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

Abstract

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).