What if we could make a battery out of two extremely common things, like salt and air?
Recent Developments in Lithium-Air (Li-Air) and Sodium-Air (Na-Air) Battery Technologies
Lithium-Air Batteries
- New Designs for Higher Energy Density: Researchers at the Illinois Institute of Technology and Argonne National Laboratory have developed a lithium-air battery utilizing a solid electrolyte instead of a liquid one. This design has achieved a four-electron reaction at room temperature, significantly improving energy density to approximately 1,200 Wh/kg—nearly four times that of conventional lithium-ion batteries. This solid electrolyte approach also addresses safety concerns associated with liquid electrolytes, which can pose overheating risks. The new battery design has successfully undergone 1,000 charge-discharge cycles, demonstrating enhanced stability and longevity compared to previous models.
- Challenges Persist: Despite these advancements, Li-air batteries still face challenges, including the instability of lithium peroxide (Li2O2) during discharge, which complicates the recharge process. The need for pure oxygen during operation remains a significant limitation, as it complicates practical applications.
Sodium-Air Batteries
- Rechargeability Breakthrough: A recent study led by researchers from Justus-Liebig-University Gießen has demonstrated that sodium-air batteries can be rechargeable, a significant improvement over traditional Li-air batteries. The study found that sodium reacts with oxygen to form sodium superoxide (NaO2), a more stable compound that allows for efficient cycling between discharge and charge. This process is less energy-intensive and avoids the decomposition issues faced by Li-air cells.
- Energy Density and Longevity: While Na-air batteries have a theoretical energy density of about 1,605 Wh/kg, which is lower than Li-air batteries, they offer advantages in terms of resource availability since sodium is more abundant than lithium. The researchers noted that although Na-air batteries can be recharged multiple times, their capacity diminishes after several cycles, with significant losses observed after eight cycles. Ongoing research aims to address these longevity issues.
- Low Overpotential Advantage: The Na-air battery design reported a low overpotential, which is three to four times lower than previously reported for both Li-air and Na-air batteries. This characteristic reduces energy losses during operation, making them more efficient overall.
Conclusion
The research into Li-air and Na-air batteries continues to evolve, with significant strides made in improving rechargeability and energy density. While Li-air batteries are pushing the boundaries of energy storage potential, Na-air batteries present a viable alternative with benefits in sustainability and cost-effectiveness. Both technologies have the potential to contribute significantly to future energy storage solutions, particularly in electric vehicles and other applications requiring high energy density.