Nickel Metal Hydride Batteries Kwo Young www.mdpi.com/journal/batteries Edited by batteries Printed Edition of the Special Issue Published in Polymers Kwo Young (Ed.) Nickel Metal Hydride Batteries This book is a reprint of the Special Issue that appeared in the online, open access journal, Batteries (ISSN 2313-0105) from 2015–2016, available at: http://www.mdpi.com/journal/batteries/special_issues/ni-mh-batteries Guest Editor Kwo Young Department of Chemical Engineering and Material Science Wayne State University USA Editorial Office MDPI AG St. Alban-Anlage 66 Basel, Switzerland Publisher Shu-Kun Lin Managing Editor Jing Su 1. Edition 2016 MDPI • Basel • Beijing • Wuhan • Barcelona • Belgrade ISBN 978-3-03842-302-7 (Hbk) ISBN 978-3-03842-303-4 (electronic) Articles in this volume are Open Access and distributed under the Creative Commons Attribution license (CC BY), which allows users to download, copy and build upon published articles even for commercial purposes, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. The book taken as a whole is © 2016 MDPI, Basel, Switzerland, distributed under the terms and conditions of the Creative Commons by Attribution (CC BY-NC-ND) license (http://creativecommons.org/licenses/by-nc-nd/4.0/). III Table of Contents List of Contributors ......................................................................................................... VII About the Guest Editor..................................................................................................... IX Preface to “Nickel Metal Hydride Batteries”................................................................. XI Kwo-Hsiung Young Nickel Metal Hydride Batteries Reprinted from: Batteries 2016 , 2 (4), 31 http://www.mdpi.com/2313-0105/2/4/31.......................................................................... 1 Chapter 1: Reviews Kwo-hsiung Young, K. Y. Simon Ng and Leonid A. Bendersky A Technical Report of the Robust Affordable Next Generation Energy Storage System-BASF Program Reprinted from: Batteries 2016 , 2 (1), 2 http://www.mdpi.com/2313-0105/2/1/2.......................................................................... 11 Shiuan Chang, Kwo-hsiung Young, Jean Nei and Cristian Fierro Reviews on the U.S. Patents Regarding Nickel/Metal Hydride Batteries Reprinted from: Batteries 2016 , 2 (2), 10 http://www.mdpi.com/2313-0105/2/2/10........................................................................ 31 Taihei Ouchi, Kwo-Hsiung Young and Dhanashree Moghe Reviews on the Japanese Patent Applications Regarding Nickel/Metal Hydride Batteries Reprinted from: Batteries 2016 , 2 (3), 21 http://www.mdpi.com/2313-0105/2/3/21........................................................................ 72 Kwo-hsiung Young and Shigekazu Yasuoka Capacity Degradation Mechanisms in Nickel/Metal Hydride Batteries Reprinted from: Batteries 2016 , 2 (1), 3 http://www.mdpi.com/2313-0105/2/1/3........................................................................ 115 IV Chapter 2: Metal Hydride Alloys Jean Nei and Kwo-Hsiung Young Gaseous Phase and Electrochemical Hydrogen Storage Properties of Ti 50Zr 1Ni 44 X 5 ( X = Ni, Cr, Mn, Fe, Co, or Cu) for Nickel Metal Hydride Battery Applications Reprinted from: Batteries 2016 , 2 (3), 24 http://www.mdpi.com/2313-0105/2/3/24...................................................................... 159 Kwo-Hsiung Young, Taihei Ouchi, Baoquan Huang and Jean Nei Structure, Hydrogen Storage, and Electrochemical Properties of Body-Centered- Cubic Ti 40V 30Cr 15Mn 13 X 2 Alloys ( X = B, Si, Mn, Ni, Zr, Nb, Mo, and La) Reprinted from: Batteries 2015 , 1 (1), 74–90 http://www.mdpi.com/2313-0105/1/1/74...................................................................... 193 Shiuan Chang, Kwo-hsiung Young, Taiehi Ouchi, Tiejun Meng, Jean Nei and Xin Wu Studies on Incorporation of Mg in Zr-Based AB 2 Metal Hydride Alloys Reprinted from: Batteries 2016 , 2 (2), 11 http://www.mdpi.com/2313-0105/2/2/11...................................................................... 213 Kwo-Hsiung Young, Taihei Ouchi, Jean Nei and Dhanashree Moghe The Importance of Rare-Earth Additions in Zr-Based AB 2 Metal Hydride Alloys Reprinted from: Batteries 2016 , 2 (3), 25 http://www.mdpi.com/2313-0105/2/3/25...................................................................... 