Hydrogen storage alloy development for wide operating temperature nickel-metal hydride battery applications

Due to the increased demand of environmentally sustainable energy resources, reliable energy storage technologies become more essential than ever. Other emerging energy storage applications include uninterruptible power supply, cell phone towers, and sensors/monitors for outdoor systems (utility line, traffic control, etc.), and automotive emergency call system. The common requirements for above-mentioned applications are high safety and durability, easy maintenance, and the most important of all, wide operating temperature range. With its proven reliability, nickel metal hydride (NiMH) battery has become very competitive in these fields. Although NiMH battery can function in a wide temperature range, extreme temperatures cause some operating difficulties. Exposure to elevated temperatures lead to premature NiMH battery material failure. At ultra-low temperature, NiMH battery's alloy anode experiences sluggish bulk reaction and decreased surface reactivity. In this review, the fundamentals of NiMH battery electrochemical reactions and failure mechanisms at extreme temperatures are explained, followed by a report focused on the research effort of hydrogen storage alloy for extreme temperature applications, and finally an alloy development plan for improved wide-temperature-range operation is discussed.