Ionic conductivity optimization of composite polymer electrolytes through filler particle chemical modification

TL;DR

This study explores how chemical modifications of filler particles in composite polymer electrolytes influence ionic conductivity, revealing optimal particle loadings and the role of particle composition in enhancing ion transport.

Contribution

It demonstrates that chemical manipulation of filler particles can optimize ionic conductivity in composite polymer electrolytes, highlighting the importance of particle composition and load.

Findings

Optimal ionic conductivity at 5-10% particle load

Particle composition significantly affects conductivity

High ionic channels form at specific filler loadings

Abstract

The addition of filler particles to polymer electrolytes is known to increment their ionic conductivity (IC). A detailed understanding of how the interactions between the constituent materials are responsible for the enhancement, remains to be developed. A significant contribution is ascribed to an increment of the polymer amorphous fraction, induced by the fillers, resulting in the formation of higher ionic conductivity channels in the polymer matrix. However, the dependence of IC on the particle weight load and its composition on the polymer morphology is not fully understood. This work investigates Li ion transport in composite polymer electrolytes (CPE) comprising Bi-doped LLZO particles embedded in PEO: LiTFSI matrixes. We find that the IC optimizes for very low particle weight loads (5 to 10%) and that both its magnitude and the load required, strongly depend on the garnet particle composition. Based on structural characterization results and electrochemical impedance spectroscopy, a mechanism is proposed to explain these findings. It is suggested that the Li-molar content in the garnet particle controls its interactions with the polymer matrix, resulting at the optimum loads reported, in the formation of high ionic conductivity channels. We propose that filler particle chemical manipulation of the polymer morphology is a promising avenue for the further development of composite polymer electrolytes.