The electrochemistry of Germanium nitride versus lithium

Germanium nitride (Ge₃N₄) was examined as a potential negative electrode material for Li-ion batteries. The electrochemistry of Ge₃N₄ versus Li showed high reversible capacity (500mAh/g) and good capacity retention during cycling. A combination of ex-situ and in-situ x-ray diffraction (XRD), ex-situ transmission electron microscopy (TEM) and ex-situ selective area electron diffraction (SAED) analyses revealed evidence supporting the conversion of a layer of Ge₃N₄ crystal into an amorphous Li₃N+Li_xGe nanocomposite during the first lithiation. The nanocomposite was electrochemically active via a reversible Li-Ge alloying reaction while a core of unreacted Ge₃N₄ crystal remained inactive. The lithium/metal nitride conversion reaction process was kinetically hindered resulting in limited capacity. Mechanical milling was found to improve the material capacity.