Abstract:

LiMn _x Fe_1-x PO₄ (LMFP) cathode materials offer higher energy density compared to LiFePO₄, making them a subject of widespread interest. However, their practical application is hindered by low power density resulting from inferior electron/Li-ion conductivities. In this study, a Mg-doped LiMn_0.5Fe_0.5PO₄ cathode is designed and synthesized. This cathode comprises secondary spherical particles self-assembled from nanoscale primary particles, with each nanoparticle uniformly coated by a carbon layer. The introduction of Mg-ions enhances Li-ion transfer efficiency by increasing the gap of octahedral LiO₆. At the same time, the carbon coating layer improves electronic conductivity by establishing a complete conductive network within the secondary particles. Moreover, the hierarchical structure shortens the migration path of Li-ions and prevents nanoparticle aggregation during long cycling processes. Consequently, the LMFP/C-1Mg cathode exhibits a reversible specific discharge capacity of 151.8 and 113 mAh/g at 0.1C and 5C, respectively. After 1000 cycles at 1C, the capacity retention increases from 90.6% to 96.4% compared to unmodified cathodes.

Key words: LiMn_0.5Fe_0.5PO₄, Mg doping, rate performance, lithium-ion batteries