Rational construction of K0.5V2O5 nanobelts/CNTs flexible cathode for multi-functional potassium-ion batteries

Abstract

Potassium-ion battery (KIB) is one of the emerging electrochemical energy storage technologies due to the abundance, low cost, and low redox potential of K. One of the most promising cathodes of KIBs is a layered vanadium-based compound, but it often suffers from fast capacity decay during repeated cycling. Herein, a K_0.5V₂O₅/CNTs hybrid film composed of K_0.5V₂O₅ nanobelt and carbon nanotube (CNT) network was synthesized by an electrostatic self-assembly and vacuum filtration process, and further used as the cathode in KIBs. The K_0.5V₂O₅/CNTs cathode possessed a flexible and interconnected network structure, which not only offered fast kinetics for electron transfer and ion transportation, but also provided an elastic medium to buffer the large volume change of the K_0.5V₂O₅ nanobelts during cycling. As a cathode for KIBs, the K_0.5V₂O₅/CNTs electrode showed a reversible discharge capacity of ∼90 mA h g⁻¹ at 50 mA g⁻¹ and exhibited good cycling stability (88.8% capacity retention for 100 cycles at 50 mA g⁻¹, 82.2% capacity retention for 300 cycles at 500 mA g⁻¹) and excellent rate performance of ∼62 mA h g⁻¹ at 500 mA g⁻¹. K-Ion full battery testing further confirmed its good electrochemical performance by presenting a high reversible discharge capacity (68 mA h g⁻¹ at 50 mA g⁻¹) and long-term retention (>80% after 80 cycles). Interestingly, a cable-shaped KIB with the flexible K_0.5V₂O₅/CNTs film as the cathode electrode was assembled and showed its further application potential as a power source for wearable electronics.