Electrolyte, preparation method thereof and battery application

Abstract

The embodiment of the invention discloses an electrolyte, a preparation method thereof and a battery application. The electrolyte comprises a film-forming additive, an infiltration additive and an organic mixed solvent comprising a carbonic ester solvent and a carboxylic ester solvent, the carbonic ester solvent comprises a carbonic ester solvent and a fluoro-carbonic ester solvent, the carboxylic ester solvent comprises a carboxylic ester solvent and a fluoro-carboxylic ester solvent, and the fluoro-carbonic ester solvent comprises a fluoro-carbonic ester solvent and a fluoro-carbonic ester solvent. The volume percentage of the carboxylic ester solvent in the organic mixed solvent is 20%-40%; the wetting additive comprises fluorobenzene and 1, 1, 2, 2-tetrafluoroethyl-2, 2, 3, 3-tetrafluoropropyl ether, and the wetting additive comprises fluorobenzene and 1, 1, 2, 2-tetrafluoroethyl-2, 2, 3, 3-tetrafluoropropyl ether. When the electrolyte is used in the double-graphite battery, the low-temperature cycle performance of the battery is good, the adaptability of the battery to an extreme environment is improved, and the electrolyte has important significance in promoting the development and application of the double-graphite battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, and in particular relates to an electrolyte, a preparation method thereof and battery application. Background Art

[0002] High-efficiency and low-cost energy storage technology is the focus of the development of the new energy industry. Lithium-ion batteries are considered to be the mainstream direction of the future development of the energy storage industry due to their high energy density and long cycle life. However, affected by market expansion, the prices of raw materials and finished products remain high, and cobalt-containing positive electrode raw materials such as lithium cobalt oxide and ternary have long relied on imports. It can be foreseen that the development of the energy storage industry will further increase the price of raw materials and increase uncertainty in future international competition. Therefore, whether from the perspective of reducing costs and increasing efficiency, or from the perspective of self-sufficiency in raw materials and reducing dependence on foreign countries, the development of new cheap and self-sufficient energy storage technologies is the only way to promote the development of the energy storage industry.

[0003] Graphite can be used as both positive and negative electrodes to assemble dual-graphite batteries. Using graphite as an electrode material will effectively reduce battery costs. Therefore, dual-graphite batteries are considered to be one of the candidates for the development of the energy storage industry and have received widespread attention in recent years. Since dual-graphite batteries use electrolytes as charge carriers, they usually use high-concentration electrolytes with higher viscosity. When the temperature decreases, the viscosity of the electrolyte further increases, making the low-temperature cycle performance of dual-graphite batteries poor, which to some extent affects the application of dual-graphite batteries. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes an electrolyte, which is used in a dual-graphite battery, and the battery has good low-temperature cycle performance and improves the battery's adaptability to extreme environments, which is of great significance to promoting the development and application of dual-graphite batteries.

[0005] The invention also provides a method for preparing the electrolyte.

[0006] The present invention also provides a secondary battery.

[0007] The invention also provides an electrical device.

[0008] In a first aspect of the present invention, an electrolyte is provided, comprising a film-forming additive, a wetting additive and an organic mixed solvent comprising a carbonate solvent and a carboxylate solvent, wherein the carbonate solvent comprises a carbonate solvent and a fluorocarbonate solvent, and the carboxylate solvent comprises a carboxylate solvent and a fluorocarboxylate solvent, wherein the volume percentage of the carboxylate solvent in the organic mixed solvent is 20% to 40%; and the wetting additive comprises fluorobenzene and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0009] The electrolyte according to the embodiment of the present invention has at least the following beneficial effects:

[0010] The organic mixed solvent of the electrolyte in the present invention includes carbonate solvents and carboxylate solvents. The carbonate solvents and carboxylate solvents can adjust the electrolyte solvation structure to have better low-temperature ion transport properties. Carbonate solvents have a high solubility for lithium salts and can increase the electrolyte concentration to store more electricity; carboxylate solvents have a low melting point and can optimize Li + The solvation structure of Li + transmission capacity; the fluorinated solvent in the organic mixed solvent can further alleviate the low-temperature solidification phenomenon of the electrolyte and improve the low-temperature ionic conductivity. The wetting additive used in the present invention promotes the wetting of high-concentration electrolyte and electrode and improves the ion conduction at the electrode interface: it can reduce the surface tension of the electrolyte, so that the electrolyte still maintains good wettability to the electrode in a low-temperature environment, and improves the ion conduction capacity of the electrode / electrolyte interface at low temperatures. The film-forming additive used in the present invention helps to form a solid electrolyte membrane with high ionic conductivity, helps to form a solid electrolyte membrane with high ionic conductivity, and improves the low-temperature reaction kinetics of the electrode.

[0011] Therefore, the electrolyte in the present invention has good low-temperature ion transport characteristics, good oxidation stability, and good low-temperature (such as -20°C) cycle performance, which can meet the low-temperature working requirements of 5V high-voltage dual-graphite batteries and greatly improve the battery's cycle stability, significantly inhibit the lithium plating and electrolyte decomposition of the 5V dual-graphite battery during the low-temperature cycle process, improve the battery's adaptability to extreme environments, and is of great significance to promoting the development and application of dual-graphite batteries.

[0012] In some embodiments of the present invention, the mass ratio of fluorobenzene to 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether is 1:(1-10).

[0013] In some embodiments of the present invention, the volume percentage of the carboxylate solvent in the organic mixed solvent is 28-32%, such as 30%.

[0014] In some embodiments of the present invention, the carbonate solvent includes at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate or ethyl methyl carbonate.

[0015] In some embodiments of the present invention, the fluorocarbonate solvent includes at least one of fluoroethylene carbonate, fluoroethyl methyl carbonate or 3,3,3-trifluoropropylene carbonate. Among them, fluoroethyl methyl carbonate, referred to as FEMC, is also known as trifluoroethyl methyl carbonate or methyl trifluoroethyl carbonate.

[0016] In some embodiments of the present invention, the volume percentage of the fluorocarbonate solvent in the carbonate solvent is 15% to 50%, such as 15% to 42%.

[0017] In some embodiments of the present invention, the carboxylate solvent includes at least one of ethyl acetate, methyl propionate, ethyl propionate or γ-valerolactone.

[0018] In some embodiments of the present invention, the fluorocarboxylate solvent includes at least one of ethyl difluoroacetate, ethyl trifluoroacetate, ethyl 3,3,3-trifluoropropyl ester, or methyl trifluoropropionate.

[0019] In some embodiments of the present invention, the volume percentage of the fluorocarboxylate solvent in the carboxylate solvent is 15% to 50%, such as 25% to 45%.

[0020] In some embodiments of the present invention, the mass fraction of the organic mixed solvent in the electrolyte is 70% to 90%.

[0021] In some embodiments of the present invention, the mass fraction of the organic mixed solvent in the electrolyte is 80% to 90%.

[0022] In some embodiments of the present invention, the film-forming additive includes at least one of lithium nitrate, tetramethylfluorouronium hexafluorophosphate, 2-fluoro-1,3-dimethylimidazolium chloride hexafluorophosphate, or bis(tetramethylene)fluoroformamide.

