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

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

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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