Magnesium batteries are attracting growing interest as next-generation energy storage technology due to their high safety, cost-effectiveness, and resource abundance. However, their development remains limited by sluggish Mg²⁺ transport kinetics at the electrode/electrolyte interface. Herein, we propose an electrolyte design strategy that modulates the Mg²⁺ solvation structure by introducing tetrahydrofuran (THF) as a co-solvent into a borate-based electrolyte, Mg[B(hfip)₄] (MBF) in dimethoxyethane (DME). THF, selected from a series of linear and cyclic ethers, has a comparable dielectric constant and donor number to DME, but its cyclic structure introduces steric hindrance that induces competitive coordination with Mg²⁺. This competition weakens Mg²⁺ − solvent interactions, yielding a more labile solvation structure and enhanced desolvation kinetics. As a result, Mg‖Mg cells employing the optimized MBF/1D1T electrolyte (DME: THF = 1:1, v:v) exhibit a significantly reduced Mg plating/stripping overpotential of 120 mV at 10 mA cm⁻², compared with 316 mV at 8 mA cm⁻² with MBF/DME, along with exceptional cycling stability exceeding 1200 h. Furthermore, representative sulfide cathodes such as CuS and VS₄ demonstrate faster activation and improved high-rate performance in the presence of MBF/1D1T.

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.