Ultrasmall Carbon Dot-Modified Bismuth Selenide Nanosheets as an Advanced Anode toward Enhanced Lithium Storage

Bismuth chalcogenides have gained widespread interest as conversion-alloying-type anode materials for lithium-ion batteries due to their large interlayer space, multielectron reactions, etc. These merits can endow bismuth chalcogenides with a Li + -storage capacity that is higher than that of the commercial graphite anode. Nevertheless, their volume variation upon cycling can destroy the structural integrity, resulting in irreversible capacity damping. Herein, the sheet-like composite (Bi 2 Se 3 –CDs), with Bi 2 Se 3 nanosheets uniformly modified with ultrasmall carbon dots (CDs), was successfully designed via a facile one-step solvothermal process. Ultrasmall CDs (∼3.7 nm) efficiently increase the electrical conductivity and surface-specific area, thereby intensifying the lithium-ion/electron transport kinetics of the Bi 2 Se 3 electrode. Additionally, the formation of the covalent bond (C–O–Bi) between Bi 2 Se 3 and CDs further accelerates charge transfer and guarantees structural integrity upon cycling. Consequently, the obtained Bi 2 Se 3 –CDs composite anode delivers comprehensive Li + -storage properties, including a relatively high initial Coulombic efficiency (76.2%), high reversible capacity (586 mAh g –1 at 100 mA g –1 after 50 cycles), and decent prolonged cycling stability (93.1% capacity retention after 300 cycles at 500 mA g –1 ). This study presents an efficient approach to constructing advanced bismuth-chalcogenide-based lithium-ion battery composite anodes.