In Situ Organoselenization for Ultrastable Li−Se Batteries

Overview

Lithium-selenium batteries exhibit high theoretical energy density but suffer from the shuttle effect, wherein soluble lithium polyselenides (Li2Sen) migrate between electrodes, causing irreversible capacity loss and performance degradation. This work presents an in situ organoselenization strategy that converts inorganic selenium into organic selenide forms, fundamentally preventing polyselenide formation and shuttle-induced failure mechanisms.

Methods and approach

The strategy employs 2-benzothiazole diethyldithiocarbamate (BTZA) as an organifying agent that undergoes nucleophilic reaction with lithium polyselenides, covalently grafting selenium atoms onto organic frameworks. During charging, this process generates organic diselenides while concurrently producing lithium benzothiazole sulfide (BTSLi). The BTSLi is oxidized to redox-active 2,2'-dibenzothiazole disulfide (BTDS) during the charge cycle, enabling capacity compensation for selenium incorporation losses. Electrochemical characterization included cycling tests at varying rates and temperatures, with evaluation of both coin cells and prototype pouch cells.

Key Findings

Lithium-selenium cells incorporating BTZA demonstrated 92.87% capacity retention after 1300 cycles at 2 C discharge rate. A prototype pouch cell with 0.6 Ah nominal capacity operated stably for 30 cycles at 0.1 C. The organoselenium products exhibited elevated discharge voltages and enhanced lithium-ion transport kinetics relative to conventional Li-Se systems. Superior electrochemical performance was achieved across high-rate discharge protocols.

Implications

The in situ organoselenization approach addresses a fundamental limitation in Li-Se battery chemistry by eliminating polyselenide shuttling through covalent incorporation of selenium into organic structures. The concurrent redox activity of sulfur-containing byproducts (BTDS formation) provides a compensatory capacity mechanism, mitigating the electrochemical cost of selenization. This strategy represents a departure from physical or chemical confinement approaches and establishes a pathway toward practical Li-Se battery deployment with cycle life and energy density metrics approaching commercial viability requirements.