One-dimensional PPy@CNT based on reversible anions doping/dedoping as a novel high-performance cathode for potassium based double ion batteries

Recently, potassium ion batteries (PIBs) have emerged as promising substitutes to lithium-ion batteries (LIBs) for large-scale energy storages owing to the abundance of potassium. However, the large K+ causes phase transition and structural deterioration for traditional inorganic cathodes during K+ insertion/extraction. Compared with traditional inorganic cathodes, conductive polymers are particularly promising because their structural diversity and great tensile strength. Herein, the one-dimensional polypyrrole@carbon nanotube (1D PPy@CNT) was prepared via one-step in situ oxidative polymerization and investigated as a cathode for potassium based double ion batteries. The nano PPy layer is uniformly coated on the surface of CNT framework, in which CNT can facilitate the ion transport and electron transfer, and nano PPy layer can enrich active sites and ion storage. As expected, the 1D PPy@CNT delivers a high reversible capacity of 148 mAh g(-1) with a capacity retention rate of 75.5% up to 200 cycles. The storage mechanism and reaction kinetics of 1D PPy@CNT are well explored by a combination of ex situ Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and electrochemical characterizations. The results of measurements suggest that the storage mechanism of PPy@CNT is based on reversible doping/dedoping of anions (PF6-). The present work indicates the potential of PPy as a promising high-performance cathode for potassium based double ion batteries. (C) 2021 Elsevier Ltd. All rights reserved.