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[sbnd]O[sbnd]Co plays an important role in maintaining the electrode stability. Accordingly, CoTe₂@rGO@NC contributes a high initial capacity of 237.6 mAh·g⁻¹ at 200 mA·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.