Our work measuring the contact resistance of carbon-NMC interfaces has been published in Advanced Energy Materials: “Contact resistance of carbon-Lix(Ni,Mn,Co)O2 interfaces”.
We find that the bulk electronic conductivity of NMC has previously been underestimated by orders of magnitude because contact resistances were not properly excluded from measurements. We also find a significant carbon-related impedance component, as resistive as the charge-transfer resistance but at an even lower frequency.
In this study, we utilize 3-electrode coin cells which are essential for isolating the working electrode impedance from that of the counter electrode. See this video tutorial to learn how we did that.
This contact resistance work is yet another piece of evidence that interface properties are important in the kinetics of Li intercalation kinetics (as opposed to the literature that tends to focus on bulk properties). Check out our earlier work identifying surface-limited kinetics by observing inter-particle inhomogeneity and also by measuring bulk vs. surface kinetics.