The new massless energy storage, wherein the car body acts as a battery, could help in reducing the weight of an Electric Vehicle by 50%.
The major drawback of an EV is its weight, more power is consumed in order to overcome this weight and move the vehicle from one place to another. But what if I told you that the conventional method of battery storage can be ditched and can integrate the batteries into the car's structure itself?
Yes, you heard it right, scientists at the Chalmers University of Technology in Gothenburg and the KTH Royal Institute of Technology in Stockholm might have the answer in what they call massless energy storage.
Massless energy storage is a modern equivalent, integrating lithium-ion electrochemistry into a structural material from which a car can be made: carbon fiber composite. Existing lithium-ion batteries have carbon negative electrodes (anodes) and metal-oxide positive electrodes (cathodes), both of which can absorb lithium ions as they migrate from one to the other through an electrolyte during charge and discharge.
The Swedish research project, which started back in 2007, has yielded a method of using carbon fibres to form an anode, with a cathode made from iron-phosphate-coated aluminium foil, separated by a glass fibre fabric in an electrolyte mix. A new concept replaces the foil with carbon fibre for the positive electrode and combines it with a thinner separator, therefore producing a stiffer energy-storage material that has the strength of aluminium but is lighter.
The research initially focused on the microstructure of carbon fibre. The scientists discovered that fibers with small and poorly oriented crystals have lower stiffness than fibres with large, well-oriented crystals but have good electrochemical properties, making them suitable anode and cathode material. The structural carbon fibre market is focused more on high-grade aircraft-spec material, but the slight decrease in stiffness isn’t a problem for use in cars.
Although promising, the new material doesn’t have as good energy density as a conventional battery. The first-stage version has an energy density by weight of 24Wh per kg (or 40Wh per kg for a complete battery pack), which is only 17% of the energy density of the Kia e-Niro’s 64kWh battery, for instance. However, losing a conventional battery of that size would shave around 460kg from the weight of the car and have a dramatic, favorable effect on range and performance.
The question then would be how much of the material could be incorporated into a car’s structure and how the trade-off between reduced weight and lower energy density would work out. Those working on the project hope that the energy density of the second-stage version with a carbon fibre anode and cathode could get as much as 75Wh per kg.
Although its early days and cost will also inevitably be a challenge, the potential for incorporating material into a car’s structure that isn’t only able to store energy to power the traction motor but also to power auxiliary equipment such as the heating, lights, and air-con or to store energy recovered by regenerative braking is clear.
The material might also prove to be a good fit with evolving EV architectures, which could be designed from the start with massless energy storage in mind.
-by Amaan Attar
(Reports via AutoCar UK)
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