[0023] The film-forming additive used in the present invention can form a SEI film rich in lithium nitride on the surface of the negative electrode. Lithium nitride has high ionic conductivity and can promote Li + Diffusion in SEI increases the interfacial reaction kinetic constant of the negative electrode, reduces the lithium ion transmission resistance, and improves the low-temperature reaction kinetics of the electrode.

[0024] In some embodiments of the present invention, in the electrolyte, the mass fraction of the film-forming additive is 1% to 10%, such as optionally 2% to 7%, specifically 4%.

[0025] In some embodiments of the present invention, in the electrolyte, the mass fraction of the wetting additive is 1% to 3%, specifically 1.8%.

[0026] In some embodiments of the present invention, the electrolyte further comprises a lithium salt.

[0027] In some embodiments of the present invention, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, or lithium bis(fluorosulfonyl)imide.

[0028] Lithium hexafluorophosphate: LiPF6; lithium bis(trifluoromethanesulfonyl)imide: LiTFSI; lithium bis(fluorosulfonyl)imide: LiFSI.

[0029] In some embodiments of the present invention, the concentration of lithium salt in the electrolyte is 0.2 to 5 mol / L, such as 1 to 4 mol / L.

[0030] In some embodiments of the present invention, the concentration of lithium salt in the electrolyte is 2.5 to 3.2 mol / L.

[0031] In a second aspect of the present invention, a method for preparing an electrolyte is provided, comprising the following steps: mixing a preparation raw material containing a film-forming additive, a wetting additive, an organic mixed solvent and a lithium salt to obtain the electrolyte.

[0032] In some embodiments of the present invention, the preparation method comprises the following steps: mixing a film-forming additive, a wetting additive, an organic mixed solvent and a lithium salt to obtain the electrolyte.

[0033] In some embodiments of the present invention, the preparation method comprises the following steps: mixing an organic mixed solvent and a lithium salt, and then mixing with a film-forming additive and a wetting additive to obtain the electrolyte.

[0034] In some embodiments of the present invention, the preparation method comprises the following steps: mixing an organic mixed solvent and a lithium salt to obtain a basic electrolyte, and then mixing with a film-forming additive and a wetting additive to obtain the electrolyte.

[0035] In some embodiments of the present invention, the concentration of lithium salt in the basic electrolyte is 0.2 to 5 mol / L, such as 1.0 to 4.0 mol / L.

[0036] According to a third aspect of the present invention, a secondary battery is provided, comprising the above-mentioned electrolyte.

[0037] In some embodiments of the present invention, the secondary battery comprises a dual graphite battery, the battery comprising a graphite positive electrode and a graphite negative electrode.

[0038] In some embodiments of the present invention, the secondary battery further includes a separator.

[0039] According to a fourth aspect of the present invention, an electric device is provided, comprising the above-mentioned secondary battery, wherein the secondary battery is used as a power source of the electric device. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0041] Figure 1This is a cycle performance diagram of the dual graphite battery of Example 14 of the present invention at 0.1C and -20°C. DETAILED DESCRIPTION

[0042] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0043] The experimental methods in the following examples without specifying specific conditions are generally carried out according to conventional conditions in the art or conditions recommended by the manufacturers; the raw materials and reagents used, unless otherwise specified, are all raw materials and reagents that can be obtained from commercial channels such as conventional markets.

[0044] In the following examples and comparative examples, unless otherwise specified, the carbonate solvent is ethyl methyl carbonate, the fluorocarbonate solvent is methyl trifluoroethyl carbonate, the carboxylate solvent is methyl propionate, and the fluorocarboxylate solvent is methyl trifluoropropionate.

[0045] Example 1

[0046] This embodiment discloses an electrolyte with good low-temperature performance (hereinafter referred to as low-temperature electrolyte), including an organic mixed solvent, a lithium salt and an electrolyte additive (film-forming additive, impregnation additive); the organic mixed solvent is a carbonate solvent and a carboxylate solvent in a volume ratio of 80:20. Among them, the carbonate solvent is a carbonate solvent and a fluorocarbonate solvent in a volume ratio of 85:15, and the carboxylate solvent is a carboxylate solvent and a fluorocarboxylate solvent in a volume ratio of 75:25; the lithium salt is lithium hexafluorophosphate; the film-forming additive is lithium nitrate and tetramethylfluorourea hexafluorophosphate in a mass ratio of 1:1, accounting for 5% of the total mass of the electrolyte; the impregnation additive is fluorobenzene and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in a mass ratio of 1:3, and the impregnation additive accounts for 1% of the total mass of the electrolyte.

[0047] The preparation method of a low-temperature electrolyte comprises: adding a carbonate solvent and a carboxylate solvent into a container in a glove box (argon atmosphere, H2O<0.1ppm, O2<0.1ppm) according to a volume ratio, adding a lithium salt to dissolve to obtain a basic electrolyte with a molar concentration of 3 mol / L; mixing the basic electrolyte and the additive in a mass ratio, and stirring and dissolving to obtain a low-temperature electrolyte.

[0048] This embodiment also discloses a dual-graphite battery, which is a 5V high-voltage dual-graphite battery (design capacity 2300mAh), including the low-temperature electrolyte of this embodiment, and also including a graphite positive electrode, a graphite negative electrode and a separator. The preparation method of the graphite positive electrode includes: mixing and stirring graphite particles, conductive carbon, a binder, and a solvent to obtain a positive electrode slurry and applying it on an aluminum current collector (thickness 12μm) (wherein the mass ratio of graphite particles, conductive carbon, and binder is 9:0.5:0.5), and the positive electrode surface density is 25mg / cm 2 The graphite negative electrode preparation method is as follows: graphite particles, conductive carbon, binder, and solvent NMP are fully mixed and stirred to obtain a positive electrode slurry and coated on a copper current collector (thickness of 6 μm) (wherein the mass ratio of graphite particles, conductive carbon, and binder is 9:0.5:0.5), and the negative electrode surface density is 9 mg / cm 2 The diaphragm is a glass fiber diaphragm (Whatman, thickness is 100 μm). Graphite is purchased from Kejing, 200 mesh; conductive carbon and binder PVDF are both purchased from Kejing.

[0049] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0050] Example 2

[0051] This embodiment discloses a low-temperature electrolyte, which is different from the embodiment 1 only in that the organic mixed solvent in this embodiment is a carbonate solvent and a carboxylate solvent in a volume ratio of 75:25. The components of the carbonate solvent and the carboxylate solvent are the same as those in the embodiment 1, and the other conditions and the electrolyte preparation method are also the same as those in the embodiment 1.

[0052] This embodiment also discloses a dual graphite battery, which is different from the embodiment 1 only in that the low-temperature electrolyte in this embodiment is used to replace the low-temperature electrolyte in the embodiment 1, and the rest is the same as the embodiment 1.

