Leaching kinetics and interface reaction of LiNi0.6Co0.2Mn0.2O2 materials from spent LIBs using GKB as reductant

Selective recycling of lithium from spent LiNixCoyMn1-x-yO2 cathode via constructing a synergistic leaching environment

The global response to lithium scarcity is overstretched, and it is imperative to explore a green process to sustainably and selectively recover lithium from spent lithium-ion battery (LIB) cathodes. This work investigates the distinct leaching behaviors between lithium and transition metals in pure formic acid and the auxiliary effect of acetic acid as a solvent in the leaching reaction. A formic acid-acetic acid (FA-AA) synergistic system was constructed to selectively recycle 96.81% of lithium from spent LIB cathodes by regulating the conditions of the reaction environment to inhibit the leaching of non-target metals. Meanwhile, the transition metals generate carboxylate precipitates enriched in the leaching residue. The inhibition mechanism of manganese leaching by acetic acid and the leaching behavior of nickel or cobalt being precipitated after release was revealed by characterizations such as XPS, SEM, and FTIR. After the reaction, 90.50% of the acid can be recycled by distillation, and small amounts of the residual Li-containing concentrated solution are converted to battery-grade lithium carbonate by roasting and washing (91.62% recovery rate). This recycling process possesses four significant advantages: i) no additional chemicals are required, ii) the lithium sinking step is eliminated, iii) no waste liquid is discharged, and iv) there is the potential for profitability. Overall, this study provides a novel approach to the waste management technology of lithium batteries and sustainable recycling of lithium resources.

A mechanochemical method for one-step leaching of metals from spent LIBs

A one-step system based on mechanochemical activation and the use of grape skins (GS) was proposed to recover metals from lithium-ion batteries (LIBs) cathode waste. The effects of the ball-milling (BM) speed, BM time, and quantity of added GS on the metal leaching rate were explored. The spent lithium cobalt oxide (LCO) and its leaching residue before and after mechanochemistry were characterized by SEM, BET, PSD, XRD, FT-IR, and XPS analysis. Our study shows that mechanochemistry promotes the leaching efficiency of metals from LIBs battery cathode waste by changing the cathode material properties (that is, reducing the LCO particle size (12.126 μm ∼ 0.0928 μm), increasing the specific surface area (0.123 m²/g ∼ 15.957 m²/g), enhancing the hydrophilicity and surface free energy (57.44 mN/m² ∼ 66.18 mN/m²), promoting the generation of mesoporous structures, refining grains, disrupting the crystal structure, and increasing the microscopic strain, while deflecting the binding energy of the metal ions). A green, efficient and environmentally friendly process for the harmless and resource-friendly treatment of spent LIBs has been developed in this study.

Leaching valuable metals from spent lithium-ion batteries using the reducing agent methanol

When considering resource shortages and environmental pressures, salvaging valuable metals from the cathode materials of spent lithium-ion batteries (LIBs) is a very promising strategy to realize the green and sustainable development of batteries. The reductive acid leaching of valuable metals from cathode materials using methanol as a reducing agent was studied. The results show that the leaching efficiencies of Co and Li are 99% under optimal leaching conditions. The leaching kinetics of cathode materials in a H₂SO₄-methanol system indicate that the leaching of Co and Li is controlled by diffusion, with activation energies of 69.98 and 10.78 kJ/mol, respectively. Detailed analysis of the leaching reaction mechanism indicates that methanol is ultimately transformed into formic acid through a two-step process to further enhance leaching. No side reactions occur during leaching. Methanol can be a sustainable alternative for the reductive acid leaching of valuable metals from spent LIBs due to its high efficiency, application maturity, environmental friendliness, and low cost.

The effect of ultrasound on synthesis and energy storage mechanism of Ti3C2Tx MXene

Removal of aluminum (abbreviated to Al) accounts for the main step for synthesizing Ti3C2Tx MXene. To date, the synthesis of Ti3C2Tx MXene is hampered by the low removal efficiency of Al from Ti3AlC2. Ultrasound was therefore introduced to achieve efficient synthesis of Ti3C2Tx MXene by promoting the removal rate of Al from Ti3AlC2. It was found that ultrasonic aid can significantly boost the removal efficiency of Al. Additionally, distinct kinetics for the removal of Al was recognized as the advent of ultrasonic intervention: (i) the shrinking core model was used to describe the removal kinetics of Al in the case without ultrasound, whilst the shrinking particle model was capable for the case in presence of ultrasound; (ii) the activation energy for removal of Al with ultrasonic aid was 70.2 kJ/mol, indicating a chemical reaction-controlled process, whereas the corresponding value for the case without sonication was 28.1 kJ/mol, demonstrating a mixed kinetic feature of the removal process of Al. Morphological study showed that ultrasound can remove the surface-adhering reaction products and favors the formation of structures with flower-like morphology. The sample without sonication treatment exhibited typical capacitive behavior, whilst the contribution of diffusion-limited capacitance in addition to the capacitive behavior was readily observed for the sonication-treated sample. Surface chemistry study indicated the more prevalent oxidation of the sonication treated sample, which gave rise to a higher specific capacitance than those without sonication treatment.

