Lithium carbon fluoride battery electrolyte, preparation method thereof and lithium carbon fluoride battery

Abstract

The invention discloses a lithium carbon fluoride battery electrolyte, a preparation method thereof and a lithium carbon fluoride battery, and belongs to the technical field of lithium / carbon fluoride primary batteries. The lithium carbon fluoride battery electrolyte comprises a lithium salt and a monofluoro-substituted short-chain ether solvent. Compared with a non-fluorinated ether solvent, the monofluoroether solvent has good compatibility with a carbon fluoride positive electrode and a metal lithium negative electrode, so that the battery has good discharge performance. Compared with a polyfluoro-substituted ether solvent, the monofluoro substituent group (-CH2F) obviously improves the ionic conductivity of the lithium carbon fluoride battery electrolyte at low temperature, and meanwhile, the monofluoro substituent group (-CH2F) has weak solvation energy at low temperature, so that the discharge platform of the battery at low temperature is obviously improved, and the discharge capacity of the battery is improved.

Description

A lithium fluorinated carbon battery electrolyte and its preparation method, and a lithium fluorinated carbon battery. Technical Field

[0001] This application relates to a lithium fluoride carbon battery electrolyte and its preparation method, and a lithium fluoride carbon battery, belonging to the field of lithium / fluoride carbon primary battery technology. Background Technology

[0002] With technological advancements in mobile communications, aerospace, transportation, and military equipment, the development of various high-energy-density power batteries has become an urgent need for national economic development. Due to the light weight and negative electrode potential of lithium metal, the development of lithium primary batteries with lithium as the negative electrode has received considerable attention.

[0003] Lithium primary batteries mainly include lithium-manganese dioxide (Li / MnO2), lithium-sulfur dioxide (Li / SO2), lithium-thionyl chloride (Li / SOCl2), and lithium-carbon fluoride (Li / CF2). x Battery systems such as Li / CF2. Compared with other galvanic cells, Li / CF2... x The battery has the highest theoretical specific energy (2180 Wh / kg), while Li / CF x The battery also has advantages such as high safety, stable discharge voltage, and environmental friendliness. It has great application prospects, especially in space applications such as satellites, spacecraft, space stations, deep space exploration (Mars, asteroid) landers, upper stages, and orbital transfer vehicles, as well as individual soldier systems and drones.

[0004] However, due to the poor electrical conductivity of fluorinated carbon materials, their low-temperature performance is inferior to that of CF4. x Material modification and optimization, and the development of novel electrolytes are key to improving Li / CF2 performance. x A more economical and effective means to improve the low-temperature performance of batteries. Using solvents with low solvation energy is key to improving the low-temperature performance of batteries. However, existing technologies still have the following drawbacks: existing low solvation energy solvents have poor compatibility with lithium metal anodes, and low solvation energy solvents cannot dissociate lithium salts, resulting in very low ionic conductivity of the electrolyte at room temperature and low temperature. Summary of the Invention

[0005] The purpose of this application is to provide a lithium fluorinated carbon battery electrolyte, its preparation method, and a lithium fluorinated carbon battery. A monofluoroether solvent is used as the low-temperature electrolyte for the fluorinated carbon battery. This solvent has good compatibility with both the fluorinated carbon cathode and the lithium metal anode, resulting in good battery discharge performance. The monofluoro substituent (-CH2F) significantly improves the ionic conductivity of the electrolyte at low temperatures, and also possesses weak solvation energy at low temperatures, which can significantly enhance the discharge plateau of the battery at low temperatures, thereby increasing the battery discharge capacity. In contrast, polyfluorosubstituted ether solvents cannot solvate lithium ions, leading to lower ionic conductivity of the electrolyte at both room temperature and low temperatures, thus affecting battery performance.

[0006] According to one aspect of this application, a lithium fluorinated carbon battery electrolyte is provided, the lithium fluorinated carbon battery electrolyte comprising a lithium salt and a monofluorinated substituted short-chain ether solvent;

[0007] The lithium salt is selected from at least one of LiPF6, LiBF4, LiClO4, LiAsF6, LiBOB, LiODFB, LiFSI, and LiTFSI.

