi x Co y Mn z O2), lithium nickel cobalt aluminum oxide (LiNi x Coy Al z At least one of oxygen (O2) and sulfur (S).

[0018] The present invention has the following beneficial effects:

[0019] The local high-concentration lithium battery electrolyte of the present invention adopts halogenated pyridine as a local high-concentration lithium battery electrolyte diluent, and is matched with a hydrofluoroether diluent to prepare the solvation structure and interface film formation of the lithium metal battery electrolyte. The halogenated pyridine diluent can be fully miscible with the organic solvent and the hydrofluoroether diluent, and can maintain the solvation structure enriched with anions; the SEI film rich in lithium fluoride / lithium chloride is formed by introducing halogenated pyridine, and the inorganic interface is constructed on the surface of the negative electrode by promoting the decomposition of anions to inhibit the growth of lithium dendrites and slow down the formation of dead lithium, thereby achieving uniform lithium deposition and improving the conductivity of the SEI film. The halogen atoms in the diluent can form an inorganic SEI film and construct a stable solid electrolyte interface film rich in LiF and LiCl on the surface of the positive and negative electrodes, inhibiting the continuous side reactions of the electrode and the electrolyte, and improving the cycle stability of the lithium negative electrode.

[0020] The present invention utilizes the N atom of the pyridine ring in the halogenated pyridine diluent to combine with the proton in the hydrofluoric acid generated by the desorption of the hydrofluoroether diluent, inhibits the hydrofluoric acid generated by the decomposition of the hydrofluoroether diluent, thereby reducing the acidity of the electrolyte, inhibiting the corrosion of the electrolyte on the positive electrode particles and the dissolution of the transition metal, thereby improving the cycle life of the positive electrode.

[0021] The electrolyte of the present invention has low cost, simple preparation method and is easy to mass produce. The present invention can greatly improve the energy density, cycle performance and calendar life of lithium metal batteries. The electrolyte used in the present invention effectively improves the stability of the electrolyte to the high-voltage positive electrode and lithium metal, and realizes the stable cycle of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The battery cycle life diagram of Example 1 and Comparative Example 3;

[0023] Figure 2 It is a comparison chart of oxidation stability of Examples 1 to 3 and Comparative Example 1. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0025] Example 1

[0026] The preparation steps of the local high-concentration lithium battery electrolyte for lithium secondary batteries are as follows:

[0027] 1.8 mol of lithium salt lithium bis(fluorosulfonyl)imide was weighed in a glove box and dissolved in 1 L of a mixed solvent to obtain a locally high-concentration lithium battery electrolyte. The mixed solvent was a mixture of an organic solvent ethylene glycol dimethyl ether, a hydrofluoroether diluent 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, and a halogenated pyridine diluent 2,3,5,6-tetrafluoropyridine in a molar ratio of 1:2:1.

[0028] Among them, the lithium salt concentration is 1.8 mol / L, the molar ratio of lithium salt to organic solvent is 1:1.2, the molar ratio of hydrofluoroether diluent to halogenated pyridine diluent is 2:1, and the molar ratio of the total amount of the hydrofluoroether diluent and the halogenated pyridine diluent to the lithium salt is 3:1.

[0029] Example 2

[0030] The preparation steps of the local high-concentration lithium battery electrolyte for lithium secondary batteries are as follows:

[0031] In a glove box, 1 mol of lithium bis(fluorosulfonyl)imide was weighed and dissolved in 1 L of a mixed solvent to obtain a locally high-concentration lithium battery electrolyte. The mixed solvent was a mixture of an organic solvent, ethylene glycol diethyl ether, a hydrofluoroether diluent, 1,1,2,2-tetrafluoroethyl ether, and a halogenated pyridine diluent, 1-chloropyridine, in a molar ratio of 1:2.5:1.

[0032] Among them, the lithium salt concentration is 1.0 mol / L, the molar ratio of lithium salt to organic solvent is 1:2, the molar ratio of hydrofluoroether diluent to halogenated pyridine diluent is 2.5:1, and the molar ratio of the total amount of the hydrofluoroether diluent and the halogenated pyridine diluent to the lithium salt is 3:1.

[0033] Example 3

[0034] The preparation steps of the local high-concentration lithium battery electrolyte for lithium secondary batteries are as follows:

[0035] In a glove box, 2 mol of lithium bis(fluorosulfonyl)imide was weighed and dissolved in 1 L of a mixed solvent to obtain a locally high-concentration lithium battery electrolyte. The mixed solvent was a mixture of an organic solvent, dimethyl carbonate, a hydrofluoroether diluent, 1,1,1,2,3,3,-hexafluoropropyl-2,2,2-trifluoroethyl ether, and a halogenated pyridine diluent, 1-trichloromethylpyridine, in a molar ratio of 1:2.5:1.

