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.