About Nickel-zinc battery
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PowerGenix NiZn AA cells with charger |
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| Energy/weight | 100 W·h/kg |
|---|---|
| Energy/size | 280 W·h/L |
| Power/weight | > 900 W/kg |
| Energy/consumer-price | 2-3Wh/US$ |
| Cycle durability | 400-1000[1] |
| Nominal Cell Voltage | 1.6 V |
The nickel-zinc battery (sometimes abbreviated NiZn) is a type of rechargeable battery commonly used in cordless power tools, cordless telephone, digital cameras, battery operated lawn and garden tools, professional photography, electric bike and light electric vehicle sectors.
While nickel-zinc battery systems have been around for over 100 years, recent technological breakthroughs have made this technology viable and competitive with other commercially available rechargeable battery systems.
Contents |
History
Developed by an Irish chemist, Dr. James J. Drumm (1897-1974)[2] and installed in four 2-car Drumm Railcar sets between 1932 and 1948 for use on the Dublin-Bray line. Although successful they were then withdrawn when the batteries wore out. Early nickel-zinc batteries were plagued by limited number of discharge cycles.
Thomas Edison was awarded a U.S. Patent for a recharged Nickel Zinc battery system in 1901 (U.S. Patent 684, 204).
Applications
Nickel Zinc batteries have an open circuit voltage of 1.6 volts. This makes NiZn an ideal replacement battery for electronic products that were designed to use alkaline primary batteries (1.5V). Because NiZn rechargeable batteries have a high open circuit voltage that closely approximates the open circuit voltage of alkaline primary cells it makes these batteries best suited for substitution into these electronic devices. Because NiCd and NiMH both have open circuit voltages of 1.2v they are often not ideal for electronic equipment designed for alkaline primary cells. Due to the low voltage of both NiCd and NiMH it is often the case that the electronic equipment will shut off prior to a complete discharge of the battery because a minimal operating voltage is not provided. Li Ion batteries have a much higher open circuit voltage and are not suitable replacement batteries for alkaline primary batteries (1.5v); however having resistors in the AA shell with Li-ion batteries may help approximate the cell voltage.
Presently this battery technology has limited consumer availability with only AA cells offered for the digital camera market in some camera stores (Ritz Camera). Both D-cell and sub-C cells are currently used by commercial applications.
Nickel-zinc is promoted as the next generation batteries for 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 (up to 75% lighter for the same power), and are cheap compared to nickel-cadmium batteries (expected to be priced somewhere in between NiCd and lead-acids). NiZn may be used as an industrial substitute for nickel-cadmium. The European Parliament has supported bans on cadmium based batteries and nickel-zinc offers the European power tool industry a potential alternative.
Electrochemistry
Charge Reaction: 2Ni(OH)2(s) + Zn(OH)2(s) ↔ 2Ni(OH)3(s) + Zn(s)
Note that the stoichiometry above is different than below, but the reactions are identical. Technically, water is consumed and generated on the charge and discharge cycles.
Discharge Reaction: H2O + Zn + 2NiOOH ↔ ZnO +2Ni(OH)2
Electrochemical open circuit voltage potential: ~1.73V
Battery Life
The affinity for the zinc electrode to dissolve into solution and not fully migrate back to the cathode has, in the past, presented challenges to the commercial viability of the NiZn battery. The zinc's reluctance to fully return to the solid electrode adversely manifest itself and resulted in limited battery recharge cycles.
Recent technological steps have allowed PowerGenix to patent a commercially viable battery system. These technology breakthroughs include: improved electrode separators materials, zinc material stabilizers, and electrolyte improvements. The resulting PowerGenix NiZn battery has realized battery cycle life comparable to both NiCd and NiMH battery systems.
Battery cycle life is most commonly specified at a discharge rate of 80 percent of rated capacity and assuming a one hour discharge current rate. If the discharge current rate is reduced or if the depth of discharge is reduced then the number of charge/discharge cyles for a battery increases.
When comparing NiZn to other battery technologies it is important to note that cycle life specifications may vary with other battery technologies depending on the discharge rate and depth of discharge that were used.
Technological Advantage
Higher performances than other alkaline batteries.
No use of heavy/toxic metals (mercury, lead or cadmium).
No use of metal hydrides (rare earth metals) that are difficult to recycle.
No flammable active material or organic electrolyte.
Low internal impedance (typ. 5 milliohm) provides for high battery discharge rates capability.
Simple recycling process, similar to the one in use for primary alkaline batteries. Zinc and nickel can be fully recycled.
1.6V cell voltage vs. 1.2V for NiCd and NiMH rechargeable cells.
Fewer cells required (compared to NiCd and NiMH)to achieve battery pack voltage reducing pack weight, size and improving pack reliability.
Both nickel and zinc are commonly occurring elements in nature and are not hazardous.
Nickel-zinc batteries when used with aqueous electrolytes may provide a "green" battery.
Charging
NiZn technology is well suited for fast recharge cycling as optimum charge rates of C or C/2 are preferred.
Known charging regimes include constant current of C or C/2 to cell voltage = 1.9V. Maximum charge time of 2 1/2 hours. Trickle charging is not recommended as recombination is not provided for and excess hydrogen will eventually vent adversely affecting battery cycle life. Charge is reinitiated after cell voltage has decayed below 1.6V.
Nickel Zinc Manufacturing
Evercel (Hingham, MA): ceased NiZn operations in 2004 which included it wholly owned subsidiary Xiamen Evercel Battery Co. in China. Evercel produced a flooded rechargeable prismatic large format battery. Evercel issued an exclusive, worldwide license for its rechargeable nickel-zinc battery technology to CM Partner of Kyungkido, Korea in 2006.
Xellerion, Inc./eVionyx, Inc. (Hawthorne, NY): large format rechargeable prismatic battery.
PowerGenix (San Diego, CA): cylindrical rechargeable battery cells.
Optimum Battery CO. (Shenzhen China): cylindrical rechargeable battery cells.
Toshiba Battery Co. (Tokyo Japan): Giga Energy, cylindrical primary cells.
References
- ^ PowerGenix
- ^ Famous Irish Chemists: James J. Drumm
External links
- Powergenix - Developer and Manufacturer of nickel zinc batteries
- [1] - SCPS - Developer of industrial NiZn batteries
- [2] - Branch of Evionyx who has all infos on NiZn battery
- eVionyx - Developer and manufacturer of "flooded" prismatic NiZN battery
- eVionyx Taiwan - Taiwan manufacturer of eVionyx products
2009,10,15
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