Green energy storage: upcycling of lithium-ion batteries for their utilization in a high-performance asymmetric supercapacitor device

Abstract

The increasing demand for lithium-ion battery recycling has spurred efforts to develop sustainable strategies for the economic and greener recovery of its metal counterparts. The current hydrometallurgical approach is efficient, but selective separation of closely aligned metals remains difficult and costly. This study represents a pioneering step toward bypassing the costly hydrometallurgical approach by re-engineering spent cathode and anode materials for secondary energy storage applications. The electrode materials are recovered using a novel, greener organic-acid delamination method. Various synthesis or modification approaches are employed, and the solvothermal-assisted ball-milling method has proven effective and efficient for the cathode (LCO-BS_NF), whereas KOH activation has improved porosity and surface area, thereby enhancing the anode's efficiency (GR-C_NF). These materials were then tested through both three and two-electrode setups. The specific capacitances of LCO-BS_NF and GR-C_NF in the three-electrode setup, at a current density of 1 A g⁻¹, were 1167 and 281.56 F g⁻¹, respectively. An asymmetric device assembly comprising the two materials retained 56.73% of its capacitance after 10 000 cycles. The device's practical utility was tested by illuminating a red LED from both symmetric and asymmetric energy storage devices. The morphological, geometrical, chemical, and surface-area properties of the materials were also studied using FE-SEM, EDS, HR-TEM, XRD, XPS, and BET analysis. The current study employs both the cathode and anode components of LIB materials for utilization in energy storage devices, using as-recovered materials obtained through green recovery processes, thereby offering advantages in waste reduction, energy innovation, and sustainable resource utilization for next-generation energy storage devices.