Lithium ion battery electrolyte, preparation method and application thereof

Abstract

The present application relates to a kind of lithium ion battery electrolyte and its preparation method and application, belong to lithium ion battery electrolyte technical field.The electrolyte of the present application is specifically a kind of 1-alkyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonic acid ionic liquid and lithium trifluoromethanesulfonate and water preparation mixed electrolyte.The functionalized 1-alkyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonic acid ionic liquid prepared by the present application effectively expands the solubility of lithium trifluoromethanesulfonate in water, the mass fraction of lithium trifluoromethanesulfonate salt contained in the electrolyte of the present application far exceeds the mass fraction of solvent water, reaches the effect of " salt package water", inhibits the movement of water molecules in solution, makes water molecules far away from electrode, reduces the occurrence of side reaction, effectively widens the electrochemical window of lithium ion battery electrolyte, improves electrochemical performance, and preparation method is simple, easy to realize scale production.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery electrolyte technology, specifically relating to a lithium-ion battery electrolyte, its preparation method, and its application. Background Technology

[0002] The global fossil fuel crisis is looming, prompting efforts to efficiently utilize renewable energy sources such as solar, wind, and tidal power. Rechargeable lithium-ion batteries, as promising sustainable energy storage systems, have attracted global research interest. Simultaneously, the ever-increasing demand for longer battery life continues to drive improvements in the energy density of these lithium-ion batteries. Improving the electrochemical window of the electrolyte is one effective method to increase battery energy density. The electrolyte is also a crucial factor influencing lithium-ion battery performance. In recent years, mixed salt electrolytes have made significant progress in the emerging next-generation lithium-ion battery field. Single mixed salt electrolytes cannot meet all requirements; adding functional additives can further enhance the performance of mixed salt electrolyte lithium-ion batteries. Therefore, selecting and innovating suitable additives with a wide electrochemical stability window is essential for mixed salt electrolytes.

[0003] Most studies have used lithium salts dissolved in organic solvents to form non-aqueous electrolytes containing highly flammable and volatile organic solvents, leading to safety concerns. Therefore, it is necessary to explore a safe alternative electrolyte. Because ionic liquids exhibit unique properties, such as flame retardancy, non-volatility, and high thermal stability, dissolving lithium salts in ionic liquids offers a novel approach. Furthermore, this electrolyte exhibits a fairly wide electrochemical window, providing an important direction for the development of lithium-ion batteries and offering significant research prospects for the practical application of mixed salt electrolytes. Summary of the Invention

[0004] Lithium salts must be dissolved at high concentrations to ensure sufficient lithium-ion conductivity, but this leads to increased electrolyte viscosity and decreased ionic conductivity. Therefore, the problem of high-concentration lithium salts is addressed by introducing aqueous electrolytes. These electrolytes are non-flammable and exhibit high ionic conductivity, but they have a low electrochemical stability window. Therefore, this invention prepares a "salt-in-water" electrolyte, which is prepared by mixing a functionalized 1-alkyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonic acid ionic liquid with lithium trifluoromethanesulfonate and water. This invention effectively improves the electrochemical window and thermal stability of the "salt-in-water" electrolyte, enhances its performance over a wide temperature range (high and low temperatures), forms a good interface layer on the two electrodes, and protects the lithium metal anode.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A lithium-ion battery electrolyte is a mixed electrolyte prepared from a functionalized 1-alkyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonic acid ionic liquid, lithium trifluoromethanesulfonate, and water. The general structural formula of the functionalized 1-alkyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonic acid ionic liquid is shown in (I):

[0007]

[0008] Furthermore, in the aforementioned lithium-ion battery electrolyte, the alkyl group is one of methyl, ethyl, propyl, butyl, pentyl, or hexyl.

[0009] The above-mentioned method for preparing a lithium-ion battery electrolyte includes the following steps:

[0010] 1) Place N-alkylpiperidine in a reactor and heat and stir at 40℃~160℃. Then add 2-chloro-N,N-dimethylacetamide to the reactor and react for 6~36h. After the product cools to room temperature, pour the product in the reactor into a container and seal it to isolate it from air. Place it in a freezer for 5~30h to obtain a crude crystalline product. Dissolve the crude crystalline product in another reactor and heat and stir at 40℃~160℃. Add a mixed solvent of ethyl acetate and acetonitrile to wash the product. Repeat the washing operation 2~4 times. Dry the product to obtain the high-purity intermediate 1-alkyl-1-N,N-dimethylacetamide piperidine.

