Introduction
Li(NixCoyMn1-x-y)O2 (NCM) lithium-ion batteries (LIBs) have attracted considerable research attention because of their high energy density and excellent electrical performance. However, owing to the high activity of the cathode material specifically Li(Ni0.8Co0.1Mn0.1)O2 (NCM811), NCM LIBs are not stable under the current technical conditions. Fire and explosion accidents of NCM LIBs occur frequently. Most LIBs accidents are caused by thermal runaway (TR). Numerous studies focused on the TR mechanism of NCM LIBs have revealed that NCM cathode material decomposes at high temperature and releases oxygen, which results in an exothermic reaction with the electrolyte. This result promotes the thermal decomposition of the cathode, which releases considerable heat rapidly, rendering the TR of the NCM LIBs highly volatile and dangerous [1]. The abuse conditions include mechanical abuse, electrical abuse, and thermal abuse [2]. Overcharged LIB stores more energy, which make TR temperature higher and fire-prone. In daily life, overcharging is the most common battery abuse condition. Mismatched chargers and battery management system failures result in overcharging of batteries, which frequently causes fire accident. Therefore, many studies have been conducted on TR under overcharging conditions.
Zeng et al. [3] established a three-dimensional electrochemical–thermal coupling model to simulate thermal and electrochemical characteristics from normal charge to early overcharge. The simulation results revealed that irreversible joule heat contributes the most to the temperature rise during normal charge, but at the early overcharge stage, heat caused by manganese dissolution and lithium deposition gradually dominated the temperature rise. Ren et al. [4] established the electrochemical–thermal coupling overcharge–TR model, and revealed that the electrolyte oxidation reaction and the reaction between the plated lithium and the electrolyte are the primary causes of overcharge–TR heat generation. These two models cover the entire process from overcharging to thermal runaway and sustain experimental studies.
Numerous TR experiments have been conducted on NCM LIBs under overcharge conditions. Yuan et al. [5] observed that when the NCM battery was overcharged to 5.1V for the first time, the battery resistance suddenly increased because of electrolyte oxidation. Because the battery is further overcharged, the cathode/electrolyte interface becomes highly reactive. The internal temperature of the battery rises to more than 200°C, accompanied by the generation of a large amount of gas. The analysis of the cathode and anode after overcharging revealed that the lithium plating during overcharging is the primary cause of TR. Zhu et al. [6] categorized the overcharging process into four stages. When the charging rate was less than 2C, a novel voltage plateau occurred when the voltage reached approximately 5.1V. Ren et al. [7] characterized the cathode and anode materials under various overcharge states to determine side reactions within the battery. The cathode underwent electrolyte decomposition, transition metal dissolution, and phase transformation during the process of overcharging, but did not exhibit obvious exothermic behavior before the occurrence of TR. For anode, severe lithium plating accelerated the TR process caused by overcharging. Xu et al. [8] revealed that the early abnormal expansion of the NCM523 battery was caused by the reaction of lithium dendrite and lithium plating, and the expansion force increased sharply with the increase in the state of charge (SOC), up to 3400N. Above studies reveal the plateau voltage, major heat sources, and side reactions of overcharging. Zhu et al. [6]With the increased in the rate of charge, the peak voltage of the voltage curve increased linearly. Ren et al. [7] revealed that charging current had a limited influence on the overcharge behavior of batteries, whereas batteries with decompression design and excellent heat dissipation exhibited superior overcharge performance. Pouch rupture and separator melting are two key factors leading to TR in the overcharging process. Ye et al. [9] revealed that the constant current (CC)-constant voltage (CV)-CC overcharge of the LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode material battery was more dangerous than the CC overcharge. When charging speeds are less than 1C, side effects generate 80% heat, which results in TR. Huang et al. [10] revealed that, compared with prismatic and pouch LIBs with the same capacity and chemical composition, pouch batteries exhibited excellent thermal behavior characteristics and overcharging resistance. However, superior TR buffering characteristics, smaller deformation, and longer warning time using prismatic cells. Wang et al. [11] revealed that under the same overcharge condition, with the increase in the proportion of nickel in the cathode material, TR occurrence gradually advanced, and the maximum temperature also increased. Above studies focused on various factors affecting the overcharge of LIBs. These studies are highly critical to the safety design and management of NCM power batteries.
