Potassium pre-intercalated manganese dioxide nanoflakes for high-performance aqueous zinc ion batteries

Manganese dioxide (MnO2) is promising cathode materials for aqueous rechargeable zinc ion batteries (ARZIBs) owing to their diverse polymorphy, high operating voltage and environmental benignity. However, the sluggish electrochemical kinetics and poor cycling stability are major issues to binder their practical applications. Herein, potassium pre-intercalated manganese dioxide (KMO) nanoflakes were fabricated via simple hydrothermal method. The KMO nanoflakes are assigned to be layered birnessite phase with layer spacing of 7.2 & ANGS; and the atomic ratio between K and Mn is around 1:3. As cathode for ARZIBs, the KMO electrode delivered specific capacity of 252 mAh g(-1) at current density of 0.1 A g(-1) and gained specific capacity of 288 mAh g(-1) after 100 cycles, being with the retention of 114%. The KMO cathode displayed outstanding cycling stability that under large current density of 2.0 A g(-1) it could retain 84.3% of initial capacity after 4000 cycles. By analyzing the electrochemical dynamics and phase evolution of KMO electrode during discharge/charge process, it was validated that the potassium pre-intercalation in MnO2 framework not only provides enlarged spacing for Zn2+/H+ ion transferring but also is served as strong support to stabilize the layer structure, resulting in high energy density and better cycling stability. Our work provides rational way for designing high-performance manganese-based cathode materials for ARZIBs. [Graphics] .