The Effect of TiO₂ and GeO₂ Composite Mixing on the Behavior of Macroporous Li-Ion Battery Anode Materials

Highly ordered, macroporous inverse opal structures can be made as TiO2/GeO2 nanocomposites with various GeO2 content and provide Coulombic and voltage stable response where the Ge content and its distribution influence the overall capacity at both slow and fast rates. These interconnected binder-free anodes were characterized using X-ray diffraction, high resolution transmission electron microscopy, selected area electron diffraction, energy dispersive X-ray spectroscopy and electron energy loss spectroscopy. The electrochemical response in half cells over 2000 cycles and various rates showed how the mixture affected key metrics for the material in battery cells. The data shows that a composite of intercalation and alloying compounds can provide good capacity (between theoretical maxima for either material alone) and excellent coulombic efficiency (>99%), even with low quantities of the higher capacity alloying compound. Compositional gradients or spatial heterogeneities in the distribution of one material in the composite are shown to affect capacity during cycling life, where a coulombically efficient increasing capacity is found as the higher capacity material becomes electrochemically active within the composite matrix as the material is modified during cycling.