Facile separation and regeneration of LiFePO4 from spent lithium-ion batteries via effective pyrolysis and flotation: An economical and eco-friendly approach

Mixed crushing and competitive leaching of all electrode material components and metal collector fluid in the spent lithium battery

Hydrometallurgy is a primary method for recovering cathode electrode materials from spent lithium-ion batteries (LIBs). Most of the current research materials are pure cathode electrode materials obtained through manual disassembly. However, the spent LIBs are typically broken as a whole during the actual industrial recycling which makes the electrode materials combined with the collector fluid. Therefore, the competitive leaching between metal collector fluid and electrode material was examined. The pyrolysis characteristics of the electrode materials were analyzed to determine the pyrolysis temperature. The electrode sheet was pyrolyzed and then crushed for competitive leaching. The effect of pyrolysis was analyzed by XPS. The competitive leaching behavior was studied based on leaching agent concentration, leaching time and leaching temperature. The composition and morphology of the residue were determined to prove the competitive leaching results by XRD-SEM. TG results showed that 500 °C was the suitable pyrolysis temperature. XPS analysis demonstrated that pyrolysis can completely remove PVDF. Li and Co were preferentially leached during the competitive leaching while the leaching rates were 90.10% and 93.40% with 50 min leaching at 70 °C. The Al and Cu had weak competitive leachability and the leaching rate was 29.10% and 0.00%. XRD-SEM analysis showed that Li and Co can be fully leached with residual Al and Cu remaining. The results showed that the mixed leaching of electrode materials is feasible based on its excellent selective leaching properties.

Aggregating fine hydrophilic materials in froth flotation to improve separation efficiency through a homo-aggregation flotation process

As a versatile separation technology, froth flotation has gained extensive applications in both primary resource recovery and secondary resource recycling. It exploits differences in the water-wettability of solid surfaces to separate value components from wastes. Hydrophobic (water-repelling) particles attach to gas bubbles, float away from hydrophilic (water-loving) particles and become froth products. However, flotation separation deteriorates with low efficiency and low selectivity when treating fine (< circa 20 μm) and ultrafine (< circa 5 μm) particles. Particularly, fine hydrophilic particles affect value mineral recovery and froth product grade by attaching indiscriminately to value minerals, increasing pulp viscosity, and entering froth products by entrainment. Many mitigation measures have been proposed in the literature to target the fine hydrophilic particles in the flotation process, mainly from physical/mechanical perspective. Notably, recent investigations suggest that selectively aggregating fine hydrophilic particles could reduce their entrainment to froth products and increase froth product grade. In this review, we first analyze the adverse effects of fine hydrophilic particles on froth flotation and summarize current mitigation methods. Following the review, a homo-aggregation flotation (HAF) concept different from conventional approaches is proposed to improve the separation efficiency of fine particles in froth flotation. We present case studies highlighting the necessity of aggregating fine hydrophilic materials to improve separation efficiency in froth flotation, noting that hydrophobic aggregation is a natural process in water.

The Recycling of Spent Lithium-Ion Batteries: Crucial Flotation for the Separation of Cathode and Anode Materials

The recycling of spent lithium-ion batteries (LIBs) has attracted great attention, mainly because of its significant impact on resource recycling and environmental protection. Currently, the processes involved in recovering valuable metals from spent LIBs have shown remarkable progress, but little attention has been paid to the effective separation of spent cathode and anode materials. Significantly, it not only can reduce the difficulty in the subsequent processing of spent cathode materials, but also contribute to the recovery of graphite. Considering the difference in their chemical properties on the surface, flotation is an effective method to separate materials, owing to its low-cost and eco-friendly characteristics. In this paper, the chemical principles of flotation separation for spent cathodes and materials from spent LIBs is summarized first. Then, the research progress in flotation separation of various spent cathode materials (LiCoO₂, LiNi_xCo_yMn_zO₂, and LiFePO₄) and graphite is summarized. Given this, the work is expected to offer the significant reviews and insights about the flotation separation for high-value recycling of spent LIBs.

Ultra-fast recovery of cathode materials from spent LiFePO4 lithium-ion batteries by novel electromagnetic separation technology

The separation of electrode materials from current collectors plays a significant role in determining the leaching efficiency of different metals from spent lithium-ion batteries (LIBs). In the presented research, a highly efficient, environmentally sustainable, and cost-effective cathode materials separation strategy was proposed for spent LiFePO₄ batteries. Based on the difference in the thermal expansion coefficient of the binder and aluminum foil, the electromagnetic induction system was examined to harvest cathode materials for the first time, which could provide a high heating rate to erase the mechanical interlocking force between Al foil and coated material, and breaking the chemical bond or Van der Waals forces of the binder. The process avoids the usage of any chemicals such as acids and alkalis, thus eliminating the emission of wastewater. Our system shows ultra-fast separation (3 min) and achieves high-purity of recovered electrode materials and Al foils (99.6% and 99.2%). Furthermore, the morphology and crystalline structure of delaminated electrode materials remain almost the same compared with the pristine materials, which provides a previously unexplored technology to realize sustainable spent battery recycling.