235 Kwo-hsiung Young, Diana F. Wong and Jean Nei Effects of Vanadium/Nickel Contents in Laves Phase-Related Body-Centered- Cubic Solid Solution Metal Hydride Alloys Reprinted from: Batteries 2015 , 1 (1), 34–53 http://www.mdpi.com/2313-0105/1/1/34...................................................................... 262 Kwo-hsiung Young, Taihei Ouchi, Tiejun Meng and Diana F. Wong Studies on the Synergetic Effects in Multi-Phase Metal Hydride Alloys Reprinted from: Batteries 2016 , 2 (2), 15 http://www.mdpi.com/2313-0105/2/2/15...................................................................... 284 V Diana F. Wong, Kwo-Hsiung Young, Taihei Ouchi and K. Y. Simon Ng First-Principles Point Defect Models for Zr 7Ni 10 and Zr 2Ni 7 Phases Reprinted from: Batteries 2016 , 2 (3), 23 http://www.mdpi.com/2313-0105/2/3/23...................................................................... 314 Lixin Wang, Kwo-Hsiung Young and Hao-Ting Shen New Type of Alkaline Rechargeable Battery—Ni-Ni Battery Reprinted from: Batteries 2016 , 2 (2), 16 http://www.mdpi.com/2313-0105/2/2/16...................................................................... 336 Tiejun Meng, Kwo-hsiung Young, John Koch, Taihei Ouchi and Shigekazu Yasuoka Failure Mechanisms of Nickel/Metal Hydride Batteries with Cobalt-Substituted Superlattice Hydrogen-Absorbing Alloy Anodes at 50 °C Reprinted from: Batteries 2016 , 2 (3), 20 http://www.mdpi.com/2313-0105/2/3/20...................................................................... 353 Chapter 3: Electrolyte Jean Nei, Kwo-Hsiung Young and Damian Rotarov Studies on MgNi-Based Metal Hydride Electrode with Aqueous Electrolytes Composed of Various Hydroxides Reprinted from: Batteries 2016 , 2 (3), 27 http://www.mdpi.com/2313-0105/2/3/27...................................................................... 375 Suli Yan, Kwo-Hsiung Young and K. Y. Simon Ng Effects of Salt Additives to the KOH Electrolyte Used in Ni/MH Batteries Reprinted from: Batteries 2015 , 1 (1), 54–73 http://www.mdpi.com/2313-0105/1/1/54...................................................................... 403 Chapter 4: Analytic Methodology Kwo-hsiung Young, Benjamin Chao and Jean Nei Microstructures of the Activated Si-Containing AB 2 Metal Hydride Alloy Surface by Transmission Electron Microscope Reprinted from: Batteries 2016 , 2 (1), 4 http://www.mdpi.com/2313-0105/2/1/4........................................................................ 429 VI Yi Liu and Kwo-Hsiung Young Microstructure Investigation on Metal Hydride Alloys by Electron Backscatter Diffraction Technique Reprinted from: Batteries 2016 , 2 (3), 26 http://www.mdpi.com/2313-0105/2/3/26...................................................................... 447 Hao-Ting Shen, Kwo-Hsiung Young, Tiejun Meng and Leonid A. Bendersky Clean Grain Boundary Found in C14/Body-Center-Cubic Multi-Phase Metal Hydride Alloys Reprinted from: Batteries 2016 , 2 (3), 22 http://www.mdpi.com/2313-0105/2/3/22...................................................................... 465 Negar Mosavati, Kwo-Hsiung Young, Tiejun Meng and K. Y. Simon Ng Electrochemical Open-Circuit Voltage and Pressure-Concentration-Temperature Isotherm Comparison for Metal Hydride Alloys Reprinted from: Batteries 2016 , 2 (2), 6 http://www.mdpi.com/2313-0105/2/2/6........................................................................ 481 VII List of Contributors Leonid A. Bendersky Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA. Shiuan Chang Department of Mechanical Engineering, Wayne State University, Detroit, MI 48202, USA. Benjamin Chao BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309, USA. Cristian Fierro BASF/Battery Materials–Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309, USA. Baoquan Huang BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309, USA. John Koch BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309, USA. Yi Liu Department of Chemistry, Wayne State University, Detroit, MI 48201, USA. Tiejun Meng BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309, USA. Dhanashree Moghe Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824, USA. Negar Mosavati Department of Chemical Engineering and Materials Science, Wayne State