However, limited studies have been conducted on related accidents, and a scientific analysis us yet to be conducted on the identification of the cause of battery fires. Based on fire patterns, witness testimony, and video surveillance, fire investigators can determine that the fire origin was in the battery. Due to the lack of investigation methods, many investigations of accidents with minor damage ended at this step. The cause of thermal runaway was not specified. In fires with large damage, the first battery to fail was identified by battery management system data and physical characteristics such as expansion. A sudden voltage decrease in a cell or module often means an internal short circuit [12]. Wang et al. revealed that the bulge surface of the residue pointed to the battery that experienced thermal runaway first in the module [13]. The suspected battery was subjected to nondestructive examinations, such as CT, to look for flaws in the battery. The battery was then disassembled to verify flaws. Melted traces can be observed in the battery triggered by internal short circuit [14]. Nagourney et al. [15] revealed that several physical features were incorrectly identified in previous LIBs accident investigations. They conducted repeatable experiments to confirm that these physical features were present in flawless batteries in controlled fires. Thus, these features were not effective indicators of the causes of fire. Therefore, research on thermal runaway residues is needed to find more scientific and generalizable methods for investigating lithium battery fires. Liu et al. [16] was the first to relate characteristic elements of TR causes to residues. Aluminum was detected in combustion products under the overcharge condition because the metal oxides precipitated from the cathode material react with aluminum foil at a high temperature to produce Al2O3. However, under heating conditions, no aluminum was detected because of insufficient conditions for the alumino–thermal reaction. Repeated experiments were performed to verify the phenomenon. Weng et al. [17] used the X-ray CT imaging and energy-dispersive spectrometry (EDS) to conduct the micro morphology analysis of TR residue induced by external heating. From the X-ray images, the messy internal structure and molten drops are observed from the burnt cells. EDS mapping reveals a dramatic reduction on the content of element F after combustion (8.95±0.52% vs. 1.79±0.41%). Limited studies have focused on scientific methods and systems to determine and identify the causes of TR of LIBs in the fire investigation.
In this study, the overcharging behavior of NCM LIBs was analyzed by combining the voltage and temperature changes and phenomena during overcharging. The macroscopic trace, microscopic morphology, and residual composition of NCM LIBs under overcharging were analyzed. This study provides a reference for studying the TR mechanism under overcharging and distinguishing the specific causes of TR.
Section snippets
Experiment
In this project, the pouch NCM811 polymer power battery (Model 1368130) assembled by the lamination process was selected. The specific parameters and dimensions are presented in Table 1 and Fig. 1.
At an ambient temperature of 25±2°C, connect the battery to EBC-A10 charge–discharge meter, conduct 0.2C (2.4 A) CC charging, then charge the battery at constant voltage to the voltage of 4.22V, and allow it to stand for 1h till 100% SOC battery.
Referring to the overcharge test method in GB/T
Macroscopic analysis
The macroscopic analysis included two parts: observation and analysis of the appearance characteristics of the battery, the other part is the observation and analysis of the electrode units inside the battery after disassembly.
After cooling, the battery residues were placed on the evidence table and recorded with Nikon D7000 camera under the same shooting conditions. The key dimensions of each component were measured and recorded with digital display vernier calipers. The characteristics system
TR process
Fig. 2 displays the overcharge process of the experiment. With the continuous overcharging process, the battery shell begins to exhibit obvious swelling deformation, and with the leakage of electrolyte. After approximately 20min, the positive side of battery packaging burst and deflated, and a limited amount of gas was vented. After approximately 27min, the battery continued to emit white gas from the broken part of the package. The gas was ignited to form a jet fire, followed by a premix gas
Conclusion
The relationship between the TR phenomenon and voltage–current–temperature of the NCM811 battery triggered by 1C overcharge was studied. Residue analysis was used to investigate TR process and mechanism. The macroscopic morphology, microscopic morphology, and phase composition of battery residue were analyzed. Valuable features were identified for use in the investigation of lithium-ion battery accidents. The conclusions are as follows:
- 1)
The 1C overcharging process of the NCM811 battery could be
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgment
This work was supported by the National Natural Science Foundation of China (52106284), the Natural Science Foundation of Hebei Province (B2021507001/E2021507002). The author would also like to acknowledge the support of the Science and Technology Project of Langfang (2021011017), and Cultivation Project of NSFC from China People's Police University (ZRJJPY202101).
CRediT authorship contribution statement
Junli Sun: Conceptualization, Methodology, Investigation, Writing - Review & Editing.
Zihan Gong: Writing - Original Draft, Experimental design method, Writing - Review & Editing.
Congyu Gu: Writing - Review & Editing, Experiment.
Huaibing Wang: Assist in carrying out experimental research, Funding Acquisition.
Yang Li: Assist in carrying out experimental research, Funding Acquisition.
Xiaohui Zhou: Assist in carrying out experimental research.
Yizhuo Jia: Data Visualization.
