How is the concentration determined for rapid lithium ion transfer in highly concentrated electrolyte solutions?

Abstract

Highly concentrated electrolyte solutions have various unique characteristics for use in secondary batteries, including lithium ion batteries. The superlative performance of batteries should be achieved not at a saturating concentration, but rather at an appropriate concentration in terms of both Li+ transport in electrolyte solutions and Li+ transfer across interfaces between the electrodes and electrolyte solutions. This work focused on the latter, and studied the effect of the electrolyte concentration on interfacial Li+ transfer kinetics. Interfacial resistance between a solid electrolyte and LiBF4/PC electrolyte solutions of different concentrations were investigated by impedance spectroscopy using a four-electrode cell, and the activation energy was evaluated by the least-squares method. The results revealed that specific concentrations reduced interfacial resistance and activation energy. The solution structure of these electrolyte solutions was characterized by Raman spectroscopy, and was associated with the low interfacial resistance and activation energy.