Advanced yolk–shell microstructure for high-efficiency electromagnetic wave absorption: a critical review of composition-structure synergy

The rapid proliferation of 5G/6G communication technologies and high-frequency electronic devices has led to escalating electromagnetic (EM) pollution, and EM wave absorbing materials (EWAMs) are crucial for mitigating this pollution. Beyond conventional composition optimization, rational microstructure engineering (such as porous, hollow, and aerogel architectures) has emerged as an alternative and effective route for enhancing the performance of EWAMs. Among these diverse architectures, yolk–shell structures have garnered significant attention because they integrate the advantages of hollow and core–shell configurations. Its unique core-void-shell geometry not only facilitates impedance matching through the regulation of effective permittivity but also provides abundant heterogeneous interfaces for intensified dielectric and magnetic losses. This review provides a comprehensive overview of recent advancements in yolk–shell EWAMs, focusing on the synergy between the chemical composition and microstructural design. We first summarize the typical preparative strategies, including nanocasting, phase engineering, and heterointerface anti-contraction techniques. Then, we categorize and discuss various yolk–shell systems, which range from conventional configurations with single-component cores and single-component shells to novel architectures featuring multi-component cores and shells. Ultimately, we present the prospects and unresolved challenges of yolk–shell materials and anticipate that this review will provide a meaningful reference for advancing the structural design of EWAMs in subsequent research.