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An Experimental Study of a Lithium Ion Cell Operation at Low Temperature Conditions

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Lithium-ion (Li-ion) batteries are widely used for various applications such as telecommunication, automotive, and stationary applications. With their wide range of safe operating temperatures (i.e. -10°C to 50°C), the Li-ion is preferred over other types of matured battery technologies such as lead acid and nickel-cadmium (NiCd). Nevertheless, operating the Li-ion batteries at cold climate conditions can potentially harm the batteries and lead to issues such as degradation and reduction in their capacity and power density. This paper aims to experimentally investigate the behavior of a Li-ion cell operating at low temperatures (i.e. -15°C to 25°C) with respect to its charging and discharging behavior. It was observed that at sub-zero temperatures (i.e. -5°C, -10°C and -15°C) the Li-ion cell's capacity is reduced due to the impedance effect which then increases the cell's internal resistance. Moreover, at such low temperatures the best state of charge (SOC) of the cell (i.e. during charging mode) has reduced to about 7-23% of its maximum initial SOC (i.e. 100%). To complement the experimental finding, an existing simplified adaptive thermal model was used to obtain the discharge curves at various current rates based on the function of extracted charge (Qout). The discharge curve of equilibrium potential (Eeq) is then extrapolated towards zero current in order to obtained the overpotential heat generation curve based on the discharge current of the cell. The result showed a good agreement to the discharge curves that were obtained experimentally. Likewise, with the finding of cell voltage (E), current (I) and temperature (T) that were obtained experimentally, the thermal behavior of the cell in respect of its internal temperature is predicted and represented by comparing both the simulated and experimental cell internal temperatures.
Content may be subject to copyright.
1876-6102 © 2017 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of the organizing committee of the 1st International Conference on Energy and Power.
doi: 10.1016/j.egypro.2017.03.117
Energy Procedia 110 ( 2017 ) 128 135
ScienceDirect
1st International Conference on Energy and Power, ICEP2016, 14-16 December 2016, RMIT
University, Melbourne, Australia
An experimental study of a lithium ion cell operation at low
temperature conditions
Asma Mohamad Aris
*
, Bahman Shabani
School of Engineering, RMIT University, Melbourne 3000, Australia
Abstract
Lithium-ion (Li-ion) batteries are widely used for various applications such as telecommunication, automotive, and stationary
applications. With their wide range of safe operating temperatures (i.e. -10 °C to 50 °C), the Li-ion is preferred over other types of
matured battery technologies such as lead acid and nickel-cadmium (NiCd). Nevertheless, operating the Li-ion batteries at cold
climate conditions can potentially harm the batteries and lead to issues such as degradation and reduction in their capacity and
power density. This paper aims to experimentally investigate the behavior of a Li-ion cell operating at low temperatures (i.e. -15
°C to 25 °C) with respect to its charging and discharging behavior. It was observed that at sub-zero temperatures (i.e. -5 °C, -10 °C
and -15 °C) the Li-ion cell’s capacity is reduced due to the impedance effect which then increases the cell’s internal resistance.
Moreover, at such low temperatures the best state of charge (SOC) of the cell (i.e. during charging mode) has reduced to about 7-
23% of its maximum initial SOC (i.e. 100%). To complement the experimental finding, an existing simplified adaptive thermal
model was used to obtain the discharge curves at various current rates based on the function of extracted charge (ܳ௢௨௧). The
discharge curve of equilibrium potential (ܧ௘௤) is then extrapolated towards zero current in order to obtained the overpotential heat
generation curve based on the discharge current of the cell. The result showed a good agreement to the discharge curves that were
obtained experimentally. Likewise, with the finding of cell voltage (ܧሻ, current (ܫሻ and temperature (ܶሻ that were obtained
experimentally, the thermal behavior of the cell in respect of its internal temperature is predicted and represented by comparing
both the simulated and experimental cell internal temperatures.
© 2017 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the organizing committee of the 1st International Conference on Energy and Power.
Keywords: Lithium ion; batteries; cold climatre condition; charging; discharging; heat transfer; theoretical modelling
* Corresponding author. Tel.: +6-139-925-6138; fax: +6-139-925-8099.
