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What additives need to be added to the lithium battery electrolyte?

2019-01-21 来源:亚科官网

Lithium battery is the best comprehensive battery system at present. The advantages of lithium battery are mainly light weight, small volume and high discharge voltage. Compared with other types of batteries, it also has the advantages of environmental protection, long life and high specific energy. Therefore, it is increasingly recognized by people, and the scope of application is more and more extensive. As one of the essential raw materials for lithium batteries, lithium battery electrolyte is very important.

What lithium battery electrolyte is?

Lithium battery electrolyte is also called as the blood of lithium battery. It mainly plays the role of transferring charge in lithium battery. It has a great influence on the safety performance, cycle efficiency, specific capacity and production cost of lithium battery. It is one of the important constituent materials of lithium batteries. Usually, the electrolyte of lithium battery is composed of electrolyte (that is, a lithium salt) and organic solvent.

The Types of Lithium battery electrolyte additive

Adding some functional additives to the lithium battery electrolyte can improve the performance of the lithium battery, and the functions of different kinds of additives are also different. Lithium battery electrolyte additives can be classified into two types: inorganic additives and organic additives. The organic additive has better effect than the inorganic additive, is more convenient to use, and has better miscibility with the lithium battery electrolyte, and thus is more widely used. Additives can also be classified into solid, gaseous, and liquid additives depending on the state standing at room temperature. It can also be distinguished from the functions, including flame retardant additives, film forming additives, conductive additives, additives for controlling water, overcharge protection additives, multifunctional additives, etc.

Synthesis technology of battery electrolyte additive

1) vinyl carbonate

vinyl carbonate (VC) is an unsaturated organic compound, which contains sub-ethylene and is an organic film-forming additive. It is an electrolyte additive with the best effect, the deepest research and wide application. The preparation process comprises the following steps: converting vinyl carbonate to vinyl chlorocarbonate by chlorination reaction, and then producing crude sub-vinyl carbonate by dechlorination reaction, and finally purifying the product. Chlorine gas, solid phosgene, sulfuryl chloride, etc. can be used as a chlorinating agent for vinyl carbonate, and chlorinated to prepare ethylene chlorocarbonate by adding an initiator or irradiating with an ultraviolet lamp.

2) Vinyl fluorocarbonate

Vinyl fluorocarbonate is a new type of electrolyte additive. Its principle of action is to form a SEI film with better performance on the surface of the carbon electrode to protect the carbon electrode and inhibit the decomposition of the electrolyte to achieve the effect of improving battery performance and lithium battery cycle.

In the current production method of vinyl fluoroethylene, the main difference is that the fluorinating agent. When a mixed gas of fluorine gas and nitrogen gas is used as the fluorinating agent, it can be reacted with vinyl carbonate to form a vinyl fluorocarbonate. However, it should be noted that fluorine gas is a highly toxic gas, and its reactivity is high. When it reacts, it will generate heat intensely, and there are certain safety hazards. A method of adding vinyl fluoroethylene to vinyl carbonate can be used to lower the freezing point of the mixture, thereby lowering the temperature of the reaction, and effectively reducing the possibility of occurrence of a safety accident. When an alkali metal fluoride is used as the fluorinating agent, fluoroethylene carbonate can be produced by reacting with chloroethylene carbonate.

Edited by Suzhou Yacoo Science Co., Ltd.