Dissolution-equilibrium-driven repair of passivated copper electrode interfaces for reversible Cu plating and stripping

A nonaqueous AlCl 3 CuCl/THF electrolyte is developed for Cu metal batteries. • Undissolved CuCl particles act as a Cu⁺ reservoir via dissolution equilibrium. • Dynamic Cu⁺ supply enables sustained Cu plating on passivated surfaces. • The dominant reaction pathway shifts from Cu⁺/Cu 0 to Cu 2+ / Cu 0 during cycling. • Stable Cu cycling over 1400 h is achieved at 0.5 mA cm⁻ 2 . Aqueous copper metal batteries suffer from passivation caused by a Cu 2 O layer that blocks interfacial ion transport. Here, we develop a non-aqueous electrolyte system in which tetrahydrofuran (THF) solvent is employed to suppress Cu⁺ disproportionation, while the strong Lewis acid AlCl 3 is introduced to enhance the solubility of CuCl, thereby maintaining ionic transport in the liquid phase. At the early stage of cycling, the intrinsically low solubility of CuCl leaves residual CuCl on the separator, serving as a Cu⁺ reservoir. Despite local passivation, the dissolution equilibrium continuously supplies Cu⁺, enabling sustained deposition of fresh Cu on the passivated surface. With continued cycling, incomplete stripping of Cu gradually covers passivation layer, leading to gradual restoration of the Cu electrode, thereby enabling stable cycling for over 1400 h at 0.5 mA cm⁻ 2 . Further characterization reveals that the low overpotential at the initial stage is dominated by the Cu +  + e⁻ → Cu 0 pathway. In the mid-to-late cycling stages, gradual depletion of Cu⁺ increases the contribution of the Cu 2+  + 2e⁻ → Cu 0 pathway, resulting in a moderate rise in overpotential. Nevertheless, due to the dynamic reconstruction of the interfacial layer, highly reversible Cu deposition/stripping is maintained throughout cycling. This work provides new insights for the design of advanced copper-based battery electrolytes. Download: Download high-res image (245KB) Download: Download full-size image