For functional materials used for lithium ion batteries, their electrochemical properties are highly dependent on their defect structures. For examples, the reversible capacity of layered cathode such as LiCoO₂ is limited by its highly defective layered structure when state of charge greater than 50%. On the other hand, capacity of spinel or olivine cathodes show higher delithiation rate without noticeable phase change. Furthermore, with oxygen defects formed in Li₂MnO₃, the capacity of Li-rich layer-structured cathode formulated as xLi₂MnO₃-(1-x)LiMO₂(M = Mn, Ni, Co, etc.) was able to provide high reversible capacity (>250 mAh/g) for Li-ion battery applications. Similarly, the zero-strain anode materials Li₄Ti₅O₁₂ shows high interface polarization and low rate capability due to low electronic defects. Hopefully, the rate capability may be improved by introduction of more electronic defects on Ti cation sublattice.

In additions, the properties of solid state Li ion conductors for all-solid-state lithium batteries is strongly affected by their defect structures as well. Due to its better safety characteristics, solid-state lithium battery may use more reactive anode, such as Li. Thus, it is extremely crucial to find a stable solid electrolyte when the high-capacity Li anode is used. In our study, the stability of perovskite-based La_0.50Li_0.50TiO₃, NASICON-based Al-doped LiTi₂(PO₄)₃, and garnet-based Li₇La₃Zr₂O₁₂ against metallic Li were investigated. After La_0.50Li_0.50TiO₃ reacted with Li, the electron injection accompanied by the incorporation (insertion) of Li ion into vacant cation sites was likely to take place. The apparent reduction of tetravalent Ti into trivalent Ti was observed in La_0.50Li_0.50TiO₃. On the other hand, Al-doped LiTi₂(PO₄)₃, and garnet-based Li₇La₃Zr₂O₁₂ are much more stable when Li anode is used. For these solid electrolytes, the difference in stability against metallic Li may be rationalized based on their defect structures and corresponding atomic arrangements.