Solid polymer electrolytes (SPEs) based on polysiloxane having ion-conducting poly(ethylene oxide) (PEO) groups crosslinked with modified gallic acid from natural resources are prepared by thiol-ene click reaction for all-solid-state lithium metal battery applications. The effects of composition and crosslinking density on physical and electrochemical properties of the SPEs are systematically studied. The SPEs are found to be thermally and mechanically stable even at elevated temperature due to stable crosslinked polymer networks by modified gallic acid crosslinker. Furthermore, ionic conductivity of SPE based on 80 mol% of PEO group and 20 mol% of modified gallic acid crosslinker is found to be comparable to that of polymer electrolyte having a wax state. The formation and growth of lithium dendrites are effectively suppressed by the SPE due to its good compatibility with lithium metal anode and mechanical suppression effect. All-solid-state lithium metal battery is fabricated with SPE-integrated cathode and it is found that SPE exhibits superior cycle performance to conventional liquid electrolyte/separator system at 60 degrees C that is attributed to the good thermal stability and lithium dendrite-suppressing ability of the SPE. (C) 2017 Elsevier Ltd. All rights reserved.