Detection of cell-stack inhomogeneities via mechanical SOC and SOH measurement

Common lithium-ion battery cells consist of a cathode material, such as a Nickel-Manganese-Cobalt NMC and a graphite anode. Expansion of the graphite anode due to lithium intercalation while charging leads to macroscopic expansion of the entire cell, which is directly related to the state-of-charge. Therefore, conventional rigid-battery-module bracing causes pressure forces to build up periodically in the cell stack due to charging and discharging steps. In homogeneous cell stacks, the measured-pressure curve is a multiple of a single cell's measured pressure force curve. One cell, perhaps prematurely aged (i.e. diverging state-of-health), disturbs the module-pressure force curve. Due to the mechanical coupling of the cells in a module, a single sensor can monitor this.