A Simple and Facile Preparation of LiFePO₄ by a One-step Microwave Hydrothermal Method

Abstract

A novel method was used to synthesize LiFePO₄, using inorganic salts as raw materials, and PEG-4000 as the surfactant. The results show that LiFePO₄ powders with various morphologies were prepared by microwave hydrothermal method, and it is very important to synthesize the LiFePO₄ powders with well-defined shape and size controlling experimental conditions, such as the solution pH and surfactant. The modified preparation of LiFePO₄ was built. The coating carbon on LiFePO₄ powders as a core–shell structure was carried out by annealing in 3%H₂/97%N₂ at 700 °C for 2 h. As a result, the diffusion coefficient of lithium ions can be increased, and the reversibility of lithium intercalation and deintercalation can be improved markedly. In addition, LiMn_0.08Fe_0.92PO₄ powders were synthesized, which were observed in an ordered olivine structure, but great changes occurred in morphology. Doping Mn²⁺ does not destroy the lattice structure and enlarges the lattice volume. Consequently, the conductivity can be enhanced, and the lithium ion diffusion coefficient can be boosted. Initial discharge capacity is improved obviously, and increases to 99.6 mA h g⁻¹ and 93.8 mA h g⁻¹ respectively. The microwave assisted hydrothermal approach presented here opens a potential avenue to explore the synthesis of LiFePO₄ powders.