A strategic way of high-performance energy storage device development with environmentally viable “Water-in-salt” electrolytes

Development of cost-effective and environmental friendly energy storage devices (ESDs) has attracted widespread attention in recent scenario of energy research. Recently, the environmentally viable “water-in-salt” (WiS) electrolytes has received significant interest for the development of advanced high performance ESDs. The WiS electrolyte exhibits wide electrochemical stability window (ESW), high-safety, non-flammability and superior electrochemical performance compared to the conventional “salt-in-water” electrolytes. This review aims to provide a comprehensive discussion on WiS electrolyte based on theoretical, electrochemical and physicochemical characteristics. A strategic way for the usage of WiS electrolyte in rechargeable metal-ion batteries and supercapacitors with potentially improved electrochemical performance has been reviewed systematically. This review also discussed the unique advantages of WiS electrolytes as well as the future scope and challenges.