[0011] 2) The intermediate 1-alkyl-1-N,N-dimethylacetamide piperidine was placed in a reactor, and deionized water and silver trifluoromethanesulfonate were added to the reactor. The mixture was stirred continuously for 6–36 h. The crude product obtained after the reaction was separated and filtered. Water was added to the crude product again, and the mixture was stirred, washed, separated, and filtered. The washing and filtration operations were repeated until silver nitrate was added to the aqueous washing liquid and no longer produced turbidity. The filtered product was then subjected to thorough rotary evaporation and vacuum filtration. The filtered product was dried to obtain 1-alkyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonate ionic liquid.

[0012] 3) Preparation of electrolyte: A mixed lithium-ion battery electrolyte was prepared using lithium trifluoromethanesulfonate as the solute and 1-alkyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonate ionic liquid and water as solvents.

[0013] Furthermore, in the above preparation method, in step 1), the molar ratio of N-alkylpiperidine to 2-chloro-N,N-dimethylacetamide is 1:1 to 10.

[0014] Furthermore, in the above preparation method, in step 1), the molar ratio of acetonitrile to ethyl acetate is 1:1 to 10.

[0015] Furthermore, in the above preparation method, in step 2), the molar ratio is 1-alkyl-1-N,N-dimethylacetamide piperidine:deionized water:silver trifluoromethanesulfonate = 1:1~10:1~10.

[0016] Furthermore, in step 3) of the above preparation method, the molality of the 1-alkyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonic acid ionic liquid is 10–50 mol / kg, and the molality of lithium trifluoromethanesulfonate is 20–100 mol / kg.

[0017] Furthermore, in the above preparation method, in steps 1) and 2), the drying conditions are: drying in a vacuum drying oven at 40℃ to 160℃ for 6 to 36 hours.

[0018] The above-mentioned lithium-ion battery electrolyte is used in lithium-ion full batteries.

[0019] Furthermore, in the above application, the positive electrode of the lithium-ion full battery uses Li4Ti5O. 12 Active electrode material, LiNi is used for the negative electrode. 0.8 Mn 0.1 Co 0.1 O2 active electrode material.

[0020] The beneficial effects of this invention are as follows:

[0021] 1. This invention solves the problem of increased electrolyte viscosity and decreased ionic conductivity caused by the requirement that lithium salts must be dissolved at high concentrations to ensure sufficient lithium ion conductivity.

[0022] 2. The electrolyte of this invention is non-flammable, exhibits high ionic conductivity, effectively improves the energy density and thermal stability of lithium batteries, enhances wide-temperature-range (high and low temperature) performance, forms a good interface layer on the two electrodes, protects the lithium metal anode, and achieves high ionic conductivity. Attached Figure Description

[0023] Figure 1 Linear scan voltammetry diagrams of lithium-ion full cells assembled using the four lithium-ion battery electrolytes prepared in Examples 1-4. Detailed Implementation

[0024] To further understand the present invention, the preferred experimental scheme of the present invention is described below in conjunction with embodiments. It should be noted that the following embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Therefore, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

[0025] Example 1

[0026] 1) N-methylpiperidine was placed in a reactor and heated and stirred at 50°C. Then, 2-chloro-N,N-dimethylacetamide (1:5) was added to the reactor and reacted for 7 hours. The product was then removed. After the product cooled to room temperature, it was poured into a container and sealed to isolate it from air. The container was then placed in a freezer for 10 hours to obtain a crude crystalline product. The crude crystalline product was dissolved in another reactor and heated and stirred at 40°C. A mixed solvent of acetonitrile and ethyl acetate (1:3) was added to wash the product. The washing operation was repeated 2 to 4 times. The product was then dried in a vacuum drying oven at 80°C for 8 hours to obtain the high-purity intermediate 1-methyl-1-N,N-dimethylacetamide piperidine.

[0027] 2) The intermediate 1-methyl-1-N,N-dimethylacetamide piperidine was placed in a reactor, and deionized water and silver trifluoromethanesulfonate in a 1:2:2 ratio were added to the reactor. The mixture was stirred continuously for 8 hours. The crude product obtained after the reaction was separated and filtered. Deionized water was added to the crude product again, and the mixture was stirred, washed, separated, and filtered. The washing and filtration operations were repeated until silver nitrate was added to the aqueous washing liquid and no longer produced turbidity. The filtered product was then subjected to complete rotary evaporation and vacuum filtration. The filtered product was placed in a vacuum drying oven at 80°C and dried for 9 hours to obtain 1-methyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonate ionic liquid.

[0028] The structure of the ionic liquid 1-methyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonic acid is shown in (II):

[0029]

[0030] 3) Preparation of electrolyte: The molality of 1-methyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonic acid ionic liquid is 15 mol / kg, the molality of lithium trifluoromethanesulfonate is 20 mol / kg, and a mixed lithium-ion battery electrolyte is prepared with water.

