6 research outputs found

    ZrO<sub>2</sub>‑Nanoparticle-Modified Graphite Felt: Bifunctional Effects on Vanadium Flow Batteries

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    To improve the electrochemical performance of graphite felt (GF) electrodes in vanadium flow batteries (VFBs), we synthesize a series of ZrO<sub>2</sub>-modified GF (ZrO<sub>2</sub>/GF) electrodes with varying ZrO<sub>2</sub> contents via a facile immersion-precipitation approach. It is found that the uniform immobilization of ZrO<sub>2</sub> nanoparticles on the GF not only significantly promotes the accessibility of vanadium electrolyte, but also provides more active sites for the redox reactions, thereby resulting in better electrochemical activity and reversibility toward the VO<sup>2+</sup>/VO<sub>2</sub><sup>+</sup> and V<sup>2+</sup>/V<sup>3+</sup> redox reactions as compared with those of GF. In particular, The ZrO<sub>2</sub>/GF composite with 0.3 wt % ZrO<sub>2</sub> displays the best electrochemical performance with voltage and energy efficiencies of 71.9% and 67.4%, respectively, which are much higher than those of 57.3% and 53.8% as obtained from the GF electrode at 200 mA cm<sup>–2</sup>. The cycle life tests demonstrate that the ZrO<sub>2</sub>/GF electrodes exhibit outstanding stability. The ZrO<sub>2</sub>/GF-based VFB battery shows negligible activity decay after 200 cycles

    Polysulfides Capture-Copper Additive for Long Cycle Life Lithium Sulfur Batteries

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    Copper powder was introduced into the lithium sulfur battery system to capture intermediate polysulfides and Cu<sub><i>x</i></sub>S (<i>x</i> = 1 or 2) species was generated depending on the chain length of polysulfides. This phenomenon was verified by X-ray absorption near edge structure technique. The results indicated that copper can be oxidized to CuS by Li<sub>2</sub>S<sub><i>x</i></sub> (<i>x</i> ≥ 6), and a mixture of Cu<sub>2</sub>S and CuS was obtained when <i>x</i> ranges from 3 to 6. While Cu<sub>2</sub>S is eventually formed in the presence of Li<sub>2</sub>S<sub>3</sub>. After several cycles activation, the polysulfide-shuttle effect and self-discharge phenomenon which hinder the application of lithium sulfur batteries are found nearly eliminated Further experiments demonstrated that in the case of Cu<sub>2</sub>S generation, a high specific sulfur capacity of 1300 mAh g<sup>–1</sup> could be delivered, corresponding to 77.6% sulfur utilization, while the Coulombic efficiency approximates around 100%. Self-discharge experiment further demonstrated that polysulfides almost disappear in the electrolyte, which verified the polysulfide-capture capability of copper

    Confined Solid Electrolyte Interphase Growth Space with Solid Polymer Electrolyte in Hollow Structured Silicon Anode for Li-Ion Batteries

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    Silicon anodes for lithium-ion batteries are of much interest owing to their extremely high specific capacity but still face some challenges, especially the tremendous volume change which occurs in cycling and further leads to the disintegration of electrode structure and excessive growth of solid electrolyte interphase (SEI). Here, we designed a novel approach to confine the inward growth of SEI by filling solid polymer electrolyte (SPE) into pores of hollow silicon spheres. The as-prepared composite delivers a high specific capacity of more than 2100 mAh g<sup>–1</sup> and a long-term cycle stability with a reversible capacity of 1350 mAh g<sup>–1</sup> over 500 cycles. The growing behavior of SEI was investigated by electrochemical impedance spectroscopy and differential scanning calorimetry, and the results revealed that SPE occupies the major space of SEI growth and thus confines its excessive growth, which significantly improves cycle performance and Coulombic efficiency of cells embracing hollow silicon spheres