Porous LiMn ₂O ₄ as cathode material with high power and excellent cycling for aqueous rechargeable lithium batteries

A porous LiMn ₂O ₄ consisting of nano grains was prepared by using polystyrene as template. It was studied as a cathode material for aqueous rechargeable lithium batteries (ARLBs) using 0.5 mol l ^-1 Li ₂SO ₄ aqueous solution as the electrolyte. Charge and discharge capacities at a current density of 10 A g ^-1 (about 90C) were 76% and 95% of the total capacity (118 mAh g ^-1), respectively. The power density can be up to 10000 W kg ^-1 and the cycling behavior is excellent. After 10000 cycles at 9C with 100% DOD (depth of discharge), the capacity retention of porous LiMn ₂O ₄ is 93%, which indicates that it can be used for a lifetime without maintenance. The main reasons for its excellent electrochemical performance are due to the nano grains, porous morphology and high crystalline structure. In addition, the acid-free aqueous electrolyte prevents Mn ²⁺ from dissolution. These excellent results suggest a great promise for the development of aqueous rechargeable lithium batteries (ARLBs) in practical application.