Encapsulating selenium into mesoporous carbon for high-performance aqueous Cu-Se battery

As an appealing cathode material for rechargeable batteries, selenium (Se) attracts much attention benefitting from its outstanding electronic conductivity and high volumetric specific capacity. Whereas, Se cathode generally suffers from large volume expansion and polyselenides shuttling, which seriously hamper the progress of Se-based batteries. To overcome these challenges, a novel aqueous Cu-Se battery is designed by employing Se encapsulated in ordered mesoporous carbon (Se/CMK-3) as cathode. Via X-ray diffraction and X-ray photoelectron spectroscopy, the reaction mechanism of the designed battery is verified as a four-electron conversion of Se ↔ CuSe ↔ Cu5Se4 ↔ Cu2Se. Benefiting from the synergistic effects of four-electron conversion (Se ↔ Se2−, Cu2+↔Cu+) and robust mesoporous carbon host, the battery manifests high specific capacity (1009.5 mAh/g at 0.2 A/g) and favorable long-span cycling capability (93.7 % capacity retention after 400 cycles at 4.0 A/g). Therefore, this work provides a novel route for building high-performance aqueous Se-based batteries.