Demand Promotes Development: Will LiFSI Replace LiPF6 as the Mainstream Solute Lithium Salt?

SHANGHAI, Jul 6 (SMM) - The electrolyte is mainly composed of solute lithium salt, organic solvent and additives. The choice of solute lithium salt largely determines the capacity, operating temperature, cycling performance, power density, energy density and safety of the lithium battery. Solute lithium salts are mainly divided into inorganic lithium salts and organic lithium salts. Compared to organic lithium salts, inorganic lithium salts have fewer manufacturing processes and lower purification difficulties, and have the advantages of low price and low process barriers.

Lithium hexafluorophosphate (LiPF6) is now the dominant solute lithium salt due to its low cost, while lithium bis(fluorosulfonyl)imide (LiFSI) is currently a hot topic in the lithium battery industry.

LiFSI mainly exists as a solute in the electrolyte of lithium batteries, which is also its main application. At present, the downstream customers of LiFSI industry include power battery plants and new energy vehicle enterprises, including LG, Samsung, Panasonic and other well-known new energy battery manufacturers as well as Volkswagen, Toyota, etc.

The study of LiFSI first started overseas, and NIPPON SHOKUBAI began to develop the industrial synthesis method of LiFSI as early as in 2009; after that, European and American companies such as Arkema also stepped into the development of LiFSI synthesis process. The research of LiFSI in China is late in development. Jiangsu Huasheng successfully mastered the synthesis technology of LiFSI in 2012; around 2015, the research and development of mass production accelerated, and was gradually translated into actual production capacity in 2017.

In 2020, there were 8 major domestic LiFSI producers in China, with most production capacity held by Tianci Materials (002709), Shanghai Chemspec Corporation and DFD Chem (002407), among which Tianci Materials has a market share of 36% and the CR3 concentration of LiFSI production capacity is 73%. In the next 5 years, 98% of the planned new LiFSI production capacity worldwide will be found in China, with Tianci Materials, Yongtai Technology (002326) and Growth Enterprise Market (300037) ranking among the top three brands in terms of new production capacity. The expected new capacities in the following 3-5 years will be 60,000 mt, 20,000 mt and 10,000 mt respectively.

In terms of material properties, LiFSI has better electrical conductivity, higher electrochemical and thermal stability and resistance to hydrolysis compared to LiPF6. The addition of LIFSI can significantly increase the charge and discharge cycles of the battery and keep extremely active electrode materials such as high nickel cathodes and high voltage cathodes stable, thus extending the battery life, while improving the flame retardance of the electrolyte and improving the safety.

In terms of downstream applications, Tesla's "4680" battery has started mass production and the upgrade of the new battery technology has enabled LIFSI to be rapidly introduced into the industry chain. The "4680" refers to a large ternary cathode cylindrical battery that is 46mm wide and 80mm long. According to the data released by Tesla, the "4680" battery can increase the battery capacity by 5 times, the mileage by 16% and reduce the cost by 14% on the basis of the "2170" battery.

At present, CATL has planned eight "4680" production lines, totaling 12GWh; Panasonic will start trial production of "4680" batteries next year; LG Chem's 4680 cell trial production line is now under construction and will achieve mass production in 2023 at the earliest; EVE Energy’s planned 20GWh capacity will be put into production next year at the earliest.

The promotion of the "4680" battery is expected to elevate the silicon content in the anode, as the conductivity of silicon-carbon anode is poor. LiFSI is expected to accelerate the replacement of LiPF6 as a new additive due to its better thermal and electrochemical stability and higher electrical conductivity. LiFSI is only about 3% in normal high nickel NMC battery, but in "4680" battery the amount is directly increased to 15%.

As the core component of the electrolyte, the choice of solute lithium salt largely determines the performance of lithium batteries. Currently, the low-cost inorganic lithium salt LiPF6 dominates the market, but it is gradually failing to keep up with the development of lithium batteries due to its chemical instability and lack of efficiency in low temperature environments. LiFSI, due to its high temperature stability and high conductivity, will be used more often in innovative batteries, and may become the best choice to replace LiPF6 with the mass production of 4680 battery and Qilin battery.