Engineering the Li-ion flux and interfacial chemistry toward a stable Li metal anode via a simple separator coating strategy

Abstract

Due to its remarkably high specific capacity of 3860 mA h g⁻¹ and low reduction potential (−3.04 V vs. SHE), lithium metal has been identified as an ideal anode candidate for high-energy density lithium-ion cells. However, the growth of lithium dendrites caused by the deposition of lithium metal can affect the charge and discharge behavior of a cell and lead to short circuit, which is a safety concern and hinders its practical applications. Here, we prepare a composite separator polypropylene-Li_1+xAl_xTi_2−x(PO₄)₃-indium tin oxide (PP–LATP–ITO) via a simple slurry coating method. The coating of LATP-ITO demonstrates unique advantages of Li-ion deposition as well as interfacial chemistry. Firstly, lithiophilic PP-ITO helps to reduce the energy barrier for Li deposition. In addition, the three-dimensional ion channels can regulate the transport of lithium ions and induce uniform Li metal plating and stripping. Furthermore, the in situ formed interface comprising of a Li–In alloy, Li₃PO₄ and LiF enables stable interfacial chemistry. As a result, compared with the PP separators, the voltage stability of the composite separators in Li–Li symmetric cells is greatly improved during the charge and discharge cycling. In addition, LCO/Li cells with the composite separator PP–LATP–ITO exhibit a higher specific capacity (140 mA h g⁻¹) and good capacity maintenance during cycling. This work proposes a separator coating strategy that can inhibit dendrite formation and stabilize the lithium metal interface.