Electrochemical Characteristics of Diamond-Like Carbon/Cr Double-Layer Coating on Silicon Monoxide-Graphite Composite Anode for Li-Ion Batteries

The electrochemical behavior of a SiOx–graphite composite anode with a diamond-like carbon (DLC)–Cr double-layer coating and employed in a Li-ion secondary cell was studied to determine whether the coating improved the electrochemical characteristics of SiOx. The DLC layer was coated through plasma-enhanced chemical vapor deposition, and the Cr layer was formed by physical vapor deposition. The formation of the coating layer was confirmed by transmission electron microscopy, Raman spectroscopy, and electron microprobe analysis. The charge capacity of a coated-anode cell (591 mA·h·g−1) was found to be higher than that of a bare-anode cell (517 mA·h·g−1) after the 1st cycle. Further, the 50th-cycle capacity retention of the coated-anode cell (83%) was higher than that of the bare-anode cell (59%) at a 0.5 C-rate. The electrochemical characteristics of the coated-anode cell were investigated by impedance analysis, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. Because of good mechanical properties of the DLC-Cr coatings and high electrical conductivity of Cr, double layer coating enhances the electrochemical behavior of SiOx as a supplementary coating material.