Tuning the distribution of zinc ions by manganese dioxide ion sieve to realize the uniform deposition of zinc ions on Zn metal anode of aqueous zinc-ion batteries

Abstract

Zinc (Zn) metal, as a promising anode for aqueous zinc-ion batteries (AZIBs), has attracted much attention owing to its reasonable redox potential and fabulous theoretical capacity. Notwithstanding, Zn dendrites and side reactions generated during charging/discharging seriously inhibit the reversibility of Zn anode of AZIBs. Herein, ultra-long manganese dioxide (MnO2) nanowires with low cost and easy synthesis have been designed as a high-efficiency zinc ion shunt to achieve uniform Zn deposition. The Zn coated with MnO2 protection layer possesses good water wettability, high ionic conductivity (1.3 mS cm−1) and low activation energy (38.2 kJ mol−1). As a result, the Zn@MnO2||Zn@MnO2 symmetric cell exhibits an ultra-long lifespan over 3800 h at 0.5 mA cm−2/0.25 mAh cm−2; for the Zn@MnO2||Zn@MnO2 symmetric cell, the accumulative discharge capacity surpasses 1600 mAh cm−2 and the depth of discharge (DOD) is 34.2% at the harsh conditions of 20 mA cm−2/20 mAh cm−2; and the average coulombic efficiency (CE) of the Zn//Cu@MnO2 asymmetric cell achieves 99.6%. In addition, the Zn@MnO2//NVO full cell possesses an excellent reversible discharge capacity of 176.3 mAh g−1 after 1000 cycles at 2 A g−1. This investigation provides a useful reference for designing high-efficiency zinc ion shunt to realize highly reversible Zn anode for AZIBs.