Polyaniline-intercalated FeOCL cathode material for chloride-ion batteries

Iron oxychloride is regarded as a promising cathode material for chloride-ion batteries, owing to its high theoretical capacity and abundant elemental resources. Its cycling stability, however, is limited by the intrinsic low conductivity and large volume change during cycling. Herein, the polyaniline-intercalated iron oxychloride, in which the interlayer spacing along the b-axis direction is greatly expanded from 0.79 to 1.4 nm, is developed as a cathode material for chloride-ion batteries. Benefiting from the uniform expanded laminated structure and high structural integrity, the fully polyaniline-intercalated iron oxychloride cathode delivers a short activation process, significantly improved charge transfer, and superior cycling stability. For example, a high reversible capacity of 120 mAhg^–1, owing to the redox reaction based on chloride ion transfer, is achieved after 50 cycles, showing good capacity retention of 82%. In contrast, the pure iron oxychloride cathode suffers from severe capacity decay and only 61 mAhg^–1 (42% capacity retention) is kept. This work demonstrates a new strategy for designing high-performance layered electrodes of chloride ion batteries.