Performance Degradation of Thermal Parameters During Cycle Ageing of High Energy Density Ni-Mn-Co based Lithium-Ion Battery Cells ‘ T. Stanciu¹, D.-I. Stroe¹ (dis@et.aau.dk), M. Swierczynski¹, N. Nieto², J. Gastelurrutia², J.-M. Timmermans³, R. Teodorescu¹ ‘ ¹Department of Energy Technology, Aalborg University, Denmark, ²IK4-IKERLAN Technology Research Center, Spain ³MOBI Research Group, Vrije Universiteit Brussel, Belgium Introduction NMC-based Li-ion battery Property Value Cathode Li(NiCoMn)/O2 Anode Graphite Nominal capacity 20 Ah Nominal voltage 3.7 V Max charging voltage 4.15 V Min cutoff voltage 3 V Charge current Continuous 0.5 C-rate Discharge current Continuous 5 C-rate Operating temp. -30oC/+50oC Storage temp. Electric vehicles (EV) have faced an accelerated market penetration in the last years; Lithium-ion (Li-ion) batteries (especially the NMC chemistry) are receiving the highest interest from EV manufacturers because of their superior performance parameters (e.g., energy density and specific energy) and increased lifetime in comparison to other battery technologies; Li-ion batteries still pose thermal management challenges that need to be addressed for maximizing performance and reducing safety concerns; Thus, the thermal behavior of the battery needs to be assessed under various operating conditions and the evolution during ageing of battery thermal parameters has to be mapped. Thermal Parameters Assessment Experimental Set-Up Cycle Aging – 9 conditions Stress factor I II III IV V VI VII VIII IX C-rate (cha/dch) C/3 – 1C C/3 – C/3 C/3 – 2C T (oC) 25 35 45 DOD (%) 80 50 20 Max SOC (%) 90 75 60 Min SOC (%) 10 40 Cell # G270 G271 G272 G277 G273 G274 G275 G276 G278 Literature Review Sensitivity Analysis. Internal Resistance Entropic Heat Coeff. Emissivity Thermal Parameter Importance Internal Resistance [mOhm] HIGH  Entropic Heat Coeff. [mv/K] MEDIUM Heat Capacity [J/gK] X Thermal Conductivity [W/K] LOW Emissivity [-] At 10°C, 25°C, 40°C 90% SOC … 10% SOC Results – for cell G277 Capacity Emissivity BOL 1500 FEC Angle [deg.] 30 Distance [m] 0.5 Ambient T [°C] 23.5 26.0 Cell T [°C] 37.2 44.0 Emissivity 0.49 0.45 Internal Resistance Entropic Heat Coefficient SOC=80% T=25°C SOC=10% EHC increase Capacity decrease EHC decrease Resistance increase Resistance increase No change in EHC Similar internal resistance increase trend independent on measurement SOC and temperature The evolution of the EHC with the aging is highly dependent on the measurement SOC Slight change of the emissivity value during ageing Conclusions High increase of the internal resistance (e.g. 150%) – depending on cycling conditions; measurement SOC and temperature do not influence the increase trend; The EHC changes during cycle ageing – the evolution trend is highly dependent on the measurement SOC; This work has been part of the NMP.2013-1 Batteries2020 project (Grant agreement GC.NMP.2013-1 /GA nº 608936). Authors gratefully acknowledge the involved partners for the extended collaboration and the European Union’s Seventh Program for Research for providing financial support.