Why do Lithium Ion Batteries Catch Fire and Explode?

These days, lithium-ion batteries can be found in a whole host of household electronics including laptops, mobile phones and tablets. As well as this, they&#;re a popular choice for large-scale energy storage systems such as electric cars and power grids across the country.  

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Lithium-ion batteries, particularly lithium-ion ones, are popular in these products and systems due to their proficiency to recharge. Unlike your standard alkaline batteries, lithium-ion batteries can be used over and over again, which is why they can be found in many home electronics. 

The good news is that fires and accidents triggered by lithium-ion batteries are extremely rare. However, that does not mean you shouldn&#;t take precautions to avoid a catastrophe. 

While instances may be infrequent, spontaneous combustion of lithium batteries does occur, and in this article, we&#;ll explain why they can catch fire and how to prevent it from happening.

    

How Do Batteries Work?

Before asking the question why do batteries catch fire, it&#;s important to have an understanding of how they work. 

Time for a quick science lesson. All lithium-ion batteries have two electrodes that are kept apart by an electrolyte. An electrolyte is a substance that creates a solution that conducts electricity. An electric charge is passed through the electrolyte from a lithium-ion metal cathode, and this is what makes the battery, and therefore your electronics, operate. 

However, it also creates the perfect environment for a fire to thrive. Lithium-ion batteries are built in such a way that the three core conditions of a fire (oxygen, fuel and heat) can be met. 

The ingredients used in the electrolyte are known as organic solvents and they can act as fuel for a fire. This, combined with the heat generated in a battery and the oxygen that is contained in the cathode, makes for an ideal trigger for a fire. 

 

Why Do Batteries Catch Fire? 

Now we&#;ve established that, under the right conditions, lithium-ion batteries can provide a good environment for a fire, let&#;s take a look at why they occur.  

Because they need to fit into a compact space, key components of a battery are extremely small and lightweight. Many of these components come in the form of thin partitions that are quite fragile, and if they become punctured or pierced a spark may occur and start a fire. As the heat of the fire increases, a process called thermal runaway can begin. 

This is where the heat generated inside the battery begins to exceed the amount that is dispersed elsewhere, potentially resulting in an explosion from the battery. 

It&#;s important to mention at this point that this is an extremely rare occurrence, but it is something you should be aware of.    

 

How to Minimise the Risk  

If your business or organisation handles a large number of products that include lithium-ion batteries, it&#;s important to understand the risks and how to prevent a fire from breaking out. 

There are a variety of ways you can do this. Firstly, it&#;s good practice to ensure that the place you&#;re storing the batteries is not exposed to high temperatures. For example, do not leave them in a room that is known to get hot, keep them out of hot vehicles and for individual products such as laptops and mobile phones, try not to cover them with blankets or keep them in warm pockets for a significant amount of time.

Another good tip is keeping products that contain these batteries away from each other. For example, try not to keep laptops, phones and tablets all in the same bag while travelling. Sometimes this may be unavoidable, like when you visit an airport and need to keep electronics together, but on the whole, it&#;s a good idea. While it won&#;t necessarily stop a fire from occurring, keeping your items separate will mean that they won&#;t all be at risk.

Finally, look after your battery. Sometimes we take recharging for granted and it can actually be causing damage to your battery and making it more susceptible to faults. For instance, don&#;t wait until your device is completely drained to charge it and avoid overcharging. Overcharging is when you keep your device plugged in even after it has been fully charged; at this point, it usually becomes hot to touch so remember to unplug when it&#;s done.   

At Scutum South East, we&#;re experts in all aspects of fire safety and provide a wide range of services to keep people and property protected. From the supply, installation and maintenance of products such as fire extinguishers, fire alarm systems and doors to fire risk assessments and training for staff, we&#;re on hand to keep commercial, industrial and non-residential properties safe. To learn more about what we do or for some help and advice, contact us today.  

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Apparao Rao, Clemson University ; Bingan Lu, Hunan University; Mihir Parekh, Clemson University , and Morteza Sabet, Clemson University

In today&#;s electronic age, rechargeable lithium-ion batteries are ubiquitous. Compared with the lead-acid versions that have dominated the battery market for decades, lithium-ion batteries can charge faster and store more energy for the same amount of weight.

In June , a fire started at this e-bike shop in New York City and spread to upper floors of the building. AP Photo/Bebeto Matthews

These devices make our electronic gadgets and electric cars lighter and longer-lasting &#; but they also have disadvantages. They contain a lot of energy, and if they catch fire, they burn until all of that stored energy is released. A sudden release of huge amounts of energy can lead to explosions that threaten lives and property.

As scientists who study energy generation, storage and conversion, and automotive engineering, we have a strong interest in the development of batteries that are energy-dense and safe. And we see encouraging signs that battery manufacturers are making progress toward solving this significant technical problem.

A new fire hazard

At the same time, e-bikes and electric scooters are transforming urban transit by providing convenient, low-carbon ways to navigate crowded streets and reduce traffic congestion. From through , shared e-bikes and e-scooters &#; those owned by rental networks &#; accounted for more than half a billion trips in U.S. cities. Privately owned e-bikes add to that total: In , more than 880,000 e-bikes were sold in the U.S., compared with 608,000 electric cars and trucks.

Urban transportation is undergoing a transformative shift toward electrification. As concerns grow in cities around the world about climate change and air quality, electric vehicles have taken center stage.

