Carbon nanotubes lower percolation threshold in sodium-ion cathode

Carbon nanotubes established an electronic-percolation network in a P2-type layered sodium-ion battery cathode at just 1 volume percent, the lowest conductive-additive loading reported in the study. Researchers experimentally measured percolation thresholds for composites containing the positive-electrode active material Na0.68Mn0.45Co0.55O2 and several carbon additives, including Super P, Vulcan XC-72, carbon nanotubes and acetylene black. The material-level comparison indicates that nanotubes could help minimize the amount of inactive conductive material while still providing sufficient electronic connectivity.

Carbon nanotubes reached that condition at 1 volume percent, whereas acetylene black required the highest loading among the additives considered to surpass its threshold, at 4 volume percent. The supplied study abstract does not report the corresponding thresholds for Super P or Vulcan XC-72, so the numerical comparison is limited to the additives for which values were specified. The findings concern laboratory electrode composites based on one P2-type sodium-manganese-cobalt oxide and do not establish how the additives will behave in other active materials or commercial cell designs.

Despite their low percolation threshold, carbon nanotubes did not produce the strongest reported electrochemical results. Electrodes containing acetylene black exhibited superior cycling stability and the highest discharge capacity, reaching up to 120 mAh/g with a Coulombic efficiency of 83%. In other words, the additive that needed the greatest carbon concentration to form an electronically connected network yielded the best reported capacity and stability in this experimental comparison.

The apparent contradiction is the central result: establishing electron percolation is a fundamental part of composing an electrode, but the threshold alone does not determine its electrochemical behavior. That distinction matters when conductive additives are evaluated for sodium-ion battery cathodes. Percolation measurements provide a quantitative indication of how much carbon is needed to create a connected conductive phase, but the reported electrode results show that a low threshold cannot serve as a complete predictor of discharge capacity or cycling stability.

The authors associate the findings with the need to examine electrode-formation methods and the overall composition of the electrode rather than judge conductive additives solely by their percolation threshold. This is a study-specific result, not evidence that acetylene black is universally superior or that carbon nanotubes are unsuitable for other cathodes. Within the scope of the tested Na0.68Mn0.45Co0.55O2 system, the experiments present two separate optimization targets.

Carbon nanotubes offered the lowest loading for electronic percolation and showed potential for reducing inactive conductive content. Acetylene black, by contrast, delivered the highest discharge capacity and superior cycling stability in the electrodes tested. The research therefore offers a quantitative foundation for comparing conductive additives in P2-type layered oxide cathodes while making clear that electrical connectivity and electrochemical performance must be evaluated as related but distinct properties.

Subject of Research: Electronic percolation and electrochemical performance of carbon additives in P2-type sodium-ion battery cathodes

Article Title: Carbon additives for P2–layered sodium–manganese–cobalt oxide cathode for Na-ion batteries: percolation characteristics and electrochemical performance

Article References: Lochina, A. A., Kayumov, R. R., Subcheva, E. N., Volodin, A. A., Lochin, G. A., & Shmygleva, L. V. (2026). Carbon additives for P2–layered sodium–manganese–cobalt oxide cathode for Na-ion batteries: percolation characteristics and electrochemical performance. Journal of Materials Science, 61(40), 31077-31096. https://doi.org/10.1007/s10853-026-13640-9

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13640-9

Keywords: sodium-ion batteries, P2 layered oxide, carbon nanotubes, acetylene black, electronic percolation, cathode materials, electrode conductivity, discharge capacity, cycling stability, conductive additives, Carbon, additives