Supercritical CO2-assisted synthesis of 3D porous SiOC/Se cathode for ultrahigh areal capacity and long cycle life Li–Se batteries

Abstract

The commercial application of lithium–selenium (Li–Se) batteries is hampered by low areal capacity, inferior cycling stability and low utilization of Se, in particular at a high Se loading. Here, a facile biotemplating method with the assistance of a supercritical CO₂ (SC–CO₂) technique has been developed to construct a unique 3D porous SiOC/Se cathode with a high Se loading for Li–Se batteries with high areal capacity and a long cycling life. An SiOC/Se cathode derived from rice husks achieved an extremely high initial areal capacity of 8.1 mA h cm⁻² at 0.1C at an Se loading of 8 mg cm⁻², which is the highest Se loading reported thus far. After 200 cycles, the reversible areal capacity remained at 4.1 mA h cm⁻² together with a capacity retention of 90% (vs. 4.8 mA h cm⁻² in the 2nd cycle). This excellent performance at a record-breaking Se loading in comparison with earlier Li–Se batteries is attributed to the unique 3D porous conductive network and Si–O–C units set in the porous carbon matrix, which provided continuous electron/ion pathways, enhanced structural stability and strong chemical adsorption for trapping Se and Li₂Se, as well as the uniform distribution of Se infiltrated via the SC–CO₂ strategy. This cathode with an ultrahigh Se loading is strongly expected to pave the way for the practical implementation of Li–Se batteries with a high energy density in large-scale energy storage systems.