Nano-scale flower-like structures from germanium sulfide (GeS)**Researchers Create �Nanoflowers� for Energy Storage, Solar Cells** Release Date: 10.11.2012 http://news.ncsu.edu/releases/wms-cao-flower/
Researchers from North Carolina State University have created flower-like structures out of germanium sulfide (GeS) � a semiconductor material � that have extremely thin petals with an enormous surface area. The GeS flower holds promise for next-generation energy storage devices and solar cells.
�Creating these GeS nanoflowers is exciting because it gives us a huge surface area in a small amount of space,� says Dr. Linyou Cao, an assistant professor of materials science and engineering at NC State and co-author of a paper on the research. �This could significantly increase the capacity of lithium-ion batteries, for instance, since the thinner structure with larger surface area can hold more lithium ions. By the same token, this GeS flower structure could lead to increased capacity for supercapacitors, which are also used for energy storage.�
To create the flower structures, researchers first heat GeS powder in a furnace until it begins to vaporize. The vapor is then blown into a cooler region of the furnace, where the GeS settles out of the air into a layered sheet that is only 20 to 30 nanometers thick, and up to 100 micrometers long. As additional layers are added, the sheets branch out from one another, creating a floral pattern similar to a marigold or carnation.
Role of Boundary Layer Diffusion in Vapor Deposition Growth of Chalcogenide Nanosheets: The Case of GeS http://pubs.acs.org/stoken/nanotation/pipe/abs/10.1021/nn303745e
We report a synthesis of single-crystalline two-dimensional GeS nanosheets using vapor deposition processes and show that the growth behavior of the nanosheet is substantially different from those of other nanomaterials and thin films grown by vapor depositions. The nanosheet growth is subject to strong influences of the diffusion of source materials through the boundary layer of gas flows. This boundary layer diffusion is found to be the rate-determining step of the growth under typical experimental conditions, evidenced by a substantial dependence of the nanosheet�s size on diffusion fluxes. We also find that high-quality GeS nanosheets can grow only in the diffusion-limited regime, as the crystalline quality substantially deteriorates when the rate-determining step is changed away from the boundary layer diffusion. We establish a simple model to analyze the diffusion dynamics in experiments. Our analysis uncovers an intuitive correlation of diffusion flux with the partial pressure of source materials, the flow rate of carrier gas, and the total pressure in the synthetic setup. The observed significant role of boundary layer diffusions in the growth is unique for nanosheets. It may be correlated with the high growth rate of GeS nanosheets, 3�5 ?m/min, which is 1 order of magnitude higher than other nanomaterials (such as nanowires) and thin films. This fundamental understanding of the effect of boundary layer diffusions may generally apply to other chalcogenide nanosheets that can grow rapidly. It can provide useful guidance for the development of general paradigms to control the synthesis of nanosheets.
Researchers develop paintable battery: Technique could turn any surface into lithium-ion battery (w/ Video)
Researchers at Rice University have developed a lithium-ion battery that can be painted on virtually any surface.
[November 23, 2011]
Copper hexacyanoferrate battery electrodes with long cycle life and high power http://www.nature.com/ncomms/journal/v2/n11/full/ncomms1563.html
Short-term transients, including those related to wind and solar sources, present challenges to the electrical grid. Stationary energy storage systems that can operate for many cycles, at high power, with high round-trip energy efficiency, and at low cost are required. Existing energy storage technologies cannot satisfy these requirements. Here we show that crystalline nanoparticles of copper hexacyanoferrate, which has an ultra-low strain open framework structure, can be operated as a battery electrode in inexpensive aqueous electrolytes. After 40,000 deep discharge cycles at a 17?C rate, 83% of the original capacity of copper hexacyanoferrate is retained. Even at a very high cycling rate of 83?C, two thirds of its maximum discharge capacity is observed. At modest current densities, round-trip energy efficiencies of 99% can be achieved. The low-cost, scalable, room-temperature co-precipitation synthesis and excellent electrode performance of copper hexacyanoferrate make it attractive for large-scale energy storage systems.
(a) CuHCF has the Prussian Blue crystal structure, in which octahedrally coordinated transition metals such as Cu and Fe are linked by CN ligands, forming a face-centred cubic structure. Fe is sixfold carbon-coordinated, while Cu is sixfold�
The 30-year battery: New chemistry holds promise - For bulk storage on the grid, Stanford research develop a new chemistry that could lead to durable, fast-charging batteries for storing wind and solar energy. http://news.cnet.com/8301-11128_3-57330311-54/the-30-year-battery-new-chemistry-holds-promise/
In the lab, the copper and iron-based nano-engineered material was able to take 40,000 charge/discharge cycles while still maintaining an 80 percent capacity. By contrast, the lithium ion batteries used in consumer electronics degrade noticeably after only a few hundred cycles.
- Battery research