2, Iljin Electric Co. Ltd, Seoul, , Korea (the Republic of)
An increasing demand for high-performance rechargeable batteries for various applications including portable electronic devices, electric vehicles and energy storage systems requires large improvements in the energy densities of the current lithium-ion batteries. Graphite has been widely used as an active anode material in commercial lithium-ion batteries due to its low cost and long cycle life. However, the available capacity of graphite is limited to around 350 mAh g-1, which is close to its theoretical capacity of 372 mAh g-1. In order to improve the energy density of lithium-ion batteries, silicon materials have been actively studied as attractive anode materials due to their high theoretical capacities, low reduction potentials and low cost. However, silicon materials suffer from substantial volume changes during repeated cycling, which are highly detrimental to the cycling stability of lithium-ion batteries. The mechanical stresses caused by repeated changes in volume can fracture the electrode, which causes poor electrical contacts between the active materials, electronic conductors and current collector. As a result, a serious capacity decline occurs during repeated cycling.
In this study, we synthesized silicon alloys composed of silicon nanoparticles embedded in inert metal matrix phases, and investigate their electrochemical performance. The resulting silicon alloy particles were coated by different kinds of polymer materials or conductive carbon to a form stable interfacial layer and achieve good capacity retention. The interfacial studies and cycling tests were carried out by electrochemical impedance spectroscopy, XPS, FE-SEM, HR-TEM and galvanostatic charge/discharge cycles. Detailed characterization of surface-modified silicon alloy materials along with their electrochemical performance will be presented