Facile Ultrasonic Synthesis of CoO Quantum Dot/Graphene Nanosheet Composites with High Lithium Storage Capacity
Facile Ultrasonic Synthesis of CoO Quantum Dot/Graphene Nanosheet Composites with High Lithium Storage Capacity
复制标题
简便超声合成具有高储锂能力的CoO量子点/石墨烯纳米片复合材料
DOI：
10.1021/nn202888d
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发表时间：
2012-02-01
期刊：
影响因子：
17.1
通讯作者：
Yang, Jinhu
中科院分区：
文献类型：
--
作者：
Peng, Chengxin;Chen, Bingdi;Yang, Jinhu
在本文中，我们报道了一种简便的超声波方法，以 Co-4(CO)(12) 作为钴前驱体，在室温下在石墨烯纳米片上合成分散良好的 CoO 量子点 (3-8 nm)。所制备的CoO/石墨烯复合材料显示出作为锂离子电池负极材料的高性能，如高可逆储锂容量（50次循环后为1592 mAh g(-1)）、高库仑效率（超过95%）、优异的循环稳定性和高倍率性能（在1000 mA g(-1)电流密度下，50次循环后为1008 mAh g(-1)，总保留率为77.6%）。从最初的 50 mA g(-1)) 急剧增加。非凡的性能源于复合材料的结构优势：导电石墨烯基底上高分散的纳米级CoO量子点不仅为锂离子嵌入提供了大量可接近的活性位点，而且具有良好的导电性和短的锂离子扩散长度，这有利于高容量和倍率性能。同时，紧密锚定在石墨烯纳米片上的孤立的CoO量子点可以有效地避免在放电/充电过程中与锂嵌入/脱嵌相关的体积膨胀/收缩，这有利于高容量和循环稳定性。此外，针对观察到的容量随循环增加的异常行为（激活效应），我们提出了一个初步假设，强调循环过程中复合电极的电导率增加和非晶化之间的竞争决定容量的趋势，以期更全面地了解新型纳米结构电极基锂离子电池的内部工作原理。
In this paper, we report a facile ultrasonic method to synthesize well-dispersed CoO quantum dots (3-8 nm) on graphene nanosheets at room temperature by employing Co-4(CO)(12) as cobalt precursor. The prepared CoO/graphene composites displayed high performance as an anode material for lithium-ion battery, such as high reversible lithium storage capacity (1592 mAh g(-1) after 50 cycles), high Coulombic efficiency (over 95%), excellent cycling stability, and high rate capability (1008 mAh g(-1) with a total retention of 77.6% after 50 cycles at a current density of 1000 mA g(-1), dramatically increased from the initial 50 mA g(-1)). The extraordinary performance arises from the structure advantages of the composites: the nanosized CoO quantum dots with high dispersity on conductive graphene substrates supply not only large quantity of accessible active sites for lithium-ion insertion but also good conductivity and short diffusion length for lithium ions, which are beneficial for high capacity and rate capability. Meanwhile, the isolated CoO quantum dots anchored tightly on the graphene nanosheets can effectively circumvent the volume expansion/contraction associated with lithium insertion/extraction during discharge/charge processes, which is good for high capacity as well as cycling stability. Moreover, regarding the anomalous behavior of capacity increase with cycles (activation effect) observed, we proposed a tentative hypothesis stressing the competition between the conductivity increase and the amorphorization of the composite electrodes during cycling in determining the trends of the capacity, in the hope to gain a fuller understanding of the inner working of the novel nanostructured electrode-based lithium-ion batteries.