Chloride-ion batteries (CIBs) have been regarded as a promising alternative battery technology to lithium-ion batteries because of their abundant resources, high theoretical volumetric energy density, and high safety. However, the research on chloride-ion batteries is still in its infancy. Exploring appropriate cathode materials with desirable electrochemical performance is in high demand for CIBs. Herein, the FeOCl nanocrystal embedded in a mesocellular carbon foam (MCF) has been prepared and developed as a high-performance cathode material for CIBs. The MCF with uniform and large mesocells (15.7-31.2 nm) interconnected through uniform windows (15.2-21.5 nm) can provide high-speed pathways for electron and chloride-ion transport and accommodate the strain caused by the volume change of FeOCl during cycling. As a result, the optimized FeOCl@MCF cathode exhibits the highest discharge capacity of 235 mAh g-1 (94% of the theoretical capacity) among those of the previously reported metal (oxy)chloride cathodes for CIBs. A reversible capacity of 140 mAh g-1 after 100 cycles is retained. In contrast, only 18 mAh g-1 was kept for the FeOCl cathode.
Keywords: chloride-ion batteries; electrochemistry; iron oxychloride; mesocellular carbon foam; nanoconfinement.