Wide-temperature-range high-voltage electrolyte, lithium battery and preparation method of lithium battery

Abstract

The invention relates to a wide-temperature-range high-voltage electrolyte, a lithium battery and a preparation method of the lithium battery. The wide-temperature-range high-voltage electrolyte comprises a lithium salt, an electrolyte solvent, a first additive, a second additive and a third additive, wherein the first additive is fluoroethylene carbonate; the second additive is at least one of 1, 3-propane sultone and propylene sulfite; and the third additive is at least one of dimethoxy (methyl) (3, 3, 3-trifluoropropyl) silane and trimethylsilyl phosphite ester.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium battery electrolytes, and in particular relates to a wide temperature range high-voltage electrolyte, a lithium battery and a preparation method thereof. Background Art

[0002] At present, non-aqueous electrolyte lithium-ion batteries have been increasingly used in the 3C consumer electronics market. With the advancement of technology, the functions of digital products are becoming increasingly rich and powerful, and the disadvantages of insufficient battery life are becoming increasingly prominent. The development trend of lithium batteries is high energy density, so the use of lithium metal as the negative electrode and the selection of high specific capacity lithium-manganese-rich or ternary positive electrode materials are the mainstream direction of future lithium batteries. Ultra-high capacity positive electrode materials are the core key to achieving specific energy. The potential positive electrode material system is analyzed as follows: Existing high-energy materials include high-nickel ternary, high-voltage lithium cobalt oxide, lithium-rich manganese and sulfur-based materials, which can show great potential in the pursuit of high energy density.

[0003] However, existing electrolyte systems often fail to meet the requirements of stable discharge under high voltage conditions and below -20°C. At the same time, in order to improve the safety of electrolytes, it is also urgent to reduce the safety issues caused by flammable liquid carbonate solvents. Summary of the invention

[0004] In view of the above technical problems, the purpose of the present invention is to provide a wide temperature range high-voltage electrolyte, a lithium battery and a preparation method thereof. By adding a specific structure of additives to the non-aqueous electrolyte, the flame retardancy or self-extinguishing property of the electrolyte is improved, thereby improving the high temperature storage, cycle performance and safety of the battery.

[0005] In a first aspect, the present invention provides a wide temperature range high-voltage electrolyte, the wide temperature range high-voltage electrolyte comprising: a lithium salt, an electrolyte solvent, a first additive, a second additive, and a third additive; Among them: the first additive is fluoroethylene carbonate; the second additive is at least one of 1,3-propane sultone and propylene sulfite; the third additive is at least one of dimethoxy(methyl) (3,3,3-trifluoropropyl) silane and trimethylsilyl phosphite.

[0006] Preferably, the lithium salt includes at least one of LiPF6, LiBF4, LiCl, LiAlCl4, LiSCN, LiCl, LiNO3, LiTFSI, LiFSI, and LiPO2F2; preferably, the lithium salt in the wide temperature range high-voltage electrolyte is 0.5-2.0 mol / L LiPF6 and 0.01-0.1 mol / L LiPO2F2.

[0007] Preferably, the electrolyte solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, methyl acetate, methyl propionate, ethyl acetate, vinyl sulfate, propylene sulfate, vinyl sulfite, diethyl sulfite, and γ-butyrolactone; preferably at least one of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0008] Preferably, the volume fraction of the electrolyte solvent in the wide temperature range high-voltage electrolyte is 60-99%, and the total amount of the additives added in the wide temperature range high-voltage electrolyte is 1-40%, preferably 5-40%.

[0009] Preferably, the first additive is added in an amount of 0.5-33.3 vol% of the wide temperature range high-voltage electrolyte, preferably 5 vol%; The amount of the second additive added is 0.5-15 vol% of the wide temperature range high voltage electrolyte, preferably 5 vol%; The amount of the third additive added is 0.05-5 vol %, preferably 0.1-5 vol %, and more preferably 1-2 vol % of the wide temperature range high voltage electrolyte.

[0010] Preferably, the ionic conductivity of the wide temperature range high-voltage electrolyte is 5 to 12 mS / cm.

[0011] In a second aspect, the present invention provides a method for preparing the above-mentioned wide temperature range high-voltage electrolyte, the preparation method comprising the following steps: adding additives and lithium salts to the electrolyte solvent in sequence to obtain the wide temperature range high-voltage electrolyte.

