Study of the Cu-Li-Mg-H system by thermal analysis

Abstract

Finite fossil-fuel supplies, nuclear waste and global warming linked to CO2 emissions have made the development of alternative/'green' methods of energy production, conversion and storage popular topics in today's energy-conscious society. These crucial environmental issues, together with the rapid advance and eagerness from the electric automotive industry have combined to make the development of radically improved energy storage systems a worldwide imperative. CuMg2 has an orthorhombic crystal structure and does not form a hydride: it reacts reversibly with hydrogen to produce Cu2Mg and MgH2. However, CuLixMg2-x (x = 0.08) has a hexagonal crystal structure, just like NiMg2, a compound known for its hydrogen storage properties. NiMg2 absorbs up to 3.6 wt% of H. Our studies showed that not only CuLixMg2-x absorbs a considerable amount of hydrogen, but also starts releasing it at a temperature in the range of 40-130 degrees C. In order to determine the properties of the hydrogenated CuLixMg2-x, absorption-desorption, Differential scanning calorimeter and thermo-gravimetric experiments were performed. Neutron spectra were collected to elucidate the behavior of hydrogen in the Li-doped CuMg2 intermetallic. Using DFT calculations we were able to determine the best value for x in CuLixMg2-x and compare different possible structures for the CuLixMg2-x hydride.