An ultrathin Li-doped perovskite SEI film with high Li ion flux for a fast charging lithium metal battery†

Developing an artificial solid electrolyte interphase (SEI) with high Li ion flux is vital to improve the cycling stability of lithium metal batteries, especially under a high rate. In this work, a novel artificial SEI film was prepared via in situ deposition of a lithium-doped cesium lead chloride perovskite (Li–CsPbCl₃). Benefiting from its ultra-high thickness (0.45 μm), high mechanical modulus (5.9 GPa), high lithium-ion migration number (0.57), and unique highly oriented framework, the Li–CsPbCl₃ SEI film could promote the rapid transport and uniform deposition of lithium ions, enhancing the stability of lithium deposition and stripping. As a result, Li/Li symmetric cells based on the Li–CsPbCl₃ protective film could cycle stably for 1300 hours under high current density of 10 mA cm⁻². In addition, the Li/LiFePO₄ battery using the Li–CsPbCl₃ SEI film showed an impressive cycling stability with a capacity retention rate of up to 91.4% after 230 cycles at a high current rate of 3C.