Lithium-ion batteries power most of our daily gadgets and electric vehicles. But did you know these high-energy density batteries come with the risk of a thermal runaway? In this blog, we’ll cover everything you need to know about lithium battery thermal runaway – from what exactly it is and what causes it to how to prevent it. By the end, you’ll understand this hot battery safety topic and solution options to manage it.
What is Lithium Battery Thermal Runaway?
In simple terms, thermal runaway refers to a dangerous self-heating feedback loop in lithium batteries. Typically, a battery’s internal temperature rises gradually during operation or charging. But sometimes, usually due to an internal short circuit or other failure, heat builds up rapidly.
This kicks off chemical reactions that generate more heat. And before you know it, the battery is in thermal runaway mode. Here, temperatures can exceed 500°C in minutes! This extreme heat further accelerates exothermic chemical reactions, releasing combustible gas, eventually leading to fire or battery explosion.
So in summary, lithium battery thermal runaway is an uncontrolled self-heating effect that leads to overheating and potential safety issues. Read on to learn what causes it and how to prevent your lithium batteries from ending up in this catastrophic failure mode.
What Causes Thermal Runaway in Lithium Batteries?
First, we need to know what causes thermal runaway in batteries. Several triggers start the vicious thermal runaway cycle in lithium-ion batteries:
- Internal short circuit– Caused by burrs, metal particles, or other contaminants inside the cell interrupting the insulation barrier between the electrodes. This allows abnormal current flow leading to excessive heat buildup.
- External short circuit– Typically due to an electrical system failure or damage to battery terminals/cables allowing current to bypass the actual battery cell pathway. The excessive current flow causes extreme resistive heating.
- Overcharging– Forcefully pumping too much current into a lithium battery beyond its safe limit during charging leads to the cathode and anode heating up due to electrochemical inefficiencies.
- Overheating– Exposure to high ambient temperatures also heats the battery internals, bringing cells closer to the thermal runway threshold.
- Manufacturing defects– Improper winding, contamination, etc. introduce flaws that make batteries more prone to short circuits and heating.
As you can see, protecting lithium batteries from thermal runaway requires a multi-pronged approach considering different use conditions and failure modes.
The Serious Dangers of Thermal Runaway
It’s critical to prevent lithium battery thermal runaway because once initiated, there is no stopping the chemical chain reaction without rapid cooling. And the consequences, as Samsung learned the hard way with the Galaxy Note 7, are serious:
- Extreme Heat Generation– In thermal runaway, temperatures inside battery cells spike up incredibly fast – from room temperature to over 500°C in minutes. This heat further fuels the runaway reaction.
- Fire and Explosion– The intense heat vaporizes the organic electrolyte into inflammable gas. Combined with oxygen released from cathode decomposition, this gas ignites resulting in battery fire or even explosion.
- Toxic Emissions– The heat also decomposes other cell components like the electrolyte salt lithium hexafluorophosphate which releases hydrofluoric acid vapor. Other toxic gases like carbon monoxide may be generated making battery fumes extremely dangerous.
With such severe risks to human safety and assets, it’s evident why properly preventing thermal runaway is non-negotiable for lithium battery applications.
How to Prevent Lithium Battery Thermal Runaway
So what’s the best way to stop lithium batteries from going into thermal runaway during operation or charging? Here are the most effective prevention strategies:
- Battery Management Systems (BMS)– Also called protection circuits, BMS monitor critical parameters like cell voltage, current and temperature to detect conditions risking thermal runaway. Upon detection, they cut off the current flow and apply overvoltage protection preventing further self-heating.
- Thermal Management System– These active cooling systems use air or liquid to regulate the temperature of battery cells and packs within safe operating limits. This prevents overheating from external sources like high ambient temperatures or internal heat buildup.
- Improved Mechanical Design– Enhancing battery cell and pack mechanical design increases their resilience to crush, vibration, penetration or other mechanical damage that may trigger internal shorts. Protective housing also shields them from external heat.
- Quality Manufacturing– Following stringent quality control during lithium cell manufacturing lowers risks of contaminants or component damage leading to cell vulnerabilities.
- Fuses & Current Interrupters– Secondary protective components like fuses melt and cause an open circuit when excess current flows while current interrupters are electronically controlled switches programmed to cut-off current flow when they sense overcurrent or overtemperature.
Together, these five approaches form an effective framework to catch abnormal battery conditions early and prevent progression to thermal runaway. Thermal management systems play a key role in regulating temperatures to avoid external heat triggering the runaway reaction in the first place.
Do Battery Management Systems Fully Prevent Thermal Runaway?
As the method of preventing battery thermal runaway, now there is a common question – can battery management systems offer complete protection against lithium battery thermal runaway?
The answer is they significantly reduce but cannot fully eliminate the risks. No system is perfect. For example, while a BMS can detect and respond to extremely fast heating of just a small section of the cell, runaway triggering from an internal short on a tiny inadvertently missed burr or contaminant particle is difficult.
Similarly, false temperature measurements from a damaged sensor or software bugs may hamper response. Human errors in setting protection thresholds also affect robustness. So while having an actively monitoring BMS lowers risks tremendously compared to unprotected batteries, the possibility of a thermal runaway due to unforeseen failure sequences exists nonetheless.
This is why we recommend further safeguards like current interrupters and even active cooling protection beyond just BMS to enforce true fault tolerance for lithium battery systems, especially large packs with abundant stored energy.
Further read: Overtemperature protection in BMS
How MOKOENEGY Helps Secure Battery Systems
MOKOENERGY provides cutting-edge battery thermal management technology tailored to safeguard lithium cells, modules, and packs from thermal runaway during operation, charging, and storage.
Our solutions combine multilayer safety redundancy with proprietary analytics and cloud connectivity for comprehensive protection. With thermal research and analytics at the world’s leading electric vehicle and grid storage companies, our engineers have unparalleled expertise in lithium battery safety. MOKOENERGY battery management hardware and software solutions are deployed across automotive and home energy storage helping clients meet their reliability goals while avoiding thermal runaway risks.
Conclusion
Lithium batteries are crucial for electric mobility and clean energy solutions. However uncontrolled thermal runaway poses grave safety hazards from intense heat, fire, and toxic gas releases. Thankfully, the combination of battery management systems, design improvements, and analytics software provides robust protection against failure sequences triggering this runaway reaction.
With seasoned engineers and advanced technology, MOKOENERGY partners with enterprises around the world to secure their lithium battery assets. Get in touch to learn how our thermal management systems can cost-effectively safeguard your projects and peace of mind!
