Abstract: This invention provides alkali ion conducting polymer electrolytes with high ionic conductivity and elastomeric properties suitable for use in high energy batteries. The polymer electrolytes are cyclic carbonate-containing polysiloxanes that can be modified with a cross linker or chain extender, and an alkali metal ion-containing material dissolved in the carbonate-containing polysiloxane. The cyclic carbonate-containing polysiloxanes may be prepared by reacting derivatized polysiloxanes with chain extending and/or crosslinking agents. The invention also provides batteries prepared by contacting an alkali metal anode with an alkali metal intercalating cathode and an alkali ion-conducting polymer electrolyte. As one example, polymers prepared from poly {3[2,3-(carbonyldioxy)propoxy]propyl]methyl siloxane, a polysiloxane with cyclic carbonate side chains, have shown promising results for battery applications.