The open-circuit voltage curve is an important parameter in modeling the electrical behavior of lithium-ion batteries. A common assumption in describing the changes in open-circuit voltage curve characteristics during cell aging is that the shape of the open-circuit voltage curves of the individual electrodes of a lithium-ion battery does not change with aging. We experimentally investigated this assumption in a recently published study. Our results show that the shape of the open-circuit voltage curve of nickel-rich NMC-811 does not change significantly, whereas we found a significant change in the curve shape of silicon-graphite. This aging-dependent change is caused by a reduced relative contribution of silicon to the total anode capacity. These results should be considered in the implementation of state estimation algorithms for cells with silicon-graphite anode to provide accurate and reliable state estimation for aged cells.
Change in the half-cell open-circuit potential curves of silicon–graphite and nickel-rich lithium nickel manganese cobalt oxide during cycle aging / Julius Schmitt, Markus Schindler, Andreas Jossen / Journal of Power Sources (2021): 230240 - DOI