Effects of amorphous AlPO4 coating on the electrochemical performance of BiF3 cathode materials for lithium-ion batteries

Abstract

The BiF3/AlPO4 composite has been synthesized using the mixture of as-prepared BiF3 and amorphous AlPO4 powder as the starting materials by solid state method. The structure and morphology of AlPO4 and BiF3/AlPO4 composite have been characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The electrochemical performance of BiF3/AlPO4 composite has been studied by galvanostatic charge/discharge, cyclic voltammetry (CV) measurements. The results show that the as-prepared AlPO4 is amorphous, and the addition of amorphous AlPO4 does not change the bulk structure of BiF3, but AlPO4 is only coated on the surface of BiF3 forming the BiF3/AlPO4 composite. Electrochemical measurements in the voltage range of 1.5–4.5 V reveal that the addition of amorphous AlPO4 can effectively reduce the effect of solid electrolyte interface (SEI) and markedly improve the electrochemical performance of BiF3 in the EC:DMC electrolyte. And the BiF3/AlPO4 composite delivers an initial discharge capacity of 271.5 mAh g−1 and a reversible capacity of 209.1 mAh g−1 at a current density of 30 mA g−1. Furthermore, the BiF3/AlPO4 composite also exhibits enhanced rate capability and acceptable cycle performance.