Accessing the current limits in lithium ion batteries: Analysis of propensity for unexpected power loss as a function of depth of discharge, temperature and pulse duration

Abstract

The maximum extractable power from lithium-ion batteries is a crucial performance metric both in terms of safety assessment and to plan prudent corrective action to avoid sudden power loss/shutdown. However, precise estimation of state of power remains a challenge because of the highly non-linear behaviour of batteries that are further aggravated at extremities of temperature as well as battery state of charge. To address this issue, we present the current limit estimate (CLE), which is determined using a robust electrochemical-thermal reduced order model, as a function of the pulse duration, depth of discharge, pre-set voltage cut-off and importantly the temperature. The CLE calculated from the model is experimentally validated using commercial mobile phone cells. With cell temperatures varying from 0 °C to 65 °C and full range of depths of discharge, the model gives a prediction accuracy of more than 98%. The model is computationally efficient and compact enough to be implemented on battery management systems for on-board, real time state of power estimation. Further, key insights on what limits power capability of a battery are drawn through an analysis of contributions of different kinetic and transport processes to the cell resistance as a function of temperature and depth of discharge.