Researchers developed a halide-rich electrolyte that enables reversible high-valent chalcogen redox reactions in lithium batteries, according to a peer-reviewed study published in Nature Communications. The method transitions elemental selenium positive electrodes from a conventional two-electron reduction pathway into a three-electron conversion mechanism.
Elemental chalcogen chemistry in lithium batteries has historically faced limitations below 2.5 volts due to the instability of oxidized species during two-electron conversion. To bypass that barrier, the research team synthesized an electrolyte containing soluble organic halide salts paired with asymmetric cations. The formulation delivers active chloride or bromide anions into the system to stabilize oxidized intermediates and establish a redox-amphoteric conversion pathway.
During electrochemical testing, the shift to a three-electron reaction produced a voltage plateau at approximately 2.6 volts, marking the transition from elemental selenium to positive selenium ions. A lithium-selenium test cell utilizing the electrolyte recorded a reversible discharge capacity of 980 milliampere-hours per gram and a specific energy of 2003 watt-hours per kilogram of selenium. The cell sustained stable cycling across 200 cycles at a current rate of 400 milliamperes per gram.
The study demonstrated that the halide electrolyte design also activates high-valent conversion in sulfur and selenium sulfide cathode materials. The research team included scientists from City University of Hong Kong, Chulalongkorn University in Bangkok, and the Shenzhen Research Institute of City University of Hong Kong, with primary funding provided by the Natural Science Foundation of China and the Hong Kong Research Grants Council.
