Building better aqueous Zn-organic batteries

As potential alternatives to conventional inorganic materials, organic compounds are attractive for use as the cathodes of aqueous zinc-ion batteries (ZIBs), due to their high theoretical capacities, structural tunability, controllable synthesis and environmental friendliness. Herein, a systematic overview focusing on recent developments, energy storage mechanisms, and design and improvement strategies for aqueous Zn-organic batteries (ZOBs) is presented. In this review, we first summarize the ion storage mechanisms of aqueous ZOBs in detail, and then introduce the main methods for analyzing their dynamic behavior. Then, we systematically summarize the latest advances and design strategies for existing organic electrode materials based on their ion storage mechanisms and molecular structural characteristics, including n-type, p-type and bipolar-type electrode materials. Subsequently, for the first time, we summarize the main synthesis strategies of these organic electrode materials. Furthermore, we highlight the existing strategies to improve aqueous ZOBs to obtain higher electrochemical performance in terms of their specific capacity, working voltage, rate performance and cycle life, and to achieve lower preparation costs. Finally, the challenges for aqueous ZOBs to realize their practical application are discussed. Accordingly, rational perspectives and promising exploration directions for aqueous ZOBs are proposed to guide research towards practical applications, achieving a greener rechargeable world.