钇掺杂钛酸锂/石墨烯纳米复合材料的合成与电化学性能

以氧化石墨烯（GO）为基底，钛酸四丁酯、一水合氢氧化锂、六水合硝酸钇为原料，十六烷基三甲基溴化铵为表面活性剂，采用溶剂热法合成前驱体，在N2气氛保护下高温煅烧合成了钇掺杂钛酸锂/氧化石墨烯纳米复合材料。采用SEM、XRD、EDS、Raman对复合材料进行了形貌、结构和成分表征。将复合材料用作锂离子电池负极材料，采用循环伏安法、恒流充放电循环法研究了其电化学性能。结果表明，片状钛酸锂包覆在氧化石墨烯片上形成了钇掺杂钛酸锂/氧化石墨烯纳米复合材料。在100 mA/g的电流密度下，钇掺杂量为8%（以钛酸锂的物质的量为基准，下同）的纳米复合材料的首次放电比容量为145.5mA·h/g，经过100圈充放电循环后容量衰减几乎为0，经过200圈循环后容量衰减1.59%，经过300圈循环后容量衰减3.24%，与目前容量保持率只有80%左右的石墨负极相比有明显的改进。钇元素的掺杂和钛酸锂包覆氧化石墨烯形式的复合材料可以减小钛酸锂电极在充放电循环中的极化程度，从而改善了材料的循环性能。

Synthesis and electrochemical properties of yttrium-doped lithium titanate/graphene nanocomposites

With graphene as the base, tetrabutyl titanate, lithium hydroxide and yttrium nitrate as raw material, cetyl ammonium bromide as the surfactant, the nanocomposite precursor was synthesized by solvothermal method, and then the yttrium-doped lithium titanate/graphene nanocomposite was synthesized by calcination under the atmosphere of nitrogen. The morphology, structure and composition of the nanocomposite were characterized by SEM, XRD, EDS, Raman Spectroscopy, etc. The results show that yttrium doped lithium titanate / graphene nanocomposites were formed by coating flake lithium titanate on graphene sheets. The nanocomposite was used as anode material of the lithium-ion battery, and its electrochemical properties were studied by cyclic voltammetry and constant current charge-discharge cycle method. The results show that under the charge-discharge current density of 100 mA/g, the initial charge-discharge capacity of the nanocomposite is 145.5mAh/g, the capacity fading is almost 0 after 100 cycles of charge-discharge cycle, 1.59% after 200 cycles, and 3.24% after 300 cycles, which is significantly improved compared with the graphite anode whose capacity retention rate is only about 80%. Further research found that the doping of yttrium and the compositing of graphene can reduce the polarization degree of lithium titanate electrode in the charge and discharge cycle and improve the cycle performance of the material.