An investigation of irreversible heat generation in lithium ion batteries based on a thermo-electrochemical coupling method

Irreversible heat generation plays a dominant role in li-ion batteries, it is thus highly important to study its evolution in order to adapt the development of electronic devices. Internal irreversible heat generation mainly consists of two parts: one arises from the polarization and the other one from ohmic heat generation. A thermo-electrochemical coupling model was established here to study the production and evolution of the irreversible heat within li-ion batteries considering dynamic parameters and the electric double layer. Results show that the irreversible heat production rapidly increases with the discharge rate and the polarization heat production is the dominating factor. Ohmic heat production mainly resulted in the heating of the electrolyte, and the heating produced at the negative active materials result to be negligible respect to the one produced at the positive active materials. According to calculations, the ratio between the ohmic heat production and the total irreversible heat production increases from 24.2% at 3 C to 32.8% at 8 C, thus, the ratio related to the polarization heating decreases from 75.6% to 67.2%. In addition, effects of the particle size at the positive and negative electrodes at the rate of 3 C were studied. Results show that the negative electrode particle size has thus a more significant impact on the irreversible heat production and the polarization heat production of the battery.