Process Flow for Lithium Extraction from Spent Lithium Batteries Using Mixer-Settlers

With the large-scale retirement of new energy power batteries, the stock of spent lithium batteries is increasing year by year. The recycling and reuse of lithium resources has become a core link in the sustainable development of the new energy industry. Primary lithium ore mining is characterized by high costs and limited resource reserves, while spent lithium batteries contain high concentrations of lithium, making them a highly valuable secondary lithium resource. Traditional lithium extraction processes for lithium batteries have drawbacks such as low recovery rates, difficulty in impurity separation, high equipment operation costs, and heavy environmental loads, which make it hard to meet the industry’s demand for large-scale and green development. The solvent extraction lithium extraction technology based on mixer-settlers has become the mainstream practical technology in the hydrometallurgical recovery field of spent lithium batteries, thanks to its advantages of continuous operation, stable separation effect, controllable energy consumption, and adaptability to industrial mass production. It can efficiently complete the enrichment and purification of lithium, providing reliable technical support for the development of the lithium battery circular economy.

1. Pretreatment Process of Spent Lithium Batteries

Before spent lithium batteries enter the lithium extraction stage, systematic pretreatment is required to break the battery packaging structure and achieve homogeneous material treatment, laying the foundation for subsequent solvent extraction. First, discharge and disassembly are carried out: residual electricity is released through brine immersion to avoid safety hazards during the disassembly process. Then, components such as the shell, diaphragm, and electrode materials are disassembled to separate the core active materials of the positive and negative electrodes. Next, the electrode materials are processed into uniform powder through crushing and screening processes to remove irrelevant impurities such as plastics, copper foil, and aluminum foil. Finally, acid leaching is adopted: inorganic leaching agents are used to dissolve the powder, allowing lithium, cobalt, nickel, manganese, and other metal elements to enter the leachate simultaneously, forming a stable mixed feed solution. Suspended solid residues are removed to ensure the cleanliness of the feed solution, which is then transported to the extraction process.

2. Core Process of Multi-Stage Solvent Extraction for Lithium Using Mixer-Settlers

As the core reaction equipment for hydrometallurgical lithium extraction, mixer-settlers achieve precise separation of lithium from other metal impurities through their stable mixing and clarification zone structure, serving as a key link in the entire process. According to the composition characteristics of the feed solution, a highly adaptable selective extraction solvent is selected, combined with diluents and regulators to prepare the organic extraction phase, ensuring its specific binding capacity for lithium ions. The pretreated lithium battery leachate and the prepared organic phase are continuously injected into the mixer-settler at a fixed ratio. Through the built-in stirring mechanism of the equipment, the aqueous feed solution and the organic phase are fully contacted and mixed. Under the set process conditions of temperature, pH value, and mixing time, lithium ions are selectively transferred to the organic phase, while impurity metals such as cobalt, nickel, manganese, and iron remain in the aqueous raffinate. Relying on the built-in clarification and separation zone of the mixer-settler, rapid phase separation is completed, effectively avoiding material mixing. In industrial production, a multi-stage countercurrent extraction mode is mostly adopted: multiple mixer-settlers are connected in series to greatly improve the lithium extraction and enrichment ratio, reduce impurity entrainment, and continuously enhance the lithium recovery efficiency.

3. Stripping and Enrichment Process of Loaded Organic Phase

After extraction, the loaded organic phase containing high concentrations of lithium needs to enter the stripping stage to complete the desorption and enrichment of lithium, obtaining high-purity lithium solution. The loaded organic phase is transported to the secondary operation unit of the mixer-settler, and a special stripping agent is added as the aqueous stripping system. In the controllable mixing environment of the mixer-settler, the binding state between lithium ions and the extraction solvent is broken, allowing lithium ions to be transferred from the organic phase back to the aqueous phase. Key parameters such as stripping agent concentration, phase flow ratio, and reaction residence time are strictly controlled to ensure the full progress of the stripping reaction. After clarification and phase separation in the mixer-settler, the stripping solution rich in lithium ions is separated, with significantly increased lithium concentration and reduced impurity content. The blank organic phase after desorption can be recycled for reuse after simple adjustment, continuously participating in the extraction process, reducing reagent consumption, and lowering the overall production material cost.

4. Lithium Solution Purification and Finished Product Preparation

The crude lithium solution obtained from stripping still contains trace residual impurities, which need further purification to meet the production standards of industrial-grade lithium salt products. By adjusting the pH value of the lithium solution, combined with precipitation and filtration processes, residual heavy metals and non-metallic impurities are removed, obtaining a refined high-purity lithium solution. Subsequently, according to market demand, processes such as concentration crystallization and precipitation conversion are adopted to prepare mainstream lithium battery raw materials such as lithium carbonate and lithium hydroxide. The finished products are put on the market after drying, sieving, and packaging, realizing secondary resource utilization. The treated production tail liquid is discharged in compliance with standards or recycled after environmental purification treatment, enabling the entire process to achieve efficient resource utilization and green production.

5. Application Advantages of Lithium Extraction Process Using Mixer-Settlers

Compared with traditional precipitation methods and single extraction equipment lithium extraction modes, the mixer-settler solvent extraction lithium extraction process is more suitable for the industrial scenario of spent lithium battery recycling. The equipment can achieve 24-hour continuous stable operation with large processing capacity and easy adjustment of process parameters, making it suitable for flexible configuration of small-to-large lithium battery recycling production lines. The mixer-settler has a reasonable structural design, with sufficient mixing reaction and fast phase separation speed. The comprehensive lithium recovery rate remains stably high, and the product quality is uniform and controllable. At the same time, the process reagents can be recycled, the total amount of three wastes (waste gas, waste water, solid waste) emissions is small, and the operation energy consumption is low, which can effectively control the enterprise’s production and operation costs. The overall process flow is simple and smooth, with convenient operation and maintenance and high safety factor, meeting the dual industry requirements of environmental protection production and resource recycling.

6. Process Development and Industry Application Prospects

Driven by the dual carbon policy, the standardization level of the new energy battery recycling industry is constantly improving, and the market demand for efficient, low-cost, and low-pollution lithium extraction processes is continuously rising. With mature industrial application experience, the mixer-settler solvent extraction lithium extraction technology is constantly optimized and upgraded by combining new extraction reagents and intelligent control systems. By improving the internal structure of the mixer-settler and optimizing the process formula, the selective separation effect of lithium can be further improved, the production cycle can be shortened, and the adaptability to various types of materials such as spent ternary lithium batteries and lithium iron phosphate batteries can be expanded. In the future, with continuous technological iteration, the mixer-settler hydrometallurgical lithium extraction process will be widely popularized in the lithium battery recycling industry, effectively alleviating the supply and demand pressure of lithium resources and helping the green, low-carbon, and high-quality development of the entire new energy industry chain.

Conclusion

The mixer-settler solvent extraction process for lithium from spent lithium batteries takes pretreatment, multi-stage extraction, stripping and enrichment, and refined product preparation as the complete link. Relying on the stable performance of the mixer-settler as the core equipment, it solves the industry pain points of low efficiency, difficult impurity separation, and high cost of traditional lithium extraction processes. The entire process is mature in technology, green and environmentally friendly, and highly adaptable to industrialization. It can not only efficiently recover lithium resources from spent lithium batteries but also realize reasonable control of production energy consumption and pollutant emissions. Under the general trend of new energy resource recycling, the mixer-settler solvent extraction technology will continue to be optimized and upgraded, becoming the core mainstream process for the resource recycling of spent lithium batteries, and providing solid technical support for the closed-loop development of the lithium battery industry.