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- Lithium-Air Batteries
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Toward Standardized Performance Metrics
Toward Standardized Performance Metrics
A lithium–air battery is a rechargeable battery that uses oxygen from ambient air as the active material at the positive electrode and metallic lithium at the negative electrode. Because its theoretical energy density is several times higher than that of today’s lithium-ion batteries, it is often called the “ultimate rechargeable battery.” Thanks to their exceptionally high gravimetric energy density—meaning high capacity at low weight—lithium–air batteries are expected to find use across a wide range of applications where lightness matters, from drones and IoT devices to electric vehicles and home energy-storage systems. Research and development is therefore thriving worldwide. However, because the reaction mechanisms differ fundamentally from those of conventional lithium-ion batteries, evaluation methods and reporting conventions have not yet been unified, making it difficult to compare progress fairly. This column explains the principles of lithium–air batteries, how their performance should be evaluated, and the latest research trends.
Balancing Energy Density and Cycle Life—the Key to Better Rechargeable Batteries
In general, a rechargeable battery performs better when it can store more energy (high energy density) and withstand many charge–discharge cycles (long cycle life). Simply making a battery larger increases capacity, but it also adds volume and mass, which restricts where it can be used—and the extra weight increases the energy required to move or operate the system, reducing overall efficiency. For many practical applications, what is needed is a small, lightweight battery with high energy density. That is why lithium–air batteries—light yet high-capacity—have attracted so much attention. Why can they be made so light, and how far have we come in achieving both high capacity and long life?
