Layered Double Hydroxides for Low-Cost Zinc Batteries with High Safety

Description

Since its first appearance in the Leclanché cell in 1866, metallic zinc has been considered as an ideal electrode material for aqueous energy storage systems owing to its intrinsic high capacity, low redox potential, abundance in nature, low toxicity, and absolute safety. These advantageous features have resulted in a recent renaissance in the development of rechargeable zinc batteries (ZBs). However, exposing zinc metal to traditional alkaline electrolytes causes severe irreversible electrochemical processes in the zinc that result from insufficient coulombic efficiency of its stripping/plating, dendrite formation upon charging/discharging, irreversible production of by-products, and sustained water consumption. Thus, ZBs that use alkaline electrolytes exhibit poor cycle stability.In recent years, ZBs have successfully evolved into a new era through the use of neutral or mildly acidic electrolytes and MnO2 cathodes with tunnelled structures. These batteries have demonstrated greatly improved cycle stability and have retained the advantages of high specific capacity and safety. Despite the moderate cycle stability, MnO2 still suffers unignorable structural transformation when acting as host for zinc ion intercalation/deintercalation during cycling, and the resultant large volumetric change tends to lead to accumulative capacity fading. Besides, the low coulombic efficiency remains a problem, high charging and discharging rates are thus necessary to alleviate the influences of poor reversibility during electrochemical processes. However, MnO2 cathode cannot meet the requirement of high charge/discharge rates because of its sluggish intercalation/deintercalation kinetics, resulting in poor rate performance.New cathode materials have been developed for ZBs. Researchers have borrowed vanadium oxides and vanadates from other battery systems for use as cathodes to pair zinc anode, and great progresses have been achieved. Many ZBs based on these materials have exhibited much improved performances including increased specific capacity and better cycle stability. However, the zinc ion intercalation/deintercalation potentials for most vanadium oxides and vanadates are relatively low, which leads to low discharge plateaus that decrease their energy density. Moreover, Prussian blue analogues have also been investigated as novel cathodes. Despite possessing higher potentials, these materials suffer issues of low specific capacity and poor cycle stability that substantially limit their further applications.In this project, we propose to develop novel transition-metal-based layered double hydroxides (LDHs) as cathode for ZBs. LDH compounds with structures that are promising for ion accommodating, fast intercalation/deintercalation and stable cycling will be synthesized and optimized. Their working mechanism, structural evolution, and electrochemical dynamics will be in-depth investigated via in-situ X-ray diffraction, Raman spectroscopy and neutron-based techniques. Based on our preliminary results, we strongly believe that the proposed LDHs will work as high-performance cathodes that fills in the voids of efficient cathodes for ZBs.