A nickel–zinc battery, abbreviated NiZn, is a type of

rechargeable battery A rechargeable battery, storage battery, or secondary cell (formally a type of Accumulator (energy), energy accumulator), is a type of electrical battery which can be charged, discharged into a load, and recharged many times, as opposed to ...

similar to NiCd batteries, but with a higher voltage of 1.6 V. Larger

nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...

–

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...

battery systems have been known for over 100 years. Since 2000, development of a stabilized zinc

electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials de ...

system has made this technology viable and competitive with other commercially available rechargeable battery systems. Unlike some other technologies,

trickle charging Trickle charging means charging a fully charged battery at a rate equal to its self-discharge rate, thus enabling the battery to remain at its fully charged level; this state occurs almost exclusively when the battery is not loaded, as trickle char ...

is not recommended.

History

In 1901

Thomas Alva Edison Thomas Alva Edison (February 11, 1847October 18, 1931) was an American inventor and businessman. He developed many devices in fields such as electric power generation, mass communication, sound recording, and motion pictures. These invention ...

was awarded for a rechargeable nickel–zinc battery system. "Building A Better Battery", Kerry A. Dolan, Forbes.com, ''

Forbes ''Forbes'' () is an American business magazine owned by Integrated Whale Media Investments and the Forbes family. Published eight times a year, it features articles on finance, industry, investing, and marketing topics. ''Forbes'' also re ...

'' magazine, 11 May 2009, Retrieved 2011-02-12,
Forbes-44
The battery was later developed by the Irish chemist Dr. James J. Drumm (1897–1974), and installed in four two-car Drumm railcar sets between 1932 and 1949 for use on the Dublin–Bray railway line. Although successful, they were withdrawn when the batteries wore out. Early nickel–zinc batteries provided only a small number of discharge/recharge cycles. In the 1960s nickel–zinc batteries were investigated as an alternative to silver–zinc batteries for military applications, and in the 1970s were again of interest for electric vehicles. ''Evercel Inc.'' developed and patented several improvements in nickel–zinc batteries, but withdrew from that area in 2004.

Applications

Nickel–zinc batteries have a charge/discharge curve similar to 1.2 V NiCd or

NiMH NIMH may refer to: *Nickel–metal hydride battery (NiMH), a type of electrical battery *National Institute of Mental Health, an agency of the United States government *National Institute of Medical Herbalists, a professional organisation in the Un ...

cells, but with a higher 1.6 V nominal voltage. Nickel–zinc batteries perform well in high-drain applications, and may have the potential to replace lead–acid batteries because of their higher energy-to-mass ratio and higher power-to-mass ratio — as little as 25% of the mass for the same power. NiZn are cheaper than nickel-cadmium batteries, and are expected to be priced somewhere between NiCd and lead–acid types. NiZn may be used as a substitute for nickel–cadmium. The European Parliament has supported bans on cadmium-based batteries; nickel–zinc is a good alternative for power tools and other applications. A disadvantage is increased self-discharge rate after about 30-50 cycles, so that batteries do not hold their charge as long as when new. Where this is not a problem NiZn is a good battery choice for applications requiring high-power and high-voltage.

Battery life

Compared with cadmium hydroxide, the tendency of the soluble zinc hydroxide ion (

zincate In chemistry the term zincate may refer to several substances containing the element zinc: * usually the anion ZnO22−, more properly called tetrahydroxozincate or salts thereof, such as sodium zincate . * the polymeric anion n(OH)3−and its s ...

) to dissolve into solution and not fully migrate back to the cathode during recharging has, in the past, presented challenges for the commercial viability of the NiZn battery.David Linden (ed)., ''Handbook of Batteries'', McGraw Hill, 2002, , chapter 31. Another common issue with zinc rechargeable batteries is electrode shape change and

dendrites Dendrites (from Greek δένδρον ''déndron'', "tree"), also dendrons, are branched protoplasmic extensions of a nerve cell that propagate the electrochemical stimulation received from other neural cells to the cell body, or soma, of the n ...

(or "

whiskers Vibrissae (; singular: vibrissa; ), more generally called Whiskers, are a type of stiff, functional hair used by mammals to touch, sense their environment. These hairs are finely specialised for this purpose, whereas other types of hair are c ...

