LAUSR

Constructing a gradient structure has emerged as a promising strategy for alleviating electromagnetic pollution. Nevertheless, challenges remain in relatively high density and weak bonding force between multilayers. Herein, inspired by the biological leaf structure, a gradient oxidation‐assisted calcination strategy is proposed to prepare ultralight, gradient, and pure carbon sponges with a “disordered skin‐ordered core” structure, named O‐CMS. The O‐CMS avoids high density and weak bonding force between multilayers. Meanwhile, the gradient degree of graphitization between the “skin” and “core” of O‐CMS guarantees that microwaves can fully enter the interior and be absorbed. Benefiting from the appropriately regulated gradient degree of graphitization, the as‐prepared O‐CMS exhibits a maximum absorption efficiency of more than 99.9999% (a minimum reflection loss of −65.3 dB) at an ultralight filler loading of 5 wt.%, with a wide effective absorption bandwidth of 6.62 GHz that covering the whole Ku‐band. Particularly, the radar cross‐section reduction value of O‐CMS can reach 31.88 dB m2, indicating its competitive radar stealth capability. The gradient architecture incorporating vacancy defects also endows O‐CMS with good thermal stealth performance. Specifically, its temperature maintained below 40 °C after heating at 80 °C for 120 min. This study provides an efficient pathway to develop radar‐infrared compatible stealth materials.