Isolation of Hypervalent Group-16 Radicals and Their Application in Organic-Radical Batteries

Using a newly prepared tridentate ligand, we isolated hypervalent sulfur and selenium radicals for the first time and characterized their structures. X-ray crystallography, electron spin resonance spectroscopy, and density functional theory calculations revealed a three-coordinate hypervalent structure. Utilizing the reversible redox reactions between hypervalent radicals and the corresponding anions bearing Li⁺, we developed organic radical batteries with these compounds as cathode-active materials. Furthermore, an all-radical battery, with these compounds as the cathode and a silyl radical as the anode, was developed that exhibited a practical discharge potential of ∼1.8 V and stable cycle performance, demonstrating the potential of these materials for use in metal-free batteries that can replace conventional Li-ion batteries where Li is used in the metal form.