A new method of thermal runaway warning for lithium-ion batteries using the swelling force

doi:10.21203/rs.3.rs-2824070/v1

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A new method of thermal runaway warning for lithium-ion batteries using the swelling force

https://doi.org/10.21203/rs.3.rs-2824070/v1

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The thermal runaway process of a battery is accompanied by changes in the characteristic parameters, including the battery voltage, temperature, internal resistance, gas, smoke, and swelling force, which provide many options for the early warning of battery thermal runaway. Among the various feasible warning methods for thermal runaway, the method of swelling force may have distinct advantages in advance warning and warning reliability. In this paper, commercial lithium iron phosphate/graphite and ternary/graphite batteries were used as the research objects. The patterns of the change of the swelling force with voltage, temperature, and other parameters were compared, and the results showed that the change of the swelling force during thermal runaway was higher than that during normal charging and discharging. Moreover, the time when the change of the swelling force in the thermal runaway process exceeded the change under normal working conditions was earlier, so an earlier warning could be achieved. In addition, compared with the temperature signal, the collection of the swelling force signal was more convenient. In summary, this paper provides a feasible and fast method for the early warning of battery thermal runaway, which has high engineering significance for improving the safety of electric vehicles.

Physical sciences/Engineering/Mechanical engineering

Physical sciences/Energy science and technology/Energy storage/Batteries

Lithium-ion battery

Early warning

Swelling force

Thermal runaway

1. Swelling force during normal operation and thermal runaway is analysed.

2. Analysis was conducted on batteries with two different material systems.

3. New method for thermal runaway warning using swelling force is proposed.

4. Safety warning using swelling force has advantage in identification and advance.

To solve the problems of fossil energy shortages and air pollution, in the past ten years, electric vehicles have been greatly developed in China [1][3]. In 2020 and 2021, China’s electric vehicle sales reached 1.36 and 2.26 million, respectively, and China is the world’s largest electric vehicle market. According to the plan issued by the government, China’s electric vehicle sales will strive to account for 20% of total vehicle sales by 2025 [4].

However, the number of fire accidents of electric vehicles has grown in recent years, which has become an important obstacle to the large-scale application of electric vehicles [5]. According to the comprehensive analysis of electric vehicle fire accidents and their possible causes, electric vehicle fire accidents have the following typical characteristics: (1) the vehicle models are diverse, covering passenger cars, electric buses, special vehicles, and other types of vehicles; (2) accidents are highly correlated with the season, and the summer has a high rate of accidents; (3) the specific cause of the fire is often vague, as evidence is destroyed as the vehicle burns, and it is difficult to accurately locate the source of the accident; (4) accidents are highly correlated with power batteries. As the power source of electric vehicles, power batteries are directly related to a large proportion of electric vehicle fire accidents.

