Numerical analysis of accelerated degradation in large lithium-ion batteries

The size effect on degradation in lithium-ion battery cells is investigated by simulations of lithium iron phosphate/graphite LIB cells with different size. An electrical-electrochemical-thermal model considering degradation phenomena is modeled for a 1Ah pouch cell and a 55Ah pouch cell with an identical electrode design. Numerical results in the large cell shows the additional voltage drops of 27 mV and the mean temperature increase of 8 °C for 3C discharge due to overpotentials in metal current collectors and clear spatial imbalances of temperature, current density and electric potential. The capacity fade in the large cell is accelerated by about 33% for cycling operation due to the activated parasitic reactions at high temperature conditions. But even in an isothermal condition, the large cell still shows about 7% faster degradation than the small cell because it stays longer at high SOC in the charge process.