Toward Closing the Loop for Cobalt-Free Lithium-Ion Batteries: Oxalate-Based Recycling and Direct Cathode Re-Synthesis

Demonstrating transition metals closed-loop recyclability for cobalt-free lithium-ion batteries is essential for sustainable and resilient battery value chains. This study demonstrates the recyclability of a spent high-voltage LiNi 0 . 5 Mn 1 . 5 O 4 (LNMO) lithium-ion battery via a hydrometallurgical process that enables reuse of recovered transition metals in new cathode synthesis, establishing a circular pathway. A deep eutectic solvent is used to leach the active material, achieving high extraction efficiencies for lithium (97.9 ± 1.7%), manganese (99.9 ± 2.3%), and nickel (97.7 ± 1.3%), meeting, as well as exceeding EU Battery Regulation targets. Selective precipitation with oxalic acid recovers nickel and manganese as a mixed metal oxalate, primarily manganese oxalate dihydrate (73.8 ± 1.9%) and nickel oxalate dihydrate (25.9 ± 1.8%). This recovered oxalate, combined with Li 2 CO 3 , is reused to synthesize new LNMO cathode material, delivering capacities of 126 mAh g -1 at 0.05C and 93 mAh g -1 at 1C, with capacity retentions of 85% after 100 cycles and 68% after 200 cycles. These results confirm the suitability of recycled oxalates for LNMO re-synthesis and provide a proof-of-concept for transition metal closed-loop recycling of next-generation cobalt-free lithium-ion batteries.