A Comparison between Electrochemical Impedance Spectroscopy and Incremental Capacity-Differential Voltage as Li-ion Diagnostic Techniques to Identify and Quantify the Effects of Degradation Modes within Battery Management Systems

Carlos Pastor-Fernández,Kotub Uddin,Gael H Chouchelamane,W Dhammika Widanage,James Marco

doi:10.1016/j.jpowsour.2017.03.042

Carlos Pastor-Fernández, Kotub Uddin + Show 3 more

Open Access

https://doi.org/10.1016/j.jpowsour.2017.03.042

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Abstract

Degradation of Lithium-ion batteries is a complex process that is caused by a variety of mechanisms. For simplicity, ageing mechanisms are often grouped into three degradation modes (DMs): conductivity loss (CL), loss of active material (LAM) and loss of lithium inventory (LLI). State of Health (SoH) is typically the parameter used by the Battery Management System (BMS) to quantify battery degradation based on the decrease in capacity and the increase in resistance. However, the definition of SoH within a BMS does not currently include an indication of the underlying DMs causing the degradation. Previous studies have analysed the effects of the DMs using incremental capacity and differential voltage (IC-DV) and electrochemical impedance spectroscopy (EIS). The aim of this study is to compare IC-DV and EIS on the same data set to evaluate if both techniques provide similar insights into the causes of battery degradation. For an experimental case of parallelized cells aged differently, the effects due to LAM and LLI were found to be the most pertinent, outlining that both techniques are correlated. This approach can be further implemented within a BMS to quantify the causes of battery ageing which would support battery lifetime control strategies and future battery designs.

Highlights

State of Health (SoH) is typically the parameter used by the Battery Management System (BMS) to quantify battery degradation with respect to its nominal state and it is often quantified based on two measures: capacity fade (CF) and power fade (PF) [3]
The AR-Equivalent Circuit Model (ECM) was fitted to the electrochemical impedance spectroscopy (EIS) measurements using the complex non-linear least squares algorithm (CNLS)
Similar as to the loss of active material (LAM), this study considers the shift toward lower capacities in the Differential Voltage (DV) curves to calculate the growth of the effects of loss of lithium inventory (LLI) because their variation can be observed clearer than the decrease of the height of the Incremental Capacity (IC) peaks toward lower voltages

Summary

Introduction

Intrinsic factors are currently mitigated by improving quality control, manufacturing processes and battery designs Extrinsic factors include those due to the inhomogeneous operating conditions that a LIB may be subject to, e.g. non-uniform current or temperature distribution within the complete battery pack. State of Health (SoH) is typically the parameter used by the BMS to quantify battery degradation with respect to its nominal state and it is often quantified based on two measures: capacity fade (CF) and power fade (PF) [3]. These metrics are directly related to available driving range and power, respectively. The definition of SoH within a BMS does not currently include an indication of the underpinning ageing mechanisms causing the degradation

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