Quantifying Phase Contributions to Ion Transport in Organic-Inorganic Composite Electrolytes

Polymer-ceramic composite electrolytes represent a promising strategy for realizing solid-state batteries. However, ion transport in such organic-inorganic hybrid systems remains poorly understood. Here, we reveal the mechanism of ion transport in model hybrid electrolytes composed of Li_1.3Al_0.3Ti_1.7P₃O₁₂ (LATP) particles and various highly concentrated liquid electrolytes with conductivities similar to those of polymer electrolytes. By comparing the impedance responses of LATP particles suspended in Li⁺ electrolytes and in K⁺ electrolytes, where LATP particles are not DC-conductive, we accurately quantify the contribution of LATP to the overall hybrid electrolyte conductivity. This further allows calculation of particle interfacial resistances and overall hybrid electrolyte transference numbers. Our study indicates that solvent's Li⁺ solvation strength, Li⁺ transference number in the organic phase, and inorganic particle size are critical factors governing Li⁺ conductivity of hybrid electrolytes, suggesting single-ion conducting polymer matrices, in combination with large inorganic particles and plasticizers facilitating Li⁺ desolvation, are favored when designing polymer-ceramic composite electrolytes.