Supercapacitors are important energy storage devices due to their low energy density, which limits their application. An effective strategy for increasing the energy density of supercapacitors is to use organic electrolytes with a wide voltage window. However, conventional organic electrolytes are costly, conductance The rate is low, and there are safety hazards. Relatively speaking, the water-based electrolyte has the characteristics of safety, low cost and easy operation. However, the voltage window of the water-based electrolyte is narrow, resulting in 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 high viscosity, low electrical conductivity, and are not suitable for low temperature problems, which greatly limits the problem. Performance of supercapacitors prepared using this type of electrolyte. In summary, designing a new electrolyte system, preparing a safe, wide voltage window, high conductivity, and a wide application temperature range will definitely help improve the super Capacitor performance.
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. By using a typical 'water in salt' (WIS; 21 m LiTFSI/H2O) electrolyte The 'acetonitrile/water in salt' (AWIS) mixed electrolyte was prepared by adding the cosolvent acetonitrile. Compared with the WIS electrolyte, the AWIS mixed electrolyte has low viscosity, high electrical conductivity and wide application temperature range. Meanwhile, AWIS mixed electrolyte Maintains a wide voltage window, non-flammable and easy to operate. Using this AWIS hybrid 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. The 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 Chinese Academy of Sciences's “One Three Five” Strategic Planning Key Cultivation Project and the Western Light of the Chinese Academy of Sciences.
Figure 1. Physical and chemical properties of AWIS electrolyte
Figure 2. Analysis of electrolyte structure
Figure 3. Electrochemical performance of a supercapacitor
