Fluorinated microporous carbon spheres for Li/CFx batteries with high volumetric energy density

Abstract

Carbon fluorides (CFx) have the highest theoretical energy density among current cathode materials for lithium primary battery. Although fluorinated graphite (FG) has been successfully commercialized, its energy density is difficult to meet the continuously increasing demand. In this study, porous carbon spheres are prepared as starting materials to obtain a new type of CFx compound with improved electrochemical performance. The fluorinated microporous carbon spheres (FMCSs) with a high fluorinated degree achieve a comparable specific capacity as that of the commercial FG. The spherical morphology and hierarchically porous structure prompt the diffusion of Li+ and the reaction with fluorinated active sites. The FMCSs fluorinated at 250 °C deliver a specific capacity of 955 mAh g−1 and a maximum energy density of 2428 Wh kg−1, and could operate stably at discharge rate as high as 10C. Unlike nanostructured CFx, the desirable true density of FMCSs enable their practical applications without sacrificing the volumetric energy density. Therefore, the assembled pouch cell using FMCSs as the cathode material exhibits superior electrochemical performance. In particular, the alleviated volume expansion and heat release further promoted the applicability of FMCSs and strengthen their capability as a favorable alternative to commercial FG.