Recent progress of molybdenum-based materials in aqueous rechargeable batteries

Taking advantages of aqueous electrolytes such as high safety, ease of fabrication, and high ion conductivity, a series of aqueous batteries have been reported, including lithium-ion batteries, sodium-ion batteries, zinc-ion batteries, aluminum-ion batteries, and novel batteries such as ammonium batteries. They realize energy storage via the repeated (de)intercalation of charge carriers or conversion, which sets strict criteria for choosing proper electrode hosts. Molybdenum-based materials are very competitive candidates for aqueous battery assembly because of their specific layered/tunnel structure and low cost, but their development in this area remains at the infant stage. This review sums up the latest advances on the use of molybdenum-based materials as electrode materials for aqueous batteries. The main strategies for improving their electrochemical properties are summarized, including the introduction of oxygen/sulfur vacancy, interlayer spacing tuning, substrate coating, and electrolyte formulation. The working principles of these methods are compared and discussed in detail. In addition, the main opportunities, achievements, and challenges in this field are briefly commented. (C) 2020 The Author(s). Published by Elsevier Ltd.