Lithium-Ion: Cathode

Degradation Of NMC Cathodes Via Hydrogenation From Carbonate Solvents The prevailing theory of cathode degradation self-discharge in carbonate-containing electrolytes centers around the diffusion of lithium from the electrolyte into the cathode. However, using computational techniques such as Density Functional Theory DFT, and spectroscopy techniques such as DFT, XANES, NEXAFS, XRD and XAS, Wan et al. discovered that insertion of protons into a charged cathode can occur via decomposition of CH 2 containing species in the electrolyte. This hydrogen transfer from the the carbonate solvent to the delithiated cathode accelerates at higher cut-off voltages 4.3V.

TOFSIMS DEPTH PROFILES

Solvent-mediated Hydrogenation A B

Pristine NMC532 film in LP57 NMC532 filmcycled to 4.46V in LP57

Wan et al. present a new mechanism of cathode degradation and self-discharge for NMC cathodes via solvent-mediated hydrogenation of the cathode.

Note the change in H- concentration as a function of film depth for the charged electrode Figure B Source: Wan et al. Science 2024

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