[0012] In a third aspect, the present invention provides a lithium battery, comprising a shell, a battery cell contained in the shell, and the above-mentioned wide temperature range high-voltage electrolyte; wherein the battery cell comprises a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode.

[0013] Preferably, the capacity retention rate of the lithium battery can reach 88.1% after 305 cycles under the conditions of a wide temperature range of -20 to 40°C and a cycle voltage of 2.0 to 4.8V; the discharge capacity at -20°C and 0.2C can reach 78.7% of the capacity at room temperature.

[0014] In a fourth aspect, the present invention provides a method for preparing the above-mentioned lithium battery, the preparation method comprising the following steps: using a diaphragm to isolate the positive electrode and the negative electrode, then performing top and side sealing, injecting the above-mentioned wide temperature range high-voltage electrolyte, forming, final sealing, and volume separation to obtain the lithium battery.

[0015] Beneficial Effects (1) The wide temperature range and high voltage electrolyte for lithium batteries provided by the present invention comprises a solvent, an additive and a lithium salt having the ability to conduct lithium ions. By adding dimethoxy(methyl)(3,3,3-trifluoropropyl)silane, propane sultone (PS) and fluoroethylene carbonate, etc. and adjusting the content of the lithium salt and the additive, a stable cycle at -20°C-40°C and a wide voltage of 2.0-4.8V can be achieved, and the ion conductivity is 5-12mS / cm; (2) The preparation process of the electrolyte of the present invention is simple, convenient for large-scale production, and can be adapted to high-nickel ternary positive electrodes, lithium-rich manganese-based positive electrodes, and composite positive electrodes prepared from lithium-rich manganese and sulfur, perovskite solid electrolytes, etc.; (3) The lithium battery of the present invention has a wider operating temperature, higher specific energy and high-voltage cycle performance. By adopting the additive provided by the present invention, the negative electrode can be protected from damage, the low-temperature cycle performance of the lithium battery can be improved, the volume of flatulence during battery circulation can be reduced, the side reactions of the electrolyte solvent can be reduced, and the life of the battery can be extended. DETAILED DESCRIPTION

[0016] The present invention is further described below by the following embodiments. It should be understood that the following embodiments are only used to illustrate the present invention, but not to limit the present invention.

[0017] First, the present invention provides a wide temperature range high-voltage electrolyte, wherein the wide temperature range high-voltage electrolyte may include: lithium salt, electrolyte solvent and additives.

[0018] In some embodiments, the lithium salt may include at least one of LiPF6, LiBF4, LiCl, LiAlCl4, LiSCN, LiCl, LiNO3, LiTFSI, LiFSI, and LiPO2F2; preferably, the lithium salt in the wide temperature range high-voltage electrolyte may be 0.5-2.0 mol / L LiPF6 and 0.01-0.1 mol / L LiPO2F2.

[0019] For LiPF6, as the concentration of lithium salt increases, the viscosity of the electrolyte increases, which will cause the lithium ion movement rate to decrease; at the same time, the increase in lithium salt concentration leads to the enhanced interaction between electrolyte anions and cations, reducing the number of free lithium ions. Therefore, considering the viscosity of the electrolyte and the number of free lithium ions, the concentration of lithium salt LiPF6 needs to be controlled within a reasonable range to ensure the current transmission speed generated by the movement of free lithium ions while having a large conductivity.

[0020] In addition, the addition of LiPO2F2 can promote the composition and morphological characteristics of the cathode-electrolyte interface (CEI) film, that is, before adding LiPO2F2, it is an inhomogeneous lithium alkyl carboxylate, and after adding it, it is transformed into a uniform LiF film. At the same time, the new film will promote the Li +The transfer of LiPO2F2 in the electrolyte further improves the electrochemical performance of the battery at low temperatures. At the same time, LiPO2F2 can also improve the properties of the positive electrode interface film, effectively inhibiting the oxidative decomposition of the electrolyte on the positive electrode surface, especially the decomposition of the LiPF6 component; at the same time, LiPO2F2 also undergoes a reduction reaction at the negative electrode to form a SEI film, which can effectively inhibit the reduction and decomposition of electrolyte components on the graphite surface. However, the solubility of LiPO2F2 in the solution is low, so if the concentration is too high, the salt cannot be fully dissolved, resulting in an uneven electrolyte, and if the concentration is too low, it cannot effectively participate in the formation of CEI and SEI.

