Zinc Air Batteries

1. Zinc Air Batteries By: Ana Brar

2. General Information Oxygen from air • Activated when oxygen is absorbed into the electrolyte through a membrane • Usually reaches full operating voltage within 5 seconds of being exposed to air • Oxygen diffused directly into battery • Electrolyte that catalytically promotes the reaction of oxygen, but is not depleted or transformed at discharge Zinc and alkaline electrolyte Button cell

3. Advantages • Weight - not necessary to carry a second reactant • High energy density • Competitive with Lithium-ion • Inexpensive materials • Flat discharge voltage • Safety - don't require volatile materials, so zinc-air batteries are not prone to catching fire like lithium-ion batteries • Excellent shelf life, with a self-discharge rate of only 2% per year • Available in a range of button and coin cell sizes • Rechargeable high powerfuelcellsin the process of development • Environmental benefits • Have high volumetric energy density compared to most primary batteries

4. Disadvantages • Sensitive to extreme temperature and humid conditions • Carbon dioxide from the air forms carbonate which reduces conductivity • High self discharge (after seal is broken) • After activation, chemicals tend to dry out and the batteries have to be used quickly • Although recharging is possible for fuel cells, it’s also inconvenient and is only suitable for high power types • Zinc air batteries must be larger to satisfy high current needs • High power batteries use mechanical charging in which discharged zinc cartridges are replaced by fresh zinc cartridges—therefore the used cartridges must be recycled • Have flooding potential • Limited output • When zinc turns it into zinc oxide it expands, space

5. Common uses • Hearing Aids • Watches • Mobile phones • Digital Cameras • Pagers • Power sources for electric fences • Recharging Li-Ion batteries • Transportation: • Cars - EVs • Buses

6. Rechargeability • Zn/Air Batteries – not rechargeable • Zn/Air Fuel Cells – rechargeable • ReVolt has developed rechargeable Zinc/Air batteries • In future: EVs using Zn/Air? • Zinc-air batteries can be made for high rate applications, which have a short life but high output • Or low rate, with low power but last a longer amount of time

7. Transportation • Would use Zn/Air Fuel Cells • Currently used in Las Vegas • Electrical Vehicle Division • Contain a central static replaceable anode cassette • To refuel: discharged zinc-air module removed from the vehicle and is "refueled" by exchanging spent "cassettes" with fresh cassettes Regeneration

8. Revolt • Swiss Company • Opened U.S. center of operations - Portland • Disadvantages: • They can't deliver sufficient power • They lose a lot of power very quickly • The cell dry out, becoming useless after only a few months • There is no satisfactory way to recharge them • The solution: • ReVolt's new technology has a theoretical potential of up to 4x the energy density of Li-Ion batteries at a comparable or lower production cost • Extended battery life due to stable reaction zone, low rates of dry-out and flooding, and no pressure build-up problems • Rechargeability • Compact size • Can manage the humidity within the cell

9. More on revolt • ReVolt technology claims to have overcome the main problem with zinc-air rechargeable batteries--that they typically stop working after relatively few charges (air electrode can become deactivated) • For electric vehicles: plan to use two flat electrodes – one containing zinc “slurry” • Air electrodes in the form of tubes • Zinc slurry is pumped through the tubes where it's oxidized, forming zinc oxide and releasing electrons

10. Revolt’s ev battery • Plan to increase energy density by increasing the amount of zinc slurry relative to the amount of material in the air electrode • Much like a fuel cell system or conventional engine – zinc slurry ~ fuel, pumping through the air electrode like gas in a combustion engine • Longer life span - from 2,000 to 10,000 cycles • As with fuel cells, may need to be paired with another type of battery for bursts of acceleration or regenerative braking

11. Zn/air vs. al/air • Al/Air: produces electricity from the reaction of oxygen in the air with aluminum • Has one of the highest energy densities of all batteries • Not widely used - cost, shelf-life, start-up time and byproduct removal, which have restricted their use to mainly military applications • An electric vehicle with aluminum batteries could have potentially ten to fifteen times the range of lead-acid batteries with a far smaller total weight

12. Mg/air Li/Air • High energy density • Safe • Inexpensive • Not been widely used - self-discharge in neutral solution • Reaction mechanism of magnesium alloy anode • Effects of different additives on performance of Mg alloy in solution • Approach energy density of fuel cells • PolyPlus • Single use and rechargeable lithium metal-air – could power Evs • Theoretically: max energy density 5,000+ watt-hours per kilogram • Lower self discharge rate and longer shelf life

13. conclusion • Many promising metal-air batteries: • Zinc/Air • Aluminum/Air • Magnesium/Air • Lithium/Air • Still mostly in developmental stages • Hope for use in electric vehicles in the future

14. References • http://news.cnet.com/8301-11128_3-10388553-54.html • http://www.technologyreview.com/energy/22926/ • http://www.treehugger.com/files/2009/10/zinc-air-battery-revolt-3-times-more-energy-lithium-ion-battery-electric-cars.php • http://www.mpoweruk.com/zinc_air.htm • http://news.cnet.com/8301-11128_3-10388553-54.html • http://www.duracell.com/oem/primary/Zinc/zinc_air_tech.asp • http://www.revolttechnology.com/technology/revolt-introduction.php • http://www.technologyreview.com/business/23812/page2/