Synthesis of LiMnPO4 microspheres assembled by plates, wedges and prisms with different crystallographic orientations and their electrochemical performance

Abstract

Olivine-structured LiMnPO₄ microspheres assembled by plates, wedges and prisms with different crystallographic orientations were synthesized via a facile hydrothermal route at 200 °C for 10 h. Na₂S·9H₂O was employed as a sole additive for controlling the phase, shape and crystallographic orientation of LiMnPO₄ microspheres. The obtained product was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The possible formation mechanism was proposed based on time-dependent experiments. The electrochemical properties of carbon-coated LiMnPO₄ samples with different assembly units were investigated. The synthesized LiMnPO₄ microspheres assembled with plates exhibited higher discharge capacity, more stable cycling stability and better rate capability, which were attributed to the exposed (010) facets as well as small thickness along the [010] direction allowing for a fast Li⁺ ion diffusion rate and short diffusion length.