Hierarchical bismuth composite for fast lithium storage: Carbon dots tuned interfacial interaction

Abstract

• Carbon dots (CDs) are utilized as “structure-directing agent” to tailor Bi 2 Se 3 /CDs composites with highly interconnected 3D architecture. • CDs-induced Bi-O-C bond is proved to effectively regulate the interfacial electronic structure. • The lithium storage mechanism of Bi 2 Se 3 /CDs anode is revealed by in-situ XRD. • Bi 2 Se 3 /CDs anode delivers fast-charging capability and durable cycling life. CDs are utilized as crucial structure-directing agents to elaborately design 3D cross-linked rod-like structured Bi 2 Se 3 /CDs composites. Computational simulations combined with experiments demonstrate that such robust 3D framework and the existence of interface Bi-O-C bond can simultaneously enhance the intrinsic sluggish kinetics and structural stability, endowing Bi 2 Se 3 /CDs anode with fast-charging capability and durable cycling life. Advanced electrode materials for fast-charging lithium-ion batteries are of great significance to next-generation energy-storage systems. Herein, three-dimensional (3D) hierarchical rod-structured Bi 2 Se 3 /carbon dots (Bi 2 Se 3 /CDs) composite is elaborately designed for fast-kinetics lithium storage. It is proposed that CDs-induced self-assembly growth and site-selective ion-exchange transform nanosheets into cross-linked architecture. Such robust 3D framework provides efficient channels for electron/ion transport and sufficient inner space for volume variation as confirmed by theoretical prediction. Notably, the existence of interface Bi-O-C bond would effectively enhance its inherent bulk electronic conductivity and accelerate ionic transportation by narrowing the bandgap and reducing the Li + migration energy barriers. Consequently, intrinsic sluggish kinetics and structural stability are simultaneously improved, endowing Bi 2 Se 3 /CDs composite electrode fast charging/discharging capability of 165 mAh g −1 at 20 A g −1 (corresponding to charge in ≈27 s) and excellent long-term durability with the capacity of 502 mAh g −1 over 950 cycles at 1 A g −1 . Moreover, the intercalation-conversion-alloying type lithium storage mechanism of Bi 2 Se 3 /CDs is revealed by in-situ XRD. This work provides a train of thoughts for other CDs-tailored composites with tunable morphology and structure.