Stabilizing the Solid Electrolyte Interphase with Phenyl Isothiocyanate for Long-Cycle Lithium Metal Batteries

Abstract

Lithium metal batteries possess great potential for portable electronic devices as a next-generation secondary battery owing to their high specific capacity and energy density. However, their cycling stability is hindered by the formation of an unstable solid-electrolyte interphase between the electrolyte and the Li anode, leading to poor cycling performance. Herein, phenyl isothiocyanate (PITC) has been introduced as an additive in a propylene carbonate (PC) electrolyte to stabilize the solid-electrolyte interphase layer on the Li metal anode. The addition of PITC significantly improves the electrochemical performance of Li||Cu half-cells, exhibiting a coulombic efficiency of 82%, and enhances cycling stability in Li||Li symmetric cells, with low polarization and a uniform solid-electrolyte interface, as confirmed by scanning electron microscopy (SEM) analysis. In Li||LFP full cells, the optimized electrolyte demonstrated excellent cycling stability, maintaining a discharge capacity of 150 mAh g−1 after 650 cycles at a 1C rate. These results verify that PITC is an effective additive for PC-based electrolytes, enhancing the longevity and stability of lithium metal batteries.