Li-ion batteries (LIBs) represent the most sophisticated electrochemical energy storage technology. Nevertheless, they still suffer from safety issues and practical drawbacks related to the use of toxic and flammable liquid electrolytes. Thus, polymer-based solid electrolytes may be a suitable option to fulfill the safety and energy density requirements, even though the lack of high ionic conductivity at 25 °C (10⁻⁸–10⁻⁷ S cm⁻¹) hinders their performance. To overcome these drawbacks, herein, we present an all-solid-state Li-metal full cell based on a three-component solid poly(ethylene oxide)/lithium bis(trifluoromethanesulfonyl) imide/titanium dioxide composite electrolyte that outclasses the conventional poly(ethylene oxide)-based solid electrolytes. Moreover, the cell features are enhanced by the combination of the solid electrolyte with a self-standing LiFePO₄ catholyte fabricated through an innovative, simple and easily scalable approach. The structural, morphological and compositional properties of this system are characterized, and the results show that the electrochemical performance of the solid composite electrolyte can be considerably improved by tuning the concentration and morphology of TiO₂. Additionally, tests performed with the self-standing LiFePO₄ catholyte underline a good cyclability of the system, thus confirming the beneficial effects provided by the novel manufacturing path used for the preparation of self-standing electrodes.