Preparation of lithium salt lithium bis(fluorosulfonyl)imide (LiFSI) and prospects for its application in lithium batteries

The electrolyte of lithium batteries is one of the key factors in battery performance. Its composition directly affects the safety performance, charge and discharge efficiency and service life of the battery. Among the many electrolyte components, lithium bis(fluorosulfonyl)imide (LiFSI) has gradually become a research hotspot due to its unique physical and chemical properties. This article will deeply explore the raw materials of lithium bis(fluorosulfonyl)imide and its application prospects in lithium batteries.

1. Ethylene carbonate

The molecular formula is C3H4O3. It is a transparent, colorless liquid that is a crystalline solid at room temperature. Its boiling point is 248°C/760mmHg, or 243-244°C at 740mmHg. The flash point is 160°C, the density is 1.3218, the refractive index is 1.4158 (50°C), and the melting point ranges from 35-38°C. Ethylene carbonate is an excellent solvent for polyacrylonitrile and polyvinyl chloride, and is often used in spinning liquid in the textile industry. It can also be directly used as a solvent for removing acidic gases, as well as an additive for concrete. In the medical field, it is used as an important component and raw material for pharmaceuticals. In addition, it is also a stabilizer for plastic foaming agents and synthetic lubricants. In the battery industry, ethylene carbonate is widely used as an excellent solvent for lithium battery electrolytes.

2. Propylene carbonate

Its molecular formula is C4H6O3. This chemical substance is in the form of a colorless or light yellow transparent liquid and is soluble in water and carbon tetrachloride. It is also miscible with organic solvents such as ether, acetone, and benzene. It is widely regarded as a high-quality polar solvent and plays a key role in many fields, such as polymer operations, gas separation processes, and electrochemical applications. In particular, propylene carbonate performs well in absorbing carbon dioxide from natural gas and synthetic ammonia raw materials in petrochemical plants. It can also be used as a plasticizer, spinning solvent, and extractant for olefins and aromatics. In terms of toxicological data, animal experiments have confirmed that no signs of poisoning were found in oral or skin contact, and the oral LD50 of rats reached 29000mg/kg. In addition, to ensure safety, this product should be stored in a cool, ventilated and dry environment, away from fire sources, and follow the storage and transportation regulations of general low-toxic chemicals.

3. Diethyl carbonate

Its molecular formula is CH3OCOOCH3. This chemical is in the form of a colorless liquid with a slight odor. At 23.8°C, its vapor pressure is 1.33 kPa, while its flash point is 25°C, indicating that this substance easily evaporates and mixes with air when the temperature rises, thus posing a fire risk. Its melting point is -43°C and its boiling point is 125.8°C. Diethyl carbonate is insoluble in water, but it is miscible with organic solvents such as alcohols, ketones, and esters. This substance has a relatively large density and good stability. It has a wide range of applications in organic synthesis and as a solvent.

In addition, most of the lithium salts used in lithium-ion batteries, such as LiPF6, LiBF4, LiClO4, etc., have the characteristics of easy hydrolysis and poor thermal stability. However, lithium bis(fluorosulfonyl)imide (LiFSI), as a new type of lithium salt, has shown excellent comprehensive performance. Its synthesis process is advanced. It is obtained by fluorinating bis(chlorosulfonyl)imide with a fluorinating agent to obtain bis(fluorosulfonyl)imide, and then further lithiation reaction. Compared with traditional lithium hexafluorophosphate, LiFSI has higher conductivity, excellent thermal stability and good high and low temperature performance in the electrolyte. Therefore, the application of LiFSI in the electrolyte can significantly improve the cycle life, rate performance and safety of lithium batteries, which meets the needs of the future development of lithium batteries.

Therefore, LiFSI is expected to become an indispensable additive in lithium batteries, partially replacing traditional LiPF6. Although the current production process of LiFSI is relatively complex and costly, with the maturity of the production process and the release of production capacity in the future, its production cost and market price are expected to drop significantly, thereby improving its cost performance. In addition, the continuous updating and iteration of lithium battery technology has also brought broad development space for LiFSI. Many domestic companies have actively laid out the research and development and production of LiFSI to accelerate its penetration in the lithium salt field. With the rapid development of the new energy vehicle market, the new lithium salt market will also usher in important growth opportunities.

 At present, many domestic companies have mastered the preparation technology of LiFSI.  They usually synthesize bis(chlorosulfonyl)imide first, then react with fluorinated metal salts, and finally obtain LiFSI after a series of chemical reactions.

Domestic production capacity of lithium bis(fluorosulfonyl) imide has reached about 21,700 tons. Many well-known companies have already laid out in this field and have considerable production capacity. Newcomers in the industry have also joined in, jointly promoting the prosperity of the lithium bis(fluorosulfonyl)imide market.

In addition, the rapid development of the new energy vehicle industry and the continued prosperity of the electrolyte market have jointly promoted the vigorous development of the upstream lithium salt market. The continuous expansion of the production scale of lithium bis(fluorosulfonyl)imide will undoubtedly further reduce its production cost, thereby making it more widely used in lithium battery electrolytes.

Jiayuan should continue to understand the market situation, do a good job of research, find its own position in the lithium battery market, highlight its own advantages, and improve the core competitiveness of the company!