SiAg film by magnetron sputtering for high reversible lithium ion storage anodes

Abstract

Abstract In the present work we proposed a new strategy to produce Si electrodes with high capacity retention. Si film with 20% at. Ag content is deposited by magnetron sputtering. The galvanostatic test result shows that the electrode delivers 1825 mAh g−1 initially with 95% Coulombic efficiency and retains 96% of its initial discharge capacity after 60 cycles when cycled between 0.2–1.2 V. The same SiAg electrode performs 2500 mAh g−1 as the first discharge capacity and quickly fails after 20 cycles when cycled between 0.005–1.2 V. Cyclic voltammetry and electrochemical impedance spectroscopy show that by proper selection of lower cut-off voltage (0.2 V), Ag particles remain inactive versus Li in cycling, which induces the distribution of finely dispersed active (Si) element with an inactive component (Ag) in the electrode. The results of the galvanostatic test at different lower cut-off potentials exhibit outstanding properties. The SiAg electrodes are highly dependent on the potential range since high reversibility and good capacity retention are mostly related to the presence of Ag, which decreases the polarization of anode when its reaction with lithium is restricted.