Hierarchically Porous Carbon from Lychee Seed as Cathode Host for Fast-Charging and High Area Capacity Li–Se Batteries

Selenium cathodes are expected to become next-generation energy storage materials due to their high electronic conductivity and volumetric capacity. However, their commercial applications are hindered by polyselenides dissolution and low Se utilization. Herein, a biomass compound, namely lychee seed, is used as a sustainable precursor to design hierarchically porous carbon by a single-step carbonization activation method. With a unique hierarchical porous structure, the lychee seed–derived activated carbon (LSDAC) used to encapsulate selenium delivers a reversible capacity of 446 mA h g⁻¹ at 2 C and 291 mA h g⁻¹ at 5 C after 1000 cycles. The Se/LSDAC electrodes show the most favorable fast-charging and good cycling behavior compared to the previously reported biomass-based carbon materials. By increasing the Se area loading to 9.5 mg cm⁻², the Se/LSDAC cathode maintains an areal capacity of 3.7 mA h cm⁻² (3.2 mA cm⁻² areal current density) after 80 cycles. High Se loading and economical and fast-charging cathode designs in Li–Se batteries are inspired.