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Graphene

[Due to the increasing size of the archives, each topic page now contains only the prior 365 days of content. Access to older stories is now solely through the Monthly Archive pages or the site search function.]

New silicon-sulfur battery built on 3D graphene shows excellent performance

April 28, 2016

Researchers at Beihang University in Beijing have developed a new Li-sulfur battery using honeycomb-like sulfur copolymer uniformly distributed onto 3D graphene (3D cpS-G) networks for a cathode material and a 3D lithiated Si-G network as anode.

In a paper published in the RSC journal Energy & Environmental Science, they reported that the full cell exhibits superior electrochemical performances in term of a high reversible capacity of 620 mAh g-1, ultrahigh energy density of 1147 Wh kg−1 (based on the total mass of cathode and anode), good high-rate capability and excellent cycle performance over 500 cycles (0.028% capacity loss per cycle).

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New silicon oxycarbide glass/graphene anode material; lightweight, high-capacity and long cycle life

April 11, 2016

Researchers at Kansas State University have developed a new high-performance Li-ion battery anode material combining silicon oxycarbide (SiOC) glass and graphene. The self-standing (i.e., no current collector or binder) anode material comprises molecular precursor-derived SiOC glass particles embedded in a chemically-modified reduced graphene oxide (rGO) matrix.

The porous reduced graphene oxide matrix serves as an effective electron conductor and current collector with a stable mechanical structure, and the amorphous silicon oxycarbide particles cycle lithium-ions with high Coulombic efficiency. The SiOC-rGO composite electrode delivers a charge capacity of ~588 mAh g−1electrode (~393 mAh cm−3electrode) at the 1,020th cycle and shows no evidence of mechanical failure.

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Researchers develop all-weather solar cell that generates power from rain as well as from sun

April 03, 2016

While many technical advances have made solar cells more efficient and affordable, a disadvantage remains in the fact that solar cells produce no power when it’s raining. Now, however, researchers from the Ocean University of China (Qingdao) and Yunnan Normal University (Kunming, China) have developed an all-weather solar cell that is triggered by both sunlight and raindrops by combining an electron-enriched graphene electrode with a dye-sensitized solar cell.

The new solar cell can be excited by incident light on sunny days and raindrops on rainy days, yielding an optimal solar-to-electric conversion efficiency of 6.53% under AM 1.5 irradiation and current over microamps as well as a voltage of hundreds of microvolts by simulated raindrops. Their work is published as a “Very Important Paper” in the journal Angewandte Chemie.

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LLNL team finds certain graphene metal oxide nanocomposites increase Li-ion capacity and cycling performance

March 22, 2016

Material scientists at Lawrence Livermore National Laboratory have found that certain graphene metal oxide (GMO) nanocomposites increase capacity and improve cycling performance in lithium-ion batteries.

The team synthesized and compared the electrochemical performance of three representative graphene metal oxide nanocomposites—Fe2O3/graphene, SnO2/graphene, and TiO2/graphene—and found that two of them greatly improved reversible lithium storage capacity. The research appears on the cover of the 21 March edition of the Journal of Materials Chemistry A.

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Berkeley Lab team develops new high-performance solid-state H2 storage material: graphene oxide (GO)/Mg nanocrystal hybrid

March 12, 2016

Researchers at Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a new, environmentally stable solid-state hydrogen storage material constructed of Mg nanocrystals encapsulated by atomically thin and gas-selective reduced graphene oxide (rGO) sheets.

This material, protected from oxygen and moisture by the rGO layers, exhibits dense hydrogen storage (6.5 wt% and 0.105 kg H2 per liter in the total composite). As rGO is atomically thin, this approach minimizes inactive mass in the composite, while also providing a kinetic enhancement to hydrogen sorption performance.

