Investigating K⁺ Storage Behavior of Highly Graphitized Carbon Fibers as Anodes for a Potassium-Ion Battery

Many problems of potassium-ion batteries (PIBs) are hidden under a low mass load of the active material. However, developing research based on areal capacity is challenging for PIBs, due to the lack of an anode capable of delivering a stable capacity of more than 1 mAh cm^-2. This work investigates the K⁺ storage behavior of highly graphitized carbon fibers (HG-CF), which exhibit automatic structural adjustments to mitigate voltage polarization. The created defects and residual K⁺ in the structure favor the reversible insertion/deinsertion of K⁺. HG-GF after structural adjustment realizes a capacity of 2 mAh (1.13 cm^-2) without K deposition and a stable cyclic stability (>500 h). In situ X-ray diffraction and in situ Raman spectra were used to detect defect formation and structural evolution during cycles. This work demonstrates the feasibility of HG-GF as an anode for PIBs and provides a suitable anode for further research of PIBs based on areal capacity.