Li-ion storage models for energy system optimization: the accuracy-tractability tradeoff

There is a need for accurate analytical models that describe how a Lithium-ion battery's state of charge evolves as a result of a charging or discharging operation and that can be used in optimization problems. Although 'white box' models that take into account the details of electro-chemical processes can be highly accurate, they are not typically suitable for optimization problems. We propose two models that represent different tradeoffs between accuracy and tractability. We validate the accuracy of these models with data traces obtained from extensive experiments using two different commercially-available cells based on two distinct Li-ion technologies. We find that one of our models can be easily adopted for use in a mathematical optimization problem, while significantly increasing the range of C-rates over which it is accurate (<5% error) compared to the models that are currently being used.