A novel recycling process of the conductive agent in spent lithium iron phosphate batteries is demonstrated. Wet chemistry is applied in recovering lithium and iron phosphate, and the filter residue is calcined with a small amount of recovered iron phosphate in N2 at 900 °C to form a FeNP-codoped carbon catalyst, which exhibits a low half-wave potential and excellent durability for oxygen reduction. When applied in a rechargeable Zn–air battery, the power density can reach 80 mW cm−2.