Soon structural batteries, for “massless” energy storage?

A structural battery is a multi-material capable of providing structural properties while storing electrochemical energy. A team of researchers has just presented a new type of structural battery whose performance is 10 times higher, both in terms of electrical energy storage and rigidity or mechanical resistance.

The weight of the batteries is currently a brake on the development of electric planes and a handicap to the development of clean vehicles. This work, carried out by Swedish researchers from the Chalmers University of Technology, in collaboration with the Royal Institute of Technology KTH in Stockholm, opens the way to “massless” energy storage.

A technology that combines energy storage and mechanical resistance

While the structural battery concept is not new, the results achieved so far have not lived up to expectations. In 2007, the US Army Research Laboratory (ARL) made the first attempt to manufacture a laminated structural composite. Unfortunately, the resulting composite structural battery was unable to store electrochemical energy due to poor electrical insulation. On the other hand, it had interesting mechanical characteristics.

Meanwhile, several attempts have been made by others, notably through the use of gel electrolytes and new types of electrodes, but the mechanical properties this time were too weak.

Until now, no structural battery technology seemed to have both good energy storage capacity and sufficient mechanical strength.

A new type of stronger structural battery, based on carbon fiber

The new battery technology proposed by the research team consists of a carbon fiber negative electrode, a positive electrode composed of an aluminum film, a glass fiber separator and a structural electrolyte matrix (SBE).

It is the result of many years of research, their work having been named by Physics World as one of the ten greatest scientific breakthroughs of 2018.

Steps in making a structural battery composite (Credit: Adv Energy and Sustain Res, Volume: 2, Issue: 3, First published: 27 January 2021, DOI: 10.1002/aesr.202000093)

The paper recently published in open access in the journal Advanced Energy & Sustainability Research thus highlights interesting performances. With a stiffness of 25 GPa, this structural battery prototype is in theory able to compete with many materials on the market.

Furthermore, the battery they developed has an energy density of 24 Wh/kg, which is equivalent to about 20% of the capacity of a lithium ion battery. If this may not seem like much, it should also be taken into account that this material will make it possible to lighten vehicles by integrating the battery directly into their structure. The energy consumption of a vehicle in operation will thus be considerably reduced, which is likely to greatly reduce the environmental footprint.

An infinity of long-term applications

Leif Asp, first author of the study, is enthusiastic, saying in a press release: “The next generation structural battery has fantastic potential. If we consider consumer technologies, it would be quite possible, in a few years, to manufacture smartphones, laptops or electric bicycles that weigh half as much as today by being much more compact. “.

In the long term, this type of battery probably has a very wide range. When the performance is sufficient and the technology is mature, it will then become conceivable to design planes, cars or even satellites powered by this type of ultra-light structural battery.

Leif Asp thus confirms that their work arouses strong interest from industrialists in different fields. They have just launched a new project funded by the Swedish National Space Agency. Its aim is to improve the performance of structural batteries by replacing, for example, the aluminum foil at the positive electrode with carbon fibre, in order to improve rigidity and energy density.

Because the performances are still largely improvable. Leif Asp, professor at Chalmers and responsible for the project, estimates that an energy density of 75 Wh/kg and a stiffness of 75 GPa are realistic objectives. If such numbers are ever achieved, then next-generation structural batteries will be as strong as aluminum, but much lighter.

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