Editing Nickel–metal hydride battery (section)

== History ==
[[File:Nimh disassembled.jpg|thumb|Disassembled NiMH [[AA battery]]: {{ordered list
| Positive terminal
| Outer metal casing (also negative terminal)
| Positive electrode
| Negative electrode with current collector (metal grid, connected to metal casing)
| Separator (between electrodes)
}}]]
{{See also|History of the battery}}

Work on NiMH batteries began at the [[Battelle Memorial Institute|Battelle]]-Geneva Research Center following the technology's invention in 1967. It was based on [[sintering|sintered]] Ti<sub>2</sub>Ni+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&nbsp;W·h/kg (180&nbsp;kJ/kg), specific power up to 1000&nbsp;W/kg and a life of 500 [[charge cycle]]s (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.<ref>The US patent is {{cite patent | country=US | status=patent | number = 3824131A | title = Negative electrode of titanium-nickel alloy hydride phases | invent1 = Dr. Klaus Beccu | assign1 = Battelle-Geneva R&D Center}}. For the performance data, see the "Examples" section.</ref>

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|Philips Laboratories]] and France's [[French National Centre for Scientific Research|CNRS]] developed new high-energy hybrid alloys incorporating [[rare-earth metal]]s 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 La<sub>0.8</sub>Nd<sub>0.2</sub>Ni<sub>2.5</sub>Co<sub>2.4</sub>Si<sub>0.1</sub>), 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.<ref name="rdjapan">{{cite journal | last1=Nii | first1=K. | last2=Amano | first2 = M. | year = 1997 | title = R & D of Hydrogen Absorbing Alloys in Japan | journal = Acta Metallurgica Sinica | volume = 10 | issue = 3 | pages = 249–255 | url = http://www.amse.org.cn/EN/abstract/abstract13633.shtml | access-date = 10 September 2011}}</ref> The first consumer-grade NiMH cells became commercially available in 1989.<ref>[http://www.economist.com/displaystory.cfm?STORY_ID=10789409 In search of the perfect battery], ''[[The Economist]]'', 6 March 2008.</ref>

In 1998, [[Stanford Ovshinsky]] at [[Energy Conversion Devices|Ovonic Battery Co.]], which had been working on MH-NiOOH batteries since mid-1980,<ref>{{cite web | url=https://patents.google.com/patent/US4623597A/en?oq=US4%2c623%2c597 | title=Rechargeable battery and electrode used therein }}</ref> improved the Ti–Ni alloy structure and composition and patented its innovations.<ref>{{cite patent | country = US | status = patent | number = 6413670 | title =High power nickel metal hydride batteries and high power alloys/electrodes for use therein | pubdate = July 2, 2002 | fdate = December 8, 1998}}</ref>

In 2008, more than two million hybrid cars worldwide were manufactured with NiMH batteries.<ref>Avicenne Conf., Nice 2008, M. A. Fetcenko/ECD.</ref>

In the European Union due to its [[Battery Directive]], nickel–metal hydride batteries replaced Ni–Cd batteries for portable consumer use.<ref>{{Cite journal|title=Directive 2006/66/EC of the European Parliament and of the Council of the 6 September 2006 on batteries and accumulators and repealing Directive 91/157/EEC|url=http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2006:266:0001:0014:EN:PDF|journal=[[Official Journal of the European Union]]|publisher=[[European Union]]|issue=L 266|date=2006-09-26|access-date=2015-11-13|format=PDF}}</ref>

About 22% of portable rechargeable batteries sold in Japan in 2010 were NiMH.<ref name="bajstat">{{cite web | url=http://www.baj.or.jp/e/statistics/06.html | title = Secondary battery sales statistics by volume | publisher = Battery Association of Japan | access-date = 10 September 2011}}</ref> In Switzerland in 2009, the equivalent statistic was approximately 60%.<ref>{{cite web|url=http://inobat.ch/fileadmin/user_upload/pdf_09/Absatz_Statistik_2008.pdf |title=Batterien-Absatzstatistik 2008 |publisher=INOBAT (the Swiss interest organisation for battery disposal) |access-date=10 September 2011 |page=2 |language=de |trans-title=Battery Sales Statistics 2008 |url-status=dead |archive-url=https://web.archive.org/web/20111114174228/http://www.inobat.ch/fileadmin/user_upload/pdf_09/Absatz_Statistik_2008.pdf |archive-date=November 14, 2011 }}</ref> This percentage has fallen over time due to the increase in manufacture of [[Lithium-ion battery|lithium-ion]] batteries: in 2000, almost half of all portable rechargeable batteries sold in Japan were NiMH.<ref name="bajstat" />

In 2015 [[BASF]] produced a modified microstructure that helped make NiMH batteries more durable, in turn allowing changes to the cell design that saved considerable weight, allowing the specific energy to reach 140 watt-hours per kilogram.<ref>{{Cite news |last=Bullis |first=Kevin |date=February 19, 2015 |title=Old Battery Type Gets an Energy Boost |work=Technology Review |url=https://www.technologyreview.com/2015/02/19/110774/old-battery-type-gets-an-energy-boost/ |access-date=2023-11-13}}</ref>