Spatially Confined Carbonization-Induced Reorganization of Microcrystals and Nanopores in Carbon Framework for Enhanced Sodium Plateau Storage

Non-graphitic carbons are considered as promising anode candidates for sodium-ion batteries (SIBs). Regulation of microcrystalline state and pore configuration of carbon anode is key to boost sodium plateau storage. Herein, a facile strategy is developed to create abundant closed nanopores and extensive pseudo-graphitic regions in carbon framework by the spatially confined carbonization of coal tar within the nanopores of commercial activated carbon (AC). The interlayer spacing, microcrystalline size, and nanopore structures of the obtained carbon materials can be facilely adjusted by changing the amount of coal tar and carbonization temperature. As expected, the optimized sample delivers an excellent sodium storage capacity of 361.7 mAh g⁻¹ at 0.1C with a high ICE value of 81.6%. The constructed full cell displays a high energy density of 254.3 Wh kg⁻¹ with an average voltage of 3.19 V. The detailed experimental studies and in/ex situ electrochemical tests reveal that the enhanced sodium plateau storage is related to the development of pseudo-graphitic phase and closed nanopores. In addition, the high mass loading electrode (≈11 mg cm⁻²) and 10-layered pouch full cell demonstrate excellent electrochemical performance. This work provides a practical strategy for collaboratively designing microcrystalline and closed pore structures in carbon anode for high-performance SIBs.