Recent advancements and next of aqueous rechargeable lithium-ion batteries

Aqueous rechargeable lithium-ion batteries (ARLBs) have attracted widespread attention due to the inherent merits of low cost, high safety, and environmental friendliness in comparison to their nonaqueous counterparts. However, the limited electrochemical stability window (ESW) of aqueous electrolytes near 1.23 V greatly restricts the selection of electrode materials and improvement of energy density of ARLBs. In the early stage, most works primarily focused on the modification of electrode materials with operating voltages in the narrow ESW range to enhance the cyclability. After the "water-in-salt" electrolyte came out, various approaches have been devised to continually widen the ESW of aqueous electrolytes and increase the energy density of ARLBs. Herein, we overview the historical development and recent advancements of ARLBs, focusing on the aspects of the electrode materials (modification strategies of cathode and anode) and the novel electrolytes (e.g., water-in-salt electrolytes, water-in-bisalt electrolytes, hydrate-melt electrolytes, hybrid aqueous/non-aqueous electrolytes, gel electrolytes). Finally, the existing key issues and future prospects are also presented for the next-generation ARLBs.