Interfacial Barrier of Ion Transport in Poly(ethylene oxide)-Li7La3Zr2O12 Composite Electrolytes Illustrated by 6Li-Tracer Nuclear Magnetic Resonance Spectroscopy.

Abstract

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., 6Li-tracer NMR spectroscopy. By analyzing the 6Li distribution within the PEO-LLZO composite at the end of the discharge of an electrochemical cell of 6Li | 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.