The main research application area of the researchers is many vehicles such as automobiles or airplanes. Most of their body or fuselage are composed of structural lithium-ion batteries. Multifunctional carbon fibers can be used as battery electrodes and carrier materials. Ion batteries in which the negative electrode is made of carbon fiber and the positive electrode is made of carbon fiber coated by the cathode. Charging the battery means that the negative electrode is full of positively charged lithium ions.
A study led by Chalmers University of Technology in Sweden shows that carbon fibers can be used as battery electrodes to store energy directly. They elaborated this research result in "Graphitic microstructure and performance of carbon fibre Li-ion structural battery electrodes", which opened a new way for the development of structural batteries, and carbon fiber is expected to become a part of the energy system. The use of this versatile material can greatly reduce the weight of aircraft and is the key to meeting the challenges of future electrification of vehicles.
Airliners need to be much lighter than they are today to be powered by electricity. Reducing weight is also very important for vehicles. Because only after reducing the weight can you extend the driving distance per battery charge.
Leif Asp, a professor of materials and computational mechanics at Chalmers University of Science and Technology, has conducted in-depth research on the development of carbon fibers, with the aim of pushing the carbon fiber's capabilities to the limit so that it has more than just enhanced functions. For example, carbon fibers can also store energy.
Asp said, "The car body is more than just a load-bearing element. It can also be used as a battery. Carbon fiber can also be used for other purposes, such as collecting kinetic energy, sensors or energy and data conductors. A part of the aircraft body, rather than a separate component, can reduce weight by 50%. "
Asp led a multidisciplinary research group who recently published a study on how the microstructure of carbon fibers affects its electrochemical performance, examining the ability of carbon fibers to function as electrodes in lithium-ion batteries. So far, this is an unexplored research area.
Researchers have studied the microstructure of different types of commercial carbon fibers. They found that carbon fibers with smaller and poorer-oriented crystals had good electrochemical performance but lower relative stiffness. If compared with carbon fibers with large and well-oriented crystals, their stiffness is greater, but the electrochemical performance is too low to be suitable for structural batteries.
Asp said: "We now know how to make multifunctional carbon fiber to achieve high energy storage capacity, while also ensuring sufficient stiffness. For many applications such as automotive, a slight decrease in stiffness is not a major issue. The current market The main carbon fiber composites are very expensive, and their stiffness is tailored to the use of the aircraft. Therefore, carbon fiber manufacturers have great potential for improvement. "
In this study, the carbon fiber with good electrochemical performance is slightly harder than steel, while the carbon fiber with poor electrochemical performance is only twice as stiff as steel.
Asp explained that researchers are working with car companies and airlines. For the aviation industry, it may be necessary to increase the thickness of carbon fiber composites to compensate for the reduced stiffness of structural batteries, which will also increase their energy storage capacity.
Asp said: "The key is to systematically optimize vehicles based on weight, strength, stiffness and electrochemical characteristics. This is a new way of thinking for the automotive industry and it is more used to optimize individual components. There is nothing like traditional batteries That's as efficient, but because they have the structural carrying capacity, they can systematically get very big gains. "
He continued, "In addition, the lower energy density of structured batteries will make them safer than standard batteries, especially since they also do not contain any volatile substances."