LiFSI Industry Research On Lithium Battery Materials
- LiFSI has superior performance
- The economy of LiFSI is gradually emerging
- LiFSI synthesis process diversification
Lithium-ion batteries are the main battery type in commercial batteries today, and their important components include electrolyte, positive electrode, negative electrode and separator.
The charging and discharging process of LIB is realized by the intercalation and deintercalation of li-ions back and forth between the battery terminal through the electrolyte. LiFSI as the next generation of solute lithium salt is the future trend.
At present, the mainstream commercial electrolyte is liquid electrolyte (commonly known as electrolyte), which is mainly composed of solute lithium salt, organic solvent and additives. Electrolytes can be divided into solid electrolytes and liquid electrolytes (commonly known as electrolytes) in terms of physical form.
Electrolytes can also be divided into aqueous electrolytes and organic (solvent) electrolytes based on the type of solvent. The electrolytes currently used commercially are mainly organic electrolytes, which are composed of solute, solvent and additives.
LiFSI has superior performance
The choice of solute lithium salt also determines the capacity, operating temperature, cycle performance, power density, energy density and safety of LIB to a large extent. The solute lithium salt is not only responsible for providing free shuttle ions in the LIB and undertaking the role of transporting ions inside the battery.
However, it also needs to interact with the electrode material to form a solid electrolyte film (SEI), so the lithium salt selection of LIB usually considers: ionic conductivity rate, solubility, stability, SEI formation ability, aluminum passivation ability and hydrolysis resistance.
At present, the electrolyte solute lithium salt mainly uses relatively low-cost lithium hexafluorophosphate (LiPF6). As the core component of lithium salt, its electrolyte mass accounts for only about 13%, but it accounts for about 62% of the electrolyte manufacturing cost, so the cost of lithium salt will greatly limit its application in electrolyte.
Solute lithium salts are mainly divided into inorganic lithium salts and organic lithium salts. Compared with organic lithium salts, inorganic lithium salts have fewer manufacturing steps and less difficulty in purification, and have the advantages of low price and low process barriers.
Therefore, lithium hexafluorophosphate whose comprehensive performance meets the current market requirements (LiPF6, hereinafter abbreviated as 6F), with its low cost advantage, the current mainstream solute lithium salt.
Bifluorosulfonimide (LiFSI) has excellent performance, which is in line with the development trend of battery electrolyte in the future. From the perspective of material properties, compared with LiPF6, LiFSI has better electrical conductivity, higher electrochemical and thermal stability, and hydrolysis resistance, and can maintain good battery performance in high temperature environments.
LiFSI can also form a thinner and more uniform SEI in the battery, which can reduce the damage of dendrites to the battery structure and improve stability. Although LiFSI has a corrosive effect on aluminum collector plates, it can be overcome by adding a small amount of additives such as LiODFB to passivate aluminum in advance.
The mixed use of LiFSI and LiPF6 can also improve battery performance by using LiPF6 alone to a certain extent. LiFSI and its derivative NaFSI are also very suitable for future battery systems such as lithium sulfur battery (Li-S), lithium metal batteries (LMB), sodium-ion batteries (SIB) and silicon anode lithium batteries, in line with the development trend of future battery electrolytes .
Therefore, it can be judged that the position of LiFSI in the electrolyte is expected to gradually transition from the current additive (accounting for less than 0.5%) to the lithium salt used alone (accounting for 1%~15%), realizing the technical change of the solute lithium salt link in the electrolyte.
The economy of LiFSI is gradually emerging
The price of 6F has risen sharply, the LiFSI manufacturing process has improved to optimize costs, and the economy of new lithium salts has gradually emerged. With the rapid development of smart cars and energy storage equipment in China, the rapid growth of market demand for LIB has led to a tight supply and demand balance of LiPF6, and the price has entered an upward channel.
LiPF6 has risen from 107,000/ton at the beginning of 2021 to 525,000/ton , an increase of 390.6%. Due to the limited maturity of the process and the high price of LiFSI due to the low yield of the product, its application in the market is limited. The cost and selling price are gradually decreasing. The market price in 2020 is about 400,000 RMB/ton, which is less than half of the price in 2016. The price difference between LiFSI and LiPF6 is gradually narrowing.
