A Multifunctional Amino Acid Enables Direct Recycling of Spent LiFePO₄ Cathode Material

Abstract

Lithium iron phosphate (LiFePO4, LFP) batteries are extensively used in electric vehicles and energy storage due to their good cycling stability and safety. However, the finite service life of lithium‐ion batteries leads to significant amounts of retired LFP batteries, urgently required to be recycled by environmentally friendly and effective methods. Here, a direct regeneration strategy using natural and low‐cost L‐threonine as a multifunctional reductant is proposed. The hydroxyl groups and amino groups in L‐threonine act as electron donors and nitrogen sources, respectively. The reductive environment created by L‐threonine not only aids in converting the degraded FePO4 phase back to a single LFP phase but also facilitates the elimination of detrimental Li–Fe anti‐site defects; thus, reconstructing fast Li+ diffusion channels. Meanwhile, N atoms derived from amino groups are able to dope into carbon layers, generating more active sites and enhancing the conductive properties of LFP particles. The regenerated LFP shows great electrochemical performance with a discharge capacity of 147.9 mAh g−1 at 1 C and a capacity retention of 86% after 500 cycles at 5 C. Further, this approach is also feasible for LFP black mass sourced from practical industrial dismantling lines, providing considerable prospects for the large‐scale recycling of LFP batteries.

Nondisassembly Repair of Degraded LiFePO4 Cells via Lithium Restoration from the Solid Electrolyte Interphase

“…According to the Rietveld refinement results calculated from XRD, the defect value was reduced from 2.85 (Figure 2e; Table S2, Supporting Information) to 2.452% (Figure 2f; Table S3, Supporting Information). Reducing antisite defects is vital for improving Li + diffusion, 38 consistent with the lower charge voltage plateau exhibited by R-LFP, as shown in Figure 1c. C-LFP requires a higher overpotential to overcome the impediment due to defects obstructing Li + diffusion channels, while the extra electrons R-LFP gained from the anode side can reduce Fe 3+ , thereby leading to a decrease in the activation barrier of cation migration, thus reordering the transport channels for better Li + diffusion.…”

Direct Recycling Technology for Spent Lithium-Ion Batteries: Limitations of Current Implementation

“…The solution-based recovery method for LFP materials holds promise for restoring both Li losses and the formation of Fe-Li defects, particularly in cases of severe degradation and substantial capacity decay [53]. The revival of these defects is crucial for achieving complete material recovery and optimal performance.…”