In order to enhance the ionic conductivity of solid polymer electrolytes (SPEs) and their structural rigidity against lithium dendrite during lithium-ion battery (LIB) cycling, we propose porous garnet Li_6.4La₃Zr₂Al_0.2O₁₂ (LLZO), as the filler to SPEs. The porous LLZO with interlinked grains was synthesized via a resol-assisted cationic coordinative co-assembly approach. The porous structure of LLZO with high specific surface area facilitates the interaction between polymer and filler and provides sufficient entrance for Li⁺ migration into the LLZO phase. Furthermore, the interconnection of LLZO grains forms continuous inorganic pathways for fast Li⁺ migration, which avoid the multiple diffusion for Li⁺ in interface. As a result, the SPEs with porous LLZO (SPE-PL) show a high ionic conductive of 0.73 mS·cm⁻¹ at 30 °C and lithium-ion transference number of 0.40. The porous LLZO with uniformly dispersed pores also acts as an ion distributor to regulate ionic flux. The lithium-symmetrical batteries assembled with SPE-PL show a highly stable Li plating/stripping cycling for nearly 3000 h at 0.1 mA·cm⁻². The corresponding Li/LiFePO₄ batteries also exhibit excellent cyclic performance with capacity retention of 75% after nearly 500 cycles. This work brings new insights into the design of conductive fillers and the optimization of SPEs.

The aggregation of inorganic particles with high mass ratio will form a heterogeneous electric field in the solid polymer electrolytes (SPEs), which is difficult to be compatible with lithium anode, leading to inadequate ionic conductivity. Herein, a facile spray drying method is adopted to increase the mass ratio of inorganic particles and solve the aggregation problems of fillers simultaneously. The polyvinylidene fluoride (PVDF) with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) covers the surface of each Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) granules during the nebulization process, then forming flat solid electrolytes via layer-by-layer deposition. Characterized by the atomic force microscope, the obtained solid electrolytes achieve a homogenous dispersion of Young’s modulus and surface electric field. As a result, the as-prepared SPEs present high tensile strength of 7.1 MPa, high ionic conductivity of 1.86 × 10⁻⁴ S·cm⁻¹ at room temperature, and wide electrochemical window up to 5.0 V, demonstrating increased mechanical strength and uniform lithium-ion migration channels for SPEs. Thanks to the as-prepared SPEs, the lithium-symmetrical cells show a highly stable Li plating/stripping cycling for over 1,000 h at 0.1 mA·cm⁻². The corresponding Li/LCoO₂ batteries also present good rate capability and excellent cyclic performance with capacity retention of 80% after 100 cycles at room temperature.