Tailoring sp3/sp2 carbon hybridization to balance the trade-off between active site and conduction for rapid Li-ion intercalation chemistry in dual-carbon batteries

Dual-carbon batteries (DCBs) have emerged as an appealing candidate for large-scale energy storage, yet the common trade-off between active sites and electronic conduction in carbon materials engenders a main challenge towards efficient DCBs. Here, we introduce a heteroatom-doped sp3/sp2 hybridized carbon fiber membrane (cPAN-Gr) as a universal binder-free active electrode that effectively overcomes this trade-off, enabling efficient Li-ion intercalation chemistry for advanced DCBs. By strategically tuning the sp3 and sp2 carbon hybridization, the interlayer interaction, geometric and electronic structures of cPAN-Gr are simultaneously optimized, which facilitates rapid Li-ion adsorption, smooth interlayer transport, and efficient electron transport by maximizing the synergy between sp2- and sp3-hybridized carbon. This, coupled with a 3D porous network structure, endows the cPAN-Gr with superior Li-ion storage capability and fast reaction kinetics. Therefore, the cPAN-Gr electrode delivers a high reversible capacity of 345 mA h g−1, excellent rate capability (50 C), and an ultralong cycle life over 10,000 cycles, outperforming other reported carbon-based electrodes. Moreover, the constructed DCB exhibits a large specific capacity of 135 mA h g−1, long-term cyclability over 500 cycles, and a remarkable energy density of 524.4 Wh kg−1. The cPAN-Gr electrode can also be expanded to construct a LiFePO4//cPAN-Gr full battery. Combined theoretical and experimental studies reveal the crucial role of an optimized sp3/sp2 ratio (79%) with topological defects and pyridine/pyrrolic N sites on the performance enhancement. This work offers new insights into the design of advanced carbon materials for DCBs and beyond.