New-concept Batteries Based on Aqueous Li(+)/Na(+) Mixed-ion Electrolytes

Rechargeable batteries made from low-cost and abundant materials operating in safe aqueous electrolytes are attractive for large-scale energy storage. Sodium-ion battery is considered as a potential alternative of current lithium-ion battery. As sodium-intercalation compounds suitable for aqueous batteries are limited, we adopt a novel concept of Li(+)/Na(+) mixed-ion electrolytes to create two batteries (LiMn(2)O(4)/Na(0.22)MnO(2) and Na(0.44)MnO(2)/TiP(2)O(7)), which relies on two electrochemical processes. One involves Li(+) insertion/extraction reaction, and the other mainly relates to Na(+) extraction/insertion reaction. Two batteries exhibit specific energy of 17 Wh kg(−1) and 25 Wh kg(−1) based on the total weight of active electrode materials, respectively. As well, aqueous LiMn(2)O(4)/Na(0.22)MnO(2) battery is capable of separating Li(+) and Na(+) due to its specific mechanism unlike the traditional “rocking-chair” lithium-ion batteries. Hence, the Li(+)/Na(+) mixed-ion batteries offer promising applications in energy storage and Li(+)/Na(+) separation.