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Nickel–metal hydride battery
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Nickel–metal hydride battery
A nickel–metal hydride battery (NiMH or Ni–MH) is a type of rechargeable battery. The chemical reaction at the positive electrode is similar to that of the older nickel–cadmium cell (NiCd), with both using nickel oxide hydroxide, NiO(OH). However, the negative electrodes use a hydrogen-absorbing alloy instead of cadmium. NiMH batteries typically have two to three times the capacity of NiCd batteries of the same size, with significantly higher energy density, although only about half that of lithium-ion batteries. NiMH batteries have almost entirely replaced NiCd.
These batteries are typically used as a substitute for similarly shaped non-rechargeable alkaline and other primary batteries. They provide a cell voltage of about 1.2V while fresh alkaline cells provide 1.5V; however devices designed for alkaline batteries operate until cell voltage gradually drops to around 1.0V, while the voltage of a fully-charged NiMH cell drops more slowly, giving good endurance for a 1.0V end point. NiMH batteries are less prone to leaking corrosive electrolyte than primary batteries.
Work on NiMH batteries began at the Battelle-Geneva Research Center following the technology's invention in 1967. It was based on sintered Ti2Ni+TiNi+x alloys and NiOOH electrodes. Development was sponsored over nearly two decades by Daimler-Benz and by Volkswagen AG within Deutsche Automobilgesellschaft, now a subsidiary of Daimler AG. The batteries' specific energy reached 50 W·h/kg (180 kJ/kg), specific power up to 1000 W/kg and a life of 500 charge cycles (at 100% depth of discharge). Patent applications were filed in European countries (priority: Switzerland), the United States, and Japan. The patents transferred to Daimler-Benz.
Interest grew in the 1970s with the commercialisation of the nickel–hydrogen battery for satellite applications. Hydride technology promised an alternative, less bulky way to store the hydrogen. Research carried out by Philips Laboratories and France's CNRS developed new high-energy hybrid alloys incorporating rare-earth metals for the negative electrode. However, these suffered from alloy instability in alkaline electrolyte and consequently insufficient cycle life. In 1987, Willems and Buschow demonstrated a successful battery based on this approach (using a mixture of La0.8Nd0.2Ni2.5Co2.4Si0.1), which kept 84% of its charge capacity after 4000 charge-discharge cycles. More economically viable alloys using mischmetal instead of lanthanum were soon developed. Modern NiMH cells were based on this design. The first consumer-grade NiMH cells became commercially available in 1989.
In 1998, Stanford Ovshinsky at Ovonic Battery Co., which had been working on MH-NiOOH batteries since mid-1980, improved the Ti–Ni alloy structure and composition and patented its innovations.
In 2008, more than two million hybrid cars worldwide were manufactured with NiMH batteries.
In the European Union due to its Battery Directive, nickel–metal hydride batteries replaced Ni–Cd batteries for portable consumer use.
In Switzerland in 2009, approximately 60% of portable rechargeable batteries were NiMH. In 2000, almost half of all portable rechargeable batteries sold in Japan were NiMH, compared to 22% in 2010. This percentage has fallen over time due to the increase in manufacture of lithium-ion batteries.
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Nickel–metal hydride battery
A nickel–metal hydride battery (NiMH or Ni–MH) is a type of rechargeable battery. The chemical reaction at the positive electrode is similar to that of the older nickel–cadmium cell (NiCd), with both using nickel oxide hydroxide, NiO(OH). However, the negative electrodes use a hydrogen-absorbing alloy instead of cadmium. NiMH batteries typically have two to three times the capacity of NiCd batteries of the same size, with significantly higher energy density, although only about half that of lithium-ion batteries. NiMH batteries have almost entirely replaced NiCd.
These batteries are typically used as a substitute for similarly shaped non-rechargeable alkaline and other primary batteries. They provide a cell voltage of about 1.2V while fresh alkaline cells provide 1.5V; however devices designed for alkaline batteries operate until cell voltage gradually drops to around 1.0V, while the voltage of a fully-charged NiMH cell drops more slowly, giving good endurance for a 1.0V end point. NiMH batteries are less prone to leaking corrosive electrolyte than primary batteries.
Work on NiMH batteries began at the Battelle-Geneva Research Center following the technology's invention in 1967. It was based on sintered Ti2Ni+TiNi+x alloys and NiOOH electrodes. Development was sponsored over nearly two decades by Daimler-Benz and by Volkswagen AG within Deutsche Automobilgesellschaft, now a subsidiary of Daimler AG. The batteries' specific energy reached 50 W·h/kg (180 kJ/kg), specific power up to 1000 W/kg and a life of 500 charge cycles (at 100% depth of discharge). Patent applications were filed in European countries (priority: Switzerland), the United States, and Japan. The patents transferred to Daimler-Benz.
Interest grew in the 1970s with the commercialisation of the nickel–hydrogen battery for satellite applications. Hydride technology promised an alternative, less bulky way to store the hydrogen. Research carried out by Philips Laboratories and France's CNRS developed new high-energy hybrid alloys incorporating rare-earth metals for the negative electrode. However, these suffered from alloy instability in alkaline electrolyte and consequently insufficient cycle life. In 1987, Willems and Buschow demonstrated a successful battery based on this approach (using a mixture of La0.8Nd0.2Ni2.5Co2.4Si0.1), which kept 84% of its charge capacity after 4000 charge-discharge cycles. More economically viable alloys using mischmetal instead of lanthanum were soon developed. Modern NiMH cells were based on this design. The first consumer-grade NiMH cells became commercially available in 1989.
In 1998, Stanford Ovshinsky at Ovonic Battery Co., which had been working on MH-NiOOH batteries since mid-1980, improved the Ti–Ni alloy structure and composition and patented its innovations.
In 2008, more than two million hybrid cars worldwide were manufactured with NiMH batteries.
In the European Union due to its Battery Directive, nickel–metal hydride batteries replaced Ni–Cd batteries for portable consumer use.
In Switzerland in 2009, approximately 60% of portable rechargeable batteries were NiMH. In 2000, almost half of all portable rechargeable batteries sold in Japan were NiMH, compared to 22% in 2010. This percentage has fallen over time due to the increase in manufacture of lithium-ion batteries.
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