Constructing a Three-Phase Reaction System for Efficiently Recycling Spent LiFePO₄

In recent years, a large number of spent lithium iron phosphate (LiFePO 4, abbreviated as LFP) batteries have been retired. Selective leaching is the most suitable recycling option for spent LFP (S-LFP). However, the current mainstream oxidants and acids are not economical, safe, and green. Herein, we constructed a HNO 3 -O 2 system to achieve efficient leaching of Li from S-LFP. HNO 3 can be recovered by high temperatures after use to achieve the recycling of acid, and O 2 is more economical and safer than mainstream oxidants. In the comfortable oxidizing environment provided by HNO 3, O 2 is used to oxidize Fe 2+ in S-LFP into Fe 3+, and Li + is extracted from S-LFP into the solution with a leaching rate of almost 100%. The lithium-rich solution is further used to leach the Li from the spent graphite anode, and then the Li in the solution is captured using CO 2 to obtain Li 2 CO 3 . The iron phosphate (FePO 4 ) slag from Li extraction is regenerated into LFP based on the above obtained Li 2 CO 3 through carbon thermal reduction. The regenerated LFP displays a high discharge capacity of 163.85 mAh g –1 and a stable cycling performance, which are comparable to those of commercial LFP.