Graphene Oxide Block Derived Edge-Nitrogen Doped Quasi-Graphite for High K⁺ Intercalation Capacity and Excellent Rate Performance

The intercalation capacity at low potential of carbon-based anode plays a significant role for developing potassium ion batteries (PIBs) with high energy density. However, the inferior rate and cyclic performance caused by repeated insertion/extraction of large K⁺ tremendously restricts the practical application of PIBs. Herein, a quasi-graphite structure with abundant edge-nitrogen doping, micropores structure, and enhanced graphite nanodomains via in situ polymerization of oligoaniline in-between graphene oxide blocks and subsequent carbonization is proposed. The macro-ordered multilayered structure with micro-ordered graphite nanodomains can provide efficient K⁺ insertion/extraction channels, thus greatly increasing the intercalation capacity at low potentials. Moreover, the high edge-nitrogen doping (97%) is of great importance for improving K⁺ transfer kinetics, particularly at high current densities. As a result, the anode exhibits a high discharge capacity below 0.5 V (303 mAh g⁻¹ at 0.05 A g⁻¹), outstanding rate performance (113 mAh g⁻¹ at 5 A g⁻¹), and long-term cycle stability (176 mAh g⁻¹ at 1 A g⁻¹ after 2000 cycles). The K⁺ intercalation mechanism and enhanced kinetics are systematically probed by in situ Raman spectroscopy, ex situ X-ray diffraction (XRD) spectra, and theoretical calculations. This results demonstrate that the construction of quasi-graphite with heteroatom doping is feasible for large ion storage.