Highly crystalline graphite nanofibers as an anode for high-performance potassium-ion batteries

Abstract

Graphite is considered the most promising anode for low-cost potassium-ion batteries (PIBs). However, the large volume change and sluggish kinetics due to the large ionic size of K⁺ cause inferior rate capability and poor cycling stability for the graphite anode. Herein, we report highly crystalline graphite nanofibers (GNFs) as an anode material for PIBs, which deliver flat voltage plateaus with a high specific capacity of 257 mA h g⁻¹. The highly graphitized, fiber-shaped nanostructure not only mitigates the volume expansion caused by K⁺-intercalation but also facilitates both ionic diffusion and electron transfer. GNFs achieve a long cycle life of 1 year with 99% capacity retention and fast K⁺-intercalation kinetics. Moreover, the low-defect structure of GNFs ensures a high initial coulombic efficiency of up to 74.23%. A potassium-ion full-cell prototype featuring GNFs anode and Prussian blue analogue cathode demonstrates a high energy efficiency of up to 90.6%. This low-defect graphitic nanofiber may offer insights into the design of carbon-based anodes for PIBs.