Effect of Li Powder-Coated Separator on Irreversible Behavior of SiOx-C Anode in Lithium-Ion Batteries

Lithium powder coatings on anodes have been reported to reduce the irreversible first-cycle capacity loss in silicon monoxide (SiOx) anodes. Instead of electrodes, we coated a separator with Li powder to reduce the irreversible capacity. We assembled a SiOx anode and Li cobalt oxide (LCO) cathode coin cell (CR2032) with an Li-coated separator in an argon-filled glove box. The charge capacity of the obtained separator in a cell at 0.1 C was 1502.0 mAh g−1 in the first cycle, while that of an uncoated separator was 1534.3 mAh g−1. The former also had a higher discharge capacity than the latter, 1334.2 compared to 1019.3 mAh g−1. Using electrochemical analysis it was estimated that the first cycle irreversible capacity loss ratio was 11.2% with the Li coating compared to the 33.6% capacity drop in pure SiOx cells. Morphology changes in the Li-coated separator are also observed using a scanning electron microscope. The results indicate that a uniform Li coating on a separator acts as an effective reserve layer, reducing the irreversible first-cycle capacity loss.