Resource Recovery of Spent Lithium-Ion Battery Cathode Materials by a Supercritical Carbon Dioxide System.

The increasing global market size of high-energy storage devices due to the boom in electric vehicles and portable electronics has caused the battery industry to produce a lot of waste lithium-ion batteries. The liberation and de-agglomeration of cathode material are the necessary procedures to improve the recycling derived from spent lithium-ion batteries, as well as enabling the direct recycling pathway. In this study, the supercritical (SC) CO2 was innovatively adapted to enable the recycling of spent lithium-ion batteries (LIBs) based on facilitating the interaction with a binder and dimethyl sulfoxide (DMSO) co-solvent. The results show that the optimum experimental conditions to liberate the cathode particles are processing at a temperature of 70 °C and 80 bar pressure for a duration of 20 min. During the treatment, polyvinylidene fluoride (PVDF) was dissolved in the SC fluid system and collected in the dimethyl sulfoxide (DMSO), as detected by the Fourier Transform Infrared Spectrometer (FTIR). The liberation yield of the cathode from the current collector reaches 96.7% under optimal conditions and thus, the cathode particles are dispersed into smaller fragments. Afterwards, PVDF can be precipitated and reused. In addition, there is no hydrogen fluoride (HF) gas emission due to binder decomposition in the suggested process. The proposed SC-CO2 and co-solvent system effectively separate the PVDF from Li-ion battery electrodes. Thus, this approach is promising as an alternative pre-treatment method due to its efficiency, relatively low energy consumption, and environmental benign features.

Study on preparation of UV-CDs/Zeolite-4A/TiO2 composite photocatalyst coupled with ultraviolet-irradiation and their application of photocatalytic degradation of dyes.

In this work, ultraviolet irradiation was employed to assist in the preparation of a novel photocatalyst composite in the form of carbon dots/zeolite-4A/TiO2, using coal tailings as the source of silicon-aluminum and carbon. The composite was designed for the degradation of methylene blue under 500 W of UV light irradiation. Zeolite-4A was used as a support for the well-dispersed carbon dots and TiO2 nanoparticles. The as-prepared composites were subjected to thorough characterization, confirming the successful formation of zeolite-4A with a cube structure, along with the loading of TiO2 and coal-based CDs in the composites. The experimental results demonstrated that the UV-CZTs nanocomposites exhibited a remarkable removal efficiency of 90.63% within 90 min for MB. The corresponding rate constant was exceptionally high at 0.0331 min-1, surpassing that of the Dark-CZTs and pure TiO2. This significant enhancement was possibly due to the synergistic effect of adsorption photocatalysis of the UV-CZTs, combined with the excellent electron-accepting capabilities of the coal-based CDs, which led to highly improved charge separation. An investigation of the spent photocatalyst's recyclability revealed that it retained a remarkable 82.94% MB removal efficiency after five consecutive cycles, signifying the stability of the composite. Trapping experiments also elucidated the primary reactive species responsible for MB degradation, which were identified as photo-generated holes and ⸱O2- species. By this process, the hydroxyl radicals generated in the system successfully promoted the transformation of coal tailings to coal-based zeolite and coal-based CDs. Coal-based zeolite served as an excellent carrier of titanium dioxide, which improved its dispersibility. The inhibition of e--h+ recombination of titanium dioxide by introducing coal-based CDs improved the photocatalytic ability of titanium dioxide. Through this study, coal tailings, as a coal processing waste, were transformed into high-value materials, and relevant photocatalytic composite materials could be prepared with broad application prospects.

Structural Characterization and Molecular Model Construction of High-Ash Coal from Northern China.

High-ash coal, also known as low-grade coal, has becomes a viable alternative in recent years to high-quality coal because available resources have become increasingly scarce due to extensive mining activity. This work aims to provide a comprehensive understanding of the structural characteristics of high-ash coal and construct a plausible molecular structure to elucidate its chemical reactivity in future applications. Its properties were investigated using Solid-state 13C nuclear magnetic resonance (13C NMR), X-ray photoelectron spectroscopy analysis (XPS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The molecular structure was constructed and validated using Material Studio, LAMMPS Software Package, and MATLAB program. The characterization results revealed that high-ash coal contains 72.15% aromatic carbon, significantly surpassing the percentage of aliphatic carbon (27.85%). The ratio of bridgehead carbon to peripheral aromatic carbon was calculated as 0.67, indicating that the pentacene is the main carbon skeleton form in the high-ash coal structure. Furthermore, oxygen-containing functional groups presented as C=O/O-C-O, C-O, and COO- within the structure along with pyridine and pyrrolic structures. Consequently, the molecular structure comprises pentacene with aliphatic carbon chains, such as methylene, that connect the benzene rings and form a three-dimensional network. The results of a simulated IR spectrum and contact angle simulation aligned with the experimental results, validating the molecular structure of high-ash coal. The chemical formula for the high-ash coal model was determined as C203H189N7O61S with a molecular weight of 3734.79.

Recycling of valuable metals from spent lithium-ion batteries by self-supplied reductant roasting.

