Enlarging potential window and enhancing stability of poly(ethylene oxide)-based composite solid electrolyte via succinonitrile additive for advanced solid lithium batteries

Solid polymer electrolytes such as poly(ethylene oxide) (PEO) are desirable in lithium batteries due to their high safety and excellent flexibility. However, low ionic conductivity and electrochemical stability of PEO hamper their applications. In this work, succinonitrile (SN) is added to the composite solid electrolyte (CSE) composed of PEO matrix and [Formula: see text]La 3 [Formula: see text][Formula: see text][Formula: see text] filler to improve its ionic conductivity and electrochemical stability, thereby matching with ternary cathode materials. The results reveal that the ionic conductivity of CSE at 55 ∘ C can be increased by more than one order of magnitude with the addition of SN. And the CSE membrane containing 6 wt.% SN (CSE-6) exhibits the best electrochemical stability, which has improved the electrochemical window from 4.83 to 5.26 V. Compared with blank sample without the additive, the specific capacity of [Formula: see text][Formula: see text][Formula: see text]O 2 /CSE-6/Li is increased from 15.6 to 154 mAh ⋅ g[Formula: see text], and exhibits relatively optimal cyclic stability in a range of solid-state batteries with different SN contents. It is expected that the results of this study will provide a reference for the application of PEO-based CSEs in high-voltage solid lithium batteries.