Abstract: Mn-doped amorphous LiPON solid electrolyte films has been deposited by magnetron sputtering, and the effect of Mn on the electrochemical performance of LiPON electrolyte was systematically studied in this work. The results show that this electrolyte film effectively enhanced the network cross-linked structure and facilitated the migration of Li⁺ with an ionic conductivity as high as 5.00 × 10⁻⁶ S/cm. The decomposition voltage analyzed by CV and LSV is above 5 V, and the ion migration number reaches 0.999. The doping of Mn-ions increases the intrinsic work function of LiPON and reduces the VCPD between LiPON and LiCoO₂, beneficial to enhance the electrochemical stability of the contact interface. All-solid-state thin film lithium battery (TFLB) with the structure of LiCoO₂/LiPON–Mn/Li have been fabricated by Mn-doped LiPON electrolyte layer, showing a high cycle and rate performance. We suggested that the Mn-doping is an effective approach to enhance the electrochemical performance of LiPON electrolyte, and lower the Li⁺ migration barrier at the LiCoO₂/LiPON interface.