Synthesis of Nickel-Based Catalysts from Spent Lithium-Ion Batteries for Hydrogen Generation with Hydrazine Hydrate

The recovery and reuse of cathode materials from spent lithium-ion batteries (LIBs) have gained significant attention in recent years. In this work, we successfully transformed Ni, Co, Mn, and Al in spent LIBs into novel catalysts (i.e., Ni_xFe_yCoMnAl) for hydrogen generation from hydrazine hydrate (N₂H₄·H₂O), while recovering the Li as lithium phosphate to prepare new LIBs. The synthesized nickel-based catalysts were characterized by X-ray diffraction, electron microscopy techniques, and X-ray photoelectron spectroscopy, and the effects of Al, Co, and Mn in the cathode materials of spent LIBs on the hydrogen (H₂) production performance of the obtained Ni_xFe_yCoMnAl catalyst were investigated. The metallic Al in the catalyst enhanced the H₂ selectivity and the turnover frequency (TOF) in N₂H₄·H₂O decomposition, whereas Co had a minimal effect on the H₂ selectivity and TOF, and Mn increased the TOF without significantly affecting the H₂ selectivity. Furthermore, the influences of temperature and the NaOH and N₂H₄·H₂O concentrations on N₂H₄·H₂O decomposition were investigated to evaluate the performance of the Ni₁Fe₃CoMnAl catalyst. When N₂H₄·H₂O was completely decomposed, the optimal H₂ selectivity and TOF reached 91.67% and 38.56 h⁻¹, respectively. In addition, the catalyst exhibited excellent stability after ten cycles of catalytic N₂H₄·H₂O decomposition. This study provides a novel method for the value-added utilization of high-nickel ternary LIBs.