Tremendous attention has been paid to carbon-based anodes for lithium-ion and potassium-ion batteries. Nevertheless, conferring high energy storage properties using carbon-based anodes is still challenging. In this work, petroleum coke-based nitrogen-doped porous carbon nanosheets (N-PCSs) were prepared using carbon nitride (g-C₃N₄) as both a template and nitrogen source and tested as advanced anode materials. The as-obtained N-PCSs constructed through an in situ solid-state approach take advantage of both the high capacity and excellent cycling stability. High capacities were obtained for Li-ion and K-ion batteries (407 mAh g^-1 after 500 cycles at 3720 mA g^-1 and 206 mAh g^-1 after 300 cycles at 1000 mA g^-1, respectively); these are some of the best capacities for carbon-based electrode materials and could be ascribed to the unique microstructure of the anodes, i.e., nanosheet morphology, developed porosity, ultrahigh nitrogen doping, and high level of disorder. Meanwhile, this study provides a milestone for high-valued utilization of petroleum coke and other kinds of heavy oil. References: 1. J.-H. Lee, C.-S. Yoon, J.-Y. Hwang, S.-J. Kim, F. Maglia, P. Lamp, S.-T Myung and Y.-K. Sun, Energy Environ. Sci. 2016, 9, 2152. 2. K. Share, A. P. Cohn, R. Carter, B. Rogers and C. L. Pint, ACS Nano, 2016, 10, 9738. 3. M.-G. Jeong, H. L. Du, M. Islam, J.-K. Lee, Y.-K. Sun and H.-G. Jung, Nano Lett. 2017, 17, 5600. Figure 1