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Stanford, SLAC team cages silicon microparticles in graphene for stable, high-energy anode for Li-ion batteries

January 28, 2016

A team from Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory has developed a new practical, high-energy-capacity lithium-ion battery anode out of silicon by encapsulating Si microparticles (∼1–3 µm) using conformally synthesized cages of multilayered graphene.

The graphene cage acts as a mechanically strong and flexible buffer during deep cycling, allowing the silicon microparticles to expand and fracture within the cage while retaining electrical connectivity on both the particle and electrode level.

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Graphene ultracapacitor company Skeleton Technologies secures €4M from KIC InnoEnergy; targeting 20 Wh/kg by 2020

European ultracapacitor manufacturer Skeleton Technologies received a €4-million (US$4.4-million) investment from KIC InnoEnergy, an investment company dedicated to promoting sustainable innovation and entrepreneurship in Europe’s energy industry.

The €4m investment from KIC InnoEnergy—the shareholders of which include ABB, EDF, Iberdrola and Total—will be used to further develop the competitive advantage of Skeleton Technologies’ ultracapacitors. The company aims to reach the ambitious target of 20 Wh/kg energy density for its technology by 2020.

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Northwestern researchers discover crumpled graphene balls are a promising lubricant additive

January 26, 2016

Researchers at Northwestern University’s McCormick School of Engineering have found that crumpled graphene balls are an extremely promising lubricant additive. In a series of tests, a polyalphaolefin base oil with only 0.01–0.1 wt % of crumpled graphene balls outperformed a fully formulated commercial lubricant in terms of friction and wear reduction. A paper on their work is published in the Proceedings of the National Academy of Sciences.

For the average car, 15% of the fuel consumption is spent overcoming friction in the engine and transmission. While oil helps reduce this friction, researchers have long sought additives that enhance oil’s performance. Ultrafine particles are often used as lubricant additives because they are capable of reducing friction and protecting surfaces from wear. They also tend to be more stable than molecular additives under high thermal and mechanical stresses during rubbing. However, they also can aggregate, reducing the effective concentration.

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LLNL team finds hydrogen treatment improves performance of graphene nanofoam anodes in Li-ion batteries

November 05, 2015

Lawrence Livermore National Laboratory researchers have found, through experiments and calculations, that hydrogen-treated graphene nanofoam (GNF) anodes in lithium-ion batteries (LIBs) show higher capacity and faster transport. The research suggests that controlled hydrogen treatment may be used as a strategy for optimizing lithium transport and reversible storage in other graphene-based anode materials. An open-access paper on their work is published in Nature Scientific Reports.

Commercial applications of graphene materials for energy storage devices, including lithium ion batteries and supercapacitors, hinge critically on the ability to produce these materials in large quantities and at low cost. However, the chemical synthesis methods frequently used leave behind significant amounts of atomic hydrogen, whose effect on the electrochemical performance of graphene derivatives is difficult to determine.

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Atomic cobalt on nitrogen-doped graphene catalyst shows promise to replace platinum for hydrogen production

October 21, 2015

The Rice lab of chemist James Tour and colleagues at the Chinese Academy of Sciences, the University of Texas at San Antonio and the University of Houston have developed a robust, solid-state catalyst that shows promise to replace expensive platinum for hydrogen generation.

The new electrocatalyst, based on very small amounts of cobalt dispersed as individual atoms on nitrogen-doped graphene (Co-NG), is robust and highly active in aqueous media with very low overpotentials (30 mV). In an open-access paper published in Nature Communications, the researchers suggested that the unusual atomic constitution of supported metals is suggestive of a new approach to preparing extremely efficient single-atom catalysts.

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Very high-performance silicon anodes with engineered graphene assemblies

August 27, 2015

Researchers in China have developed a self-supporting high-performance silicon anode for Li-ion batteries (LIBs) consisting of silicon-nanoparticle-impregnated assemblies of templated carbon-bridged oriented graphene.