[0021] In some embodiments, the electrolyte solvent may include at least one of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate (MF), methyl acetate (MA), methyl propionate (MP), ethyl acetate (EP), vinyl sulfate (DTD), propylene sulfate, vinyl sulfite (ES), diethyl sulfite (DES), and γ-butyrolactone (BL); preferably at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC).

[0022] Among them, single-component electrolytes are not conducive to the intercalation and deintercalation of lithium ions on the electrode, which will cause the effective lithium storage capacity to be extremely low. When the electrolyte is a single EMC or DEC, the battery cycle performance will decline to a certain extent. If DMC, DEC, and EMC are mixed and added to other carbonate-based electrolytes to form a co-solvent, the polarization phenomenon and cycle stability of the battery are significantly improved, and the corresponding lithium ion intercalation and deintercalation behavior can be observed on the electrode surface. The reason may be that there is a synergistic effect between the solvents in the mixed electrolyte, which inhibits the decomposition of the electrolyte, thereby making the electrolyte more stable.

[0023] In some embodiments, the volume fraction of the electrolyte solvent in the wide temperature range high-voltage electrolyte may be 60 to 99%.

[0024] In some embodiments, the additives may include a first additive, a second additive and a third additive; preferably, the volume fraction of the additives in the wide temperature range high-voltage electrolyte may be 1 to 40%, preferably 5 to 40%.

[0025] Wherein, the first additive may be fluoroethylene carbonate, and the added amount may be 0.5-33.3 vol%, preferably 5 vol%, of the wide temperature range high voltage electrolyte.

[0026] Fluoroethylene carbonate (FEC) can form a LiF-rich interfacial layer on the electrode surface, reducing the SEI and CEI impedance, thereby improving the low-temperature performance of the battery. The additive FEC undergoes a reduction decomposition reaction at a higher potential, effectively inhibiting the decomposition and reduction of the electrolyte solvent at a lower potential. In addition, the FEC additive in the carbonate electrolyte can produce a LiF-based CEI, stabilize the positive electrode surface and improve the cycling performance at low cut-off voltages. However, the formation of a thick LiF layer at high cut-off voltages and high rates leads to higher polarization and slower Li + transport kinetics, which in turn will reduce battery performance. Therefore, the amount of FEC added needs to be controlled within an appropriate range.

[0027] The second additive may be at least one of 1,3-propane sultone (1,3-PS) and propylene sulfite (PS), and the added amount may be 0.5-15 vol%, preferably 5 vol%, of the wide temperature range high voltage electrolyte.

[0028] 1,3-Propane sultone (1,3-PS) and propylene sulfite (PS) are high-temperature additives that have the function of inhibiting gas production. After 1,3-propylene sultone is added to the electrolyte, it can form a solid electrolyte phase interface film on the surface of the battery electrode, inhibit the co-embedding and reduction decomposition of solvent molecules in the negative electrode, and improve the cycle performance and high-temperature performance of lithium-ion batteries. At the same time, PS can form a film on the negative electrode and can better inhibit the generation of gas during high-temperature storage.

[0029] Among them, the third additive can be at least one of dimethoxy(methyl)(3,3,3-trifluoropropyl)silane and trimethylsilyl phosphite (TMSPi), and the added amount can be 0.05-5 vol%, preferably 0.1-5 vol%, and more preferably 1-2 vol% of the wide temperature range high-voltage electrolyte.

[0030] The third addition used in the present invention can promote the high-voltage stability of the electrolyte. The coordination solvent in the electrolyte caused by desolvation or intermolecular interaction in the electrolyte is oxidatively unstable during high-voltage operation. Due to the fluorinated group and the silane structure, dimethoxy(methyl)(3,3,3-trifluoropropyl)silane is solvated with Li + The binding energy is significantly higher than that of the non-solvated one. It is connected by intramolecular interactions and is not easy to break, which helps to significantly improve the stability of the electrolyte, so it has strong antioxidant ability and high pressure resistance. In addition, the additive has good miscibility with other solvents, which can promote a higher content of inorganic components in SEI, which is conducive to the formation of an inorganic SEI structure that remains uniform and stable during the cycle, and this inorganic SEI Li + The transport activation energy is greatly reduced, which is beneficial to lithium deposition and reduces dendrites.

