Tween40 surfactant effect on the formation of nano-sized LiFePO4/C powder via a solid state reaction and their cathode properties

Abstract

Synthesizing nano-sized LiFePO 4 /C powders with less agglomeration using a solid state reaction method has become a hot research topic. This study synthesized nano-sized LiFePO 4 /C powder using FeC 2 O 4 , LiH 2 PO 4 as raw materials and tween40 as surfactant and examined the effect of tween40 surfactant addition on LiFePO 4 formation in a solid sate reaction. XRD, FTIR, SEM and TEM are used in this investigation. The results confirm the existence of interactions between the surfactant molecules and the precursor, which contribute to a uniform size distribution of the particles and a homogeneous carbon coating layer (about 8 nm) on the surface. The combination of nano-size and carbon coating plays a key role in the improvement of LiFePO 4 electrochemical performance. As a result, the prepared nano-LiFePO 4 /C composite synthesized with tween40 showed high electrochemical performance with a discharge capacity of 155.5 and 120 mAh g − 1 , respectively at room temperature of 25 °C and a low temperature of − 20 °C, under the discharge rate of 0.1 C. In addition, the sample showed an excellent low temperature cycling performance with capacity retention of 99.6% (0.1 C) and 99.4% (0.5 C) respectively after 100 cycles at − 20 °C. • Adding tween40 achieves the combine of particle minimization and carbon coating. • XRD results confirm that tween40 restricts the growth of LiH 2 PO 4 crystals. • FTIR spectrum confirms that tween40 surfactant bonded with Fe 2 C 2 O 4 particles. • The prepared LiFePO 4 /C shows a high low temperature electrochemical performance.