Multidimensional encapsulation geometry boosting bismuth selenide anode material with fast kinetics for superior potassium-ion storage

Conversion-alloying anode materials exhibit ultra-high theoretical specific capacity for potassium-ion batteries (PIBs) based on multi-electron transfer reaction. However, large volume variation and sluggish electrochemical kinetics have become key issues limiting its cyclability and rate capability. Herein, Bi₂Se₃ micro-flowers intertwined with one-dimensional carbon nanotube, anchored on two-dimensional reduced graphene oxide and encapsulated by three-dimensional N-doped C (Bi₂Se₃@rGO@NC/CNT) are constructed as anode materials for PIBs. The multidimensional hierarchical confinement effect boosts Bi₂Se₃ to exhibit fast electron/K-ion transport kinetics and great K-ion adsorption ability, as well as superior structure stability with the reduced lattice stress, where the stable existence of C-Se bond and Bi-O-C bonds plays an important role in maintaining interfacial stability of composite. It is illustrated that K-ion insertion into and extraction from Bi₂Se₃ via conversion-alloying dual-mechanism using Bi as the redox center based on 12-electron transfer per formular. Therefore, Bi₂Se₃@rGO@NC/CNT architecture contributes high initial specific capacity, excellent rate capability and cycling stability with ultra-long lifetime over 1000 cycles and low-capacity decay rate of 0.068% per cycle. This work lays a theoretical and experimental basis for the construction of high-performance conversion-alloying anode for PIBs.