Pt Nanorods-Decorated Macroporous Carbon Nanofiber Free-Standing Cathodes for High-Performance Li-O2 Battery

Abstract

Controlling the pore structure of cathodes has a strong influence on the performance of Li-O2 battery. In the present study, macroporous carbon nanofiber (MCNF) mats are successfully fabricated through an electrospinning and templating methods using cross-linked polystyrene particles. Additionally, Pt nanorods are grown on the surface of the MCNF (PtNR-MCNF) as catalysts for Li/O2 reactions. As-prepared PtNR-MCNF has interconnected macropores along the MCNF interior and abundant surface openings. Those macropores are also connected to larger pores between individual MCNF through the orifices on the MCNF surface, rendering a hierarchical porous structure. Owing to the highly porous structure, Li-O2 cells using the PtNR-MCNF cathodes achieved a specific capacity of approximately 7,000 mAh/gc and even more at a current density of 200 mA/gc. In particular, the Li-O2 cell using the PtNR-MCNF cathode exhibited higher electrochemical performance in terms of rate capability, energy efficiency, and cycle stability. This study demonstrates that the growth of PtNRs resulted in the formation of poorly crystalized Li2O2, which significantly reduced the overpotentials, both during the discharge and the charge. Additionally, it contributed to the considerably prolonged cycle life of the Li-O2 cell using the PtNR-MCNF (468 cycles) compared to the cell using the MCNF cathode (272 cycles) with a limiting capacity of 1,000 mAh/gc at a current density of 500 mA/gc.