Lithium-ion battery electrolyte preparation method
The electrolyte in a lithium-ion battery is the carrier for ion transport in the battery. It is mainly composed of high-purity organic solvents, electrolyte lithium salts, and necessary additives. The electrolyte plays the role of conducting electrons between the positive and negative electrodes of a lithium-ion battery, which is the guarantee for the high voltage and high specific energy of lithium-ion batteries.
1. Vinyl carbonate was chlorinated with chlorine gas to synthesize chloroethylene carbonate, and then triethylamine was used as an acid-binding agent to remove hydrogen chloride, yielding vinylene carbonate. The chlorination reaction was carried out under solvent-free conditions, and the elimination reaction was carried out using dimethyl carbonate, which is commonly used as an electrolyte solvent, to prevent residual solvent from adversely affecting the additives.
2. Fluoroethylene carbonate is prepared by reacting anhydrous KF with chloroethylene carbonate. This method reduces safety and cost, and the production process is easy to control. With PEG.800 as a catalyst, the single-step yield is 82.5%.
3. 1,3-Propanesulfonyl lactone was chlorinated with chlorine to synthesize 2-chloro-1,3-propanesulfonyl lactone, and then 1,3-propanesulfonyl lactone was obtained by removing hydrogen chloride with triethylamine as an acid-binding agent. Compared with the literature, the reaction route was greatly shortened and the yield of the two-step reaction was 72.7%.
Lithium-ion battery electrolyte testing methods
1. Appearance
Observe the color of the lithium-ion battery electrolyte. Generally, electrolytes are colorless and transparent liquids. There are also specific national standards for the inspection of appearance. The standard is GB/T9282.1-2008 Transparent liquids are evaluated by platinum-cobalt grade, part one, by preparing platinum-cobalt standard solutions.
2. Moisture test
Tested using the Karl Fischer method.
3. Free acid
Because lithium-ion battery electrolytes contain LiPF6, which decomposes in water to produce HF, and the electrolytes inevitably come into contact with air or moisture during production, manufacturing, transportation, and actual use, free acid is generally tested before leaving the factory and before the battery is filled with electrolyte. The method is very simple: acid-base titration.
4. Density
The density of petroleum products is generally measured using the specific gravity bottle method (GB/T2540). A suitable specific gravity bottle is selected based on the sample. The liquid to be tested is placed in the specific gravity bottle and heated in a constant temperature bath. When the liquid surface no longer changes, excess water is absorbed with filter paper. The sample above the mark is wiped off, the exterior is cleaned, and the sample is weighed. The weight is then calculated using the formula.
5. Color
Color is represented by both brightness and chromaticity. Chromaticity is a property of color that does not include brightness. It reflects the hue and saturation of a color and is also represented by the standard GB/T3143 Liquid Chemical Products Color Determination Method Platinum-Cobalt Color Number. The test method is similar to the appearance test method, which is to obtain the result by measuring with a spectrophotometer and comparing with a standard sample.
