Battery Degradation and Performance
Pages 605–617 (13 pages)
Text on page 613
Accelerating Aging by Testing Above 85 °C
Specially designed 18650 cells with Gr|NMC640, Gr|NMC63.50.5 and Gr|NMC631 chemistries balanced at 4.05 V containing LiFSI electrolyte underwent cycle life testing at C/3 and C/20.
Operating temperatures ranged from 20 °C to 100 °C with an upper voltage cutoff of 4.0 V (prevents electrolyte oxidation).
Loss of lithium inventory and minor impedance growth are the only aging modes, enabling square root of time capacity decay and an equitable comparison across cells.
Cells operated at lower temperatures show an initial rise in capacity with cycling.
Best cells retain 87% capacity after 1400 C/3 cycles even at 85°C.
By designing cells to only have a single degradation mechanism even across chemistries, we can directly compare high temperature durability.
Source: C. Floras, S.M. Maher, K. Tuul, J. Harlow, M. Bauer, J. R. Dahn
Discharge capacity and voltage gap evolution with cycling for varying NMC chemistries.
Extracted from the PDF; charts and images may read imperfectly.
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