Adjusting Zn2+ diffusion kinetics and storage capability of MnOOH nanofibers for high-performance cathode of aqueous zinc-ion batteries

MnOOH is regarded as a product of manganese-based materials after H+ insertion. There is rare study on the Zn2+/H+ storage capability of MnOOH. Herein, MnOOH nanofibers are prepared through a one-step hydrothermal method and developed as a promising cathode. The introduction of S doping changes the crystal structure of MnOOH and is conducive to its electronic/ionic transport and structural stability, proven by density functional theory calculations and various characterizations. The reduced Zn2+ diffusion barrier of S-doped MnOOH leads to its increased Zn2+ storage capability in the test of rate capability, especially at large current density. The Zn2+/H+ insertion-type mechanism of MnOOH is revealed by ex situ XRD, Raman, XPS, and SEM tests. Therefore, this optimized material delivers a high reversible capacity of 178 mAh g−1 at 0.1 A g−1, a good rate capability of 50 mAh g−1 at 3.0 A g−1, and a long cyclic life with 108 mAh g−1 at 0.5 A g−1 over 500 cycles. Moreover, the electrode still shows satisfactory rate capability and cyclic life even at the high mass loadings of 10 and 15 mg cm−2. This work proves the Zn2+/H+ storage capability of MnOOH and its potential as a high-performance cathode in aqueous zinc ion battery.