Highly Reversible Zinc Metal Anode for Aqueous Batteries
Fei Wang, Oleg Borodin, Tao Gao, Xiulin Fan, Wei Sun, Fudong Han, Antonio Faraone, Joseph A. Dura, Kang Xu, Chunsheng Wang
Metallic zinc (Zn) has been regarded as an ideal anode material for aqueous batteries, because of its high theoretical capacity (820 mAh/g), low electrochemical potential (-0.762 V vs. SHE), high abundance, low toxicity and intrinsic safety. There has been a recent resurgence in Zn battery chemistry research due to increased safety concern on Li-ion batteries. However, Zn chemistry persistently suffers from severe irreversibility issues, caused by low coulombic efficiency (SE) of its plating/stripping in alkaline electrolytes, the growth of dendrite during cycling, and sustained water consumption caused by side reactions. Large excessive zinc has to be used to maintain the cucling stability, resulting in substantial under-utilization of the zince theoretical capacity. Here we report that the Zn-version of "water-in-salt" electrolyte (Zn-WiSE), being neutral in pH and capable of retaining water in open atmosphere, promotes dendrite-free plating/stripping of Zn at nearly 100% CE. Such merits render unprecedented reversibility to Zn chemistries with either LiMn2O4 or O2 cathodes. The former delivers 180 Wh/Kg and retained 80% of capacity for over 4000 cycles, while the latter delivers 200 Wh/Kg (1000Wh/Kg based on the cathode) for over 200 cycles.