Tunable Layered (Na,Mn)V8O20·nH2O Cathode Material for High‐Performance Aqueous Zinc Ion Batteries

Rechargeable aqueous zinc-ion batteries (ZIBs) show promise for use in energy storage. However, the development of ZIBs has been plagued by the limited cathode candidates, which usually show low capacity or poor cycling performance. Here, a reversible Zn//(Na,Mn)V8O20·nH2O system is reported, the introduction of manganese (Mn) ions in NaV8O20 to form (Na,Mn)V8O20 exhibits an outstanding electrochemical performance with a capacity of 377 mA h g-1 at a current density of 0.1 A g-1. Through experimental and theoretical results, it is discovered that the outstanding performance of (Na,Mn)V8O20·nH2O is ascribed to the Mn2+/Mn3+-induced high electrical conductivity and Na+-induced fast migration of Zn2+. Other cathode materials derived from (Na,Mn)V8O20·nH2O by substituting Mn with Fe, Co, Ni, Ca, and K are explored to confirm the unique advantages of transition metal ions. With an increase in Mn content in NaV8O20, (Na0.33,Mn0.65)V8O20 ·nH2O can deliver a reversible capacity of 150 mA h g-1 and a capacity retention of 99% after 1000 cycles, which may open new opportunities for the development of high-performance aqueous ZIBs.