[0053] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0054] Example 3

[0055] This embodiment discloses a low-temperature electrolyte, which is different from the embodiment 1 only in that the organic mixed solvent in this embodiment is a carbonate solvent and a carboxylate solvent in a volume ratio of 70:30. The components of the carbonate solvent and the carboxylate solvent are the same as those in the embodiment 1, and the other conditions and the electrolyte preparation method are also the same as those in the embodiment 1.

[0056] This embodiment also discloses a dual graphite battery, which is different from the embodiment 1 only in that the low-temperature electrolyte in this embodiment is used to replace the low-temperature electrolyte in the embodiment 1, and the rest is the same as the embodiment 1.

[0057] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0058] Example 4

[0059] This embodiment discloses a low-temperature electrolyte, which is different from the embodiment 1 only in that the organic mixed solvent in this embodiment is a carbonate solvent and a carboxylate solvent in a volume ratio of 65:35. The components of the carbonate solvent and the carboxylate solvent are the same as those in the embodiment 1, and the other conditions and the electrolyte preparation method are also the same as those in the embodiment 1.

[0060] This embodiment also discloses a dual graphite battery, which is different from the embodiment 1 only in that the low-temperature electrolyte in this embodiment is used to replace the low-temperature electrolyte in the embodiment 1, and the rest is the same as the embodiment 1.

[0061] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0062] Example 5

[0063] This embodiment discloses a low-temperature electrolyte, which is different from the embodiment 1 only in that the organic mixed solvent in this embodiment is a carbonate solvent and a carboxylate solvent in a volume ratio of 60:40. The components of the carbonate solvent and the carboxylate solvent are the same as those in the embodiment 1, and the other conditions and the electrolyte preparation method are also the same as those in the embodiment 1.

[0064] This embodiment also discloses a dual graphite battery, which is different from the embodiment 1 only in that the low-temperature electrolyte in this embodiment is used to replace the low-temperature electrolyte in the embodiment 1, and the rest is the same as the embodiment 1.

[0065] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0066] Example 6

[0067] This embodiment discloses a low-temperature electrolyte, which is different from the embodiment 3 only in that: the carboxylate solvent in this embodiment is a carboxylate solvent and a fluorocarboxylate solvent in a volume ratio of 85:15; the rest is the same as the embodiment 3.

[0068] This embodiment also discloses a dual graphite battery, which is different from the embodiment 3 only in that the low-temperature electrolyte in this embodiment is used to replace the low-temperature electrolyte in the embodiment 3, and the rest is the same as the embodiment 3.

[0069] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0070] Example 7

[0071] This embodiment discloses a low-temperature electrolyte, which is different from the embodiment 3 only in that: the carboxylate solvent in this embodiment is a carboxylate solvent and a fluorocarboxylate solvent in a volume ratio of 70:30; the rest is the same as the embodiment 3.

[0072] This embodiment also discloses a dual graphite battery, which is different from the embodiment 3 only in that the low-temperature electrolyte in this embodiment is used to replace the low-temperature electrolyte in the embodiment 3, and the rest is the same as the embodiment 3.

[0073] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0074] Example 8

[0075] This embodiment discloses a low-temperature electrolyte, which is different from the embodiment 3 only in that: the carboxylate solvent in this embodiment is a carboxylate solvent and a fluorocarboxylate solvent in a volume ratio of 55:45; the rest is the same as the embodiment 3.

[0076] This embodiment also discloses a dual graphite battery, which is different from the embodiment 3 only in that the low-temperature electrolyte in this embodiment is used to replace the low-temperature electrolyte in the embodiment 3, and the rest is the same as the embodiment 3.

[0077] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0078] Example 9

[0079] This embodiment discloses a low-temperature electrolyte, which is different from Embodiment 7 only in that the carbonate solvent in this embodiment is a carbonate solvent and a fluorocarbonate solvent in a volume ratio of 70:30; the rest is the same as Embodiment 7.

[0080] This embodiment also discloses a dual graphite battery, which is different from Embodiment 7 only in that the low-temperature electrolyte in this embodiment is used to replace the low-temperature electrolyte in Embodiment 7, and the rest is the same as Embodiment 7.

[0081] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0082] Example 10

[0083] This embodiment discloses a low-temperature electrolyte, which is different from Embodiment 7 only in that the carbonate solvent in this embodiment is a carbonate solvent and a fluorocarbonate solvent in a volume ratio of 60:40; the rest is the same as Embodiment 7.

[0084] This embodiment also discloses a dual graphite battery, which is different from Embodiment 7 only in that the low-temperature electrolyte in this embodiment is used to replace the low-temperature electrolyte in Embodiment 7, and the rest is the same as Embodiment 7.

[0085] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0086] Embodiment 11

[0087] This embodiment discloses a low-temperature electrolyte, which is different from Embodiment 7 only in that the carbonate solvent in this embodiment is a carbonate solvent and a fluorocarbonate solvent in a volume ratio of 50:50; the rest is the same as Embodiment 7.

[0088] This embodiment also discloses a dual graphite battery, which is different from Embodiment 7 only in that the low-temperature electrolyte in this embodiment is used to replace the low-temperature electrolyte in Embodiment 7, and the rest is the same as Embodiment 7.

[0089] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0090] Example 12

[0091] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 9 only in that: in this embodiment, the film-forming additives are lithium nitrate, tetramethylfluorouronium hexafluorophosphate, 2-fluoro-1,3-dimethylimidazolium chloride hexafluorophosphate and bis(tetramethylene)fluoroformamide in a mass ratio of 0.5:1:0.6:0.2, accounting for 1.5% of the total mass of the electrolyte; the wetting additive component and its content, the organic mixed solvent component, the lithium salt component and its content in the basic electrolyte are the same as in Embodiment 9, and other conditions and electrolyte preparation method are also the same as in Embodiment 9.

[0092] This embodiment also discloses a dual graphite battery, which is different from Embodiment 9 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 9, and the rest is the same as Embodiment 9.

[0093] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0094] Embodiment 13

[0095] This embodiment discloses a low-temperature electrolyte, which is different from Embodiment 9 only in that: the film-forming additives in this embodiment are lithium nitrate, tetramethylfluorouronium hexafluorophosphate, 2-fluoro-1,3-dimethylimidazolium chloride hexafluorophosphate and bis(tetramethylene)fluoroformamide in a mass ratio of 0.5:1:0.6:0.2, accounting for 2.5% of the total mass of the electrolyte; the rest is the same as Embodiment 9.

[0096] This embodiment also discloses a dual graphite battery, which is different from Embodiment 9 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 9, and the rest is the same as Embodiment 9.

[0097] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0098] Embodiment 14

[0099] This embodiment discloses a low-temperature electrolyte, which is different from Embodiment 9 only in that: the film-forming additives in this embodiment are lithium nitrate, tetramethylfluorouronium hexafluorophosphate, 2-fluoro-1,3-dimethylimidazolium chloride hexafluorophosphate and bis(tetramethylene)fluoroformamide in a mass ratio of 0.5:1:0.6:0.2, accounting for 4% of the total mass of the electrolyte; the rest is the same as Embodiment 9.

[0100] This embodiment also discloses a dual graphite battery, which is different from Embodiment 9 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 9, and the rest is the same as Embodiment 9.

