Ternary Deep Eutectic Solvent (DES) with a Regulated Rate-Determining Step for Efficient Recycling of Lithium Cobalt Oxide

Abstract

Deep eutectic solvents (DESs) have attracted extensive research for their potential applications as leaching solvent to recycle valuable metal elements from spent lithium ion batteries (LIBs). Despite various advantages like being economical and green, the full potential of conventional binary DES has not yet been harnessed because of the kinetics during leaching. Herein, we consider the fundamental rate-determining-step (RDS) in conventional binary DES and attempt to design ternary DES, within which the chemical reaction kinetics and diffusion kinetics can be regulated to maximize the overall leaching rate. As a proof of concept, we show that the ternary choline chloride/succinic acid/ethylene glycol (ChCl/SA/EG) type ternary DES can completely dissolve LCO powder at 140 °C in 16 h. By systematically studying the leaching process at various conditions, the energy barrier during leaching can be calculated to be 11.77 kJ/mol. Furthermore, we demonstrate that the extraction of the cobalt ions from the leaching solution can be directly achieved by adding oxalic ions without neutralizing the solution. The precipitate can be used to regenerate LCO with high purity. The recycled materials show comparable electrochemical performance with commercial LCO. Our design strategy of ternary DES with regulated RDS is expected to have both scientific and technological significance in the field of hydrometallurgical recycling of LIBs.

Electron Transfer Kinetics in Ethaline/Water Mixtures: An Apparent Non‐Marcus Behavior in a Deep Eutectic Solvent

“…It was concluded that water addition (1–10 %) to the DES may even be beneficial in electrochemistry because water accelerates the relaxation and solvation and that drying a DES may be rather counterproductive [12] . Other works provide similar comments notably how the controlled addition of water could generate desired results [15,16] or about controlling the strength of the H‐Bonding by adding a third component in the DES [17] …”

“…[12] Other works provide similar comments notably how the controlled addition of water could generate desired results [15,16] or about controlling the strength of the H-Bonding by adding a third component in the DES. [17] Molecular electrochemistry methods as using cyclic voltammetry have been shown to be an efficient and practical tool for probing the basic properties of DES. [18] In the present work, we used cyclic voltammetry for examining the variation of the charge transfer kinetics upon water addition considering two examples in Ethaline: the one-electron oxidation of 1,1'ferrocene-dimethanol (Fc(MeOH) 2 ) and the one-electron oxidation of ferrocyanide [Fe(CN) 6 ] 4À .…”

Selective Extraction of Critical Metals from Spent Lithium-Ion Batteries

“…Wang et al also revealed that 89.1 wt % of Co was extracted when the LiCoO 2 cathode material was leached in ChCl–urea at 170 °C for 12 h with vigorous stirring . DES is proven to be a feasible approach for extracting critical metals from spent LIBs. − However, its application is still limited by high operation temperature (180–220 °C) and long reaction time (18–24 h), associated with high energy consumption and production cost . In addition, the diversity of constituent elements and differences in the crystal structures of metal compounds would limit the selectivity in extracting critical metals from multisource and heterogeneous hybrid cathode materials, thus lowering the feasibility of solvometallurgy systems.…”

Conjugated supercapacitor with suppressed self‐discharge constructed by pairs of prelithiated Nb2O5@C with optimized elemental and phase purity in the carbon shell

“…The ambitious goal of carbon neutralization calls for high‐performance energy storage systems. [ 1,2 ] Supercapacitors have become a considerable alternative to rechargeable batteries [ 3–6 ] due to their high power density and cycle stability, especially for applications that require instantaneous high power density and short‐term energy storage, [ 7–11 ] such as the gantry cranes that need to quickly grab cargo in ports. Despite numerous advantages, self‐discharge is one of the key problems which limits the wider applications of conventional electrochemical double‐layer capacitors (EDLCs).…”