[0008] The monofluorinated short-chain ether solvent is selected from at least one of the structures shown in Formulas I to V;

[0009]

[0010] Optionally, the concentration of the lithium salt is 0.5 to 3 mol / L.

[0011] Optionally, the concentration of the lithium salt is independently selected from any value among 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, and 3 mol / L, or a range between any two of the above values.

[0012] Optionally, the concentration of the lithium salt is 0.5–1.5 mol / L.

[0013] According to another aspect of this application, a method for preparing a lithium fluoride carbon battery electrolyte is provided, comprising the following steps: mixing a dried lithium salt with a monofluorinated short-chain ether solvent to obtain the lithium fluoride carbon battery electrolyte.

[0014] As a specific implementation method, the preparation method of the lithium fluoride carbon battery electrolyte includes the following steps: preparing the electrolyte in a glove box, adding fully dried electrolyte lithium salt and organic solvent, and mixing evenly to obtain a clear lithium / fluoride carbon battery electrolyte.

[0015] According to another aspect of this application, a lithium fluorinated carbon battery is provided, the lithium fluorinated carbon battery comprising a fluorinated carbon positive electrode, a lithium negative electrode, a separator and an electrolyte;

[0016] The electrolyte is selected from the lithium fluorinated carbon battery electrolyte described above or the lithium fluorinated carbon battery electrolyte prepared by the above preparation method.

[0017] Optionally, the preparation of the fluorinated carbon cathode includes the following steps: coating a mixed solution of fluorinated carbon, conductive carbon black and binder into an electrode film using a wet film preparation device, and drying it under vacuum to obtain the fluorinated carbon cathode.

[0018] Optionally, the adhesive is PVDF.

[0019] Optionally, the mass ratio of the fluorinated carbon, conductive carbon black, and binder is 8:1:1.

[0020] Optionally, the solvent in the mixed solution is N-methylpyrrolidone.

[0021] Optionally, the solid-liquid ratio of fluorinated carbon, conductive carbon black, binder and solvent in the mixed solution is 50% to 80%.

[0022] Optionally, the thickness of the electrode film is 100–200 μm.

[0023] Optionally, the vacuum drying temperature is 60–120°C.

[0024] Optionally, the vacuum drying time is 12 to 24 hours.

[0025] Optionally, the diaphragm is selected from at least one of Celgard 2500 and Celgard 2325.

[0026] Optionally, the amount of electrolyte used is 35 to 100 μL.

[0027] Optionally, the operating temperature of the lithium fluoride carbon battery is -60 to 30°C.

[0028] Optionally, the allowable discharge rate of the lithium fluoride carbon battery during operation is 0.01 to 10C.

[0029] The beneficial effects that this application can produce include:

[0030] This application utilizes a monofluorinated short-chain ether solvent as the pure solvent to prepare an electrolyte with lithium salts. This results in an electrolyte with high ionic conductivity and good compatibility with both fluorinated carbon cathodes and metallic lithium anodes, leading to excellent battery discharge performance. Furthermore, its weak solvation energy at low temperatures significantly enhances the battery's discharge plateau and discharge capacity. Detailed Implementation

[0031] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0032] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0033] The analysis method in the embodiments of this application is as follows:

[0034] The ionic conductivity of the electrolyte was tested using a METTLER TOLEDO SG3 conductivity meter.

[0035] Electrochemical testing methods and conditions for lithium fluoride carbon batteries: The batteries were discharged to 1V at a rate of 0.1C at 25℃ and -60℃.

[0036] Example 1

[0037] The lithium salt electrolyte is LiFSI, and the concentration of the lithium salt in the lithium fluorinated carbon battery electrolyte is 1 mol / L. The structural formula of the monofluorinated short-chain ether solvent is as follows:

[0038]

[0039] Prepare the electrolyte as follows: In a glove box, add a thoroughly dried lithium electrolyte salt and an organic solvent, mix thoroughly to obtain a clear lithium / carbon fluoride battery electrolyte. Then test the ionic conductivity of the electrolyte.

