Repurposing of Fruit Peel Waste as a Green Reductant for Recycling of Spent Lithium-Ion Batteries.

The development of environmentally benign hydrometallurgical processes to treat spent lithium-ion batteries (LIBs) is a critical aspect of the electronic-waste circular economy. Herein, as an alternative to the highly explosive H2O2, discarded orange peel powder (OP) is valorized as a green reductant for the leaching of industrially produced LIBs scraps in citric acid (H3Cit) lixiviant. The reductive potential of the cellulose- and antioxidant-rich OP was validated using the 3,5-dinitrosalicylic acid and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic) acid assays. Leaching parameters such as OP concentration (200 mg), processing temperature (100 °C), H3Cit concentration (1.5 M), reaction duration (4 h), and slurry density (25 g/mL) were systematically optimized to achieve 80-99% leaching efficiencies of Ni, Mn, Co, and Li from the LIB "black mass". Importantly, solid side-streams generated by the OP-enabled leaching displayed negligible cytotoxicity in three different human cell lines, suggesting that the process is environmentally safe. As a proof of concept, Co(OH)2 was selectively recovered from the green lixiviant and subsequently utilized to fabricate new batches of LiCoO2 (LCO) coin cell batteries. Galvanostatic charge-discharge test revealed that the regenerated batteries exhibited initial charge and discharge values of 120 and 103 mAh/g, respectively, which is comparable to the performance of commercial LCO batteries. The use of fruit peel waste to recover valuable metals from spent LIBs is an effective, ecofriendly, and sustainable strategy to minimize the environmental footprint of both waste types.

Lignin@Nafion Membranes Forming Zn Solid-Electrolyte Interfaces Enhance the Cycle Life for Rechargeable Zinc-Ion Batteries.

Metallic zinc is an ideal anode material for rechargeable zinc-ion batteries (ZIBs), taking us beyond the lithium-ion era. In-depth understanding of the Zn metal surface is currently required owing to diverse but uncorrelated data about the Zn surface in mild environments. Herein, the surface chemistry of Zn is elucidated and the formation and growth of a zinc layer hydroxide is verified as an effective solid-electrolyte interface (SEI) during stripping/plating in mild electrolyte. The effects of battery separators/membranes on the growth of an effective SEI and deposited Zn are then investigated from the perspectives of structure, morphology, compositions, and interfacial impedance. Nafion-based membranes enable the formation of a planar SEI, which protects the metal surface and prevents short circuiting. Biomass@Nafion membranes are developed and assessed with a long cycle life of over 400 h compared with below 200 h for physical separators. The mechanism behind this is attributed to interaction between the membranes and Zn2+ , which enables reshaping of the Zn2+ coordination in an aqueous medium. Together with the advantages of using the membranes in ß-MnO2 |ZnSO4 |Zn, our work provides a feasible way to design an effective SEI for advancing the use of Zn anodes in rechargeable ZIBs.