[0031] Example 2

[0032] 1) N-ethylpiperidine was placed in a reactor and heated and stirred at 70°C. Then, 2-chloro-N,N-dimethylacetamide in a 1:6 ratio was added to the reactor. After reacting for 9 hours, the product was removed. After the product cooled to room temperature, the product in the reactor was poured into a container and sealed to isolate it from air. The container was then placed in a freezer for 13 hours to obtain a crude crystalline product. The crude crystalline product was dissolved in another reactor and heated and stirred at 50°C. A mixed solvent of acetonitrile and ethyl acetate in a 1:4 ratio was added to wash the product. The washing operation was repeated 2 to 4 times. The product was then dried in a vacuum drying oven at 110°C for 12 hours to obtain a high-purity intermediate, 1-ethyl-1-N,N-dimethylacetamide piperidine.

[0033] 2) The intermediate 1-ethyl-1-N,N-dimethylacetamide piperidine was placed in a reactor, and deionized water and silver trifluoromethanesulfonate in a 1:3:3 ratio were added to the reactor. The mixture was stirred continuously for 12 hours. The crude product obtained after the reaction was separated and filtered. Deionized water was added to the crude product again, and the mixture was stirred, washed, separated, and filtered. The washing and filtration operations were repeated until silver nitrate was added to the aqueous washing liquid and no longer produced turbidity. The filtered product was then subjected to complete rotary evaporation and vacuum filtration. The filtered product was placed in a vacuum drying oven at 110°C and dried for 15 hours to obtain 1-ethyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonate ionic liquid.

[0034] The structure of the ionic liquid 1-ethyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonic acid is shown in (III):

[0035]

[0036] 3) Preparation of electrolyte: The molality of 1-ethyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonic acid ionic liquid is 20 mol / kg, the molality of lithium trifluoromethanesulfonate is 50 mol / kg, and a mixed lithium-ion battery electrolyte is prepared with water.

[0037] Example 3

[0038] 1) N-propylpiperidine was placed in a reactor and heated and stirred at 90°C. Then, 2-chloro-N,N-dimethylacetamide (1:7) was added to the reactor and reacted for 12 hours. The product was then removed. After the product cooled to room temperature, it was poured into a container and sealed to isolate it from air. The container was then placed in a freezer for 15 hours to obtain a crude crystalline product. The crude crystalline product was dissolved in another reactor and heated and stirred at 70°C. A mixed solvent of acetonitrile and ethyl acetate (1:6) was added to wash the product. The washing operation was repeated 2 to 4 times. The product was then dried in a vacuum drying oven at 140°C for 16 hours to obtain the high-purity intermediate 1-propyl-1-N,N-dimethylacetamide piperidine.

[0039] 2) The intermediate 1-propyl-1-N,N-dimethylacetamide piperidine was placed in a reactor, and deionized water and silver trifluoromethanesulfonate in a 1:4:4 ratio were added to the reactor. The mixture was stirred continuously for 16 hours. The crude product obtained after the reaction was separated and filtered. Deionized water was added to the crude product again, and the mixture was stirred, washed, separated, and filtered. The washing and filtration operations were repeated until silver nitrate was added to the aqueous washing liquid and no longer produced turbidity. The filtered product was then subjected to complete rotary evaporation and vacuum filtration. The filtered product was placed in a vacuum drying oven at 140°C and dried for 20 hours to obtain 1-propyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonate ionic liquid.

[0040] The structure of the ionic liquid 1-propyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonic acid is shown in (IV):

[0041]

[0042] 3) Preparation of electrolyte: The molality of 1-propyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonic acid ionic liquid is 30 mol / kg, the molality of lithium trifluoromethanesulfonate is 80 mol / kg, and a mixed lithium-ion battery electrolyte is prepared with water.

[0043] Example 4

[0044] 1) N-Butylpiperidine was placed in a reactor and heated and stirred at 110°C. Then, 2-chloro-N,N-dimethylacetamide (1:8 ratio) was added to the reactor and reacted for 15 hours. The product was then removed. After the product cooled to room temperature, it was poured into a container and sealed to isolate it from air. The container was then placed in a freezer for 19 hours to obtain a crude crystalline product. The crude crystalline product was dissolved in another reactor and heated and stirred at 100°C. A mixed solvent of acetonitrile and ethyl acetate (1:9 ratio) was added to wash the product. The washing operation was repeated 2 to 4 times. The product was then dried in a vacuum drying oven at 160°C for 24 hours to obtain a high-purity intermediate, 1-butyl-1-N,N-dimethylacetamide piperidine.

