‌Lithium bis(fluorosulfonyl)imide (LiFSI)

‌Lithium bis(fluorosulfonyl)imide (LiFSI)

LiFSI-powder
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‌Lithium bis(fluorosulfonyl)imide (LiFSI) Powder

‌Lithium bis(fluorosulfonyl)imide (LiFSI) is a new type of lithium salt with excellent electrochemical properties, hydrolysis resistance, thermal stability and conductivity. ‌It is mainly used as an additive in electrolytes, and can also be used alone as an electrolyte. It is regarded as a substitute for lithium hexafluorophosphate (LiPF6).

  • Short name：LiFSI
  • CAS NO.：171611-11-3
  • HS Code：2921199090
  • EINECS No.：924-516-9
  • Molecular Formula：F2LiNO4S2
  • Molecular Weight：187.07
  • Appearance：white crystal or powder
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Technical Specifications

Item Lithium Bis(fluorosulfonyl)imide
Molecular Weight 187.07 g/mol
Purity >99.9%
Water Content <80 ppm
Melting Point 140 °C
Vapor Pressure 27.198-31.064 Pa at 20-25 ℃
Density 1.052 g/cm3 at 25℃
Thermal  
Decomposition >200 °C
Insoluble Substance ≤300 ppm
Free Acid < 5 ppm
Solubility in Water Soluble
Storage Store under inert gas
Condition to Avoid Moisture

Performance Characteristics of LiFSI

LiFSI has high thermal and electrochemical stability, can remain stable at high temperatures, and is not prone to side reactions. Its melting point is 140-145℃, its ionic conductivity is 9.8mS/cm, and its decomposition temperature is higher than 200℃.

  1. High conductivity. The fluoride ions in LiFSI have strong electron-withdrawing properties, which weakens the coordination effect between anions and cations in lithium salts, making lithium ions more active, thereby improving the conductivity of the electrolyte.
  2. High thermal stability. Compared with LiPF6, LiFSI electrolyte exhibits better thermal stability, which means that under high temperature conditions, LiFSI can better maintain battery performance and reduce the possibility of thermal decomposition.   
  3. High electrochemical stability.LiFSI excels in electrochemical stability and can support the battery to operate in a wider operating temperature range, especially in low temperature environments, where its performance is even better.
  4. Hydrolysis resistance. LiFSI has stronger hydrolysis resistance, which makes it more stable in humid environments and reduces harmful side reactions caused by hydrolysis.
  5. Improve cycle life.Due to these characteristics of LiFSI, it can increase the number of charge and discharge cycles of lithium batteries and extend the battery life.
  6. Good chemical compatibility. Compatible with a variety of solvents and additives to reduce battery capacity attenuation.

Application of ‌Lithium bis(fluorosulfonyl)imide LiFSI Powder in Lithium Battery Industry

LiFSI is mainly used in the lithium battery industry, especially in power lithium batteries. It can effectively improve the low-temperature discharge performance and safety performance of lithium batteries, maintain good compatibility with positive and negative electrode materials, and extend the service life of the battery. In addition, LiFSI can also inhibit battery expansion and improve the energy density and safety of the battery.

  • Used as an electrolyte additive

    LiFSI is mainly used as an additive in the electrolyte, which can significantly improve the cycle performance and rate performance of lithium-ion batteries. At the same time, due to its high thermal stability and electrochemical stability, LiFSI can also inhibit the expansion effect of the battery and extend the service life of the battery.

  • Used as an electrolyte

    In addition to being an additive, LiFSI can also be used alone as an electrolyte to provide lithium-ion batteries with higher energy density and better safety. With the rapid development of the new energy vehicle market and the advancement of battery technology, the demand for LiFSI continues to increase. Although the current cost is high, with the advancement of technology and the expansion of the market scale, its price is expected to fall, and the market prospects are broad.

Future Development Trend of LiFSI Electrolyte

The process of replacing LiPF6 is accelerating. In semi-solid/solid-state batteries, LiFSI has become the core material for liquid electrolyte replacement due to its low viscosity and high wettability.

Diversified application scenarios. Penetrate into the fields of sodium-ion batteries, supercapacitors, etc., further broaden the market space.

In summary, LiFSI is upgrading from “additive” to “mainstream lithium salt” with its performance advantages and technological breakthroughs, and may reshape the electrolyte industry landscape in the future.  

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