[0036] Among them, the lithium salt concentration is 2.0 mol / L, the molar ratio of lithium salt to organic solvent is 1:1.5, the molar ratio of hydrofluoroether diluent to halogenated pyridine diluent is 2.5:1, and the molar ratio of the total amount of the hydrofluoroether diluent and the halogenated pyridine diluent to the lithium salt is 2.5:1.

[0037] Example 4

[0038] The preparation steps of the local high-concentration lithium battery electrolyte for lithium secondary batteries are as follows:

[0039] In a glove box, 1.5 mol of lithium bis(fluorosulfonyl)imide was weighed and dissolved in 1 L of a mixed solvent to obtain a locally high-concentration lithium battery electrolyte, wherein the mixed solvent was a mixture of an organic solvent, acetonitrile, a hydrofluoroether diluent, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, and a halogenated pyridine diluent, pentafluoropyridine, in a molar ratio of 1:2.5:0.5.

[0040] Among them, the lithium salt concentration is 1.5 mol / L, the molar ratio of lithium salt to organic solvent is 1:2, the molar ratio of hydrofluoroether diluent to halogenated pyridine diluent is 5:1, and the molar ratio of the total amount of the hydrofluoroether diluent and the halogenated pyridine diluent to the lithium salt is 5:1.

[0041] Example 5

[0042] The preparation steps of the local high-concentration lithium battery electrolyte for lithium secondary batteries are as follows:

[0043] In a glove box, 1.5 mol of lithium bis(fluorosulfonyl)imide and 0.3 mol of lithium bis(trifluoromethyl)sulfonylimide were weighed and dissolved in 1 L of a mixed solvent to obtain a locally high-concentration lithium battery electrolyte. The mixed solvent was a mixture of an organic solvent, acetonitrile, a hydrofluoroether diluent, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, and a halogenated pyridine diluent, pentafluoropyridine, in a molar ratio of 1:2.5:0.5.

[0044] Among them, the lithium salt concentration is 1.8 mol / L, the molar ratio of lithium salt to organic solvent is 1:1.4, the molar ratio of hydrofluoroether diluent to halogenated pyridine diluent is 5:1, and the molar ratio of the total amount of the hydrofluoroether diluent and the halogenated pyridine diluent to the lithium salt is 2:1.

[0045] Example 6

[0046] The preparation steps of the local high-concentration lithium battery electrolyte for lithium secondary batteries are as follows:

[0047] In a glove box, 1.5 mol of lithium bis(fluorosulfonyl)imide and 0.1 mol of lithium nitrate were weighed and dissolved in 1 L of a mixed solvent to obtain a locally high-concentration lithium battery electrolyte. The mixed solvent was a mixture of an organic solvent, acetonitrile, a hydrofluoroether diluent, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, and a halogenated pyridine diluent, pentafluoropyridine, in a molar ratio of 1:2.5:0.5.

[0048] Among them, the lithium salt concentration is 1.6 mol / L, the molar ratio of lithium salt to organic solvent is 1:4, the molar ratio of hydrofluoroether diluent to halogenated pyridine diluent is 5:1, and the molar ratio of the total amount of the hydrofluoroether diluent and the halogenated pyridine diluent to the lithium salt is 3:1.

[0049] Example 7

[0050] The preparation steps of the local high-concentration lithium battery electrolyte for lithium secondary batteries are as follows:

[0051] In a glove box, 1.5 mol of lithium bis(fluorosulfonyl)imide and 0.2 mol of lithium bis(oxalatoborate) were weighed and dissolved in 1 L of a mixed solvent to obtain a locally high-concentration lithium battery electrolyte. The mixed solvent was a mixture of an organic solvent, acetonitrile, a hydrofluoroether diluent, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, and a halogenated pyridine diluent, pentafluoropyridine, in a molar ratio of 1:2.5:0.5.

[0052] Among them, the lithium salt concentration is 1.7 mol / L, the molar ratio of lithium salt to organic solvent is 1:2.5, the molar ratio of hydrofluoroether diluent to halogenated pyridine diluent is 5:1, and the molar ratio of the total amount of the hydrofluoroether diluent and the halogenated pyridine diluent to the lithium salt is 3:1.

[0053] Example 8

[0054] The preparation steps of the local high-concentration lithium battery electrolyte for lithium secondary batteries are as follows:

[0055] In a glove box, 1.5 mol of lithium hexafluorophosphate, 0.5 mol of lithium tetrafluoroborate and 2 mol of lithium difluorooxalate borate were weighed and dissolved in 1 L of a mixed solvent to obtain a local high-concentration lithium battery electrolyte. The mixed solvent is a mixture of an organic solvent dimethyl sulfone, a hydrofluoroether diluent 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether and a halogenated pyridine diluent 1-trifluoromethylpyridine in a molar ratio of 1:2.0:0.2.

