Influence of the Active Material on the Electronic Conductivity of the Positive Electrode in Lithium-Ion Batteries

Electronic conductivity is one of the critical factors that govern the performance of high-energy lithium-ion batteries. However, until now, equations have been used to simulate electrode behavior in the absence of the necessary experimental background. In this study, we examined whether or not two commonly used equations can be used to express the electronic conductivity of a positive electrode fabricated with an NCA-based material. The electronic conductivity of this positive electrode was comprehensively examined, and the experimental results were used to validate the two above-mentioned equations. It was revealed that (i) the electrode density and weight ratio of carbon black affect electronic conductivity in different ways and (ii) electronic conductivity is influenced by the volume fractions of both conductive carbon and active material. This deviation from classical percolation theory arises from the electronic conductivity of the active material, which cannot be regarded as an insulator. We therefore derived an empirical equation for a positive electrode composed of an NCA-based material. The empirical equation not only simulated the electrode more accurately, it also provides a better understanding of the electronic-conduction mechanism and helps to facilitate better electrode and battery design.