What You Need to Know About Lithium Battery Thermal Runaway

Lithium battery thermal runaway is a phenomenon that occurs when the batteries are exposed to high temperatures for extended periods of time.

If left unchecked, thermal runaway can cause these batteries to experience a catastrophic failure that results in fires, explosions and other dangerous consequences. Lithium-ion batteries are used in a wide range of applications because they have a low cost, high energy density and fast charging capabilities.

However, they are also known to experience thermal runaway if specific conditions are not met.

In this blog post, you will learn what thermal runaway is, the different types of lithium ion batteries and their inherent risks, as well as steps you can take to mitigate the risk of thermal runaway in your facility or work space.

What is thermal runaway?

Thermal runaway occurs when an increase in temperature causes an increase in current within the battery. This can lead to a cascading chain reaction that results in the failure of the battery.

The problem with lithium ion batteries is that the thermal runaway reaction can be difficult to predict and is often out of the control of the user.

If lithium ion batteries experience thermal runaway, there is a chance that they could catch fire. Firefighters need to be aware that batteries are a potential fire hazard because lithium ion batteries can produce high heat, smoke and ash.

In addition to the risk of a fire, thermal runaway can cause batteries to overheat and emit toxic fumes. It can also cause batteries to expand at an accelerated rate, which can lead to the breakdown of the battery’s electrolyte and the release of the electrolyte into the environment.

Dangers of lithium battery Thermal Runaway

While lithium ion batteries are often used in daily life because of their low cost and high energy density, they can experience thermal runaway if specific conditions are not met.

Thermal runaway can occur in any lithium ion battery, but it is more likely to happen in lithium-ion batteries that use an organic solvent as an electrolyte.

You should be aware of these risks if you use lithium-ion batteries in your facility or work space. There are several dangers related to lithium battery thermal runaway:

A risk of fire

If batteries experience thermal runaway, there is a chance that they could catch fire. Firefighters need to be aware that batteries are a potential fire hazard because lithium ion batteries can produce high heat, smoke and ash.

A risk to the environment

If the battery catches fire, it can lead to toxic fumes being released into the air. These fumes can be harmful to the surrounding environment.

A risk to human health

If the battery catches fire, toxic fumes can be released into the surrounding environment and can be inhaled by people, posing a risk to their health.

Process of lithium battery thermal runaway

Stage 1: Battery Abuse

During this first stage,thermal electrical or mechanical abuse results in cell damage, causing battery cell temperatures and pressures to increase.

Stage 2: Off-Gas Generation

As cell temperatures and pressures rise, flammable gases vent from the cells. This is the critical point an which action must be taken to avoid thermal runaway and a fire event.

Stage 3: Thermal Runaway

Thermal runaway marks the very end of the prevention region and the start of the containment region. Temperatures rapidly rise several hundred degrees and smoke is produced. It is at this point that catastrophic fai

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Why do lithium ion batteries experience thermal runaway?

Reasons in Using

Temperature:

Lithium ion batteries can experience thermal runaway if they are exposed to high temperatures for extended periods of time. While lithium ion batteries can operate in extreme temperatures, they must be monitored at all times.

If you keep the batteries at or below their designated temperature, you will reduce the risk of thermal runaway. Lithium ion batteries are designed to operate within a specific temperature range.

If they are outside of this temperature range for too long, they can experience thermal runaway. Lithium ion batteries experience a reduction in capacity and lifespan when they are used outside of their designated temperature range, which can lead to thermal runaway.

Short circuit:

Mechanical abuse, such as extrusion, collision, acupuncture, etc. causes the battery (battery cell) to deform under the action of external forces, the diaphragm is destroyed, and the short circuit between the positive and negative electrodes induces thermal runaway.

Reasons in Manufacturing

1.Insufficient of negative electrode capacity:

The following is the thermal runaway process if negative electrode capacity is insufficient

Step 1.

When the capacity of the negative electrode opposite the positive electrode part is insufficient, or there is no capacity at all, some or all of the lithium generated during charging cannot be inserted into the inter layer structure of the negative electrode graphite.

Step 2.

Then lithium will settle on the surface of the negative electrode, forming a protruding “dendrite”. The next time, when battery is charged, this protruding part is more likely to generate lithium.

Step 3.

After dozens to hundreds of cycles of charging and discharging, the “dendrite” will grow.

Step 4.

Finally, “dendrite” will pierce the diaphragm paper and cause a short circuit inside.

The battery discharges sharply which will generate a lot of heat.

The heat will burn out the diaphragm, and cause a greater short circuit.

The high temperature will decompose the electrolyte into gas, and the negative carbon and the diaphragm paper will burn, causing excessive internal pressure. When the shell of the battery cannot withstand this pressure, the battery will explode.

2.High moisture content

Moisture can react with the electrolyte in the battery to produce gas. When charging, it can react with the generated lithium to generate lithium oxide, which causes the capacity of the battery to be lost. It is easy to overcharge the battery and generate gas. The decomposition voltage of moisture is low, and it is easy to decompose to generate gas when charging. When this series of generated gases will increase the internal pressure of the battery, and when the shell of the battery cannot withstand it, the battery will explode.

