70% More EV Range: Inside the 'World’s Strongest' Battery

Researchers at Chalmers University of Technology in Sweden have developed what they call the "world's strongest" battery.

Made from carbon fibre composite, this structural battery can serve as both a power source and part of car structures. 

Led by Professor Leif Asp, the research could help to make EVs lighter as this battery can replace other structural components. 

“The major technological shifts and the green transition require world-class research and long-term capacity building,” says Martin Nilsson Jacobi, President of Chalmers University of Technology.

What is a structural battery?

Research on multifunctional, or “massless”, energy storage systems has been ongoing since roughly 2007. 

These batteries act both as a component and energy storage device, eliminating the need for separate battery packs that can be heavy.

One of the earliest major papers, "Multifunctional Structural Composite Batteries for US Army Applications", was published in 2008 by the US Army Research Laboratory, exploring ways to reduce the weight of equipment carried by soldiers. 

Structural batteries could help to reduce the weight and boost the range of EVs, including cars and aircraft, and even impact smaller technologies like laptops or mobile phones.

While Chalmers’ researchers acknowledge further work is required to increase power output, this technology may be ready for significant industry investment.

Unlike all-solid-state batteries, structural batteries have a rigid skeleton and a liquid or gel-like electrolyte trapped in pores that allows ions to move quickly. 

This format can allow for higher mechanical strength while maintaining conductivity. 

"Investing in light and energy-efficient vehicles is a matter of course if we are to economise on energy and think about future generations," says research leader Leif Asp, who is a professor at the Department of Industrial and Materials Science at Chalmers.

"We have made calculations on electric cars that show that they could drive for up to 70% longer than today if they had competitive structural batteries."

The history of structural batteries

A team including researchers from Chalmers and KTH developed one of the first functioning laminated structural batteries in 2010.

This battery used a carbon fibre weave as the negative electrode and glass fibre as a separator. 

Professor Emile Greenhalgh at Imperial College London led the "STORAGE" project funded by the EU, which looked at structural supercapacitors. 

This team worked with Volvo to create a concept car where the car boot lid and plenum stored energy.

At Texas A&M, Jodie Lutkenhaus focused on aramid nanofibers and graphene in 2017, proving that high mechanical strength could be achieved without relying solely on carbon fibre. 

In 2021, Chalmers created a version using LFP-coated aluminium foil, before it moved towards carbon fibre to reduce weight in 2024. 

Inside Chalmers’ carbon fibre battery

In Chalmers’ 2024 research, it showed that carbon fibres can both store energy and provide stiffness and strength in structural batteries. 

Previous experiments showed that the positive electrode worked when paired with a piece of pure lithium metal, but this is not practical outside of a laboratory setting.

The 2024 research showed that carbon fibre can be used as both the positive and negative electrode by coating the positive side with LFP. 

Cellulose was used as the separator to keep the two layers from short-circuiting, and this whole structure was soaked in a liquid resin and cured to provide rigidity while leaving space for ions to move through. 

The full cell demonstrates a power density of 46 W/kg based on cell mass and remains stable for up to 1,000 charge-discharge cycles. 

Chalmers researcher Richa Chaudhary says: "We have succeeded in creating a battery made of carbon fibre composite that is as stiff as aluminium and energy-dense enough to be used commercially.

"Just like a human skeleton, the battery has several functions at the same time."

The safety of structural batteries

Integrating energy storage directly into the chassis of a vehicle brings new safety considerations.

Unlike a traditional battery pack protected inside a safety cell, a structural battery needs to be its own safety cell. 

Researchers are studying how carbon fibre composites behave under impact. 

Carbon fibre tends to shatter rather than bend, so ensuring batteries don’t catch fire or leak during a collision is important.

It may also be more difficult to swap or repair these batteries, so research needs to prove they can last.