Construction of an Electric Field Based on Mn Gradient Coating for Inhibiting Lattice Mismatch in LMFP during Charge–Discharge Processes

Lithium manganese iron phosphate (LMFP) has emerged as a promising stable and safe cathode material for power batteries and energy storage systems, succeeding the widely commercialized lithium iron phosphate (LFP). However, its practical deployment is hindered by the intrinsic Jahn–Teller effect and sluggish lithium-ion diffusion kinetics. Herein, we design a core–shell precursor with a manganese concentration gradient to fabricate Al3+-doped LMFP with a β-LiAlO2 coating layer. X-ray diffraction (XRD) and cyclic voltammetry (CV) characterizations confirm that the microelectric field induced by the manganese gradient suppresses the Jahn–Teller distortion, while the Al(LMFP)–O–Al(β-LiAlO2) interfacial structure accelerates lithium-ion diffusion. The optimized material with 2 mol % Al3+ doping and 10 mol % β-LiAlO2 coating delivers a superior specific capacity of 115.4 mAh·g–1 at 10 C, with an ultrahigh capacity retention of 99.5% after 500 cycles, markedly outperforming previously reported LMFP cathodes (typically ∼90 mAh·g–1 at 10 C and ∼90% retention after 500 cycles). Notably, this Al-based modification strategy is directly applicable to recycling Al-containing spent LFP black mass, and the recycled LMFP delivers 127.98 mAh·g–1 at 10 C with 92% capacity retention after 150 cycles. This work provides a facile, scalable technical route for both high-performance LMFP fabrication and sustainable recycling of Al-containing LFP battery wastes.