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Talga Boosts European Natural Graphite Resources

Posted By Graphene Council, Saturday, September 19, 2020
Talga Resources is pleased to announce significant increases in the Company’s natural graphite mineral resources within its wholly-owned Vittangi Graphite Project in northern Sweden.

Talga has completed a review of its four JORC (2012) compliant graphite mineral resources within Vittangi to standardise parameters for increased accuracy in upcoming feasibility studies and enable better mine planning, permitting and reporting.

The review also identified significant new Exploration Targets to be tested along strike and at depth from current resources, providing potential for future additional resource growth. Highlights  of results of the review include:

• Updated Nunasvaara South Mineral Resource Estimate defines 15% increase in total natural graphite resources at Vittangi

• Vittangi graphite mineral resource now stands at 19.5 million tonnes at 24.0% graphite (based on a revised 10% cut-off grade across the project)

• Vittangi remains the world’s highest grade natural graphite resource1, set to play a significant role in battery anode production for the booming electric vehicle market

• Talga’s total graphite resource inventory in Sweden increases to 55.3 million tonnes at 17.5% graphite, representing the largest source of natural graphite defined in Europe2

• Additional growth Exploration Targets totalling 26–46 million tonnes at 20–30% graphite defined within Vittangi and set to be drill-tested for potential further increases in scale

Note that the potential quantity and grade of the Exploration Target is conceptual in nature, there has been insufficient exploration to estimate a Mineral Resource and it is uncertain if further exploration will result in the estimation of a Mineral Resource.

Commenting on the resource upgrade, Talga Managing Director Mark Thompson said: “We are pleased to continue defining and growing these globally significant and strategically important European graphite deposits.“

“The European Commission recently published an updated list of Critical Raw Materials necessary for the energy transition to a more sustainable society. Natural graphite features on this list of materials vital to European development as it forms nearly half the volume of active materials in electric vehicle batteries, where it is used as the anode.”

“With projected anode demand set to reach 3.2 million tonnes by 20303 the potential of Talga’s Swedish integrated natural graphite anode production facility is significant for the European electric vehicle supply chain and the ‘green’ economy.

Tags:  Batteries  Graphene  Graphite  Mark Thompson  Talga Resources 

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WHAT HAPPENS BETWEEN THE SHEETS? ‘FLOATING’ GRAPHENE ON A BED OF CALCIUM ATOMS

Posted By Graphene Council, Saturday, September 19, 2020
Adding calcium to graphene creates an extremely-promising superconductor, but where does the calcium go?

Adding calcium to a composite graphene-substrate structure creates a high transition-temperature (Tc) superconductor.

In a new study, an Australian-led team has for the first time confirmed what actually happens to those calcium atoms: surprising everyone, the calcium goes underneath both the upper graphene sheet and a lower ‘buffer’ sheet, ‘floating’ the graphene on a bed of calcium atoms.

Superconducting calcium-injected graphene holds great promise for energy-efficient electronics and transparent electronics.

STUDYING CALCIUM-DOPED GRAPHENE: THROWING OFF THE DUVET

Graphene’s properties can be fine-tuned by injection of another material (a process known as ‘intercalation’) either underneath the graphene, or between two graphene sheets.

This injection of foreign atoms or molecules alters the electronic properties of the graphene by either increasing its conductance, decreasing interactions with the substrate, or both.

Injecting calcium into graphite creates a composite material (calcium-intercalated graphite, CaC6) with a relatively ‘high’ superconducting transition temperature (Tc). In this case, the calcium atoms ultimately reside between graphene sheets.

Injecting calcium into graphene on a silicon-carbide substrate also creates a high-Tc superconductor, and we always thought we knew where the calcium went in this case too…

Graphene on silicon-carbide has two layers of carbon atoms: one graphene layer on top of another ‘buffer layer’: a carbon layer (graphene-like in structure) that forms between the graphene and the silicon-carbide substrate during synthesis, and is non-conducting due to being partially bonded to the substrate surface.

