In traditional batteries, the electrolytic liquid system usually USES water as the solvent, but since the theoretical decomposition voltage of water is 1.23v, considering the overpotential of hydrogen or oxygen, the highest battery voltage of the electrolytic liquid system using water as the solvent is only about 2V (for example, lead-acid batteries).In lithium ion batteries, the operating voltage of the battery is usually as high as 3~4V, and the traditional aqueous solution is no longer applicable. Therefore, non-hydroelectrolytic liquid system must be used as the electrolyte of lithium ion batteries.The non-aqueous organic solvent is the main component of the electrolyte.

Electrolyte additives are mainly classified：

1. The excellent SEI film (solid electrolyte film) has organic solvent compatibility, allowing lithium ions to enter and exit the electrode freely while solvent molecules cannot pass through, thus preventing the destruction of the electrode caused by co-insertion of solvent molecules, and improving the battery’s cycling efficiency and reversible capacity.
2. The research on additives to improve the conductivity of electrolyte mainly focuses on improving the dissolution and ionization of conductive lithium salts and preventing the destruction of electrode by solvent co-insertion.
3. As a commercial application, the safety of lithium ion battery is still an important factor restricting its application development.Lithium ion battery itself has a lot of safety risks, such as high charging voltage, and electrolyte for organic flammable, if the use of improper, the battery will occur dangerous or even explosion.Therefore, improving the stability of electrolyte is an important method to improve the safety of lithium ion battery.Adding some high boiling point, high flash point and non-flammable solvent to the battery can improve the safety of the battery.

In general, the solvent system, the role of additives, lithium properties, water acidity control, compatibility with electrode materials, and so on jointly determine the performance of the electrolyte.Electrolyte is an important part of lithium ion battery, so grasp the electrolyte component is the key to give full play to the battery performance.