Ultralow-temperature electrolyte and lithium carbon fluoride battery prepared from ultralow-temperature electrolyte

Abstract

The invention discloses an ultralow-temperature electrolyte and a lithium carbon fluoride battery prepared from the ultralow-temperature electrolyte, and belongs to the technical field of batteries, the ultralow-temperature electrolyte comprises an organic solvent and a lithium salt, the organic solvent is a mixture of a carboxylic ester compound and a fluorinated ester compound, the concentration of the lithium salt in the electrolyte is 0.5-2.0 mol / L, and the concentration of the fluorinated ester compound in the electrolyte is 0.5-2.0 mol / L; the volume fraction of the carboxylic ester compound in the electrolyte is 70%-90%, the volume fraction of the fluorinated ester compound in the electrolyte is 10%-30%, and the prepared electrolyte is kept in a liquid state at-40 DEG C. Appropriate carboxylic ester and carbonic ester solvents are selected and used in a matched mode according to a certain proportion, and the conductivity of the electrolyte can be improved at low temperature, the viscosity can be reduced, the low-temperature activity can be enhanced, and the low-temperature performance can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries, and in particular relates to an ultra-low temperature electrolyte and a lithium carbon fluoride battery prepared therefrom. Background Art

[0002] There are many types of lithium metal primary batteries, which usually have high energy density and operating voltage. In recent years, lithium carbon fluoride batteries have become the most promising system due to their extremely high theoretical energy density (2180Wh / kg) and stable operating voltage (2.5V~2.6V). They are widely used in polar scientific research, deep space exploration and other fields. The needs of these fields require not only high energy density of the power source, but also the ability to continuously output energy in low temperature environments.

[0003] However, due to the poor electronic conductivity of carbon fluoride materials themselves and the lack of suitable electrolytes, their application in low-temperature scenarios is severely limited. Usually under low temperature conditions, the viscosity of the electrolyte will increase, resulting in a decrease in the conductivity of lithium ions in the electrolyte, slowing down the desolvation of the interface, increasing the internal resistance, and reducing the diffusion coefficient, which will eventually cause serious energy loss. At -20°C, the capacity lost by most batteries is about half of their rated capacity at room temperature, and at -30°C to -40°C, the loss may reach two-thirds of the rated capacity at room temperature; at lower temperatures, the released capacity is almost zero, and the battery cannot work. In order to meet the growing needs of low-temperature scenarios, it is more feasible and practical to formulate a reasonable lithium carbon fluoride battery electrolyte with an ultra-low temperature working range than complex and costly material modifications. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides an ultra-low temperature electrolyte and a lithium carbon fluoride battery prepared therefrom, so as to overcome the defects of the prior art.

[0005] The present invention is implemented as follows: an ultra-low temperature electrolyte includes an organic solvent and a lithium salt, wherein the organic solvent is a mixture of a carboxylic acid ester compound and a fluoroester compound, the concentration of the lithium salt in the electrolyte is 0.5-2.0 mol / L, the volume fraction of the carboxylic acid ester compound in the electrolyte is 70%-90%, and the volume fraction of the fluoroester compound in the electrolyte is 10%-30%, and the electrolyte is prepared to remain in a liquid state at -40°C.

[0006] The carboxylic acid ester compound is at least one of methyl acetate, ethyl acetate, methyl formate, methyl propionate, ethyl propionate, methyl butyrate and ethyl butyrate.

[0007] The fluorinated ester compound is at least one of fluoroethylene carbonate, 2,2,2-trifluoroethylbutyrate, 2,2,2-trifluoroethyl acetate, ethyl trifluoroacetate and methyl pentafluoropropionate.

[0008] The lithium salt is at least one of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium bis(fluorosulfonyl)imide salt and lithium bis(trifluoromethanesulfonyl)imide.

[0009] A lithium carbon fluoride battery is prepared using the ultra-low temperature electrolyte.

[0010] The positive electrode active substance of the lithium carbon fluoride battery is at least one of graphite fluoride, graphene fluoride, carbon fluoride microspheres, carbon fluoride fibers and carbon fluoride nanotubes.

[0011] The conductive agent of the lithium fluoride carbon battery is at least one of conductive carbon black, carbon nanotubes, carbon nanofibers, Ketjen black, graphene and single-walled carbon nanotubes.

[0012] The binder of the lithium carbon fluoride battery is at least one of polyvinylidene fluoride, polytetrafluoroethylene and carboxymethyl cellulose.

[0013] The negative electrode sheet of the lithium fluoride carbon battery is a metal lithium sheet, and its thickness is controlled to be 0.20-0.50 mm.

