An inverse-spinel Mg2MnO4 cathode for high-performance and flexible aqueous zinc-ion batteries

Abstract

Aqueous zinc-ion batteries (AZIBs) have gained extensive attention owing to low cost and high safety but their development has reached a bottleneck due to the limited number of suitable cathode materials available. Here, we report an inverse-spinel-structured Mg₂MnO₄ nanosheet cathode for AZIBs. Mn⁴⁺-rich Mg₂MnO₄ allows remarkable discharge capacity and structure stability. Thus, the Zn//Mg₂MnO₄ battery exhibits a high discharge capacity of 371.7 mA h g⁻¹ at 150 mA g⁻¹ and excellent long-cycle life over 500 and 2000 cycles with no obvious capacity fading at 1500 and 3000 mA g⁻¹, respectively. Moreover, the Mg₂MnO₄ electrode exhibits a Zn²⁺/H⁺ deintercalation/intercalation mechanism during the charging/discharging process, resulting in fast ion-transfer kinetics. In addition, copolymerized 2-acrylamido-2-methylpropane sulfonic acid–acrylamide (P-APSA) hydrogel electrolyte is utilized to fabricate a flexible Zn//P-APSA//Mg₂MnO₄ battery. Benefitting from the good compatibility and high adhesion between the P-APSA hydrogel and Zn anode, the battery exhibits impressive electrochemical performance. This work provides an option to design high-performance AZIBs for durable applications.