Star block copolymer electrolyte with lithium ion conducting phase are investigated in the present work to assess the influence of this complex architecture compared to the linear one, on both, bulk morphology and ionic conductivity. For that purpose, the controlled synthesis of a series of poly(styrene-co-benzyl methacrylate)-b-poly[oligo(ethylene glycol) methyl ether acrylate] (P(S-co- BzMA)-b-POEGA) block copolymers (BCPs) by RAFT polymerization was performed from either a monofunctional or a tetrafunctional chain transfer agent (CTA) containing trithiocarbonate groups. We emphasized how a small amount of styrene (6 mol-%) improved drastically the control of the RAFT polymerization of benzyl methacrylate mediated by the tetrafunctional CTA. Transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS) demonstrated a clear segregation of the BCPs in the presence of lithium salt. Interestingly, the star BCPs gave rise to highly ordered lamellar structures compared to the linear analogue. Consequently, the reduced lamellae tortuosity of self-assembled star BCPs improved the lithium conductivity by more than 8 times at 30°C for ̴ 30 wt-% of POEGA conductive phase.