Regulating lithium deposition via electropolymerization of acrylonitrile in rechargeable lithium metal batteries

We report acrylonitrile (AN) as an effective additive in carbonate-based electrolytes to enable uniform and dense lithium (Li) deposition and to improve the coulombic efficiency of Li metal anode. Our electrochemical, spectroscopic, and theoretical study reveal that AN is cathodically electropolymerized on the Li surface prior to the electrochemical decomposition of the electrolyte during Li deposition. The resultant polyacrylonitrile artificial solid electrolyte interphase enables uniform nucleation and growth of Li deposition with significantly reduced side reactions. The effectiveness of the AN additive is demonstrated in 0.4 Ah Li||LiNi0.6Mn0.2Co0.2O2 pouch cells (using 50-μm Li anode, 3 mAh cm−2 cathode areal capacity, and 4 g Ah−1 electrolyte) with excellent cycle stability under realistic charge-discharge condition.