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Highlights • The NiCo 2 O 4 and NiCo 2 O 4 @MnO 2 composites synthesized by a hydrothermal method. • NiCo 2 O 4 @MnO 2 maintained reversible capacities of 1000 mA h g−1 after 100 cycles. • NiCo 2 O 4 @MnO 2 electrodes demonstrated an enhanced rate performance. Abstract 3D flower-like NiCo 2 O 4 and NiCo 2 O 4 @MnO 2 were successfully synthesized via a hydrothermal method. Scanning electron microscopy results illustrated that NiCo 2 O 4 is formed by stacking nanosheets, and after reaction in KMnO 4 solution, MnO 2 were evenly coated on the surface of NiCo 2 O 4 formed flower-like structure. The as-synthesized materials were evaluated as an anode materials for lithium-ion batteries, NiCo 2 O 4 and NiCo 2 O 4 @MnO 2 exhibited high specific capacities of 841.9 and 1 000 mA h g−1 after 100 cycles respectively. Moreover, NiCo 2 O 4 @MnO 2 composites demonstrate good rate performance. These enhanced electrochemical properties could be attributed to the distinctive 3D flower-like structure, which increases the contact area between the electrolyte and electrode material to provide more active sites, and reduced volume effects during repeated insertion/extraction of lithium ions. The results suggest that the NiCo 2 O 4 @MnO 2 composites could be promising LIBs anode materials. [ABSTRACT FROM AUTHOR]

A free-standing Si@Co 9 S 8 CF electrode with excellent rate capability and cycling performance was obtained by electrospinning, vulcanization, and carbonization processes as high-performance anode for Li-ion batteries. [Display omitted] • Si@Co 9 S 8 CF films are explored by electrospinning, vulcanization and carbonization. • The yolk-shelled Si@Co 9 S 8 can remarkably alleviate the volume expansion. • The introduction of CFs can improve the electrical conductivity of the electrodes. • The free-standing anode avoids the conventional process of electrode preparation. Silicon-based (Si-based) materials have aroused extensive attention owing to their ultra-high theoretical specific capacity, while the huge volume expansion and inferior electronic conductivity have impeded their practical application in lithium-ion batteries (LIBs). Rational structural design has been regarded as a fascinating strategy, especially for yolk-shell structures. Herein, Si nanoparticles (Si NPs) were encapsulated in ZIF-67 metal–organic frameworks to obtain Si@ZIF-67 particles, which were wrapped in one-dimensional carbon fibers (CFs) by simple processes of electrospinning, vulcanization and carbonization to obtain a free-standing Si@Co 9 S 8 CF electrode. The yolk-shelled Si@Co 9 S 8 particles could remarkably ameliorate the volume variation of Si materials during the lithiation/de-lithiation cycling and the introduction of CFs endowed an efficient one-dimensional electronic pathway accurately to improve the conductivity of composite materials. In addition, it was not negligible that the as-obtained Si@Co 9 S 8 CF films could be as a self-supporting electrode, which avoided the traditional cumbersome procedure of the electrode preparation. The resulting composite electrodes possess an excellent rate performance and an ultra-stable cycling lifespan. We hope this work can provide some novel insights for the development of the self-supporting Si-based electrode materials. [ABSTRACT FROM AUTHOR]

The electromagnetic wave absorption properties of the quaternary composites consisting of reduced graphene oxide (rGO), polyaniline (PANI), FeNi 3 @SiO 2 (FeNi 3 nanocrystals encapsulated in SiO 2 ) nanoparticles had never been reported. In this case, we prepared FeNi 3 @SiO 2 @rGO–PANI quaternary composites and TEM results shows spherical nanoparticles are well distributed on the surface of rGO–PANI nanosheets. The investigation of the electromagnetic wave absorbability reveals that the quaternary composites exhibit wide absorption bandwidth and enhanced electromagnetic wave absorption properties. The absorption bandwidth with reflection loss less than −10 dB (90% attenuation) is up to 6.64 GHz (10.08–10.80 GHz, 12.08–18.0 GHz), and the maximum reflection loss reaches about −40.18 dB at 14.0 GHz with the thickness of 2.4 mm. It is believed that the FeNi 3 @SiO 2 @rGO–PANI composites can serve as excellent electromagnetic wave absorbent and can be widely used in practice. [ABSTRACT FROM AUTHOR]