Effects of Li2SO4·H2O amounts on morphologies of hydrothermal synthesized LiMnPO4 cathodes

Abstract

Developing an industrial LiMnPO₄ cathode, featuring a high rate capability, is still a huge challenge because of its slow Li⁺ diffusion speed as well as low electronic conductivity. Here, we expect to address these inherent obstacles by controlling its morphology in a well-dispersed way. The effects of the added amounts of Li₂SO₄·H₂O on the morphologies of the LiMnPO₄ samples prepared via the hydrothermal method were studied using structural and morphological characterizations. Based on the additional independent experiments, a two-step reaction was tentatively proposed to understand the formation of the LiMnPO₄ samples and the dual functions of Li₂SO₄·H₂O. For synthesizing LiMnPO₄ samples, a high SO₄²⁻ concentration may be helpful for a fast nucleation rate, while a high Li⁺ concentration can be beneficial for a rapid growth rate. The results showed that the LiMnPO₄ sample prepared with 40 mmol Li₂SO₄·H₂O (denoted as the S4) exhibited the best electrochemical performances in terms of the discharge capacity, the rate capability and the cycling stability among all the LiMnPO₄ samples, which was reasonably attributed to its well-dispersed characteristics.