Synergistic Optimization of LiMn0.6Fe0.4PO4 Kinetics Property and Structural Stability via Molecular Chelating Action and Ni-Doping Strategy to Improve Electrochemical Performance

LiMn1–xFexPO4 (LMFP) is an olivine-type material with great application potential, which inherits both the advantages and disadvantages of LiFePO4 (LFP) and LiMnPO4 (LMP). Nevertheless, the poor electrochemical kinetics and low structural stability hinder its widespread application. Drawing inspiration from the chelating ability of tartaric acid toward metal ions, we herein regulate LMFP into nanoparticles with uniform carbon coating via a simple ball-milling-assisted solid-phase sintering method. This strategy is validated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results. Furthermore, Rietveld refinement of X-ray diffraction (XRD) data combined with crystal orbital Hamilton population (COHP) analysis reveals that Ni doping facilitates lithium-ion diffusion, while reinforcing the structural stability of LMFP. The proposed dual modification strategy concurrently enhances the electronic conductivity and the ionic diffusion by factors of 10.22 and 4.26, respectively. Consequently, the optimized LMFP/TNi-2 cathode delivers outstanding electrochemical performance, manifesting a high reversible capacity of 161.8 mAh/g at 0.1 C and retaining 91.97% of its initial capacity after 1000 cycles at a charge–discharge rate of 1 C. Collectively, this synergistic modification strategy offers a scalable route toward the industrial implementation of olivine-type LMFP cathode materials.