The recovery of critical metals from spent lithium-ion batteries (LIBs) is essential to reduce environmental impacts and promote circular economy strategies. This study developed a sustainable and scalable process for the recovery and complete valorization of lithium, cobalt, and other valuable components from end-of-life LIBs. Hydrometallurgical treatment using biodegradable citric and oxalic acids was employed as a green alternative to conventional inorganic acids, achieving high selectivity and reduced environmental impact. Experimental work was conducted on 3 kg of LIBs from discarded laptop batteries (Dell and HP). After safe discharge and dismantling, the cathode materials were thermally treated at 300 °C to detach active components, followed by acid leaching in 1 M citric acid at 30 °C, pH 2.5, and 6 h of reaction. Lithium and cobalt were recovered as oxalates with efficiencies of 90% and 85%, respectively, while copper, aluminum, and graphite were separated through mechanical and thermal processes. Beyond metal recovery, the process demonstrates a circular upcycling approach, transforming recovered materials into functional products such as aluminum keychains, copper jewelry, and graphite-based pencils. This integrated strategy connects hydrometallurgical extraction with material reuse, advancing toward a zero-waste, closed-loop system for sustainable LIB recycling and local resource valorization.