The binder-free anodes demonstrate exceptional lithium storage performances, simultaneously attaining high gravimetric capacity (1390 mAh g–1 at 2 A g–1 with respect to the total electrode weight); high volumetric capacity (1807 mAh cm–3—more than three times that of graphite anodes); remarkable rate capability (900 mAh g–1 at 8 A g–1); excellent cyclic stability (0.025% decay per cycle over 200 cycles); and competing areal capacity (as high as 4 and 6 mAh cm–2 at 15 and 3 mA cm–2, respectively) that approaches the level of commercial lithium-ion batteries. A paper on their work is published in the ACS journal Nano Letters.

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Laser-burned graphene could replace platinum as fuel cell catalyst

August 21, 2015

Researchers at the Tour Lab at Rice University developed an improved cost-effective approach using direct laser scribing to prepare graphene embedded with various types of metallic nanoparticles. The resulting metal oxide-laser induced graphene (MO-LIG) is highly active in electrochemical oxygen reduction reactions with a low metal loading of less than 1 at%. As such, it could be a candidate to replace expensive platinum in catalysts for fuel cells and other applications.

In addition, the researchers noted in their open access paper published in ACS Nano, the nanoparticles can vary from metal oxide to metal dichalcogenides through lateral doping, making the composite active in other electrocatalytic reactions such as hydrogen evolution.

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NSF funds new center for advanced 2-D coatings; energy conversion and storage

August 13, 2015

A new NSF-funded Industry/University Collaborative Research Center (I/UCRC) at Penn State and Rice University will study the design and development of advanced coatings based on two-dimensional (2D) layered materials to solve fundamental scientific and technological challenges that include: corrosion, oxidation and abrasion, friction and wear, energy storage and harvesting, and the large-scale synthesis and deposition of novel multifunctional coatings.

The Center for Atomically Thin Multifunctional Coatings, (ATOMIC), is one of more than 80 Industry/University Cooperative Research Program centers established by the National Science Foundation (NSF) to encourage scientific collaboration between academia and industry. It is the only NSF center dedicated to the development of advanced 2-D coatings.

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Manchester team greatly broadens thermal window of thermoelectric material using graphene; potential vehicle applications for waste heat recovery

July 22, 2015

Researchers at the University of Manchester (UK) have shown that the thermal operating window of the thermoelectric material lanthanum strontium titanium oxide (LSTO) can be expanded down to room temperature by addition of a small amount of graphene. Applications of LSTO-based thermoelectric materials are currently limited by their high operating temperatures of >700 °C.

Rather than working within the usual narrow “thermal window”, these bulk graphene/LSTO nanocomposites exhibit useful ZT values across a broad temperature range of several hundred degrees, the team reported in the journal ACS Applied Materials & Interfaces. This increase in operating performance can enable future applications such as thermoelectric generators in vehicles for waste heat recovery and other sectors, the researchers suggested.

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Argonne researchers develop macroscale superlubricity system with help of Mira supercomputer; potential for “lubricant genome”

Argonne scientists have used the Mira supercomputer to identify and to improve a new mechanism for eliminating friction, which fed into the development of a hybrid material that exhibited superlubricity—a state in which friction essentially disappears—at the macroscale—i.e., at engineering scale—for the first time. A paper on their work was published in the journal Science.

They showed that superlubricity can be realized when graphene is used in combination with nanodiamond particles and diamond-like carbon (DLC). Simulations showed that sliding of the graphene patches around the tiny nanodiamond particles led to nanoscrolls with reduced contact area that slide easily against the amorphous diamond-like carbon surface, achieving incommensurate contact and a substantially reduced coefficient of friction (~0.004).

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New rationally designed high-performance Li-S cathode; rate performance, capacity and long life

July 10, 2015

Researchers in China report the development of a rationally designed Li−S cathode consisting of a freestanding composite thin film assembled from sulfur nanoparticles, reduced graphene oxide (rGO), and a multifunctional additive poly(anthraquinonyl sulfide) (PAQS): nano-S:rGO:PAQS.

