In a study recently published in Sustainability of nature, we describe our design of a self-extinguishing rechargeable battery. It replaces the most commonly used electrolyte, which is highly combustible (a medium composed of a lithium salt and an organic solvent), with materials found in a commercial fire extinguisher.
An electrolyte allows lithium ions carrying an electrical charge to move through a separator between the positive and negative terminals of a lithium-ion battery. By modifying affordable commercial coolants to function as battery electrolytes, we were able to produce a battery that puts out its own fire.
Our electrolyte performed well over a wide temperature range, from approximately minus 100 to 175 degrees Fahrenheit (minus 75 to 80 degrees Celsius). The batteries we have produced in the laboratory with this electrolyte carry heat away from the battery very well and effectively extinguish internal fires.
We subjected these batteries to the nail penetration test, a common method for evaluating the safety of lithium-ion batteries. Driving a stainless steel nail into a charged battery simulates an internal short circuit; if the battery catches fire, it fails the test. When we drove a nail into our charged batteries, they withstood the impact without catching fire.
By nature, the temperature of a battery changes as it charges and discharges, due to internal resistance, that is, opposition to the flow of lithium ions in the battery. battery. High external temperatures or uneven temperatures inside a battery seriously threaten the safety and durability of batteries.
When a lithium-ion battery supplies power to a device, lithium ions – atoms carrying an electrical charge – move from the anode to the cathode. The ions move in the opposite direction when recharging. Credit: Argonne National Laboratory/Flickr, CC BY-NC-SA
Energy-dense batteries, such as lithium-ion versions widely used in electronics and electric vehicles, contain an electrolyte formulation dominated by highly flammable organic molecules. This increases the risk of thermal runaway, an uncontrollable process in which excess heat inside a battery accelerates unwanted chemical reactions that release more heat, triggering other reactions. The temperature inside the battery can rise several hundred degrees in one second, causing a fire or explosion.
Another safety issue arises when lithium-ion batteries are charged too quickly. This can cause chemical reactions that produce very sharp lithium needles called dendrites on the battery’s anode, the negatively charged electrode. Eventually, the needles enter the separator and reach the other electrode, shorting the inside of the battery and causing overheating.
As scientists studying energy production, storage and conversion, we have a keen interest in the development of safe, energy-dense batteries. Replacing flammable electrolytes with a flame-retardant electrolyte has the potential to make lithium-ion batteries safer and can buy time for longer-term improvements reducing the inherent risks of overheating and thermal runaway.
How we did our job
We wanted to develop an electrolyte that was nonflammable, would easily conduct heat away from the battery, could operate over a wide temperature range, would be very durable, and would be compatible with any battery chemistry. However, most known nonflammable organic solvents contain fluorine and phosphorus, which are expensive and can have harmful effects on the environment.
Instead, we focused on adapting affordable commercial coolants that were already widely used in fire extinguishers, electronic testing and cleaning applications, so that they could function as battery electrolytes.
We focused on a mature, safe and affordable commercial fluid called Novec 7300, which has low toxicity, is non-flammable and does not contribute to global warming. By combining this fluid with several other durability-increasing chemicals, we were able to produce an electrolyte with the characteristics we were looking for and allowing a battery to charge and discharge for a full year without losing significant capacity.
What we still don’t know
Since the alkali metal lithium is rare in the Earth’s crust, it is important to study how well batteries that use other, more abundant alkali metal ions, such as potassium or sodium, perform in comparison. For this reason, our study mainly focused on self-extinguishing potassium-ion batteries, although it also showed that our electrolyte works well to make self-extinguishing lithium-ion batteries.
It remains to be seen whether our electrolyte can work as well for other types of batteries in development, such as sodium-ion, aluminum-ion and zinc-ion batteries. Our goal is to develop practical, environmentally friendly and durable batteries regardless of their ion type.
For now, however, because our alternative electrolyte has similar physical properties to currently used electrolytes, it can be easily integrated into current battery production lines. If the industry adopts it, we hope that companies will be able to manufacture non-flammable batteries using their existing lithium-ion battery facilities.
More information:
Xianhui Yi et al, Safe electrolyte for long cycle alkaline-ion batteries, Sustainability of nature (2024). DOI: 10.1038/s41893-024-01275-0
Provided by The Conversation
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Quote: Self-extinguishing batteries could reduce the risk of deadly and costly battery fires (February 6, 2024) retrieved February 6, 2024 from
This document is subject to copyright. Apart from fair use for private study or research purposes, no part may be reproduced without written permission. The content is provided for information only.
