The substitution of NaMgH3 for MgH2 greatly enhancing the hydrogen storage performance and mechanism of Li-Mg-N-H system

Metal nitrogen hydride (Li-Mg-N-H) is regarded as an ideal hydrogen storage material for automotive applications due to its advantages of high hydrogen storage capacity (5.6 wt%), low operating temperature, and good cycling performance, but the comprehensive hydrogen storage performance of this material still could be improved. For this reason, this paper constructed a Li-Na-Mg-N-H composite system by synthesizing NaMgH 3 to replace MgH 2 in the Li-Mg-N-H system. The improvement of the hydrogen absorption and desorption properties of the composite system after the replacement of MgH 2 by NaMgH 3 was investigated. Various properties and test results showed that the composite system after the replacement of MgH 2 by NaMgH 3 showed better hydrogen absorption and desorption properties. The initial/peak hydrogen release temperatures of Li-Na-Mg-N-H decreased from 135 ˚C/245 ˚C to 105 ˚C/145 ˚C, and the apparent activation energy of hydrogen release was reduced from 114.90 to 104.05 kJ/mol which means the kinetics of hydrogen absorption and desorption was greatly improved. The mechanism study shows that NaMgH 3 will react with LiNH 2 and forms the intermediate product Li 3 Na(NH 2 ) 4 during the hydrogen release process, which changes the hydrogen desorption pathway of the composite system and thus the hydrogen absorption and desorption kinetics were improved.