In situ construction of polyether-based composite electrolyte with bi-phase ion conductivity and stable electrolyte/electrode interphase for solid-state lithium metal batteries

Abstract

Polyether-based composite electrolytes exhibit great promise to bridge the gap between solid polymer electrolytes (SPEs) and high-energy solid-state Li metal batteries. However, the practical application of polyether electrolytes is still hindered by their poor ionic conductivity and low oxidation potential. Herein, a topochemistry-driven polyether-based composite electrolyte is constructed in situ, by the cation polymerization of 1,3-dioxolane (DOL) to obtain poly(1,3-dioxolane) (PDOL) in a three-dimensional (3D) La_0.56Li_0.33TiO₃ nanofiber (LLTO NF) skeleton, with a chemically stable interface and strong-coupled ionic conductivity. The spontaneous polymerization reaction results in the formation of a unique polymeric CH₂–CH₂–O–CH₂–O– amorphous structure of PDOL, with a wide operation voltage (5.5 V) and an intimate interface within the LLTO NF skeleton. The continuous one-dimensional (1D) LLTO NFs and polymer chains act as bi-phase ion transport channels, enabling an improved conduction of 6.6 × 10⁻⁴ S cm⁻¹. Furthermore, the LiF and Al-complex films derived from the solid electrolyte interphase (SEI) can redistribute the ion flux and ensure the structural stability of the Li anode. Thus, the polyether-based composite electrolyte achieves a remarkable cyclability (over 900 h at 0.1 mA cm⁻²) and satisfactory capacity retention (70.7% over 350 cycles). This polymer composite electrolyte design offers a unique perspective for linking in situ topochemistry design with safe and high-energy solid batteries.