A Few-Layer Quasi-Graphite Anode With Rigid-Flexible Synergy for High-Performance Potassium-Ion Batteries

Potassium-ion batteries (KIBs) have emerged as promising candidates for grid-scale energy storage due to abundant K resources and reversible K⁺ de-/intercalation in graphite (KC₈, 279 mAh g^-1). However, practical application is hindered by severe volume expansion (≈60% for K⁺ vs. ≈10% for Li⁺), which induces stress accumulation, structural degradation, and capacity fading. Here, we develop a few-layer quasi-graphite (QGr) via structural reconstruction of graphite to regulate its mechanical stability and kinetics. The resulting QGr architecture integrates ordered domains with mechanically compliant graphene interfaces, creating a rigid-flexible synergy that alleviates intercalation-induced stress and lowers the kinetic barrier for K⁺ intercalation. As a result, the QGr anode delivers a reversible capacity of 279.2 mAh g^-1 at 0.1 A g^-1 and maintains stable cycling over 1200 cycles. Notably, QGr exhibits a pronounced low-voltage plateau of 246.1 mAh g^-1 below 0.5 V. Combined in situ Raman spectroscopy and kinetic analysis demonstrates that K⁺-storage in QGr is dominated by an intercalation mechanism. This work demonstrates that rational structural engineering of graphite can simultaneously regulate structural stability and ion transport kinetics, providing a promising strategy for designing high-energy KIBs.