Advanced design of electrodeposited copper foil: Modulating grain growth and microstructure to achieve ultrahigh mechanical properties

The increasing demand for lithium-ion batteries (LIBs) with high energy densities and long cycle lifetimes places stringent requirements on the copper foil used as a negative current collector. Although copper foil meeting these requirements can potentially be fabricated by additives, this approach does not enable breakthrough performance improvements because of poor stability, insufficient synergistic effects, and other issues of the conventional additives in the plating solution. Herein, we designed two functionalized ionic liquids (1-aminopropyl-3-methylimidazolium chloride, IL-Cl and 1-aminopropyl-3-methylimidazolium bromide, IL-Br) and used them as composite additives to comprehensively regulate the properties of copper foil. Under optimal conditions (the ratio of IL-Cl to IL-Br in the composite additive is 2:1), the copper foil possesses ultrahigh mechanical properties (the tensile strength and elongation were 509.6 MPa and 12.35 %, respectively). Further structural and electrochemical assessments revealed that the developed additives modulated crystal structure growth by increasing the electrodeposited overpotential of Cu 2 + ions, and enhanced copper foil properties by inducing grain refinement and augmenting the density of Σ3 twin boundaries. The action mode of the additives on the copper foil surface (adsorption behavior) and their coordination interactions with Cu 2+ ions were examined using theoretical calculations. Thus, this work provides theoretical guidance for modulating the properties of the copper foils to satisfy the requirements of high-performance LIBs.