E-mail address: asmamohamadaris@gmail.com
Available online at www.sciencedirect.com
© 2017 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of the organizing committee of the 1st International Conference on Energy and Power.
Asma Mohamad Aris and Bahman Shabani / Energy Procedia 110 ( 2017 ) 128 – 135 129
1. Introduction
Advanced lithium ion (Li-ion) battery technology is now broadly used in a range of applications such as
telecommunication, personal transportation (e.g. e-bikes and scooters), automotive, aerospace, grid, and stationary
applications [1-7]. With its wide range of safe operating temperatures (i.e. -10 °C to 50 °C), the Li-ion batteries have
gained distinction that is comparable to other types of matured battery technologies such as lead acid and nickel-
cadmium (NiCd) batteries [8]. Nevertheless, unlike the simplicity of deploying lead acid battery, the Li-ion batteries
require electronic control circuitry to maximize their performances and reinforce their safety that are very important
in applications such as telecommunication and electric vehicles (EVs) [2].
In recent years, the thermal management of Li-ion batteries has been the focus of a number of studies as it is a
crucial consideration to get them operated at optimum conditions. While both cooling and heating are equally critical,
the emphasis of recent studies were mainly towards high temperature applications (e.g. for EV operation in hot climate
condition or for remote area power supply (RAPS) system at desert area) with noticeably less attention to their
operation in low temperature climate conditions (i.e. particularly for stationary applications). This calls into question
on issues relating to the effect of low temperature operation on the performance of Li-ion batteries: for instance reduced
energy and power densities of the batteries [9]. It is noteworthy that the Li-ion batteries operate at the same temperature
range of human’s tolerable range; however, both the high and low temperatures can greatly reduce their performances
while overheating can lead to safety issues such as thermal runaway and explosions [10].
As reported by Gering [11], the limitations of the Li-ion batteries can be put into two categories of intrinsic and
operational limitations. The intrinsic limitations are due to unavoidable materials-related constraints that are
irrespective to the battery usage condition. Examples of the intrinsic limitations include transport characteristics of the
electrolyte, charge transfer rates within the electrode materials, and others. Meanwhile, the operational limitations are
related to how actively a cell is being cycled under specified state of charge (SOC) and temperature [11]. Hence, it is
known that the challenges faced by the Li-ion batteries at low temperature conditions are clearly related to the
operational limitations.
Previous research studies have shown that rapid charging of the Li-ion batteries at subzero temperatures can
potentially harm the batteries and lead to their degradation [12]. For example the capacity of the Li-ion batteries is
greatly reduced as much as 95% when operated at -10 °C rather than at 20 °C [13]. This drop in the capacity is
unacceptable in many applications when the Li-ion battery storage system fails to meet the load demand due to aging
behavior associated with their operation at extreme cold conditions. It was suggested that such occurrence of
performance loss at cold conditions is caused by a significant rise of internal resistance that tends to increase the cell’s
internal temperature (warming the cell) and potentially degrade the Li-ion in the long run [14, 15]. Hence, among the
efforts suggested to improve the Li-ion’s performance are advanced thermal behavior study, upgraded electrode
materials, improved charging/discharging arrangement and comprehensive battery’s thermal management [16-20].
In this paper, the behavior of Li-ion cells is studied based on charging and discharging of the cell at various low
operating temperatures. The results of this experimental study will then be used to establish the reliability of an existing
simplified thermal model used to predict the performance of Li-ion batteries operated under various temperatures. A
small-scale experimental study was carried out on a Li-ion cell at operating temperature ranging between -15 °C to 25
°C. The manufacturer’s recommendation of current rate (C-rate) values (i.e. 20C for charging and 5C for discharging)
are used to identify the effect of the battery’s temperature on its performance.
