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

•Adding tween40 achieves the combine of particle minimization and carbon coating.•XRD results confirm that tween40 restricts the growth of LiH2PO4 crystals.•FTIR spectrum confirms that tween40 surfactant bonded with Fe2C2O4 particles.•The prepared LiFePO4/C shows a high low temperature electrochemical performance.

Synthesizing nano-sized LiFePO4/C powders with less agglomeration using a solid state reaction method has become a hot research topic. This study synthesized nano-sized LiFePO4/C powder using FeC2O4, LiH2PO4 as raw materials and tween40 as surfactant and examined the effect of tween40 surfactant addition on LiFePO4 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 LiFePO4 electrochemical performance. As a result, the prepared nano-LiFePO4/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.