Flexible, high-temperature-resistant, highly conductive, and porous siloxane-based single-ion conducting electrolyte membranes for safe and dendrite-free lithium-metal batteries

High-temperature-resistant polymer electrolyte membranes with satisfactory Li-ion transference number (tLi+) and ionic conductivity is desirable for the application in safe and dendrite-proof lithium metal batteries (LMBs). In this study, siloxane-based single-ion conducting polymer electrolyte (SIPE) membranes with high porosity are fabricated by in-situ sol-gel and non-solvent induced phase separation methods. Benefiting from the well-designed three-dimensional interpenetrating polymer network, the thermal and dimensional ability of the as-developed membranes are significantly enhanced. In addition, the porous structure enabling a high liquid electrolyte uptake (468.6%) combines with the intrinsic nature of SIPE for the membranes, giving rise to much higher ionic conductivity of 1.72 × 10−3 S cm−1 and tLi+ of 0.72 compared to commercial polypropylene (PP) separators (3.56 × 10−4 S cm−1 and 0.33) at 25 °C. Such excellent electrochemical properties are beneficial to inhibiting the Li dendrites and impeding short-circuiting of batteries. As expected, the Li/Li symmetrical cells show a stable galvanostatic Li plating/stripping cycling performance with a low overpotential of more than 400 h at 2 mA cm−2. Remarkably, the LiFePO4/Li batteries using the membranes exhibit impressive rate capacity and superior cycling ability compared to the batteries assembled with PP separators. This novel design and exciting results offer tremendous potential in the construction of dendrite-free LMBs with high safety.