Silicon as anode material for Li-ion batteries

Silicon is considered as a promising anode material for Li-ion batteries because of its record capacity (about 4000 mAh g−1), more than ten times higher than that of graphite, which is used in commercial batteries. However, its use is severely limited, due to the important swelling of the material in the loaded (lithiated) state (more than 300%), and the instability of the solid-electrolyte interphase layer (SEI). The poor mechanical stability and chemical passivation properties make the cyclability of silicon electrodes far from being able to meet the requirements for battery systems and have motivated a wealth of studies and many proposals to circumvent these limitations. In this review, an outlook of the material research devoted to silicon electrodes for Li-ion batteries is presented, with special attention to material fundamental properties associated with various forms of silicon used in this context. The strategies associated with silicon nano-structuration and with the elaboration of composite materials, aimed at improving the electrode cyclability, are deliberately kept out of this scope. On the opposite, the interest of in situ techniques for the study of silicon electrodes is stressed, and the major results obtained using the latter techniques briefly reviewed.