Metal hydrides are promising high-capacity anode materials for Li-ion batteries but their conversion reaction with lithium suffers from low reversibility at room temperature (RT). Irreversibility issues in magnesium hydride MgH₂ thin films are investigated, as well-defined model system. Films are deposited over Cu current collectors by means of microwave plasma-assisted sputtering and coated with aluminum to minimize formation of passivating MgO native oxide. Structural and chemical properties of the electrodes have been analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and electrochemical impedance spectroscopy (EIS). Galvanostatic cycling reversibility at RT and C/50 regime is limited to 25% in the first cycle for 1 μm thick films. The lithiation of the thin film is complete and doubles its thickness. Despite drastic volume changes, neither cracks, voids, nor detachment of the thin film from the substrate are noticed. Moreover, electronic resistivity decreases upon lithiation due to the formation of metallic Mg. The origin of irreversibility phenomena in MgH₂ films is attributed to sluggish mass transport of species within the electrode at RT.

金属氢化物有望成为锂离子电池的高容量负极材料，但它们与锂的转化反应在室温（RT）下具有较低的可逆性。研究了氢化镁MgH ₂薄膜的不可逆性问题，以及定义明确的模型系统。借助于微波等离子体辅助溅射将膜沉积在Cu集电器上，并涂以铝，以最大程度地减少钝化MgO天然氧化物的形成。电极的结构和化学性质已通过X射线衍射（XRD），X射线光电子能谱（XPS），透射电子显微镜（TEM）和电化学阻抗谱（EIS）进行了分析。RT和C的恒电流循环可逆性对于1μm厚的膜，/ 50方案在第一个循环中被限制为25％。薄膜的锂化作用完成，其厚度增加一倍。尽管体积发生了急剧变化，但仍未发现裂纹，空隙或薄膜与基材的分离。此外，由于形成金属Mg，因此在锂化时电子电阻率降低。MgH ₂膜中不可逆现象的起源归因于RT电极内物质的缓慢传质。