Silicon/Wolfram Carbide@Graphene composite: enhancing conductivity and structure stability in amorphous-silicon for high lithium storage performance

By Sun, Wei; Hu, Renzong; Liu, Hui; Zhang, Hanying; Liu, Jiangwen; Yang, Lichun; Wang, Haihui; Zhu, Min
Published in Electrochimica Acta NULL 2016

Abstract

Abstract Improving the electron conductivity and lithiated structure stability for Si anodes can result in high stable capacity in cells. A Silicon/Wolfram Carbide@Graphene (SW@G) composite anode is designed and produced by a simple two-step ball milling the mixture of coarse-grained Si with good conductive wolfram carbide (WC) and graphite. The SW@G composite consists of multiple-scale {WC} particles, which are uniformly distributed in amorphous Si matrices, and wrapped by graphene nanosheets (GNs) on the outside. Owing to the unique concrete-like core-shell structure, the wrapping of {GNs} on the Si improves the conductivity and structural stability of the composite. The inner {WC} particles which tightly connect the Si and graphene act as the cornerstone to resist large volumetric expansion of Si during charge/discharge, and in particular serve as the high-speed channels of electrons as well as provide more interface paths for Li+ to accelerate their transfer inside the Si. These contribute to the excellent electrochemical properties of SW@G composite anode, including high volumetric capacity (three times higher than that of graphite), superior rate capability, and long-life stable cycleability. The synthetic method developed in this work paves the way for large-scale manufacturing of high performance Li storage anodes using commercially available materials and technologies.

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