Dengchao Han: Assist in
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FAQs
What is the impact of charging and charging rate on thermal runaway behaviors of lithium ion cells? ›
Ouyang (Ouyang et al., 2021) analyzed the impact of charging and charging rate on thermal runaway behaviors, their results indicated that the more severe deterioration may be ascribed to the growth of the cell capacity and the decline operation stability during charging.
What is the thermal runaway of a lithium ion battery? ›The thermal runaway of lithium-ion batteries is the phenomenon of chain exothermic reactions within the battery. These reactions cause a sharp rise in the internal battery temperature causing the inner structures of the battery to destabilize and degrade, which eventually leads to the failure of the battery.
What is the probability of thermal runaway in lithium ion cells? ›For lithium-ion batteries this includes the risk of thermal runaway and associated fires. The risk of thermal runaway is quite low for a single cell (— 0.0001%), but the probability of a cell initiating thermal runaway can increase significantly in large installations with thousands of cells (-0.1%).
What is thermal runaway characterization of Li ion batteries under external heating conditions? ›This catastrophic self-accelerated degradation of the Li-ion battery is called thermal runaway. During thermal runaway, temperatures as high as 900 °C can be reached,3 and the battery can release a significant amount of burnable and (if inhaled in high concentrations) toxic gas.
What effect does an overcharging over discharging rise in temperature can do on a Li-ion battery cell life and operation? ›The excess energy leads to heat generation. “In the worst case, this can lead to a so-called 'thermal runaway'. This means that the temperature in the cell continues to rise and chemical reactions start from it, which proceed exponentially. These reactions can no longer be stopped,” explains Dr.
How does a Li-ion battery degrade under overcharge conditions? ›Overcharging damages the interior structure and causes side reactions, including electrolyte decomposition, transitional metal ion dissolution, lithium deposition, SEI decomposition and generation, particle cracking, and negative and positive electrode decomposition [4], [5].
How do you prevent thermal runaway in lithium-ion batteries? ›One of the simplest ways to prevent thermal runaway is to store batteries at safe temperatures. The ideal storage temperature for most lithium-ion batteries is between 40-70 degrees Fahrenheit (5-20 degrees Celsius).
What happens when a lithium-ion battery runs out? ›Rechargeable Lithium-Ion batteries have a limited life and will gradually lose their capacity to hold a charge. This loss of capacity (aging) is irreversible. As the battery loses capacity, the length of time it will power the product (run time) decreases.
What causes thermal runaway in lead-acid batteries? ›Dropping a battery, over charging and over discharging, high vibration environments, and even poor manufacturing quality can lead to internal shorts that cause thermal runaway.
What causes thermal runaway in lithium-ion cells? ›Faults in a lithium-ion cell can result in a thermal runaway. These faults can be caused by internal failure or external conditions. One example of such internal failure is an internal short circuit.
What triggers thermal runaway? ›
Thermal runaway begins when the heat generated within a battery exceeds the amount of heat that is dissipated to its surroundings. If the cause of excessive heat creation is not remedied, the condition will worsen.
How do you check for thermal runaway in batteries? ›Terminal voltage and surface temperature monitoring methods. The battery management system (BMS) is the most widely used method for monitoring and detecting thermal runaway events in lithium-ion battery applications. It mainly relies on the built-in voltage sensors and temperature sensors as measurement tools.
How does temperature affect lithium-ion battery life? ›Very low temperatures can produce a reduction in the energy and power capabilities of lithium-ion batteries. High ambient temperatures, however, can contribute to a high internal temperature of the battery — which can also decrease performance and power capabilities.
What are the characteristics of Li battery? ›Lithium-ion batteries are common in consumer electronics. They are one of the most popular types of rechargeable battery for portable electronics, with one of the best energy-to-weight ratios, high open circuit voltage, low self-discharge rate, no memory effect and a slow loss of charge when not in use.
What happens if you charge a lithium battery with too much voltage? ›In a lithium-ion battery, overcharging can create unstable conditions inside the battery, increase pressure, and cause thermal runaway. Lithium-ion battery packs are required to have a protection circuit to prevent excessive pressure build-up and cut off the flow of ions when the temperature is too high.
What are the dangers of a lithium-ion battery if overheated or overcharged? ›Occasionally, if a Lithium-ion Battery is improperly charged, handled, stored or disposed of there is a risk of overheating, catching fire or explosion. This also increases the risk of a house fire, garage fire or personal injury.
What temperature do lithium batteries stop working? ›Unfortunately, any temperature lower than 32°F can cause appreciable damage to the batteries. The chemical reactions when charging lithium batteries below freezing point will slow down to a point where hardly any useful energy is produced. At this point, the batteries may eventually stop working altogether.
