Surface Coating Layer on Li Metal for Increased Cycle Stability of Li-O2 Batteries

The effects of polymer coating on the cycle stability of Li-O2 batteries were investigated. Capacity fading is much higher with increasing Li utilization; however, it was found that coating the Li metal with poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) highly and effectively increased the cycle stability of a Li-O2 battery. This indicates that the coating may prevent shape changes of the metal during discharge and charge cycles. Impedance analysis suggested that the interfacial resistance on the anode compartment explained the low cycle stability in cells containing pristine Li. The PVdF-HFP coating suppressed this interfacial resistance during discharge-charge cycles performed at current densities exceeding 0.1 mA/cm2. Microscopy studies showed that lithium morphology deposited on the polymer coated electrode showed suppressed needle-like dendrite formation explaining the increase in the cycle stability of Li-O2 batteries.