High Concentration Electrolyte Based On LiFSi Improves The Performance of Dual ion Batteries

The dual ion battery is a new type of secondary battery using anion-embedded graphite as the positive electrode, such as a dual-carbon battery. Dual-ion batteries have been the focus of research in recent years. Compared with lithium-ion batteries, they have the advantages of easy availability of positive electrode materials, stable structure, high reversible potential, and environmental friendliness, and have become the focus of research in recent years.

The unique structure and discharge principle of the dual-ion battery require that the electrolyte not only has a wide electrochemical window and good high voltage stability, but also form a stable SEI film on the surface of the negative electrode material to increase the stability of the battery. The electrolytes used for dual ion batteries mainly include quaternary ammonium salt organic electrolytes, ionic liquids and lithium salt organic electrolytes. Among them, the lithium salt organic solvent electrolyte is the main body of the current commercial electrolyte, but most of the electrolyte systems based on LiPF ₆ salt are not ideal in dual-ion batteries.

Based on this, Yongbing Tang from the Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, and Professor Zhiming Zhou from Chongqing University of Technology synthesized 7.5 m lithium bis(fluorosulfonyl)imide (LiFSi) in a carbonate electrolyte system and verified its presence in aluminum Practical value in dual ion batteries.

Based on the concept of this concentrated electrolyte, the discharge capacity of the dual ion battery at 200 mAg ^-1 was 94.0 mAhg ^-1, and the capacity retention rate after 500 cycles was 96.8%. By counting electrode materials and electrolytes, the energy density of this new dual-ion battery is as high as 180 Whkg^-1, which achieves the best performance of the previously reported dual-ion battery.

In short, this highly concentrated electrolyte enhances the intercalation ability and cycle stability of the graphite cathode, while optimizing the structural stability of the aluminum anode, greatly increasing the energy density of the battery.

References: Li Xiang, et al, Highly Concentrated Electrolyte towards Enhanced Energy Density and Cycling Life of Dual-Ion Battery, Angew. Chem. Int. Ed.DOI: 10.1002/anie.202006595