Bio-synthesis participated mechanism of mesoporous LiFePO4/C nanocomposite microspheres for lithium ion battery

Abstract

In this paper we report a bio-synthesis route towards controllable mesoporous LiFePO₄/C nanocomposite microspheres (MP-LFP/C-NC-MS). During the synthesis baker's yeast cells were used as both structure templates and a carbon source. Then we clarify the bio-deposited and biomolecular self-assembly mechanisms of iron phosphate by means of the Langmuir biosorption isotherms of the yeast biomass in iron ion solution and by applying the model of heterogeneous nucleation of iron phosphate in a yeast cell. The MP-LFP/C-NC-MS show a uniform size distribution (4.76 μm), high tap density (1.74 g cm⁻³) and a large specific surface area (203 m² g⁻¹). The microsphere is composed of densely aggregated nanoparticles and interconnected nanopores. The open mesoporous structure allows lithium ions to easily penetrate into the spheres, while a thorough coating of the biocarbon network on the surface of the LiFePO₄ nanoparticles facilitates lithium ion and electron diffusion. The MP-LFP/C-NC-MS have a high discharge capacity of about 158.5 mA h g⁻¹ at a current density of 0.1 C, discharge capacity of 122 mA h g⁻¹ at 10 C, and high capacity retention rate. Therefore the mesoporous microspheres are an ideal type of cathode-active materials for making high-power Li-ion batteries.