Wet recycling process of lithium iron phosphate battery

Wet recovery is mainly to dissolve metal ions in lithium iron phosphate batteries through acid-base solution, and further use precipitation, adsorption and other methods to extract the dissolved metal ions in the form of oxides and salts. Most of the reaction process uses H2SO4, NaOH and Reagents such as H2O2. The wet recycling process is simple, the equipment requirements are not high, and it is suitable for industrial scale production. It is the most studied by scholars and is also the mainstream domestic waste lithium-ion battery treatment route.
The wet recycling of lithium iron phosphate batteries is mainly to recover the cathode. When the lithium iron phosphate cathode is recycled by a wet process, the aluminum foil current collector must be separated from the cathode active material first. One of the methods is to use lye to dissolve the current collector, and the active substance does not react with the lye, and the active substance can be obtained by filtration. The second method is to dissolve the binder PVDF with an organic solvent, so that the lithium iron phosphate cathode material is separated from the aluminum foil, and the aluminum foil can be reused. The active material can be processed later, and the organic solvent can be distilled to realize its recycling. Compared with the two methods, the second one is more environmentally friendly and safe. The recovery of lithium iron phosphate in the positive electrode is to generate lithium carbonate. This recycling method is low in cost and has been adopted by most lithium iron phosphate recycling companies, but the main component of lithium iron phosphate, iron phosphate (content 95%), has not been recycled, resulting in a waste of resources.
The ideal wet recovery method is to convert the waste lithium iron phosphate cathode material into lithium salt and iron phosphate, so as to realize the full element recovery of Li, Fe, and P. In order to turn lithium ferrous phosphate into lithium salt and ferric phosphate, ferrous iron needs to be oxidized to ferric iron, and lithium is leached out by acid leaching or alkali leaching. Some scholars use oxidative calcination to separate aluminum flakes and lithium iron phosphate, and then leaching and separating with sulfuric acid to obtain crude iron phosphate, and then use sodium carbonate to precipitate lithium carbonate for impurity removal from the solution; the filtrate is evaporated and crystallized to obtain anhydrous sodium sulfate product as a by-product for sale; 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. The process has been relatively mature after years of research.