Synergistic effects of freestanding architecture and heteroatom-doping in carbon anode toward ultra-high areal capacity potassium-ion batteries

Potassium-ion batteries (PIBs) have garnered considerable interest for promising stationary energy storage devices. However, the current researches of carbon anode for PIBs still face the severe challenge of low areal capacity, unsatisfactory kinetics rate and low initial coulombic efficiency from the practical application perspective. To solve these issues, we design Fluorine-doped Typha orientalis fibre (FTOF) membrane by constructing integrated architecture and regulating electronic structure, and this FTOF membrane is used as freestanding carbon anode. This novel carbon anode not only retains integrated architecture with bamboo-like microfiber, but also presents abundant F-doped site and vacancy defects. As a result, the FTOF electrode delivers high areal capacity (1.12 mAh cm−2) with initial coulombic efficiency (62.5 %), stable cycling performance (0.41 mAh cm−2 after 500 cycles) and excellent rate performance (0.50 mAh cm−2 at 4 mA cm−2), overmatching most of the reported studies. Theoretical calculations on K adsorption affinities at various configurations illuminate the synergistic effects of F-doping and vacancy defects in improving K+ adsorption kinetics. Moreover, full cells deliver superior cycling performance with high capacity retention of 90.2 % after 1000 cycles. This work provides a rational electrode design strategy and theoretical guidance to achieve ultra-high areal capacity carbon anode for PIBs.