Lignite-based hard carbon for high-performance potassium-ion battery anode

Amorphous C has the advantages of low-cost and adjustable interlayer spacing, which exhibits great potential in K⁺ storage. However, the sluggish diffusion kinetics of K⁺ in the C lattice and mediocre capacity limit the use of C materials as anodes in potassium-ion batteries (PIBs). Herein, we develop an N-doped hierarchical porous C derived from lignite by a simple carbonization activation process. The resulting N-doped hierarchical porous C delivers reversible capacities of 314 mAh g⁻¹ after 100 cycles at 0.1 A g⁻¹ and 124.3 mAh g⁻¹ after 1500 cycles at 1.0 A g⁻¹, when utilized as anode materials for PIBs. The outstanding reversible capacity and excellent cyclic performance can attribute to the porous structure and N doping, which improves electronic conductivity and facilitates K⁺ insertion. This research aids in the development of high-performance anode materials for PIBs and provides some insights into the manufacturing of heteroatom-doped C materials.