[0101] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0102] Embodiment 15

[0103] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 9 only in that: in this embodiment, the film-forming additives are lithium nitrate, tetramethylfluorouronium hexafluorophosphate, 2-fluoro-1,3-dimethylimidazolium chloride hexafluorophosphate and bis(tetramethylene)fluoroformamide in a mass ratio of 0.5:1:0.6:0.2, accounting for 7% of the total mass of the electrolyte; the wetting additive component and its content, the organic mixed solvent component, the lithium salt component and its content in the basic electrolyte are the same as in Embodiment 9, and other conditions and electrolyte preparation method are also the same as in Embodiment 9.

[0104] This embodiment also discloses a dual graphite battery, which is different from Embodiment 9 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 9, and the rest is the same as Embodiment 9.

[0105] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0106] Example 16

[0107] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 9 only in that: in this embodiment, the film-forming additives are lithium nitrate, tetramethylfluorouronium hexafluorophosphate, 2-fluoro-1,3-dimethylimidazolium chloride hexafluorophosphate and bis(tetramethylene)fluoroformamide in a mass ratio of 0.5:1:0.6:0.2, accounting for 10% of the total mass of the electrolyte; the wetting additive component and its content, the organic mixed solvent component, the lithium salt component and its content in the basic electrolyte are the same as in Embodiment 9, and other conditions and the electrolyte preparation method are also the same as in Embodiment 9.

[0108] This embodiment also discloses a dual graphite battery, which is different from Embodiment 9 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 9, and the rest is the same as Embodiment 9.

[0109] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0110] Embodiment 17

[0111] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 9 only in that: in this embodiment, the film-forming additive is lithium nitrate, tetramethylfluorouronium hexafluorophosphate and bis(tetramethylene)fluoroformamide in a mass ratio of 0.8:1:0.4, accounting for 4% of the total mass of the electrolyte; the wetting additive component and its content, the organic mixed solvent component, the lithium salt component and its content in the basic electrolyte are the same as in Embodiment 9, and other conditions and electrolyte preparation method are also the same as in Embodiment 9.

[0112] This embodiment also discloses a dual graphite battery, which is different from Embodiment 9 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 9, and the rest is the same as Embodiment 9.

[0113] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0114] Embodiment 18

[0115] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 9 only in that: in this embodiment, the film-forming additive is lithium nitrate, 2-fluoro-1,3-dimethylimidazolium chloride hexafluorophosphate and bis(tetramethylene)fluoroformamide in a mass ratio of 1:1.5:0.2, accounting for 4% of the total mass of the electrolyte; the wetting additive component and its content, the organic mixed solvent component, the lithium salt component and its content in the basic electrolyte are the same as in Embodiment 9, and other conditions and electrolyte preparation method are also the same as in Embodiment 9.

[0116] This embodiment also discloses a dual graphite battery, which is different from Embodiment 9 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 9, and the rest is the same as Embodiment 9.

[0117] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0118] Embodiment 19

[0119] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 9 only in that: in this embodiment, the film-forming additive is tetramethylfluorouronium hexafluorophosphate, 2-fluoro-1,3-dimethylimidazolium chloride hexafluorophosphate and bis(tetramethylene)fluoroformamide in a mass ratio of 0.9:0.5:0.3, accounting for 4% of the total mass of the electrolyte; the wetting additive component and its content, the organic mixed solvent component, the lithium salt component and its content in the basic electrolyte are the same as in Embodiment 9, and other conditions and electrolyte preparation method are also the same as in Embodiment 9.

[0120] This embodiment also discloses a dual graphite battery, which is different from Embodiment 9 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 9, and the rest is the same as Embodiment 9.

[0121] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0122] Embodiment 20

[0123] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 9 only in that: in this embodiment, the film-forming additives are lithium nitrate, tetramethylfluorouronium hexafluorophosphate and 2-fluoro-1,3-dimethylimidazolium chloride hexafluorophosphate in a mass ratio of 0.6:0.8:1.1, accounting for 4% of the total mass of the electrolyte; the wetting additive component and its content, the organic mixed solvent component, the lithium salt component and its content in the basic electrolyte are the same as in Embodiment 9, and other conditions and electrolyte preparation methods are also the same as in Embodiment 9.

[0124] This embodiment also discloses a dual graphite battery, which is different from Embodiment 9 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 9, and the rest is the same as Embodiment 9.

[0125] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0126] Embodiment 21

[0127] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 9 only in that: in this embodiment, the film-forming additive is lithium nitrate and tetramethylfluorouronium hexafluorophosphate in a mass ratio of 1:1.7, accounting for 4% of the total mass of the electrolyte; the wetting additive component and its content, the organic mixed solvent component, the lithium salt component and its content in the basic electrolyte are the same as in Embodiment 9, and other conditions and electrolyte preparation methods are also the same as in Embodiment 9.

[0128] This embodiment also discloses a dual graphite battery, which is different from Embodiment 9 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 9, and the rest is the same as Embodiment 9.

[0129] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0130] Embodiment 22

[0131] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 9 only in that: in this embodiment, the film-forming additive is lithium nitrate and 2-fluoro-1,3-dimethylimidazolium chloride hexafluorophosphate in a mass ratio of 0.6:1, accounting for 4% of the total mass of the electrolyte; the wetting additive component and its content, the organic mixed solvent component, the lithium salt component and its content in the basic electrolyte are the same as in Embodiment 9, and other conditions and electrolyte preparation methods are also the same as in Embodiment 9.

[0132] This embodiment also discloses a dual graphite battery, which is different from Embodiment 9 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 9, and the rest is the same as Embodiment 9.

[0133] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0134] Embodiment 23

[0135] This embodiment discloses a low-temperature electrolyte, which differs from Example 9 only in that: the film-forming additive in this embodiment is lithium nitrate and bis(tetramethylene)fluoroformamide in a mass ratio of 0.9:1.9, accounting for 4% of the total mass of the electrolyte; the wetting additive component and its content, the organic mixed solvent component, the lithium salt component and its content in the basic electrolyte are the same as in Example 9, and other conditions and electrolyte preparation methods are also the same as in Example 9.

[0136] This embodiment also discloses a dual graphite battery, which is different from Embodiment 9 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 9, and the rest is the same as Embodiment 9.

[0137] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0138] Embodiment 24

[0139] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 9 only in that: the film-forming additive in this embodiment is tetramethylfluorouronium hexafluorophosphate and bis(tetramethylene)fluoroformamide in a mass ratio of 2:1, accounting for 4% of the total mass of the electrolyte; the wetting additive component and its content, the organic mixed solvent component, the lithium salt component and its content in the basic electrolyte are the same as those in Embodiment 9, and other conditions and electrolyte preparation methods are also the same as those in Embodiment 9.

[0140] This embodiment also discloses a dual graphite battery, which is different from Embodiment 9 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 9, and the rest is the same as Embodiment 9.

