Halogen Storage Electrode Materials for Rechargeable Batteries

The ever-increasing demand for rechargeable batteries with high energy density, abundant resources, and high safety has pushed the development of various battery technologies based on cation, anion, or dual-ion transfer. The use of halogen storage electrode materials has led to new concept battery systems such as halide-ion batteries (HIB) and dual-ion batteries (DIB). This review highlights the recent progress on these electrode materials, including metal (oxy)halides, layered double hydroxides, MXenes, graphite-based materials, and organic materials with carbon or nitrogen redox centers. The reversible electrochemical halogen storage of halide ions (e.g., F⁻, Cl⁻, and Br⁻), dual halogen (e.g., Br_mCl_n and [ICl₂]⁻), or binary halide anions (e.g., PF₆⁻, AlCl₄⁻, [ZnCl_x]^2−x, and [MgCl_x]^2−x) in the electrodes is covered. The challenges and mechanisms of halogen storage in various electrode materials in HIBs and DIBs are summarized and analyzed, providing insights into the development of high-performance halogen storage electrode materials for rechargeable batteries.