Fluorinated saccharide-derived hard carbon as a cathode material of lithium primary batteries: effect of the polymerization degree of the starting saccharide

Abstract

Fluorinated hard carbon materials have been considered to be a good candidate of cathode materials of Li/CF_x batteries. However, the effect of the precursor structure of the hard carbon on the structure and electrochemical performance of fluorinated carbon cathode materials has yet to be fully studied. In this paper, a series of fluorinated hard carbon (FHC) materials are prepared by gas phase fluorination using saccharides with different degrees of polymerization as a carbon source, and their structure and electrochemical properties are studied. The experimental results show that the specific surface area, pore structure, and defect degree of hard carbon (HC) are enhanced as the polymerization degree (i.e. molecular weight) of the starting saccharide increases. At the same time, the F/C ratio increases after fluorination at the same temperature, and the contents of electrochemically inactive –CF₂ and –CF₃ groups also become higher. At the fluorination temperature of 500 °C, the obtained fluorinated glucose pyrolytic carbon shows good electrochemical properties, with a specific capacity of 876 mA h g⁻¹, an energy density of 1872 W kg⁻¹, and a power density of 3740 W kg⁻¹. This study provides valuable insights and references for selecting suitable hard carbon precursors to develop high-performance fluorinated carbon cathode materials.