Can you fix an overcharged lithium battery? ›No, there is no possibility of battery repair in case of over-discharging or overcharging. This applies to lithium iron phosphate and other battery types. Excessive charging causes permanent and irreparable damage.
How do I know if my lithium-ion battery is bad? ›Swelling: When a lithium battery fails, another common sign is battery swelling. If your battery looks swollen, you should stop using it immediately. Similar signs include any type of lump or bulge, or leakage from the device. Noise: Failing lithium batteries have also been reported to make hissing or cracking sounds.
What causes lithium batteries to lose capacity? ›Batteries degrade in part due to loss of lithium inventory (LLI), where the lithium ions do not attach to the electrodes and leave the battery circulation process. This can be caused when the electrodes degrade and damage the sites where the lithium ions normally attach.
Can you stop a battery thermal runaway? ›
It may not be possible to eliminate the possibility of thermal runaway within a cell completely. While good thermal management, structural design, and battery management can reduce the risk, there is always the possibility of defects or foreign objects causing internal short circuits.
How can a thermal runaway reaction be stopped? ›A runaway reaction, if caught early, can sometimes be halted by adding chemicals to cancel the effect of the catalyst. Common measures include neutralization, quenching with water or other diluent, or dumping the contents into another vessel which contains a quench liquid.
What is the major problem in lithium-ion battery? ›Lithium-ion batteries contain metals such as cobalt, nickel, and manganese, which are toxic and can contaminate water supplies and ecosystems if they leach out of landfills. Additionally, fires in landfills or battery-recycling facilities have been attributed to inappropriate disposal of lithium-ion batteries.
Do Li-ion batteries need to be fully discharged before charging? ›Unlike other types of batteries that need to be recharged throughout their storage time, lithium batteries do better at 40%-50% DOD (depth of discharge). Pro-Tip: After every 30 charges, allow your lithium based battery to completely discharge before recharging.
What happens if you overcharge a 18650 battery? ›You can overcharge a 18650 battery, but it's not recommended. Overcharging will damage the battery and in some cases cause a fire or explosion. A lithium-ion battery is an energy storage device that uses an electrochemical reaction to produce electricity.
Which types of batteries are susceptible to thermal runaway? ›Lithium-ion batteries are known for being prone to thermal runaway.
At what temperature do lithium-ion batteries explode? ›The temperature can quickly reach 500°C (932°F), at which point the cell catches fire or it explodes. This thermal runaway that occurs is known as “venting with flame.” “Rapid disassembly” is the preferred term by the battery industry.
What is the biggest cause of lead-acid battery failures? ›1. The leading causes of battery failure are improper charging and lack of maintenance that aggravate lead-acid battery failure mechanisms. 2. The primary lead-acid battery failure mechanisms are internal corrosion, sulfation and loss of electrolyte.
What happens when lithium gives away an electron? ›In losing an electron to become a cation, the lithium atom is said to be oxidized. When lithium forms chemical compounds with other elements, it does so by losing an electron from each lithium atom to become Li+ cations. These, then, are attracted to negatively charged anions in ionic compounds.
What reduces thermal runaway? ›Thermal runaway often occurs from punctures and improper charging. To counter such fire hazards, the inventors used a thermal fluid that contains a flame retardant. A flame retardant is a compound that inhibits, suppresses, or delays the production of flames or prevents the spread of fire.
Does thermal runaway need oxygen? ›
Ending Thermal Runaway
Safety systems include gas/oxygen deprivation and water. Among the more common gas systems are carbon dioxide, argon, or nitrogen. With these systems, the idea is to flood the area with gas that doesn't contain oxygen and, therefore, makes it difficult for anything to burn.
Addressing and preventing thermal runaway
One approach to minimizing the possibility of TR is with preventative maintenance, including adjusting the charging voltage, ensuring proper ambient air temperature surrounding the battery, and replacing older batteries before failure is likely to occur.
Excessive cold (generally between -4 to 140 ℉ or -20 to 60 ℃) can also lead to thermal runaway.
How reliable is thermal battery? ›Thermal batteries have the inherent advantages of being very reliable, rugged, and robust. Being hermetically sealed, they can remain in storage for 25 years or more without degradation.
Can thermal runaway caused an explosion of lithium ion battery? ›Lithium ion battery and its safety are taken more consideration with fossil energy consuming and the reduction requirement of CO2 emission. The safety problem of lithium ion battery is mainly contributed by thermal runaway caused fire and explosion.