[0141] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0142] Embodiment 25

[0143] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 9 only in that: in this embodiment, the film-forming additive is 2-fluoro-1,3-dimethylimidazolium chloride hexafluorophosphate and bis(tetramethylene)fluoroformamide in a mass ratio of 2.5:1.5, accounting for 4% of the total mass of the electrolyte; the wetting additive component and its content, the organic mixed solvent component, the lithium salt component and its content in the basic electrolyte are the same as in Embodiment 9, and other conditions and electrolyte preparation method are also the same as in Embodiment 9.

[0144] This embodiment also discloses a dual graphite battery, which is different from Embodiment 9 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 9, and the rest is the same as Embodiment 9.

[0145] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0146] Embodiment 26

[0147] This embodiment discloses a low-temperature electrolyte, which differs from Example 13 only in that: the wetting additive in this embodiment is fluorobenzene and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in a mass ratio of 1:3, and the wetting additive accounts for 1.8% of the total mass of the electrolyte; the film-forming additive component and its content, the organic mixed solvent component, the lithium salt component and its content in the basic electrolyte are the same as in Example 13, and other conditions and electrolyte preparation methods are also the same as in Example 13.

[0148] This embodiment also discloses a dual graphite battery, which is different from Embodiment 13 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 13, and the rest is the same as Embodiment 13.

[0149] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0150] Embodiment 27

[0151] This embodiment discloses a low-temperature electrolyte, which differs from Example 13 only in that: the wetting additive in this embodiment is fluorobenzene and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in a mass ratio of 1:3, and the wetting additive accounts for 3% of the total mass of the electrolyte; the film-forming additive component and its content, the organic mixed solvent component, the lithium salt component and its content in the basic electrolyte are the same as Example 13, and other conditions and electrolyte preparation methods are also the same as Example 13.

[0152] This embodiment also discloses a dual graphite battery, which is different from Embodiment 13 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 13, and the rest is the same as Embodiment 13.

[0153] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0154] Embodiment 28

[0155] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 12 only in that lithium bis(trifluoromethanesulfonyl)imide is used in this embodiment to replace the lithium hexafluorophosphate in Embodiment 12.

[0156] This embodiment also discloses a dual graphite battery, which is different from Embodiment 12 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 12, and the rest is the same as Embodiment 12.

[0157] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0158] Embodiment 29

[0159] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 13 only in that lithium bis(trifluoromethanesulfonyl)imide is used in this embodiment to replace the lithium hexafluorophosphate in Embodiment 13.

[0160] This embodiment also discloses a dual graphite battery, which is different from Embodiment 13 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 13, and the rest is the same as Embodiment 13.

[0161] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0162] Embodiment 30

[0163] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 14 only in that lithium bis(trifluoromethanesulfonyl)imide is used in this embodiment to replace the lithium hexafluorophosphate in Embodiment 14.

[0164] This embodiment also discloses a dual graphite battery, which is different from Example 14 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Example 14, and the rest is the same as Example 14.

[0165] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0166] Embodiment 31

[0167] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 15 only in that lithium bis(trifluoromethanesulfonyl)imide is used in this embodiment to replace the lithium hexafluorophosphate in Embodiment 15.

[0168] This embodiment also discloses a dual graphite battery, which is different from Embodiment 15 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 15, and the rest is the same as Embodiment 15.

[0169] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0170] Embodiment 32

[0171] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 16 only in that lithium bis(trifluoromethanesulfonyl)imide is used in this embodiment to replace the lithium hexafluorophosphate in Embodiment 16.

[0172] This embodiment also discloses a dual graphite battery, which is different from Embodiment 16 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 16, and the rest is the same as Embodiment 16.

[0173] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0174] Embodiment 33

[0175] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 12 only in that lithium bis(fluorosulfonyl)imide is used in this embodiment to replace the lithium hexafluorophosphate in Embodiment 12.

[0176] This embodiment also discloses a dual graphite battery, which is different from Embodiment 12 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 12, and the rest is the same as Embodiment 12.

[0177] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0178] Embodiment 34

[0179] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 13 only in that lithium bis(fluorosulfonyl)imide is used in this embodiment to replace the lithium hexafluorophosphate in Embodiment 13.

[0180] This embodiment also discloses a dual graphite battery, which is different from Embodiment 13 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 13, and the rest is the same as Embodiment 13.

[0181] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0182] Embodiment 35

[0183] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 14 only in that lithium bis(fluorosulfonyl)imide is used in this embodiment to replace the lithium hexafluorophosphate in Embodiment 14.

[0184] This embodiment also discloses a dual graphite battery, which is different from Example 14 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Example 14, and the rest is the same as Example 14.

[0185] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0186] Embodiment 36

[0187] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 15 only in that lithium bis(fluorosulfonyl)imide is used in this embodiment to replace the lithium hexafluorophosphate in Embodiment 15.

[0188] This embodiment also discloses a dual graphite battery, which is different from Embodiment 15 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 15, and the rest is the same as Embodiment 15.

[0189] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0190] Embodiment 37

[0191] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 16 only in that lithium bis(fluorosulfonyl)imide is used in this embodiment to replace the lithium hexafluorophosphate in Embodiment 16.

[0192] This embodiment also discloses a dual graphite battery, which is different from Embodiment 16 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 16, and the rest is the same as Embodiment 16.

[0193] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0194] Embodiment 38

[0195] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 14 only in that, during the preparation of the low-temperature electrolyte in this embodiment: the concentration of lithium hexafluorophosphate in the base electrolyte is 1 mol / L.

[0196] This embodiment also discloses a dual graphite battery, which is different from Example 14 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Example 14, and the rest is the same as Example 14.

[0197] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0198] Embodiment 39

[0199] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 14 only in that, during the preparation of the low-temperature electrolyte in this embodiment: the concentration of lithium hexafluorophosphate in the base electrolyte is 2 mol / L.

[0200] This embodiment also discloses a dual graphite battery, which is different from Example 14 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Example 14, and the rest is the same as Example 14.

[0201] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0202] Embodiment 40

[0203] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 14 only in that, during the preparation of the low-temperature electrolyte in this embodiment: the concentration of lithium hexafluorophosphate in the base electrolyte is 4 mol / L.

[0204] This embodiment also discloses a dual graphite battery, which is different from Example 14 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Example 14, and the rest is the same as Example 14.

[0205] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0206] Embodiment 41

[0207] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 30 only in that, during the preparation of the low-temperature electrolyte in this embodiment: the concentration of lithium bis(trifluoromethanesulfonyl)imide in the base electrolyte is 1 mol / L.

[0208] This embodiment also discloses a dual graphite battery, which differs from Embodiment 30 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 30, and the rest is the same as Embodiment 30.

[0209] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0210] Embodiment 42

[0211] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 30 only in that, during the preparation of the low-temperature electrolyte in this embodiment: the concentration of lithium bis(trifluoromethanesulfonyl)imide in the base electrolyte is 2 mol / L.

[0212] This embodiment also discloses a dual graphite battery, which differs from Embodiment 30 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 30, and the rest is the same as Embodiment 30.

[0213] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0214] Embodiment 43

[0215] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 30 only in that, during the preparation of the low-temperature electrolyte in this embodiment: the concentration of lithium bis(trifluoromethanesulfonyl)imide in the base electrolyte is 4 mol / L.