[0031] It should be noted that the electrolyte system used in the present invention uses silane as the third additive, and the limited volume fraction is preferably ≤2%. Starting from the stability of the substance itself, combined with its excellent film-forming properties and stability to the positive and negative electrodes, the high-voltage stability of carbonate electrolytes is improved. Different from the electrolyte system using silane as a solvent, the latter is generally based on silane, with a volume fraction of 20%-30% and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) mixed to prepare a local high-concentration electrolyte for ether electrolyte systems, and generally the concentration of LiPF6 can reach 1.7 mol / L. The mechanism of action is completely different from that of conventional electrolytes. The local high-concentration electrolyte uses solvent molecules and high-concentration lithium salts to form a special solvation structure, thereby regulating the performance of the electrolyte.

[0032] It should also be noted that the battery system in which the electrolyte with the third additive provided by the present invention can be used may include a ternary system, an LRM lithium-rich manganese-based battery (the test voltage can reach 5V), etc., which is different from the conventional ether electrolyte system (mostly suitable for high-nickel ternary battery system).

[0033] In addition, the third additive used in the present invention needs to be controlled within an appropriate addition amount range. If the content is too low, the high-voltage stability of the electrolyte decreases, and the electrolyte will decompose during high-voltage cycles, thereby reducing the cycle life of the battery; if the content is too high, the solvation stage and Li + The high binding energy will lead to a decrease in the kinetics of lithium ions, affect the ionic conductivity, and at the same time cause a decrease in the low-temperature performance of the battery.

[0034] The presence of the additive used in the present invention in the same electrolyte system can form an excellent SEI film at the negative electrode through a synergistic effect, which plays a role in stabilizing the negative electrode; at the same time, a protective film of complexed metal ions can be formed at the positive electrode, thereby inhibiting the dissolution of metal ions and the decomposition of the electrolyte at the positive electrode, and finally effectively improving the high-voltage cycle performance of the battery. At the same time, due to the presence of silane and fluorinated solvents, the thermal stability of the electrolyte system is further improved, and mixed with solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) to achieve stable circulation under a wide temperature range. In addition, the additive system used in the present invention greatly improves the acid resistance and heat resistance of the electrolyte, thereby improving the life of the battery at high temperatures, and there is a significant effect compared with the prior art. The electrolyte system has the advantages of being more stable, resistant to high voltage, widely used, high lithium salt dissociation, and better additive solubility.

[0035] In some embodiments, the ionic conductivity of the wide temperature range high-voltage electrolyte may be 5 to 12 mS / cm.

[0036] The following is an exemplary description of the preparation method of the wide temperature range high-voltage electrolyte provided by the present invention. The preparation method may include the following steps: (1) In a glove box, under the conditions of water content <0.1 ppm and oxygen content <0.1 ppm, adding additives to the electrolyte solvent, and then stirring at a speed of 500 rpm for 0.5 to 4 hours to obtain an additive mixed solution; (2) In a glove box, under the conditions of water content <0.1 ppm and oxygen content <0.1 ppm, lithium salt is added to the additive mixed solution, and then stirred at a rotation speed of 500 rpm for 1 to 10 hours to obtain the wide temperature range high-voltage electrolyte.

[0037] In addition, the present invention also provides a lithium battery, wherein the lithium battery may include a housing, a battery cell contained in the housing, and the above-mentioned electrolyte; wherein the battery cell may include a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode.

[0038] In some embodiments, the positive electrode may include a positive electrode current collector and a positive electrode material layer located on the surface of the positive electrode current collector; wherein the positive electrode material layer may include a positive electrode active substance, a positive electrode conductor, and a positive electrode binder; preferably, the positive electrode active substance may include a lithium-rich manganese-based material, a sulfur-based material, a high-nickel ternary positive electrode, and a composite material prepared from lithium-rich manganese and sulfur, and a perovskite solid electrolyte.

[0039] In some embodiments, the negative electrode may include a negative electrode current collector and a negative electrode material layer located on the surface of the negative electrode current collector; wherein, the negative electrode material layer may include a negative electrode active substance, a negative electrode conductive agent, and a negative electrode binder; preferably, the negative electrode active substance may be lithium metal, copper-lithium composite active material, graphite or silicon carbon, which has a higher capacity, and is assisted by the additive of the structure described in the present invention to form a stable SEI film on the surface of the negative electrode, which can reflect the realization of a higher energy density of the battery.

[0040] The capacity retention rate of the lithium battery provided by the present invention can reach 88.1% after 305 cycles under the conditions of a wide temperature range of -20 to 40°C and a cycle voltage of 2.0 to 4.8V; the discharge capacity at -20°C and 0.2C can reach 78.7% of the capacity at room temperature.