For the abovementioned electric vehicle fire accidents caused by the thermal runaway of power batteries, the typical process usually mainly includes three stages: accumulation of the factors that cause thermal runaway of the battery cell, occurrence of the thermal runaway of the battery cell, and thermal runaway propagation of the battery system [6][7]. To improve the safety of the power battery system, the above three stages must be monitored and controlled step by step. One of the most important links is to provide an accurate warning when battery runaway occurs and give clear signals to the occupants to provide enough time to deal with the vehicle and escape. In the process of battery thermal runaway, the changes in the battery voltage, temperature, internal resistance, gas concentration, pressure, and swelling force provide a basis for battery thermal runaway warning [8][9]. Based on quantitative tests of the critical conditions of battery thermal runaway, battery thermal runaway warning is currently realized by adopting one or a combination of the above-mentioned thermal runaway parameters. Conventional thermal runaway warning methods are mainly based on voltage and temperature signals. For example, in the first-stage draft of the Global Technical Regulation on the Electric Vehicle Safety (EVS GTR) [10], it is recommended to use a combination of the voltage change, maximum temperature, and temperature variation rate (1°C/s) as a warning. To allow the use of temperature as an effective advanced thermal runaway warning, Li et al. [11] used a resistance temperature detector to collect the temperature of the battery current collector. The results showed that the temperature detected using this method was higher than the battery case temperature detected by the temperature sensor, and the detection speed was 10 times faster. When battery thermal runaway occurs, due to the decomposition of the electrolyte and various side reactions between the electrolyte and the positive and negative pole materials, various gases, such as CO and H₂, are generated, which provides a relatively reliable method for thermal runaway warning. Zhang et al. [12] used a pressure-resistant pyrolysis autoclave and a gas chromatography–mass spectrometer to study the pattern of gas production of the electrolyte at different thermal decomposition temperatures, heating durations, and oxygen concentrations. They also found that for lithium-ion batteries with different positive-pole and negative-pole active materials but with the same electrolyte composition, the composition of the main gas released during heating or overcharging was very similar to that of the gases produced by the thermal decomposition of the electrolyte. For lithium-ion batteries whose electrolyte was the LiPF6 + EC/DMC system, CO, CO₂, C₂H₄, C₂H₆O, and C₂H₄O₂ could be selected as characteristic gases for safety warning. The principle of the warning based on the smoke signal was similar to the principle of the warning based on a signal of the special gas concentration. Koch et al. [9] conducted studies on the gas and smoke signals of soft-pack batteries during thermal runaway. The research results showed that the detection of smoke was easily affected by signal reflections by objects in the environment, location, and other factors, resulting in low signal quality, and the gas signal was a relatively feasible means for warning. Researchers have also suggested that to achieve a reliable warning, it is often not sufficient to use only one signal, and a combination of several signals will be more effective. It should be noted that for the thermal runaway warning method that uses the gas composition and smoke signals, it is possible to detect the signal only when the battery has apparent leakage (i.e., for a soft-pack battery, the aluminum–plastic film is cracked; for a hard-case battery, the safety valve is opened). That is, when the battery reaches the warning condition, the battery has already experienced significant thermal runaway. At this time, the time left for the battery thermal management system to actively dissipate heat and remind passengers to escape will be extremely limited.

For this reason, researchers have attempted to develop new test methods to obtain the internal parameters of the battery to achieve an earlier warning for thermal runaway. Raghavan et al. [13][14] proposed an embedded optical fiber sensor to test the internal pressure and temperature of the battery. The principle is that when the internal temperature or pressure of the battery changes, the refractive index of the optical fiber sensor will change, and the corresponding reflected light wavelength will also change. Srinivansan et al. [15][16] proposed a thermal runaway warning method for lithium-ion batteries based on impedance monitoring. The results of the study found that in the early stage of lithium-ion battery thermal runaway, the impedance phase shift was abnormal. At this moment, the battery temperature changed slowly, and the voltage had no apparent change. Thus, using the change in the characteristic value to provide a thermal runaway warning is feasible. In terms of warning signal research for battery thermal runaway, the most systematic and comprehensive study was conducted by Koch et al. [9]. In addition to voltage, temperature, gas composition, and smoke signals, the research team also analyzed the changes in the creep distance and the swelling force of the soft-pack battery during thermal runaway. By comparing the detection speed, signal clarity, and sensor feasibility level of various warning signals, the researchers suggested that the gas concentration, gas pressure, and swelling force are the three most sensitive parameters in terms of the detection speed. The abovementioned tests were carried out for soft-pack batteries, and thus, further research is still needed for square batteries.

This paper compares and examines the changes in the swelling forces of lithium-ion batteries during the processes of temperature rise, normal charge and discharge, and thermal runaway. Based on this, a new method using the swelling force as a warning for battery thermal runaway is proposed. The paper is mainly composed of the following sections. The first section is the experimental section, which introduces the test samples, the overcharge and heating thermal runaway test procedures, and the devices and methods used for collecting signals (voltage, temperature, and swelling force). The second section discusses the changes in the pressure, temperature, and swelling force of the battery under normal working conditions and the process of thermal runaway, and the feasibility and main advantages of using the swelling force for battery thermal runaway warning are analyzed.

One lithium iron phosphate/graphite system and one ternary material/graphite system battery were selected as the research objects. The main technical parameters of the samples are shown in Table 1. The energy density test conditions listed in the table were for discharging at a constant current discharge (1 C) at 25°C.