[0014] The diaphragm of the lithium carbon fluoride battery is a polymer diaphragm, a composite polymer diaphragm or an inorganic material diaphragm.

[0015] The beneficial effects of the present invention are: selecting suitable carboxylic acid ester and carbonate solvents and using them in a certain proportion can improve the conductivity of the electrolyte, reduce the viscosity, enhance the low-temperature activity, and improve the low-temperature performance at low temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The figures are discharge curve comparison diagrams of button batteries using the electrolytes of Example 1 of the present invention and Comparative Example 1 respectively (discharge rate 0.1C, the left is the discharge specific capacity curve, and the right is the discharge specific energy curve).

[0017] Figure 2 The figures are discharge curve comparison diagrams of button batteries using the electrolytes of Example 2 of the present invention and Comparative Example 2 respectively (discharge rate 0.1C, the left is the discharge specific capacity curve, and the right is the discharge specific energy curve).

[0018] Figure 3 The figures are discharge curve comparison diagrams of button batteries using the electrolytes of Example 3 of the present invention and Comparative Example 3 respectively (discharge rate 0.1C, the left is the discharge specific capacity curve, and the right is the discharge specific energy curve). DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further illustrated and described below by specific implementation modes in combination with the accompanying drawings. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0020] The electrolyte of the present invention comprises an organic solvent and a lithium salt, wherein the organic solvent is a mixture of a carboxylic acid ester compound and a carbonate compound, the concentration of the lithium salt in the electrolyte is 0.5 to 2.0 mol / L, the volume fraction of the carboxylic acid ester compound in the electrolyte is 70% to 90%, and the volume fraction of the fluoroester compound in the electrolyte is 10% to 30%. In the electrolyte provided by the present invention, the concentration of the electrolyte salt in the electrolyte is any value in the range of 0.5 to 2.0 mol / L, and can be 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, and 2.0 mol / L, the volume fraction of the carboxylic acid ester compound in the electrolyte is any value in the range of 70% to 90%, and can be 70%, 80%, and 90% by example, and the volume fraction of the fluoroester compound in the electrolyte is any value in the range of 10% to 30%, and can be 10%, 20%, and 30% by example.

[0021] The abbreviations of the compounds involved in the present invention are as follows: ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl acetate (MA), ethyl acetate (EA), methyl formate (MF), methyl propionate (MP), ethyl propionate (EP), methyl butyrate (MB), ethyl butyrate (EB), fluoroethylene carbonate (FEC), 2,2,2-trifluoroethylbutyrate (TFEB), 2,2,2-trifluoroethyl acetate (TFEA), ethyl trifluoroacetate (ETFA) and methyl pentafluoropropionate (MPFP), lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(oxalatoborate) (LiBOB), lithium difluorooxalatoborate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethylsulfonimide) (LiTFSI), polyvinylidene fluoride (PVDF), and N-methylpyrrolidone (NMP).

[0022] In a room temperature glove box filled with argon, the electrolytes of the following Examples 1 to 3 and Comparative Examples 1 to 3 were prepared.

[0023] Embodiment 1:

[0024] In a room temperature glove box filled with argon, 10 mL of an electrolyte containing MP and FEC (volume ratio of 9:1) was prepared, and 1.8707 g of LiFSI was added thereto and mixed thoroughly to prepare an electrolyte with a concentration of 1 mol / L.

[0025] Embodiment 2:

[0026] In a room temperature glove box filled with argon, 10 mL of an electrolyte containing EA and TFEA (volume ratio of 8:2) was prepared, and 3.7414 g of LiFSI was added thereto and mixed thoroughly to prepare an electrolyte with a concentration of 2 mol / L.

[0027] Embodiment 3:

[0028] In a room temperature glove box filled with argon, 10 mL of an electrolyte containing EB and MPFP (volume ratio of 9:1) was prepared, and 0.5320 g of LiClO4 was added thereto and mixed thoroughly to prepare an electrolyte with a concentration of 0.5 mol / L.

[0029] Comparative Example 1:

[0030] In a room temperature glove box filled with argon, 10 mL of an electrolyte containing EC and EMC (volume ratio of 1:1) was prepared, and 1.8707 g of LiFSI was added thereto and mixed thoroughly to prepare an electrolyte with a concentration of 1 mol / L.

[0031] Comparative Example 2:

[0032] In a room temperature glove box filled with argon, 10 mL of an electrolyte containing EC and DMC (volume ratio of 1:1) was prepared, and 3.7414 g of LiFSI was added thereto and mixed thoroughly to prepare an electrolyte with a concentration of 2 mol / L.

