Hydrometallurgical Recovery Methods for LFP Batteries involve the use of strong acids to dissolve the cathode sheets, followed by the addition of alkalis to precipitate lithium, iron ions, and phosphate ions out of solution. These precipitates are then adjusted according to the desired recovery ratio and calcined at high temperatures to regenerate LFP.
Here are Two detailed approaches to hydrometallurgical recycling of spent LFP batteries:
1. Hydrometallurgical Recycling Overview: Primarily utilizing acid and alkali solutions to dissolve metal ions from LFP batteries, this method further employs precipitation or adsorption techniques to extract dissolved metal ions in the form of oxides or salts. Reagents commonly used include sulfuric acid (H2SO4), sodium hydroxide (NaOH), and hydrogen peroxide (H2O2). Hydrometallurgical recycling is straightforward, requires minimal equipment, making it suitable for industrial-scale production, and is the most researched and widely adopted route for recycling lithium-ion batteries.
2. Cathode Recovery Focus: Hydrometallurgical recycling of LFP batteries primarily targets the recovery of the cathode. To recycle the LFP cathode, the first step involves separating the aluminum current collector from the active cathode material.
(1) One method involves dissolving the current collector in an alkaline solution while the active material remains unaffected, allowing it to be isolated via filtration.
(2) Another approach uses organic solvents to dissolve the polyvinylidene fluoride (PVDF) binder, enabling the LFP cathode material to separate from the aluminum foil. The foil can then be reused, and the active material can proceed to further processing. The organic solvent can be distilled for reuse, promoting a more environmentally friendly and safer process.
(3) Comparatively, the second method is more environmentally friendly and safe. A common method for recycling LFP is to produce lithium carbonate; this method is cost-effective and widely adopted by many LFP recycling companies, but it fails to recover the main component, iron phosphate (comprising about 95% of the cathode), leading to wasted resources.
(4) A more desirable hydrometallurgical recycling method transforms spent LFP cathode material into lithium salts and iron phosphate, achieving full recovery of Li, Fe, and P elements. Transforming LFP into lithium salts and iron phosphate requires oxidizing ferrous iron to ferric iron, typically achieved through acid leaching or alkali leaching to extract lithium. Researchers have developed a process involving oxidative roasting to separate aluminum foil and LFP, followed by sulfuric acid leaching and solid-liquid separation to obtain crude iron phosphate. Impurities are removed from the solution using sodium carbonate to precipitate lithium carbonate. The filtrate is evaporated and crystallized to produce anhydrous sodium sulfate as a by-product for sale. Crude iron phosphate is further refined into battery-grade iron phosphate, which can be used in the production of new LFP materials. This process, after years of research, has become relatively mature.
