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To prepare a hierarchical micro-nano structure FeF3·0.33H2O simply and economically, a one-pot method with dual surfactants was used. Scanning electron microscopy and a Fourier transformation infrared spectrometer revealed that polyvinyl pyrrolidone (PVP) regulates the morphology of the material, while cetyltrimethylammonium bromide (CTAB) can reshape FF@PVP, it can not only remove PVP at room temperature, but also obtain a hierarchical micro-nano structure. The electrochemical results show that the hierarchical micro-nano structure FF(1.5CTAB 0.5PVP) has the best electrochemical performance. It maintained a high specific capacity of 109.4 mAh g−1 after 100 cycles at 1 C. In particular, under the ultra-high rate discharge of 20 C, the ultra-high specific discharge capacity of 66.4 mAh g−1 was reached. The FF(1.5CTAB 0.5PVP)'s excellent electrochemical performance is mainly due to a large contact area between the electrolyte and active materials. [ABSTRACT FROM AUTHOR]

Li 4 Ti 5 O 12 (LTO) nanoparticles coated with two types of carbon were synthesized for the anode of lithium ion batteries (LIBs). One type was LTO coated with crystalline carbon from graphite-based mesocarbon microbeads (LTO-MCMB), and the other type was LTO coated with amorphous carbon (LTO-AMC). Transmission electron microscopy (TEM) results indicate that MCMB and amorphous carbon were uniformly coated on the LTO nanoparticles surface using a facile solid-state synthesis method. Electrochemical characterization results show that the rate capability and cycle performance of LTO-MCMB were better than those of LTO-AMC. For example, at an extremely fast charge and discharge rate of 20C (~3 min charge or discharge), LTO-MCMB with 3 wt% MCMB still maintained a high specific capacity of 117 mAh g−1, compared with 91 mAh g−1 for LTO-AMC, demonstrating that particle surface engineering at the nanoscale is an efficient method to improve the energy storage performance of the anode material. Unlabelled Image • A solid-state method to synthesize Li 4 Ti 5 O 12 nanoparticles coated with C • The crystalline C coating improved electric conductivity and Li ion diffusivity. • The optimal crystalline C coating is 3 wt% and ~1.2 nm thickness. [ABSTRACT FROM AUTHOR]