Effect of chromium coating on nanosilicon anodes for lithium ion batteries

The effects of a Cr coating on Si nanopowder electrodes have been researched in order to improve the electrochemical characteristics of Si anodes for use in Li-ion batteries. Cr was coated onto Si nanopowder electrodes by sputtering, and the electrodes were then analyzed using scanning electron microscopy, high-resolution transmission electron microscopy, and an electron probe microanalyzer. Cr-coated Si anode/Li-foil half-cells (CR2032) were then assembled in an Ar-filled glove box. The discharge capacity of the Cr-coated Si anode cell was found to be 2561 mAh·g^{- 1} at the 1st cycle; this value was greater than the discharge capacity of a pure Si nanoelectrode cell (2240 mAh·g^{- 1}). Further, the Cr-coated Si anode cell was stable for more than 50 cycles and showed a discharge capacity of 1061 mAh·g^{- 1} at the 50th cycle and a 0.1 C-rate. Thus, the 50-cycle capacity retention for this cell was 41.4%, whereas that of the cell with uncoated electrodes was 19.5%. The improved electrochemical characteristics of the Cr-coated Si anode cell were explained using impedance analysis and SEM observations. Since Cr has high electrical conductivity and mechanical stability, the Cr coating enhanced the electrical conductivity and acted as a buffering layer for the nano-Si electrode.