FeOCl/polyaniline nanosheets as high-performance cathode for chloride ion battery

Chloride-ion batteries (CIBs) are potentially low-cost and safe alternatives to lithium-ion batteries. As a promising cathode material for CIBs, iron oxychloride shows high theoretical capacity and rich resources. However, the huge volumetric expansion and shrinkage issue for the phase transition result in pulverization of FeOCl particles and structural collapse of electrodes. Herein, FeOCl/polyaniline nanosheets with expanded laminated structure, polyaniline-coated, and high chlorine content have been developed as a high-performance cathode material for CIBs. It was found that the slow in situ intercalation polymerization of aniline into the layer of FeOCl nanosheets results in an irreversible loss of chlorine content, which is unfavorable for high discharge capacity. After being completely intercalated, adding an oxidizing agent is conducive to the polymerization of aniline and keeping the chlorine content stable. As a result, the optimized FeOCl/polyaniline cathode exhibits the highest discharge capacity of 187 mAh·g-1, and a capacity retention of 85.0% after 50 cycles. Polyaniline was maintained in the doped state and acted as a volume buffering matrix during the cycles.