Exploring pristine and Li-doped Mg2NiH4 compounds with potential lithium-storage properties: Ab initio insight

In this work, pure and Li-doped Mg2NiH4 hydrides are explored for potential Li-ion battery conversion anode materials applications from state-of-the-art Density functional theory. The most thermodynamically stable Li-doped Mg2NiH4 structure is determined, which possesses a smaller band gap than pure material and owns a theoretical specific capacity of 975.35 mA h g−1 and an average voltage of 0.437 V (vs. Li+/Li0). The Li-doping also improves the diffusion behavior of Li-ion in electrode material especially at 300 K, which implies the promising rate capability of the device at room temperature when the anode material is doped utilizing Li element. The non-empirical values of diffusion coefficients of Li-ion in both pure and Li-doped Mg2NiH4 system are also quantitatively determined from ab initio molecular dynamics. After Li-doping, the diffusion coefficient of Li-ion in the electrode is evidently increased to 1.791 × 10−9 m2 s−1 from the pristine 1.431 × 10−9 m2 s−1 at 300 K and the Li-ion conductivity is also increased. This theoretical study is proposed to encourage the design and experimental modification of better light-metal based hydrides for Li-ion battery conversion anodes applications.