A surface chemistry-regulated gradient multi-component solid electrolyte interphase for a 460 W h kg−1 lithium metal pouch cell

Abstract

Lithium (Li) metal is an ideal anode for high energy density rechargeable Li batteries. However, parasitic reactions and an uneven native oxide layer on the surface lead to uncontrollable Li deposition and dendrite growth, significantly restricting its practical application. Here, we introduce a simple and scalable surface chemical approach involving spray casting of dilute 2,2-difluoro-2-(fluorosulfonyl)acetic acid (DFFSA) solution onto the Li surface, meticulously regulating ion transfer and improving interface stability to achieve stable cycling of the Li anode. The spontaneous in situ reaction between Li and DFFSA eliminates the uneven native oxide layer, forming an organic fluorinated carboxylate lithium salt on the outermost surface and a graded inorganic layer composed of LiF, Li₂S, and Li₂SO₃ inside, resulting in a multi-component artificial solid electrolyte interphase (SEI). This multi-component SEI, as evidenced by visualization techniques and computational methods, exhibits enhanced Li affinity and wettability, enabling rapid lithium-ion transport and dendrite-free, uniform lithium deposition. Consequently, the modified Li||LiCoO₂ full cell retains 77.85% capacity after 1200 cycles in carbonate-based electrolytes. A 461.6 W h kg⁻¹ pouch cell with a capacity of 5.49 A h, a low N/P ratio of 1.28 and a lean electrolyte of 1.6 g A h⁻¹, demonstrates an impressive capacity retention of 84.7% after 100 cycles at 0.5C. This work provides a simple and promising surface engineering strategy and enlightens the multi-component SEI design for promoting the practical application of high energy density Li metal batteries.