Polysiloxane-Based Single-Ion Conducting Polymer Blend Electrolyte Comprising Small-Molecule Organic Carbonates for High-Energy and High-Power Lithium-Metal Batteries

Single-ion conducting polymer electrolytes are considered particularly attractive for realizing high-performance solid-state lithium-metal batteries. Herein, a polysiloxane-based single-ion conductor (PSiO) is investigated. The synthesis is performed via a simple thiol-ene reaction, yielding flexible and self-standing polymer electrolyte membranes (PSiOM) when blended with poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP). When incorporating 57 wt% of organic carbonates, these polymer membranes provide a Li${}^{+}$ conductivity of >0.4 mS cm${}^{-1}$ at 20 °C and a wide electrochemical stability window of more than 4.8 V. This excellent electrochemical stability allows for the highly reversible cycling of symmetric Li||Li cells as well as high-energy Li||LiNi${}_{0.6}$Mn${}_{0.2}$Co${}_{0.2}$O${}_2$2 (NMC${}_{622}$) and Li||LiNi${}_{0.8}$Mn${}_{0.1}$Co${}_{0.1}$O${}_2$ (NMC${}_{811}$) cells for several hundred cycles at relatively high discharge and charge rates. Remarkably, Li||NMC${}_{811}$ cells with high mass loading cathodes provide more than 76% capacity retention at a high current density of 1.44 mA cm${}^{-2}$, thus rendering this polymer electrolyte suitable for high-performance battery applications.