The Alkynyl π Bond of sp-C Enhanced Rapid, Reversible Li–C Coupling to Accelerate Reaction Kinetics of Lithium Ions

Graphdiyne (GDY) is a promising anode for rechargeable batteries with high capacity, outstanding cyclic stability, and low diffusion energy. The unique structure of GDY endows distinctive mechanisms for metal-ion storage, and it is of great significance to further visualize the complex reaction kinetics of the redox process. Here, we systematically tracked the reaction kinetics and provided mechanistic insights into the lithium ions in the GDY to reveal the feature of the cation-π effect. It has been demonstrated that, unlike only one π bond in sp²-C, π electrons provided by one of the two alkynyl π bonds in sp-C can achieve proper interaction and speedy capture of lithium ions; thus, reversible Li-C coupling can be formed between electron-rich sp-C and lithium ions. In addition to interlayer intercalation in sp²-C regions, nanopores filling triangular-like cavities composed of highly conjugated sp-C contribute to the major capacity in flat voltage plateau regions. Therefore, a capture/pores filling-intercalation hybrid mechanism can be found in GDY. The coexistence of sp and sp² carbon enables GDY electrodes with rapid Li⁺ diffusion, high capacity of over 1435 mAh g^-1, extraordinary rate capability, and cyclic stability for more than 10000 cycles at 10A g^-1. These results provide guidance for developing advanced carbon electrodes with optimized reaction kinetics for rechargeable batteries.