Nomenclature
݉ Mass of cell (g)
ܥ Specific heat capacity (J.g-1.K-1)
ܳ
௜௡ All processes that generate heat (W)
ܳ
௢௨௧ All processes that dissipate heat (W)
Overpotential heat generation (W)
Entropic heat generation (W)
Heat convection (W)
Heat radiation (W)
130 Asma Mohamad Aris and Bahman Shabani / Energy Procedia 110 ( 2017 ) 128 – 135
ߟ Total overpotential (V)
ߟ Ohmic losses in cell (V)
ߟ Diffusion and migration of Li-ion through the electrolytes (V)
ߟ Diffusion of Li-ion cell inside the electrodes (V)
ߟୡ୲ Charge transfer reactions at the electrode (V)
Cell voltage (V)
ୣ୯ Equilibrium potential (V)
Current (A)
௢௨௧ Extracted charge from the cell (Ah)
ݐ Time (s)
ݐୣ୬ୢ Time at end of discharge (s)
݄ Convective heat transfer coefficient (W.m-2.K-1)
ܣ External surface area of the cell (m2)
ܶ Surface temperature of cell (K)
ܶ
Ambient temperature (K)
ߪ Stefan-Boltzmann constant (W.m-2.K-4)
ߝ Emissivity
2. Experimental Study
2.1. An Overview
An experimental investigation was conducted to test the performance of three 3.7 V 1500 mAh rechargeable Li-
ion polymer cells based on a specified temperature range of -15 °C to 25 °C. A climatic chamber was used to recreate
the cold climate conditions where the tested cells were placed in the chamber for capacity measurement during
charging and discharging. A recommended C-rate value (i.e. 5C for discharge and 20C for charge) by the Li-ion cell’s
manufacturer was selected as the charging and discharging rate in order to minimize the risk of cell’s damage and
explosion. Table 1 shows the specifications of the Li-ion batteries used in the experiment. To observe the cell behavior
when operating at low temperature, a series of procedure is applied to the experimental setup with the objective of
investigating the effect of low temperature operation to the Li-ion cell’s performance. The details of this setup are
shown in Fig. 1.
Table 1. The specifications of the Li-ion batteries used in the experiment.
Type
Nominal
Capacity (Ah)
Nominal
Voltage (V)
Upper cut-off
voltage (V)
Lower cut-off
voltage (V)
Operating
temperature
Li-ion polymer cell
1.5
3.7
4.2
3.2
-30 °C ~ 60 °C
The procedures undertaken for conducting this experimental study are as follows:
x Step 1: The temperature of climatic chamber temperature (Tamb) was set to a designated testing temperature
(Ttest).
x Step 2: The Li-ion cells were placed in the climatic chamber until it reaches thermal equilibrium that was
when the temperature of the cell (Tcell) was measured to be the same as the Ttest.
x Step 3: The Li-ion cells were discharged from maximum state of charge (SOC) to their cut-off voltage of
3.2V. Throughout this phase, the increase in the internal temperature of the cell indicated a heat generation
due to the electrochemical reaction within the cell. The Tcell was recorded during the test.
x Step 4: Once the discharge cycle was completed, the cells were rested until they reached 25 °C (i.e. the
assumed Tamb). To ensure identical SOC in different tests of the Li-ion cells they were left rested overnight.
Before the start of the experiment
x Step 5: The charge cycle was continued until the cell’s voltage reached its maximum value of 4.2 V.
Asma Mohamad Aris and Bahman Shabani / Energy Procedia 110 ( 2017 ) 128 – 135 131
Fig. 1. (a) Schematic diagram of experimental setup; (b) Climatic chamber used for testing; (c) Type of rechargeable Li-ion polymer cell used in
testing
2.2. Effects of Li-ion Cell Performance
To understand the behavior of the Li-ion cell used for this study, the experimental data has been analyzed as a
series of plotted curves. The effects of temperature on charging/discharging characteristics of the Li-ion cell are
presented in Fig. 2. In Fig. 2 (a), the charge voltage profiles of a Li-ion cell at various testing temperatures (i.e. Ttest.
= -15 °C to 25 °C) and at a constant charging current of 1 A are shown respectively while Fig. 2 (b) shows the
discharging characteristics at a constant current of 0.25 A in different temperatures. From the curves, the cell delivers
substantially less capacity at subzero temperatures during both charging and discharging modes as compared to that
at ambient temperatures of 15 °C and 25 °C.
