Discharge Mechanism of Fluorinated Ketjen Black Cathode Material

Abstract

Fluorinated carbon is a prospective cathode material for lithium (Li) primary batteries, which are widely used as power sources for military applications, such as individual combat, spacecraft, and deep-sea detection. It offers high gram-specific capacity but is hindered by its low intrinsic conductivity and large volume expansion. However, fluorinated Ketjen black (FKB), with enhanced conductivity and less volume expansion compared with other fluorinated analogs, has been the subject of extensive attention, with its discharge mechanism being unclear. Herein, the structural evolution and compositional changes of FKB at various depths of discharge are revealed through characterization and analysis: The three-dimensional (3D), chain-like aggregate structure of FKB has a high void ratio, which can provide a storage space for LiF formation, thereby inhibiting the volume deformation during discharge. The discharge reaction model is a synergistic mechanism of a surface uniform reaction and local structural reorganization. The surface and defect sites preferentially react with Li⁺ and the C–F bonds in the 3D, chain-like structure selectively break to form LiF. We anticipate that our study paves the way for implementing better Li/fluorinated carbon (Li/CF_x) batteries.

Keywords

Fluorinated Ketjen black / Intrinsic conductivity / Suppress volume expansion / Lithium/fluorinated carbon batteries

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The Author(s) under exclusive licence to Tianjin University