Overcoming the electrolyte-derived interphase through sequential reactions for stable lithium metal anode

Abstract

Lithium metal batteries hold significant promise for achieving energy densities beyond 400 Wh kg–1. However, the uncontrolled decomposition of solvent molecules and salt anions leads to a heterogeneous electrolyte-derived solid electrolyte interphase (SEI), resulting in nonuniform Li-ion diffusion and uncontrolled dendrite growth, which severely compromises cycling stability. Herein, we propose a sequential reactions strategy that enables precise SEI regulation through finely controlled chemical and electrochemical processes, overcoming the limitations of conventional electrolyte-driven decomposition. A reactive polymer, sulfurized polyethylenimine, is designed to chemically induce the formation of an Li2S layer on the lithium metal surface, ensuring homogeneous Li-ion transport. Subsequently, a Li2S/Li3N intermediate layer, generated by electrochemical reactions, accelerates Li-ion migration. Shielded by the unreacted organic layer, the tailored SEI maintains robust structural integrity. Even under lean electrolyte (1.35 g Ah–1) and high areal capacity (6.0 mAh cm–2), a 3.4 Ah LiNi0.8Co0.1Mn0.1O2||Li pouch cell employing this well-controlled SEI achieves an ultrahigh specific energy of 480.5 Wh kg–1 with an impressive capacity retention of 85.9% after 100 cycles. These findings provide a new paradigm for rational SEI design via the regulation of sequential reactions, offering valuable insights into stabilizing Li metal anodes under practical conditions.