One of the Li-LiPON decomposition products is Li 3 N, which has previously been investigated extensively as a Li-ion conductor. However, its electronic conductivity has not been discussed extensively. Figure shows the defect formation energy for Li 3 N as a function of the Fermi energy (E Fermi ). We calculated the band gap of Li 3 N to be ⇠2.13 eV from the GW approximation, which sets the x-axis range in Figure . We examined the defect energetics under three representative thermodynamic conditions (Figure ) in the accessible range: most Li-rich or reducing ( µ Li = 0 eV), moderate ( µ Li = 0.39 eV), and the most Li-poor or oxidizing ( µ Li = 0.78 eV).