LifePo4 Battery Recycling Solution Progress and Setbacks

Retired lithium iron phosphate batteries that do not have value for secondary use and those that have undergone secondary use must eventually enter the disassembly and recycling stage. Unlike ternary material batteries, lithium iron phosphate batteries do not contain heavy metals. The main components for recovery are Li, P, and Fe, and the added value of the recovered products is low, necessitating the development of low-cost recycling routes. There are mainly two recycling methods: pyrometallurgical and hydrometallurgical.

Traditional pyrometallurgical recycling generally involves high-temperature incineration of electrode sheets to burn off the carbon and organic matter in the electrode fragments. The remaining ash, which cannot be burned off, is ultimately obtained through screening and contains metal and metal oxides in a fine powder form. This method is simple but has a long processing time, and the comprehensive recovery rate of valuable metals is low. An improved pyrometallurgical recycling technology involves calcining to remove organic binders, separating lithium iron phosphate powder from aluminum foil, obtaining the lithium iron phosphate material, and then adding the appropriate raw materials to achieve the required molar ratio of lithium, iron, and phosphorus, and synthesizing new lithium iron phosphate through high-temperature solid-phase methods. According to cost estimates, improved pyrometallurgical dry recycling of waste lithium iron phosphate batteries can be profitable. However, the lithium iron phosphate produced by this recycling process has high impurity levels and unstable performance.

Hydrometallurgical recycling mainly involves dissolving the metal ions in lithium iron phosphate batteries in acid-base solutions and then extracting the dissolved metal ions in the form of oxides, salts, and other compounds using precipitation and adsorption methods. The reaction process often uses reagents such as H2SO4, NaOH, and H2O2. This method is simple, requires low equipment demands, and is suitable for industrial-scale production. It is the most researched method and the mainstream route for the treatment of waste lithium-ion batteries in China.

In the hydrometallurgical recycling of lithium iron phosphate batteries, the focus is on recovering the positive electrode. When using the wet process to recover lithium iron phosphate positive electrodes, the aluminum foil collector fluid is separated from the positive electrode active material. One method involves using an alkaline solution to dissolve the collector fluid, while the active material does not react with the alkaline solution and can be obtained through filtration. Another method involves using an organic solvent to dissolve the binder PVDF, separating the lithium iron phosphate positive electrode material from the aluminum foil, and reusing the aluminum foil. The active material can then undergo subsequent processing, and the organic solvent can be recycled through distillation for reuse. Of the two methods, the second is more environmentally friendly and safe. One method for recovering lithium iron phosphate from the positive electrode is to produce lithium carbonate. This low-cost recovery method is adopted by most waste lithium iron phosphate recycling companies, but the main component of lithium iron phosphate, iron phosphate (with a content of 95%), is not recovered, leading to resource waste.

An ideal hydrometallurgical recycling method involves converting waste lithium iron phosphate positive electrode materials into lithium salt and iron phosphate to achieve full elemental recovery of Li, Fe, and P. To transform lithium iron phosphate into lithium salt and iron phosphate, the ferrous iron must be oxidized to ferric iron, and the lithium must be leached using acid or alkali. Researchers have used oxidation and calcination to separate aluminum foil and lithium iron phosphate, followed by sulfuric acid leaching and separation to obtain crude iron phosphate. The solution is purified using sodium carbonate precipitation to obtain lithium carbonate. The crude iron phosphate is further refined to obtain battery-grade iron phosphate, which can be used in the preparation of lithium iron phosphate materials. After years of research, this process has become relatively mature.