[0216] This embodiment also discloses a dual graphite battery, which differs from Embodiment 30 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Embodiment 30, and the rest is the same as Embodiment 30.

[0217] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0218] Embodiment 44

[0219] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 35 only in that, during the preparation of the low-temperature electrolyte in this embodiment: the concentration of lithium bis(fluorosulfonyl)imide in the base electrolyte is 1 mol / L.

[0220] This embodiment also discloses a dual graphite battery, which differs from Example 35 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Example 35, and the rest is the same as Example 35.

[0221] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0222] Embodiment 45

[0223] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 35 only in that, during the preparation of the low-temperature electrolyte in this embodiment: the concentration of lithium bis(fluorosulfonyl)imide in the base electrolyte is 2 mol / L.

[0224] This embodiment also discloses a dual graphite battery, which differs from Example 35 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Example 35, and the rest is the same as Example 35.

[0225] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0226] Embodiment 46

[0227] This embodiment discloses a low-temperature electrolyte, which differs from Embodiment 35 only in that, during the preparation of the low-temperature electrolyte in this embodiment: the concentration of lithium bis(fluorosulfonyl)imide in the base electrolyte is 4 mol / L.

[0228] This embodiment also discloses a dual graphite battery, which differs from Example 35 only in that the low-temperature electrolyte in this embodiment is used instead of the low-temperature electrolyte in Example 35, and the rest is the same as Example 35.

[0229] This embodiment also discloses an electrical device, including the dual graphite battery of this embodiment, wherein the dual graphite battery is used as a power source for the electrical device.

[0230] Comparative Example 1

[0231] This comparative example discloses a low-temperature electrolyte, which differs from Example 1 only in that: this comparative example does not contain a carboxylic acid ester solvent. Specifically, the low-temperature electrolyte in this comparative example includes an organic mixed solvent, a lithium salt and an electrolyte additive (film-forming additive, impregnation additive). Among them, the organic mixed solvent is a carbonate solvent and a fluorocarbonate solvent in a volume ratio of 85:15, and the lithium salt is lithium hexafluorophosphate; the film-forming additive is lithium nitrate and tetramethylfluorourea hexafluorophosphate in a mass ratio of 1:1, accounting for 5% of the total mass of the electrolyte; the impregnation additive is fluorobenzene and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in a mass ratio of 1:3, and the impregnation additive accounts for 1% of the total mass of the electrolyte.

[0232] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 1.

[0233] Comparative Example 2

[0234] This comparative example discloses a low-temperature electrolyte, which differs from Example 1 only in that: this comparative example does not contain carbonate solvents. Specifically, the low-temperature electrolyte in this comparative example includes an organic mixed solvent, a lithium salt and an electrolyte additive (film-forming additive, impregnation additive). Among them, the organic mixed solvent is a carboxylate solvent and a fluorocarboxylate solvent in a volume ratio of 75:25; the lithium salt is lithium hexafluorophosphate; the film-forming additive is lithium nitrate and tetramethylfluorourea hexafluorophosphate in a mass ratio of 1:1, accounting for 5% of the total mass of the electrolyte; the impregnation additive is fluorobenzene and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in a mass ratio of 1:3, and the impregnation additive accounts for 1% of the total mass of the electrolyte.

[0235] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 1.

[0236] Comparative Example 3

[0237] This comparative example discloses a low-temperature electrolyte, which differs from Example 3 only in that: this comparative example does not contain a fluorinated carboxylate solvent. Specifically, the low-temperature electrolyte in this comparative example includes an organic mixed solvent, a lithium salt and an electrolyte additive (film-forming additive, impregnation additive). The organic mixed solvent is a carbonate solvent and a carboxylate solvent in a volume ratio of 70:30, wherein the carbonate solvent is a carbonate solvent and a fluorinated carbonate solvent in a volume ratio of 85:15; the lithium salt is lithium hexafluorophosphate; the film-forming additive is lithium nitrate and tetramethylfluorourea hexafluorophosphate in a mass ratio of 1:1, accounting for 5% of the total mass of the electrolyte; the impregnation additive is fluorobenzene and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in a mass ratio of 1:3, and the impregnation additive accounts for 1% of the total mass of the electrolyte.

[0238] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 3.

[0239] Comparative Example 4

[0240] This comparative example discloses a low-temperature electrolyte, which differs from Example 7 only in that: this comparative example does not contain a fluorinated carbonate solvent. Specifically, the low-temperature electrolyte in this comparative example includes an organic mixed solvent, a lithium salt and an electrolyte additive (film-forming additive, impregnation additive). The organic mixed solvent is a carbonate solvent and a carboxylate solvent in a volume ratio of 70:30, wherein the carboxylate solvent is a carboxylate solvent and a fluorinated carboxylate solvent in a volume ratio of 70:30; the lithium salt is lithium hexafluorophosphate; the film-forming additive is lithium nitrate and tetramethylfluorourea hexafluorophosphate in a mass ratio of 1:1, accounting for 5% of the total mass of the electrolyte; the impregnation additive is fluorobenzene and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in a mass ratio of 1:3, and the impregnation additive accounts for 1% of the total mass of the electrolyte.

[0241] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 7.

[0242] Comparative Example 5

[0243] This comparative example discloses a low-temperature electrolyte, which differs from Example 9 only in that: this comparative example does not contain a film-forming additive, specifically, the low-temperature electrolyte in this comparative example includes an organic mixed solvent, a lithium salt and an impregnation additive. The organic mixed solvent is a carbonate solvent and a carboxylate solvent in a volume ratio of 70:30, wherein the carbonate solvent is a carbonate solvent and a fluorocarbonate solvent in a volume ratio of 70:30, and the carboxylate solvent is a carboxylate solvent and a fluorocarboxylate solvent in a volume ratio of 70:30; the lithium salt is lithium hexafluorophosphate; the impregnation additive is an impregnation additive of fluorobenzene and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in a mass ratio of 1:3, accounting for 1% of the total mass of the electrolyte.

[0244] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 9.

[0245] Comparative Example 6

[0246] This comparative example discloses a low-temperature electrolyte, which differs from Example 13 only in that: this comparative example does not contain a wetting additive, specifically, the low-temperature electrolyte in this comparative example includes an organic mixed solvent, a lithium salt and a film-forming additive. The organic mixed solvent is a carbonate solvent and a carboxylate solvent in a volume ratio of 70:30, wherein the carbonate solvent is a carbonate solvent and a fluorocarbonate solvent in a volume ratio of 70:30, and the carboxylate solvent is a carboxylate solvent and a fluorocarboxylate solvent in a volume ratio of 70:30; the lithium salt is lithium hexafluorophosphate; the additive is a film-forming additive of lithium nitrate, tetramethylfluorourea hexafluorophosphate, 2-fluoro-1,3-dimethylimidazolium chloride hexafluorophosphate and bis(tetramethylene)fluoroformamide in a mass ratio of 0.5:1:0.6:0.2, accounting for 2.5% of the total mass of the electrolyte.

[0247] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 13.

