Nickel-iron battery
Encyclopedia
The nickel–iron battery (NiFe battery) is a storage battery having a nickel(III) oxide-hydroxide cathode
Cathode
A cathode is an electrode through which electric current flows out of a polarized electrical device. Mnemonic: CCD .Cathode polarity is not always negative...

 and an iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 anode
Anode
An anode is an electrode through which electric current flows into a polarized electrical device. Mnemonic: ACID ....

, with an electrolyte
Electrolyte
In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....

 of potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...

. The active materials are held in nickel-plated steel tubes or perforated pockets. It is a very robust battery which is tolerant of abuse, (overcharge, overdischarge, and short-circuiting) and can have very long life even if so treated. It is often used in backup situations where it can be continuously charged and can last for more than 20 years. Due to its low specific energy, poor charge retention, and its high cost of manufacture, other types of rechargeable batteries have displaced the nickel–iron battery in most applications.

They are currently gaining popularity for off-the-grid
Off-the-grid
The term off-the-grid or off-grid refers to living in a self-sufficient manner without reliance on one or more public utilities....

 applications where daily charging makes them an appropriate technology
Appropriate technology
Appropriate technology is an ideological movement originally articulated as "intermediate technology" by the economist Dr...

.

Durability

The ability of these batteries to survive frequent cycling is due to the low solubility of the reactants in the electrolyte. The formation of metallic iron during charge is slow because of the low solubility of the ferrous hydroxide. While the slow formation of iron crystals preserves the electrodes, it also limits the high rate performance: these cells charge slowly, and are only able to discharge slowly. Nickel–iron cells should not be charged from a constant voltage supply since they can be damaged by thermal runaway
Thermal runaway
Thermal runaway refers to a situation where an increase in temperature changes the conditions in a way that causes a further increase in temperature, often leading to a destructive result...

; the cell internal voltage drops as gassing begins, raising temperature, which increases current drawn and so further increases gassing and temperature.

Nickel-iron batteries have long been used in European mining operations because of their ability to withstand vibrations, high temperatures and other physical stress. They are being examined again for use in wind and solar power systems and for modern electric vehicles, especially boats, where the weight of the batteries is not an issue.

Electrochemistry

The half-cell reaction at the cathode:
2 NiOOH + 2 H2O + 2 e ↔ 2 Ni(OH)2 + 2 OH


and at the anode:
Fe + 2 OH ↔ Fe(OH)2 + 2 e


(Discharging is read left to right, charging is from right to left.)

The open-circuit voltage is 1.4 volts, dropping to 1.2 volts during discharge. The electrolyte mixture of potassium hydroxide and lithium hydroxide is not consumed in charging or discharging, so unlike a lead-acid battery the electrolyte specific gravity does not indicate state of charge. Lithium hydroxide improves the performance of the cell. the voltage required to charge the cells is between 1.45 and 1.65 volts. The equalization charge voltage is 1.65 volts.

History

Swedish inventor Waldemar Jungner
Waldemar Jungner
Ernst Waldemar Jungner, June 19, 1869- August 30, 1924, was a Swedish inventor and engineer. In 1899 he invented the nickel-iron electric storage battery and invented the nickel-cadmium battery.-Literature:...

 had invented the nickel–cadmium battery in 1899. Jungner experimented with substituting iron for the cadmium in varying proportions, including 100% iron. Jungner had already discovered that the main advantage over the nickel–cadmium chemistry was cost, but due to the lower efficiency of the charging reaction and more pronounced formation of hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 (gassing), the nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...

iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 technology was found wanting and abandoned. Jungner had several patents for the iron version of his battery (Swedish pat.Nos 8.558/1897, 10.177/1899, 11.132/1899, 11.487/1899 and German Patent No.110.210 /1899. Moreover he had one patent for NiCd battery: Swed.pat No. 15.567/1899.
The battery was developed by Thomas Edison
Thomas Edison
Thomas Alva Edison was an American inventor and businessman. He developed many devices that greatly influenced life around the world, including the phonograph, the motion picture camera, and a long-lasting, practical electric light bulb. In addition, he created the world’s first industrial...

 in 1901, and used as the energy source for electric vehicle
Electric vehicle
An electric vehicle , also referred to as an electric drive vehicle, uses one or more electric motors or traction motors for propulsion...

s, such as the Detroit Electric
Detroit Electric
Detroit Electric was an automobile brand produced by the Anderson Electric Car Company in Detroit, Michigan. Nowadays, a Chinese British entrepreneur is leading Detroit Electric to develop affordable and high quality pure electric vehicles in mainland Europe...

 and Baker Electric. Edison claimed the nickel–iron design to be, "far superior to batteries using lead plates and acid" (lead–acid battery). Edison had also several patents: US.Pat No.678.722/1901, 692.507/1902 and German patent No 157.290/1901.

Jungner's work was largely unknown in the US until the 1940s, when nickel-cadmium batteries went into production there. A 50 volt nickel–iron battery was the main power supply in the World War II German V2 rocket (together with two 16 volt accumulators which powered the four gyroscope
Gyroscope
A gyroscope is a device for measuring or maintaining orientation, based on the principles of angular momentum. In essence, a mechanical gyroscope is a spinning wheel or disk whose axle is free to take any orientation...

s), with a smaller version used in the V1 flying bomb. (viz. 1946 Operation Backfire blueprints.)

Manufacture

Edison's batteries were made from about 1903 to 1972 by the Edison Storage Battery Company
Edison Storage Battery Company
The Edison Storage Battery Company was organized in New Jersey on May 27, 1901, to develop, manufacture, and sell Thomas Edison's alkaline storage battery. It produced batteries for mining lamps, train lighting and signaling, submarines, electric vehicles, and other uses...

 in East Orange, NJ. They were quite profitable for the company. In 1972 the battery company was sold to the Exide Battery Corporation, which discontinued making the battery in 1975.

Edison was disappointed that his battery was not adopted for starting internal combustion engines and that electric vehicles went out of production only a few years after his battery was introduced. He actually developed the battery to be the battery of choice for electric vehicle
Electric vehicle
An electric vehicle , also referred to as an electric drive vehicle, uses one or more electric motors or traction motors for propulsion...

s which were the preferred transportation mode in the early 1900s (followed by gasoline and steam). Edison's batteries had a significantly higher energy density
Energy density
Energy density is a term used for the amount of energy stored in a given system or region of space per unit volume. Often only the useful or extractable energy is quantified, which is to say that chemically inaccessible energy such as rest mass energy is ignored...

 than the lead–acid batteries in use at the time, and could be charged in half the time, however they performed poorly at low ambient temperatures and were more expensive. The battery enjoyed wide use for railroad signaling, fork lift, and standby power
Standby power
Standby power, also called vampire power, vampire draw, phantom load, or leaking electricity , refers to the electric power consumed by electronic and electrical appliances while they are switched off Standby power, also called vampire power, vampire draw, phantom load, or leaking electricity...

applications.

Nickel–iron cells were made with capacities from 5 to 1250 Ah. Many of the original manufacturers no longer make nickel iron cells. Currently they are being manufactured in China and Russia as well as in the US.

Environmental impact

Nickel–iron batteries do not have the lead or cadmium of the lead–acid and nickel–cadmium batteries, which makes them a lesser burden on human and ecological health.

External links

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