University, Detroit, MI 48202, USA. Jean Nei BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309, USA. K. Y. Simon Ng Department of Chemical Engineering and Materials Science, Wayne State University, Detroit, MI 48202, USA. Taihei Ouchi BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309, USA. Damian Rotarov BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309, USA. Hao-Ting Shen BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309, USA; Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA. Lixin Wang BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309, USA. VIII Diana F. Wong BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309, USA; Department of Chemical Engineering and Materials Science, Wayne State University, Detroit, MI 48202, USA. Xin Wu Department of Mechanical Engineering, Wayne State University, Detroit, MI 48202, USA. Suli Yan Department of Chemical Engineering and Materials Science, Wayne State University, Detroit, MI 48202, USA. Shigekazu Yasuoka FDK Corporation, 307-2 Koyagimachi, Takasaki 370-0071, Gunma, Japan. Kwo-Hsiung Young Department of Chemical Engineering and Materials Science, Wayne State University, Detroit, MI 48202, USA; BASF/Battery Materials—Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309, USA. IX About the Guest Editor Kwo-hsiung Young is the Chief Scientist in the BASF-Ovonic located in Rochester Hills, Michigan, USA. He graduated from National Taiwan University, Republic of China, in 1982 with a BS in Electrical Engineering and graduated from Princeton University, New Jersey, in 1989, with a Ph.D. also in the Electrical Engineering Department. He has been in the research field of Ni/MH batteries for more than 25 years. He is one of the key inventors who aim to increase the power of NiMH battery technology, and successfully implemented the technology in EV and HEV with support from United State Advanced Battery Consortium (USABC). He has 38 US Patents in Ni/MH battery technology which form the basis to the licenses for battery manufactures. Dr. Young also serves as research professor at Wayne State University, Michigan, where he supervises Ph.D. students in electrochemical materials research. In recent years, he has published over 100 technical papers in the field of metal hydrides for electrochemical applications. XI Preface to “Nickel Metal Hydride Batteries” Nickel/metal hydride (Ni/MH) batteries are presently used extensively in hybrid electric vehicles (HEVs). More than 10 million HEVs based on NiMH batteries have been manufactured and driven, and NiMH battery chemistry is expected to continue dominating the HEV market with its proven abuse tolerance, wide operating-temperature range, and durable service life. With the main goal of achieving higher gravimetric energy density while maintaining safety and robustness advantages, continuous efforts in improving the performances of NiMH batteries are very much needed in order to explore their possible use in other applications, such as battery-powered electric vehicles, the stationary market, and more. Meanwhile, with the inherited high volumetric energy density, the NiMH battery may have a chance to return to application in portable electronic devices. In this Special Issue of Batteries , review papers, current research, and future projection in the materials, fabrication methods, cell integration and development, performance evaluation, failure analysis, and other subjects related to NiMH batteries are included. Kwo Young Guest Editor Research in Nickel/Metal Hydride Batteries 2016 Kwo-Hsiung Young Abstract: Nineteen papers focusing on recent research investigations in the field of nickel/metal hydride (Ni/MH) batteries have been selected for this Special Issue of Batteries. These papers summarize the joint efforts in Ni/MH battery research from BASF, Wayne State University, the National Institute of Standards and Technology, Michigan State University, and FDK during 2015–2016 through reviews of basic operational concepts, previous academic publications, issued US Patent and filed Japan Patent Applications, descriptions of current research results in advanced components and cell constructions, and projections of future works. Reprinted from Batteries . Cite as: Young, K.