A Desolvated Solid-Solid-Solid Interface for a High-Capacitance Electric Double Layer

Understanding the electric double layer is essential for achieving efficient electrochemical energy storage technologies. A conventional solid-liquid electrode interface suffers from serious self-discharge and a narrow voltage window, which makes the development of a solid-solid interface imperative. However, an in-depth understanding of the electric double layer with a solid- solid interface is lacking. Here, a solid-solid interfacial electric double layer is proposed with excellent electrochemical performance. The solid layer is constructed by the electrochemical decomposition of lithium difluora(oxalate) borate, which provides a desolvated environment for the establishment of a electric double layer. This makes a stronger interaction between the electrode surface and the ions. Based on this unique property, it is found that the solid- solid interfacial electric double layer has an increased capacitance, which suggests a way to develop high-energy electrochemical capacitors.