"), which may reduce the cell discharging performance or, eventually, short out the cell, resulting in a low cycle life. Recent advances have enabled this problem to be greatly reduced. These advances include improvements in electrode separator materials, inclusion of zinc material stabilizers, and electrolyte improvements (e.g. by using

phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phospho ...

s). PowerGenix has developed 1.6 V batteries with claimed battery cycle life comparable to NiCd batteries. Battery cycle life is most commonly specified at a discharge depth of 80 percent of rated capacity and assuming a one-hour discharge current rate. As the discharge current or the depth of discharge is reduced, the number of charge-discharge cycles for a battery increases. When comparing NiZn to other battery technologies, cycle life comparisons may vary depending on the discharge rate and depth of discharge used.

Advantages

Nickel–zinc cells have an open circuit voltage of 1.85 volts when fully charged, and a nominal voltage of 1.65 V. This makes NiZn an excellent replacement for electronic products designed to use 1.5 V alkaline primary cells. Equipment designed for alkaline batteries will not operate properly below an endpoint voltage based on 1.5 V when fresh; NiCd and NiMH both have nominal cell voltages of 1.2 V, and will reach this endpoint before their charge capacity is fully depleted. Newer cells which are more powerful and with a life of up to 800 cycles can be an alternative to Li-ion batteries for electric vehicles. Due to the higher cell voltage, fewer cells are required for a given pack voltage than for NiCd and NiMH. They also have low internal impedance (typically 5 milliohms), which allows for high battery discharge rates, up to 50''C''. (''C'' is battery capacity in Ah, divided by one hour.) NiZn batteries do not use mercury, lead, or cadmium, or

metal hydride In chemistry, a hydride is formally the anion of hydrogen( H−). The term is applied loosely. At one extreme, all compounds containing covalently bound H atoms are called hydrides: water (H2O) is a hydride of oxygen, ammonia is a hydride of ...

s, all of which can be difficult to recycle. Both nickel and zinc are commonly occurring elements in nature, and can be fully recycled. NiZn cells use no flammable active materials or organic electrolytes, and the newest models use polymeric separators which reduce the dendrites problem. Properly designed NiZn cells can have very high power density and low-temperature discharging performance, and also can be discharged to almost 100%, and recharged without problems. they were available in sizes up to F, and 50Ah/ prismatic cell. Zinc is a cheap and abundant metal, the 24th most abundant element in the Earth's crust, and is not dangerous to health. Common oxidation is +2, so charge and discharge move two electrons instead of one as in NiMH batteries.

Charging

Chargers for NiZn batteries must be capable of charging a battery with a fully charged voltage of 1.85 V per cell, higher than the 1.4 V of NiMH. NiZn technology is well suited for fast recharge cycling, as optimum charge rates of C or C/2 are preferred. Known charging regimes include a constant current of C or C/2 to cell voltage = 1.9 V. One manufacturer recommends charging at a constant current of C/4 to C until cell voltage reaches 1.9V, then continuing to charge at a constant voltage of 1.9V until charge current declines to C/40. Maximum charge time is given variously as hours and 3 hours. Once charged, continuous trickle charging is not recommended, as recombination is not provided for, and excess

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

will eventually vent, adversely affecting battery cycle life. A typical charger for NiZn batteries specifically does not trickle charge after the battery is fully charged, but shuts off.

Chemistry

:(−) electrode: Zn + 4 OH⁻ Zn(OH)₄²⁻ + 2e⁻ (E⁰ = −1.2 V/SHE ) :Electrolyte: KOH ::Zn(OH)₄²⁻ Zn(OH)₂ + 2OH⁻ ::Zn(OH)₂ ZnO + H₂O :(+) electrode: 2 NiO(OH) + 2 H₂O + 2 e⁻ 2 Ni(OH)₂ + 2 OH⁻ (E⁰ = +0.50 V/SHE) :Overall reaction: Zn + 2 NiO(OH) + H₂O ZnO + 2 Ni(OH)₂ :Parasitic reaction: Zn + 2 H₂O → Zn(OH)₂ + H₂

References

{{DEFAULTSORT:Nickel-zinc battery Nickel Rechargeable batteries Zinc