Tellurium-doped MoS2/carbon composite nanotubes for potassium-ion capacitors

Potassium-ion capacitors (PICs) combine the benefits of high energy density and excellent power density at a lower cost than lithium storage technology. However, developing high-rate and stable anode materials that are compatible with capacitor-type counterparts remains a formidable challenge. In this study, tellurium-doped MoS2/carbon composite nanotubes (Te-MoS2/C NTs), featuring a one-dimensional hollow structure decorated with interlayer-extended few-layer nanosheets, were designed as anode materials for potassium storage. The Te-MoS2/C NTs achieve a notable average reversible capacity of 417.8 mA h g−1 at 0.05 A g−1 and 215.0 mA h g−1 at 5.0 A g−1. Additionally, it maintains a high capacity retention rate of 95.6% after 300 cycles at 2.0 A g−1. Moreover, density functional theory calculations validate the enhanced K+ adsorption and diffusion, attributed to the Te doping and interlayer expansion of MoS2. The PICs based on Te-MoS2/C NTs also achieves an energy density of 113.6 W h g−1 and a power density of 12.1 kW kg−1, alongside cycling stability.