In-Operando Measurement of Temperature Gradients in Cylindrical Lithium-Ion Cells during High-Current Discharge

Abstract

The temperatures inside the jelly roll and on the surface of high-power 18650-type cells are investigated quantitatively. In-operando temperature measurements are conducted during discharge at rates in the range of 1C-12C. The experimental data are used to estimate local aging gradients inside the cell. The maximum temperatures on the cell housing and inside the jelly roll are correlated to the respective discharge currents, yielding clear linear dependencies over the whole current range. Using the collected data, a straightforward low-cost semi-empirical model is developed for prediction of the temperature rise inside cylindrical cells during discharge at different currents.Lithium-ion batteries are subject to aging reactions, which reduce their life-time. 1 Most of these aging reactions are accelerated by elevated ambient temperatures, following an Arrhenius-like behavior. 2,3 It is known from modeling studies that temperature gradients develop inside Lithium-ion batteries during operation. 4-6 Temperature gradients on the surface of Lithium-ion batteries have also been subject of measurements. [7][8][9] However, there is a lack of experimental data for temperatures inside Lithium-ion cells during operation. Such data would be very helpful for validation of models, prediction of aging gradients and thermal runaway prevention. Mutyala et al. developed a pouch cell with embedded temperature sensor. 10 The authors were able to measure a temperature rise during discharge and charge of this cell, however, they did not correlate it to other operating parameters. 10 Zhang et al. built 18650 cells with multiple embedded sensors to learn more about radial temperature distributions during discharge at rates lower than 3C. 11 We have recently shown that it is also possible to build a thermocouple inside the jelly roll of commercial 18650-type cells and measure the temperatures inside the jelly roll during discharge at rates as large as 16C. 12 In the present paper, we present in-operando temperature measurements inside the jelly roll of a commercial high-power 18650 cell during discharge at high currents. The data are used to estimate the magnitude of aging gradients in high-power cells. The maximum temperatures on the surface of the cell housing and inside the jelly roll are correlated with the discharge current. Finally, a straightforward semi-empirical model is presented to estimate the temperature rise in 18650 cells for a discharge with a sequence of different currents. ExperimentalCommercial 18650-type cells with a minimum rated capacity of 1.4 Ah were tested. The cells include a NMC/Mn-Spinel cathode and graphite anode. After discharging to 2 V by a constant current of 1A, a cell was opened inside an Ar-filled glove box and a temperature sensor was introduced into the cylindrical hole inside the jelly roll (see Figure 1b). Further details can be found in Ref. 12. The electrochemical tests were conducted by a Basytec XCTS system and a climatic chamber (Vötsch) held at 25 • C. Before each discharge step, the cells we...

Internal temperature prediction of Lithium-ion cell using differential voltage technique

“…The internal temperature of the cell also shows a similar trend albeit with a greater magnitude. In agreement with [14,15], the maximum difference (∆T) between the internal and measured temperatures over a discharge cycle is proportional to the corresponding C-rate. [15].…”

“…In agreement with [14,15], the maximum difference (∆T) between the internal and measured temperatures over a discharge cycle is proportional to the corresponding C-rate. [15]. The ∆T obtained in this paper for different operating conditions is slightly overstated as compared to [14] who only investigate temperature gradients on the surface, but is more in agreement with [15] who compared internal and surface temperatures.…”

“…This paper aims to use the DV technique to predict the 'effective resistance' of the cell for different continuous discharge currents at ambient temperatures between -20 and 25 o C, and thus, its internal temperature. Deviation between the internal and measured cell surface temperature is shown to vary directly with discharge current and declining ambient temperature [14,15]. These predictions may help improve control strategies within a battery management system (BMS) by improving accuracy of cell temperature estimation.…”

Large format lithium ion pouch cell full thermal characterisation for improved electric vehicle thermal management

“…As a consequence of thermal gradients, the cell does not age uniformly and an ageing gradient occurs inside the cell [29,30], reducing the efficiency and lifespan of lithium ion batteries. Strong thermal gradients can also lead to deformations of the jelly roll in cylindrical cells [22,31].…”

Simulation and Measurement of the Current Density Distribution in Lithium-Ion Batteries by a Multi-Tab Cell Approach

“…By monitoring 10 tab pairs at each edge of the single-layered NMC/graphite pouch cell, the quality and resolution in measuring local potentials 5 is maximized. Such a multi-tab cell can be used as measurement setup and validation tool for spatially resolved models in order to study effects related to electrode configuration and tab patterns, 6,[20][21][22][23] local relaxation processes 24,25 or local impedance effects. 3 Due to the specific cell design, any thermal gradient along the electrode can be avoided and, therefore, the superimposed effect of temperature inhomogeneity on cell performance is eliminated.…”