Design strategies of performance-enhanced Se cathodes for Li-Se batteries and beyond

Lithium-selenium (Li-Se) batteries are deemed as an emerging high energy density electrochemical energy storage system owing to their high specific capacity and volume capacity. Prior to their practicality, a series of critical challenges from the Se cathode side need to be overcome including low reactivity of bulk Se, shuttle effect of intermediates, sluggish redox kinetics of polyselenides, and volume change etc. In this review, recent progress on design strategies of functional Se cathodes are comprehensively summarized and discussed. Following the significance and key challenges, various efficient functionalized strategies for Se cathodes are presented, encompassing covalent bonding, nanostructure construction, heteroatom doping, component hybridization, and solid solution formation. Specially, the universality of these functional strategies are successfully extended into Na-Se batteries, K-Se batteries, and Mg-Se batteries. At last, a brief summary is made and some perspectives are offered with the goal of guiding future research advances and further exploration of these strategies.