Review on Li–Mg–N–H-based lightweight hydrogen storage composites and its applications: challenges, progress and prospects.

The increasing severity of global climate and energy problems has made renewable energy an inevitable choice for achieving a low-carbon society. Hydrogen is regarded as one of the most promising renewable energy due to its excellent characteristics, such as abundant and extensive resources, high calorific value, and non-pollution. How to achieve efficient hydrogen storage is one of the main hot spots of hydrogen energy research. For on-board hydrogen storage systems, which could be used for portable power sources and fuel cell vehicles, how to store hydrogen safely and effectively is one of the most urgent technological bottlenecks to overcome. The solid-state storage based on hydrogen storage materials has the advantages of low hydrogen storage pressure, high energy efficiency, safety and reliability, compared to conventional compressed hydrogen and cryogenic liquid hydrogen storage methods. It may be one of the most promising solutions to solve the above problems. Among the hydrogen storage materials, the lightweight composite hydrides Li–Mg–N–H system holds great promise for vehicular hydrogen storage applications owing to its moderate thermodynamic properties (∆Hdes ~ 44 kJ mol−1 H2 and ∆Sdes ~ 112 J mol−1 H2·K) and relatively high hydrogen capacity (~ 5.6 wt%). However, the Li–Mg–N–H material itself has poor cycling performance and a high energy barrier, resulting in a low dehydrogenation rate and high operating temperature. Apart from this, the multi-field coupling of mass and energy transfer also poses a challenge, hindering its on-board applications. In this paper, we present the modification methods and research status of the Li–Mg–N–H system's hydrogen storage materials. The effects of composition modification, nanocrystallization and catalyst addition on the thermal/kinetic properties of hydrogen storage materials in the Li–Mg–N–H system are expounded. The difficulties and directions for enhancing the hydrogen storage performance of Li–Mg–N–H system are discussed. [ABSTRACT FROM AUTHOR]