Diagnostic evaluation of detrimental phenomena in 13C-labeled composite cathodes for Li-ion batteries

13C-carbon black substituted composite LiNi0.8Co0.15Al0.05O2 cathodes were tested in model electrochemical cells to monitor qualitatively and quantitatively carbon additive(s) distribution changes within tested cells and establish possible links with other detrimental phenomena. Raman qualitative and semi-quantitative analysis of 13C in the cell components was carried out to trace the possible carbon rearrangement/movement in the cell. Small amount of cathode carbon additives were found trapped in the separator, at the surface of Li-foil anode, and in the electrolyte. The structure of the carried away carbon particles was highly amorphous unlike the original 12C-graphite and 13C-carbon black additives. The role of the carbon additive, the mechanism of carbon retreat in composite cathodes and its correlation with the increase of the cathode interfacial charge-transfer impedance, which accounts for the observed cell power and capacity loss is investigated and discussed.