For the next generation of safe and high energy rechargeable lithium metal batteries, we introduce nano structured polymer particles of asymmetric miktoarm star :copolymers. as, additives to liquid electrolytes for use as solid polymer electrolytes (SPE). The mechanical properties of the resulting SPEs are dramatically improved compared to the pure liquid electrolyte (the elastic modulus increased by up to 8 orders of magnitude), while the ionic conductivity was maintained: close to that of the pure liquid electrolyte. In particular, the addition of 44 wt.% miktoarm stars, composed of ion conducting poly(ethylene oxide), PEO, arms that complement stiff insulating polystyrene arms, PS ((PS),;(PEO), where n = 30 the number of arms), in a low molecular weight PEO doped with lithium bis(trifluorornethane)sulfonamide (LiTFSI) resulted in SPEs with a shear modulus of G' similar to 0.1 GPa and ion conductivity sigma similar to 10(-4) S/cm. The SPEs show a strong decoupling, between the mechanical behavior and the ionic conductivity as G' remains fairly constant for temperatures up to the glass transition temperature of the PS blocks, while the conductivity monotonically increases reaching sigma similar to 10(-2) S/cm. Our strategy offers tremendous potential for the design of all-polymer nanostructured materials with optimized mechanical, properties, and ionic conductivity over a wide temperature window for advanced lithium battery technology.