Could independent battery packs be a thing of the past?

Electric cars could soon be able to store their energy within carbon-fibre body panels, enabling manufactures to conserve weight and space, according to a new study.

The paper from Chalmers University of Technology in Sweden found carbon fibres could function as battery electrodes. Because of this, the carbon-fibre structure of a car could act as a battery, holding charge for the electric motors.

A multidisciplinary team of researchers conducted the study, led by Leif Asp, professor of material and computational mechanics at Chalmers University of Technology.

The researchers compared a number of commercially-available carbon-fibres, assessing them for both relative stiffness and electrochemical properties.

The study found the stiffest forms of carbon fibre, such as the types used in aviation had poor electrochemical properties. However, the forms of carbon fibre with ‘small and poorly oriented crystals’ proved to have good electrochemical properties – enough for them to act similarly to a battery.

Even the weakest carbon fibres tested were slightly stiffer than steel, with Asp explaining “a slight reduction in stiffness is not a problem for many applications, such as cars.

“The market is currently dominated by expensive carbon-fibre composites whose stiffness is tailored to aircraft use. There is therefore some potential here for carbon-fibre manufacturers to extend their utilisation,” he explained.

“The key is to optimise vehicles at system level – based on the weight, strength, stiffness and electrochemical properties. That is something of a new way of thinking for the automotive sector, which is more used to optimising individual components.

“Structural batteries may perhaps not become as efficient as traditional batteries, but since they have a structural load-bearing capability, very large gains can be made at system level,” he continued.

The biggest hurdle in this technology making its way to production cars may well prove to be cost. Carbon-fibre is still substantially more expensive than traditional materials such as steel, and is also substantially harder to recycle.

Proving the technology’s longevity over the tough life of a conventional car is another potential hurdle.

The study, which can be read in full here, was funded by the Swedish Energy Agency, the Swedish Research Council and Alistore European Research Institute.