Amorphous Se species anchored into enclosed carbon skeleton bridged by chemical bonding toward advanced K-Se batteries

Abstract

Potassium-selenium (K-Se) batteries have attracted significant attention as one of the most promising alternatives of lithium-ion storage systems owing to high energy density and low cost. In the design of Se-based cathode materials, however, the low utilization rate of active Se and the rapid dissolution of polyselenides seriously weaken the capacity and cycle stability. Therefore, how to make full use of Se species without loss during the charge and discharge process is the key to design high-performance Se-based cathode. In this paper, a 3D “water cube”-like Se/C hybrid (denoted as Se−O−PCS) is constructed with the assistance of Na2CO3 templates. Thanks to the abundant carbonate groups (CO32−) originated from the Na2CO3 templates, the molten Se species are firmly anchored into the pore of carbon skeleton by strong C−O−Se bonding. Thus, this unique Se−O−PCS model not only improves the utilization of active Se species, but also can reduce the contact with the electrolyte to inhibit the shuttle effect of polyselenides. Moreover, flexible carbon skeleton gives Se-O-PCS hybrid a good electrical conductivity and excellent structural robustness. Consequently, the resultant Se−O−PCS hybrid is endowed with an obviously enhanced K-ions storage property.