Hydrothermal synthesis of morphology-controlled LiFePO4 cathode material for lithium-ion batteries

Abstract

A simple sodium dodecyl benzene sulfonate (SDBS) mediated hydrothermal method has been described in this paper to prepare morphology-controlled LiFePO4, cathode material such as nanoparticles, nanorods and nanoplates with controllable b-axis thickness. When used in lithium-ion batteries, the LiFePO4/C nanoparticles (200 nm in size) and nanorods (90 nm in diameter along b-axis and 200 nm–1 μm in length) display initial discharge capacities of 145.3 and 149.0 mAh g−1 at 0.1 C rate, 33.9 and 61.3 mAh g−1 at 10 C rate, respectively. The LiFePO4/C nanoplates (20 nm thickness along b-axis and 50 nm width) deliver a discharge capacity of 162.9 mAh g−1 at 0.1 C rate and 107.9 mAh g−1 at 10 C rate. The Li-ion diffusion coefficients of the LiFePO4/C nanoparticles, nanorods and nanoplates are calculated to be 1.66 × 10−12, 2.99 × 10−12 and 1.64 × 10−11 cm2 s−1, respectively. In general, the discharge capacity and rate performance have been found to increase with the decreasing thickness of the b-axis. The experimental results demonstrate that decreasing the crystallite size in the b-axis and increasing the surface area of (010) plane can shorten Li-ion diffusion path and increase the electrode reaction, which significantly improve electrochemical performance of the LiFePO4/C nanocomposites.