Enhancing the electrochemical performance of lithium ion batteries using mesoporous Li3V2(PO4)3/C microspheres

Abstract

Mesoporous Li₃V₂(PO₄)₃–carbon (LVP-C) microspheres are synthesized using Baker's yeast cells as both mesoporous structure templates and amorphous carbon sources. We find that the vanadium cations are combined with the negatively charged hydrophilic groups and are self-assembled both on the yeast cell wall surface and inside the cell by electrostatic interaction and metabolism regulation, respectively. The self-assembly leads to the formation of LVP-C microspheres with diameters of 1–8 μm. These microspheres are composed of densely aggregated nanoparticles (20–40 nm) as well as interconnected nanopores (2–15 nm), and hence they are of mesoporous nature. The nanoparticles can be easily brought into contact with electrolyte, and the open mesoporous structure allows lithium ions to easily penetrate into the microspheres. The carbon network (16.4 wt.%) on the surface of the Li₃V₂(PO₄)₃ nanoparticles facilitates electron diffusion. The mesoporous LVP-C microspheres have a high discharge capacity (about 126.7 mAh g⁻¹), only 2% capacity loss of the initial value at the 50th cycle at a current density of 0.2 C, and a high rate capacity of 100.5 mAh g⁻¹ at 5 C in the region of 3.0–4.3 V. The apparent Li⁺ diffusion coefficient is found to be 6.76 × 10⁻¹⁰ cm² s⁻¹. The microspheres could be an ideal cathode-active material that fulfills the requirements of rechargeable lithium batteries for high power applications.