Mg-doped porous spherical LiFePO4/C with high tap-density and enhanced electrochemical performance

Abstract

Composition regulate and morphology control can lead to LiFePO4 cathode material with high physicochemical properties for practical applications. Herein, we report a facile solid-phase method to design and synthesize Mg-doped carbon-coated porous spherical LiFePO4/C composite with ultralow carbon content (1.6 wt%) and high tap-density (1.13 g/cm3). It shows that the LiFePO4/C maintains an olivine-type crystal structure with tiny amounts of Mg doping, and the cell parameters can be optimized with a Mg doping content of 0.03 (LiMg0·03Fe0·97PO4/C). In the structure of optimized LiMg0·03Fe0·97PO4/C, well-crystallized LiMg0·03Fe0·97PO4 particles with a diameter of ∼100 nm are uniformly covered by a carbon layer of ∼3 nm to form primary LiMg0·03Fe0·97PO4/C, which are assembled into standard spherical-shaped secondary particles with a diameter of few microns to tens of microns. Benefiting from the contributions of morphology controlling, Mg doping and carbon coating, LiMg0·03Fe0·97PO4/C manifests excellent rate and cycle performance, which exhibits capacities of 158, 145 and 105 mA h g−1 at 0.2C, 1C and 10C, respectively, as well as a capacity attenuation rate of 0.02% per cycle during 1000 cycles at a high rate of 10C.