After more than 20 years of steady progress, lithium-ion batteries still exhibit modest energy capacities that seem to have reached their asymptotic values with the present combination of graphite at the anode and insertion oxide or phosphate materials at the cathode. New applications, particularly for all-electric vehicles are pushing the development of electrode materials with higher Li storage capabilities, for both electrodes.Silicon, which exhibits the highest known Li-alloying capacity is one of the most promising anode materials.However, Li alloying with Si is accompanied by a large volume change which induces cracking and rapid pulverization of Si-based anodes. Significant improvements in the anode's lifetime as well as chargedischarge rates have been obtained over the past few years by employing Si nanostructures, particularly nanowires. In this paper, we present the main synthesis methods for Si nanowires as well as the alloying properties of Li with Si and review how the use of Si-based nanowires has evolved, thanks to sophisticated material/structure combinations, including core-shell nanowires, composites as well as hollowed nanotube-like approaches.

Silicon exhibits the largest known capacity for Li insertion in anodes of Li‐ion batteries. However, because of large volume expansion/phase changes upon alloying, Si becomes powder‐like after a few charge‐discharge cycles. Various approaches have been explored in the past to circumvent this problem, including the use of nanomaterials, particularly Si nanowires. However, even though nanowires resist cracking very well, anodes based on Si nanowires still see their original capacity fade away upon cycling, because of wire detachment from the substrate, due to the stress generated at their roots upon alloying with Li. Here, we present a silicon nanowire growth strategy yielding highly interconnected specimens, which prevents them from being individually detached from the substrate. We report a ∼100% charge retention after 40 cycles at C/2 rate, without charging voltage limitation. We also show that our anodes can be cycled at 8C rates without damage and we grow nanowires with a density of 1.2 mg/cm2, yielding anodes delivering a 4.2 mAh/cm2 charge density. Finally, we point out that a better understanding of the interactions of silicon with electrolytes is needed if the field is to progress in the future.

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Kinking of semiconductor nanowires grown by the vapour-solid-liquid (VSL) mechanism has long been observed and studied, particularly for Si. A large variety of turning angles for kinked Si nanowires (KSiNWs) has been reported in the literature, but most authors have studied the kinking mechanism rather than the structure and corresponding geometrical features of the kinks. Here, we have investigated the relationship between the turning angles and the structure (down to atomic level) of KSiNWs grown by VSL from indium nanoparticles. By using transmission electron microscopy, we have characterized the transition regions between different segments of KSiNWs of various crystallographic orientations. We have found that most turning angles can be viewed as rich combinations of different types of {111} coherent twins that coexist within the transition regions between different segments of KSiNWs. CrystEngCommThis journal is