A Superior Trifunctional Electrocatalyst of Ni–Mn–Co Sulfide Anchored on Nitrogen‐Doped Graphene Derived From Spent Lithium‐Ion Batteries

Nickel, cobalt, and manganese are difficult to separate and purify using traditional recycling methods for end‐of‐life ternary cathode materials from lithium‐ion batteries. This study presents a facile approach that enables efficient lithium extraction (94.1%), while most of the Ni/Co/Mn (>91%) are converted into Mn‐doped CoNi 2 S 4 (Mn‐CoNi 2 S 4 ) without separating Ni/Co/Mn. Additionally, this method also transforms the graphene oxide (GO) into nitrogen‐doped graphene (NG), which acts as a support for Mn‐CoNi 2 S 4 . The prepared Mn‐CoNi 2 S 4 /NG can be repurposed as an effective catalyst for the methanol oxidation reaction (MOR), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). The ORR half‐wave potential of Mn‐CoNi 2 S 4 /NG is 0.788 V, the OER potential is 1.475 V at 10 mA cm −2 , and the MOR potential is only 1.395 V at 100 mA cm −2 . The zinc–air batteries (ZABs) using Mn‐CoNi 2 S 4 /NG as the cathode exhibit high power densities, excellent reversibility, and cycling stability. Additionally, replacing OER with MOR results in methanol‐assisted ZABs, which offer superior energy efficiency and cycling stability. This study offers a novel method for effectively recycling valuable metals from retired lithium‐ion batteries for electrocatalysis.