Metal Hydrides for Advanced Hydrogen/Lithium Storage and Ionic Conduction Applications

The widespread deployment of solar and wind energy requires advanced energy storage technologies to address the intermittent energy output and the loading limit of the current power grid. Materials are of critical importance for energy storage and conversion. Under such circumstances, development of the advanced energy storage materials featuring high capacity, large energy density, and good safety has been taking center stage in the research areas of physics, chemistry, and materials science. As a class of multifunctional materials, metal hydrides with great potential for energy-related applications such as rechargeable batteries, hydrogen energy storage, thermal storage, and ion conduction are one of the core focuses in the current development of advanced energy materials. In this Account, we summarize our research efforts in the manipulation of thermodynamics and kinetics for advanced hydrogen/lithium storage and ionic conduction applications. By optimization of the compositions, two series of hydrogen storage alloys including La-Mg-Ni-Co-Mn-Al and Ti-Zr-V-Mn-Cr-Ni were developed as the anodes of nickel-metal hydride (Ni/MH) batteries. Among these, La0.7Mg0.3Ni2.45Mn0.1Co0.75Al0.2 and Ti0.8Zr0.2(V0.533Mn0.107Cr0.16Ni0.2)4 alloys delivered similar to 370 and 412 mAh g(-1) maximum discharge capacities, respectively, >20% higher than those of the commercial AB5-type alloys. Through adding catalysts and fabricating nanostructures, the operation temperatures for hydrogen storage in light-metal hydrides (e.g., MgH2, NaAlH4, Mg(AlH4)2, LiBH4, and Li-Mg-N-H) were largely reduced, and the reversibility was remarkably improved. Support-free MgH2 nanoparticles (4-5 nm) started releasing hydrogen at 30 degree celsius with 6.7 wt % of reversible capacity. This is the first experimental observation of room-temperature hydrogen desorption for light-metal hydrides. Using alkali metals or alkaline earth metals to replace their metal counterparts, a series of metal silicides and sulfides were successfully synthesized at largely lower temperatures and studied for their lithium storage behaviors. This methodology provides a truly original approach for chemical prelithiation of the Si anode. By creating complexes or compositing with solid-state electrolytes, the conductivity of Li+ ions by the LiBH4-based electrolyte was efficiently increased to similar to 10(-3) S cm(-1) at 30 degree celsius with exceptional stability, comparable with the commercial organic liquid electrolyte, displaying remarkable practical application potential. For each application of metal hydrides, we start with the basic working mechanism and highlight the relationship between composition, structure, and properties. At the end of the Account, challenges and future development are proposed and discussed. We hope that this Account could help us to understand the current status and offer insight into future energy storage-related applications of metal hydrides.