Table 1

Main technical parameters of the research objects
Item	Parameter
Item	Cell 1	Cell 2
Material type	Ni0.5Co0.2Mn0.3/Graphite	LFP/Graphite
Battery type	Rectangular	Rectangular
Length×Width×Height / mm	26.5×148×91	119.4×173.0×19.5
Rated voltage / V	3.65	3.20
Rated capacity / Ah	37	25
Terminal charge voltage / V	4.20	3.80
Terminal discharge voltage / V	2.80	2.00
Specific mass energy density / Wh/kg	173.59	105.29
Specific volume energy density / Wh/L	397.76	201.19

For the samples shown in Table 1, before the thermal runaway test, the battery was discharged by constant current discharging at 1 C, and then the battery was charged by constant current charging at 1 C. After reaching the cut-off voltage, the battery was switched to constant voltage charging until the current was 0.05 C. Through this step, the battery state of charge (SOC) was adjusted to the full state.

The overcharge and heating methods were used to conduct thermal runaway tests on the battery, and the changes in the parameters, such as the voltage, temperature, and swelling force of the battery during the process, were obtained. The voltage and temperature signals were collected by a voltage sensor and a temperature sensor (Omega K-type thermocouple with a maximum measurable temperature of 1000 ℃ and measuring error of ± 0.5 ℃) coupled with a data acquisition system, respectively. For the test of the swelling force signal, the battery was placed in the fixture shown in Fig. 1. The clamp was mainly composed of three clamping plates, of which the upper and lower clamping plates were fixed, and the upper and lower sides of the middle clamping plate were in close contact with the battery and the pressure sensor, respectively. When the battery expanded or contracted, the force was transmitted to the sensor by pushing and moving the middle clamping plate. Before the start of the experiment, the initial value of the battery swelling force was set to 1000 N.

In the overcharge test, the positive and negative poles of the battery were connected to the charging and discharging devices, and the battery was overcharged with a 2 C current to simulate the abuse of the battery management system (BMS) of the electric vehicle battery system when a functional safety failure or a voltage signal acquisition failure occurred. In the external heating thermal runaway test, an electric heater was used to heat the battery to simulate the self-heating-runaway-induced heat diffusion scenario caused by the internal defects of some battery cells in the electric vehicle battery system. As shown in Fig. 1, the electric heater was powered by a programmable power supply, and the heater power was set to 800 W. The electric heater also had a square shape. The material was cast iron, which is not prone to thermal deformation, and an electric heating wire was installed inside.

Under the overcharge or heating trigger condition, when the triggered battery exhibited apparent thermal runaway characteristics (as shown in Fig. 2), charging or heating of the battery was stopped. Throughout the process, the battery cell voltage, temperature, and swelling force during the process (sampling frequency was 100 Hz) were recorded, and the battery changes were observed through the camera. When battery runaway occurred, the data acquisition device remained operating continuously until the runaway phenomenon no longer occurred. When the temperatures tested by all the temperature sensors were lower than 50°C, the data recording was stopped.

3.1 Changes in swelling force under normal working conditions of battery

In addition to the change in the swelling force of the battery in the process of thermal runaway, the swelling force also changed due to thermal expansion and contraction caused by temperature changes or normal charge and discharge.

The charging and discharging of lithium-ion batteries correspond to reversible processes of lithium intercalation and deintercalation of the positive and negative electrodes. Therefore, the change in the swelling force during the charge and discharge process is mainly due to the difference in thickness of the positive and negative electrodes during the lithium intercalation and deintercalation processes. Overall, the swelling force of the battery increases during charging, while the swelling force decreases during discharging. For batteries with different material systems, there are certain differences in the pattern of the swelling force with the SOC. For the lithium iron phosphate/graphite system battery, the pattern of change was relatively complicated. The positive electrode material did not contract significantly in the early stage of charging, while the graphite negative electrode expanded substantially. So, the swelling force showed an increasing trend. In the middle of charging, the positive electrode material contracted, and the extent was greater than the expansion of graphite, so the swelling force showed a downward trend. In the late stage of charging, the positive electrode material no longer contracted, but the graphite continued to expand, and the swelling force increased again. For the ternary/graphite system battery, the positive electrode material possessed a hexagonal crystal system, and its unit cell volume changed slightly during the charging and discharging processes. The volume change during the charging process mainly arose from the expansion of the negative electrode, so the swelling force during the charging process showed an increasing trend. In summary, for the lithium-ion battery of a specific system, it is first necessary to calibrate the change of the swelling force under the normal working state of the battery.

The swelling force of the battery was first calibrated during charging and discharging. The constant current and constant voltage (CC-CV) charging conditions were as follows: charging was carried out with a constant current at 2 C under a constant temperature of 25°C. When the battery charging cut-off voltage was reached, it was switched to constant voltage charging, and charging was stopped until the charging current dropped to 0.05 C. Figure 3 shows the changes of the ternary material/graphite and lithium iron phosphate/graphite battery in the voltage, temperature, and swelling force during this process, respectively.

