PEDOT-intercalated NH₄V₃O₈ nanobelts as high-performance cathode materials for potassium ion batteries

Potassium ion batteries (PIBs) have great potential to replace lithium ion batteries (LIBs) for large-scale energy storage applications because of the low cost and earth abundance of potassium resources. However, it is critically challenging to exploit an appropriate cathode material to accommodate the large size of K⁺. Herein, a conducting polymer (PEDOT) intercalation method is utilized to tailor the interlayer spacing of NH₄V₃O₈ nanobelts from 7.8 Å to 10.8 Å, and afford rich oxygen vacancies inside the vanadate, thus enhancing its electronic conductivity and accelerating the K⁺ insertion/extraction kinetics. Benefiting from these features, PEDOT-intercalated NH₄V₃O₈ (PNVO) nanobelts deliver an improved capacity of 87 mA h g^-1 at 20 mA g^-1, high rate capability of 51 mA h g^-1 at 500 mA g^-1, and a stable cycle life (capacity retention of 92.5 % after 100 cycles at 50 mA g^-1). Even cycled at 200 mA g^-1, PNVO nanobelts feature a long cycle life over 300 cycles with a capacity retention of 71.7 %. This work is of great significance for exploitation of PIBs cathode with improved electrochemical performance through pre-intercalation and defect engineering.