Simulating lithium-ion batteries operation with MODAL recent development and some test cases

In order to improve lithium-ion batteries design, an in-depth understanding of limiting phenomena is necessary. The experimental approach (test the battery as a black-box) can now be complemented by a practical computational alternative. Simulation not only can give reliable and useful information about the origin of low capacity or poor performance, but also insight about the way to improve the design or the operation of a battery. MODAL is a code solving a coupled mass and charge transfer problem, with specialized battery-oriented dialog boxes; the battery designer can input easily critical parameters (geometry, material, transport and chemical properties, charge profile...) and obtain computational results such as concentration profiles, interface current density or a conventional characteristic curve (potential vs. state of charge). This paper reviews some developments recently introduced in MODAL and gives examples of analysis allowing better understanding of battery operation. The test-cases presented show how some design options can hinder the best use of a battery and what can be done to improve the design of a cell, or choose ad-hoc operation to get optimal use of an existing cell. Among the test-cases, the roles of the substrate interfacial area and of the charge procedure are explored in detail. Results are presented as classical (characteristic) curves and we discuss how the internal concentration profile can be used for a practical improvement of the cell (i.e. improve discharge rate via an increase of lithium salt concentration).