Electrochemical Impedance Studies of Internal Short Circuits of Lithium-Ion Batteries Under Mechanical Abusive Conditions
Authors: Mundhe Sanket S , Thangavel Naresh kumar , Islam Mahbub , Arava Leela mohana reddy , Newaz Golam 
Published: December 2020

Due to the high energy density and long lifetime, lithium-ion batteries (LIB) become ubiquitous energy storage systems for electric vehicle operations1. However, a higher energy density frequently results in a developed risk of thermal instability issues, where a series of heat-producing reactions can quickly occur, leading to fire and even explosions2. Due to the prevalent utilization in electric vehicles, battery abuse can hardly be avoided as LIB is exposed to many accidents, and mechanical abuse of various degrees of intensity often paves the way for internal short-circuiting of components through rupturing of separators3-4. Such battery failure induced by mechanical damage can lead to electrical and chemical hazards together with fire, which can result in danger to life, the environment, and the infrastructure and should therefore not occur in the field. The origin of such thermal-induced battery degradation certainly caused by short-circuiting of battery components mostly by direct contact of anode and cathode electrodes. To mitigate these issues and caution the electric vehicle drivers about thermal runaway events, the development of a diagnostic method to identify the damage mechanism under mechanical deformation and corresponding electrical behavior is essential.

The onset of short circuits often characterized by a sharp increase in current, temperature, and rapid drop in voltage and set pass criteria as the absence of these potentially dangerous events as which may be enough for regular safety testing. Such events detected by a range of techniques including electrochemical impedance, incremental capacity-differential voltage, infra-red, tomography, etc5-7. However, it is challenging to design repeatable experiments that can emulate early-stage incubation of field ISC failure. Herein, we demonstrate resistance measurement by electrochemical impedance spectroscopy as an indicator for the detection of an internal short circuit of LIBs. The occurrence of ISC at different mechanical deformative conditions is evaluated through proper equivalent circuit model with multi-frequency and alternating voltage or current signal. The fitted results reveal that cathode-electrolyte interface resistance can be used to predict the onset of ISC due to mechanical abusive conditions. The obtained results demonstrate that impedance spectroscopy, together with a precise modeling parameter, provides information about the emergence of ISC and battery lifetime.

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