Fig. 2. (a) Charge-temperature characteristics of a Li-ion cell at 20C rate; (b) Discharge-temperature characteristics of a Li-ion cell at a 5C rate
In Fig. 3 (a), the effect of temperature on the Li-ion cell when charging at subzero temperatures (i.e. -5 °C, -10 °C
and -15 °C) is plotted with respect to the SOC of the cell. From the curves, lower temperatures affect the cell’s capacity
significantly by dropping its SOC from 100% (initial testing) down to about 93%, 88% and 77% at -5 °C, -10 °C and
-15 °C respectively. Moreover, the same trend can be also presented during discharging of the cell at subzero
temperatures, where the cell capacity reduces to 92%, 85% and 82% of the cell’s depth of discharge (DOD) at -5 °C,
-10 °C and -15 °C respectively (Fig. 3 (b)). This loss of capacity is mainly due to the increase of internal resistance
that causes some warming effect to the cell during charging and discharging [20].
132 Asma Mohamad Aris and Bahman Shabani / Energy Procedia 110 ( 2017 ) 128 – 135
Fig. 3. The effect of temperature on a Li-ion cell SOC and DOD when: (a) charging at sub-zero temperature (i.e. -5 °C, -10 °C and -15 °C) based
on Li-ion cell SOC; (b) discharging at sub-zero temperature (i.e. -5 °C, -10 °C and -15 °C) based on Li-ion cell DOD
Table 2 presents the temperature difference between the maximum and minimum cell internal temperature when
operating at 25 °C, -5 °C, -10 °C and -15 °C. It can be observed that the experimental finding has a good agreement
with the effect of low temperature operation increases the cell internal temperature. Prolong of the low temperature
operations can potentially lead to reduced lifetime of the cell; in which the temperature difference (ΔT) is
recommended to be below 5 °C [5, 21].
Table 2. Temperature difference between the battery and its surrounding ambient for charge and discharge of a Li-ion cell operated at sub-zero
temperatures.
Discharge
Testing
Temperature
(Ttest)
Min.
Temperature
Max.
Temperature
Temperature
Difference (ΔT)
SOC
Min.
Temperature
Max.
Temperature
Temperature
Difference (ΔT)
DOD
25 °C
23.6 °C
25.9 °C
2.3 °C
100%
24.9 °C
27.7 °C
2.8 °C
100%
-5 °C
-5.0 °C
-1.7 °C
3.3 °C
93%
-5.1 °C
-0.5 °C
4.4 °C
92%
-10 °C
-10.0 °C
-6.0 °C
4.0 °C
88%
-10.1 °C
-6.0 °C
4.1 °C
85%
-15 °C
-15.8 °C
-10.4 °C
5.4 °C
77%
-15.8 °C
-10.3 °C
5.3 °C
82%
3. Theoretical Study
3.1. An Overview
A numerical modeling can be applied parallel to the experimental study as a hybrid approach in predicting the
thermal behavior of Li-ion cell under different thermal conditions. In this study, an existing simplified adaptive
thermal model that was developed by Rad, Danilov, Baghalha, Kazemeini and Notten [22] is used to establish the
reliability of the experimental finding. The assumptions made when deploying the model is that the internal
temperature and heat generation of the cell are uniform. Based on the general energy balance equation represented as
equation (1), the processes that contribute to the heat evolution comprise of heat generation, ܳ
௜௡ (i.e. Ohmic heat,
irreversible heat and reversible heat) and heat transfer, ܳ
௢௨௧ (i.e. heat convection and heat radiation from the outer
surface of the cell) [5, 23]. However for simplification of this study, only ܳ is taken into consideration when
quantifying the heat generation of the cell due to its substantial source of heat generation inside the cell.
