Cycleability Enhancement of Li Metal Anode by Primary Charge with Electrolyte Additives

Abstract

Li metal was charged on a substrate in binary electrolytes, propylene carbonate (PC) with dimethyl carbonate (PC-DMC) or ethylene carbonate with DMC (EC-DMC), containing Li bis(perfluoroethylsulfonyl)imide [Li(C₂F₅SO₂)₂N] in the presence of metal iodide additives, magnesium iodide (MgI₂) or aluminum iodide (AlI₃). This electrodeposited Li with the additives showed a high cycleability even after it was transferred to the corresponding electrolyte without any additives; its cycleability was nearly equal to or, in some cases, higher than that of Li metal cycled all along with the corresponding additive. This means that the primary Li charge in the presence of the additives can provide a Li metal anode with an enhanced cycleability no longer with the need for the additives during the subsequent cycles. Ac impedance analysis revealed that the interfacial resistance of Li anode prepared by the leadoff charge with the additives remains fairly low even in the subsequent cycles.