LiTi2(PO4)3/reduced graphene oxide hybrids for high performance cathode materials in lithium ion batteries

Abstract

Recently, LiTi2(PO4)3 [LTP] has emerged as a promising candidate for both cathode and anode materials of rechargeable organic and aqueous lithium batteries, respectively, owing to their thermal stability, environmental benignity and low cost1,2. Moreover, LTP possesses NASICON type open-framework with three-dimensional structure. Thus, LTP has good ionic conductivity and a flat plateau around 2.5 V. However, its low electronic conductivity has led to lower capacity utilization, which limits its application in lithium ion battery. Other phosphate based cathode materials also exhibit similar challenge and various studies have focused on the improvement of electronic conductivity using thin carbon coating, metal ion doping and physical mixing of conductive materials. Graphene has recently attracted significant attention due to their superior electrical conductivity, high surface-to-volume ratio, structural flexibility, and chemical stability5. Therefore, graphene could be utilized to improve the electrochemical performance of LTP particles. In this work, we have employed two-step approach to synthesize LTP/reduced graphene oxide (rGO) hybrid material. In the first step, the TiO2 nanoparticles were grown on graphene oxide sheets (prepared by modified Hummer’s method6), which were stably suspended in aqueous solution. The suspended TiO2 nanoparticles on graphene oxide sheets were later transformed into LTP through solid state reaction at high temperature. This second step also helps to reduce graphene oxide. The crystal structure and morphology of the synthesized hybrid materials were characterized using X-ray diffractometer (Rigaku D/max) and scanning electron microscope (Magellan), respectively.