Effect of V doping on the electronic structure and hydrogen storage performance of the Li-Mg-N-H material

The effect of V doping on the electronic structure and hydrogen storage performance of the Li2MgN2H2 material and its mechanism were studied by using the first-principles plane-wave pseudopotential method based on density functional theory. The impurity replacement energy, energy band structure, density of states, charge density and population, and formation enthalpy of the Li2MgN2H2 system are obtained via structure calculations. The results indicate that for the V-doping Li2MgN2H2 system, V atom tends to occupy the Mg lattice site at position (sic). The electronic structure analysis results demonstrate that V doping increases the unit cell volume and decreases the band gap of the Li2MgN2H2 system. The strong interaction between V and N atoms weakens obviously the bond strength of Li-N and N-H bonds. The formation enthalpy calculation results indicate that V doping reduces significantly the formation enthalpy of the Li2MgN2H2 system by about 68.34 kJ/mol. All these factors are conducive to improving the hydrogen absorption kinetics of the Li2MgN2H2 material.