In-depth insights into critical role of aromatic C(sp²)–H on Li⁺ storage

The development of high-sloping-capacity carbons enables the creation of high-power lithium-ion batteries and capacitors (LIBs/LICs). Among the various heteroatom-doped carbon materials, hydrogen-rich carbon appears to be a promising candidate due to its facile synthesis and high capacity for Li⁺ storage. Nevertheless, conclusive data are still lacking to elucidate the fundamental function of the hydrogen-terminated groups (C–H configuration) in Li⁺ storage. Prof. Lian and his co-workers have utilized an ion-catalyzed self-template method to synthesize the hydrogen-rich carbon nanoribbon (HCNR) with high specific and rate capacity. The HCNR’s Li⁺ storage mechanism is clarified by the use of in situ spectroscopy methods, which reveals that the sp²-hybridization of the protonated carbon atoms undergoes a highly reversible transition to sp³-hybridization for efficient Li⁺ ions uptake ( \({\text{C}}\left( {{\text{sp}}^{2} } \right){-}{\text{H}} + {\text{Li}}^{ + } + {\text{e}}^{ - } \leftrightarrow {\text{C}}\left( {{\text{sp}}^{3} } \right) <_{{{\text{Li}}}}^{{\text{H}}}\) $\text{C}\left({\text{sp}}^2\right)-\text{H}+{\text{Li}}^{+}+{\text{e}}^{-}\leftrightarrow \text{C}\left({\text{sp}}^3\right){<}_{\text{Li}}^{\text{H}}$ ), contributing to the dominant high sloping capacity. This sloping characteristic points to a highly capacitance-dominated storage process with fast kinetics, enabling better rate performance. This discovery provides mechanistic insights into the critical function of aromatic C(sp²)–H in enhancing Li⁺ storage and creates new opportunities for the development of such sloping-type carbons for high-performance rechargeable batteries and capacitors.