Despite great progress of lithium-sulfur (Li-S) battery performance at the laboratory-level,both key parameters and challenges at cell scales to achieve practical high energy density require high-sulfur-loading cathodes end lean electrolytes.Herein,a novel carbon foam integrated by hollow carbon bubble nanoreactors with ultrahigh pore volume of 6.9 cm3·g-1 is meticulously designed for ultrahigh sulfur content up to 96 wt.％.Tailoring polysulfide trapping and ion/electron transport kinetics during the charge-discharge process can be achieved by adjusting the wall thickness of hollow carbon bubbles.And a further in-depth understanding of electrochemical reaction mechanism for the cathode is impelled by the in-situ Raman spectroscopy.As a result,the as-prepared cathode delivers high specific capacitances of 1,269 and 695 mAh·g-1 at 0.1 and 5 C,respectively.Furthermore,Li-S pouch cells with high areal sulfur loading of 6.9 mg·cm-2 yield exceptional practical energy density of 382 Wh·kg-1 under lean electrolyte of 3.5 μL-mg-1,which demonstrates the great potential for realistic high-energy Li-S batteries.