Investigations of battery degradation behaviour and state of charge reset of lithium-ion batteries using differential temperature

Beyond using the temperature measurement of batteries for the power and thermal management, it also provides valuable information on the state of health (SOH) and state of charge (SOC), just like the voltage and the current. This work highlights the gradual increase in the surface temperature due to age of the three different chemistries, lithium nickel cobalt aluminium oxide cathode with silicon-doped graphite anode (NCA-GS), nickel cobalt aluminium oxide cathode with graphite anode (NCA-G) and lithium nickel manganese cobalt oxide cathode with graphite anode (NMC-G). The rate of temperature change with respect to voltage (DTV) was obtained in charge and discharge direction and plotted with voltage and SOC to study the ageing pattern of the temperature using a low current rate of 0.2C in an insulated setup. In the extrema analysis of the DTV versus voltage curve, the anode material significantly affects the choice of the extrema that correlate well with the SOH by the contribution of the reversible heat attributed to the intercalation of lithium in the electrodes. The result shows that the second minima, which is the negative peak value of the DTV ( ° C /V), was used to estimate the SOH with a mean absolute error of 1.443% and 1.078% in NMC-G and NCA-G, respectively. When using the voltage shifts of maxima 2, the SOH was estimated with a mean absolute error of 1.309% in NCA-GS. Additionally, a particular zero crossing of the DTV, related to stage 2 in the graphite, is presented as an SOC reset for state estimation purposes. This highlights the impact of the anode on the DTV analysis and identifies the extrema to be considered when using the silicon-doped graphite anode and the graphite-only anode. • Ageing study with focus on temperature development. • Accurate SOH estimation using battery cell’s temperature response. • Distinct features in DTV curve can help to reset SOC for estimation algorithms. • Insulated setup at a low C/5 current rate to reduce influence of ambient and different heating mechanisms on temperature profile. • Insights in voltage shift and absolute values changes of DTV extrema‘s during charge period.