An air-stable and waterproof lithium metal anode enabled by wax composite packaging

The reviving use of lithium metal anode (LMA) is one of the most promising ways to upgrade the energy density of lithium ion batteries. In the roadmap towards the real use, besides the formation of the dendrite, various adverse reactions due to the high activity of LMA when exposed to air or the electrolyte limit its practical applications. Learning from the packaging technology in electronic industry, we propose a wax-based coating compositing with the ion conducting poly (ethylene oxide) by a simple dip-coating technology and the prepared LMA is featured with an air-stable and waterproof surface. The LMA thus remains stable for 24 h in ambient air even with the relative humidity of 70% while retaining about 85% its electrochemical capacity. More importantly, the LMA is accessible to water and when dipping in water, no obvious adverse reactions or capacity decay is observed. With the composite coating, a steady cycling performance for 500 h in symmetrical cells and a low capacity decay rate of 0.075% per cycle after 300 cycles in lithium-sulfur batteries assembled with the packaged anode have been achieved. This work demonstrates a very simple and effective LMA package technology which is easily scalable and is very promising for speeding up the industrialization of lithium-sulfur batteries and shows potentials for the large-scale production of air-sensitive electrode materials not limited to LMAs.