World’s most powerful battery paves way for light, energy-efficient vehicles

Weight reduction in vehicles and devices directly translates to improved energy efficiency. Traditional lithium-ion batteries, while powerful, limit the energy density needed for groundbreaking advancements in electric vehicles, aircraft, and portable electronics.

Enter structural batteries—a transformative concept combining energy storage with structural integrity, heralding a new era in multifunctional material science.

Structural batteries serve dual purposes: storing energy and bearing mechanical loads. Unlike conventional batteries that only supply energy, these batteries are integrated into the structure of a device or vehicle. By reducing system weight, they enable increased energy efficiency and extended range.

For instance, replacing an electric vehicle's roof with a structural battery could cut weight by up to 20%, freeing space for additional batteries and significantly improving mileage.

The potential applications are vast. A structural battery could halve a laptop’s weight or make smartphones as thin as a credit card. Electric cars, powered by such batteries, could increase their range by as much as 70%.

As researcher Richa Chaudhary from Chalmers University of Technology in Sweden explains, this is akin to a "human skeleton," performing multiple functions simultaneously.

Structural batteries rely on advanced materials like intermediate modulus polyacrylonitrile-based carbon fibers (PAN-CF). These fibers strike the optimal balance between mechanical strength and electrochemical properties, allowing them to act as both electrodes and reinforcement structures.

Recent studies reveal promising results when carbon fibers are coated with lithium iron phosphate (LiFePO₄ or LFP) using electrophoretic deposition. However, initial tests showed poor capacity retention of 47% after 100 cycles due to weak bonding between LFP and carbon fibers.

As LFP nanoparticles detach from the carbon fibers during repeated charging cycles, performance diminishes. By incorporating reduced graphene oxide (rGO) into the design, researchers improved adhesion and achieved a specific capacity of 72 mAh g⁻¹ at a 2C-rate, although this remains below the theoretical potential.

Further innovations include using carbon fibers as the anode and combining them with aluminum foil coated in LFP as the cathode. Testing various separators revealed that thinner materials reduced internal resistance, resulting in higher energy densities. For instance, the Whatman GF plain weave separator outperformed thicker alternatives, doubling energy density from 12 Wh/kg to 24 Wh/kg.

Chalmers University of Technology has been at the forefront of structural battery research. Its groundbreaking work began in 2018, showcasing the ability of stiff carbon fibers to store electrical energy.

The most recent breakthrough saw the creation of a carbon fiber composite battery boasting an energy density of 30 Wh/kg and an elastic modulus of 70 GPa—comparable to aluminum's stiffness but at a fraction of the weight.

As research leader Leif Asp noted, “Investing in light and energy-efficient vehicles is a matter of course if we are to economize on energy and think about future generations.” With these advancements, structural batteries could make electric cars 70% more energy-efficient while meeting strict safety standards.

The journey from lab to market is challenging but increasingly promising. The Chalmers team has formed Sinonus AB to accelerate commercialization. Applications in portable electronics, such as credit card-thin smartphones or ultra-light laptops, may be the first to benefit. In the long term, this technology could revolutionize aerospace and automotive industries.

However, significant engineering hurdles remain. For instance, transitioning from liquid to semi-solid electrolytes is critical for achieving higher power densities and improved safety. Semi-solid electrolytes reduce fire risks, an important factor in commercial adoption.

Structural batteries offer several environmental benefits. By eliminating the need for heavy current collectors made of aluminum or copper, these batteries reduce material usage. Additionally, their design avoids conflict metals like cobalt, frequently associated with traditional lithium-ion batteries.

The integration of carbon fibers into both electrodes simplifies the overall structure, further lowering weight. In the anode, the fibers act as reinforcement, current collectors, and active material. In the cathode, they support lithium deposition, eliminating unnecessary components and streamlining production.

Despite significant progress, challenges remain. Liquid electrolytes currently dominate research, limiting the structural battery's full potential. Additionally, using carbon fibers exclusively as negative electrodes or relying on commercial LFP foils for positive electrodes restricts innovation.

Addressing these limitations, Chalmers researchers recently demonstrated an all-carbon-fiber structural battery using pristine carbon fibers as the anode and LFP-coated fibers as the cathode. Embedded in a biphasic solid-liquid electrolyte system, this design achieved an energy density of 33.4 Wh/kg, with an impressive Young's modulus of 38 GPa.

Improvements in manufacturing techniques have further increased energy density to 42 Wh/kg while maintaining mechanical robustness. These advances underline the potential for structural batteries to integrate seamlessly into large-scale industrial applications, such as cars, planes, and drones.

The global interest in structural batteries is growing, particularly within the automotive and aerospace sectors. These industries stand to benefit the most from lighter, more energy-efficient designs. However, significant investments in research and manufacturing are needed to meet the energy demands of these sectors.

As Professor Asp points out, “One can imagine that credit card-thin mobile phones or laptops that weigh half as much as today are the closest in time.” With structural batteries poised to disrupt the status quo, the dream of multifunctional materials driving our vehicles, powering our gadgets, and reducing environmental impact may soon become reality.

Note: Materials provided above by The Brighter Side of News. Content may be edited for style and length.

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