[0056] Among them, the lithium salt concentration is 4 mol / L, the molar ratio of lithium salt to organic solvent is 1:2.6, the molar ratio of hydrofluoroether diluent to halogenated pyridine diluent is 10:1, and the molar ratio of the total amount of the hydrofluoroether diluent and the halogenated pyridine diluent to the lithium salt is 5:1.

[0057] Example 9

[0058] The preparation steps of the local high-concentration lithium battery electrolyte for lithium secondary batteries are as follows:

[0059] In a glove box, 0.5 mol of lithium difluorooxalate borate was weighed and dissolved in 1 L of a mixed solvent to obtain a locally high-concentration lithium battery electrolyte. The mixed solvent was a mixture of an organic solvent diphenyl sulfone, a hydrofluoroether diluent 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether, and a halogenated pyridine diluent 1-fluoropyridine in a molar ratio of 1:0.1:1.

[0060] Among them, the concentration of lithium salt is 0.5 mol / L, the molar ratio of lithium salt to organic solvent is 1:1, the molar ratio of hydrofluoroether diluent to halogenated pyridine diluent is 0.1:1, and the molar ratio of the total amount of the hydrofluoroether diluent and the halogenated pyridine diluent to the lithium salt is 1:1.

[0061] Example 10

[0062] The preparation steps of the local high-concentration lithium battery electrolyte for lithium secondary batteries are as follows:

[0063] In a glove box, 1 mol of lithium difluorooxalatoborate and 1 mol of lithium tetrafluoroborate were weighed and dissolved in 1 L of a mixed solvent to obtain a locally high-concentration lithium battery electrolyte. The mixed solvent is a mixture of an organic solvent, a hydrofluoroether diluent, and a halogenated pyridine diluent in a molar ratio of 1:0.1:1. The organic solvent is diphenyl sulfone and dimethyl sulfone, the hydrofluoroether diluent is 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, and the halogenated pyridine diluent is 1-fluoropyridine, pentafluoropyridine, and 1-chloropyridine.

[0064] Among them, the lithium salt concentration is 2 mol / L, the molar ratio of lithium salt to organic solvent is 1:20, the molar ratio of hydrofluoroether diluent to halogenated pyridine diluent is 0.1:1, and the molar ratio of the total amount of the hydrofluoroether diluent and the halogenated pyridine diluent to the lithium salt is 20:1.

[0065] The halogenated pyridine diluent added in the above embodiment has the following general structural formula:

[0066]

[0067] Wherein, at least one of R1-R5 is a fluorine atom or a chlorine atom, and the others are hydrogen atoms, alkyl groups, halogenated alkyl groups or halogen atoms. Except for the examples listed, all halogenated pyridines conforming to the above structure can be used as the diluent of the present invention.

[0068] Comparative Example 1

[0069] The preparation steps of the local high-concentration lithium battery electrolyte for lithium secondary batteries are as follows:

[0070] 1.8 mol of lithium bis(fluorosulfonyl)imide was weighed in a glove box and dissolved in 1 L of a mixed solvent to obtain a locally high-concentration lithium battery electrolyte, wherein the mixed solvent was a mixture of ethylene glycol dimethyl ether and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in a molar ratio of 1:3.

[0071] Comparative Example 2

[0072] The preparation steps of the local high-concentration lithium battery electrolyte for lithium secondary batteries are as follows:

[0073] 2 mol of lithium bis(fluorosulfonyl)imide was weighed in a glove box and dissolved in 1 L of a mixed solvent to obtain a locally high-concentration lithium battery electrolyte, wherein the mixed solvent was a mixture of dimethyl carbonate and 1,1,1,2,3,3,-hexafluoropropyl-2,2,2-trifluoroethyl ether in a molar ratio of 1:2.

[0074] Comparative Example 3

[0075] Ordinary carbonate electrolyte, preparation steps are as follows:

[0076] In a glove box, 1 mol of lithium hexafluorophosphate was weighed and dissolved in 1 L of a mixed solvent to obtain a common carbonate electrolyte, wherein the mixed solvent was a mixture of ethylene carbonate and dimethyl carbonate in a molar ratio of 3:7.

[0077] The embodiments 1-4 of the present invention all obtain locally high-concentration lithium battery electrolytes with good cycle stability and low cost, and are compared with the comparative examples 1-3. The specific research results and methods are as follows:

[0078] 1. Battery Assembly

[0079] The electrolytes of the comparative example and the embodiment are respectively used to assemble batteries, and the battery assembly method is as follows:

[0080] In a glove box, the positive electrode shell, NCM811 positive electrode sheet, electrolyte, diaphragm, electrolyte, negative electrode sheet, gasket, spring, and negative electrode shell are assembled in sequence, and sealed in a battery sealing machine to obtain an assembled lithium battery.

