An Organic Coordination Manganese Complex as Cathode for High-Voltage Aqueous Zinc-metal Battery.

Abstract

Aqueous Zn-Mn battery has been considered as the most promising scalable energy-storage system due to its intrinsic safety and especially ultralow cost. However, the traditional Zn-Mn battery mainly using manganese oxides as cathode shows low voltage and suffers from dissolution/disproportionation of the cathode during cycling. Herein, for the first time, a high-voltage and long-cycle Zn-Mn battery based on a highly reversible organic coordination manganese complex cathode (Manganese polyacrylate, PAL-Mn) was constructed. Benefiting from the insoluble carboxylate ligand of PAL-Mn that can suppress shuttle effect and disproportionationation reaction of Mn3+ in a mild electrolyte, Mn3+ /Mn2+ reaction in coordination state is realized, which not only offers a high discharge voltage of 1.67 V but also exhibits excellent cyclability (100 % capacity retention, after 4000 cycles). High voltage reaction endows the Zn-Mn battery high specific energy (600 Wh kg-1 at 0.2 A g-1 ), indicating a bright application prospect. The strategy of introducing carboxylate ligands in Zn-Mn battery to harness high-voltage reaction of Mn3+ /Mn2+ well broadens the research of high-voltage Zn-Mn batteries under mild electrolyte conditions.