Modelling the rheology and electrochemical performance of Li4Ti5O12 and LiNi1/3Co1/3Mn1/3O2 based suspensions for semi-solid flow batteries

Abstract

A semi-solid flow battery, consisting in a single channel with millimetric width, was operated in flow conditions using Li4Ti5O12 (LTO) or LiNi1/3Co1/3Mn1/3O2 (LNCM) based suspensions versus Li metal. Cell voltages were measured experimentally for various values of charge/discharge current. A model of the electrochemical cell was developed and validated by comparing calculated results with experimental data. The model consists in solving simultaneously the suspension rheology, potential and current within the cell (secondary distribution) and state of charge evolution between the inlet and outlet. Modelling results indicate low pressure drop (<50 kPa), nearly-homogeneous velocity profile along the channel and potential and current gradients in the cell. Comparison of experimental and calculated results indicate that the model takes into account the influence of applied current density on the cell potential but with significant differences on their absolute value, which are discussed in terms of electrochemical stability for the semi-solid suspensions during cycling. Results detailed in this article can, therefore, be applied to larger electrochemical cells or systems based on alternative chemistries, operated in flow conditions.