Multi‐layered fluorinated graphene cathode materials for lithium and sodium primary batteries

Abstract

Abstract Fluorinated graphene has a promising application prospect in lithium primary batteries (LPBs) and sodium primary batteries (SPBs). Herein, five fluorinated graphene materials with different fluorine contents (FG‐ x ) are prepared by a large‐scale gas fluorination process. It is found that the structural characteristics of FG‐ x strongly depend on the fluorination temperature: the fluorine content (i.e., F/C ratio) gradually increases with the fluorination temperature rising, resulting in the enlargement of interlayer spacing and the increase of average bonding strength between C and F. FG‐0.75 sample with the intermediate degree of fluorination achieves the maximum energy densities in LPBs (2239.8 Wh·kg −1 ) and SPBs (1939.2 Wh·kg −1 ). The interlayer distance is critical to the rate capability of FG‐ x , and FG‐0.95 with the largest lattice spacing exhibits the best rate performance in both Li/CF x and Na/CF x batteries. The electrochemical reaction mechanism and the structural evolution of FG material revealed by ex situ X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD) characterization, and in situ Raman spectra further confirm the effect of interlayer distance.