ZINC AIR BATTERIES

By: Ana Brar

GENERAL INFORMATION 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

Oxygen from air

Zinc and alkaline electrolyte

Button cell

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 power fuel cells in the

process of development Environmental benefits Have high volumetric energy density compared

to most primary batteries

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

COMMON USES Hearing Aids Watches Mobile phones Digital Cameras Pagers Power sources for electric fences Recharging Li-Ion batteries Transportation:

Cars - EVsBuses

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

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

REVOLT Swiss Company Opened U.S. center of operations -

PortlandDisadvantages: • 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

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

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

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

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

CONCLUSION Many promising metal-air batteries:

Zinc/AirAluminum/AirMagnesium/AirLithium/Air

Still mostly in developmental stages Hope for use in electric vehicles in the

future

REFERENCES http://news.cnet.com/8301-11128_3-10388553-54.ht

ml http://www.technologyreview.com/energy/22926/ http://www.treehugger.com/files/2009/10/zinc-air-bat

tery-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.ht

ml

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/