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 (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.