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Lithium Ion Battery Testing Using Adiabatic Calorimetry

Introduction

Batteries based on lithium ion technology provide several benefits in portable power applications, thanks to their superior performance aspects over other technologies. However, the possibility for thermal runaway to take place both under normal situations and in situations of mishandling is one of the key disadvantages of such energy storage devices and raises concern over their safety.

Contact of the highly reactive cell components with oxygen, short circuits, and overcharging are the damage mechanisms that have the potential to discharge the whole amount of energy stored in the device within a few minutes or even seconds. This may result in spontaneous increase in temperature. Moreover, combustion of the battery components may occur when they come into contact with oxygen due to mechanical damage. Hence, care must be taken to ensure the safety of such devices. This article discusses the application of adiabatic calorimetry to perform controlled penetration of a lithium ion cell (18650) with a nail inside the device.
Penetration Test Procedure

A special holder was designed to penetrate the 18650 cell that allowed a metal perforator to pierce the cell utilizing a compressed air control system. This results in an electrical short circuit because of the penetration of the metal perforator into the battery cylinder laterally, i.e., at right angle to the lithium ion cell’s layer structure. Subsequent to the penetration, the cell is opened, which makes the battery components that are sensitive to air to react with oxygen.

The holder for piercing the batteries was designed to perform this nail test inside the NETZSCH ARC 254 calorimeter. The objective is to determine the increase in pressure and temperature during penetration. However, some tests were also performed in a hood outside the calorimeter for demonstration purposes. The vertical, cylindrical penetration sample holder along with the horizontally fixated 18650 cell is depicted in Figure 1 (upper figure). A metal perforator placed in the center of the sample holder pierces the battery at the press of a button, thus causing abrupt destruction of the cell, as shown in Figure 1 (lower figure).
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