Recycling method of waste lithium iron phosphate positive electrode material

Abstract

The invention relates to a recycling method of a waste lithium iron phosphate positive electrode material. The method comprises the following steps: adding phosphate into the waste lithium iron phosphate positive electrode material, then carrying out supercritical carbon dioxide extraction, and filtering to obtain a solid intermediate A; heating the solid intermediate A to obtain a solid intermediate B; and adding a polymer containing a benzene ring into the solid intermediate B, and calcining to obtain regenerated lithium iron phosphate. The method is simple in process, low in environmental pressure, low in manufacturing cost, good in atom economy, controllable in quality and easy to industrialize, and the final product is good in performance.

Description

technical field [0001] The invention relates to the technical field of battery material recycling, in particular to a method for recycling waste lithium iron phosphate cathode materials. Background technique [0002] Lithium iron phosphate is an important cathode material for lithium batteries. It has an orthorhombic olivine structure. Lithium ions can move and intercalate in the crystal, and has electrochemical activity. In a certain voltage range, the olivine structure of lithium iron phosphate is stable. It is not easy to transform into a spinel structure. The actual specific capacity of lithium iron phosphate can reach 140mAh / g, the discharge voltage is 2.0-4.0V, and the charge and discharge times can reach 2000 times. Compared with lithium-ion battery cathode materials such as lithium manganese oxide and ternary materials, lithium iron phosphate batteries have high safety performance and do not contain highly toxic heavy metal ions. In addition, lithium iron phosphate...

AI Technical Summary

Problems solved by technology

For example, patent CN104953200A discloses using acid solution to dissolve waste lithium iron phosphate powder, adding a surfactant to the acid solution after dissolving, adjusting the pH value, filtering the precipitate and obtaining battery grade iron phosphate, mixing iron phosphate with lithium carbonate and carbon source Lithium iron phosphate is obtained by calcining. This technical solution fails to fully recover the electrolyte remaining on the waste lithium iron phosphate electrode. At the same time, an acid solution is used to dissolve the waste lithium iron phosphate when preparing iron phosphate. This method still needs to use the waste iron phosphate Different metal elements in lithium materials are extracted and recovered separately. The recovery process is complicated, the process is long, the waste water discharge is large, the energy consumption is high, and the electrolyte cannot be recovered, which is easy to cause secondary pollution. It is difficult to purify and require a lot of equipment investment. The use of different acid systems will inevitably introduce impurities and bring new by-products

[0008] To sum up, in the current recycling methods of waste lithium iron phosphate materials, it is often necessary to re-extract and recover the metal after dissolving the waste lithium iron phosphate materials. The process is relatively complicated, and lithium iron phosphate with an olivine structure needs to be re-synthesized

Therefore, the existing recovery and regeneration methods are often costly, and the obtained lithium iron phosphate has a high impurity content, and the product quality and performance are uncontrollable