Nonstoichiometric Molybdenum Trioxide Adjustable Energy Barrier Enabling Ultralong-Life All-Solid-State Lithium Batteries

The performance of lithium batteries is largely dependent on the ionic conductivity within robust solid electrolytes. Poly(ethylene oxide) (PEO)-based electrolytes, however, have a low lithium ionic conductivity, which limits the hop of Li+. Herein, a novel PEO-based composite electrolyte is prepared that contains nonstoichiometric transition molybdenum trioxide (MoO3–x) nanosheets as fillers to improve the ionic conductivity. The MoO3–x nanosheets containing many oxygen vacancies can cross-link with PEO chains to reduce the energy barrier of Li+ migration and the matrix crystallinity, leading to an increase in the lithium-ion transference number (up to 0.56) and a high ionic conductivity (up to 6 × 10–4 S cm–1) at 60 °C. Meanwhile, the incorporation of MoO3–x nanosheets alleviates the decomposition of the electrolyte, enhancing the tensile strength by ∼4 times compared to PEO. As a result, a LiFePO4/Li cell with PEO/LiTFSI/MoO3–x (PLM3–x) delivers an excellent rate capability, high capacity, and lifespan during high rates (2 C, ≥10 000 cycles), which demonstrates a facile yet effective strategy toward high-performance lithium batteries.