Zinc-air battery

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Zinc-air battery

Zinc-air batteries (non-rechargeable), and zinc-air fuel cell
Fuel cell

A fuel cell is an Electrochemistry conversion device. It produces electricity from fuel and an Oxidizing agent , which react in the presence of an electrolyte....
s, (mechanically-rechargeable) are electro-chemical batteries

Battery (electricity)

In electronics, a battery or voltaic cell is a combination of one or more electrochemical cell Galvanic cells which store chemical energy that can be converted into electric potential energy, creating electricity....
powered by the oxidation of zinc

Zinc

Zinc is a metallic chemical element with the symbol Zn and atomic number 30. It is a first-row transition metal of the group 12 element of the periodic table....
with oxygen

Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
from the air. These batteries have high energy densities

Energy density

Energy density is the amount of energy stored in a given system or region of space per unit volume, or per unit mass, depending on the context, although the latter is more formally specific energy ....
and are relatively inexpensive to produce. They are used in hearing aid

Hearing aid

A hearing aid is an electroacoustic body worn apparatus which typically fits in or behind the wearer's ear, and is designed to amplify and Modulation sounds for the wearer....
s and in experimental electric vehicles

Battery electric vehicle

The battery electric vehicle, or BEV, is a type of electric vehicle that uses chemical energy stored in rechargeable battery battery pack....
. They may be an important part of a future zinc economy.

Particles of zinc are mixed with an electrolyte

Electrolyte

An electrolyte is any substance containing free ions that behaves as an electrical conductor medium. Because they generally consist of ions in solution, electrolytes are also known as ionic solutions, but molten electrolytes and solid electrolytes are also possible....
(usually potassium hydroxide

Potassium hydroxide

Potassium hydroxide is the inorganic compound with the formula potassiumhydroxide. Along with sodium hydroxide, this colourless solid is a prototypical "strong base"....
solution); water and oxygen from the air react at the cathode

Cathode

A cathode is an electrode through which electric charge flows out of a polarized electrical device. Mnemonic: CCD .From an electrochemical point of view, positively charged ion invariably move toward the cathode and/or negatively charged ion move away from it to balance the electrons arriving from external circuitry....
and form hydroxyl

Hydroxyl

Hydroxyl in chemistry stands for a molecule consisting of an oxygen atom and a hydrogen atom connected by a covalent bond. The neutral form is a hydroxyl Radical and the hydroxyl anion is called a hydroxide....
s which migrate into the zinc paste and form zincate (Zn(OH)₄^2-), at which point electron

Electron

The electron is a subatomic particle that carries a negative electric charge. It has elementary particle and is believed to be a point particle....
s are released and travel to the cathode.

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Is it possible to power a car with this cell?

Encyclopedia

Battery (electricity)

Zinc

Zinc is a metallic chemical element with the symbol Zn and atomic number 30. It is a first-row transition metal of the group 12 element of the periodic table....
with oxygen

Oxygen

Energy density

Hearing aid

Battery electric vehicle

Electrolyte

Potassium hydroxide

Cathode

Hydroxyl

Electron

The electron is a subatomic particle that carries a negative electric charge. It has elementary particle and is believed to be a point particle....
s are released and travel to the cathode. The zincate decays into zinc oxide

Zinc oxide

Zinc oxide is an inorganic compound with the Chemical formula ZnO. It usually appears as a white powder, nearly insoluble in water. The powder is widely used as an additive into numerous materials and products including plastics, ceramics, glass, cement, rubber , lubricants, paints, ointments, adhesives, sealants, pigments, foods , batteries,...
and water is released back into the system. The water and hydroxyls from the anode

Anode

An anode is an electrode through which electric charge flows into a polarized electrical device. Mnemonic: ACID . Electrons flow in the opposite direction to the positive electric current....
are recycled at the cathode, so the water serves only as a catalyst. The reactions produce a maximum voltage

Voltage

Electrical tension is the potential difference between two points of an electrical or electronic circuit, expressed in volts. It is the measurement of the potential for an electric field to cause an electric current in an electrical conductor....
level of 1.65 volts, but this is reduced to 1.4–1.35 V by reducing air flow into the cell; this is usually done for hearing aid batteries to reduce the rate of water drying out.

The term zinc-air fuel cell usually refers to a zinc-air battery in which zinc fuel is replenished and zinc oxide waste is removed continuously. This is accomplished by pushing zinc electrolyte paste or pellets into an anode chamber. Waste zinc oxide is pumped into a waste tank or bladder inside the fuel tank, and fresh zinc paste or pellets are taken from the fuel tank. The zinc oxide waste is pumped out at a refuelling station and sent to a recycling plant. Alternatively, this term may refer to an electro-chemical system in which zinc is used as a co-reactant to assist the reformation of hydrocarbon

Hydrocarbon

In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. With relation to chemical terminology, aromatic hydrocarbons or arenes, alkanes, alkenes and alkyne-based compounds composed entirely of carbon or hydrogen are referred to as "pure" hydrocarbons, whereas other hydrocarbons with bonded com...
fuels on an anode of a fuel cell.

