Facile Ultrasonic Synthesis of CoO Quantum Dot/Graphene Nanosheet Composites with High Lithium Storage Capacity.
Summary of "Facile Ultrasonic Synthesis of CoO Quantum Dot/Graphene Nanosheet Composites with High Lithium Storage Capacity."
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 Co4(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 raised 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 associating 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 electrodes based lithium-ion batteries.
This article was published in the following journal.
Name: ACS nano
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Medical and Biotech [MESH] Definitions
Nanometer sized fragments (the dots) of semiconductor crystalline material which emit PHOTONS. The wavelength is based on the quantum confinement size of the dot. They are brighter and more persistent than organic chemical INDICATORS. They can be embedded in MICROBEADS for high throughput ANALYTICAL CHEMISTRY.
A subfield of acoustics dealing in the radio frequency range higher than acoustic SOUND waves (approximately above 20 kilohertz). Ultrasonic radiation is used therapeutically (DIATHERMY and ULTRASONIC THERAPY) to generate HEAT and to selectively destroy tissues. It is also used in diagnostics, for example, ULTRASONOGRAPHY; ECHOENCEPHALOGRAPHY; and ECHOCARDIOGRAPHY, to visually display echoes received from irradiated tissues.
The theory that the radiation and absorption of energy take place in definite quantities called quanta (E) which vary in size and are defined by the equation E=hv in which h is Planck's constant and v is the frequency of the radiation.
Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues using a transducer placed in the esophagus.
Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues. The standard approach is transthoracic.