[0248] Comparative Example 7

[0249] This comparative example discloses a low-temperature electrolyte, which differs from comparative example 1 only in that lithium bis(trifluoromethanesulfonyl)imide is used in this comparative example to replace the lithium hexafluorophosphate in comparative example 1.

[0250] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 1.

[0251] Comparative Example 8

[0252] This comparative example discloses a low-temperature electrolyte, which differs from comparative example 2 only in that lithium bis(trifluoromethanesulfonyl)imide is used in this comparative example to replace the lithium hexafluorophosphate in comparative example 2.

[0253] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 1.

[0254] Comparative Example 9

[0255] This comparative example discloses a low-temperature electrolyte, which differs from comparative example 3 only in that lithium bis(trifluoromethanesulfonyl)imide is used in this comparative example to replace the lithium hexafluorophosphate in comparative example 3.

[0256] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 1.

[0257] Comparative Example 10

[0258] This comparative example discloses a low-temperature electrolyte, which differs from comparative example 4 only in that lithium bis(trifluoromethanesulfonyl)imide is used in this comparative example to replace the lithium hexafluorophosphate in comparative example 4.

[0259] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 1.

[0260] Comparative Example 11

[0261] This comparative example discloses a low-temperature electrolyte, which differs from comparative example 5 only in that lithium bis(trifluoromethanesulfonyl)imide is used in this comparative example to replace the lithium hexafluorophosphate in comparative example 5.

[0262] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 1.

[0263] Comparative Example 12

[0264] This comparative example discloses a low-temperature electrolyte, which differs from comparative example 6 only in that lithium bis(trifluoromethanesulfonyl)imide is used in this comparative example to replace the lithium hexafluorophosphate in comparative example 6.

[0265] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 1.

[0266] Comparative Example 13

[0267] This comparative example discloses a low-temperature electrolyte, which differs from comparative example 1 only in that lithium bis(fluorosulfonyl)imide is used in this comparative example to replace the lithium hexafluorophosphate in comparative example 1.

[0268] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 1.

[0269] Comparative Example 14

[0270] This comparative example discloses a low-temperature electrolyte, which differs from comparative example 2 only in that lithium bis(fluorosulfonyl)imide is used in this comparative example to replace the lithium hexafluorophosphate in comparative example 2.

[0271] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 1.

[0272] Comparative Example 15

[0273] This comparative example discloses a low-temperature electrolyte, which differs from comparative example 3 only in that lithium bis(fluorosulfonyl)imide is used in this comparative example to replace the lithium hexafluorophosphate in comparative example 3.

[0274] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 1.

[0275] Comparative Example 16

[0276] This comparative example discloses a low-temperature electrolyte, which differs from comparative example 4 only in that lithium bis(fluorosulfonyl)imide is used in this comparative example to replace the lithium hexafluorophosphate in comparative example 4.

[0277] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 1.

[0278] Comparative Example 17

[0279] This comparative example discloses a low-temperature electrolyte, which differs from comparative example 5 only in that lithium bis(fluorosulfonyl)imide is used in this comparative example to replace the lithium hexafluorophosphate in comparative example 5.

[0280] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 1.

[0281] Comparative Example 18

[0282] This comparative example discloses a low-temperature electrolyte, which differs from comparative example 6 only in that lithium bis(fluorosulfonyl)imide is used in this comparative example to replace the lithium hexafluorophosphate in comparative example 6.

[0283] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 1.

[0284] Comparative Example 19

[0285] This comparative example discloses a low-temperature electrolyte, including an organic mixed solvent, a lithium salt and an electrolyte additive. The organic mixed solvent is a carbonate solvent and a fluorocarbonate solvent in a volume ratio of 85:15, and the lithium salt is lithium hexafluorophosphate; the film-forming additive is vinylene carbonate, accounting for 2% of the total mass of the electrolyte; the impregnation additive is fluorobenzene and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in a mass ratio of 1:3, and the impregnation additive accounts for 1% of the total mass of the electrolyte.

[0286] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 1.

[0287] Comparative Example 20

[0288] This comparative example discloses a low-temperature electrolyte, including an organic mixed solvent, a lithium salt and an electrolyte additive. The organic mixed solvent is a carbonate solvent and a fluorocarbonate solvent in a volume ratio of 85:15, and the lithium salt is lithium hexafluorophosphate; the film-forming additive is vinyl sulfate, accounting for 1% of the total mass of the electrolyte; the wetting additive is fluorobenzene and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in a mass ratio of 1:3, and the wetting additive accounts for 1% of the total mass of the electrolyte.

[0289] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 1.

[0290] Comparative Example 21

[0291] This comparative example discloses a low-temperature electrolyte, including an organic mixed solvent, a lithium salt and an electrolyte additive. The organic mixed solvent is a carbonate solvent and a fluorocarbonate solvent in a volume ratio of 85:15, and the lithium salt is lithium hexafluorophosphate; the film-forming additive is lithium nitrate and tetramethylfluorourea hexafluorophosphate in a mass ratio of 1:1, accounting for 5% of the total mass of the electrolyte; the wetting additive is fluorobenzene, and the wetting additive accounts for 1% of the total mass of the electrolyte.

[0292] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 1.

[0293] Comparative Example 22

[0294] This comparative example discloses a low-temperature electrolyte, including an organic mixed solvent, a lithium salt and an electrolyte additive. The organic mixed solvent is a carbonate solvent and a fluorocarbonate solvent in a volume ratio of 85:15, and the lithium salt is lithium hexafluorophosphate; the film-forming additive is lithium nitrate and tetramethylfluorourea hexafluorophosphate in a mass ratio of 1:1, accounting for 5% of the total mass of the electrolyte; the wetting additive is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and the wetting additive accounts for 1% of the total mass of the electrolyte.

[0295] This comparative example also discloses a dual-graphite battery, comprising the low-temperature electrolyte of this comparative example, and also comprising a graphite positive electrode, a graphite negative electrode and a separator. The graphite positive electrode, the graphite negative electrode and the separator are the same as those in Example 1.

[0296] The preparation method of the above comparative low-temperature electrolyte comprises: adding an organic solvent into a container in a glove box (argon atmosphere, H2O<0.1ppm, O2<0.1ppm) by volume ratio, adding a lithium salt to dissolve to obtain a basic electrolyte with a molar concentration of 3 mol / L; mixing the basic electrolyte and the additive uniformly by mass ratio, and stirring and dissolving to obtain a low-temperature electrolyte.

[0297] Test example

[0298] This test example performs performance tests on the batteries of various embodiments and comparative examples, specifically including:

[0299] Cycle test, test method: at room temperature, first charge and discharge the battery for five cycles at 0.2C rate and 3-5V charge and discharge voltage, then charge and discharge the battery for five cycles at 0.5C rate and 3-5V charge and discharge voltage, and finally cycle the battery at -20°C at 0.1C rate and 3-5V charge and discharge voltage (based on the 11th cycle capacity, the test is stopped when the capacity retention rate is 80%, and the cycle life is counted). The battery test results of the embodiment and comparative example are shown in Table 1 below.