-H. Research in Nickel/Metal Hydride Batteries 2016. Batteries 2016 , 2 , 31. 1. Introduction Nickel/metal hydride (Ni/MH) rechargeable batteries are one of the important power sources for various consumer types of mobile applications, stationary energy storage, and, most distinctively, transportation usages. In the consumer market, more than one billion cylindrical cells are built annually to replace highly toxic Ni–Cd batteries and throw-away primary alkaline batteries with Ni/MH batteries of the same nominal voltage (1.2 V) and higher energy [ 1 , 2 ]. In stationary applications, Ni/MH batteries offer a wide operation/storage temperature range, a high energy density, and a very long service life [ 3 – 5 ]. For propulsion applications, more than 10 million hybrid electrical vehicles currently on the road are powered by Ni/MH batteries [ 6 ]. New applications in start–stop types of micro-hybrid electrical vehicles [ 7 ], temporary energy storage for train braking [ 8 ], ferries [ 9 ], and buses [ 10 ] are on the horizon. Although Ni/MH batteries have an excellent track record for high abuse-tolerance and endurable service life, these batteries suffer from a relatively low gravitational energy density when comparing to rival Li-ion batteries [ 11 ]. The demand for higher mileage between charges limits the future perspectives of Ni/MH batteries in pure battery-powered electrical vehicles. In order to preempt the gap in energy density, ongoing research activities in Ni/MH are currently being conducted in the US, China, Japan, and Europe [ 12 ]. In this Special Issue of the journal Batteries, nineteen papers from research within the USA have been collected to reflect the current status of research and development in the area of Ni/MH batteries. 1 2. Contributions The selected papers presented in this Special Issue are highlighted in this section. They are mainly from the research work conducted under a United States Department of Energy (DOE)–Advanced Research Projects Agency–Energy granted program (DE-AR0000386) and can be divided into four general categories: reviews on overall programs and Patents in the area (four papers); metal hydride (MH) alloys used as negative electrode active materials in Ni/MH batteries (eight papers); electrolyte composition and additives (two papers); and uses of analytic tools to investigate the nature and failure modes of components in Ni/MH batteries (five papers). 2.1. Reviews in Related Work In this area, a single paper has been devoted to reviewing the major accomplishments of the Robust Affordable Next Generation Energy Storage System (RANGE) program funded by the DOE [ 13 ]; two papers are reviews of Patents, specifically those granted in the US [ 14 ] and applied in Japan [ 15 ]; and one review of the field of failure analysis of Ni/MH batteries [ 16 ]. In the RANGE program, new anodes, cathodes, and electrolytes—together with a new pouch type of cell assembly—were developed to boost the gravitational energy density of Ni/MH batteries to 145 Wh · kg − 1 on the cell level. The combination of an advanced Si-anode with an extremely high potential capacity (up to 4000 mAh · g − 1 ) and an ionic liquid electrolyte has led to a new era of Ni/MH battery development [ 13 ]. In the paper reviewing US Patents on the subject of Ni/MH batteries, 350 US Patents were studied, beginning with active materials, to electrode fabrication, cell assembly, system integration, application, and finally recovery and recycling [ 14 ]. This paper also gives a brief introduction to the major components used in Ni/MH batteries. Another paper reviewing Japanese Patent Application takes a different approach. Instead of by subject manner, these Patent Applications were categorized by the filing company/institute [ 15 ]. Applications from nine top Ni/MH battery manufacturers, five major component suppliers, and three research institutes (all based in Japan) are included, with special emphasis on the evolution of melting/casting apparatuses, fabrication of paste electrode, and cell construction. The last review paper focuses on studies of failure modes and degradation mechanisms of Ni/MH batteries [ 16 ]. The paper first gives a brief introduction to the structure of Ni/MH batteries and the common experimental methods used in failure analysis. It then describes the capacity loss mechanism under various conditions (temperature, rate, and storage duration), and finally, presents methods for improving the cycle stability using six approaches: improvement to cell design, negative and positive electrodes, separator, electrolyte, and other components. 