On the decisive role of passive material properties and morphology in Li-ion batteries

Abstract

vehicles due to their outstanding energy and power density. A typical Li-Ion battery electrode is a porous composite consisting of active material (particle diameter ~10-20 µm), conductive carbon (particle diameter ~100 nm), and polymeric binder. The carbon black and binder form a microporous phase (CB domain) which is distributed in the macro-pores of the active material network and ensures mechanical stability and electrical contact. However, at high current densities, e.g. during fast charging, the transport of Li-ions in the electrolyte is decisive for the performance of the battery cell and the CB domain increases mass transport limitations. [1,2] In order to assess the effect of the CB domain we performed detailed simulation studies on the pore-scale specifically resolving the transport processes in the CBD. Simulations were performed on reconstructions of NMC electrodes with different thickness and density which were created with the help of synchrotron tomography and a 3D stochastic microstructure generator [1,3,4]. In our presentation we cover different properties of the CBD and their impact on cell performance. More specifically, we investigate the influence of the distribution in the pore space [1,3], the distribution across the electrode [2], the volume of CBD in the electrode [3], and finally the morphology of the CBD. Based on these results different electrode configurations were evaluated regarding their optimization potential. This virtual screening provides material-structure-function relationships which are a helpful tool for the development of improved functional materials and electrochemical devices.