**6. Conclusions**

Parameter identification methods (based on ECM and EIS) for a Li-Ion battery are compared considering their similarities and differences. Hysteresis is the major difference between the two methods for resistance identification. To compare the methods, the following theories are developed:


These theories are validated by experimental results. The parameter extraction algorithm was applied for impedance spectra of two different batteries. The proposed hysteresis-free resistance identification method is used to analyze data obtained from a charging–discharging test. Finally, a match is found for the value of internal resistance from both methods with an insignificant tolerance. The proposed parameter extraction will be useful for the online EIS where fast interpretation of impedance spectrum is necessary. The quadratic model of hysteresis resistance separation is computationally effective and will be useful for the modeling of a battery. The proposed methods will be supplementary to track electrochemical parameters properly which can improve the accuracy of SOH prediction.

**Author Contributions:** All the authors contributed substantially to the manuscript.Contributions of each author are as follows: conceptualization, S.M.R.I., S.-Y.P., and B.B.; methodology, S.M.R.I.,and B.B.; software, S.M.R.I.; validation, S.M.R.I. and S.-Y.P.; formal analysis, S.M.R.I.; investigation, S.M.R.I.; resources, S.I. and S.-Y.P.; data curation, S.M.R.I.; writing—original draft preparation, S.M.R.I.; writing—review and editing, S.M.R.I. and S.-Y.P.; visualization, S.M.R.I.; supervision, S.-Y.P. and B.B.; project administration, S.-Y.P.; funding acquisition, S.-Y.P. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the National Science Foundation of under Grant No. 1454578.

**Acknowledgments:** This work was supported by the National Science Foundation under Grant No. 1454578. However, any opinions, findings, conclusions, or recommendations expressed herein are those of the authors and do not necessarily reflect the views of the National Science Foundation.

**Conflicts of Interest:** The authors declare no conflict of interest.The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
