Conversion-Alloying Dual Mechanism Anode: Nitrogen-Doped Carbon-Coated Bi2Se3 Wrapped with Graphene for Superior Potassium-Ion Storage

Abstract The construction of an anode material with a conversion-alloying dual mechanism will facilitate the development of potassium-ion batteries (PIBs) with high-energy density. Here a Bi2Se3 nanosheets coated with nitrogen-doped carbon and wrapped with reduced graphene oxide (Bi2Se3@NC@rGO) is fabricated to boost K-ion storage. The Bi2Se3@NC@rGO composite with strong C–O–Bi bonding can provide superior electrode integrity and electrochemical kinetics by combining the synergistic effect of carbon encapsulation and graphene confinement. In situ X-ray diffraction and ex situ transmission electron microscopy analyses demonstrate that K-ion intercalation/deintercalation proceeds via both conversion and alloying/dealloying reactions based on 12-electron transfer per formula unit; the conversion product of K2Se can efficiently suppress the volume expansion during alloying/dealloying process to improve its stability. Hence, a high reversible capacity of 612.0 mAh•g−1 at 100 mA•g−1; a great rate capability with the capacity of 101.6 mAh•g−1 at 5 A•g−1, and an ultra-long cycling life of over 1000 cycles at 500 mA•g−1 is achieved for the Bi2Se3@NC@rGO. The K-ion full cell is also assembled using K2Ni[Fe(CN)6] as the cathode, thereby contributing a high-energy density of 162.9 Wh•kg−1 at 10 mA•g−1 and a great cyclability.