Ageing induced changes in electrical and thermal characteristics of cylindrical lithium-ion cells: A preliminary study on correlations for thermal behaviour monitoring

Ageing of lithium-ion cells leads to a deterioration of both electrical and thermal properties. Understanding this correlation is highly relevant for the thermal management of battery systems, as conclusions about thermal behaviour can be drawn using easily determinable electrical parameters. In this study, 9 cylindrical cells were aged under different operating conditions at ambient temperatures between 0 °C and 50 °C. After 10 months of ageing, relative capacity values between 89.5% and 56.2% were achieved. In addition to electrical parameters, the thermal conductivity at electrode level was determined in both in-plane and through-plane directions. The through-plane direction of the anode exhibited the most significant decline in thermal conductivity at the end of the test, showing an average reduction of 48.6% across all 9 cells. On average, the cathode showed a 28.9% decrease in the through-plane direction. The in-plane thermal conductivity of the anode decreased by 23.8%, while the cathode experienced an average decrease of only 2.1%. For estimating the effective radial thermal conductivity of the cylindrical jelly-roll with electrical parameters, R CT (r = -0.95) and R DC100%,10s (r = -0.87) are best suited. The degradation mechanisms increasing these electrical resistances also reduce thermal conductivity, establishing a strong correlation.