Recent Advances in Li Anode for Aprotic Li-O2 Batteries

The aprotic Li-O-2 battery has attracted considerable interest in recent years because of its high theoretical specific energy that is far greater than that achievable with state-of-the-art Li-ion technologies. To date, most Li-O-2 studies, based on a cell configuration with a Li metal anode, aprotic Li+ electrolyte and porous O-2 cathode, have focused on O-2 reactions at the cathode. However, these reactions might be complicated by the use of Li metal anode. This is because both the electrolyte and O-2 (from cathode) can react with the Li metal and some parasitic products could cross over to the cathode and interfere with the O-2 reactions occurring therein. In addition, the possibility of dendrite formation on the Li anode, during its multiple plating/stripping cycles, raises serious safety concerns that impede the realization of practical Li-O-2 cells. Therefore, solutions to these issues are urgently needed to achieve a reversible and safety Li anode. This review summarizes recent advances in this field and strategies for achieving high performance Li anode for use in aprotic Li-O-2 batteries. Topics include alternative counter/reference electrodes, electrolytes and additives, composite protection layers and separators, and advanced experimental techniques for studying the Li anode vertical bar electrolyte interface. Future developments in relation to Li anode for aprotic Li-O-2 batteries are also discussed.