The massive spent lithium-ion batteries (LIBs) need to be recycled due to their increasing decommission in recent years. This paper aims to propose an effective process that uses self-supplied reductant roasting and acid leaching to recover Lithium, Nickle, Cobalt and Manganese from spent LIBs. In the absence of external carbon resources, the waste membrane from spent LIBs was used as the reductant in the self-supplied reductant roasting. A thermodynamic analysis was conducted to judge the possible reduction reaction between the cathode material and waste membrane. Then, the effects of roasting temperature, roasting time and membrane dosage on the crystal structure and phase transformation of roasting products were investigated and optimized. After the roasting process, the valence state of metals in the cathode material decreased and the structure became loose and porous. Moreover, the layer structure of the cathode material was transformed into groups of Li2CO3, Ni, Co, NiO, CoO and MnO. Further, the reduction effect of cathode powders under each roasting condition was verified under the same leaching conditions. After leaching for 30 min, the leaching efficiencies of Li, Ni, Co and Mn were over 99% under the optimum roasting conditions. Finally, economic assessments proved that the proposed process is profitable. The whole process demonstrates an effective and positive way for recycling spent LIBs and making full use of their waste membrane, which promotes resource recovery and environmental protection.

Hydrometallurgical enhanced liberation and recovery of anode material from spent lithium-ion batteries.

The efficient recycling of spent anode material (SAM) from spent lithium-ion batteries (LIBs) is generally critical in terms of electronic waste recyclingas well as increasing resource shortage and environmental problems. This research reported a novel and green method to recycle lithium, copper foil, and graphite from SAM by water leaching treatment. The results indicated that 100% of graphite was exfoliated from the anode material and 92.82% leaching efficiency of lithium was obtained under the optimal conditions of 80 °C, 60 g/L, 300 rpm, and 60 min, respectively. This finding revealed that the SAM got a full liberation characteristic due to the removal of binder, which produced an ideal leaching lithium efficiency rivaling the acids' performance. The mechanism of the liberation of SAM and lithium leaching is presented based on the analysis of results. The graphite was purified and recovered after water leaching treatment. Besides, lithium was recovered in the form of lithium carbonate (Li2CO3), and the copper foil was recovered in a sheet. This study endeavors to develop an economical and environmentally feasible plan to recycle graphite, copper, and lithium from SAM.

Separation of the cathode materials from the Al foil in spent lithium-ion batteries by cryogenic grinding.

An environmentally friendly technology of cryogenic grinding for recovering cathode materials from spent lithium-ion batteries was has been investigated in this paper. Differential Scanning Calorimeter was used to test the glass transition temperature of the organic binder. Advanced analysis techniques, a microcomputer-controlled electronic universal material-testing machine, a low-temperature impact testing machine, scanning electron microscopy and high-resolution 3 Dimension-X-ray microscopy, were utilized to analyze the effect of low temperature on the mechanical properties and morphology of cathode. Results show that the yield strength, tensile strength and impact strength of the current collector is significantly increased at low temperature, that the glass transition temperature of the organic binder is approximately 235 K. Low temperature enhances the strength of the current collector and causes the organic binder to fail. Therefore, cryogenic grinding could realize the selective grinding of the cathode and significantly improve the peel-off of the electrode materials. The peel-off efficiency of cathode materials was improved from 25.03% to 87.29% at the optimum conditions of low temperature pretreatment for 5 min and cryogenic grinding for 30 s. The experiments demonstrate that the cryogenic grinding can obviously facilitate the efficient recovery of cathode materials, revealing a great application prospective for the recycling of spent lithium-ion batteries.

Enhancement in leaching process of lithium and cobalt from spent lithium-ion batteries using benzenesulfonic acid system.

Recycling of valuable metals from spent lithium ion batteries (LIBs) is of great significance considering the conservation of metal resources and the alleviation of potential hazardous effects on environment. Thus, the present work focuses on enhancing the efficiency of leaching process for the recovery of cobalt and lithium from the cathode active materials of spent LIBs. In this study, benzenesulfonic acid (C6H5SO3H) with a reducing agent hydrogen peroxide (H2O2) was innovatively used as leaching reagents, and the operating variables were optimized to obtain higher leaching efficiencies. Results show the optimized leaching recovery of 99.58% Li and 96.53% Co was obtained under the conditions of 0.75 M benzenesulfonic acid, 3 vol% H2O2, a solid to liquid (S/L) ratio of 15 g/L, 500 rpm stirring speed, and 80 min leaching time at 90 °C. Moreover, a new kinetic model was introduced to describe the leaching kinetics of LiCoO2 from the cathode material. The apparent activation energies Ea for leaching of lithium and cobalt are 41.06 and 35.21 kJ/mol, respectively, indicating that the surface chemical reaction is the rate-controlling step during this leaching process. Further, the proposed recovery mechanism for spent cathode material was raised by analyzing the experimental results and characterizing the morphological and chemical state (i.e. SEM-EDS, XPS and XRD) of raw material and leaching residues. In comparison with the previous leaching process, this research was found to be efficient, low energy consumption, and environmental friendly.