Effective Solution toward the Issues of Zn-Based Anodes for Advanced Alkaline Ni-Zn Batteries.

Abstract

Alkaline nickel-zinc (Ni-Zn) batteries, as traditional rechargeable aqueous batteries, possess an obvious advantage in terms of energy density, but their development has been hindered by the anode-concerned problems, Zn dendrites, self-corrosion, passivation, deformation, and hydrogen evolution reaction (HER). Herein, to solve these problems, a dual protective strategy is proposed toward the anode using ZnO as an initial active material, including a C coating on ZnO (ZnO@C) and a thin poly(vinyl alcohol) (PVA) layer coating on the electrode (ZnO@C-PVA). In a three-electrode configuration, the reversible capacity can reach 600 mAh g-1 for the ZnO@C-PVA. Using excessive commercial Ni(OH)2 as the cathode, the alkaline Ni-Zn cells exhibit good electrochemical performance: Discharge capacity can be as high as 640-650 mAh g-1 at 4 A g-1 with a Coulomb efficiency (CE) as high as 97-99% after activity, suggesting low self-corrosion and HER. Capacity retention is 97% after 1200 cycles, indicating rather good durability. The discharge capacity is even slightly increased with the increase of charge/discharge current density (≤8 A g-1), implying good rate performance. Additionally, the discharge voltage can reach 1.8 V (midpoint value) at various current densities, reflecting the fast reaction kinetics of the anode. Most importantly, no Zn dendrites and passivation are observed after long-term cycling. The strategy proposed here can solve the anode-concerned problems effectively, exhibiting a high application prospect.