The latest arrangement performs ten times better than previous versions.
By being able to use the structure of an item as its battery this holds out the prospect of essentially “massless” energy storage for vehicles, planes and equipment. There is great interest in this for electric cars as batteries constitute a large part of the vehicle’s weight.
The first attempt to make a structural battery was made as early as 2007, but it has so far proven difficult to manufacture batteries with both good electrical and mechanical properties. But now the development has taken a real step forward, with researchers from Chalmers, in collaboration with KTH Royal Institute of Technology in Stockholm, presenting a superior structural battery in terms of electrical energy storage, stiffness and strength.
The energy density is 24Wh/kg, about 20 percent of that of lithium-ion batteries currently in use. But as complete sections of the car can be used for storage, similar storage could be achieved to conventional electric vehicles and the weight of the vehicle can be greatly reduced. Therefore, less energy would be required to drive and brake such an electric car. And with a stiffness of 25GPa, the structural battery can compete with many other commonly used construction materials.
The battery has a negative electrode made of carbon fibre and a positive electrode made of a lithium iron phosphate-coated aluminium foil. They are separated by a fibreglass fabric, in an electrolyte matrix. The researchers now intend to increase performance further by replacing the aluminium foil with carbon fibre as a load-bearing material in the positive electrode, providing both increased stiffness and energy density. The fibreglass separator will be replaced with an ultra-thin variant, which will give a much greater effect – as well as faster charging cycles. The new project is expected to be completed within two years.
Professor Leif Asp, who leads the projects at Chalmers, estimates that the next-generation battery could have three times the energy density and three times the structural stiffness at 75Wh/kg and 75GPa, respectively. This would make the battery as strong as aluminium but at much lower weight.
“The next generation structural battery has fantastic potential. If you look at consumer technology, it could be quite possible within a few years to manufacture smartphones, laptops or electric bicycles that weigh half as much as today and are much more compact”, said Professor Asp, in a statement. In the longer term the use of the structural battery would be extended to electric cars, electric planes and satellites.
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