Characterisation and modelling of the transport properties in lithium battery gel electrolytes: Part I. The binary electrolyte PC/LiClO 4

Abstract

A recent development trend for rechargeable lithium batteries is the use of ternary gel electrolytes. The main advantage of the gels is the mechanical rigidity, which improves as the polymer content is increased. However, the transport properties deteriorate with increasing polymer amount. This dualistic optimisation problem has caused an increased interest in understanding the transport processes in gels, however no full characterisation or modelling study could be found in the literature. In this paper, which is the first part of a study of the transport in the ternary gel system PMMA/PC/LiClO 4, the liquid electrolyte PC/LiClO 4 is characterised and modelled for concentrations between 0.1 and 2 M according to a previously employed methodology, based on electrochemical measurements. A model using concentration dependent interaction parameters proved to describe the results in the whole concentration region well. The cationic transport number and salt diffusivity were determined to be approximately 0.3 and 1e−10 m 2/s, respectively. The mean ionic activity factor variations prove to be substantial. Furthermore, it was demonstrated that the inter-ionic friction was important to consider at concentrations above 1 M. The fundamental friction parameters determined in this part will be used in the following part of the study to describe the friction between ions and solvent.