Silicon Anodes Incorporating Few-Layer Graphene (FLG) for Improved Cyclability in Li-Ion Batteries

Abstract

Silicon remains a promising anode material for next generation lithium-ion batteries despite the well-documented issues associated with it, namely fast capacity fade and volume expansion. The element’s abundance and high capacity (3579mAh/g: almost 10 times higher than the capacity of graphite) has made it the focus of high profile global research for the last decade. However, the problems still facing Si-based battery commercialization are yet to be successfully overcome. To address this an optimized electrode composition and microstructure are considered as an effective approach. Several studies have been conducted towards hybrid silicon/graphene electrodes with promising results achieved[1], [2], [3]. However, most of these studies relied on synthetic routes to make silicon and graphene that relied on complicated chemical methods, such as electrophoretic deposition or chemical vapor deposition; neither of which are considered practical for large-scale manufacture. In this study a matrix formulation of Si/FLG hybrid electrodes is used, manufactured with micron-sized silicon, using physical mixing methods that are employed in industrial electrode fabrication. A resulting formulation for a Si/FLG hybrid electrode will be described, which has achieved up to 1900mAh/g discharge capacity with 95% capacity retention after 200 cycles. Further characterisation has investigated the impact from graphene in terms of long-term electrochemical performance on an electrode formulated only with FLG as the active material. AC impedance and tensile property testing has also been performed, as the mechanical properties of graphene-containing electrodes has been minimally reported to date. This additional characterisation was included to indicate what exactly the graphene is contributing towards battery performance and to clarify the improvement of conductivity and flexibility with its incorporation. [1] Ren, J.-G. et al. Silicon-Graphene Composite Anodes for High-Energy Lithium Batteries. Energy Technol. 1, 77–84 (2013). [2] Chou, S.-L. et al. Enhanced reversible lithium storage in a nanosize silicon/graphene composite. Electrochem. commun. 12, 303–306 (2010). [3] Zhang, Y. Q. et al. Silicon/graphene-sheet hybrid film as anode for lithium ion batteries. Electrochem. commun. 23, 17–20 (2012). Figure 1