By Dave Brown — Exclusive to Lithium Investing NewsThe International Journal of Smart and Nano Materials recently published a review by the Changchun Institute of Applied Chemistry that outlines the progress and remaining chemistry challenges of lithium-air battery technology.
While lithium-air batteries have received attention as possible batteries for electric vehicle applications, the technology is still in its infancy. There are a number of scientific and technical challenges that must be overcome if the engaging promise of the technology is to be realized in electric vehicle adoption. Competitive advantage The major appeal of lithium-air batteries is that they use oxygen from the air instead of storing an oxidizer internally, and as a result have extremely high-energy density. The research team suggests that the energy density of the lithium-air battery with respect to the anode could reach 13,000 watt hours per kilogram, which is comparatively close to the 13,200 watt hours per kilogram of gasoline. A United States IBM team has also demonstrated high-energy density with lithium-air chemistry. The Battery 500 coalition features an IBM-led team that includes commercial partners and four US national laboratories. The team hopes to have a full-scale prototype ready by 2013, with commercial batteries to follow within this decade. Types of lithium-air battery chemistry There are four basic chemical configurations of lithium-air batteries. Three versions of lithium-air batteries use liquid electrolytes, which include a fully aprotic liquid electrolyte, an aqueous electrolyte, and a mixed system with an aqueous electrolyte immersing the cathode and an aprotic electrolyte immersing the anode. The fourth approach is an all-solid-state battery with a solid electrolyte. The Chinese team is concerned primarily with the first architecture for lithium-air batteries, as it shows the most promise of rechargeability, and has attracted the most effort worldwide.
Key areas for future researchFrom the perspective of the authors, five areas are important for future research.
- Understanding the complex chemical reaction mechanisms that occur during charge and discharge underscores any future progress.
- A porous carbon-based oxygen cathode is expected to be critical for performance improvement of lithium-air battery technology. The electrons are confined inside the electrode material while the oxygen is in both the gaseous and solution phases and the lithium ions are contained in the electrolyte solution.
- High “round-trip efficiency” is optimized by screening bifunctional cathode catalysts with improved activity for both an oxygen reduction reaction during the discharge period and an oxygen evolution reaction during the charge period.
- Attributes for development of stable electrolytes include excellent lithium ionic conductivity, high oxygen solubility, low viscosity, and vapor pressure. Properties of the electrolyte such as ionic conductivity, oxygen solubility, viscosity, and contact angle strongly influence the cell discharge performance.
- Developing a high lithium ionic conducting separator and a high throughout oxygen-breathing membranes used at the cathode to block H2O, CO2 and other air components except O2