Fundamentals

Fundamentals

Lithium-on Intercalation by Coupled Ion-electron Transfer CIET

Coupled Ion-Electron Transfer CIET) theory is proposed and tested, unifying ion and electron transfer mechanisms to provide a more complete picture of the reaction. In experiments on common cathodes like LixCoO2 and LixNMC, it was shown that current rises linearly with lithium vacancy and does not follow Tafelʼs law in overpotential dependence, a finding that contradicts Butler-Volmer BV) model. The predictive power of the CIET model was demonstrated by collapsing hundreds of data points onto a universal curve using a small set of intrinsic material parameters. A linear decay in capacity with increasing current, a distinct signature of a CIET-limited reaction, was revealed by rate capability measurements across eight different electrode materials.

The conventional view that battery performance is diffusion-limited is challenged by this work, proving that the interfacial reaction could be a key bottleneck in commercial cells. Source: Zhang, Yirui, et al, Science 2025

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