Abstract
Emulating true, field-like internal short-circuits (ISCs) by experimental methods is a complex task with mostly unsatisfactory outcome. However, understanding the evolution and impact of ISCs is crucial to mitigate safety issues related to lithium-ion batteries. Local short-circuit (LSC) conditions are applied to single-layered, small-sized (i.e. <60 mAh), and single-side coated graphite/NMC-111 pouch-type cells in a quasi-isothermal test bench using the nail/needle penetration approach. The cell’s impedance, capacity, and the contact resistance at the penetration site mainly define the short-circuit current and, hence, the terminal voltage and heat generation rate associated with polarization effects and electrochemical rate limitations, which are correlated to the cell’s behavior during external short-circuits (ESCs) at various short-circuit resistances. Measuring the electrical potential between the needle and the cell’s negative tab allows to evaluate the polarization across the electrodes and to estimate the short-circuit intensity. LSC simulation studies are used to correlate current flux and resistance to ESC conditions. Double-layered cells are penetrated to create short-circuit conditions within either a single or both electrode stacks to study the difference between multiple LSCs (e.g. during a nail penetration test) and a single LSC (e.g. due to a particle/dendrite). Post-mortem analysis reveals copper dissolution/deposition across both electrodes.
Highlights
On The Impact of the Locality on Short-Circuit Characteristics: Experimental Analysis and Multiphysics Simulation of External and Local Short-Circuits Applied to Lithium-Ion Batteries
We investigate the influence of the locality of the shorting scenario via triggering the short-circuit in the center of the electrodes using the nail/needle penetration technique and eventually compare the cell’s local short-circuit characteristics to its external shortcircuit behavior
The locality of the short-circuit defines the electrical behavior in the very beginning (i.e.
Summary
On The Impact of the Locality on Short-Circuit Characteristics: Experimental Analysis and Multiphysics Simulation of External and Local Short-Circuits Applied to Lithium-Ion Batteries. There is a strong need for relevant test scenarios simulating such triggers, which help understanding the underlying mechanisms in order to derive suitable means to mitigate or even rule out safety issues related to LIBs (e.g. shutdown separators,[14] integrated circuits,[15] pyrotechnical safety systems,[16] etc.) by increasing the battery’s tolerance toward ESCs and ISCs. On the one hand, ESC tests revealing a good reproducibility[17] and relevance for simulating realistic high current and abusive shortcircuit conditions applied via the terminals of a LIB. As an example for a typical, field-like ISC failure, metallic particle contamination, followed by dissolution and deposition including dendrite growth can lead to a local penetration of the separator and initiate a short-circuit.[18,19,20] In order to reproduce such a field-like shorting scenario, the test must trigger the shorting only at a single site, set a low ohmic resistance, form over time/operation of the LIB, and should reveal sufficient reproducibility.
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