One of the emerging issues in solving the electronic waste problem is to address the growing amount of end-of-life Liion battery (LIB) waste. In this work, the regeneration of LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM 111) cathode active materials from end-of-life LIBs was successfully carried out via an easy, fast, and environmentally friendly recycling process that comprised three main stages, i.e., ascorbic acid leaching, oxalate coprecipitation process, and heat treatment. Ascorbic acid was able to leach Li, Ni, Co, and Mn ions from the spent NCM 111 cathode material with a relatively high leaching efficiency up to 90%. The following oxalic acid coprecipitation method has effectively recovered the transition metal ions in the leachate in the form of the metal oxalates MC 2 O 4 • 2H 2 O (M = Ni, Mn, and Co), as confirmed by the result of X-ray diffraction characterization. The quantitative analysis of metal ions using X-ray fluorescence revealed that the ratio of Ni, Co, and Mn in the precipitate was approximately 1:1:1, with a slightly lower amount of Mn. Regeneration of NCM 111 via the heat treatment of metal oxalates at temperatures of 800−950 °C successfully reproduced the material (R-NCM) with an R3m hexagonal-layered structure, which could be reemployed as the cathode in LIBs. Charge−discharge characterization of the as-fabricated LIB at 2.5−4.3 V revealed that the battery with the R-NCM cathode synthesized at 900 °C exhibited a slightly higher initial specific discharge capacity (164.9 mAh/g at 0.2 C) than that of commercial NCM (157.4 mAh/g at 0.2 C). Moreover, the Li-ion battery also showed a very stable performance with a capacity retention of 91.3% after 100 cycles at 0.2 C.

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Graphene has been gaining tremendous attention as an active material for energy storage devices owing to its large surface area, high electrical conductivity, and high electrochemical stability. However, the restacking of graphene layers during the synthesis process has become one issue that can reduce electrode performance. In this work, the structure of electro-exfoliated graphene (EG) is regulated to improve its electrochemical properties as the supercapacitor electrode using a facile postultrasonication treatment. The ultrasonicated EG exhibited a higher exfoliation degree than the raw EG as indicated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and Brunauer–Emmett–Teller (BET) characterization results. Ultrasonicated samples were then tested using three-electrode configuration, which obtained a maximum specific capacitance of 140.5 F g–1 at 0.5 A g–1, which is higher than that of the sample prepared without ultrasonication treatment (79.0 F g–1) at the same current density. Moreover, the cycling performance of ultrasonicated EG was examined using two-electrode measurement yielding the highest capacitance retention of 92.9% after 10,000 cycles at 1 A g–1, which can improve the stability of EG than the sample without ultrasonication (82.2%). These results indicate that ultrasonication can be applied as a straightforward treatment to modify exfoliation degree and lateral size of EG sheets leading to the enhancement of supercapacitor electrode performance.