Boosting cobalt ditelluride quantum-rods anode materials for excellent potassium-ion storage via hierarchical physicochemical encapsulation

The exploration of anode materials that can store large-sized K-ion to solve the poor kinetics and large volume expansion issues has become the key scientific bottlenecks hindering the development of potassium-ion batteries (PIBs). Herein, ultrafine CoTe2 quantum rods physiochemically encapsulated by graphene and nitrogen-doped carbon (CoTe2@rGO@NC) are regarded as anode electrodes for PIBs. Dual physicochemical confinement and quantum size effect not only enhance electrochemical kinetics but also restrain large lattice stress during repeated K-ion insertion/ extraction process. Superior electronic conductivity, K-ion adsorption, and diffusion ability can be acquired for CoTe2@rGO@NC, confirmed through first-principles calculations and kinetics study. K-ion insertion/extraction proceeds via a typical conversion mechanism relying on Co as the redox site, where the robust chemical bond of C-O-Co plays an important role in maintaining the electrode stability. Accordingly, CoTe2@rGO@NC contributes a high initial capacity of 237.6 mAh center dot g(-1) at 200 mA center dot g(-1), a long lifetime over 500 cycles with low-capacity decay of 0.10% per cycle. This research will lay the materials science foundation for the construction of quantum-rod electrodes.

Automated summary

In this study, ultrafine CoTe2 quantum rods encapsulated by graphene and nitrogen-doped carbon (CoTe2@rGO@NC) were used as anode materials for potassium-ion batteries. The dual physicochemical confinement and quantum size effect improved the electrochemical kinetics and reduced lattice stress during the insertion/extraction of potassium ions. CoTe2@rGO@NC showed excellent electronic conductivity, potassium ion adsorption, and diffusion ability, as confirmed by first-principles calculations and kinetics study. The conversion mechanism with Co as the redox site and the strong C-O-Co bond played important roles in maintaining the electrode stability. CoTe2@rGO@NC exhibited a high initial capacity of 237.6 mAh·g(-1) at 200 mA·g(-1) and a long cycle life with low-capacity decay of 0.10% per cycle. This research is significant for the development of quantum-rod electrodes.