Charge Dynamics Engineering Sparks Hetero-Interfacial Polarization for an Ultra-Efficient Microwave Absorber with Mechanical Robustness

Microwave absorbers with high efficiency and mechanical robustness are urgently desired to cope with more complex and harsh application scenarios. However, manipulating the trade-off between microwave absorption performance and mechanical properties is seldom realized in microwave absorbers. Here, a chemistry-tailored charge dynamic engineering strategy is proposed for sparking hetero-interfacial polarization and thus coordinating microwave attenuation ability with the interfacial bonding, endowing polymer-based composites with microwave absorption efficiency and mechanical toughness. The absorber designed by this new conceptual approach exhibits remarkable Ku-band microwave absorption efficiency (-55.3 dB at a thickness of 1.5 mm) and satisfactory effective absorption bandwidth (5.0 GHz) as well as desirable interfacial shear strength (97.5 MPa). The calculated differential charge density depicts the uneven distribution of space charge and the intense hetero-interfacial polarization, clarifying the structure-performance relationship from a theoretical perspective. This work breaks through traditional single performance-oriented design methods and ushers a new direction for next-generation microwave absorbers.

Diagnosing and Correcting the Failure of the Solid-State Polymer Electrolyte for Enhancing Solid-State Lithium-Sulfur Batteries

Solid-state polymer electrolytes (SPEs) attract great interest in developing high-performance yet reliable solid-state batteries. However, understanding of the failure mechanism of the SPE and SPE-based solid-state batteries remains in its infancy, posing a great barrier to practical solid-state batteries. Herein, the high accumulation and clogging of "dead" lithium polysulfides (LiPS) on the interface between the cathode and SPE with intrinsic diffusion limitation is identified as a critical failure cause of SPE-based solid-state Li-S batteries. It induces a poorly reversible chemical environment with retarded kinetics on the cathode-SPE interface and in bulk SPEs, starving the Li-S redox in solid-state cells. This observation is different from the case in liquid electrolytes with free solvent and charge carriers, where LiPS dissolve but remain alive for electrochemical/chemical redox without interfacial clogging. Electrocatalysis demonstrates the feasibility of tailoring the chemical environment in diffusion-restricted reaction media for reducing Li-S redox failure in the SPE. It enables Ah-level solid-state Li-S pouch cells with a high specific energy of 343 Wh kg^-1 on the cell level. This work may shed new light on the understanding of the failure mechanism of SPE for bottom-up improvement of solid-state Li-S batteries.