As shown in Fig. 3(a), the change in the swelling force of the ternary material/graphite battery during the charging process was 333 N, and the change in the swelling force could be divided into three typical stages based on the rate of increase, which is below 0.4 N/s during the whole process. In the first half of the constant current charging (SOC = 0–0.6), the battery temperature increased at a rapid rate, but the swelling force increased at a relatively slow rate during this process, only increasing from 750 to 820 N. In the second half of constant current charging, the swelling force increased at a faster rate, from 820 to 980 N. The main reason for this change was that in the initial stage of discharge, there was enough space inside the negative electrode to accommodate lithium-ions, and the swelling effect caused by lithium intercalation was small. With increasing SOC, the expansion effect of lithium intercalation in the negative electrode was more significant. After entering the constant current charging stage, the temperature of the battery gradually dropped because the external heat dissipation was greater than the heat produced by the battery itself. The swelling force continued to increase, but the rate of increase decreased to some extent. This was mainly due to the significant decrease in the number of lithium-ions intercalated into the negative electrode per unit time in the constant pressure stage. For the lithium iron phosphate/graphite battery, the change of expansion force during charging shows more complex characteristics. However, the change in expansion force is within 300N and the rate of change is within 0.5N/s, which is similar to that of the ternary material/graphite battery.

The change in the battery temperature in the above process would also cause the thermal expansion of the battery and then lead to a change in the swelling force, but this effect was small. Figure 4 shows the changes in the temperature and swelling force of of the lithium iron phosphate/graphite battery as the temperature in the test chamber increased from 25 to 45°C and then further to 65°C. In this process, the battery was not charged and discharged, and the experiment was only used to investigate the influence of the temperature on its swelling force. The change in the swelling force of the battery during the whole process was only 30 N, which was considerably smaller than the change in the swelling force in Fig. 3. The change in the swelling force of the battery during the charging process mainly arose from the change in thickness of the positive and negative electrodes caused by the intercalation and deintercalation of lithium-ions because the thermal expansion caused by the temperature rise was not the main factor.

For constant current discharge, the working conditions were as follows: discharging was carried out by constant current discharge at 2 C under a constant temperature of 25°C and was stopped when the battery discharge cut-off voltage was reached. Figure 5 shows the changes of the lithium iron phosphate/graphite battery in the voltage, temperature, and swelling force during this process. In contrast to the charging process, in the first half stage of discharge (i.e., the state of higher SOC), the swelling force decreased rapidly during the battery discharging process. At the end of the discharge process, the rate at which the swelling force decreased gradually slowed. The change in the battery swelling force during the entire discharge process was 500 N.

Based on the findings above, the change in the swelling force of the battery under normal working conditions was calibrated. In the following sections, the change in the swelling force of the battery under overcharge- and heating-induced thermal runaway is studied, and the feasibility of using the swelling force as a signal for thermal runaway warning is explored.

3.2 Change in swelling force of battery during thermal runaway

When battery thermal runaway occurs, the battery generated gases due to various internal decomposition and mutual reactions, which caused the internal pressure of the battery to increase sharply. When the internal pressure of the battery was less than the opening pressure of the pressure relief valve of the square or cylindrical battery and the rupture pressure of the aluminum–plastic film of the soft-pack battery, the external swelling force increased continuously, which provides the possibility for using the external swelling force for battery thermal runaway warning.

Figure 6 shows the changes in the temperature and swelling force during the overcharge-induced thermal runaway of the lithium iron phosphate/graphite battery. After the start of the experiment, with the slow rise of the battery voltage, the battery swelling force increased rapidly, the variation range and changing rate of swelling force reached 1500 N and 10 N/s respectively within 150 s, and the battery temperature was only 27°C at that time. When the pressure relief valve was opened, the swelling force reached its maximum value. After the pressure relief valve was opened, the swelling force of the battery was considerably reduced. Due to the continuous occurrence of various side reactions inside the battery, large quantities of gas and smoke were generated, and the swelling force was maintained at about 2800 N. When the battery was completely disconnected, the temperature did not continue to rise, the voltage dropped to zero, and the swelling force gradually disappeared and dropped to zero. The change of the battery swelling force during the whole process was 5477 N. By comparing the changes in the signals, such as the battery voltage, temperature, and swelling force, it is evident that the time when the swelling force started to increase dramatically was earlier than that when the temperature change occurred. When the change was far beyond the range of change in the swelling force corresponding to normal charge and discharge (the change value and changing rate were set to 1500 N and 10 N/s, respectively), there was still 150 s before battery thermal runaway occurred. Therefore, the change of the battery swelling force could be used as a warning of battery thermal runaway.

