Nanostructured Ball-Milled Ni-Co-Mn Oxides from Spent Li-Ion Batteries as Electrocatalysts for Oxygen Evolution Reaction

Discovering sources of transition metals, such as Ni,Co, and Mn,has become crucial due to their broad applicability, particularlyas electrocatalysts for the oxygen evolution reaction (OER). Upcycledspent batteries have emerged as alternatives for transition metalsources for the OER electrocatalysts. In this work, Ni-Co-Mnoxalates were extracted from the spent LiNi x Co y Mn z O2 (NCM) cathode of lithium-ion batteries. The extractedoxalates were further processed via ball milling as a rapid and scalablemechanochemical route to engineer their structures. After calcination,Ni-Co-Mn oxides with nanosized granules on the surfacethat mainly consist of MnCo2O4 were obtained.With a correlation of morphology and trimetallic oxide formation withthe OER catalytic performance, Ni-Co-Mn oxides exhibitOER overpotentials of 367 and 732 mV in alkaline and neutral media,respectively, showing OER catalytic activity in a wide pH range. Theresults indicate that ball milling can induce particle size reductionand bond formation between metals to facilitate mixed-metal oxideformation. Furthermore, the resulting material is also applicableas the catalyst in the air cathode of Zn-air batteries, where thebattery achieved a power density of 85.42 mW cm(-2) and 100 h of cycling stability, showing comparability with a batterywith a Pt/C-Ir/C catalyst.