World’s Strongest Battery Paves Way for Light, Energy-Efficient Vehicles

Power Electronics INSIDER

When cars, planes, ships, or computers are built from a material that functions as both a battery and a load-bearing structure, the weight and energy consumption are radically reduced.

A research group at Chalmers University of Technology in Sweden is presenting an advance in so-called massless energy storage — a structural battery that could halve the weight of a laptop, make the mobile phone as thin as a credit card, or increase the driving range of an electric car by up to 70 percent on a single charge.

"We have created a battery made of carbon fiber composite that is as stiff as aluminum and energy-dense enough to be used commercially. Just like a human skeleton, the battery has several functions at the same time," said Chalmers researcher Richa Chaudhary, who is the first author of a scientific article recently published in Advanced Materials.

Research on structural batteries has been going on for many years at Chalmers, and in some stages also together with researchers at the KTH Royal Institute of Technology in Stockholm, Sweden. Leif Asp, Professor at the Department of Industrial and Materials Science at Chalmers, and colleagues published their first results in 2018 on how stiff, strong carbon fibers could store electrical energy chemically, with carbon fiber used as the electrodes in lithium-ion batteries.

A milestone was reached in 2021 when the battery had an energy density of 24 watt-hours per kilogram (Wh/kg), roughly 20 percent of the capacity of a comparable lithium-ion battery. Now it's up to 30 Wh/kg. While this is still lower than today's batteries, the conditions are quite different. When the battery is part of the construction and can also be made of a lightweight material, the overall weight of the vehicle is greatly reduced. Then not nearly as much energy is required to run an electric car, for example.

"Investing in light and energy-efficient vehicles is a matter of course if we are to economize on energy and think about future generations. We have made calculations on electric cars that show that they could drive for up to 70 percent longer than today if they had competitive structural batteries," said research leader Leif Asp.

When it comes to vehicles, of course, there are high demands on the design to be sufficiently strong to meet safety requirements. The research team's structural battery cell has significantly increased its stiffness, or more specifically, the elastic modulus, which is measured in gigapascal (GPa), from 25 to 70. This means that the material can carry loads just as well as aluminum, but with a lower weight.

From the start, the goal was to achieve performance that makes it possible to commercialize the technology. In parallel with the fact that the research is now continuing, the link to the market has been strengthened, through the newly started Chalmers Venture company Sinonus AB, based in Borås, Sweden.

However, there is still a lot of engineering work to be done before the battery cells can take the step from lab manufacturing on a small scale to being produced on a large scale for our technology gadgets or vehicles.

"One can imagine that credit card-thin mobile phones or laptops that weigh half as much as today, are the closest in time. We could also soon have components such as electronics in cars or planes powered by structural batteries. It will require large investments to meet the transport industry's challenging energy needs, but that is where the technology could make the most difference," said Asp.

Structural batteries are materials that, in addition to storing energy, can carry loads. In this way, the battery material can become part of the actual construction material of a product, which means that much lower weight can be achieved.

The developed battery concept is based on a composite material and has carbon fiber as both the positive and negative electrodes — where the positive electrode is coated with lithium iron phosphate. When the previous battery concept was presented, the core of the positive electrode was made of an aluminum foil.

The carbon fiber used in the electrode material is multifunctional. In the anode it acts as a reinforcement, as well as an electrical collector and active material. In the cathode it acts as a reinforcement, current collector, and as a scaffolding for the lithium to build on. Since the carbon fiber conducts the electron current, the need for current collectors made of copper or aluminum (for example), is reduced, which reduces the overall weight even further. Nor are any so-called conflict metals such as cobalt or manganese required in the chosen electrode design.

In the battery, the lithium ions are transported between the battery terminals through a semi-solid electrolyte, instead of a liquid one, which is challenging when it comes to getting high power and for this, more research is needed. At the same time, the design contributes to increased safety in the battery cell, through reduced risk of fire.

Source