Improvements in Li deposition and stripping induced by Cu (111) nanotwinned columnar grains

Abstract

How to depress the dendrite growth, promote the coulombic efficiency, and improve the cycling stability of Li plating/stripping on Cu foils is a strict challenge in the lithium metal-free batteries (LMfBs). Here, the Cu substrates with the (111)-preferred orientation and the (111)-nanotwinned lamella grains are compared for the performance of Li deposition/stripping in 1 M lithium hexafluorophosphate/ethylene carbonate-dimethyl carbonate (LiPF6/EC-DMC with EC:DMC=50:50 vol.%). The presence of twin boundaries in the Cu foil does decrease the total interfacial energy of the copper surface, favoring the formation of the LiF-amorphous matrix solid electrolyte interphase (SEI) to provide fast Li-ion pathways and inducing the growth of UPD (underpotential deposition) Li. As a result, the (111)-nanotwinned copper foil significantly reduces the nucleation overpotential of Li plating, uniforms the lithium deposit, improves the coulombic efficiency, and ameliorates the cycling stability of Li plating/stripping. The microstructures of Cu foils with the (111)-preferred orientation and the (111)-nanotwinned lamella grains have been confirmed by the X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM).