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Author: Mikhailova, Daria × Publisher: Lausanne : Frontiers Media ×

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    Studies of Li2Fe0.9M0.1SO Antiperovskite Materials for Lithium–Ion Batteries: The Role of Partial Fe2+ to M2+ Substitution
    (Lausanne : Frontiers Media, 2021) Gorbunov, Mikhail V.; Carocci, Salvatore; Gonzalez Martinez, Ignacio G.; Baran, Volodymyr; Mikhailova, Daria
    Cubic Li2Fe0.9M0.1SO antiperovskites with M–Co2+, or Mn2+ were successfully synthesized by a solid-state technique, and studied as cathode materials in Li-batteries. The influence of the Co, and Mn cation substitution of Fe in Li2FeSO on the resulting electrochemical performance was evaluated by galvanostatic cycling, while the reaction mechanism was explored by applying operando X-ray absorption and X-ray diffraction techniques using synchrotron radiation facilities. Even 10% Fe-substitution by these metals completely changes the structural behavior of the material upon Li-removal and insertion, in comparison to Li2FeSO. The Co-substitution significantly improves cyclability of the material at high current densities in comparison to the non-substituted material, reaching a specific capacity of 250 mAh/g at 1C current density. In contrast, the Mn-substitution leads to deterioration of the electrochemical performance because of the impeded kinetics, which may be caused by the appearance of a second isostructural phase due to formation of Jahn-Teller Mn3+ cations upon delithiation.
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    Polypyrrole Wrapped V2O5 Nanowires Composite for Advanced Aqueous Zinc-Ion Batteries
    (Lausanne : Frontiers Media, 2020) Qin, Xinghua; Wang, Xinyu; Sun, Juncai; Lu, Qiongqiong; Omar, Ahmad; Mikhailova, Daria
    Aqueous zinc-ion batteries (ZIBs) have obtained increasing attention owing to the high safety, material abundance, and environmental benignity. However, the development of cathode materials with high capacity and stable cyclability is still a challenge. Herein, the polypyrrole (PPy)-wrapped V2O5 nanowire (V2O5/PPy) composite was synthesized by a surface-initiated polymerization strategy, ascribing to the redox reaction between V2O5 and pyrrole. The introduction of PPy on the surface of V2O5 nanowires not only enhanced the electronic conductivity of the active materials but also reduced the V2O5 dissolution. As a result, the V2O5/PPy composite cathode exhibits a high specific capacity of 466 mAh g–1 at 0.1 A g–1 and a superior cycling stability with 95% capacity retention after 1000 cycles at a high current density of 5 A g–1. The superior electrochemical performance is ascribed to the large ratio of capacitive contribution (92% at 1 mV s–1) and a fast Zn2+ diffusion rate. This work presents a simple method for fabricating V2O5/PPy composite toward advanced ZIBs.