It is estimated that the LiFSI market space is expected to exceed 30 billion RMB in 2025. With the development of the new energy industry, it is expected that the demand for LIB in the world will continue to grow, and the demand for electrolyte will also increase further. In this way, there are more and more electrolyte companies. The article top 10 battery electrolyte companies in China will help you to know.
According to the environmental assessment information of Tinci Materials and Xinzhoubang, the demand for solute lithium salt per ton of electrolyte is basically maintained at 0.126 tons, but with the continuous improvement of battery energy density requirements, the proportion of organic solvents in electrolyte will decrease, and the solute lithium salt proportion will increase in disguise.
According to the forecast of the installed capacity of LIB in the world by the New Energy Vehicle Group of the Research Department of CITIC Securities, it is estimated that the total demand for solute lithium salt in the world in 2025 is about 258,300 tons. It is believed that LiFSI, as a lithium salt, will replace part of LiPF6, and the market penetration rate is expected to reach 50% in 2025.
LiFSI synthesis process diversification
The LiFSI synthesis process is diversified
The LiFSI industry has entered a stage of rapid development. Research on the industrial synthesis of LiFSI by Chinese companies began around 2015, and production capacity was gradually implemented in 2017. At present, major companies in the world have begun to invest in large-scale LiFSI production capacity.
The process control of chlorosulfonic acid method is less difficult, and the proportion of market adoption is large. The three links in the chlorosulfonic acid method are relatively independent, while the sulfamide method can shorten the link to two steps or even one step, which has obvious advantages in efficiency.
In the sulfuryl fluoride method, the feed temperature is generally required to be lower than room temperature, and the temperature during the reaction is generally maintained at about 25°C. However, its reaction will release a lot of heat and form solid salt, which makes it difficult to transfer the heat quickly, which undoubtedly increases the difficulty of process control.
The reaction of ammonium fluoride and imine dichlorosulfonate is a liquid phase reaction, which is easier to carry out than the gas-liquid two-phase reaction. Usually, no catalyst is added, and the reaction time is short, but it will introduce heteroions into the system, requiring additional purification steps.
Significant technological progress of LiFSI
The current manufacturing cost of the old LiFSI process is about 270,000/ton. Because the sulfuryl fluoride method is relatively small, the specific information in the actual production of this process is less disclosed, and the cost is difficult to calculate.
The current manufacturing cost of the new LiFSI process has dropped to about 120,000/ton. At present, the LiFSI process belongs to the rapid development stage, and the update is relatively fast, and the LiFSI yield is also rising rapidly.
The manufacturing cost of LiFSI by chlorosulfonic acid method can be controlled at about 120,000 RMB/ton, of which raw material cost and energy cost are the main production costs, accounting for about 56% and 21% of the total production cost respectively. Taking into account the progress of the process since 2019, the current manufacturing cost of LiFSI is likely to be further reduced.
LiFSI still has room for cost reduction and process optimization
At present, in the LiFSI manufacturing process, the use efficiency of some core raw materials is low, and there is still a lot of room for improvement in the future. Compare the actual consumption of materials in the EIA with the theoretical consumption level of materials calculated based on chemical equations.
The first step of LiFSI synthesis (HCISI/HFSI synthesis step) is all raw materials except thionyl chloride, such as chlorosulfonic acid isocyanate, sulfamic acid, chlorosulfonic acid, etc., and the fluorinating agent in the second step of fluorination, such as hydrogen.The use efficiency of core raw materials such as hydrofluoric acid (hydrogen fluoride) and potassium fluoride is relatively low, both around 50%.
In the future, the cost of chlorosulfonic acid method per ton of LiFSI is expected to be reduced to about 100,000. From the previous analysis, it is known that multiple core raw materials in the manufacturing process based on thionyl chloride and based on chlorosulfonic acid isocyanate all have the problem of low utilization rate.
According to the maturity of LiPF6 process (raw material utilization efficiency is about 90%), the LiFSI cost of two subdivided chlorosulfonic acid process routes is predicted. Considering the further optimization of labor cost and depreciation cost, the future LiFSI manufacturing cost is expected to drop to about 100,000 RMB/ton.