Lithium Nitride-rich Li Protection Layer via Facile Lewis Acid–Base Reaction for Li Metal Batteries

Abstract

In this study, we present a scalable approach for forming a lithium nitride (Li₃N)-rich protection layer on Li metal, enabling practical applications for high-energy-density lithium metal (Li) batteries. This protection layer is developed through a simple Lewis acid–base reaction involving the direct contact of Li metal with xylylenediamine. This method employs a two-step solution coating process. First, the native oxide layer on the Li surface is removed via chemical polishing. Then, the Li₃N protection layer is coated onto the polished Li metal (Li₃N@Li). This ensures an effective chemical reaction between Li metal and xylylenediamine, leading to a robust protection layer. The Li nucleation and growth behavior of Li₃N@Li shows a dendrite-free morphology with dense and compact properties. Electrochemical evaluations in Li||Li symmetric cells demonstrate dendrite-free Li deposition at 0.5 mA cm^–2 for a capacity of 2 mA h cm^–2. Additionally, pairing the protected Li anode with a LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode achieves an areal capacity of 5 mA h cm^–2. The resulting Li||NCM full cells exhibit stable cycling stability with 78.5% capacity retention and an average Coulombic efficiency of 99.8% for over 100 cycles. This work provides insights into the practical realization of high-energy-density Li metal batteries, offering a scalable solution for developing protection layers on Li metal anodes.