K2 Mn4 O8 /Reduced Graphene Oxide Nanocomposites for Excellent Lithium Storage and Adsorption of Lead Ions.

Ion diffusion efficiency at the solid-liquid interface is an important factor for energy storage and adsorption from aqueous solution. Although K2 Mn4 O8 (KMO) exhibits efficient ion diffusion and ion-exchange capacities, due to its high interlayer space of 0.70 nm, how to enhance its mass transfer performance is still an issue. Herein, novel layered KMO/reduced graphene oxide (RGO) nanocomposites are fabricated through the anchoring of KMO nanoplates on RGO with a mild solution process. The face-to-face structure facilitates fast transfer of lithium and lead ions; thus leading to excellent lithium storage and lead ion adsorption. The anchoring of KMO on RGO not only increases electrical conductivity of the layered nanocomposites, but also effectively prevents aggregation of KMO nanoplates. The KMO/RGO nanocomposite with an optimal RGO content exhibits a first cycle charge capacity of 739 mA h g-1 , which is much higher than that of KMO (326 mA h g-1 ). After 100 charge-discharge cycles, it still retains a charge capacity of 664 mA h g-1 . For the adsorption of lead ions, the KMO/RGO nanocomposite exhibits a capacity of 341 mg g-1 , which is higher than those of KMO (305 mg g-1 ) and RGO (63 mg g-1 ) alone.

Neuron-Inspired Fe3O4/Conductive Carbon Filament Network for High-Speed and Stable Lithium Storage.

Construction of a continuous conductance network with high electron-transfer rate is extremely important for high-performance energy storage. Owing to the highly efficient mass transport and information transmission, neurons are exactly a perfect model for electron transport, inspiring us to design a neuron-like reaction network for high-performance lithium-ion batteries (LIBs) with Fe3O4 as an example. The reactive cores (Fe3O4) are protected by carbon shells and linked by carbon filaments, constituting an integrated conductance network. Thus, once the reaction starts, the electrons released from every Fe3O4 cores are capable of being transferred rapidly through the whole network directly to the external circuit, endowing the nanocomposite with tremendous rate performance and ultralong cycle life. After 1000 cycles at current densities as high as 1 and 2 A g-1, charge capacities of the as-synthesized nanocomposite maintain 971 and 715 mA h g-1, respectively, much higher than those of reported Fe3O4-based anode materials. The Fe3O4-based conductive network provides a new idea for future developments of high-rate-performance LIBs.