Towards durable practical lithium–metal batteries: advancing the feasibility of poly-DOL-based quasi-solid-state electrolytes via a novel nitrate-based additive

Abstract

The in situ polymerization of quasi-solid-state electrolytes (QSSEs) is emerging as a promising approach for the development of scalable, safe, and high-performance quasi-solid-state lithium–metal batteries. In this context, poly-DOL-based electrolytes are particularly attractive due to their wide electrochemical window and strong compatibility with lithium metal. To enhance the stability of lithium metal, LiNO₃ is frequently added as it creates an effective, Li₃N-rich solid electrolyte interphase on the surface of the lithium metal anode. However, LiNO₃ prevents DOL's ring-opening polymerization, making the two compounds incompatible. To address this issue, this work develops triethylene glycol dinitrate (TEGDN), a novel nitrate-based additive, to replace LiNO₃. Like LiNO₃, TEGDN forms a dense, nitrogen-rich solid electrolyte interphase on the surface of lithium, protecting it from parasitic reactions. However, unlike LiNO₃, TEGDN does not interfere with the polymerization of DOL, allowing the fabrication of a highly effective electrolyte that delivers an ionic conductivity of 2.87 mS cm⁻¹ and an oxidation stability potential of 4.28 V at room temperature. To demonstrate the viability of this approach, a Li|LiFePO₄ coin-type cell cycling stably more than 2000 times at 1C is fabricated. In addition, a 1.7 A h pouch-type lithium-sulfur cell with an initial specific energy of 304 W h kg⁻¹ and a capacity retention of 79.9% after 50 cycles is prepared. In short, the present study proposed a new additive to resolve poly-DOL and LiNO₃ incompatibility for the first time and developed in situ polymerized quasi-solid-state batteries that exhibit remarkable capacity and stability by forming an N-rich solid electrolyte interphase.