Recycled electrode-based lithium-ion capacitors: an efficient route for transforming LIB waste into high-performance energy storage devices

Abstract

The rapid proliferation of lithium-ion batteries (LIBs) has amplified concerns, with waste levels predicted to reach 1.1 million tons by 2030. Current recycling efforts predominantly focus on either recovering critical metals such as lithium, nickel, and copper or the direct regeneration of electrode materials. However, a gap exists in fully utilizing these materials to create high-value products while recovering only metals. Besides, direct regeneration involves challenges due to impurities, material degradation, complex separation techniques, and difficulties restoring the original performances. Therefore, this study explores innovative upcycling strategies to efficiently repurpose cathode and anode materials from spent LIBs into lithium-ion capacitors (LICs) through a simplified and effective approach. Herein, mixed cobalt oxide (mCO-R), generated from the spent LiCoO₂ and activated graphene oxide (AGO-R), developed from the spent graphite, is utilized as an anode and cathode material for LICs, respectively, after coating onto a carbon fiber (CF) mat. Switching from a Cu current collector to a carbon fiber backbone is crucial in boosting Li-ion storage, accommodating volume changes in the internal void spaces, and providing mechanical stability. The resulting LIC delivers an energy density and power maxima of 206 Wh kg⁻¹ and 7560 W kg⁻¹, respectively, rendering 75% retention after prolonged durability of 10 000 cycles. Thus, the approach not only supports a circular economy offering sustainable solutions to mitigate LIB waste but also contributes to the rising demand for renewable energy storage, showcasing the value derived from end-of-life LIBs.