Concerning the safety aspects of Li+ ion batteries, an epoxy-reinforced thin ceramic film (ERTCF) is prepared by firing and sintering a slurry-casted com-posite powder film. The ERTCF is composed of Li+ ion conduction channels and is made of high amounts of sintered ceramic Li1+xTi2-xAlx(PO4)3 (LATP) and epoxy polymer with enhanced mechanical properties for solid-state bat-teries. The 2D and 3D characterizations are conducted not only for showing continuous Li+ ion channels thorough LATP ceramic channels with over 10-4 S cm−1 of ionic conductivity but also to investigate small amounts of epoxy polymer with enhanced mechanical properties. Solid-state Li+ ion cells are fabricated using the ERTCF and they show initial charge–discharge capac-ities of 139/133 mAh g−1. Furthermore, the scope of the ERTCF is expanded to high-voltage (>8 V) solid-state Li+ ion batteries through a bipolar stacked cell design. Hence, it is expected that the present investigation will significantly contribute in the preparation of the next generation reinforced thin ceramic film electrolytes for high-voltage solid-state batteries.