In Situ Fabrication of 3-Dimentional Li4Ti5O12/Reduced Graphene Oxide Microspheres with High Tap Density for High-Rate Lithium Ion Batteries

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Spinel Li4Ti5O12 has attracted much attention as an anode material for lithium-ion batteries because of its good Li-ion intercalation reversibility and extremely small structural changes during charge-discharge cycling. Despite these advantages, Li4Ti5O12 is not suitable for commercial use due to its low electronic conductivity (10-13 S cm-1), which leads to poor rate capabiltiy.1 Several effective ways to improve the rate capability of Li4Ti5O12 have been reported, including reduction of the particle size to the nanoscale, doping Li, Ti, or O sites with small amounts of metal or nonmetal ions, surface modification or carbon coating, and its incorporation into composites with carbonaceous materials.2-4 Among the various carbonaceous materials, reduced graphene oxide (RGO) or graphene nanosheets has attracted considerable interest as electrode materials for electrochemical energy storage because of their unique properties such as high electronic conductivity, large surface area, and good mechanical properties. Some recent studies have demonstrated the excellent rate capability and cycle stability of Li4Ti5O12/RGO nanocomposites.4 However, in all these reports, the lithium–titanium–oxide (Li–Ti–O)/RGO nanocomposite as the precursor for Li4Ti5O12, was initially synthesized using a two-step or multistep process. In such multistep methods, Li4Ti5O12 particles can be limited the available sizes and morphologies. In addition, it is difficult to fabricate the phase-pure Li4Ti5O12 due to the formation of titanates with several other phases.5 Previously reported Li4Ti5O12/RGO nanocomposites mostly have 2-dimension morphologies with low tap density.4,5 The 2-dimentional Li4Ti5O12/RGO nanocomposites are not suitable for commercial use because their low tap density limits the volumetric energy density. Therefore, a simple and facile synthesis of 3-dimentional Li4Ti5O12/RGO nanocomposites with a high tap density and superior rate capability is highly desirable. In this study, we report in-situ synthesis of 3-dimentional Li4Ti5O12/RGO microspheres with high tap density, wherein the initial Li-Ti-O/RGO precursor is fabricated by the spray drying method in the presence of all precursors in a solution. Upon subsequent heat treatment, phase-pure 3-dimentional Li4Ti5O12/RGO microspheres with high tap density were successfully synthesized. More detailed on the synthetic procedure, morpology, electrochemical and structural properties of 3-dimentional Li4Ti5O12/RGO microspheres will be presented at the meeting.