Flexible free-standing air electrode with bimodal pore architecture for long-cycling Li-O2 batteries

Li-O2 batteries have been proposed as next-generation energy-storage devices, but this technology is hindered by serious problems including parasitic reactions, degradation, and leakage of the electrolyte. Li-O2 batteries are also currently designed to have a rigid bulky structure, which cannot satisfy the flexibility demands of modern electronics. Herein, we report the significant enhancement of the electrochemical performance and flexibility of a Li-O2 battery by introducing a free-standing, binder-free carbon nanotube cathode with a bimodal pore architecture. This electrode structure imparted stability to active sites during the recovery of discharge products to the initial state, providing long-term cyclability of more than 100 cycles in a tetraethylene glycol dimethyl ether electrolyte system. The O2 transportation and conductivity were also improved, yielding an increased discharge capacity of 5500 mAh g−1 (nearly twice that of a non-porous cathode) and minimizing parasitic reactions. This novel bimodal-pore cathode exhibited an increased tri-phase boundary for the Li-O2 reactive zone in the interconnected CNT network. The small pore structures (∼50 nm) accommodated Li2O2, and the large pore structures (∼385 nm) enabled effective oxygen diffusion without clogging the pores. Moreover, Li+ and oxygen diffusion were facilitated by the two independent channels provided by the pore structures.

292