Tailored lithium metal/polymer electrolyte interface with LiTa 2 PO 8 fillers in PEO‐based composite electrolyte

The unstable Li/PEO‐based electrolyte interface in all‐solid‐state lithium metal batteries usually leads to high interfacial resistance, low Coulombic efficiency and fast lithium dendrites growth even under a low current density. The interface composition directly determines the interfacial integrity, dynamic Li + /e – transport processes and the subsequent Li + plating/stripping behavior; thus, it is of significance to regulate the interphase to have better safety and higher energy density for all‐solid‐state lithium metal batteries. Here, by incorporation of Li + conducting LiTa 2 PO 8 fillers in PEO‐based polymer electrolyte, the reaction of LiTa 2 PO 8 (LTPO) particles with Li metal at the Li/polymer electrolyte interface generates an electronic conducting interphase and homogenizes the electric field for Li + deposition, suppressing the lithium dendrites growth. We obtain a hybrid composite electrolyte with high ionic conductivity of 1.1 × 10 –4 S·cm −1 at 35 °C and an excellent interface stability with a stable cycling life of over 600 h at a current density of 0.4 mA·cm −2 in symmetric Li/Li cell. All‐solid‐state lithium metal batteries with PEO–LiTFSI–10LTPO electrolytes deliver very stable cycling and high efficiencies.