[0081] 2. Performance Test

[0082] The assembled battery was activated at 0.1C for three cycles in the voltage range of 2.8-4.4V, and then subjected to constant current charge and discharge tests at 0.5C to analyze the comprehensive effects of different electrolyte formulations on battery performance. The test results are shown in Table 1:

[0083] Table 1 Electrolyte and battery performance test table

[0084]

[0085]

[0086] The results in Table 1 show that compared with the existing electrolyte, the local high-concentration lithium battery electrolyte containing halogenated pyridine diluent provided by this application has been improved to varying degrees in viscosity, freezing point and room temperature conductivity. Among them, lower viscosity is conducive to diaphragm infiltration and rapid battery charging and discharging; lower freezing point is conducive to low-temperature battery discharge; higher ion conductivity is conducive to rapid ion transmission and improved battery charging and discharging performance; after the above performance is improved, the capacity retention rate of NCM811-lithium battery after 200 cycles is significantly improved. The local high-concentration lithium battery electrolyte of this application provides technical support for the realization of high-energy long-cycle lithium batteries.

[0087] The difference between Examples 7-10 of the present application is that only the composition and proportion of the lithium salt are adjusted. The comparison results in Table 1 show that the lithium salts involved in the present application can be combined in any proportion to achieve better performance.

[0088] The assembled lithium secondary battery comprises a positive electrode, a negative electrode, a separator and the locally high-concentration lithium battery electrolyte according to any one of claims 1 to 7. The negative electrode material is lithium metal, the positive electrode material is lithium iron phosphate (LiFePO4), lithium iron manganese phosphate (LiFe x Mn y PO4), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium nickel cobalt manganese oxide (LiNi x Co y Mn z O2), lithium nickel cobalt aluminum oxide (LiNi x Co y Al z At least one of oxygen (O2) and sulfur (S).

[0089] In summary, the local high-concentration lithium battery electrolyte used in the present invention can solve the problem of low charge and discharge life of existing lithium secondary batteries, and provides an effective solution for realizing high energy density and long life lithium batteries.

Claims

1. A local high concentration lithium battery electrolyte, characterized in that: Including lithium salts, organic solvents, hydrofluoroether diluents and halogenated pyridine diluents.

2. The local high concentration lithium battery electrolyte according to claim 1, characterized in that: The hydrofluoroether diluent is at least one of 1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, 1,1,1,2,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether.

3. The local high concentration lithium battery electrolyte according to claim 1, characterized in that: The halogenated pyridine diluent has the following general structural formula: Among them, at least one of R1-R5 is a fluorine atom or a chlorine atom, and the others are hydrogen atoms, alkyl groups, halogenated alkyl groups or halogen atoms.

4. The local high concentration lithium battery electrolyte according to claim 3, characterized in that: The halogenated pyridine diluent is at least one of 1-fluoropyridine, 1-chloropyridine, 1-trifluoromethylpyridine, 1-trichloromethylpyridine, 2,3,5,6-tetrafluoropyridine and pentafluoropyridine.

5. The local high concentration lithium battery electrolyte according to claim 1, characterized in that: The lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalatoborate), lithium difluorooxalatoborate and lithium nitrate.

6. The local high concentration lithium battery electrolyte according to claim 1, characterized in that: The organic solvent is at least one of an ester solvent, an ether solvent, a nitrile solvent and a sulfone solvent.

7. The local high concentration lithium battery electrolyte according to claim 1, characterized in that: The concentration of the lithium salt is 0.5-4 mol / L, the molar ratio of the lithium salt to the organic solvent is 1:(1-20); the molar ratio of the total amount of the hydrofluoroether diluent and the halogenated pyridine diluent to the lithium salt is (1-20):

1.

8. The local high concentration lithium battery electrolyte according to claim 1, characterized in that: The molar ratio of the hydrofluoroether diluent to the halogenated pyridine diluent is (0.1-10):

1.

9. A lithium secondary battery, characterized in that: The invention comprises a positive electrode, a negative electrode, a separator and the locally high-concentration lithium battery electrolyte according to any one of claims 1 to 7.

10. The lithium secondary battery according to claim 9, characterized in that: The negative electrode material is lithium metal, and the positive electrode material is lithium iron phosphate (LiFePO4), lithium iron manganese phosphate (LiFe x Mn y PO4), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium nickel cobalt manganese oxide (LiNi x Co y Mn z O2), lithium nickel cobalt aluminum oxide (LiNi x Co y Al z At least one of oxygen (O2) and sulfur (S).

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