Glassy Li3PO4 thin film is homogeneously deposited onto lithium metal foils. Li3PO4 thin film has an electronic conductivity of 1.4 × 10−10 S/cm. Li3PO4 thin film has an ionic conductivity of 2.8 × 10−8 S/cm. Li3PO4 coated lithium metal anodes have long cycle life performance.