Preparation of high tap-density LiFePO4/C composite cathode materials by carbothermal reduction method using two kinds of Fe3+ precursors

LiFePO4 belongs to a new generation cathode material for lithium ion batteries. The improvement of the material's tap density is considered as an important research direction. LiFePO4/C composite was synthesized by a solid-state carbothermal reduction (CTR) method. The iron resource was obtained by the addition of (i) Fe2O3 and citrate ferric or (ii) single Fe2O3 as the Fe3+ precursors during synthesis. The LiFePO4/C composite synthesized with two kinds of Fe3+ precursors exhibited trimodal distribution and consisted of nanometer-sized and micrometer-sized particles, whereas the LiFePO4/C composite prepared with single Fe3+ precursor demonstrated unimodal distribution and was composed mainly of micrometer-sized particles. Because of the nanometer-sized particles filling in the space between the micrometer-sized particles, the composite synthesized with two kinds of Fe3+ precursors exhibited less vacancy than that prepared with single Fe3+ precursor and led to high tap density. The composite synthesized with two kinds of Fe3+ precursors had smaller grain size and resulted in superior discharge capacities at the rates of 0.1–1.0 C to that prepared with single Fe3+ precursor. The two kinds Fe3+ precursors method provides a simple and effective route to rapidly prepare high tap-density LiFePO4 product with excellent electrochemical performance, so it will achieve a wide-range of applications to the production of LiFePO4.