<p>Hollow carbon spheres (HCSs) have emerged as promising anode materials for lithium-ion batteries (LIBs), yet their practical application is hindered by intrinsic limitations. Excessive internal voids reduce the tapped density and volumetric energy density, while poor interparticle connectivity increases transport resistance and compromises rate capability. Here, we present a series of nitrogen-doped hollow carbon sphere clusters (HCSCs) with varying hollow diameters (20&#xa0;nm, 100&#xa0;nm, and 300&#xa0;nm), achieved via a combined spray-drying and solution-stirring approach. The 20-HCSCs with ultra-small cavities (20&#xa0;nm) markedly enhances tap density, while cluster-level interconnectivity establishes continuous pathways for efficient Li⁺ and electron transport, thereby enabling rapid charge/discharge kinetics and high volumetric capacity. Consequently, the 20-HCSCs electrodes exhibit an exceptional reversible capacity of 447.3 mAh cm^-3 after 90 cycles at 0.2&#xa0;C, surpassing that of 100-HCSCs, 300-HCSCs electrodes and conventional graphite electrodes (around 372 mAh cm^-3), and demonstrate remarkable high-rate cyclability, retaining 68.5 mAh cm^-3 after 3000 cycles at 50&#xa0;C. The ultrahigh volumetric capacity mitigates the volumetric penalty typically imposed by hollow structures, offering a viable strategy to reconcile high capacity, fast-charging capability, and competitive volumetric performance in carbonaceous anodes.</p> Graphical abstract <p>Ultra-small-cavity HCSC anodes with both high volumetric energy density and fast-charging capability </p>