What is thermal runaway in lithium ion car battery? ›Thermal runaway occurs when a battery cell short circuits & starts to heat up uncontrollably. Lithium ion batteries contain a large amount of energy in a very small space. Under normal operation, they rapidly convert chemical energy to electrical energy.
Does cold permanently damage lithium batteries? ›You should never charge any battery when the temperature dips below freezing. This can cause severe and permanent damage to your battery. You should always take the time to let the battery warm up to a safe temperature before you begin charging it.
At what temperature do batteries self discharge? ›Self-discharge is considerably increased at temperatures above +55°C. Batteries can reach or even exceeded these temperatures when left in storage rooms during hot summers.
How hot should NiMH batteries get when charging? ›When charging NiCD or NiMH rechargeable batteries, they do increase in temperature substantially due to internal resistance. Thus, the batteries may feel warm when the charge is completed. According to specification, most NiMH batteries, including Maha, may heat up to 131 deg F or 55 deg C during a rapid charge.
What are 4 characteristics of lithium? ›Between the most significant properties of lithium we find its high specific heat (calorific capacity), the huge temperature interval in the liquid state, high termic conductivity, low viscosity and very low density.
What are 3 characteristics of lithium? ›
Uses and properties
A soft, silvery metal. It has the lowest density of all metals. It reacts vigorously with water. The most important use of lithium is in rechargeable batteries for mobile phones, laptops, digital cameras and electric vehicles.
In a lithium-ion battery, graphite is used as the anode, one of the two electrodes in a battery, to host lithium ions during battery charge and discharge. In a lithium metal battery, we use lithium metal as the anode, which offers more than 10 times higher capacity than that of graphite.
What causes thermal runaway in lithium ion cells? ›Faults in a lithium-ion cell can result in a thermal runaway. These faults can be caused by internal failure or external conditions. One example of such internal failure is an internal short circuit.
What are the effects of fast charging on lithium ion cells? ›During fast charging, Li+ ions intercalate into the anode and deintercalate from the cathode rapidly, leading to a severe lithium concentration gradient, strain mismatch between different parts of the electrode particle and stress development.
Does fast charging affect lithium battery life? ›Does fast charging damage my battery? You'd think with all that extra power there could be a risk to your battery. From our findings though, fast charging doesn't cause any more damage to your phone than standard charging.
What causes thermal runaway in lead acid batteries? ›Dropping a battery, over charging and over discharging, high vibration environments, and even poor manufacturing quality can lead to internal shorts that cause thermal runaway.
What can cause a lithium ion battery to overheat? ›Lithium-ion batteries heat up when you are charging them at very high rates. If the battery almost depletes before charging, the charger will become progressively hot during the “bulk charging” phase (one to two hours after charging begins).
What is the leading cause of lithium-ion battery failure? ›Since lithium is reactive in nature, the selection of suitable electrolytes is critical. Due to the large anode volume changes, the Solid Electrolyte Interface (SEI) layer can crack and dendrites formed during lithium cycling can grow through this layer, leading to short circuit and battery failure.
What happens when a lithium-ion battery is charged? ›The movement of the lithium ions creates free electrons in the anode which creates a charge at the positive current collector. The electrical current then flows from the current collector through a device being powered (cell phone, computer, etc.) to the negative current collector.
How efficient is Li-ion battery charging? ›Lithium batteries charge at nearly 100% efficiency, compared to the 85% efficiency of most lead acid batteries. This can be especially important when charging via solar, when you are trying to squeeze as much efficiency out of every amp as possible before the sun goes down or gets covered up by clouds.
What shortens the life of lithium batteries? ›
Raising the voltage above 4.20V/cell would shorten the life. The readings reflect regular Li-ion charging to 4.20V/cell. Guideline: Every 70mV drop in charge voltage lowers the usable capacity by about 10%.
Should a lithium battery stay on charger all time when not using? ›This isn't a safety issue: Lithium-ion batteries have built-in safeguards designed to stop them from exploding if they're left charging while at maximum capacity. But in the long term, electronics will age faster if they're constantly plugged in while already charged to 100 percent.
Do lithium batteries get worse over time? ›Lithium-ion batteries are, in essence, continuously degrading from the moment they are first used. This is as a result of the fundamental chemistry of the battery, which gives rise to unavoidable chemical reactions which take place inside the battery during runtime.
How do you extinguish thermal runaway? ›The only way to stop a thermal runaway is by directly cooling the cells involved to ensure that the failed cell does not cause the cells around it to also fail.
What should lithium batteries be stored away from? ›Batteries should be stored away from sunlight, heat, and humidity. Keep the storage area ventilated and dry, and maintain a relatively steady temperature. The ideal battery storage temperature is around 59℉, but most room temperatures will suffice.