Transforming waste to value: High-performance Li-ion capacitors using recycled copper foil from spent lithium-ion batteries

The increasing demand for lithium-ion batteries (LIBs) is driving rapid advancements in energy storage technologies, with the market anticipated to expand significantly in the near future. With the growing role of electric vehicles (EVs), global e-waste generation is expected to rise significantly, creating challenges for waste management and resource conservation. This work presents a novel approach to recycle spent LIB copper foil into a high-performance Cu(OH)₂/graphene oxide (GO) composite anode for lithium-ion capacitors (LICs). Using a straightforward single-step electro-etching method, we create a flexible, binder-free Cu(OH)₂/GO composite electrode that exhibits exceptional electrochemical performance in both LIB and LIC applications. The Cu(OH)₂/GO composite electrode delivers a high initial discharge capacity of 2068 mAh/g in the half-cell LIB configuration. In the full cell LIC device, the electrode demonstrates superior charge storage capacity, high energy density (141.75 Wh/kg), high power density (6.47 kW/kg), and remarkable cyclic stability (93 % retention over 10,000 cycles). The research also highlights the repeated recycling of copper foil to maintain performance consistency, emphasizing the potential for sustainable electrode manufacturing. Theoretical and experimental studies, including density functional theory analysis, confirm the electrode's enhanced properties, highlighting a major advancement in recycling and energy storage technology. The current work establishes a strong foundation for sustainable e-waste recycling in energy storage systems.