Zinc-air batteries have properties of fuel cells as well as batteries: the zinc is the fuel, the rate of the reaction can be controlled by controlling the air flow, and used zinc/electrolyte paste can be removed from the cell and replaced with fresh paste. Research is being conducted in powering electric vehicles with zinc-air batteries.

Reaction formulas

Here are the chemical equation

Chemical equation

A chemical equation may be described as a chemical reaction or a means of writing out and describing such a phenomenon. The coefficients next to the symbols and formulae of entities are the absolute values of the stoichiometric coefficient....
s for the zinc-air cell:

Anode: Zn + 4OH^– ? Zn(OH)₄^2– + 2e^– (E₀ = –1.25 V)

Fluid: Zn(OH)₄^2– ? ZnO + H₂O + 2OH^–

Cathode: O₂ + 2H₂O + 4e^– ? 4OH^– (E₀ = 0.4 V)

Overall: 2Zn + O₂ ? 2ZnO (E₀ = 1.65 V)

Alternatively the reaction is stated without use of zincate, but this is inaccurate:

Anode: Zn + 2OH^– ? Zn(OH)₂ + 2e^– (E₀ = –1.25 V)

Cathode: O₂ + 2H₂O + 4e^– ? 4OH^– (E₀ = 0.4 V)

Overall: 2Zn + O₂ + 2H₂O ? 2Zn(OH)₂ (E₀ = 1.65 V)

Properties

High specific energy
Specific energy

Specific energy is defined as the energy per unit mass: J/kg or, in basic SI units: m2/s2. It is an intensive property. Contrast this with energy, which is an extensive property....
: up to 370 W·h
Watt-hour

The kilowatt hour, also written kilowatt-hour, is a unit of energy.Energy delivered by electric utilities is usually expressed and charged for in kWh....
/kg
Kilogram

The kilogram or kilogrammeThe spelling kilogram is used by the International Committee for Weights and Measures and the U.S....
.
Terminal voltage does not drop until 80–85% depletion.
Very long shelf lives when sealed to exclude oxygen.
A very high self-discharge
Self-discharge

Self-discharge is a phenomenon in Battery in which internal chemical reactions reduce the stored charge of the battery without any connection between the electrodes....
rate when exposed to air due to spontaneous
Spontaneous process

A spontaneous process is the time-evolution of a system in which it releases Gibbs free energy and moves to a lower, more thermodynamically stable, energy state....
zinc oxidation.

The battery must be resealed when not in use. The electrolyte can be maintained in a humidified
Humidity

Humidity is the amount of water vapor in the air. In daily language the term "humidity" is normally taken to mean relative humidity. Relative humidity is defined as the ratio of the partial pressure of water vapor in a Air parcel of air to the saturated vapor pressure of water vapor at a prescribed temperature....
environment.
Must not be over saturated or immersed in water.

Zinc is cheap; mass production is inexpensive.
Not electrically rechargeable, but recycling can reduce the zinc oxide back to zinc metal for use in new batteries.

Zinc as energy currency

Metallic zinc could be used as an alternative to hydrogen as an energy transfer medium (a fuel

Fuel

Fuel is any material that is burned or altered in order to obtain energy and to heat or to move an object. Fuel releases its energy either through a chemical reaction means, such as combustion, or nuclear means, such as nuclear fission or nuclear fusion....
). The zinc would be either used in a zinc-air battery

Zinc-air battery

Zinc-air batteries , and zinc-air fuel cells, are Battery powered by the oxidation of zinc with oxygen from the air. These batteries have high energy density and are relatively inexpensive to produce....
or used to generate hydrogen by electrolysis

Electrolysis

In chemistry and manufacturing, electrolysis is a method of separating Chemical bond chemical compound by passing an electric current through them....
near the point of use.

A major disadvantage is that zinc is a solid, and cannot be handled and pumped with the convenience of a liquid. A possible alternative is to form pellets of a size to be pumped. Fuel cells using it would have to empty the "spent" zinc and be refueled quickly. The spent zinc-oxide would be reduced at a local facility into zinc. The zinc-air "battery" cell is considered a primary cell

Primary cell

A primary cell is any kind of electrochemical cell in which the electrochemistry chemical reaction of interest is not reversible, so used in disposable battery ....
and is non-rechargeable; recycling is required to reclaim the zinc oxide.

Hydrogen generated from zinc and water could be burned in conventional internal combustion engines, although this would provide a far less powerful engine than a hydrocarbon-powered engine; a better alternative would be the use of high efficiency electric motors to exploit the power produced by a zinc-air battery and drive the vehicle.

Zinc has a number of advantages over hydrogen as an energy-carrier. Zinc-air cell batteries are already efficient enough for practical use in vehicles. Pure Zinc is non-toxic (although commercially available zinc may often be contaminated by toxic metals such as lead

Lead

Lead is a main-group Chemical element with symbol Pb and atomic number 82. Lead is a soft, malleable poor metal, also considered to be one of the heavy metal ....
) and substantially easier to store than hydrogen, and can be processed by water-based electrochemistry. The has dropped to just over $1000 per metric ton at the end of 2008 .

External links

(includes half-cell reactions)
developing RECHARGEABLE Zinc-air batteries
Zinc-air batteries for cameras

Zinc-air battery

Reaction formulas

Properties

Zinc as energy currency

See also

External links