Constructing carbon nanofiber/cobalt core/coating material for Li-O2 battery cathodes

Abstract

       In this study, we successfully design and synthesize the non-woven mats constructed from carbon nanofibers with cobalt attached on its surface (CNF/Co) by coaxial electrospinning (ES) for high-performance Li-O₂ battery cathode. The coaxial ES process involved a solution of polyacrylonitrile as core fluid and a blend of Co acetylacetonate and polyvinylpyrrolidone solution as sheath fluid. For CNF/Co cathode, Co (45 wt%) with nanosize (most of them were lower than 50 nm) is well distributed on the surface of CNF. Electrochemical tests of the CNF/Co as Li-O₂ cathode exhibited that the specific capacity of 4650 mAh/g_c compared with 3360 mAh/g of the CNF at 500 mA/g_c. The Co nanoparticles leads to the formation of Li₂O₂ with low crystalization rate, which reduces overpotential during the discharging and injecting steps. The energy efficiency of Li-O₂ batteries using CNF/Co cathodes is 20% higher than using CNF cathodes at whole capacity (1000 mAh/g_c) discharge/injection. It contributes to considerably prolonged cycle life of the LOB using the CNF/Co (> 80 cycles) in comparison to the cell using the CNF cathode (67 cycles) with limiting capacity of 1000 mAh/g_c at a current density of 500 mA/g_c.