The resulting cathode exhibits an initial specific capacity of 1255 mAh g−1 with a decay rate as low as 0.046% per cycles over 1,200 cycles. Importantly, the nano-S:rGO:PAQS batteries exhibit significant rate performances. They maintain a reversible capacity of ∼615 mAh g−1 at a rate of 13.744 A g−1 (=8 C) after more than 60 cycles at various rates and can still have a reversible capacity of ∼1000 mAh g−1 when further cycled at 0.25 C. A paper explaining their work appears in the ACS journal Nano Letters.

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Lux: graphene severely underperforming commercially against “massive hype”

July 06, 2015

Market analyst firm Lux Research has maintained a skeptical stance about the commercial prospects of graphene even in the light of the material’s compelling properties. In a 2012 report “Is Graphene the Next Silicon...Or Just the Next Carbon Nanotube?”, Lux examined the interplay between graphene’s compelling performance properties as an advanced material, and the significant hurdles it would inevitably face transitioning from the lab to the marketplace. A research and patent boom along with impressive technical performance is far from a guarantee of commercial success.

Lux is now answering its own question with the assertion that graphene looks much closer to the next carbon nanotube than the next silicon. Reasons the firm gives for this assessment include:

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Skeleton Technologies launches new range of high-performance ultracapacitors; up to 111 kW/kg and 9.6 Wh/kg; hybrid truck application coming

June 30, 2015

Skeleton Technologies (earlier post) has launched a new range of cylindrical ultracapacitors that offers specific power performance of up to 111 kW/kg (SC450, 450F) and specific energy up to 9.6 Wh/kg (SC4500, 4500F) with ESR as low as 0.075 mΩ (SC3000, 3000F)—the highest performance cylindrical cell ultracapacitors in the market.

Through the use of its patented graphene material, the new series features a capacitance of up to 4500 farads (the SC4500 cell). By contrast, the closest competitor product has a capacitance of 3400 farads. Skeleton claims this is the single biggest increase in energy density for ultracapacitors in the past 15 years.

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New Samsung silicon anode with graphene boosts volumetric capacity of LiCoO2 Li-ion cell 1.5x after 200 cycles; gravimetric capacity the same

June 27, 2015

A team at Samsung Advanced Institue of Technology (SAIT, Samsung’s global R&D hub) reports in an open access paper published in the journal Nature Communications on a new approach to advance high-capacity silicon (Si) anodes for Li-ion batteries (LIBs) to commercial viability, with a particular focus on improving the volumetric capacity of LIBs.

The SAIT team fabricated the anode material by growing graphene directly on a silicon surfaces while avoiding Si carbide (SiC) formation by developing a chemical vapor deposition (CVD) process that includes CO2 as a mild oxidant. The graphene-coated silicon nanoparticles (Gr-Si NPs) reach a volumetric capacity of 2,500 mAh cm−3 (versus 550 mAh cm−3 of commercial graphite), the highest volumetric value among those reported to date for any LIB anodes while exhibiting excellent cycling and rate performance.

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Tsinghua team develops high-efficiency and high-stability Li metal anodes for Li-sulfur batteries

June 14, 2015

Researchers from Tsinghua University have developed what they call a “promising strategy” to tackle the intrinsic problems of lithium metal anodes for Lithium sulfur batteries—dendritic and mossy metal depositing on the anode during repeated cycles leading to serious safety concerns and low Coulombic efficiency.

As described in a paper published in the journal ACS Nano, the researchers devised a nanostructured graphene framework coated by an in situ formed solid electrolyte interphase (SEI) with Li depositing in the pores (SEI-coated graphene, SCG). The graphene-based metal anode demonstrated superior dendrite-inhibition behavior in 70 hours of lithiation, while a control cell with a copper foil-based metal anode short-circuited after only 4 hours of lithiation at 0.5 mA cm–2.

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