Characterization of Li+ Transport through the Organic-Inorganic Interface by using Electrochemical Impedance Spectroscopy

Understanding Li⁺ transport at polymer||inorganic interfaces is crucial for developing composite electrolytes in solid-state batteries. In our investigation, we employed impedance spectroscopy and established a multilayer methodology for assessing Li⁺ transport at this interface. The inorganic phase chosen was Li_6.25Al_0.25La₃Zr₂O₁₂ (Al−LLZO), and the organic phase comprised a Poly(ethylene oxide) (PEO) network with dangling chains. Li⁺ incorporation in the polymer, as a free either salt or associated with anion grafting onto the PEO network, was explored. Additionally, the PEO network was either pressure-adhered to the inorganic surface (ex-situ configuration) or synthesized onto the Al−LLZO surfaces (in situ configuration) to investigate processing effects on Li⁺ transport. Using a Transmission Line Model for impedance data analysis, our study identified two key elements governing Li⁺ transport at the interface: R_i, representing resistance along the ionic pathway, and R_t and C_t, describing distributed resistance and capacitance within the interface. We observed that R_i is influenced by the polymerization process in the presence of Al−LLZO ceramic, while R_t remains constant regardless of the synthesis method. This suggests varying Li⁺ concentrations at the interphase in the in situ configuration, while interface/interphase heterogeneity remains consistent across configurations. The estimated activation energy indicates more energetically favorable direct Li⁺ transport in the in−situ configuration.

DOI : 10.1149/1945-7111/ad2595

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