Long‐Life Regenerated LiFePO₄ from Spent Cathode by Elevating the d‐Band Center of Fe

Abstract

A large amount of spent LiFePO4 (LFP) has been produced in recent years because it is one of the most widely used cathode materials for electric vehicles. The traditional hydrometallurgical and pyrometallurgical recycling methods are doubted because of the economic and environmental benefits; the direct regeneration method is considered a promising way to recycle spent LFP. However, the performance of regenerated LFP by direct recycling is not ideal due to the migration of Fe ions during cycling and irreversible phase transition caused by sluggish Li+ diffusion. The key to addressing the challenge is to immobilize Fe atoms in the lattice and improve the Li+ migration capability during cycling. In this work, spent LFP is regenerated by using environmentally friendly ethanol, and its cycling stability is promoted by elevating the d‐band center of Fe atoms via construction of a heterogeneous interface between LFP and nitrogen‐doped carbon. The FeO bonding is strengthened and the migration of Fe ions during cycling is suppressed due to the elevated d‐band center. The Li+ diffusion kinetics in the regenerated LFP are improved, leading to an excellent reversibility of the phase transition. Therefore, the regenerated LFP exhibits an ultrastable cycling performance at a high rate of 10 C with ≈80% capacity retention after 1000 cycles.

Topotactic Transformation of Surface Structure Enabling Direct Regeneration of Spent Lithium-Ion Battery Cathodes

“…Then, the mixture was sintered at 500 °C for 2 h and finally calcined for 10 h at 850 °C under an air atmosphere with a heating rate of 5 °C/min to obtain the regenerated NCM523 cathode materials (RHSNCM523-12 mg, RHSNCM523, and RHSNCM523-24 mg). The specific conditions of hydrothermal treatment, the sintering process, and the amount of ammonium are selected based on the literature reports and our experience in regenerating cathode materials. , The amount of lithium hydroxide, calcination conditions, and the hydrothermal treatment time used in the regenerating process were optimized based on the experimental results (Figure S24). The RHSNCM523 cathode materials show optimal performance.…”

“…At present, the recycling of spent LIBs mainly includes pyrometallurgy and hydrometallurgy in industrial practice. , Pyrometallurgy mainly refers to the reduction of precious metals from spent batteries through high-temperature smelting, followed by the separation of the resulting metal alloys. Although its operation is simple, the high energy consumption and low recycling efficiency of Li indicate that it is not the most efficient way to recycle spent LIBs .…”

Direct regeneration of degraded lithium-ion battery cathodes with a multifunctional organic lithium salt

“…For S-LFP, the main peaks at 710.7 eV and 709.1 eV are respectively attributed to the Fe(III) and Fe(II) of Fe 2p 3/2 . The presence of Fe(II) is due to the inhomogeneity of phase distributions in S-LFP surface after long-term cycles 19,33 . Quantification of Fe(III)/Fe(II) was presented by the Fe 2p 3/2 peak fitting area ratio, suggesting that the main phase is FePO 4 on the surface of degraded LFP particles.…”

A Materials Perspective on Direct Recycling of Lithium‐Ion Batteries: Principles, Challenges and Opportunities

“…Mater. 2023, 33,2213168 Regeneration condition Performance 100 mg D-LFP+10 mg PVP+15 mg CH 3 COOLi+15 mL ethanol, hydrothermal at 180 °C for 5 h, Sintering at 700 °C for 5 h in Ar [56] 145.7 mAh g −1 at 1C, 85.2% capacity retention after 500 cycles 3 g D-LFP+30 mL 0.08 M tartaric acid+20 mL 0.2 M LiOH, hydrothermal at 200 °C for 3 h, sintering at 700 °C for 2h [57] 165.9 mAh g −1 at 0.1C, 99.1% capacity retention after 100 cycles LMO 0.25 g D-LMO+0.1 M LiOH, hydrothermal at 180 °C for 4 h [58] 111 mAh g −1 at 0.5C, ≈92.3% capacity retention after 100 cycles…”

“…Additionally, with the increment of the hydrothermal temperature from 120 °C to 200 °C, the capacity of the regenerated LFP could be improved from 135 to 139 mAh g −1 (Figure 3g). Cheng group [56] used ethanol as the both the realithiation medium and reducing agent, and CH 3 COOLi as Li source. Besides these chemicals, they added PVP in the solution to serve as a nitrogen source.…”