Dry Upcycling of Spent Zn‐C Primary Battery Black Mass Into ZnMn ₂ O ₄

ABSTRACT

Spent Zn‐C primary batteries represent an abundant secondary resource of Zn‐ and Mn‐containing black mass, yet most recycling approaches rely on multistep hydrometallurgical or high‐temperature pyrometallurgical processing. This study presents a sustainable and entirely dry upcycling route that converts spent black mass from Zn‐C primary batteries into high‐performance spinel‐type ZnMn ₂ O ₄ (ZMO), thereby facilitating the closed‐loop reuse of battery metals. The black mass is calcined at 600°C for 2 h without chemical leaching or solvents, yielding phase‐pure ZMO. A detailed characterization using XRD, XPS, EDS, Raman, and BET techniques confirms the successful synthesis of spinel‐structured nanoporous ZnMn ₂ O ₄ . When assessed as a supercapacitor electrode, the material exhibits a specific capacitance of 344 Fg ⁻¹ at 0.1 Ag ⁻¹ , highlighting its excellent redox activity and stability. The enhanced performance is attributed to the formation of a more ordered spinel framework, reduced electrolyte‐derived impurities, and improved charge‐transfer kinetics rather than a higher BET surface area. These results establish a solvent‐free and potentially scalable waste‐to‐resource strategy for converting spent primary‐battery black mass into functional supercapacitor electrodes.