݉ܥ
ௗ்
ௗ௧ ൌሺܳ
൅ܳ
ሻെሺܳ
൅ܳ
(1)
Asma Mohamad Aris and Bahman Shabani / Energy Procedia 110 ( 2017 ) 128 – 135 133
Fig. 4. (a) Discharge curves at various current; (b) Overpotential heat generation curves of a Li-ion cell at various discharge currents
Based on the experimental findings, the cell voltage (ܧሻ, current (ܫሻ and temperature (ܶሻ can be derived and
represented as equilibrium potential (ܧ௘௤ at each SOC and temperature. The difference from ܧ and ܧ௘௤ indicate the
overpotential (Ʉ) in which the overpotential heat generation () can be calculated by multiplying with applied
current [5]. Equation (2) defined the various heat generations inside the cell. The total overpotential heat generation
(ܳ) can be calculated using equation (3).
ߟൌܧെܧ
௘௤ ൌߟ
൅ߟ
൅ߟ
൅ߟ
௖௧ (2)
ܳൌ݊
ܫ (3)
Fig. 4 (a) illustrates the discharge curves at various current rates based on the function of extracted charge (୭୳୲).
The ܧ௘௤ is determined by generating the discharge curves and extrapolating it towards zero current as suggested in [5,
22], in which the curve is represented as the Electromotive Force (“EMF”) line. By using the “EMF” curve and by
incorporating it into equation (3), the overpotential heat generation curves at various discharge currents are plotted for
every DOD (Fig. 4 (b)).
Once the overpotential heat generation is known, the energy balance equation (equation (1)) can be solved.
Moreover, to further predict the thermal behavior of the Li-ion cell with respect to its internal temperature, solving
the energy balance equation can be done by assuming the entropy contribution to be negligible [22]. By calculating
the total heat dissipation and rearrange the equations, the prediction of cell internal temperature can be computed in
order to confirm the experimental data of Li-ion cell internal temperature. Fig. 5 shows the comparison between
experimental and simulated Li-ion cell internal temperature for three subzero testing temperatures (i.e. -5 °C, -10 °C
and -15 °C).
ܳൌ݄ܣܶെܶ
(4)
ܳߪߝܣሺܶെܶ
(5)
134 Asma Mohamad Aris and Bahman Shabani / Energy Procedia 110 ( 2017 ) 128 – 135
Fig. 5. Comparison of experimental and simulated internal temperature of Li-ion cell at constant discharge current for testing temperature of (a)
-5 °C, (b) -10 °C, and (c) -15 °C
4. Conclusion
An experimental study relating to Li-ion batteries has been conducted based on their operations at cold climate
conditions. Evidently, the relation between the cell’s internal temperature in addition to electrochemical and thermal
processes was established based on the temperature rise effect in the Li-ion cells. In order to confirm the experimental
findings based on a certain degree of reliability, a simplified adaptive thermal model was used. The finding comes to
a good agreement that reduced capacity of the cell is affected by low temperature and high current operations.
Although in reality, the thermal analysis is more complex than what is presented here but for simplification purpose,
the quantification of the overpotential heat generation is done as it is the most substantial heat generation yield by the
Li-ion cell. Likewise, by using the energy balance equation, the thermal behavior of the Li-ion cell was predicted for
discharging at subzero temperatures. The result showed that the simulated internal temperature of the cell was much
lower than the experimental one when the model does not take into consideration the entropy effect. Thus, it is clear
that the correlation between the experimental and theoretical findings lies on the operating temperature, current and
voltage of the cell and that the cell chemistry have their effects on these parameters as well. For future works, a more
complex thermal model will be developed further in order to comprehensively model the thermal behavior of the Li-
ion cell with the aim of understanding the performance of the cell at low temperature operations.
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... Studies by Fetene et al. [60], based on big data analysis, revealed how strongly the energy consumption rate (ECR) of EVs varies highly and nonlinearly with driving patterns and weather conditions. The analysis of the impact of temperature on the energy efficiency of EVs was analyzed for many parts of the world, like Kuwait (Hamwi et al. [61]), the United States (Yuksel and Michalek [62]), and Alaska (Wilber et al. [63]), both for variable temperature conditions and for high temperature (Jeffers et al. [64] and Ma et al. [65]) and low-temperature conditions in winter (Hajidavalloo et al. [66], Smith et al. [67], and Aris and Shabani [68]). ...
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