Plasticized and crosslinked versions of poly(lithium oligoetherato mono-oxalato borate), called lithium polyMOBs, have been studied. In heavily plasticized forms of both polyMOB, and a LiBH4-crosslinked polyMOB, the ionic conductivity reaches 10−3 S cm−1 at room temperature while single ion conductivity is automatically retained. The electrochemical stability window is up to 5 V, for both stainless steel (SS) electrodes. The plasticized forms are fluid, not a gel, due to the low molecular weight of the polyanions. Freestanding gel electrolytes with high single ionic conductivity of 10−4 S cm−1 at ambient can be obtained by incorporation of high molecular weight poly(methyl methacrylate) (PMMA) into the solution. Electrochemical cells using these electrolytes will not suffer from concentration polarization.