Organic/inorganic composites have been considered as promising electrolyte candidates in all solid-state lithium batteries. Aiming at improving the conductivity significantly by increasing the frequently-used 0D or 1D ceramic nano-fillers to high content is unsuccessful due to the particle tendency to agglomeration. What's worse, the loose contact between the solid electrolyte and solid electrodes is much of a serious barrier to the performance and thus to the application of all solid-state lithium batteries. Herein, self-supported 3D porous Li_6.4Al_0.1La₃Zr_1.7Ta_0.3O₁₂ frameworks are employed to provide percolated fast Li⁺ conductive pathway while in-situ polymerization of poly(ethylene glycol) methyl ether acrylate can integrate the loose solid-solid interface and reduce the interfacial resistance efficiently. Inspiringly, the Li⁺ conductivity of the composite exhibits 1.9×10^-4 S·cm^-1 at room temperature. The interfacial resistance in Li-Li batteries decreases significantly from 1540 to 449 Ω·cm ², rendering good capacity and cyclability of the 4.3 V (vs. Li⁺/Li) LiCoO₂|Li all solid-state lithium battery.