N-Methyl-2-pyrrolidone-assisted solvothermal synthesis of nanosize orthorhombic lithium iron phosphate with improved Li-storage performance

Abstract

Exploring an efficient and effective way for synthesis of lithium iron phosphate (LiFePO4) with good Li-storage performance is a good way to fully demonstrate their applications for Li-ion batteries. In this contribution, LiFePO4 nanoparticles were synthesized by a facile solvothermal process with water/N-methyl-2-pyrrolidone (NMP) solvent system at a moderate temperature of 180 °C. The product was determined as single-phase orthorhombic LiFePO4, and the presence of crystal growth inhibitor NMP was favourable for the formation of smaller-sized LiFePO4 particles with improved electrochemical properties. After a carbon coating process, the LiFePO4/C sample afforded a reversible capacity of 140 mA h g−1 at 0.5 C, 106 mA h g−1 at 5.0 C at room temperature, and 163 mA h g−1 at 0.5 C, 153 mA h g−1 at 5.0 C at the higher temperature of 60 °C, respectively. The long cycle test at 0.2 C showed that no noticeable capacity fading was observed. The present LiFePO4 obtained by the facile solvothermal process had good thermal and electrochemical stability, which were attributed to facile Li ion diffusion and a good electron transfer pathway in the solvothermal LiFePO4 product.