Direct Upcycling of Spent Lithium‐Ion Battery Electrodes for Sustainable Ammonium‐Ion Storage

ABSTRACT The rapid growth in lithium‐ion battery (LIB) consumption has generated an enormous volume of spent batteries, raising significant environmental and sustainability concerns. Herein, we report direct repurposing of recovered cathode and anode materials from spent LIBs as active electrodes for aqueous ammonium ion (NH 4 + ) storage systems. We observed that defect‐rich, partially reconstructed structures generated during prolonged Li + insertion/extraction processes are intrinsically favorable for NH 4 + storage, providing abundant active sites and rapid ion‐transport pathways. Benefiting from these features, the recovered cathode delivers a high specific capacity of 384 C g −1 at 0.6 A g −1 , while the recovered anode exhibits 145 F g −1 at 1 A g −1 . An asymmetric NH 4 + storage device assembled from spent LIB‐derived electrodes achieves an energy density of 41 Wh kg −1 at a power density of 385 W kg −1 , with 95% capacitance retention after 20 000 cycles. This work demonstrates a practical pathway for upcycling spent LIB waste into high‐value NH 4 + storage materials, advancing circular battery resource utilization and sustainable aqueous energy storage technologies.