2 2.2. Metal Hydride Alloys MH alloys are the active component in the negative electrodes of Ni/MH batteries and are capable of reversibly storing hydrogen in an electrochemical environment [ 17 ]. MH alloys with suitable metal-bond strengths for room-temperature electrochemical application can be categorized as solid-solution and pseudo-binary inter-metallic alloys, specifically A 3 B, A 2 B, AB, AB 2 , AB 3 , A 2 B 7 , and AB 5 , where A is one or a combination of rare earth, alkaline earth, and light transition metal elements (Ti and Zr) and B is from the group of transition metals (mainly Ni) [ 18 ]. Comparisons of the general properties [ 19 ] and the high-rate potentials [ 20 ] of these alloy systems are available. Out of the eight available alloy systems, four are discussed in this Special Issue and are summarized as follows. Modifications of the A-site atom in body-centered-cubic (bcc) solid-solution alloys increases the storage capacity [ 21 ]. The effects of the incorporation of Mg or Ce in the Laves phase-based AB 2 MH alloys are discussed in [ 22 , 23 ], respectively. Formula optimization [ 24 ] and A-site substitution [ 25 ] in a series of Laves phase-related bcc alloys leads to a MH alloy suitable for electrical vehicle applications (P37 in [ 13 ]). TiNi-based AB MH alloys were investigated due to their low raw material costs and because they are free of rare earth elements [ 19 ]. Density function theory has also been employed to study the solubility of two ZrNi-based intermetallic alloys [ 26 ]. Last but not least, a new concept of using nickel hydroxide as the anode for Ni–Ni batteries is discussed [ 27 ]. In addition to the eight papers focusing on MH alloys, the failure mechanisms of a series of Co-substituted A 2 B 7 superlattice alloys is discussed [ 28 ], and initial research activities focused on an Mg-based AB MH alloy can be found in the paper discussing the contribution of various hydroxides in the electrolyte [29]. 2.3. Electrolyte Part of the high-rate charge/discharge capabilities in Ni/MH batteries originates from the use of highly conductive alkaline electrolytes (30–35 wt% KOH). However, the highly corrosive nature of these electrolytes limits the choice of MH alloys. For example, extremely low cycle stabilities have been reported with Mg- [ 30 , 31 ] and V-containing [ 32 ] MH alloys. Therefore, studies focused on balancing corrosion and conductivity in the electrolytes were conducted through the choice of hydroxides [ 29 ] and salt additives [ 33 ]. In addition, the use of ionic liquid to replace alkaline solution as electrolyte was shown to be effective in reducing corrosion, which allowed attempts to develop high-capacity Si-anodes [13]. 2.4. Analytic Methodology Many analytic tools have been applied during the research and development of Ni/MH batteries. While analytical methods for MH alloy research can be found 3 in one article [ 34 ], those involved in the failure analysis are summarized in a paper in this Special Issue [ 16 ]. In this Special Issue, the many uses for transmission electron microscopy (TEM) [ 35 ], electron backscatter diffraction (EBSD) [ 36 , 37 ], and X-ray energy dispersive spectroscopy (EDS) elemental mapping in a scanning electron microscope (SEM) [ 28 ], X-ray diffraction (XRD), and newly developed electrochemical pressure–concentration–temperature (PCT) measurements [ 38 ] were demonstrated to be effective for investigations into the microstructures and various mechanisms in electrochemistry and hydrogen gas–solid interactions. TEM results for a Si-doped AB 2 MH alloy [ 35 ] revealed a highly catalytic surface/interface microstructure which accounts for the superior low-temperature performance of the alloy and varies greatly from the conventional nano-Ni clusters embedded in surface oxide model [ 39 , 40 ]. The alignment in the crystallographic orientations of the constituent phases revealed by the EBSD technique [ 36 , 37 ] confirm the cleanness of the interface, which is therefore capable of generating synergetic effects and boosting the electrochemical performance of the multi-phase MH alloy systems [ 25 ]. A study comparing gaseous phase PCT and electrochemical PCT further distinguishes the synergetic effects in both environments [ 38 ]. The last paper exhibits a combination of analytic tools—including inductively coupled plasma, XRD, SEM, and EDS—to study the failure mechanism of AB 5 and A 2 B 7 MH alloys after cycling at high temperature in a sealed-cell configuration [28]. 