[0045] 2) The intermediate 1-butyl-1-N,N-dimethylacetamide piperidine was placed in a reactor, and deionized water and silver trifluoromethanesulfonate in a 1:5:5 ratio were added to the reactor. The mixture was stirred continuously for 24 hours. The crude product obtained after the reaction was separated and filtered. Deionized water was added to the crude product again, and the mixture was stirred, washed, separated, and filtered. The washing and filtration operations were repeated until silver nitrate was added to the aqueous washing liquid and no longer produced turbidity. The filtered product was then subjected to complete rotary evaporation and vacuum filtration. The filtered product was placed in a vacuum drying oven at 150°C and dried for 25 hours to obtain 1-butyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonate ionic liquid.

[0046] The structure of the 1-butyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonic acid ionic liquid is shown in (V):

[0047]

[0048] 3) Preparation of electrolyte: The molality of 1-butyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonic acid ionic liquid is 45 mol / kg, the molality of lithium trifluoromethanesulfonate is 100 mol / kg, and a mixed lithium-ion battery electrolyte is prepared with water.

[0049] Example 5

[0050] In this embodiment, all four lithium-ion battery electrolytes prepared in Examples 1-4 are derived from Li4Ti5O4. 12 Active electrode material as positive electrode, using LiNi 0.8 Mn 0.1 Co 0.1 O2 active electrode material is used as the negative electrode, and glass fiber is used as the separator, along with gaskets and springs, to form a lithium-ion full battery. The linear sweep voltammetry test voltage range is -2.5V to 0V and 0V to 2.5V. Test results are as follows... Figure 1 As shown, all four electrolytes have a wide electrochemical window and stable electrochemical performance.

Claims

1. A lithium-ion battery electrolyte, characterized in that, The lithium-ion battery electrolyte is a mixed electrolyte prepared from a functionalized 1-alkyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonic acid ionic liquid, lithium trifluoromethanesulfonate, and water. The general structural formula of the functionalized 1-alkyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonic acid ionic liquid is shown in (I): (I); The alkyl group is one of methyl, ethyl, propyl, butyl, pentyl or hexyl.

2. The method for preparing a lithium-ion battery electrolyte according to claim 1, characterized in that, Includes the following steps: 1) Place N-alkylpiperidine in a reactor and heat and stir at 40℃~160℃. Then add 2-chloro-N,N-dimethylacetamide to the reactor and react for 6~36h. After the product cools to room temperature, pour the product in the reactor into a container and seal it to isolate it from air. Place it in a freezer for 5~30h to obtain a crude crystalline product. Dissolve the crude crystalline product in another reactor and heat and stir at 40℃~160℃. Add a mixed solvent of ethyl acetate and acetonitrile to wash the product. Repeat the washing operation 2~4 times. Dry the product to obtain the high-purity intermediate 1-alkyl-1-N,N-dimethylacetamide piperidine. 2) The intermediate 1-alkyl-1-N,N-dimethylacetamide piperidine was placed in a reactor, and deionized water and silver trifluoromethanesulfonate were added to the reactor. The mixture was stirred continuously for 6–36 h. The crude product obtained after the reaction was separated and filtered. Water was added to the crude product again, and the mixture was stirred, washed, separated, and filtered. The washing and filtration operations were repeated until silver nitrate was added to the aqueous washing liquid and no longer produced turbidity. The filtered product was then subjected to thorough rotary evaporation and vacuum filtration. The filtered product was dried to obtain 1-alkyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonate ionic liquid. 3) Preparation of electrolyte: A mixed lithium-ion battery electrolyte was prepared using lithium trifluoromethanesulfonate as the solute and 1-alkyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonate ionic liquid and water as solvents.

3. The preparation method according to claim 2, characterized in that, In step 1), the molar ratio is N-alkylpiperidine: 2-chloro-N,N-dimethylacetamide = 1:1 to 10.

4. The preparation method according to claim 2, characterized in that, In step 1), the molar ratio of acetonitrile to ethyl acetate is 1:1 to 10.

5. The preparation method according to claim 2, characterized in that, In step 2), the molar ratio is 1-alkyl-1-N,N-dimethylacetamide piperidine:deionized water:silver trifluoromethanesulfonate = 1:1~10:1~10.

6. The preparation method according to claim 2, characterized in that, In step 3), the molality of the 1-alkyl-N,N-dimethylacetamide piperidine trifluoromethanesulfonic acid ionic liquid is 10–50 mol / kg, and the molality of lithium trifluoromethanesulfonate is 20–100 mol / kg.

7. The preparation method according to claim 2, characterized in that, In steps 1) and 2), the drying conditions are: drying in a vacuum drying oven at 40℃ to 160℃ for 6 to 36 hours.

8. The application of the lithium-ion battery electrolyte as described in claim 1 in lithium-ion full batteries.

9. The application according to claim 8, characterized in that, The positive electrode of the lithium-ion full battery uses LiNi. 0.8 Mn 0.1 Co 0.1 O2 active electrode material, with Li4Ti5O used as the negative electrode. 12 Active electrode materials.

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