Nickel metal hydride electrochemical cell

Those rare-earth AB -type hydrides were quickly utilized in rechargeable nickel metal hydride batteries where electrochemical hydrogen charging and discharging take place at ambient temperature. Such electrochemical hydrogen storage is reversible, when the negative hydride electrode (anode) is combined with the positive Ni electrode (cathode) in the battery cell.. 

The manufacture of secondary batteries based on aqueous electrolytes forms a major part of the world electrochemical industry. Of this sector, the lead-acid system (and in particular SLI power sources), as described in the last chapter, is by far the most important component, but secondary alkaline cells form a significant and distinct commercial market. They are more expensive, but are particularly suited for consumer products which have relatively low capacity requirements. They are also used where good low temperature characteristics, robustness and low maintenance are important, such as in aircraft applications. Until recently the secondary alkaline industry has been dominated by the cadmium-nickel oxide ( nickel-cadmium ) cell, but two new systems are making major inroads, and may eventually displace the cadmium-nickel oxide cell - at least in the sealed cell market. These are the so-called nickel-metal hydride cell and the rechargeable zinc-manganese dioxide cell. There are also a group of important but more specialized alkaline cell systems which are in use or are under further development for traction, submarine and other applications. 

In standard electrochemical notation, the above cell would be referred to as MH/M/aqueous KOH/Ni(OH)2/NiOOH. However, the current denomination is Ni/MH (nickel/metal hydride cell). 

Fig. 13.47. Discharge curve for advanced prototype electric vehicle cell demonstrating 95 W h kg-1 cell-specific energy. (Reprinted from S. R. Ovshinsky, S. K. Dhar, S. Venkatesan, D. A. Corrigan, A. Holland, M. A. Fetcenko, and P. R. Gifford, Ovonic Nickel Metal Hydride Technology for Consumer and Electric Vehicle Batteries-A Review and Update," in Batteries for Portable Applications and Electric Vehicles, C. F. Holmes and A. R. Landgrebe, eds., Electrochemical Society Proc. PV97-18, p. 706, Fig. 1, 1997. Reproduced by permission of The Electrochemical Society, Inc.)...

Lead-acid, nickel-iron (Ni-Fe), nickel-cadmium (NiCd), and nickel-metal hydride (NiMH) batteries are the most important examples of batteries with aqueous electrolytes. In lead-acid batteries, the overall electrochemical reaction upon discharge consists of a comproportionation of Pb° and Pb4+ to Pb2+. All nickel-containing battery reactions are based on the same cathodic reduction of Ni3+ to Ni2+, but utilize different anodic reactions providing the electrons. Owing to toxicity and environmental concerns, the formerly widely used Cd°/Cd2+ couple (NiCd cells) has been almost entirely replaced by H/H+, with the hydrogen being stored in a special intermetallic compound (NiMH). 

B) The nickel-metal hydride (NIMH) rechargeable secondary electrochemical cell, introduced by Beccu87 in 1967, has a nickel oxyhydroxide NiO(OH) electrode and a hydrogen-adsorbing alloy M (e.g., Ti2Ni) at the other electrode in the discharge mode the reaction is... 

SECTION 20.7 A battery is a self-contained electrochemical power source that contains one or more voltaic cells. Batteries are based on a variety of different redox reactions. Several common batteries were discussed. The lead-acid battery, the nickel-cadmium battery, the nickel-metal-hydride battery, and the lithium-ion battery are examples of rechargeable batteries. The common alkaline dry cell is not rechargeable. Fuel cells are voltaic cells that utilize redox reactions in which reactants such as H2 have to be continuously supplied to the cell to generate voltage. 

Different technologies can be used to store electrical energy in road vehicles. Notable technologies today are lead acid, nickel metal hydride, and Hthium ion batteries, and also double-layer capacitors (supercapacitors). Electrochemical high-temperature cells (e.g., ZEBRA) are no longer considered for most appHcations in passenger... 

Batteries contain a range of recyclable metals and can thus be used as sources of raw materials. Below you will find a selection of the major recycling procedures for portable batteries from the various electrochemical systems. There are sufficient facilities to deal with round and button cell batteries containing lead, nickel/ cadmium, nickel/metal hydride, and mercury. For the newer nickel/metal hydride and lithium systems, however, recycling is still in the early stages. For all the other aforementioned systems, such procedures have been in place for some time now. 

In that respect, one of the great successes in electrochemical science in recent years was the development and commercialization of Li ion batteries [11,12]. In addition to R D of Li and Li ion batteries overthe past few years, the development and commercialization of other novel battery systems, such as nickel metal-hydride [13], zinc-air [13], and practical fuel cells [14] have taken place within the framework of a general effort to develop alternative... 

Gu, W.B., Wang, C.Y., and Liaw, B Y. (1998) Micro-macroscopic coupled modeling of batteries and fuel cells - II. Application to nickel-cadmium and nickel-metal hydride cells. /. Electrochem. Soc., 145 (10), 3418-3427. 

A polymer electrolyte is also referred to as a solid solvent that possesses ion transport properties similar to that of the common liquid ionic solution. It usually comprises a polymer matrix and electrolyte, wherein the electrolyte such as a lithium salt dissolves in a polymer matrix. The research and development of polymer electrolytes have drawn great attention in the last three decades as they are applied in many electrochemical devices such as hthium batteries, nickel - metal hydride (Ni/MH) batteries, fuel cells/direct methanol fuel cells, supercapadtors, electrochromic devices and the like (Gray, 1991 Stephan, 2006). 

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