[0040] Fluorinated carbon electrodes were prepared as follows: Fluorinated carbon, conductive carbon black, and a binder (PVDF) in a mass ratio of 8:1:1 were dissolved in N-methylpyrrolidone and mixed thoroughly, ensuring a solid-liquid ratio of 60% for the mixture. A 0.15 mm thick electrode film was coated using a wet film preparation device, vacuum dried, and then sliced ​​into 14 mm diameter electrode sheets. The weight of the active material was measured. Simultaneously, a lithium sheet was used as the negative electrode, Celgard 2325 as the separator, and 100 μL of electrolyte was added. The cells were assembled into button cells in an argon-filled glove box, and then electrochemical tests were conducted on the assembled lithium-fluorinated carbon batteries. Battery temperature changes were monitored.

[0041] Example 2

[0042] The preparation process in Example 2 is the same as in Example 1, except that the structural formula of the monofluorinated short-chain ether solvent is as follows:

[0043]

[0044] Example 3

[0045] The preparation process in Example 3 is the same as in Example 1, except that the structural formula of the monofluorinated short-chain ether solvent is as follows:

[0046]

[0047] Example 4

[0048] The preparation process in Example 4 is the same as in Example 1, except that the structural formula of the monofluorinated short-chain ether solvent is as follows:

[0049]

[0050] Example 5

[0051] The preparation process in Example 5 is the same as in Example 1, except that the structural formula of the monofluorinated short-chain ether solvent is as follows:

[0052]

[0053] Example 6

[0054] The preparation process in Example 6 is the same as in Example 1, except that the electrolyte lithium salt is LiClO4.

[0055] Example 7

[0056] The preparation process in Example 7 is the same as in Example 1, except that the electrolyte lithium salt is a mixture of LiFSI and LiBF4 in a 1:1 molar ratio.

[0057] Comparative Example 1

[0058] The preparation process in Comparative Example 1 is the same as in Example 1, except that the solvent has the following structural formula:

[0059]

[0060] Comparative Example 2

[0061] The preparation process in Comparative Example 2 is the same as in Example 1, except that the solvent has the following structural formula:

[0062]

[0063] Comparative Example 3

[0064] The preparation process in Comparative Example 3 is the same as in Example 1, except that the solvent has the following structural formula:

[0065]

[0066] Comparative Example 4

[0067] The preparation process in Comparative Example 4 is the same as in Example 1, except that the solvent has the following structural formula:

[0068]

[0069] Comparative Example 5

[0070] The preparation process in Comparative Example 5 is the same as in Example 1, except that the solvent has the following structural formula:

[0071]

[0072] Comparative Example 6

[0073] The preparation process in Comparative Example 6 is the same as in Example 1, except that the solvent has the following structural formula:

[0074]

[0075] Comparative Example 7

[0076] The preparation process in Comparative Example 7 is the same as in Example 1, except that the solvent has the following structural formula:

[0077]

[0078] Comparative Example 8

[0079] The preparation process in Comparative Example 8 is the same as in Example 1, except that the solvent is a mixture of propylene carbonate and a solvent having the structure shown below, with a volume ratio of 1:1.

[0080]

[0081] Test Example 1

[0082] The ionic conductivity of the electrolytes prepared in Examples 1-7 and Comparative Examples 1-8 was tested at 25°C and -60°C. The test results are shown in Table 1.

[0083] Table 1. Results of ionic conductivity tests on electrolytes prepared in Examples 1-7 and Comparative Examples 1-8.

[0084]

[0085] The capacity performance of the lithium fluoride carbon batteries assembled in Examples 1-7 and Comparative Examples 1-8 was tested at discharge temperatures of 25°C and -60°C. The test results are shown in Table 2.

[0086] Table 2. Performance test results of lithium-fluorinated carbon batteries assembled in Examples 1-7 and Comparative Examples 1-8

[0087]

