Plasma Enhanced Formation of Lithium Nitride As Artificial SEI Layer for Lithium Metal Batteries

Abstract

Lithium (Li) metal has been considered as one of the most promising anode materials to replace conventional graphite for Li ion battery. However, it still faces some problems such as unstable solid electrolyte interphase (SEI) and uncontrolled Li dendrites growth. Although plenty of efforts have been devoted to stabilize the interphase by employing a protective layer on the surface of Li metal and to suppress the dendrite growth, those materials usually suffer unstable chemical contact with Li metal electrode as well as low Li ion conductivity. Moreover, the fabrication procedures are quite complicated with long processing time or high cost. In order to develop a facile and controllable method to fabricate a stable and low cost Li metal anode, in this work, we report for the first time to fabricate Li3N film in situ on the Li metal surface by using N2 plasma activation technology. A unique flower-shape Li3N layer with [001] crystal orientation was obtained after N2 plasma activation. With a high Young’s modulus and high ionic conductivity, the Li3N layer enabled a fast Li ion transport channel between Li metal and liquid electrolyte. This Li3N protective layer can also blocked the direct contact between Li metal and liquid electrolyte, physically suppressing the growth of Li dendrites. As a result, the cycling life of Li symmetric cell was improved dramatically compared with the untreated bare Li metal. In the full cell configuration, the plasma activated Li3N electrode also demonstrated an enhanced capacity retention.