Air-breathing lithium batteries eliminate range anxiety
Electric cars are one solution to Europe's air pollution problems, and they generally operate on Li-ion batteries. However, such batteries have a poor energy density, effectively meaning they hold relatively little power for their weight. Hence, alternative battery types are under consideration. Li-air technology is a potential alternative because of the excellent energy density. These batteries consist of a metal-based anode and air-cathode that constantly extract oxygen from the ambient air. Their advantage is that they have 10 times higher energy density than that of Li-ion batteries. Investigating this promising option was the aim of the project STABLE (Stable high-capacity lithium-air batteries with long cycle life for electric cars). One of the biggest challenges was to improve the life cycle of these batteries, which was 50 cycles maximum before STABLE. The project's objective was to increase charge cycles from 50 to 100-150 without losing capacity, which they successfully did, exceeding 150 cycles. To achieve these results, researchers conducted innovative research on battery anode, cathode, and electrolyte materials and technologies. They also investigated assembly techniques for batteries that play a central role in their performance, cost and environmental impact. The team found highly active bifunctional catalysts capable of effectively regenerating the battery and used suitable membranes to protect the Li anode from dendrite formation. It also increased electrolyte stability to enhance solubility of Li2O2 and avoid cathode clogging. In particular, researchers used silver and magnesium alloys of Li, in addition to protective layers on the anode to overcome the reactivity of Li. Carbon-based materials help to overcome the reversibility of the oxygen reduction reaction. Promising results with regard to conductivity were obtained with mesoporous carbons, carbon nanotubes, carbon fibres and graphene for use as cathode electrode materials. Researchers employed flame spray pyrolysis to synthesise several ceramic nanopowders that increased the cathode capacity. Nano-sized catalysts were produced on the porous cathode. The addition of ionic liquids in organic solvents significantly improved the electrolyte ionic conductivity. Metal oxide nanoparticles also reduced dendrite formation and improved oxygen solubility, viscosity and polarity of the electrolyte. STABLE made progress towards improving the lifespan of Li-air batteries. Such batteries can thus keep electric cars running longer on a single charge, increasing consumer confidence and the competitiveness of Europe's growing electric car market.
Keywords
Range anxiety, lithium-air, Li-air batteries, electric cars, energy density
