Non-invasive measurement of internal temperature of a cylindrical Li-ion cell during high-rate discharge

Abstract

Li-ion cells are a technologically important class of devices for electrochemical energy storage and conversion. Overheating of a Li-ion cell during operation is undesirable as it directly affects performance and safety. Although a number of methods have been used for temperature measurement in Li-ion cells, there is a lack of non-invasive techniques to determine the peak temperature at the core of the cell. Measuring only the outside surface temperature, while straightforward, is not sufficient since the core temperature is in most cases much higher. This paper presents non-invasive measurement of the core temperature of a Li-ion cell using a recently developed technique that utilizes space and time integrals of the measured temperature field at the outside surface. The surface temperature field of an operating Li-ion cell is measured using infrared thermography at multiple discharge rates up to 10C, using which, the core temperature is predicted as a function of time. In each case, there is excellent agreement throughout the discharge period between the predicted core temperature and measurements from a thermocouple embedded at the core of the cell. These measurements quantify the temperature gradient within the cell, which is particularly high at large discharge rates. This paper may result © 2016. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ 2 in non-invasive core measurement methods that may contribute towards performance optimization and improved safety of Li-ion cells.

Experimental and numerical investigation of heat transfer in Li‐ion battery pack of a hoverboard

“…19 Section 4.4 later estimates the core temperature based on these measurements using a recently developed analytical model. 19,32 These experimental data establish the fundamental thermal benefit of using the air flow generated by hoverboard motion for cooling the battery pack. In harsh conditions, such as aggressive hoverboard operation in a high temperature ambient, the thermal benefit shown in Figure 5B may be sufficient enough to prevent thermal runaway or at least improve device reliability significantly.…”

“…Further, data reported here are all surface temperatures, whereas the core temperature may be much greater . Section later estimates the core temperature based on these measurements using a recently developed analytical model …”

“…Because of the hermetically sealed nature of a Li‐ion cell, most experiments, including those described in section , are able to report only the surface temperature measured by a thermocouple attached on the outer surface of the cell. Because of the low radial thermal conductivity of the cell, however, it is likely that the core temperature may be much greater and therefore may play a more significant role than the surface temperature in determining the safety of the cell . For example, when a surface temperature measurement indicates somewhat elevated temperature, the core temperature may in fact be much greater because of internal heat generation and large thermal conduction resistance within the cell.…”

“…Because of the low radial thermal conductivity of the cell, 9 however, it is likely that the core temperature may be much greater and therefore may play a more significant role than the surface temperature in determining the safety of the cell. 19,32 For example, when a surface temperature measurement indicates somewhat elevated temperature, the core temperature may in fact be much greater because of internal heat generation and large thermal conduction resistance within the cell. Therefore, thermal management decisions based on the surface temperature may not fully recognize the possibility of thermal runaway.…”

A review on various temperature-indication methods for Li-ion batteries

“…As with thermistors and RTD, commercial (micro) thermocouples are also used to measure the internal battery temperature [149,[222][223][224][225][226][227][228][229][230][231]. Although these measurements are useful for quantifying the internal temperature, either specially designed batteries with integrated sensors must be made, or a hole must be drilled into an existing (commercial) battery to insert a sensor.…”