3. Conclusions The joint research efforts from BASF-Ovonic and their collaborators (2015–2016) are highlighted here through nineteen papers focused on the area of Ni/MH batteries in this Special Issue of Batteries. It has been demonstrated that achieving equalization of the energy density in the pack level between Ni/MH and rival Li-ion batteries is possible through the use of advanced components obtained from these studies. Future research will be focused on high-capacity Si-anodes, choice of high-voltages, multi-electron transfer cathodes, and implementation of the pouch cell design with the use of ionic liquid as the electrolyte. Acknowledgments: The Guest Editor (Kwo-Hsiung Young) thanks both the colleagues who made impressive and important contributions to the articles and the editorial team at the publisher MDPI for rending precious guidance. Kwo-Hsiung Young is also obligated to RoseFigura Jordan at the Rockefeller University for refinement in his writing skill. Conflicts of Interest: The author declares no conflict of interest. References 1. Teraoka, H. NiMH Stationary Energy Storage—Extreme Temperature and Long Life Developments. In Proceedings of the 33rd International Battery Seminar & Exhibit, Fort Lauderdale, FL, USA, 21–24 March 2016. 4 2. HighPower International. The Current Status and Future Trend of Domestic and International Market of Ni/MH Batteries. 2014. Available online: http://cbea.com/u/ cms/www/201406/06163842rc0l.pdf (accessed on 8 September 2016). (In Chinese) 3. Zelinsky, M.; Koch, J.; Fetcenko, M. Heat Tolerant NiMH Batteries for Stationary Power ; Ovonic Battery Company: Rochester Hill, MI, USA, 2010. 4. Zelinsky, M.; Koch, J. Batteries and Heat—A Recipe for Success? Available online: www.battcon.com/Papers Final2013/16-Mike%20Zelinsky%20-%20Batteries%20and% 20Heat.pdf (accessed on 8 September 2016). 5. Zelinsky, M.; Koch, J. Market Advancement of NiMH Batteries for Stationary Applications. Available online: www.battcon.com/PapersFinal2016/Zelinsky%20paper %202016.pdf (accessed on 8 September 2016). 6. Wikipedia. Hybrid Electric Vehicle. Available online: https://en.wikipedia.org/wiki/ Hybrid_electric_vehicle (accessed on 8 September 2016). 7. Panasonic. Headquarters News—Panasonic’s 12V Ni-MH Energy Recovery Systems in New Idle-Stop Minicars from Nissan and Mitsubishi. 2014. Available online: http://news. panasonic.com/global/press/data/2014/02/en140213-3/en140213-3.html (accessed on 8 September 2016). 8. Kawasaki Heavy Industry. Battery Power System (BPS) for Railways. Available online: http://global.kawasaki.com/en/energy/solutions/battery_energy/applications/bps. html (accessed on 8 September 2016). 9. Green City Ferries. MOVITZ—The World’s First Supercharged Electrical Ferry. Available online: http://www.greencityferries.com/boatfleet/movitz/ (accessed on 8 September 2016). 10. Zibo Guoli New Power Source Technology Co., Ltd. Available online: http://www. glxdy.com (accessed on 8 September 2016). 11. Young, K.; Wang, C.; Wang, L.Y.; Strunz, K. Electrical Vehicle Battery Technologies. In Electric Vehicle Integration into Modern Power Network ; Garcia-Valle, R., Lopes, J.A.P., Eds.; Springer: New York, NY, USA, 2013. 12. Yartys, V.A. Ti-Zr Based AB 2 Alloys for High Power Metal Hydride Batteries. In Proceedings of the 15th International Symposium on Metal-Hydrogen System, Interlaken, Switzerland, 7–12 August 2016. 13. Young, K.; Ng, K.Y.S.; Bendersky, L.A. A technical report of the Robust Affordable Next Generation Energy Storage System-BASF program. Batteries 2016 , 2 14. Chang, S.; Young, K.; Nei, J.; Fierro, C. Reviews on the U.S. Patents regarding nickel/metal hydride batteries. Batteries 2016 , 2 15. Ouchi, T.; Young, K.; Moghe, D. Reviews on the Japanese Patent Applications regarding nickel/metal hydride batteries. Batteries 2016 , 2 16. Young, K.; Yasuoka, S. Capacity degradation mechanisms in nickel/metal hydride batteries. Batteries 2016 , 2 17. Young, K. Stoichiometry in Inter-Metallic Compounds for Hydrogen Storage Applications. In Stoichiometry and Materials Science: When Numbers Matter ; Innocenti, A., Kamarulzaman, N., Eds.; InTech: Rijeka, Croatia, 2012. 