Figure 7 shows the changes in the temperature and swelling force during the overcharge-induced thermal runaway of the ternary/graphite battery. After the start of the experiment, with the slow rise of the battery voltage, both the swelling force and temperature of the battery began to increase. The increase range and changing rate of swelling force reached 1500 N and 2.6 N/s respectively within 650 s, and the battery temperature was only 24°C at this time. When the pressure relief valve was opened, the swelling force reached the maximum value of 4958 N. After the pressure relief valve was opened, the swelling force of the battery gradually decreased. After a period of time, the swelling force dropped to zero. This process was accompanied by a gradual decrease in the battery temperature. The change of the battery swelling force during the whole process was 4164 N. Similar to the lithium iron phosphate/graphite system battery, the time when the swelling force started to increase dramatically was earlier than that when the temperature change occurred. When the change exceeded the range of change of the swelling force corresponding to normal charge and discharge (similarly, the change value and changing rate were set to 1500 N and 2.6 N/s, respectively), there was still 260 s before battery thermal runaway occurred, which was sufficient to provide an effective early warning of battery thermal runaway.

Furthermore, the changes in the temperature, voltage, and swelling force of the ternary material/graphite battery during heating-induced thermal runaway were studied, as shown in Fig. 8. After the start of the experiment, under the action of the external electric heater, the battery swelling force increased rapidly along with the increasing battery temperature, and it increased at a faster rate after the experiment ran for 400 s. The change of the swelling force exceeded 1500 N after 510 s with a changing rate of 6.25 N/s, and the battery voltage still did not change. At 602 s, the battery voltage changed to 0 V due to an internal short circuit. The time when the swelling force began to increase considerably was earlier than that when the voltage change occurred. When the change exceeded the range of change of the swelling force corresponding to normal charge and discharge, there was still 92 s before the internal short circuit occurred in the battery, so the change of the battery swelling force could be more effective as a warning of battery thermal runaway than the voltage and temperature.

As shown in Table 2, before the safety valve was opened, the change in the swelling force during battery failure was between 4 and 5 kN, which was 10 times greater than the change of the swelling force during normal battery charge and discharge. Also, the force rising rate during thermal runaway is also far higher than that during normal operating conditions. Therefore, using the swelling force as the thermal runaway warning signal allows for better recognition in terms of parameter differentiation. In addition, the time when the change of the swelling force during thermal runaway exceeded the set value under normal working conditions was earlier than those of the temperature and voltage signals, so the early warning reliability was higher. Finally, the transmission of the swelling force signal was faster. By installing a swelling force sensor in the module, the swelling force change in any individual module could be acquired. In contrast, the temperature signal was limited by the sensor placement position and the delay of heat transfer, and it showed a slower acquisition sensitivity than the swelling force signal, which was another advantage of using the swelling force as an early warning signal for thermal runaway.

Table 2

Comparison of the changes in the swelling forces of the ternary material/graphite battery
Test conditions		Initial swelling force (N)	Maximum swelling force (N)	Magnitude of force increase (N)	Magnitude of force changing rate (N/s)
Temperature rise test	Temperature rise (25°C→65°C)	775	803	28	0.0075
Charging and discharging test	2 C-rate charging	761	1094	333	0.35
Charging and discharging test	2 C-rate discharging	842	342	500	1.4
Thermal runaway test	2 C-rate overcharge-induced runaway	794	4958	4164	80

In this paper, commercialized lithium iron phosphate/graphite and ternary/graphite batteries were used as the research objects, and the changes in the swelling force during the processes of temperature change, normal charge and discharge, and thermal runaway were compared. The results of the study were as follows.

(1) The variation range and rising rate of the swelling force during the thermal runaway process was considerably higher than the change during the normal charge and discharge processes, so the use of the swelling force as the thermal runaway warning signal had better recognition in terms of parameter differentiation.

