“…Functional oxide materials are widely used in numerous applications such as semiconductors, thermal/photo/electrochemical catalysts, Li-ion batteries (LIBs), and gas sensors. − Various types of defects, including point defects , (substitutive or interstitial), line defects (dislocation, stacking faults), and planar defects , (domain walls, twin boundary), exist in real oxides, which play a vital role in tuning the desired optical, electronic, and magnetic properties of oxides. − For instance, foreign metal doping or a O vacancy introduced into the oxides could alter the chemical affinity, band gap, and carrier concentration, thus affecting their catalytic performance . Another example is Li ions being electro/chemically inserted into WO 3 to act as electrodes for LIBs , or as electrochromic materials .…”