Toward ambient temperature operation with all-solid-state lithium metal batteries with a sp3 boron-based solid single ion conducting polymer electrolyte

•Charge delocalized sp3 boron based single ion conducting polymer electrolyte was prepared.•PEO/SIPE based all-solid-state lithium ion battery displays battery operation at 50 °C.•The PEO/SIPE blended membrane presumably presented two Li+pathways.

The ionic conductivity decay problem of poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) when increase the lithium salt of the SPEs up to high concentration is here functionally overcome by the incorporation of a charge delocalized sp3 boron based single ion conducting polymer electrolyte (SIPE) with poly(ethylene oxide) to fabricate solid-state sp3 boron based SIPE membranes (S-BSMs). By characterizations, particularly differential scanning calorimeter (DSC) and ionic conductivity studies, the fabricated S-BSMs showed decreased melting points and increased ionic conductivity as steadily increase the content of sp3 boron based SIPE, which significantly improved the low temperature performance of the all-solid-state lithium batteries. The fabricated Li | S-BSMs | LiFePO4 cells exhibit highly electrochemical stability and excellent cycling at temperature below melting point of PEO, which has never been reported so far for SIPEs based all-solid-state lithium batteries.