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

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.