The technology that makes lithium-ion batteries safer


In case of overheating Lithium ion (Li-ion) batteries are liable to catch fire or even explode. Yet they’re used to power everything from smartwatches to electric vehicles, thanks to the vast amounts of energy they can store in small spaces.

A recent research paper published in the American Chemical Society’s Nano Letters proposes a possible solution with a new technology capable of quickly braking a Li-ion battery, turning it off when it gets too hot.

The chemistry found in many batteries is essentially the same: electrons are transported through an electronic device in a circuit from one battery electrode to another. But in a Li-ion cell, the electrolyte liquid that separates these electrodes can evaporate when it overheats, causing a short circuit.

In some cases, a short circuit can lead to thermal runaway, a process in which a cell heats up uncontrollably. When multiple Li-ion cells are wired together, such as in electric vehicles, thermal runaway can spread from unit to unit, resulting in a very large fire that is difficult to fight.

To prevent this, some batteries now have safety features, such as external vents, temperature sensors, or flame-retardant electrolytes. But these measures often come too late or harm performance.

Thus, Yapei Wang, Kai Liu and their colleagues from Tsinghua and Renmin universities in Beijing, China wanted to create a Li-ion battery that could die out quickly, but also perform as well as existing technologies.

The researchers used a heat-sensitive shape-memory polymer coated in a conductive copper spray to create a material that would pass electrons most of the time, but become an insulator when overheated.

At approximately 197°F, a microscopic 3D pattern programmed into the polymer appears, breaking the copper layer and stopping the flow of electrons. This permanently shuts down the cell but prevents a potential fire. At this temperature, however, traditional cells continued to operate, putting them at risk of thermal runaway if they got hot again. Under regular operating temperatures, the battery with the new polymer maintained high conductivity, low resistivity and life similar to that of a traditional battery cell. Researchers say this technology could make Li-ion batteries safer without having to sacrifice performance.

The authors acknowledge funding from the National Natural Science Foundation of China, the Tsinghua University-China Petrochemical Corporation Joint Institute for Green Chemical Engineering, and the Tsinghua-Foshan Special Fund for Innovation.


This news seems at first glance to be very good news. For a battery experiencing rapid internal heating, this seems like a great idea. What is not in your humble writer’s experience is what proportion of lithium ion battery fires are due to internal heating versus punctures, crushing, dendrites, water soaks salt and the rest. If the battery is internally shorted, your drive does not see the new application technology offering much defense.

Researched “Lithium Ion Battery Fire Causes”. A quick glance suggests that “most” lithium-ion battery fires stem from “internal overheating” without the cause of the overheating being specified in detail. The National Fire Protection Association report is now over 6 years old. We remain in a very uninformed state.

Lithium-ion battery fires are not common. Almost “rare”, but not really rare. If one falls on you, there’s a disaster afoot. :

By Brian Westenhaus via New energy and fuel

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