High capacity anode materials have been wandering around the corner of commercialization for advanced lithium ion batteries. Nanostructuring these electrochemical active materials through reserving large void spaces have been extensively utilized to extend cycling stability in terms of volume change view. However, the ultra-low volumetric capacity associated with the loosely-packed nano-sized materials is a critical damage for the practical applications of high capacity materials. Here in a highly dense nanocomposite anode, we successfully eliminate the cycling failure of high capacity anode by suppressing atom migration during lithiation/delithiation, demonstrating a novel approach of spatially-confined electrochemical reactions through which the atoms/clusters can be rapidly lithiated/delithiated at their original sites. The spatially-confined lithiation/delithiation effectively avoids inter-cluster migration and perfectly keeps full structure integrity during prolonged cycling. Impressively, a volumetric capacity as high as 6034.5 mAh cm-3 (1206.9 mAh g-1, 86.4% of the first discharge capacity) can still be maintained after 200 stable cycles and 4704.0 mAh cm-3 (940.8 mAh g-1) is retained at an ultra-high current density of 20 A g-1. This spatially-confined lithiation/delithiation offers novel insight to enhance cycling performance of high capacity anode materials. The successful demonstration of dense anode may shed light on the practical applications of high capacity materials for the upgrade of lithium ion batteries.