The fast-charging capability is a decisive purchase requirement, not only for electric vehicles. Five boundaries are technically restricting the charging time as shown below. Violating the cell-specific limits leads to accelerated cell aging or even safety risks. The progression of the maximum permissible charging current over time, considering all five limits, depends on the electrochemical and thermal initial and boundary conditions in a strongly nonlinear manner. In addition, as the anode surface potential inside the cell is not experimentally accessible, the suitability of a charging current profile can only be tested indirectly by costly and time-consuming cycling tests.
Moreover, the fast charge capability of the battery is dependent on module design, cooling, cell type and therefore has to be solved on system level. This is why the development of optimal current profiles in the multidimensional, nonlinear parameter space consisting of time, state of charge, state of health and temperature is challenging.