EIS Benefits:
- Safion: quick and precise measurements, easily implementable
- Gives us resistance and capacitance values, that are characteristic of cell aging
- Could give us info on the cell aging (SEI, …) thanks to the R values
EIS limitations:
- Safion: QS is not directly linked to the SOH of a cell so we cannot use it as a screening criteria
- The rQS is mainly linked to the low-frequency resistance of the cell
- To estimate the SOH of a cell: need for a Deep Learning algorithm and a data set
- Entroview can also help us on the aging aspect
The data we get from a Safion measurement is: temperature, OCV, IR at 1 kHz, Ohmic Resistance, Charge Transfer Resistance and Low-frequency Resistance, Nyquist plot, and quality scores
The QS are calculated based on the several features of the EIS data that can be visualized through the Nyquist plot.
Among the parameters that affect the EIS data, the most significant one is the temperature of the cell during measurement.
The absolute quality score is not the “absolute” standalone quality of the cell, but rather a relative one. It also changes as new cells enter the database as part of the ExaMight’s adaptive algorithms. The AQS was a metric that we designed to compare the quality of different cell types. This comparison basis is yet to be implemented in the ExaMight’s user interface in future software releases. Currently, the ExaMight can relatively compare the quality of cells of the same type. For a summarized score, we advise using the relative QS
