Lithium-Ion

Understanding Capacity Loss in LFP/Graphite Pouch Cells at High Temperature through Modelling Modelling innovation: A novel “ABˮ model was proposed to interpret capacity loss incurred by lithium inventory loss and transition metal dissolution. This model directly reflects the dynamics of SEI growth rate as a function of SEI thickness and Fe dissolution from the cathode. Constant-rate (linear) iron dissolution, assumed by the model, is validated via chemical analysis of aged cells. Mechanism reflection: Through the “ABˮ modelling of the capacity vs time of LFP/graphite cells, it is reaffirmed SEI growth and the effects associated with transition metal deposition as the predominant mechanisms of capacity fade in LFP/graphite cells cycling at higher temperatures

“ABˮ MODEL

CAPACITY LOSS INTERPRETATION Model 1 Q(t) = Q01At1/2)

Model 2 Q(t) = Q01A1Btt1/2) A: lithium inventory loss to SEI growth B: iron deposition to accelerate inventory loss

Source: Black et al, Journal of The Electrochemical Society, 2025, 172, 090503

Observation: Fitted curves using model 2 are shown superimposed on the absolute capacity loss plots Conclusion: In LFP/graphite cells, Li inventory loss due to SEI growth, accelerated by transition metal deposition, is the predominant degradation mode

A comprehensive look at the performance of the LFP pouch cells introduced above showing the absolute capacity loss, normalized capacity loss, and voltage polarization at 40, 55, and 70 °C.

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