A green process for recycling and synthesis of cathode materials LiMn2O4 from spent lithium-ion batteries using citric acid

In view of the reducing reagent consumption and secondary pollution caused by recycling spent lithium-ion batteries (LIBs), a relatively green process has been proposed, because the complex process to separate metals and the use of a large number of environmentally unfriendly chemical reagents are not involved. This process combines acid leaching with the resynthesis of the cathode material to recycle LiMn2O4 (LMO) from spent LIBs. The leaching efficiencies of Li and Mn exceeded 94% under the conditions of 1.0 M citric acid concentration, solid-liquid ratio of 60 g L-1, and 60 min leaching time. After the leaching process, spinel LMO was successfully resynthesized by the sol-gel process using leachate. The sample calcined at 700 °C has the best electrochemical performances, and the initial discharge capacity at a 2C rate and capacity retention after 100 cycles were 87.85 mA h g-1 and 93.63%, respectively. The resynthesized cathode material possessed excellent cycling performance, which may result from Al doping. Furthermore, the mechanism of overall reaction and the formation process of complex Mn(C6H6O7)·H2O in the leaching process were explored. This study indicates that citric acid is an effective reagent for recycling cathode materials and the process is feasible.

Recycling of valuable metals from spent cathode material by organic pyrolysis combined with in-situ thermal reduction

From the perspective of environmental protection and resource recovery, recycling of spent lithium-ion batteries is a meaningful process. In this study, the removal of organics, liberatioin of electrode material, and reduction of high valence transition metal, as the key points in recycling efficiency of valuable metals, have been firstly achieved simultaneously by low temperature heat treatment recycling process. Pyrolysis characteristics of organics, phase transition behavior of spent cathode material and the thermal reduction mechanism were evaluated in the meantime. Results demonstrate that organics can be removed and the liberation of electrode materials can be improved by pyrolysis. High-valence transition metals in cathode materials are synchronously reduced to CoO, NiO, MnO, Ni, and Co based on the reducing action of organics, aluminum foil and conductive additives. At the same time, Li element exists in the form of Li₂CO₃, LiF and aluminum-lithium compound that can be recycled by water-leaching in the water impact crushing process while transition metals can be recycled by acid leaching without reducing agents. 81.26% of Li can be recycled from water-leaching process while the comprehensive recovery rate of Ni, Co, Mn is 92.04%, 93.01%, 92.21%, respectively. This study may provide an environmentally-friendly recycling flowchart of spent lithium-ion batteries.

Kinetics of Ni, V and Fe Leaching from a Spent Catalyst in Microwave-Assisted Acid Activation Process

Ni, V and Fe are the main contaminant metals that lead to the deactivation of the spent fluid catalytic cracking (SFCC) catalyst. In this work, the properties and distribution of Ni, V and Fe in the SFCC catalyst are investigated by employing EPMA-EDX, SEM and XPS techniques. The kinetics of Ni, V, Fe and Al leaching in organic and inorganic acids are studied under microwave heating. The EPMA-EDX results show that Fe and Ni mainly accumulate near the particle surface, while V eventually distributes throughout the catalyst particle. The XPS result suggests that the phase speciations of Ni in the SFCC catalyst are Ni, Ni2SiO4 and NiAl2O4, while Fe is present in a mixture of Fe3O4, Fe2O3 and Fe2SiO4. V is in the forms of V2O5 and VO2. Compared with oxalic acid, sulfuric acid has a better removal effect of contaminant metals, especially for Ni. The leaching kinetics results indicate that using either sulfuric acid or oxalic acid, the apparent activation energy of V is obviously lower than that of Fe and Ni, and the priority of the three contaminant metals in the removal effect is V > Fe > Ni. In addition, the leaching kinetics of contaminant metals in the microwave-assisted acid activation process are controlled by the surface chemical reaction control model.