Combustion‐Driven Lattice Reconstruction Activates Electron Spin and Densifies Electronic States for Synergistic Broadband Microwave Absorption

Abstract Carbon‐based composites typically exhibit narrow microwave absorption bandwidths due to unbalanced electromagnetic responses dominated by either conductive or polarization loss mechanisms. To address this limitation, a combustion‐induced self‐propagating strategy is developed for synthesizing well‐defined high‐entropy oxide/carbon composites, specifically comprising Mg–Fe–Co–Ni–Cu oxides uniformly anchored on graphitized carbon skeletons. This approach utilizes self‐propagating high‐temperature synthesis to drive precursor melting and lattice reconstruction, enabling precise electron spin regulation through symmetry breaking and defect engineering. Integrated electromagnetic measurements, finite element analysis, and density functional theory calculations reveal that lattice reconstruction activates electron spin and densifies electronic states near the Fermi level. The resulting gradient heterogeneous architecture optimizes impedance matching while multiscale polarization centers enhance attenuation capacity. The optimized absorber achieves an effective absorption bandwidth of 6.04 GHz at 2.2 mm thickness, covering the entire Ku‐band with 167.3% performance improvement over uncombusted counterparts, while maintaining full X‐band coverage at 3.0 mm. This work establishes a novel paradigm for designing high‐entropy microwave absorbers through lattice reconstruction‐activated spin and electronic state engineering.