Accelerated Electrochemical Parameterization of NMC and Graphite via Current Interrupt and Voltage Relaxation Extrapolation

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Physics-based battery models depend on well-characterized electrode parameters, yet established techniques, the Galvanostatic Intermittent Titration Technique (GITT) and Electrochemical Impedance Spectroscopy (EIS), require several weeks of experimental time due to rest times to OCV. Here, a Current Interrupt Method (CIM) is presented that simultaneously extracts open circuit voltages (OCVs), diffusion coefficients, and exchange current densities from short current pulses and rests without the need for full electrochemical equilibration. OCVs are determined by fitting a logarithmic function to the voltage relaxation during each rest and extrapolating to 3 h; diffusion coefficients from the gradient of the pulse voltage response against √
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and extrapolated OCVs; and exchange current densities from the initial voltage transient at the start of each rest, deconvoluted using a series resistance from a single EIS measurement. To validate this approach, NMC920503 and graphite lithium metal half-cells were tested with EIS, a 3 h rest GITT, and CIMs with rest durations from 1 h to 5 s. Time savings of 92% and 79% (∼ 13 d) over the GITT are shown for NMC920503 and graphite, respectively. Finally, a GITT-to-CIM fit validation procedure is introduced to determine the minimum viable rest duration for any material, enabling systematic optimization of future CIM protocols.
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