5 18. Young, K. Electrochemical Applications of Metal Hydrides. In Compendium of Hydrogen Energy ; Barbir, F., Basile, A., Veziro ̆ glu, T.N., Eds.; Woodhead Publishing Ltd.: Cambridge, UK, 2016; Volume 3, pp. 289–304. 19. Nei, J.; Young, K. Gaseous phase and electrochemical hydrogen storage properties of Ti 50 Zr 1 Ni 44 X 5 ( X = Ni, Cr, Mn, Fe, Co, or Cu) for nickel metal hydride battery applications. Batteries 2016 , 2 20. Young, K.; Nei, J. The current status of hydrogen storage alloy development for electrochemical applications. Materials 2013 , 6 , 4574–4608. 21. Young, K.; Ouchi, T.; Huang, B.; Nei, J. Structure, hydrogen storage, and electrochemical properties of body-centered-cubic Ti 40 V 30 Cr 15 Mn 13 X 2 alloys ( X = B, Si, Mn, Ni, Zr, Nb, Mo, and La). Batteries 2015 , 1 , 74–90. 22. Chang, S.; Young, K.; Ouchi, T.; Meng, T.; Nei, J.; Wu, X. Studies on incorporation of Mg in Zr-based AB 2 metal hydride alloys. Batteries 2016 , 2 23. Young, K.; Ouchi, T.; Nei, J.; Moghe, D. The importance of rare-earth additions in Zr-based AB 2 metal hydride alloys. Batteries 2016 , 2 24. Young, K.; Wong, D.F.; Nei, J. Effects of vanadium/nickel contents in Laves phase-related body-centered-cubic solid solution metal hydride alloys. Batteries 2015 , 1 , 34–53. 25. Young, K.; Ouchi, T.; Meng, T.; Wong, D.F. Studies on the synergetic effects in multi-phase metal hydride alloys. Batteries 2016 , 2 26. Wong, D.F.; Young, K.; Ouchi, T.; Ng, K.Y.S. First-principles point defect models for Zr 7 Ni 10 and Zr 2 Ni 7 phases. Batteries 2016 , 2 27. Wang, L.; Young, K.; Shen, H. New type of alkaline rechargeable battery—Ni-Ni battery. Batteries 2016 , 2 28. Meng, T.; Young, K.; Koch, J.; Ouchi, T.; Yasuoka, S. Failure mechanisms of nickel/metal hydride batteries with cobalt-substituted superlattice hydrogen-absorbing alloy anodes at 50 ◦ C. Batteries 2016 , 2 29. Nei, J.; Young, K.; Rotarov, D. Studies on MgNi-based metal hydride electrode with aqueous electrolytes composed of various hydroxides. Batteries 2016 , 2 30. Mu, D.; Hatano, Y.; Abe, T.; Watanabe, K. Degradation kinetics of discharge capacity for amorphous Mg-Ni electrode. J. Alloys Compd. 2002 , 334 , 232–237. 31. Liu, J.; Jiao, L.; Yuan, H.; Wang, Y.; Liu, Q. Effect of discharge cut off voltage on cycle life of MgNi-based electrode for rechargeable Ni-MH batteries. J. Alloys Compd. 2005 , 403 , 270–274. 32. Yu, X.B.; Wu, Z.; Xia, B.J.; Xu, N.X. A Ti-V-based bcc phase alloy for use as metal hydride electrode with high discharge capacity. J. Chem. Phys. 2004 , 121 , 987–990. 33. Yan, S.; Young, K.; Ng, K.Y.S. Effects of salt additives to the KOH electrolyte used in Ni/MH batteries. Batteries 2015 , 1 , 54–73. 34. Young, K. Metal Hydride. In Reference Module in Chemistry, Molecular Sciences and Chemical Engineering ; Reedijk, J., Ed.; Elsevier: Waltham, MA, USA, 2013. 35. Young, K.; Chao, B.; Nei, J. Microstructures of the activated Si-containing AB 2 metal hydride alloy surface by transmission electron microscope. Batteries 2016 , 2 6 36. Liu, Y.; Young, K. Microstructure investigation on metal hydride alloys by electron backscatter diffraction technique. Batteries 2016 , 2 37. Shen, H.-T.; Young, K.-H.; Meng, T.; Bendersky, L.A. Clean grain boundary found in C14/body-center-cubic multi-phase metal hydride alloys. Batteries 2016 , 2 38. Mosavati, N.; Young, K.; Meng, T.; Ng, K.Y.S. Electrochemical open-circuit voltage and pressure- concentration-temperature isotherm comparison for metal hydride alloys. Batteries 2016 , 2 39. Young, K.; Huang, B.; Regmi, R.K.; Lawes, G.; Liu, Y. Comparisons of metallic clusters imbedded in the surface oxide of AB 2 , AB 5 , and A 2 B 7 alloys. J. Alloys Compd. 2010 , 506 , 831–840. 40. Young, K.; Chao, B.; Pawlik, D.; Shen, H. Transmission electron microscope studies in the surface oxide on the La-containing AB 2 metal hydride alloy. J. Alloys Compd. 2016 , 672 , 356–365. 7