Lanzhou Chemical has made new progress in the research of safe high-rate supercapacitors

Supercapacitors are important energy storage devices that have limited application due to their low energy density. An effective strategy to increase the energy density of supercapacitors is to use an organic electrolyte with a wide voltage window. However, conventional organic electrolytes have high cost, low electrical conductivity, and have safety hazards. Relatively speaking, the water-based electrolyte has the characteristics of safety, low cost and easy operation. However, the voltage window of the aqueous electrolyte is narrow, resulting in a low energy density of the water-based supercapacitor.

Recently, researchers have developed a class of high-concentration “water in salt” aqueous electrolytes with large stable voltage windows. However, such electrolytes have problems of high viscosity, low electrical conductivity, and low temperature, which greatly limit the performance of supercapacitors prepared using such electrolytes. In summary, the design of a new electrolyte system, the preparation of safe, wide voltage window, high conductivity, wide application temperature range of electrolyte, will certainly help improve the performance of supercapacitors.

Recently, the team of researcher Yan Xingbin from the Laboratory of Clean Energy Chemistry and Materials, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, developed a method for preparing mixed electrolytes. An "acetonitrile/water in salt" (AWIS) mixed electrolyte was prepared by adding a cosolvent acetonitrile to a typical "water in salt" (WIS; 21 m LiTFSI/H2O) electrolyte. Compared with WIS electrolyte, AWIS mixed electrolyte has low viscosity, high electrical conductivity and wide application temperature range. At the same time, the AWIS mixed electrolyte maintains a wide voltage window, is non-flammable and easy to operate. Using the AWIS mixed electrolyte, the researchers assembled a safe, wide-window, high-magnification supercapacitor.

This work provides a strategy for mixing a salt with a water/organic solvent to prepare a new electrolyte. The electrolyte prepared based on this strategy is expected to be used to construct high performance energy storage devices such as supercapacitors, metal ion hybrid capacitors, and metal ion batteries. . Research work was recently published online in Energy & Environmental Science (DOI: 10.1039/C8EE01040D).

The above work has been funded and supported by the National Natural Science Foundation of China, the “One-Three-Year” Strategic Planning Key Cultivation Project of the Chinese Academy of Sciences, and the Western Light of the Chinese Academy of Sciences.