Tuning π-π carbon restacking hindrance to remodify hard carbon crystallites for advanced sodium energy

Hard carbon imposes great importance to boost the deployment of sodium-ion batteries (SIBs) for grid-scale energy storage. However, the precise structure regulation of carbon crystallites is highly critical yet intractable. Herein, we demonstrate a powerful steric bridging strategy to manipulate the pseudographitic crystallites of hard carbon for advanced sodium storage. Molecules with branched carboxyl groups are revealed to enable strong steric bridging effect with carbon precursors, which significantly hinders the π-π restacking of carbon layers upon pyrolysis. This effect yields twisted pseudographitic crystallites with a favorable feature of extended carbon interlayer spacing and a concomitant closed pore structure. Accordingly, the refined sample delivers an enhanced capacity of 323.9 mAh g⁻¹ accompanying with a high initial Coulombic efficiency of 87.4 % and superior cycling lifespan over 4500 cycles. Extensive characterizations are conducted to unveil the interface kinetics and the associated sodium storage mechanism. The study explicitizes the molecular bridging tactic to finely remodify the microstructure of hard carbons for high-performance SIBs.