Suppressing Zn dendrite growth by molecular layer deposition to enable long-life and deeply rechargeable aqueous Zn anodes

Abstract

Rechargeable zinc-ion batteries (ZIBs) in mild/neutral aqueous electrolytes are promising for large-scale energy storage applications due to their merits of high capacity, intrinsic high safety, low cost and environmental benignity. However, the overall performance of ZIBs has been severely hindered by the uneven electrostripping/plating of Zn on the anodes, which could cause Zn dendrite formation, enlarged overpotential (capacity decay) and even cell short-circuit (inferior cycling stability). Herein, alucone, an inorganic–organic hybrid coating, by the molecular layer deposition (MLD) technique, was developed to address the aforementioned problems and improve the reversibility of Zn anodes for ZIBs. As a result, a long-life and deeply rechargeable Zn anode was demonstrated. With the optimized coating thickness of 60 MLD cycles (∼12 nm), an over 11-fold enhancement in the running lifetime (780 vs. 70 h) and a reduced overpotential (84.3 vs. 110.3 mV) were achieved compared to bare Zn at a current density of 3 mA cm⁻². Besides, the rechargeability of the Zn anode at high current densities and deep stripping/plating levels was also improved by alucone coating. Furthermore, the alucone coated Zn has been verified in Zn/MnO₂ batteries and consequently, superior electrochemical performance with a high capacity retention of 83.3% after over 800 cycles at a current density of 1C was demonstrated. The detailed structure, morphology and surface chemistry evolution of Zn metal were comprehensively studied for interpreting the improved electrochemical performance. It is expected that this work may pave the way towards to rational design of high-performance aqueous ZIBs and shed light on the development of other metal anode-based battery systems.