Battery-powered vehicles account for a small share of car fires, but controlling EV fires is difficult. Typically, an EV fire burns at roughly 5,000 degrees Fahrenheit (2,760 Celsius), while a gasoline-powered vehicle on fire burns at 1,500 F (815 C). It takes about 2,000 gallons of water to extinguish a burning gasoline-powered vehicle; putting out an EV fire can take 10 times more.

This is a major concern in large cities where electric vehicles are popular. Fire departments in New York City and San Francisco report handling more than 660 fires involving lithium-ion batteries since . In New York City, these fires caused 12 deaths and more than 260 injuries from through early . Clearly, there is a need for safer handling and charging practices, as well as technical improvements to batteries.

E-bikes are popular for urban delivery services, which means that many users rely on them for income. Lindsey Nicholson/UCG/Universal Images Group via Getty Images

Many batteries in an EV

To understand lithium-ion battery fires, it&#;s important to know some basics. A battery holds chemicals that contain energy, with a separator between its positive and negative electrodes. It works by converting this energy into electricity.

The two electrodes in a battery are surrounded by an electrolyte &#; a substance that allows an electrical charge to flow between the two terminals. In a lithium-ion battery, for example, lithium ions carry the electric charge. When a device is connected to a battery, chemical reactions take place on the electrodes and create a flow of electrons in the external circuit that powers the device.

When a lithium-ion battery delivers energy to a device, lithium ions &#; atoms that carry an electrical charge &#; move from the anode to the cathode. The ions move in reverse when recharging. Argonne National Laboratory/Flickr, CC BY-NC-SA

Cellphones and digital cameras can operate on a single battery, but an electric car needs much more energy and power. Depending on its design, an EV may contain dozens to thousands of single batteries, which are known as cells. Cells are clustered together in sets called modules, which in turn are assembled together in packs. A standard EV will contain one large battery pack with many cells inside it.

What causes battery fires

Typically, a battery fire starts in a single cell inside a larger battery pack. There are three main reasons for a battery to ignite: mechanical harm, such as crushing or penetration when vehicles collide; electrical harm from an external or internal short circuit; or overheating.

Battery short circuits may be caused by faulty external handling or unwanted chemical reactions within the battery cell. When lithium-ion batteries are charged too quickly, chemical reactions can produce very sharp lithium needles called dendrites on the battery&#;s anode &#; the electrode with a negative charge. Eventually, they penetrate the separator and reach the other electrode, short-circuiting the battery internally.

Such short circuits heat the battery cell to over 212 F (100 C). The battery&#;s temperature rises slowly at first and then all at once, spiking to its peak temperature in about one second.

Another factor that makes lithium-ion battery fires challenging to handle is oxygen generation. When the metal oxides in a battery&#;s cathode, or positively charged electrode, are heated, they decompose and release oxygen gas. Fires need oxygen to burn, so a battery that can create oxygen can sustain a fire.

Because of the electrolyte&#;s nature, a 20% increase in a lithium-ion battery&#;s temperature causes some unwanted chemical reactions to occur much faster, which releases excessive heat. This excess heat increases the battery temperature, which in turn speeds up the reactions. The increased battery temperature increases the reaction rate, creating a process called thermal runaway. When this happens, the temperature in a battery can rise from 212 F (100 C) to 1,800 F ( C) in a second. https://www.youtube.com/embed/kHTlVmBbnPA?wmode=transparent&start=0 In thermal runaway, a lithium-ion battery enters an uncontrollable, self-heating state that can lead to fire or explosion.

Managing the thermal runaway problem

Methods to ensure battery safety can focus on conditions outside or inside of the battery. External protection typically involves using electronic devices, like temperature sensors and pressure valves, to ensure that the battery isn&#;t subjected to heat or force that could cause an accident.

However, these mechanisms make the battery larger and heavier, which can reduce the performance of the device it powers. And they may not be reliable under extreme temperatures or pressures, such as those produced in a car crash.

Internal protection strategies focus on using intrinsically safe materials for battery components. This approach offers an opportunity to address potential hazards at their source.

Making a thermal runaway in a battery pack less intense requires a mix of software and hardware improvements. Scientists are working to develop cathodes that release less oxygen when they break down; nonflammable electrolytes; solid-state electrolytes, which do not catch fire and also may help alleviate dendrite growth; and separators that can withstand high temperatures without melting.

Another solution is already in use: battery management systems. These are hardware and software packages built into battery packs that can monitor vital battery parameters, such as the state of charge, internal pressure and the temperature of the cells in the battery pack.

Just as a physician uses a patient&#;s symptoms to diagnose and treat their illness, battery management systems can diagnose conditions within the battery pack and make autonomous decisions to shut off batteries with hot spots, or to alter the load distribution so that any individual battery does not get too hot.

Battery chemistries are evolving rapidly, so new designs will require new battery management systems. Many battery producers are forming partnerships that bring together manufacturers with complementary battery expertise to tackle this challenge.

Users can also take steps to maximize safety. Use manufacturer-recommended charging equipment and outlets, and avoid overcharging or leaving an EV plugged in overnight. Inspect the battery regularly for signs of damage or overheating. Park the vehicle away from extremely hot or cold surroundings &#; for example, park in shade during heat waves &#; to prevent thermal stress on the battery.

Finally, in the event of a collision or accident involving an EV, follow the manufacturer&#;s safety protocols and disconnect the battery if possible to minimize the risk of fire or electrocution.

Apparao Rao, Professor of Physics, Clemson University ; Bingan Lu, Associate Professor of Physics and Electronics, Hunan University; Mihir Parekh, Postdoctoral Fellow in Physics and Astronomy, Clemson University , and Morteza Sabet, Research Assistant Professor of Automotive Engineering, Clemson University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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