Disassembly and recovery of lithium iron phosphate battery

The retired lithium iron phosphate battery that does not have the value of cascade utilization and the batteries after cascade utilization will finally enter the stage of disassembly and recovery. The difference between lithium iron phosphate battery and ternary material battery is that it does not contain heavy metals, and the recovery is mainly Li, P and Fe. The added value of the recovered products is low, so a low-cost recovery route needs to be developed. There are mainly two recycling methods: fire method and wet method.
Fire recovery process
The traditional fire recovery method generally involves high-temperature incineration of electrode pieces, which burns the carbon and organic matter in the electrode fragments. The remaining ash that cannot be burned is ultimately screened to obtain fine powder materials containing metals and metal oxides. The process of this method is simple, but the treatment process is long and the comprehensive recovery rate of valuable metals is low. The improved pyrometallurgical recovery technology involves removing organic binders through calcination, separating lithium iron phosphate powder from aluminum foil to obtain lithium iron phosphate material. Then, an appropriate amount of raw material is added to obtain the required molar ratio of lithium, iron, and phosphorus, and a new lithium iron phosphate is synthesized through high-temperature solid-state method. According to cost estimation, the improved pyrometallurgical dry recycling of waste lithium iron phosphate batteries can achieve profitability, but the newly prepared lithium iron phosphate using this recycling process has many impurities and unstable performance.
Wet recovery process
Wet recovery is mainly to dissolve the metal ions in lithium iron phosphate battery through acid and alkali solutions, and further extract the dissolved metal ions in the form of oxides, salts, etc. by precipitation, adsorption, etc. The reaction process mostly uses H2SO4, NaOH, H2O2 and other reagents. The wet recovery process is simple, with low equipment requirements, and is suitable for industrial scale production. It is the most studied by scholars and also the mainstream treatment route for waste lithium-ion batteries in China.
The wet recovery of lithium iron phosphate battery mainly depends on the recovery of positive electrode. When using a wet process to recover lithium iron phosphate cathode, the first step is to separate the aluminum foil collector from the active substance of the cathode. One method is to use alkaline solution to dissolve and collect the fluid, while the active substance does not react with the alkaline solution and can be obtained through filtration. The second method is to dissolve the binder PVDF with an organic solvent to separate the lithium iron phosphate cathode material from the aluminum foil. The aluminum foil is reused, and the active substance can be further treated. The organic solvent can be distilled to achieve its recycling. Compared to the two methods, the second method is more environmentally friendly and safe. One way to recover lithium iron phosphate from the positive electrode is to generate lithium carbonate. This recycling method has a lower cost and is adopted by most lithium iron phosphate recycling enterprises, but the main component of lithium iron phosphate, iron phosphate (with a content of 95%), is not recycled, resulting in resource waste.
The ideal wet recovery method is to convert waste lithium ferrous phosphate cathode materials into lithium salts and iron phosphate, achieving full element recovery of Li, Fe, and P. To convert lithium ferrous phosphate into lithium salts and iron phosphate, ferrous oxide needs to be oxidized to trivalent iron, and lithium is leached by acid or alkali leaching. Some scholars use oxidation calcination to separate aluminum sheets and lithium iron phosphate, which are then leached and separated by sulfuric acid to obtain crude iron phosphate. The solution is then precipitated into lithium carbonate using sodium carbonate for impurity removal; The filtrate is evaporated and crystallized to obtain anhydrous sodium sulfate product, which is sold as a byproduct; Crude iron phosphate is further refined to obtain battery grade iron phosphate, which can be used for the preparation of lithium iron phosphate materials. This process has been going on for many years