B4C as a stable non-carbon-based oxygen electrode material for lithium-oxygen batteries

Lithium-oxygen (Li-O-2) batteries have extremely high theoretical specific capacities and energy densities when compared with Li-ion batteries. However, the instability of both electrolyte and carbon-based oxygen electrode related to the nucleophilic attack of reduced oxygen species during oxygen reduction reaction and the electrochemical oxidation during oxygen evolution reaction are recognized as the major challenges in this field. Here we report the application of boron carbide (B4C) as the non-carbon based oxygen electrode material for aprotic Li-O-2 batteries. B4C has high resistance to chemical attack, good conductivity, excellent catalytic activity and low density that are suitable for battery applications. The electrochemical activity and chemical stability of B4C are systematically investigated in an aprotic electrolyte. Li-O-2 cells using B4C-based air electrodes exhibit better cycling stability than those using carbon nanotube-and titanium carbide-based air electrodes in the electrolyte of 1 M lithium trifluoromethanesulfonate in tetraglyme. The performance degradation of B4C-based electrode is mainly due to the loss of active sites on B4C electrode during cycles as identified by the structure and composition characterizations. These results clearly demonstrate that B4C is a very promising alternative oxygen electrode material for aprotic Li-O-2 batteries. It can also be used as a standard electrode to investigate the stability of electrolytes.