Electrodeposited Lithiophilic Zn Thin Film on the Current Collector for Improved Cyclability of Anode-Free Lithium Metal Battery

Abstract

Anode-free lithium metal batteries (AFMBs) are recently presented as the new generation of Li metal batteries benefiting high gravimetric and volumetric energy densities due to the zero excess lithium. However, poor electrochemical stability and maximum cyclability of around 40-50 cycles due to the zero excess Lithium prevent the AFLMBs to be functional1. Here, lithiophilic electrodeposited Zn thin film on the current collector is reported in order to decrease the lithium nucleation overpotential and improve the plating/stripping process during alloying and dealloying. Moreover, columbic efficiency is increased by applying more zinc coated on the cupper current collector and by providing a more hospitable site for Li nuclei to plate2. Due to the alloy formation of Li-Zn, more conformal Li growth on the current collector is provided and homogeneous Li distribution and smooth morphology are observed by SEM images. The cells in different zinc thin layer coating are cycled with different current densities as well as long-term cycling by galvanostatic cycling charge-discharge cycling. As a result, increasing the thin film thickness up to 1 micron significantly enhances the electrochemical stability of the cells such as higher columbic efficiency and cyclability, lower Li nucleation overpotential. Finally, the Li-ion chemical diffusion coefficients DLi, are evaluated by galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS) and the results are compared to each other3.References Maddukuri, S. et al. On the challenge of large energy storage by electrochemical devices. Electrochim Acta 354, 136771 (2020).Merso, S. K. et al. An in-situ formed bifunctional layer for suppressing Li dendrite growth and stabilizing the solid electrolyte interphase layer of anode free lithium metal batteries. J Energy Storage 56, 105955 (2022).Xie, J. et al. Determination of Li-ion diffusion coefficient in amorphous Zn and ZnO thin films prepared by radio frequency magnetron sputtering. Thin Solid Films 519, 3373–3377 (2011).