[0041] The following is an exemplary description of the preparation method of the lithium battery provided by the present invention. The preparation method may include the following steps: (1) Positive electrode preparation: a positive electrode active material, a positive electrode conductive agent, a positive electrode binder and a solvent are mixed to prepare a positive electrode slurry, and then the positive electrode slurry is coated on the surface of the positive electrode current collector and dried, and then rolled and die-cut to obtain the positive electrode; (2) Preparation of negative electrode: using negative electrode active material, cutting it, the length and width of the cutting size are 2-6 mm larger than the positive electrode sheet, and welding the electrode ear to the cut negative electrode active material to obtain the negative electrode; (3) Using a diaphragm to separate the positive electrode and the negative electrode, and then performing top and side sealing, injecting the above-mentioned wide temperature range high-voltage electrolyte, forming, final sealing, and volume separation to obtain the lithium battery.

[0042] The preparation process of the wide temperature range high-voltage electrolyte provided by the present invention is simple and convenient for large-scale production; moreover, the electrolyte provided by the present invention can be adapted to high-nickel ternary positive electrodes, lithium-rich manganese-based positive electrodes, and composite positive electrodes prepared from lithium-rich manganese and sulfur, perovskite solid electrolytes, etc. By adopting the additive provided by the present invention, the negative electrode can be protected from damage, the low-temperature cycle performance of the lithium battery can be improved, the flatulence volume during the battery cycle can be reduced, the side reactions of the electrolyte solvent can be reduced, and the battery life can be extended. The lithium battery provided by the present invention has a wider operating temperature, higher specific energy and high-voltage cycle performance.

[0043] In addition, the present invention also improves the flame retardancy or self-extinguishing property of the electrolyte by adding an additive of a specific structure to the non-aqueous electrolyte. FEC fluorocarbonate has higher flame retardancy due to its high flash point or no flash point, is conducive to film formation on the surface of the negative electrode, and has a low melting point. Furthermore, the reason why the solvent in the electrolyte burns is mainly due to the chain reaction itself. By adding a flame retardant with a high boiling point and a high flash point to the electrolyte, the safety of the lithium-ion battery can be improved. The reported flame retardant additives mainly include three categories: organophosphorus series, fluorocarbonate and composite flame retardant additives. The dimethoxy(methyl) (3,3,3-trifluoropropyl) silane used in the present invention can improve its comprehensive performance by halogenation or the introduction of multiple functional groups. It has a high flash point and is a composite flame retardant additive when combined with FEC.

[0044] The following further examples are given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all belong to the scope of protection of the present invention. The specific process parameters of the following examples are also only examples within a suitable range, that is, those skilled in the art can make selections within a suitable range through the description of this article, and are not limited to the specific values ​​​​exemplified below. If not specifically stated, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0045] Example 1

[0046] The method for preparing a wide temperature range high voltage electrolyte and a lithium battery provided in this embodiment comprises the following steps: (1) Preparation of wide temperature range high-voltage electrolyte: In an argon glove box, 50 mL of diethyl carbonate (DEC) and 50 mL of ethyl methyl carbonate (EMC) were mixed into a mixed solvent under the conditions of water content <0.1 ppm and oxygen content <0.1 ppm; in the glove box, 5% of fluoroethylene carbonate, 5% of propylene sulfite (PS) and 2% of dimethoxy(methyl)(3,3,3-trifluoropropyl)silane were added to the mixed system of DEC:EMC=1:1 to obtain an additive mixed solution. Under stirring, 15.2 g of lithium hexafluorophosphate (LiPF6) and 0.54 g of lithium difluorophosphate (LiPO2F2) were added to the additive mixed solution so that the lithium salt concentrations were 1 mol / L and 0.05 mol / L, respectively. The mixture was stirred at room temperature for 4 h to obtain the wide temperature range high-voltage electrolyte. (2) Preparation of positive electrode: The active material is lithium-rich manganese. In addition, polyvinylidene fluoride, carbon nanotubes, conductive carbon black and N-methylpyrrolidone are stirred in a high-speed disperser to prepare positive electrode slurry. The positive electrode slurry is coated on a metal aluminum foil at a drying temperature of 120°C. After drying for 24 hours, the positive electrode sheet is obtained by roller pressing and die cutting. (3) Preparation of negative electrode: using a metal lithium foil with a thickness of 50 μm, cutting it, the length and width of the cutting size are 2-6 mm larger than the positive electrode sheet, and welding the copper electrode ear to the cut lithium foil to obtain the negative electrode; (4) Preparation of lithium battery: The prepared positive electrode sheet, wide temperature range high-voltage electrolyte, negative electrode sheet lithium foil and 9 μm separator are assembled together, and then the top and side are sealed and liquid is injected. The battery is left standing at room temperature for 24-72 hours to fully wet the battery electrode sheet; then the battery is charged at a current of 0.05C for 4 hours to form a stable and dense SEI film, and then charged at a current of 0.1C to a cut-off voltage of 4.8V, and then discharged to 2.0V for a formation process; finally, the lithium battery is obtained after final sealing and capacity separation.

[0047] The test shows that the capacity retention rate of the lithium battery prepared in Example 1 after 305 cycles at room temperature and a cycle voltage of 2.0-4.8V is 88.1%; the discharge capacity at -20°C and 0.2C is 78.7% of the capacity at room temperature.

[0048] Example 2

[0049] The preparation method of the wide temperature range high voltage electrolyte and lithium battery provided in this embodiment refers to that in Embodiment 1, the main difference is that the volume fraction of the additive dimethoxy(methyl)(3,3,3-trifluoropropyl)silane in step (1) is 0.05%.

[0050] Example 3

[0051] The preparation method of the wide temperature range high voltage electrolyte and lithium battery provided in this embodiment refers to that in Embodiment 1, the main difference is that the volume fraction of the additive dimethoxy(methyl)(3,3,3-trifluoropropyl)silane in step (1) is 5%.

[0052] Example 4

[0053] The preparation method of the wide temperature range high voltage electrolyte and lithium battery provided in this embodiment refers to that in Example 1, the main difference is that the solvent used in step (1) is 100 mL of diethyl carbonate (DEC).

[0054] Example 5

[0055] The preparation method of the wide temperature range high voltage electrolyte and lithium battery provided in this embodiment refers to that in Example 1, the main difference is that the solvent used in step (1) is 100 mL of ethyl methyl carbonate (EMC).

[0056] Example 6

[0057] The method for preparing the wide temperature range high voltage electrolyte and lithium battery provided in this embodiment refers to that in Example 1, the main difference is that the concentration of LiPO2F2 in step (1) is 0.01 mol / L.

[0058] Example 7

[0059] The preparation method of the wide temperature range high voltage electrolyte and lithium battery provided in this embodiment refers to that in Embodiment 1, the main difference is that the concentration of LiPO2F2 in step (1) is 0.1 mol / L.

[0060] Example 8

[0061] The method for preparing the wide temperature range high voltage electrolyte and lithium battery provided in this embodiment refers to that in Example 1, the main difference is that the concentration of LiPF6 in step (1) is 0.5 mol / L.

[0062] Example 9

[0063] The method for preparing the wide temperature range high voltage electrolyte and lithium battery provided in this embodiment refers to that in Embodiment 1, the main difference is that the concentration of LiPF6 in step (1) is 2.0 mol / L.

[0064] Example 10

[0065] The preparation method of the wide temperature range high voltage electrolyte and lithium battery provided in this embodiment refers to that in Embodiment 1, the main difference is that in step (1), propylene sulfite (PS) is changed to 1,3-propane sultone (1,3-PS).

[0066] Embodiment 11

[0067] The method for preparing the wide temperature range high voltage electrolyte and lithium battery provided in this embodiment refers to that in Embodiment 1, the main difference is that the volume fraction of propylene sulfite (PS) in step (1) is 0.5%.

[0068] Example 12

[0069] The method for preparing the wide temperature range high voltage electrolyte and lithium battery provided in this embodiment refers to that in Embodiment 1, the main difference is that the volume fraction of propylene sulfite (PS) in step (1) is 15%.

[0070] Example 13

[0071] The preparation method of the wide temperature range high voltage electrolyte and lithium battery provided in this embodiment refers to that in Embodiment 1, the main difference is that the volume fraction of fluoroethylene carbonate FEC is 0.5%.

[0072] Embodiment 14

[0073] The preparation method of the wide temperature range high voltage electrolyte and lithium battery provided in this embodiment refers to that in Embodiment 1, the main difference is that the volume fraction of fluoroethylene carbonate FEC is 33.3%.