(2) Compared to those of the temperature and voltage signals, the time when the variation range and rising rate of the swelling force during thermal runaway exceeded the value under normal working conditions was earlier, so it could be used for early warning.

(3) For practical use, the transmission of the swelling force signal was faster than temperature. By installing a swelling force sensor in the module, the swelling force change of any unit in the module could be collected. Compared with the temperature signal, it had a higher signal collection sensitivity. It should be noted that when the pressure sensor is installed in the battery module, it is necessary to maintain close contact between the cells to collect the swelling force signal of any battery cell in the module. At the same time, as the degree of aging of the battery increases, the swelling force of the battery gradually increases, and this value may increase to several tens of times that of a fresh battery. In this situation, to achieve a warning during the life cycle, it is necessary to calibrate the swelling forces of batteries in different aging states under normal working conditions and during thermal runaway.

Qiao Q, Zhao F, Liu Z, et al. Life cycle cost and GHG emission benefits of electric vehicles in China[J]. Transportation Research Part D Transport and Environment, 2020, 86:102418.
Qinyu, Qiao, et al. Life cycle greenhouse gas emissions of Electric Vehicles in China: Combining the vehicle cycle and fuel cycle[J]. Energy, 2019.
Zhao F, Chen K, Hao H, et al. Technology development for electric vehicles under new energy vehicle credit regulation in China: scenarios through 2030[J]. Clean Technologies and Environmental Policy, 2019.
http://www.gov.cn/zhengce/content/2020-11/02/content_5556716.html
Chombo P V, Laoonual Y. A review of safety strategies of a Li-ion battery[J]. Journal of Power Sources, 2020, 478:228649.
Feng X, Sun J, Ouyang M, et al. Characterization of penetration induced thermal runaway propagation process within a large format lithium ion battery module[J]. Journal of Power Sources, 2015, 275:261-273.
Gao S, Feng X, Lu L, et al. Thermal Runaway Propagation Assessment of Different Battery Pack Designs Using the TF5 Draft as Framework[J]. Journal of The Electrochemical Society, 2019, 166(8):A1653-A1659.
Sascha Koch, Fill A, Birke] K P. Comprehensive gas analysis on large scale automotive lithium-ion cells in thermal runaway[J]. Journal of Power Sources, 2018.
Sascha K, Kai B, Robert K. Fast Thermal Runaway Detection for Lithium-Ion Cells in Large Scale Traction Batteries[J]. Batteries, 2018, 4(2):16.
Global Technical Regulation on the Electric Vehicle Safety (EVS). Established in the Global Registry on 14 March 2018.
LI Bing, PAREKH M H, ADAMS R A, et al. Lithium-ion battery thermal safety by early internal detection, prediction and prevention[J]. Scientific Reports, 2019, 9(1).
B, Zhenghai Liao A, et al. "Experimental evaluation of thermolysis-driven gas emissions from LiPF6-carbonate electrolyte used in lithium-ion batteries - ScienceDirect." Journal of Energy Chemistry 49(2020):124-135.
RAGHAVAN A, KIESEL P, SOMMER L W, et al. Embedded fiber-optic sencing for accurate internal monitoring of cell state in advanced battery management systems (Ⅰ): Cell embedding method and performance[J]. Journal of Power Sources, 2017, 341: 466-473.
GANGULI A, SAHA B, RAGHAVAN A, et al. Embedded fiber-optic sencing for accurate internal monitoring of cell state in advanced battery management systems part (Ⅱ): Internal cell signals and utility for state estimation[J]. Journal of Power Sources, 2017, 341: 474-482.
SRINIVASAN R, DEMIREV P A, CARHUFF B C. Rapid monitoring of impedance phase shifts in lithium-ion batteries for hazard prevention [J]. Journal of Power Sources, 2018, 405: 30-36
SRINIVASAN R, CARHUFF B C, BULTER M H, et al. Instantaneous measurement of the internal temperature in lithium-ion rechargeable cells[J]. Electrochimica Acta, 2011, 56: 6198-6204.

There is NO Competing Interest.

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A new method of thermal runaway warning for lithium-ion batteries using the swelling force

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Abstract

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Highlights

1 Introduction

2 Experimental

3 Result and discussion

3.1 Changes in swelling force under normal working conditions of battery

3.2 Change in swelling force of battery during thermal runaway

4 Conclusion

References

Additional Declarations

Supplementary Files

Status:

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