[0088] As shown in Tables 1 and 2, this application uses a short-chain ether solvent with monofluorinated substitution as the pure solvent to prepare the electrolyte with lithium salt. This results in an electrolyte with high ionic conductivity at both 25°C and -60°C, while exhibiting weak solvation energy at low temperatures, significantly improving the battery's discharge performance at -60°C. Examples 1-5 demonstrate that the electrolyte prepared using LiFSI as the lithium salt exhibits better ionic conductivity at both room temperature and low temperature, and the battery shows optimal discharge performance at both. Examples 6-7 show that after replacing the lithium salt, the electrolyte still maintains good ionic conductivity at both room temperature and low temperature. Examples 1 and Comparative Examples 1-3 illustrate that short-chain ether solvents without F, those containing F and symmetrical structures, and those containing multiple F atoms result in poor low-temperature performance of the battery. The solvent without F has a lower affinity for Li... + It has a stronger solvation effect, leading to Li at low temperatures + Desolvation is difficult. Compared to symmetrical structures containing F, asymmetrical structures containing F are more conducive to solvent desolvation, improving the kinetic rate of the battery during low-temperature discharge. The presence of multiple F atoms leads to decreased electrolyte conductivity at both room temperature and low temperature, and also reduces battery performance. Comparative Example 4 shows that when F does not substitute the terminal positions of the short-chain ether, the battery performance deteriorates at both room temperature and low temperature. Comparative Examples 5 and 6 illustrate that as the number of carbon atoms (>5) and the amount of oxygen in the fluorinated ether solvent increase, the ionic conductivity of the electrolyte and the low-temperature performance of the battery significantly decrease. Comparative Example 7 shows that the electrolyte prepared using a conventional ethylene glycol dimethyl ether solvent has poor low-temperature performance. Examples 1 and 8 demonstrate that although the electrolyte prepared by adding a mixture of conventional propylene carbonate and fluorinated ether solvent has good room temperature performance, its low-temperature performance is significantly reduced. This is because propylene carbonate has a strong solvation effect, causing the Li... + It is difficult to desolvate, resulting in poor low-temperature performance.

[0089] Unless otherwise specified, all figures appearing in this application specification and claims, such as temperature and time values, should not be construed as absolutely precise values. Due to the standard deviation of measurement techniques, the measured values ​​inevitably contain a certain degree of experimental error.

[0090] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A lithium fluoride carbon battery electrolyte, characterized in that, The lithium fluoride carbon battery electrolyte comprises lithium salt and monofluorinated short-chain ether solvent; the monofluorinated short-chain ether solvent is selected from at least one of the structures shown in Formula I to Formula V; 2. The lithium fluoride carbon battery electrolyte according to claim 1, characterized in that, The lithium salt is selected from at least one of LiPF6, LiBF4, LiClO4, LiAsF6, LiBOB, LiODFB, LiFSI, and LiTFSI.

3. The lithium fluoride carbon battery electrolyte according to claim 1, characterized in that, The electrolyte of the lithium fluoride carbon battery is composed of lithium salt and monofluorinated short-chain ether solvent.

4. The lithium fluoride carbon battery electrolyte according to claim 1, characterized in that, The concentration of the lithium salt is 0.5–3 mol / L.

5. The lithium fluoride carbon battery electrolyte according to claim 1, characterized in that, The concentration of the lithium salt is 0.5–1.5 mol / L.

6. A method for preparing the lithium fluoride carbon battery electrolyte according to any one of claims 1 to 5, characterized in that, The process includes the following steps: mixing dried lithium salt with a monofluorinated short-chain ether solvent to prepare the lithium fluoride carbon battery electrolyte.

7. A lithium fluoride carbon battery, characterized in that, The lithium fluorinated carbon battery includes a fluorinated carbon positive electrode, a lithium negative electrode, a separator, and an electrolyte; the electrolyte is selected from the lithium fluorinated carbon battery electrolyte of any one of claims 1 to 5 or the lithium fluorinated carbon battery electrolyte prepared by the preparation method of claim 6.

8. The lithium fluoride carbon battery according to claim 7, characterized in that, The preparation of the fluorinated carbon cathode includes the following steps: The fluorinated carbon positive electrode is prepared by coating a mixed solution of fluorinated carbon, conductive carbon black and binder into an electrode film using a wet film preparation device and then drying it under vacuum.

9. The lithium fluoride carbon battery according to claim 7, characterized in that, The operating temperature of the lithium fluoride carbon battery is -60 to 30°C.

10. The lithium fluoride carbon battery according to claim 7, characterized in that, The allowable discharge rate of the lithium fluoride carbon battery during operation is 0.01 to 10C.

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