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In this work, we synthesize a sandwich-structured graphite-metallic silicon@C (MS-G@C) composite, which shows good electrochemical performance compared to metallic silicon or graphite-metallic silicon. The improved electrochemical performance may be ascribed to the sandwich structure of the composite with the carbon coating on metallic Si and to the metallic Si particles with high electronic conductivity according to the results of four probe tester measurement and a density functional theory study. When evaluated as an anode material for LIBs, the low cost MS-G@C anodes Exhibit 830 mA h g −1 at 0.5 C, 650 mA h g −1 at 1 C, and 251.2 mA h g −1 at 5 C, respectively, and after 100 cycles with an average capacity loss of only 0.02% per cycle at 0.5 C. The synthetic method presented in this paper is provided a facile and low-cost strategy for the large-scale production of silicon-based material as an anode in LIBs. [ABSTRACT FROM AUTHOR]

Commercial lithium-ion batteries with carbon-based anodes exhibit low specific capacities and pose potential safety risks of lithium plating. As possible alternatives, conjugated carboxylic acid-based electrode materials have attracted extensive attention owing to their suitable discharge potential, low solubility in electrolytes, and low-cost reproducibility. However, their theoretical capacities are limited by the number of active sites. In this paper, we introduce 2,2′-bipyridine-5,5′-dicarboxylic acid (H 2 bpy) as a new anode material demonstrating high specific capacity, good cycle stability, and remarkable rate performance in both lithium- and sodium-ion batteries. In particular, H 2 bpy possesses an ultrahigh initial capacity of lithium-ion battery of 1200 mAh g−1 at a current density of 200 mA•g−1, and the specific capacity can maintain 550 mAh•g−1 after 100 cycles. Whereas the sodium-ion battery retains a specific capacity of 258 mAh•g−1 under the same conditions. We find, through density functional theory analysis, that the superior performance is due to the molecular structure and stacking form of H 2 bpy. Furthermore, we perform an ex situ spectroscopic analysis and find that the H 2 bpy electrode has good electrochemical stability. These findings suggest that bipyridine carboxylic acids can effectively broaden the application of heterocyclic carboxylic acids as anode materials. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we report density-functional theory (DFT) calculations at various levels of accuracy to compare the electrochemical properties of several silicate compounds as possible cathode materials in Li-ion batteries. We have tested the already known olivine-like structure (LiMSiO4, M=Mn, Fe, Co, and Ni) and the more recently discovered tetrahedral Pmn21 Li2MSiO4 (M=Mn, Fe, Co, and Ni). Our calculations show the influence of exchange and correlation potentials used to compute the redox potentials, electronic band gaps and other properties of these materials. A detailed study of the multicomponent effect on those characteristics gives us useful insight about how to improve the electrochemical performance of the cathode and its efficiency in the Li-ion battery. [Copyright &y& Elsevier]

In this paper, novel arrays of rutile SnO 2 nanorods (r-SnO 2 -NRs) are successfully grown vertically on the arrays of the rutile TiO 2 nanorods (r-TiO 2 -NRs) and directly supported on the carbon cloth (CC) to form a hierarchical nano-heterostructure material (r-TiO 2 -NRs@r-SnO 2 -NRs/CC) through a two-step hydrothermal process. Such a reverse core-shell nano-heterostructure design with r-SnO 2 -NRs as shell layer epitaxially grown on the r-TiO 2 -NRs backbone is directly used as a binder-free and flexible lithium-ion batteries (LIBs) anode. Both high initial Coulombic Efficiency and high reversible capacity are demonstrated, which are much better that those of the single components. The enhanced electrochemical performances are attributed to a heterostructure of r-TiO 2 -NRs and r-SnO 2 -NRs as well as the unique branched nanostructures. The density functional theory (DFT) analysis further manifest that such a r-TiO 2 -NRs@r-SnO 2 -NRs heterostructure can achieve the faster electron transport kinetics than their single components due to a change in the energy band gap after heterogenization. Due to the arrayed and crosslinked structure of such a anode material and its flexible CC supporter, the strong structure stability and flexibility can be realized for flexible LIBs. [ABSTRACT FROM AUTHOR]