Electrode and Electrolyte Interaction in Aqueous Electrochemical Energy Storage

Abstract

Aqueous rechargeable electrochemical energy storage (EES) devices using earth‐abundant transition metal oxides and Na or K ion as charge carriers could fulfill requirements for stationary energy storage, where low cost and environmental sustainability of the storage technologies become imperative. In order to meet the demands of large‐scale stationary storage, considerable efforts have been devoted to the development of advanced electrode materials for aqueous EES devices with competitive energy and power performance to their nonaqueous counterparts. Although efforts have been made in the development of novel electrode materials and aqueous electrolytes, fundamental rules governing the interaction between electrodes and aqueous electrolytes remain poorly understood. Some critical understanding underscoring the performance of aqueous EES devices is needed in order to address present challenges of aqueous systems, including low storage capacity of the electrode and limited potential window (∼1.23 V) due to water decomposition. Moreover, the structural details of electrodes resulted from the interaction with aqueous electrolytes are still far from elucidation; hence establishing structure–property relationships for advanced studies of aqueous EES systems is still largely a trial‐and‐error process. This article reviews the recent progress in controlling the interaction between electrode materials and electrolytes to improve the performance of aqueous EES devices. Particularly, this article focuses on (i) how interphase formed due to the interaction of electrodes and electrolytes widens the potential window of aqueous EES systems to reach a kinetically stable potential window well above 1.23 V and (ii) how the interaction between disordered electrode and water affects the stability of the electrode and improve the electrokinetics of charge storage.