Interfacial Barrier of Ion Transport in Poly(ethylene oxide)-Li 7 La 3 Zr 2 O 12 Composite Electrolytes Illustrated by 6 Li-Tracer Nuclear Magnetic Resonance Spectroscopy.

Fundamental understanding of the lithium-ion transport mechanism in polymer-inorganic composite electrolyte is crucially important for the rational design of composite electrolytes for solid-state batteries. In this work, the Li + ion transport pathway in a model composite electrolyte of PEO containing sparsely dispersed LLZO (PEO-LLZO) was studied by an advanced characterization technique, i.e., 6 Li-tracer NMR spectroscopy. By analyzing the 6 Li distribution within the PEO-LLZO composite at the end of the discharge of an electrochemical cell of 6 Li | PEO-LLZO | stainless steel with a fixed capacity (less than the total amount of the Li + in the composite) at various current densities, it is found that the interfacial barrier between LLZO and PEO could cause a reduced Li + flux through LLZO, particularly at high current densities, and therefore plays a critical role in determining the Li + transport pathway in the composite electrolyte. This work provides an intuitive picture of Li + ion transport in a polymer-inorganic composite electrolyte that is helpful to optimize and design better composite electrolytes.