LiFSI vs LiPF6 comparison and LiFSI market prospect

With people's growing concern for a green and low-carbon economy, lithium batteries have received widespread attention. LiFSI is considered to be a new type of fluorine-containing lithium salt that has the potential to become the main component of electrolytes for next-generation lithium batteries. Compared with LiPF6, LiFSI has a higher decomposition temperature, and studies have shown that LiFSI contains F-P bond anions, which can reduce the corrosion of the electrolyte on the current collector. These advantages make LiFSI attract much attention from academia, industry and lithium battery electrolyte companies.

1. Limitation of LiPF6 and development of LiFSI

At present, LiPF6 is still the key material and the core of the electrolyte for lithium-ion batteries. This product has the advantages of high electrical conductivity, but at the same time, it also has disadvantages such as poor thermal stability, harsh preparation process, and poor high and low temperature performance. Considering the development trend of high-nickel and high-voltage lithium batteries in the future, the requirements for the safety and energy density of lithium batteries are gradually increasing. LiPF6 may not be able to meet the demand in the future, and new lithium salts are constantly being developed.

Compared with LiPF6, these new lithium salts often have higher thermal stability, better high and low temperature discharge performance, and their physical and chemical properties can better meet the development trend of lithium batteries. There are many problems in LiPF6, which limit its application scenarios. First of all, LiPF6 is very sensitive to water. When the water content is overtime, it will react to generate HF, which will corrode the internal components of the battery and reduce the service life of the battery. Therefore, it has a high requirement for environmental water content. Secondly, LiPF6 has poor high temperature performance.

Studies have shown that compared with untreated LiPF6, the battery capacity after storage at 85°C and then assembled has a significant decrease, which hinders the application in high temperature environments. In addition, LiPF6 has poor rate performance, making it difficult to apply to applications that require fast charging. These disadvantages need to be solved urgently, and new lithium salts need to be developed in order to broaden the application scenarios. LiFSI has excellent performance and is more suitable for fast charging and high battery life.

Aiming at the above-mentioned performance shortcomings of LiPF6, a variety of new lithium salts have been developed, among which LiFSI has the fastest development and the best application prospect. At present, LiFSI is mainly used as an electrolyte additive mixed with LiPF6 in a small amount, and the overall dosage is small. Compared with LiPF6, LiFSI is more excellent in electrolyte conductivity, high and low temperature performance, thermal stability, hydrolysis resistance, and inhibition of gas expansion, so it is also regarded as one of the most promising lithium salts to replace LiPF6.

2. LiFSI vs LiPF6 - which is better

LiFSI has the following advantages:

• LiFSI has a larger anion radius, which makes it easier to dissociate lithium ions, thereby improving the conductivity of lithium-ion batteries;
• When the temperature is greater than 200 °C, LiFSI can still exist stably without decomposition, and has good thermal stability, thereby improving the safety performance of lithium-ion batteries;
• The electrolyte with LiFSI as the electrolyte maintains good compatibility with the cathode and anode materials, which can significantly improve the high and low temperature performance of lithium-ion batteries.

Among the new lithium salts, LiFSI is one of the new lithium salts with relatively bright development prospects. This is not only due to the excellent physical and chemical properties of LiFSI, but also due to the continuous improvement of the production process of LiFSI as Chinese companies increase investment in research and development, and has successfully achieved a breakthrough in industrialization technology.

3. LiFSI global market accelerates

LiFSI can be used as an electrolyte additive for lithium-ion batteries and can be used in the electrolyte of rechargeable lithium batteries. LiFSI can effectively reduce the high and low temperature resistance of the SEI layer formed on the surface of the electrode plate at low temperature, and reduce the capacity loss of the lithium battery during placement, thereby providing high battery capacity and electrochemical performance of the battery. LiFSI can also be used as an electrolyte for primary batteries and as a polymerization catalyst. LiFSI can also be used as an antistatic agent in the industrial field.

However, due to the late start of research and development and application of LiFSI, and its complex synthesis process and low yield rate, the current application cost is relatively high, and the proportion of large-scale commercial application is still low. Recently, on the one hand, the development of new energy vehicles is accelerating, and it is an inevitable trend to increase the energy density of batteries. On the other hand, as the technology matures and develops, the price of LiFSI continues to decline, and the price difference between LiFSI and lithium hexafluorophosphate is gradually narrowing.

Therefore, the popularity of LiFSI has rapidly increased recently. According to relevant data statistics and forecasts, global electrolyte shipments are showing a rapid growth trend. In 2021, the total global electrolyte output will be 563,200 tons, and the total global electrolyte demand in 2022 is expected to exceed 900,000 tons. The total global electrolyte demand is expected to exceed 1.17 million tons in 2023, and the global total electrolyte demand in 2024 is expected to exceed 1.54 million tons.

According to the current market response, the replacement ratio of LiFSI is gradually increasing. In 2022, the usage ratio of LiFSI is about 1%, and it is expected that by 2025, the usage ratio of LiFSI will exceed 9%. In 2023, the total global demand for LiFSI will reach 55,000 tons, and in 2025, the total global demand for LiFSI will reach 186,000 tons.

4. Future prospects for LiFSI

In the future, the replacement ratio of LiFSI will gradually increase. First, with the improvement of technology level and large-scale production of LiFSI manufacturers, the advantages of scale effect are highlighted, and the cost will be lowered accordingly. The price of LiFSI is expected to be further reduced. Second, the high-end battery market has high performance requirements for battery products, and LiFSI can better meet the terminal market's requirements for battery capacity density. Third, it is expected that the price of LiFSI will fall rapidly in 2024 due to the surplus of supply.

Therefore, once the price of LiFSI is comparable to the price of lithium hexafluorophosphate, and the performance of LiFSI is better at the same price level, the substitution effect of LiFSI on lithium hexafluorophosphate will be more obvious in the future. At present, when many lithium battery companies in the world purchase electrolyte, the proportion of LiFSI used in the electrolyte formula is gradually increasing. The frequency of LiFSI use in the laboratory is increasing, and the R&D team of the battery factory is also paying more and more attention to LiFSI. It is believed that LiFSI will capture most of the lithium hexafluorophosphate market in the near future.

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