Zinc ion storage abilities of Mo3WOx nano-ceramic under extreme-cold environments

Abstract

It is imperative to develop new electrode materials for aqueous multivalent metal ion batteries with electrochemistry abilities at extreme-low temperatures due to the possible extreme-cold operating conditions of batteries in the present or the future. Herein, as a proof-of-concept experiment, a new orthorhombic molybdenum-tungsten oxide (Mo3WOx) is synthesized by a wet-chemical method and tested as anode material for aqueous zinc ion batteries at extreme-cold temperatures (−40, −60 and −75 °C) for the first time. Two anti-freezing electrolytes are selected to examine the related half-cell performances, and 7.5 m ZnCl2 aqueous solution is more suitable for Mo3WOx half-cells than 2 m Zn(BF4)2 aqueous solution. At −40 °C, Mo3WOx exhibits reversible charge capacity of 104.1 mAh g−1 at 100 mA g−1 and the charge capacity can still maintain 82.3 mAh g−1 after 100 cycles; and under further test at 5000 mA g−1, Mo3WOx shows a high initial charge capacity of 42.5 mAh g−1 together with a capacity retention ratio of 81.6 % after 10,000 cycles. It is worth highlighting that the high capacities of Mo3WOx delivered at −40 °C are even comparable with the capacities of some “new-type” anode materials for aqueous zinc ion batteries exhibited at ambient temperature. At colder temperatures of −60 and −75 °C, the as-prepared compound still owns certain zinc ion storage abilities, especially high discharge/charge capacities of 48.9/48.7 mAh g−1 can be still achieved in the 100th cycle at −75 °C (100 mA g−1). Furthermore, a full-cell with operational capability at −40 °C is also built here, and it can exhibit discharge capacity of 66.1 mAh g−1 (coulombic efficiency of 99.7 %) in the 3rd cycle and discharge capacity of 48.2 mAh g−1 (coulombic efficiency of 99.7 %) in the 50th cycle.