Lithium-ion batteries have become the backbone of modern energy storage, powering everything from smartphones to electric vehicles (EVs) and renewable energy systems. However, one of the significant challenges faced by lithium-ion batteries is managing the heat generated during charging and discharging cycles.

The excessive heat can lead to degradation of battery components, reduced lifespan, and, in extreme cases, thermal runaway—a phenomenon where a battery overheats and catches fire or explodes due to uncontrolled chemical reactions.

Thermal runaway in lithium-ion batteries occurs when the internal temperature of the battery rises faster than it can dissipate, leading to a dangerous feedback loop. Traditional current collectors made of copper and aluminum, though effective, have limited thermal conductivity, contributing to the accumulation of heat within the battery cells.

Graphene: a revolutionary material

Graphene, a single layer of carbon atoms arranged in a hexagonal lattice, is renowned for its exceptional properties, including high electrical and thermal conductivity, mechanical strength, and flexibility. Its discovery earned the Nobel Prize in Physics in 2010 for its potential to revolutionize various industries, particularly electronics, materials science, and energy storage.

Graphene’s thermal conductivity is approximately 1400.8 W m-1 K-1, which is significantly higher than traditional materials like copper (400 W m-1 K-1) and aluminum (235 W m-1 K-1). This makes graphene an ideal candidate for enhancing the thermal management of lithium-ion batteries.

New production process for graphene foils

The new method, developed by the Swansea, Wuhan University of Technology, and Shenzhen Universities, is the first in the world to enable the production of defect-free graphene foils on an industrial scale. The foils are produced using a continuous heat-pressing process, which ensures consistent quality and scalability. The unique aspect of this process is its ability to create long, uniform sheets of graphene without compromising its structural integrity, a challenge that has plagued graphene manufacturing for years.

This continuous production technique can generate graphene foils in lengths of up to several kilometers, making it feasible for large-scale applications in battery production. For instance, a 200-meter-long graphene film with a thickness of 17 μm was demonstrated by the researchers, showcasing its potential for use in flexible electronics and other advanced applications.

Industrial-scale graphene production represents a significant advancement, overcoming previous limitations of small-scale, high-cost production methods. This new capability allows for customization of graphene foil thickness, which can be optimized for various applications, enhancing both safety and performance.

Implications for battery performance and safety

“This is an important advance in battery technology. Not only does it improve safety by handling heat more efficiently, but it also increases energy density and lifetime,” says Dr. Rui Tan, a researcher at Swansea University and one of the lead authors of the study.

The primary advantage of graphene-based current collectors lies in their ability to efficiently dissipate heat, reducing the likelihood of exothermic reactions that can lead to battery failure. By acting as a thermal barrier, these collectors prevent the formation of flammable gases and inhibit oxygen from entering the battery cells, addressing one of the critical factors in preventing catastrophic failures.

The use of graphene also has the potential to enhance the energy density of batteries. Higher thermal conductivity allows batteries to operate at higher power levels without overheating, thereby increasing their overall energy output. This is particularly advantageous for electric vehicles and renewable energy systems, where both performance and safety are paramount.

Expanding applications: beyond lithium-ion batteries

The implications of this new graphene production process extend beyond lithium-ion batteries. The international research team is exploring its application in other types of energy storage systems, such as redox flow batteries and sodium-ion batteries. These alternative battery technologies are being developed to address specific limitations of lithium-ion batteries, including resource scarcity, cost, and environmental impact.

Graphene’s properties could provide similar thermal management benefits in these alternative battery chemistries, enhancing their safety and efficiency. Redox flow batteries, for instance, could benefit from improved ion transfer rates and heat dissipation, making them more suitable for large-scale energy storage applications, such as grid storage.

The international research team continues to refine the manufacturing process, focusing on reducing the thickness of graphene films and enhancing their mechanical properties. These improvements could further optimize the performance of batteries and broaden the range of potential applications. Ongoing studies are investigating how graphene can be integrated into various battery components, including anodes and separators, to further enhance the overall efficiency and safety of energy storage systems.

