Promoting the Normal- and Low-Temperature Performances of Natural Graphite by the F-Doping Derived from PVDF Modification

The inferior rate performance, cyclability, and low-temperature performance plague the wide application of natural graphite (NG). In this work, NG was modified with polyvinylidene fluoride (PVDF) by a simple hydrothermal route at 180 °C and subsequent sintering at 300 °C. The two-step treatment not only boosted the graphitization degree of NG but also strengthened the binding of PVDF with NG to yield uniform PVDF coating and F-doping adjacent to the NG surface. The modification contributes to enhancing the structural stability of NG, electron transfer, and Li-ion diffusion, facilitating the formation of a uniform and dense solid electrolyte interface film, reducing impedance, and alleviating polarization, thus endowing the PVDF-modified NG with elevated electrochemical performance, especially the marked enhancement in rate performance, cyclability, and low-temperature performance. This work opens up a simple avenue to promote the performance of NG, and the technique could be scaled up to industrially produce NG with high performance in a wide temperature range.