Structure-Selective Regeneration of Heterogeneously Degraded LiFePO_<b>4</b> via Spontaneous Lithiation and Defect Reconstruction.

Abstract

Most current regeneration methods are predicated on the assumption of uniform degradation, making them inadequate to precisely address the structural disparities and defect heterogeneity among particles, thereby limiting their applicability for large-scale regeneration of industrial LiFePO₄ black mass. In this work, we propose a scalable and simplified solid-liquid hybrid strategy that enables efficient regeneration of kilogram-scale, heterogeneously degraded LiFePO₄ cathodes at room temperature under laboratory conditions. The approach leverages localized interfacial redox processes at room temperature to achieve precise lithium compensation at the particle level. However, atomic-resolution analyses reveal that lithium replenishment alone is insufficient to repair Fe/Li antisite defects within the crystal lattice, particularly in mildly delithiated particles (<5%), where the migration energy barrier reaches 2.78 eV, thus impeding deep structural recovery. To overcome this limitation, a subsequent thermal activation step is incorporated to eliminate deep-seated antisite defects and enable complete lattice reconstruction. This combined approach leads to multiscale structural recovery, allowing the regenerated material to achieve a reversible specific capacity of 114.2 mA h g^-1 at 10.0 C and retain 79.2% of its capacity after 1500 cycles. These findings validate the method's wide applicability to structurally complex degradation scenarios and offer mechanistic and practical insights into scalable regeneration of high-performance electrodes.