[0033] Comparative Example 3:

[0034] In a room temperature glove box filled with argon, 10 mL of an electrolyte containing EC, DMC and EMC (volume ratio of 1:1:1) was prepared, and 0.5320 g of LiClO4 was added thereto and mixed thoroughly to prepare an electrolyte with a concentration of 0.5 mol / L.

[0035] Make the carbon fluoride electrode:

[0036] At room temperature, graphite fluoride, conductive agent ECP conductive carbon black, and binder PVDF 5130 (6% wt.) are slurried in a mass ratio of 8:1:1, and NMP is used as a solvent. The mixture is mixed evenly to form a slurry, which is evenly coated on an aluminum foil, cut into small discs of required specifications, and dried in a vacuum oven at 110°C to obtain a fluorinated carbon electrode.

[0037] Test cell preparation:

[0038] The prepared carbon fluoride electrode was used as the positive electrode, the metal lithium sheet was used as the negative electrode, and Celgard 2340 was used as the separator. The electrolytes in Examples 1 to 3 and Comparative Examples 1 to 3 were respectively assembled into CR2430 button batteries. The constant rate discharge performance test was performed on the LAND battery test system. The cut-off voltage was 1.5V, the discharge rate was set to 0.1C, and the test environment was a constant temperature of -40°C. The test curves were as follows: Figures 1 to 3 The test results are shown in Table 1.

[0039] Table 1

[0040]

[0041] pass Figures 1 to 3 From the results in Table 1, it can be found that the electrolyte provided by the embodiment of the present invention can greatly improve the discharge performance of the lithium fluoride carbon battery at low temperature through the synergistic use of carboxylic acid ester and carbonate solvents.

[0042] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Therefore, the scope of implementation of the present invention cannot be limited thereto. That is, equivalent changes and modifications made according to the patent scope of the present invention and the contents of the specification should still fall within the protection scope covered by the present invention.

Claims

1. An ultra-low temperature electrolyte comprising an organic solvent and a lithium salt, characterized in that: The organic solvent is a mixture of carboxylic acid ester compounds and fluoroester compounds, the concentration of lithium salt in the electrolyte is 0.5-2.0 mol / L, the volume fraction of the carboxylic acid ester compound in the electrolyte is 70%-90%, and the volume fraction of the fluoroester compound in the electrolyte is 10%-30%, and the electrolyte is prepared to remain in liquid at -40°C.

2. The ultra-low temperature electrolyte according to claim 1, characterized in that: The carboxylic acid ester compound is at least one of methyl acetate, ethyl acetate, methyl formate, methyl propionate, ethyl propionate, methyl butyrate and ethyl butyrate.

3. The ultra-low temperature electrolyte according to claim 1, characterized in that: The fluorinated ester compound is at least one of fluoroethylene carbonate, 2,2,2-trifluoroethylbutyrate, 2,2,2-trifluoroethyl acetate, ethyl trifluoroacetate and methyl pentafluoropropionate.

4. The ultra-low temperature electrolyte according to claim 1, characterized in that: The lithium salt is at least one of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium bis(fluorosulfonyl)imide salt and lithium bis(trifluoromethanesulfonyl)imide.

5. A lithium carbon fluoride battery, characterized in that: Prepared using the ultra-low temperature electrolyte described in any one of claims 1 to 4.

6. The lithium carbon fluoride battery according to claim 5, characterized in that: The positive electrode active substance of the lithium carbon fluoride battery is at least one of graphite fluoride, graphene fluoride, carbon fluoride microspheres, carbon fluoride fibers and carbon fluoride nanotubes.

7. The lithium carbon fluoride battery according to claim 5, characterized in that: The conductive agent of the lithium fluoride carbon battery is at least one of conductive carbon black, carbon nanotubes, carbon nanofibers, Ketjen black, graphene and single-walled carbon nanotubes.

8. The lithium carbon fluoride battery according to claim 5, characterized in that: The binder of the lithium carbon fluoride battery is at least one of polyvinylidene fluoride, polytetrafluoroethylene and carboxymethyl cellulose.

9. The lithium carbon fluoride battery according to claim 5, characterized in that: The negative electrode sheet of the lithium fluoride carbon battery is a metal lithium sheet, and its thickness is controlled to be 0.20-0.50 mm.

10. The lithium carbon fluoride battery according to claim 5, characterized in that: The diaphragm of the lithium carbon fluoride battery is a polymer diaphragm, a composite polymer diaphragm or an inorganic material diaphragm.

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