An interface-free integrative graphitic carbon network film with defective and S/O-Codoped hollow units for voltage-stable, Ultra-fast and long-life potassium ion storage

In the K-storage process, graphitic carbon exhibits unique practical plateau potential but suffers terrible rate and cycle performance, because its perfect long-range ordered carbon structure, small lattice space and high contact/interface resistance are still bottlenecks to limit the kinetics and structural stability. Herein, we prepare a novel interface-free integrative graphitic carbon network film on a large scale, and enlarged its lattice distance and reasonably introduce defects (ED-IGCN) to boost kinetics and cyclability via a plasma-enhanced etching/S-doping process. Typically, the ED-IGCN entails ultra-thin hollow graphitic units (diameter ∼ 10 nm, shell wall ∼ 1 nm) interconnected by sp2 hybrid covalent bonds, providing an interface-free highly conductive network. Additionally, the defective long-range ordered carbon arrangement and enlarged lattice distance ensured numerous open channels and shortened pathways with low diffusion barrier for boosting the fast (de)potassiation kinetics. When applied in PIB, the ED-IGCN anodes delivered a high reversible capacity of 408 mAh g−1 at 20 mA g−1, and ultra-high rate and long-term cyclability without expensing its unique discharge plateau. The capacity maintained up to 91.1 mA h g−1 after 10,000 cycles at 5 A g−1 with a capacity retention of ∼ 60% (∼51% after 11,000 cycles), which is not inferior to that of any graphitic carbon reported previously. We separated the diffusive capacity, and pseudo-/double-layer capacitive contributions, and verified that the plasma treating process enhanced the capacitive K-storage mechanism which give great contribution to the fast kinetics. A full-cell based on potassium Prussian blue (KPB) cathode and ED-IGCN anode delivered an initial reversible capacity of 177 mAh g−1 at 1000 mA g−1, and retained ∼ 70% after 50 cycles, further demonstrating the ultra-high rate capability of ED-IGCN in practical application. The results provide new insights into the design and structure regulations of graphitic carbon for fast-charging batteries with stable working voltages and an understanding of the diffusion acceleration mechanism in graphitic carbon materials.