Advances in organic cathode materials for aqueous multivalent metal-ion storage

Abstract

Aqueous metal-ion batteries relying on multivalent charge carriers (Al³⁺, Ca²⁺, Mg²⁺, Zn²⁺) are highly praised for the merits of operational safety and natural abundance, and, more importantly, the intercalation chemistry of these cations enables multi-electron transfer with high energy storage. Very recently, a variety of organic cathode materials have sprung up toward aqueous multivalent metal-ion batteries, accompanied with the on-going exploration of working mechanisms, active materials and electrode modification. In this mini-review, the working mechanisms of aqueous multivalent metal-ion batteries are firstly introduced with a brief comparison of their respective features. Secondly, recent achievements in emerging organic active materials are presented with an emphasis on the interaction between active functionalities and charge carriers. Thirdly, we list some representative design/modification strategies to optimize key evaluation indicators (rate capability, specific capacity, redox voltage and cycle life) of organic cathode materials in aqueous multivalent metal-ion storage. Finally, bottleneck problems and future perspectives are described to promote the development toward sustainable, affordable, and high-performance metal-ion batteries.