Failure Study of Commercial LiFePO₄Cells in over-Discharge Conditions Using Electrochemical Impedance Spectroscopy

Abstract

Electrochemical impedance spectroscopy (EIS) studies were carried out on commercial 18650 LiFePO 4 cells at different States of Charge (SOCs) to investigate failure in over-discharge conditions. The charge/discharge curves, capacity, charge acceptance, temperature, and impedance were characterized and analyzed. The EIS results show that the de-convoluted Ohmic resistance, R 0 , solid electrolyte interphase (SEI) resistance, R SEI , and Warburg Coefficient, σ, change with cycle number in some patterns, indicating the occurrence of corrosion of the current collector, SEI breakdown/decomposition and reformation, and the development of diffusion barriers of Li + in the electrode, respectively. These parameters, R 0 , R SEI , and σ are associated with failure and can be used as indicators of incoming failure. The EIS results from the three-electrode system verify that the EIS results from the twoelectrode system (practical 18650 cells) are reliable, which lays the foundation for the use of electrochemical impedance on practical applications of LIB cells. Overall, electrochemical impedance spectroscopy can be used as an effective and reliable tool to monitor the state of health, predict incoming failure of the cell, and issue a warning before failure without disturbing the operation of the cell.

Graphene-modified nanostructured vanadium pentoxide hybrids with extraordinary electrochemical performance for Li-ion batteries

“…The results were fitted using the model 28 shown in Fig. 2, and the fitting results are listed in Supplementary Table 1.…”

“…These cells were tested with an Arbin Battery cycler (BT-2000, Arbin, TX, USA) using different C-rates between 1.5 and 3.6 V. A Solartron 1287A/1260A Potentiostat/Impedance System (Solartron Analytical, England, UK) was used to measure the AC impedance of these cells in the frequency range of 0.01 Hz-1 MHz with an amplitude of 5 mV. The results were fitted using the model 28 , where R 0 is the contact resistance, R e and C e refer to the resistance and capacitance of the V 2 O 5 electrode, R ct and C dl stand for the charge-transfer resistance of the redox reaction of vanadium in V 2 O 5 and the double-layer capacitance in the electrode, respectively, and W d refers to the Warburg diffusion impedance, which could reflect the diffusion of Li ions in the V 2 O 5 .…”

Expanding the Operational Limits of the Single-Point Impedance Diagnostic for Internal Temperature Monitoring of Lithium-ion Batteries

“…Consequently, non-invasive diagnostic techniques for lithiumion batteries have recently garnered considerable attention, particularly those using electrochemical impedance spectroscopy (EIS). EIS-based analyses havetraditionally been used for determining internal resistances and capacitances, thermophysical properties, and/or for modeling thermal behavior of batteries [22,[29][30][31].With respect to battery diagnostics, researchers have exhibited EIS-based correlations to monitor both state of health (SOH) [32][33][34][35][36][37] and internal temperature [10,15,16,21,[37][38][39][40].These diagnostic techniques are particularly attractive for several reasons: (i) as previously-mentioned, EIS measurements are non-invasive and therefore do not require battery disassembly or physical insertion of thermocouples or other instrumentation; (ii) they are virtually instantaneous (<1 second) in comparison to the cell's thermal response time; and (iii) they can be applied to any lithium-ion battery chemistry or cell geometry.…”

“…SOH determinations via EIS have been performed to detect abuse and/or capacity fadeof commercial lithium-ion batteries through various mechanisms, including overcharge [32,33], overdischarge [34], and aging effects [35,36]. Among these types of battery problems, overcharging is perhaps the most concerning with regard to large format battery packs due to a battery management system's inability to detect unbalanced battery voltages or inaccurate state of charge measurements [33].…”

Detection of Internal Short Circuit in Lithium Ion Battery Using Model-Based Switching Model Method

“…However, the Li-ion battery can develop dangerous malfunctions [2,3] such as internal short circuit (ISCr) [4,5] and cell reversal [6]; the main causes of these phenomena are overcharge [7] and overdischarge [8]. The ISCr may cause thermal runaway when the temperature rise by the ISCr in the battery exceeds a certain point [5] or the ISCr resistance R ISC f is lower than a certain value [9].…”