3. Internal short circuit

Due to the internal short-circuit phenomenon, the battery discharges at a high current, generating a lot of heat, burning out the diaphragm, and causing a greater short-circuit phenomenon. In this way, the battery will produce high temperature, causing the electrolyte to decompose into gas, causing excessive internal pressure. When the shell of the battery cannot withstand this pressure, the battery will explode.

During laser welding, heat is transmitted through the housing to the positive electrode ear, so that the temperature of the positive electrode ear is high. If the upper adhesive paper does not separate the positive electrode ear and the diaphragm, the hot positive electrode ear will burn out or shrink the diaphragm paper, causing an internal short circuit and an explosion.

4. External short circuit

The external short circuit may be caused by improper operation or misuse. Due to the external short circuit, the battery discharge current is very large, which will cause the battery to heat up. The high temperature will shrink or completely damage the diaphragm inside the battery, causing an internal short circuit and thus an explosion.

5.High temperature adhesive paper wraps the negative electrode ear

During spot welding of the negative electrode ear, heat is transmitted to the negative electrode ear. If the high-temperature adhesive paper is not affixed, the heat on the negative electrode ear will burn out the diaphragm, causing an internal short circuit and an explosion.

6. The bottom glue is not completely wrapped around the bottom

When the customer spot welds at the bottom of the aluminum-nickel composite belt, a lot of heat will be generated on the bottom shell wall, and the bottom of the conduction pole core. If the high-temperature adhesive paper does not completely wrap the diaphragm, it will burn out the diaphragm, causing an internal short circuit and an explosion.

7.Overcharge

When the battery is overcharged, the excessive release of lithium from the positive electrode will cause the structure of the positive electrode to change, and the excessive release of lithium will easily fail to be inserted into the negative electrode, which will also easily cause lithium to be analyzed on the surface of the negative electrode. Moreover, when the voltage reaches above 4.5V, the electrolyte will decompose to produce a large amount of gas. All of the above may cause an explosion.

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Prevention of thermal runaway for users

You can take a number of steps to prevent lithium battery thermal runaway. This includes replacing old batteries and keeping batteries at an appropriate temperature. If you follow these steps and work with experts who understand the inherent risks of the lithium ion batteries you are using, you can reduce the risk of thermal runaway in your facility or work space.

Always use batteries that are designed for your application

– Make sure you are using batteries that are designed for your application. Lithium ion batteries come in many different shapes and sizes, so be sure to select the right one for your needs.

Always follow the recommended operating conditions

– You should always follow the recommended operating conditions for your lithium ion batteries. For example, if the batteries are designed to operate at a temperature of 32 degrees Celsius, you should keep them at or below that temperature.

Keep batteries within their design temperature range

You should keep batteries within their design temperature range at all times. If you notice the batteries are being operated outside of this range, you should find a way to bring them back below the range.

– Replace old batteries

– If you are using lithium ion batteries in your facility or work space, you should replace the batteries once they have reached the end of their lifespan. Lithium ion batteries often experience a reduction in capacity when they are near the end of their lifespan, which can increase the risk of thermal runaway.

Prevention of thermal runaway for Manufacturers

The safety of lithium-ion batteries is a complex and comprehensive issue. The biggest hidden danger in battery safety is the random internal short circuit of the battery, which produces on-site failure and causes thermal runaway.

Therefore, the development and use of materials with high thermal stability is the fundamental way to improve the safety performance of lithium-ion batteries in the future.

Manufacturers can develop battery thermal runaway from three aspects:

  • Improve battery overcharge protection ability
  • Prevent short circuit of the battery
  • Improve the thermal stability of battery materials

Specific methods are as follows:

  1. Set up a safety valve. And the pressure value range of the safety valve needs to be strictly controlled.
  1. Install a thermistor to prevent the battery from being overcharged or shorted.
  1. Precise thermal management of BMS.

The use of water cooling, air cooling, etc. to cool the battery during battery use.

  1. The use of additives in the electrolyte reduces the flammability of the electrolyte.
  1. Improve the film-forming quality of SEI, such as adding LiCF3SO3to the electrolyte to make more inorganic components in SEI film.
  1. Prevent the reaction of the cathode material with the electrolyte, such as the use of additives in the electrolyte or the coating of the cathode material.
  1. Increase the melting point of the diaphragm, such as: coating ceramic layers on both sides of the diaphragm.
  1. Standardize the use of lithium batteries to reduce or eliminate human factors such as overcharge and over discharge.

Conclusion

Lithium ion batteries are a widely used energy source in the world today. They are particularly useful in applications where high power and a high energy density are needed, such as in electric vehicles and drones.

However, these batteries can experience thermal runaway, which can lead to fires and explosions.

When these batteries experience thermal runaway, they can become very dangerous very quickly.

This is why it is so important to take steps to prevent thermal runaway in your facility or work space by using batteries designed for your application, keeping them within their design temperature range, replacing old batteries and keeping them away from extreme temperatures.

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