Carbon nanotube-stabilized Co9S8 dual-shell hollow spheres for high-performance K-ion storage

Abstract

In this work, carbon nanotube-coated dual-shell Co₉S₈ hollow spheres are studied as anode materials for K-ion batteries. The unique hollow structure and carbon nanotubes synergistically enhance the conductivity and resolve the critical drawbacks of Co₉S₈ electrodes, including large volume variation, structural instability and interfacial changes. Thus, the electrode delivers a stable reversible capacity of 320.5 mA h g⁻¹ at 0.1 A g⁻¹ after 200 cycles with a capacity retention of 91%. At 1.0 A g⁻¹, the capacity is 163.9 mA h g⁻¹ after 1000 cycles with a capacity retention of 73.6%. An investigation of the electrode reaction mechanism indicates that the surface capacity also contributes to the outstanding electrochemical performance.