The electrochemical performance of fluorinated ketjenblack as a cathode for lithium/fluorinated carbon batteries

Abstract

The inferior rate capacity of lithium/fluorinated carbon (Li/CF _<i>x</i> ) batteries limits their application in the field, requiring large discharge current and high power density. Herein, we report a novel type of fluorinated carbon with superior performance through gas-phase fluorination of ketjenblack. The investigation shows that the F/C ratio of the fluorinated ketjenblack (FKB) increases with the fluorination temperature, whereas the discharge voltage decreases due to the lowered content of semi-ionic C-F bonds. Accordingly, a suitable fluorination temperature of 520 °C was selected, under which the product exhibits the largest specific capacity of 924.6 mA h g^-1 with discharge potential exceeding 3.1 V (<i>vs.</i> Li/Li⁺) and the highest energy density of 2544 W h kg^-1 with power density of 27 493 W kg^-1. This energy density is higher than the theoretical energy density of commercial fluorinated graphite (2180 W h kg^-1). In addition, the sample delivers good rate capability demonstrated by a specific capacity retention ratio of 79.5% even at a current density of 20C. Therefore, the FKB material may have very promising practical applications in lithium primary batteries.