A new Li2Mn3O7 cathode for aqueous Zn-Ion battery with high specific capacity and long cycle life based on the realization of the reversible Li+ and H+ co-extraction/insertion

摘要

Aqueous Zn-ion batteries (ZIBs) are expected to be used for practical energy storage and grid-scale applications because of their low-cost, high-safety and environmental friendliness. However, it is still a major challenge to achieve a suitable cathode for ZIBs with a high energy density and long cycle life. Herein, we reported a new cathode Li2Mn3O7 for aqueous ZIBs and have studied in detail the role of Li+ as electrolyte additives in further improving electrochemical performance. The Li+& nbsp;in the additive-contained electrolyte itself not only facilitates the reversible extraction/insertion of Li+ in Li2Mn3O7 but also effectively reduce the decomposition effect of Li2Mn3O7 caused by the charge process through the re-insertion of Li+ in subsequent discharge process and thus realizes the reversible deintercalation/intercalation of H+. Owing to the realization of the reversible Li+ and H+ co-extraction/insertion caused by the use of Li+ additive, the Li2Mn3O7 electrode exhibits a high reversible specific capacity of 242 mAh g-1 with nearly 100% coulombic efficiency at 200 mA g(+) current density. In particular, due to the enhanced capacitive contribution, Li(2)Mn(3)O(7 & nbsp;)electrode presented an impressive life span at high current density 2 A g(-1), and after 1000 cycles, a stable specific capacity greater than 100 mAh g(-1) can be maintained, which is significantly better than that of manganese oxide-based cathode materials in ZIBs. Furthermore, by In-situ X-ray diffraction (XRD) and ex-situ X-ray photoelectron spectroscopy (XPS), we discuss in detail the complex energy storage mechanism ofLi(2)Mn(3)O(7) as cathode material for ZIBs with electrolyte containing Li+ additive for the first time. Based on the high specific capacity and big current life span, aqueous ZIBs with Li2Mn3O7 & nbsp; exbibit a great potential for large scale electrical energy storage.

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