Electrochemical Impedance Spectroscopy of PEO-LATP Model Multilayers: Ionic Charge Transport and Transfer

Solid-state batteries are seen as a possible revolutionary technology, with increased safety and energy density compared to their liquid-electrolyte-based counterparts. Composite polymer/ceramic electrolytes are candidates of interest to develop a reliable solid-state battery due to the potential synergy between the organic (softness ensuring good interfaces) and inorganic (high o ionic transport) material properties. Multilayers made of a polymer/ceramic/polymer assembly are model composite electro- lytes to investigate ionic charge transport and transfer. Here, multilayer systems are thoroughly studied by electrochemical impedance spectroscopy (EIS) using poly(ethylene oxide) (PEO)-based polymer electrolytes and a NaSICON-based ceramic electrolyte. The EIS methodology allows the decomposition of the total polarization resistance (R-p) of the multilayer cell as being the sum of bulk electrolyte (migration, R-el), interfacial charge transfer (R-ct), and diffusion resistance (R-dif), i.e., R-p =R-el + R-ct + R-dif. The phenomena associated with R-el,R- (ct), and R(dif )are well decoupled in frequencies, and none of the contributions is blocking for ionic transport. In addition, straightforward models to deduce R-el, R-dif, and t(+) (cationic transference number) of the multilayer based on the transport properties of the polymer and ceramic electrolytes are proposed. A kinetic model based on the Butler-Volmer framework is also presented to model R-ct and its dependency with the polymer electrolyte salt concentration (C-Li(+)). Interestingly, the polymer/ceramic interfacial capacitance is found to be independent of C-Li(+) impedance of C-Li(+).

Automated summary

Solid-state batteries are revolutionary technologies with increased safety and energy density compared to liquid-electrolyte-based batteries. Composite polymer/ceramic electrolytes are promising candidates for reliable solid-state batteries due to the potential synergy between organic and inorganic materials. This study thoroughly investigates multilayer systems using electrochemical impedance spectroscopy (EIS) and proposes models to analyze the transport properties of the polymer and ceramic electrolytes. Interesting findings include the decoupling of polarization resistance components and the independence of the polymer/ceramic interfacial capacitance on electrolyte salt concentration.