Researchers are also exploring the environmental benefits of graphene-based batteries. Graphene’s durability and long lifespan could reduce the frequency of battery replacements, leading to lower overall waste and environmental impact. Additionally, advancements in sustainable graphene production methods, such as using biomass-derived carbon sources, are being pursued to make the material more environmentally friendly.

Source: nature.com

How graphene-based battery technology can help electric aircraft and eVTOLs ?

The application of graphene-based battery technology offers significant advantages for electric aircraft, including electric vertical take-off and landing (eVTOL) vehicles, which are poised to revolutionize urban mobility and aviation. Here’s how this technology specifically addresses the unique challenges faced by electric aircraft and eVTOLs:

1. Improved thermal management for enhanced safety and reliability

Electric aircraft and eVTOLs rely heavily on high-capacity lithium-ion batteries, which must handle large power loads during take-off, flight, and landing. This intense power demand generates considerable heat, which can compromise battery performance and safety. The integration of graphene-based current collectors, known for their exceptional thermal conductivity, significantly enhances heat dissipation within the battery. This ultrafast thermal dispersion reduces the risk of overheating, thereby preventing thermal runaway—a critical safety concern for airborne vehicles.

Example:
During high-stress flight phases, such as rapid ascents or prolonged hovering, eVTOLs can experience significant heat build-up in their batteries. Graphene’s ability to rapidly transfer heat away from critical components ensures that the batteries maintain optimal operating temperatures, enhancing the overall safety of the aircraft.

2. Increased energy density and longer flight times

Graphene-enhanced batteries allow for higher energy density without sacrificing safety, which is crucial for electric aircraft and eVTOLs. Higher energy density means that more energy can be stored within the same battery volume, allowing aircraft to fly longer distances or carry heavier payloads. This is especially important for eVTOLs, where space and weight constraints are critical design considerations.

Example:
For eVTOL manufacturers like Joby Aviation or Lilium, integrating graphene-based batteries could extend flight ranges, enabling these aircraft to perform longer trips without frequent recharging. This would greatly enhance the commercial viability of eVTOLs for urban air mobility, potentially connecting city centers to suburban areas more efficiently.

3. Enhanced power delivery for demanding flight conditions

Graphene’s superior electrical conductivity improves power delivery during peak performance periods, such as during take-offs, quick accelerations, or emergency maneuvers. This enhancement ensures that the battery can meet the high instantaneous power demands of electric aircraft without a significant drop in performance or increased heat generation.

Example:
In emergency scenarios where rapid climbs or evasive maneuvers are necessary, the graphene-enhanced batteries can provide the quick power bursts required, helping eVTOLs respond effectively to flight dynamics without compromising safety.

4. Increased battery lifespan and reduced maintenance

The improved thermal regulation provided by graphene reduces the wear and tear on battery cells caused by extreme temperature fluctuations. This not only extends the lifespan of the batteries but also reduces the frequency of maintenance and replacement cycles, a crucial factor for the economic viability of electric aircraft and eVTOLs.

Example:
Operators of eVTOL fleets, such as future air taxi services, would benefit from lower operational costs and increased vehicle availability due to fewer battery-related downtimes. This increased reliability is essential for commercial operations where consistent uptime is necessary.

5. Potential for lighter and more compact battery packs

Graphene’s ability to conduct both heat and electricity more efficiently than traditional materials allows for the design of lighter and more compact battery packs. This weight reduction can directly translate into increased payload capacity or improved overall flight efficiency, both of which are critical in the aviation sector.

Example:
For companies like Vertical Aerospace or Archer Aviation, the reduction in battery weight could mean higher passenger capacity or additional equipment on board, improving the versatility of their aircraft without compromising flight performance.

6. Future scalability and adaptability to new battery technologies

As the field of battery technology evolves, the graphene production process can be adapted for use with emerging battery chemistries, such as solid-state or sodium-ion batteries, which are being explored as alternatives to current lithium-ion technologies. These batteries promise higher energy densities and further safety improvements, making graphene a versatile material that can continue to benefit the future generations of electric aircraft.

Example:
With ongoing research into solid-state batteries, which eliminate the liquid electrolyte and further reduce the risk of thermal runaway, graphene-based current collectors could play a critical role in the development of ultra-safe, high-capacity batteries for next-generation electric aircraft.