Titanate nanotubes combined with graphene-based materials as a novel anode material for lithium-ion batteries

Official URL: http://risc01.sabanciuniv.edu/record=b1640582 (Table of Contents)

Lithium-ion batteries are popular rechargeable energy storage devices due to their attractive properties such as good performance, high reliability, and a ordability. Due to the problametic dentride growth present in typical anode materials for conventional lithium-ion batteries, graphene-based materials have gotten a wide attention as alternative materials for graphite oxide. Graphene features a high electrical conductivity and good mechanical properties. Also being able to be functionalized makes them very attractive as support materials for other electrochemically active anode materials. Due to titanium dioxide (TiO2) being a non-toxic and cost-effective material with a capacity theoretically up to 335 mAh/g, it has become a hot research topic worldwide. Nevertheless, a poor electronic conductivity and a low rate capability are the main drawbacks which can be overcome by synergetic effects of composite materials. Titanate nanotubes (TiNTs) are promising materials because of their special morphology and high specific surface area. We introduce a novel one-step hydrothermal method to obtain TiNTs&graphene-based composites as our anode materials. The selforganized TiNTs (H2T3O7) are dispersed on the surface of various types of graphene based materials, namely graphene oxide (GO), reduced graphene oxide (rGO), nitrogen doped reduced graphene oxide (NrGO), popypyrrole functionalized graphene oxide (PPy-GO), graphene nanoplates (GNP), nitrogen noped graphene nanoplates (NGNP), and amino functionalized graphene oxide (GO-NH2). Material characterization such as X-ray powder di raction (XRD), Raman spectroscopy, Brunauer-Emmett- Teller (BET), scanning electron microscopy (SEM) are performed for all the as-prepared samples to examine the chemical compositions, elemental properties, and physical morphologies. Electrochemical characterizations such as charge and discharge, cyclic performance are conducted. The material characterization reveals well-aligned TiNTs which are homogeneously dispersed on the surface of the GO-based materials. A battery test is performed on four promising samples. Among all these samples, GO-NH2&TiNTs at pH=4 yields the best electrochemical performance. It exhibits a high capacity retention with only 11% capacity fading after the rst 4 cycles. Furthermore, its reversible capacity after 40 cycles is about 100 mAh/g with a high capacity stability. Charging and discharging cycle tests of our lithium-ion batteries reveal the anode materials have good stability in terms of capacity retention. Our findings suggest that the integrity of TiNTs are conserved well and the ion di usion rate is in good balance with the electron transfer.