Highly conductive LiMn0.6Fe0.4PO4 synthesized with styrene maleic anhydride-assisted glucose and polyvinyl alcohol carbon coating

The low conductivity and Li⁺ diffusion coefficient of lithium manganese iron phosphate (LMFP) hinder its practical applications. In this study, polyvinyl alcohol (PVA) to partially replace glucose in the LMFP coating, with styrene-maleic anhydride copolymer (SMA) auxiliary carbon source, was added for the coating. Following the addition of SMA, the alternating distribution of hydrophilic and hydrophobic groups within the molecular structure of SMA effectively prevents the aggregation between particles. The agglomeration of primary particles in the sample has been significantly minimized, and the viscosity of the slurry has been effectively decreased. Under the synergistic effect of PVA and SMA, the resulting carbon layer has a high degree of graphitization, the compaction density of the material is improved, and the diffusion coefficient of Li⁺ is improved due to the uniform and moderate thickness of the carbon layer. The properties of the modified samples exhibit varying degrees of enhancement. The discharge specific capacity of LPS-4 was 156.8 mA h g⁻¹ at 0.2 C, and the capacity retention rate was 96.4% after 100 cycles at 1 C. In addition to the improvement of these properties, the powder conductivity of the material has also significantly increased. At a pressure of 350 MPa, the conductivity can attain a value of 3.25 × 10⁻² S cm⁻¹.