Interfacial‐Electronegativity‐Induced Near‐Surface Tetrahedral Reconstruction Enables One‐Step Upcycling of Spent LiFePO ₄ for High‐Rate and Long‐Life Pouch Cells

Abstract

ABSTRACT Direct upcycling of spent lithium iron phosphate (S‐LFP) into high‐rate cathodes is highly desirable yet remains challenging. While conventional solid‐state sintering can repair bulk lattice defects, it is intrinsically limited in reconstructing localized near‐surface tetrahedral distortions, which critically impede 1D [010] Li + diffusion under high‐rate conditions. Herein, we propose a novel electronegative‐heterointerface‐enhanced solid‐state sintering for one‐step upcycling S‐LFP into high‐rate pouch‐cell cathodes. In this approach, S‐LFP nanoparticles are in situ encapsulated by highly electronegative heterointerfaces through temperature‐controlled solid‐state sintering, which finely modulates Fe d‐band/O p‐band hybridization, engineers O 1 ─O 2 ─O 3 ─O 3 tetrahedra, and accelerates Li + near‐surface migration. Consequently, regenerated LFP exhibits record‐high rate capability (125.0 and 70.0 mA h g −1 at 5 C and 30 C, respectively) and superior cycling stability (91.2% after 400 cycles at 5 C), significantly outperforming both conventional sintering paradigms and commercial counterparts by ∼100% at high rates. Moreover, regenerated Ah‐level pouch cells retain 82.9% of their 1 C capacity at 5 C and deliver 88.0% capacity retention even after 1000 cycles, simultaneously achieving high power and energy densities that surpass those of commercial LFP (C‐LFP) and demonstrating strong practical viability by successfully powering unmanned aerial vehicles. This work elucidates the fundamental correlation between electronegative heterointerfaces and tetrahedral framework for high‐rate LFP.