A maize-like FePO4@MCNT nanowire composite for sodium-ion batteries via a microemulsion technique

Abstract

In this study, a microemulsion technique was applied to prepare an in situ self-assembled core–shell FePO₄@MCNT nanowire composite as a cathode material for sodium-ion batteries. Multi-walled carbon nanotubes (MCNTs) were uniformly dispersed using Triton X-100 as a surfactant in the microemulsion system. Subsequently, amorphous FePO₄ nanoparticles with a diameter of 10–20 nm were loaded onto the surface of MCNTs during the synthetic process, forming an FePO₄@MCNT nanowire composite with three-dimensional mixed conducting networks, with a structure resembling maize. The resulting products were collected by centrifugation and washed three times, and sintered under an N₂ atmosphere at 460 °C for 3 h. The discharge specific capacity of FePO₄@MCNT was 155.2 mA h g⁻¹ in the initial cycle, which was maintained at 157.2 mA h g⁻¹ after 70 cycles at 0.1 C. The discharge specific capacity at 0.3 C, 0.5 C, and 1.0 C was 133.2 mA h g⁻¹, 122.2 mA h g⁻¹, and 75.3 mA h g⁻¹, respectively, in the range of 1.5–4.2 V. The results show that FePO₄@MCNT nanowires are promising candidates as cathode materials in sodium-ion batteries.