<p>The significance of recycling spent lithium-ion batteries (LIBs) has increased due to the rapid development of electric vehicles. This work developed a facile and green process that used recyclable ammonium hydrogen sulfate (NH₄HSO₄) and hydrogen peroxide (H₂O₂) to efficiently extract valuable metals from spent LIBs cathodes. During the investigation, NH₄HSO₄ was employed as the leaching agent and H₂O₂ served as the reducing agent. A series of single-factor experiments were performed to explore the effects of NH₄HSO₄ concentration, reducing agent type and concentration, reaction temperature, reaction time, and liquid–solid ratio on extraction efficiency. The crystal structure, surface morphology, and valence state of cathode materials were determined using X-ray diffraction, scanning electron microscopy coupled with energy dispersion spectroscopy, and X-ray photoelectron spectroscopy. The results showed that the synergistic impact of NH₄HSO₄ and H₂O₂ could greatly improve the leaching efficiency of Li, Ni, Co, and Mn. And the ideal leaching conditions resulted in Li, Ni, Co, and Mn leaching efficiencies of 98.7%, 97.68%, 98.32%, and 97.46%, respectively. This research established a theoretical framework and offered technical support to enhance the efficient retrieval of discarded LIBs.</p> Graphic Abstract <p></p>