A Long-Life Manganese Oxide Cathode Material for Aqueous Zinc Batteries with a Negatively Charged Porous Host to Promote the Back-Deposition of Dissolved Mn2+

Manganese oxide is a promising cathode material for rechargeable aqueous zinc batteries. However, the cycling stability is seriously limited by Mn dissolution. Herein, a negatively charged porous carbon host is proposed for manganese oxide to ensure stable cycling. It is derived from a metal-organic framework with Zn and Mn centers. The organic ligands transform into porous carbon upon calcination, and Zn vaporizes to generate a negatively charged surface. It provides abundant reaction sites, electron transport network, and most importantly, strong attractions towards Mn2+ cations by electrostatic interactions. The Mn2+ dissolved from manganese oxide reversibly deposits back to the cathode as demonstrated by mechanism studies, and active species is preserved for energy storage. In the electrolyte of 3 m ZnSO4 without Mn2+ additives, the composite cathode achieves an ultra-long life over 11 000 cycles at 2 A g(-1). It also delivers 275 mAh g(-1) capacity (based on the total mass of the composite) at 0.1 A g(-1). This work proposes an effective strategy to realize the stable cycling of manganese oxide cathode materials in aqueous zinc batteries.