Lithium-ion batteries are rechargeable cells with relatively high power for their size. But fires caused by Li-ion batteries have increased fivefold since 2016, especially in the hot summer. So far in 2022, only in Vancouver, Canada, seven people have died in fires associated with the batteries. So it’s necessary to know how Li-ion batteries fail and how to spot a fire earlier.
What is the difference between Lithium batteries and Li-ion batteries?
Lithium batteries, also known as primary batteries, are single-use and incapable of recharge, and contain highly combustible lithium metal. Their real value is that they deliver extremely high energy densities in small configurations and are used where recharging isn’t necessary or feasible.
Li-ion batteries, or secondary batteries that are used worldwide, provide high energy density though lower than the lithium primary and can be recharged again and again. These batteries contain no free lithium metal but do contain lithium ions and highly flammable electrolytes.
How do Li-ion batteries work?
Li-ion batteries were first commercialized by Sony in 1991 for the company’s handheld video recorder. In 2008, Tesla first commercialized a battery-powered electric vehicle. Today, everything you see is powered by batteries, including laptops, cell phones, electric vehicles, hospital equipment, and energy storage systems, to name a few.
Li-ion cells are contained in several layers of aluminum casings and a Li-ion battery pack consists of several Li-ion cells stacked together in modules, temperature sensors, a voltage tap, and an onboard computer (Battery Management System) to manage the individual cells. Like any other cell, the Li-ion cell has a positive electrode (cathode), a negative electrode (anode), and a chemical called electrolyte in between them. While the anode is generally made from graphite (carbon), different lithium materials are used for the cathode – Lithium Cobalt Oxide (LCO), Lithium Nickel Manganese Cobalt (or NMC), etc.
When a charging current is provided to the cell, lithium ions move from the cathode to the anode through the electrolyte. Electrons also flow but take a longer path outside the circuit. The opposite movement takes place during the discharge with the result that the electrons power up the application that has been connected to the cell. When all the ions have moved back to the cathode, the cell has been completely discharged and will need charging.
How do Li-ion batteries catch fire?
Li-ion batteries are capable of spontaneous ignition and subsequent explosion from overheating due to electrical shorting, rapid discharge, overcharging, manufacturing defects, poor design, or mechanical damage. Overheating triggers a process called thermal runaway, which is a chemical reaction within the battery, causing internal temperature and pressure to rise quickly, and then thermal runaway can spread from cell to cell. A white vapor cloud of toxic flammable gases including hydrogen fluoride could be produced, then the cells catch fire, and finally, the gases might explode without warning.
The development process of a Thermal runaway event
Thermal imagers can help
The inspection of the production and storage of Lithium-ion batteries using active thermography becomes more essential. Thermal imagers can detect the hotspot by scanning the full temperature distribution on the battery pack surface at an early stage, giving the system and operators time to activate countermeasures.
A thermal runaway event and its development process captured by a thermal imager
The 600 Series cameras are designed to work in harsh environments at temperatures between -25° to 65°C. Among them, 600CH cameras have a temperature detection range between -20° to 2000°C for discovering chemical fires and other extreme industrial fire conditions. >> Find more about 600s
During the 24/7 continuous monitoring without supervision, an alarm can be triggered automatically when the pre-set critical temperature is exceeded, and heat sources can be localized immediately, even in dusty or smoke-polluted environments. Besides, the camera feed of multi-camera systems can be routed to the control room through ethernet cables, and radiometric video streams can be recorded at 30Hz automatically or manually.
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[1] What is thermal runaway? www.evfiresafe.com
[2] Battery Safety: Top 5 Reasons why Lithium-Ion Batteries Catch Fire. www.ionenergy.co
[3] Battery Inspection Using Advanced Thermography. www.movitherm.com
[4] Korean energy storage system fires blamed on lithium-ion battery faults. www.bestmag.co.uk