A nanocomposite consisting of both LiF and transition metal Co as general inactive electrochemical materials fabricated by pulsed laser deposition exhibits significant electrochemical activity. The charge and discharge measurement indicate that the first charge capacity of for the cell is found to release Li. The process of releasing Li from the as-deposited LiF–Co nanocomposite thin films is confirmed by ex situ high resolution transmission electron microscopy and selected area electron diffraction measurements. These results provide direct experimental evidence to support the decomposition of LiF driven by the transition metal Co. LiF–Co nanocomposite electrodes may be found to be a new good candidate for Li storage material.
Silicon, with advantages such as high theoretical capacity and relatively low working potential, has been regarded as promising when it is used for lithium-ion battery anodes. However, its practical application is impeded by the intrinsic low electrical conductivity and the dramatic volume change during the lithiation/delithiation process, which leads to a rapid capacity fading of the electrode. In this regard, we design silicon nanoparticles homogeneously coated with a phenolic resin-based carbon layer as a core-shell nanocomposite via a facile self-assembly method followed by carbonization. The surrounding carbon shell, confirmed by transmission electron microscopy and Raman spectroscopy, is not only beneficial to the formation of a stable solid electrolyte interface film, but the electrical conductivity of the electrode is also enhanced. A high and stable specific capacity of nearly 1000 mA h g-1 is achieved at C/3 after 200 cycles with a coulombic efficiency of >99.6%. The entire synthesis process is quite simple and easy to scale up, thus having great potential for commercial applications.
Abstract Effects of alkaline earth metal elements and their synergistic roles with Ta for the modified Li 7 La 3 Zr 2 O 12 (LLZO) are discussed. Li 7.1 La 3 Zr 1.95 M 0.05 O 12 (M = Mg, Ca, Sr, Ba) with the substitution of alkaline earth metal ions for Zr 4+ and Li 6.5 La 3 Zr 1.35 Ta 0.6 M 0.05 O 12 (M = Mg, Ca, Sr, Ba) with the co-substitution of alkaline earth metal ions and Ta 5+ for Zr 4+ are prepared. The sole substitution of alkaline earth metal elements for Zr in LLZO have little effects on improving ionic conductivity, while the modified LLZO with synergistically co-doping Ta and alkaline earth metal elements can achieve the great enhancement of ionic conductivity. The order of ionic conductivity influenced by Ta 5+ and alkaline earth metal ions (Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ ) co-substitution for Zr 4+ demonstrates a strong correlation with ionic radii of Mg 2+ /Ca 2+ /Sr 2+ /Ba 2+ . Particularly, the enhanced Li 6.5 La 3 Zr 1.35 Ta 0.6 Mg 0.05 O 12 with the joint substitution of Mg and Ta delivers a highest ionic conductivity of 3.45 × 10 −4 S cm −1 at room temperature.
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