Immobilizing and boosting lithium polyselenide conversion via a WSe2/WO2 heterostructure engineering strategy for lithium-selenium batteries

Crystalline selenium, characterized by higher electronic conductivity and volumetric capacity, represents one of the most promising cathode materials for next-generation battery technologies. However, the notorious lithium polyselenide shuttle effects yield formidable challenges, causing overcharge problems and unsatisfactory cycle performances. In this work, a nanosheet on nanorod WSe2/WO2 heterostructure was firstly developed as a proof of concept to immobilize and catalyze the soluble lithium polyselenides species. Through an in situ selenization process, the W5O14-ethylenediamine nanorod precursor was transformed to the WSe2/WO2 heterostructure, which was composed of long WO2 nanorods and WSe2 nanosheets. A combination of visual adsorption/permeation experiments, Li2Se electrochemical deposition tests, and theoretical calculations unraveled the strong chemical anchoring and efficient re-utilization toward soluble Li2Se6 and Li2Se4 species on the as-designed WSe2/WO2 heterostructure, which can originate from the bridge-shaped interfacial bonding structure. As anticipated, Li-Se batteries based on WSe2/WO2 heterostructure-modified separator exhibited dramatically improved overcharge property (overcharge capacity is 28.3 mA h g(-1), only 73.7% of that with pristine PP separator) and cycle performances (about 1.58 times higher than that with pristine PP separator).