A new battery that’s temperature-resilient could mean electric vehicles will be better able to withstand extreme cold — and ultimately travel longer on a single charge.
Researchers at the University of California San Diego have created a lithium-ion battery that performs well in freezing cold and scorching heat.
They used a special temperature-resistant electrolyte – the substance found in batteries that allows electricity to flow.
If introduced into electric vehicle production, the battery could allow electric vehicles in cold climates to travel further on a single charge.
They can also reduce the need for expensive cooling systems to keep a vehicle’s battery pack from overheating in hot climates.
Engineers at the University of California San Diego have developed a lithium-ion battery that performs well in freezing cold and scorching heat. Such batteries could allow electric vehicles in cold climates to travel further on a single charge. They can also reduce the need for a cooling system to keep a car’s battery pack from overheating in hot climates (stock image)
Currently, temperatures that are too hot or too cold can adversely affect the performance of batteries in electric vehicles, such as slowing down the charging rate and reducing the distance the vehicle can travel before it needs to be recharged.
Drivers’ fear of running out of battery before they find their way to another charging station is known as ‘range anxiety’, and is seen as a barrier to mass adoption of vehicles Environmentally friendly electricity.
“You need to operate at high temperatures where ambient temperatures can reach triple digits and roads get hotter,” said Professor Zheng Chen at the UC San Diego Jacobs School of Engineering.
‘In electric vehicles, the battery packs are usually located under the floor of the vehicle, near these hot roads.
‘Also, the battery heats up only when current is passed during operation. If batteries cannot withstand this heating at high temperatures, their performance will rapidly degrade. ‘
Batteries have three main components – an anode, a cathode, and an electrolyte.
The electrolyte (usually a chemical substance, in liquid or viscous form) separates the anode and cathode and moves the flow of charge between the two.
Lithium ion batteries move lithium ions from the cathode to the anode during charging.
The batteries that Chen and colleagues have developed are both cold and heat resistant thanks to their electrolyte, a liquid solution of dibutyl ether mixed with a lithium salt.
What’s special about dibutyl ether is that its molecules are weakly bound to lithium ions, which means that the electrolyte molecules can easily remove lithium ions as the battery runs.
This weak molecular interaction improves battery performance at sub-zero temperatures.
Lithium ion batteries have two electrodes – one made of lithium (cathode) and one electrode from carbon (anode) – submerged in a liquid or lake called an electrolyte. When a battery is charged, electrons attached to ions flow through a circuit, powering a device
In addition, dibutyl ether is readily endothermic because it is liquid at high temperatures – it has a boiling point of 286°F or 141°C.
In tests, the proof-of-concept battery was found to retain 87.5% and 115.9% of its energy capacity at -40°C and 50°C (-40°F and 122°F), respectively.
The new batteries also have a high ‘combined efficiency’ of 98.2% and 98.7% at these temperatures, respectively, meaning they can go through more charge and discharge cycles before shutting down. .
The researchers say their electrolyte is also compatible with lithium-sulfur batteries, a type of rechargeable battery with an anode made of lithium metal and a cathode made of sulfur.
Lithium-sulfur batteries can store twice as much energy per kilogram as today’s lithium-ion batteries, potentially doubling the range of electric vehicles without increasing the weight of the battery pack.
Most electric cars run on lithium-ion batteries, which are charged and discharged by lithium ions moving between negative (anode) and positive (cathode) electrodes. Pictured, electric cars are charging in Mosjøen, Norway
However, lithium-sulfur batteries have several problems that currently hinder their commercialization, such as reactivity, especially at high temperatures.
Additionally, lithium metal anodes are prone to forming needle-like structures called dendrites that can penetrate battery components, causing short circuits.
As a result, lithium-sulfur batteries only last up to dozens of cycles.
The dibutyl ether electrolyte developed by the UC San Diego team prevents these problems, even at high and low temperatures.
The battery they tested has a longer cycle life – the number of charge and discharge cycles it can complete before it loses performance – than typical lithium-sulfur batteries.
The team also engineered the sulfur cathode to be more stable by coupling it with a polymer, which prevents more sulfur from dissolving into the electrolyte.
In future research, the team plans to scale up the chemistry of the battery, making it operate at even higher temperatures and extending cycle life even further.
They described their temperature-resistant battery in a paper published in the journal Proceedings of the National Academy of Sciences.