Controllable solvent treatment of fluorinated graphite for high power density and low cathode swelling lithium primary batteries

Lithium/carbon fluorides batteries own a high theoretical energy density of 2180 Wh kg−1 and exceptional shelf life, but poor electrode kinetics, low electronic conductivity of cathode, and cathode swelling during discharge. In this work, fluorinated graphite is modified by a controllable solvent treatment using N-methyl-2-pyrrolidone at medium temperature (50 ∼ 90 °C). The modified fluorinated graphite is doped with nitrogen atoms and owns increased interlayer spacing and electrochemical active semi-ionic CF bonds, providing a higher conductivity and facilitating the diffusion of Li+ or solvent Li+. The maximum power density of the modified fluorinated graphite is 40.23 kW kg−1 at 25C. To elucidate the cathode swelling of the fluorinated graphite, in-situ confocal optical microscope and in-situ X-ray diffraction are conducted for the first time. It is found that the formation and accumulation of crystalline LiF during discharge, as well as the interlayer spacing of fluorinated graphite, are related to the cathode swelling in liquid electrolyte.