[0074] Comparative Example 1

[0075] The preparation method of the wide temperature range high voltage electrolyte and lithium battery provided in this comparative example refers to Example 1, with the main difference being that the volume fraction of the additive dimethoxy(methyl)(3,3,3-trifluoropropyl)silane in step (1) is 0%.

[0076] Comparative Example 2

[0077] The preparation method of the wide temperature range high voltage electrolyte and lithium battery provided in this comparative example refers to Example 1, with the main difference being that the concentration of LiPO2F2 in step (1) is 0 mol / L.

[0078] The performance of the batteries prepared in the above examples and comparative examples was tested, and the results are shown in the following table: Table 1 Battery performance test results of examples and comparative examples

[0079] It can be seen from Table 1 above that the electrolyte system provided by the present invention can improve the high-voltage stable cycle and low-temperature discharge performance of lithium batteries, among which the lithium metal battery obtained in Example 1 has the best performance, the cycle life can reach 305 weeks, the capacity retention rate reaches 88.1% of the initial discharge, and the low-temperature discharge capacity can reach 78.7% at room temperature.

[0080] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A high-voltage electrolyte with a wide temperature range, characterized in that: The wide temperature range high voltage electrolyte comprises: a lithium salt, an electrolyte solvent and a first additive, a second additive and a third additive; Among them: the first additive is fluoroethylene carbonate; the second additive is at least one of 1,3-propane sultone and propylene sulfite; the third additive is at least one of dimethoxy(methyl) (3,3,3-trifluoropropyl) silane and trimethylsilyl phosphite.

2. The wide temperature range high voltage electrolyte according to claim 1, characterized in that: The lithium salt includes at least one of LiPF6, LiBF4, LiCl, LiAlCl4, LiSCN, LiCl, LiNO3, LiTFSI, LiFSI, and LiPO2F2; preferably, the lithium salt in the wide temperature range high-voltage electrolyte is 0.5-2.0 mol / L LiPF6 and 0.01-0.1 mol / L LiPO2F2.

3. The wide temperature range high voltage electrolyte according to claim 1 or 2, characterized in that: The electrolyte solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, methyl acetate, methyl propionate, ethyl acetate, vinyl sulfate, propylene sulfate, vinyl sulfite, diethyl sulfite, and γ-butyrolactone; preferably at least one of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

4. The wide temperature range high voltage electrolyte according to any one of claims 1 to 3, characterized in that: The volume fraction of the electrolyte solvent in the wide temperature range high-voltage electrolyte is 60-99%, and the total amount of the additives added in the wide temperature range high-voltage electrolyte is 1-40%, preferably 5-40%.

5. The wide temperature range high voltage electrolyte according to any one of claims 1 to 4, characterized in that: The amount of the first additive added is 0.5-33.3 vol% of the wide temperature range high voltage electrolyte, preferably 5 vol%; The amount of the second additive added is 0.5-15 vol% of the wide temperature range high voltage electrolyte, preferably 5 vol%; The amount of the third additive added is 0.05-5 vol %, preferably 0.1-5 vol %, and more preferably 1-2 vol % of the wide temperature range high voltage electrolyte.

6. The wide temperature range high voltage electrolyte according to any one of claims 1 to 5, characterized in that: The ion conductivity of the wide temperature range high-voltage electrolyte is 5 to 12 mS / cm.

7. A method for preparing a wide temperature range high-voltage electrolyte according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: adding additives and lithium salts to an electrolyte solvent in sequence to obtain the wide temperature range high-voltage electrolyte.

8. A lithium battery, characterized in that: The lithium battery comprises a shell, a battery cell contained in the shell, and a wide temperature range high-voltage electrolyte according to any one of claims 1 to 6; wherein the battery cell comprises a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode.

9. The lithium battery according to claim 8, characterized in that: The capacity retention rate of the lithium battery can reach 88.1% after 305 cycles under the conditions of a wide temperature range of -20 to 40°C and a cycle voltage of 2.0 to 4.8V; the discharge capacity at -20°C and 0.2C can reach 78.7% of the capacity at room temperature.

10. A method for preparing a lithium battery according to claim 8 or 9, characterized in that: The preparation method comprises the following steps: using a diaphragm to isolate the positive electrode and the negative electrode described in claim 8, then performing top and side sealing, injecting a wide temperature range high-voltage electrolyte described in any one of claims 1 to 6, forming, final sealing, and volume separation to obtain the lithium battery.

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