Energy nickel-metal hydride

H. Ogawa, M. Ikoma, H. Kawano, and I. Matsumoto, "Metal Hydride Electrode for High Energy Density Sealed Nickel—Metal Hydride Battery," Proceedings of the 16th International Power Sources Conference, UK, 1988. 

Battery technology continues to advance at a steady pace. Lithium batteries and nickel-metal-hydride batteries are now commonplace. These new rechargeable batteries eliminate the need for toxic cadmium and store more energy per unit mass. The detailed chemistry that underlies the newest advances in battery technology involves principles that are beyond the scope of an introductory course. 

High-power lithium-ion batteries are promising alternatives to the nickel metal hydride batteries which are currently used for energy storage in hybrid electric vehicles (HEVs). Currently, Li(Ni,Co)02-based materials are the most widely studied cathode materials for the high-power lithium-ion batteries [1-4]. Although Li(Ni,Co)02-based materials meet the initial power requirement for the HEY application, however, it has been reported that they... 

Energy Conversion Devices (ECD) of Troy, Michigan has announced a potential breakthrough in solid hydrogen storage. ECD is one of the parent companies of GM Ovonics, patent holder for the nickel metal hydride battery. A hydride, by definition, is a solid material that stores hydrogen. 

The sealed nickel—metal hydride battery has characteristics very similar to those of the sealed NiCd battery. The main difference is that the NiMH battery uses hydrogen, absorbed in a metal alloy, for the active negative material in place of the cadmium used in the NiCd battery. The NiMH batteries have a higher energy density and are considered more environmentally friendly than the NiCd battery. The sealed NiMH battery, however, does not have the very high rate capability of NiCd battery, and is less tolerant of overcharge. 

The sealed nickel-metal hydride cell (more consistently metal hydride-nickel oxide cell) has a similar chemistry to the longer-established hydro-gen-nickel oxide cell considered in Chapter 9. In most respects (including OCV and performance characteristics), it is very similar to the sealed nickel-cadmium cell, but with hydrogen absorbed in a metal alloy as the active negative material in place of cadmium. The replacement of cadmium not only increases the energy density, but also produces a more environmentally friendly power source with less severe disposal problems. The nickel-metal hydride cell, however, has lower rate capability, poorer charge retention and is less tolerant of overcharge than the nickel-cadmium cell. 

This cell system is also under active development for EV traction. Realistic targets are reported as 80 Wh/kg for energy density, 200 W/kg for power density, and a cycle life of over 1000. The Ovonic Battery Co have already demonstrated 67 Wh/kg for a 250 Ah battery, and Panasonic have reported a similar value for a 130 Ah unit. Thermal management and cost are likely to be the key factors limiting development of nickel-metal hydride technology for electric vehicles. 

With the widespread use of laptop computers, cellular telephones, and other portable electrical devices, the need for high energy density power sources has increased. In the past decade, two systems for these purposes have been commercialized nickel-metal hydride and lithium-ion batteries. For automotive applications, the interest in... 

Toyota s Prius uses the heavy, range-limited nickel-metal hydride battery, basically because it is safe. The Prius recaptures the braking energy (instead of wasting it in friction) and runs on electric power in stop-and-start traffic, but its all-electric mode of operation is limited. Toyota s Prius is also available in a version that has been converted to hydrogen by Quantum Fuel Systems. Toyota is planning to have a hybrid version of all its 2010 models. 

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.)...

Nickel-metal hydride batteries are produced in cylindrical, button, and flat designs in different sizes. Some characteristics of these batteries are summarized in Table 3. Ni/MH batteries have a much higher energy density than Ni/Cd batteries. Their energy density is about 50 Whkg-1 at 20 °C. 

Nickel-metal hydride (NiMH) cell — used in hybrid vehicles as a supplemental energy source ... 

Nickel oxide electrodes constitute the positive plates of several storage systems (among which nickel-zinc, nickel cadmium, nickel metal-hydride, sodium-nickel chloride) [16]. In recent years, the high-specific energy and specific power of Ni-Zn systems has increased the interest in their use for electric vehicles with respect to the past years, when their application was essentially limited by a short cycle life. 

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