L Journal of Alloys and Compounds 330–332 (2002) 752–759 www.elsevier.com / locate / jallcom High catalytic activity disordered VTiZrNiCrCoMnAlSn hydrogen storage alloys for nickel–metal hydride batteries * M.A. Fetcenko , S.R. Ovshinsky, K. Young, B. Reichman, C. Fierro, J. Koch, F. Martin, W. Mays, T. Ouchi, B. Sommers, A. Zallen Energy Conversion Devices / Ovonic Battery Company, 1707 Northwood Drive, Troy, MI 48084, USA Abstract Multielement, multiphase disordered metal hydride alloys have enabled the widespread commercialization of NiMH batteries by allowing high capacity and good kinetics while overcoming the crucial barrier of unstable oxidation / corrosion behavior to obtain long cycle life. Atomic engineering is used to promote a high concentration of active hydrogen storage sites vital for raising NiMH specific 21 21 energy to 100 Wh kg by utilizing metal hydride materials having in excess of 440 mAh g specific capacity. New commercial applications demand fundamentally higher specific power and discharge rate kinetics. Disorder at the metal / electrolyte interface has ˚ enabled a surface oxide with metallic nickel alloy inclusions having a diameter less than 70 A embedded within the oxide, which provide 21 exceptional catalytic activity to the metal hydride electrode surface and allowed NiMH specific power exceeding 1000 W kg .  2002 Elsevier Science B.V. All rights reserved. Keywords: Metal hydride; Disorder; Surface catalysis 1. Introduction • Easy application to series and series / parallel strings; • Choice of cylindrical or prismatic cells; Nickel–metal hydride (NiMH) batteries are in high • Safety in charge and discharge, including tolerance to volume commercial production for small portable battery abusive overcharge and overdischarge; applications, beginning in 1989 and achieving over 900 • Maintenance free; million annual worldwide cell production in 1999 [1]. The • Excellent thermal properties; driving force for the rapid growth of NiMH is both • Capability to utilize regenerative braking energy; technical and environmental, with energy and performance • Simple and inexpensive charging and electronic control advantages over nickel–cadmium fueling the explosive circuits; and growth of portable electronic devices such as communica- • Environmentally acceptable and recyclable materials. tion equipment and laptop computers. NiMH batteries have become the dominant advanced Recent development activity in NiMH batteries has battery technology for electric vehicle (EV) and hybrid focused on further improvements in peak power for HEV electric vehicle (HEV) applications by having the best and portable power tool applications. In this paper, we will overall performance in the wide-ranging requirements set report our results in raising power and high rate discharge by automotive companies. In addition to the essential capability, with particular emphasis to the metal hydride performance targets of energy, power, cycle life and electrode surface catalytic activity at the metal / electrolyte operating temperature, the following features of NiMH oxide interface. have established the technology preeminence: • Flexible cell sizes from 60 mAh–250 Ah; 2. Experimental • Safe operation at high voltage (3201 volts); • Excellent volumetric energy and power, flexible vehicle Metal hydride alloys having formulas typified by packaging; V Ti Zr Ni Cr Co Mn Al Sn (atomic %, a/ 5 9 26.2 38 3.5 1.5 15.6 0.4 0.8 o) and Ti Zr Ni Cr Co Mn (a/o) were prepared by 8 29 29 8 11 15 *Corresponding author. vacuum induction melting to have multiphase C14 and 0925-8388 / 02 / $ – see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0925-8388(01)01460-8