To interpret the spectra and relate them to SoC values, we perform spectral deconvolution. Although this method is thoroughly described in , a concise summary is provided here for completeness. The process involves mathematically extracting the individual contributions of each component from the observed composite spectrum, thereby enabling the quantification of their respective concentrations and absorbances. The deconvolution proceeds by fitting the best pair between the experimentally measured absorbance A exp and the modelled absorbances, either A neg or A pos , given by Eqs. ( ) and (3). We performed this regression using a minimization function, e.g., the scipy.optimize.minimize function in Python or the fmincon function in MATLAB, both of which converge to an optimal solution.