The practical exploitation of the high-capacity Si anodes suffers from the insufficient cation utilization degree in the energy-dense batteries, which originates from unstable interfacial dynamics, lithiation-induced mechanical stress, and irreversible Li trapping in the alloy intermediates. Herein, we develop a scalable, indirect mechanical calendaring approach to enable the homogeneous prelithiation process, specifically through interpolating an intermediate buffer layer (IBL) with tunable electronic/ionic pathways in-between the lithium foil source and the target high-capacity electrode. Upon the prototype assembly of various prelithiated Si/Graphite anodes (450-1000 mAh g(-1) at the constant areal capacity of 4.6 mAh cm(-2)) and the LiNi0.8Co0.1Mn0.1O2 cathode (NCM811, 23 mg cm(-2) for the double-sided electrode), the enhanced Li utilization degree with the highest energy density up to 362 Wh kg(-1) could be achieved on the realistic cell level (1.6 Ah pouch model). More encouragingly, the reversible phasic evolution of both the cathode and anode, upon the Li+ inventory replen-ishment, are real-time tracked by the transmission-mode operando X-ray diffraction (XRD). This IBL-regulated approach is further extended to construct an environmental-adaptive composite film that integrates the metallic Li source, the prelithiation of which could well function even at the extreme humid conditions (long-time shelf life or relative humidity up to 85%).