[0300] 1) The battery performance test results obtained with different organic mixed solvents are shown in Table 1:

[0301] Table 1

[0302]

[0303]

[0304] Compared with Comparative Example 1, Examples 1 to 5 added carboxylic acid ester solvents to increase the Li +Ionic conductivity is beneficial to the capacity and cycle performance of the dual graphite battery; compared with Comparative Example 2, Examples 1 to 5 add carbonate solvents to improve the oxidation resistance of the electrolyte and slow down the battery capacity decay; preferably, the battery performance can be further optimized by adjusting the proportion of carboxylate solvents in the electrolyte.

[0305] Compared with Comparative Example 3, Examples 6 to 8 added a fluorinated carboxylate solvent, and compared with Comparative Example 4, Examples 9 to 11 added a fluorinated carbonate solvent. Both modification methods can improve the oxidation stability of the electrolyte, while reducing the melting point of the electrolyte, improving the performance of the electrolyte at low temperatures, and thus improving the battery performance. Preferably, the ratio of the fluorinated carboxylate or fluorinated carbonate in the electrolyte can be adjusted to affect the battery performance, and the battery performance can be further optimized.

[0306] 2) The battery performance test results obtained with different lithium salt types are shown in Table 2, where the cycle performance results of the battery in Example 14 are shown in Figure 1 As shown:

[0307] Table 2

[0308]

[0309]

[0310] Examples 12 to 25 added different proportions of film-forming additives compared to Comparative Example 5. It is not difficult to find that the introduction of film-forming additives significantly improves the capacity and cycle performance of the battery at low temperatures; at the same time, although the combination of different additives will make the battery show different low-temperature performance, they are all better than Comparative Example 5, which strongly confirms the effectiveness of the film-forming additives and the wetting additives in synergistically improving the low-temperature performance of the dual-graphite battery.

[0311] 3) The battery performance test results obtained with different contents of the wetting additives are shown in Table 3:

[0312] Table 3

[0313]

[0314] Compared with Comparative Example 6, Examples 13 and 26-27 add different proportions of wetting additives, which is beneficial to ion conduction between the electrolyte and the electrode at low temperatures, reduces the interface reaction impedance, and thus improves the low-temperature performance of the battery.

[0315] As can be seen from Tables 1 to 3, the low-temperature reversible capacity and cycle life of the dual-graphite battery using the electrolyte described in the embodiment are much higher than those of the dual-graphite battery using the electrolyte of the comparative example. Further, by optimizing the solvent, additive components and proportions, the low-temperature cycle life of the dual-graphite battery can be as high as 237 cycles or more.

[0316] 4) The battery performance test results obtained with different lithium salt types are shown in Table 4:

[0317] Table 4

[0318]

[0319]

[0320] From the comparison of Tables 1 to 4, it can be seen that the battery of the embodiment is much better than the dual-graphite battery using the electrolyte described in Comparative Examples 1 to 6. Comparative Examples 7 to 18 compared with Comparative Examples 1 to 6 show that simply changing the lithium salt will not significantly optimize the low-temperature performance of the dual-graphite battery. The above comparison fully illustrates the advantages and effects of the technical solution of the present invention and its applicability to low-temperature dual-graphite batteries.

[0321] 5) The battery performance test results obtained with different lithium salt concentrations are shown in Table 5:

[0322] Table 5

[0323]

[0324]

[0325] From the data in Tables 4 and 5, it can be seen that changing the electrolyte concentration will affect the battery performance to a certain extent. Since the electrolyte is the power carrier of the dual-graphite battery, increasing the lithium salt concentration can increase the battery capacity and improve the battery cycle performance; compared with the optimal electrolyte concentration (such as 1-4 mol / L), when the electrolyte concentration is too high, the electrolyte solidification point increases and the viscosity increases at low temperatures, which is not conducive to the full play of the battery cycle performance.

[0326] If there is no special explanation, the actual meaning of "about" in the present invention is that the error is allowed within the range of ±2%, for example, about 100 is actually 100±2%×100. The "normal temperature" and "room temperature" in the present invention, if there is no special explanation, are about 20 to 30°C. The "between" in the present invention includes the number itself, for example, "between 2 and 3" includes the endpoint values ​​2 and 3.

[0327] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. An electrolyte, characterized in that: The invention comprises a film-forming additive, a wetting additive and an organic mixed solvent comprising a carbonate solvent and a carboxylate solvent, wherein the carbonate solvent comprises a carbonate solvent and a fluorocarbonate solvent, and the carboxylate solvent comprises a carboxylate solvent and a fluorocarboxylate solvent, wherein the volume percentage of the carboxylate solvent in the organic mixed solvent is 20% to 40%; and the wetting additive comprises fluorobenzene and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

2. The electrolyte according to claim 1, characterized in that The carbonate solvent includes at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate or ethyl methyl carbonate; or / and, the fluorocarbonate solvent includes at least one of fluoroethylene carbonate, fluoroethyl methyl carbonate or 3,3,3-trifluoropropylene carbonate; or / and, the volume percentage of the fluorocarbonate solvent in the carbonate solvent is 15% to 50%.

3. The electrolyte according to claim 1, characterized in that The carboxylate solvent includes at least one of ethyl acetate, methyl propionate, ethyl propionate or γ-valerolactone; or / and, the fluorocarboxylate solvent includes at least one of ethyl difluoroacetate, ethyl trifluoroacetate, ethyl 3,3,3-trifluoropropyl or methyl trifluoropropionate; or / and, the volume percentage of the fluorocarboxylate solvent in the carboxylate solvent is 15% to 50%; Preferably, the mass fraction of the organic mixed solvent in the electrolyte is 70% to 90%; preferably, the mass fraction of the organic mixed solvent in the electrolyte is 80% to 90%.

4. The electrolyte according to claim 1, characterized in that The film-forming additive includes at least one of lithium nitrate, tetramethylfluorourea hexafluorophosphate, 2-fluoro-1,3-dimethylimidazolium chloride hexafluorophosphate or bis(tetramethylene)fluoroformamide; Preferably, in the electrolyte, the mass fraction of the film-forming additive is 1% to 10%.

5. The electrolyte according to claim 1, characterized in that In the electrolyte, the mass fraction of the wetting additive is 1% to 3%.

6. The electrolyte according to claim 1, characterized in that The electrolyte also includes a lithium salt; Preferably, the lithium salt comprises at least one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl imide) or lithium bis(fluorosulfonyl imide); Preferably, in the electrolyte, the concentration of lithium salt is 0.2-5 mol / L.

7. A method for preparing an electrolyte, characterized in that: The method comprises the following steps: mixing raw materials containing film-forming additives, wetting additives, organic mixed solvents and lithium salts to obtain the electrolyte.

8. A secondary battery, characterized in that: The invention comprises the electrolyte described in any one of claims 1 to 6 or the electrolyte prepared by the method described in claim 7.

9. The secondary battery according to claim 8, characterized in that: The secondary battery comprises a dual graphite battery, the battery comprising a graphite positive electrode and a graphite negative electrode.

10. An electrical device, characterized in that: The secondary battery according to any one of claims 8 to 9 is used as a power source for the electrical device.

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