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At present, microwave absorbers are prepared by dispersing absorbing nanomaterials in a binder, which can lead to the aggregation of nanomaterials in the binder and further affect the optimization of the absorption performances. Hybrid micro/nano-scale structures are beneficial for buffering agglomeration phenomena and the construction of multiple interfaces. Here, Ni@C nanocapsules are conjugated onto flower-like BiOI microspheres, forming micro/nano-scale hybrid composites. The multiple interfaces between BiOI microspheres and Ni@C nanocapsules can bring enhanced dielectric loss and increased attenuation constant, resulting in the enhancement of absorption capacity (the optimal reflection loss reaches  −61.35 dB), increased width of the effective absorption band (the maximum effective bandwidth, fEmax, is 5.86 GHz) and the reduction of absorption thickness (the thickness corresponding to fEmax is 1.7 mm). This study highlights a simple idea for the optimization of electromagnetic absorbing performance, which is of great significance in the development of microwave absorbers.

Fe3O4/MnO2 core–shell structured nanocomposites have been synthesized by a one-pot approach at ambient temperature and pressure.

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The synthesis of magnetite (Fe 3 O 4 )@C nanocapsules with Fe 3 O 4 nanoparticles as the core and onion-like carbon as the shell has been reported. The electromagnetic (EM) characteristics and electrochemical performance are studied. The onion-like carbon shell improves dielectric loss and EM matching degree, leading to enhanced EM properties. The optimal reflection loss (RL) value of the Fe 3 O 4 @C-paraffin composite is À45.9 dB at 16.6 GHz at a thickness of 2.4 mm and the absorption bandwidth of 7.2 GHz (RL exceeding À10 dB) covers 9.8-17.0 GHz at 3.0 mm. The EM absorption mechanism may be explained by the combination of the EM loss model and the quarter-wavelength cancellation condition.The onion-like defective carbon shell not only can accommodate the volume change of Fe 3 O 4 nanoparticles but also can prevent the formation of solid electrolyte interface films on the surface of nanoparticles, resulting in the remarkable electrochemical performance for lithium ion batteries (LIBs).The Fe 3 O 4 @C nanocapsules display an attractive cycling performance up to 300 cycles (918 mA h g À1 retained at 0.1 A g À1 ) and a high initial coulomb efficiency of 85.6%. A capacity of 934 mA h g À1 is recoverable after the charge-discharge process at high rates. The present work presents Fe 3 O 4 @C nanocapsules as a new kind of EM absorptive anode material for LIBs.