“Imagine the silicon carbide is like a mattress with a fitted sheet (the buffer layer bonded to it) and a flat sheet (the graphene),” explains lead author Jimmy Kotsakidis.

Conventional wisdom held that calcium should inject between the two carbon layers (between two sheets), similar to injection between the graphene layers in graphite. Surprisingly, the Monash University-led team found that when injected, the calcium atoms’ final destination location instead lies between buffer layer and the underlying silicon-carbide substrate (between the fitted sheet and the mattress!).

“It was quite a surprise to us when we realised that the calcium was bonding to the silicon surface of the substrate, it really went against what we thought would happen”, explains Kotsakidis.

Upon injection, the calcium breaks the bonds between the buffer layer and substrate surface, thus, causing the buffer layer to ‘float’ above the substrate, creating a new, quasi-freestanding bilayer graphene structure (Ca-QFSBLG).

This result was unanticipated, with extensive previous studies not considering calcium intercalation underneath the buffer layer. The study thus resolves long-standing confusion and controversy regarding the position of the intercalated calcium.

X-ray photoelectron spectroscopy (XPS) measurements at the Australian Synchrotron were able to pinpoint the location of the calcium near to the silicon carbide surface

Results were also supported by low-energy electron diffraction (LEED), and scanning tunnelling microscopy (STM) measurements, and by modelling using density functional theory (DFT).

AND MAGNESIUM TOO…
With this information at hand, the Australian team also decided to investigate if magnesium–which is notoriously difficult to inject into the graphite structure –could be inserted (intercalated) into graphene on a silicon-carbide substrate.

To the researchers’ surprise, magnesium behaved remarkably similarly to calcium, and also injected between the graphene and substrate, again ‘floating’ the graphene.

Both magnesium- and calcium-intercalated graphene n-type doped the graphene, and resulted in a low workfunction graphene, an attractive aspect when using graphene as a conducting electrical contact for other materials.

But unlike calcium, magnesium-intercalated graphene remained stable in ambient atmosphere for at least 6 hours, overcoming a major technical hurdle for alkali and alkaline earth intercalated graphene.

“The fact that Mg-QFSBLG is a low workfunction material and n-type dopes the graphene while remaining quite stable in ambient atmosphere is a huge step in the right direction for implementing these novel intercalated materials in technological applications,” explains co-author Prof Michael Fuhrer.

“Magnesium-intercalated graphene could be a stepping stone towards discovery of other similarly stable intercalants.”

Tags:  Electronics  Graphene  Graphite  Jimmy Kotsakidis  Monash University  superconductor 

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Graphene additives show a new way to control the structure of organic crystals

Posted By Graphene Council, Wednesday, September 2, 2020
A team of researchers at The University of Manchester has demonstrated that the surface properties of graphene can be used to control the structure of organic crystals obtained from solution.

Organic crystal structures can be found in a large number of products, such as food, explosives, colour pigments and pharmaceuticals. However, organic crystals can come in different structures, called polymorphs: each of these forms has very different physical and chemical properties, despite having the same chemical composition.

To make a comparison, diamond and graphite are polymorphs because they are composed both by carbon atoms, but they have very different properties because the atoms are bonded to form different structures. The same concept can be extended to organic molecules, when interacting between each other to form crystals.

Understanding and reacting to how materials work on a molecular level is key because the wrong polymorph can cause a food to have a bad taste, or a drug to be less effective. There are several examples of drugs removed from the market because of polymorphism-related problems. As such, production of a specific polymorph is currently a fundamental problem for both research and industry and it does involve substantial scientific and economic challenges.

New research from The University of Manchester has now demonstrated that adding graphene to an evaporating solution containing organic molecules can substantially improve the selectivity towards a certain crystalline form. This opens up new applications of graphene in the field of crystal engineering, which have been completely unexplored so far.

Professor Cinzia Casiraghi, who led the team, said: “Ultimately, we have shown that advanced materials, such as graphene and the tools of nanotechnology enable us to study crystallisation of organic molecules from a solution in a radically new way. We are now excited to move towards molecules that are commonly used for pharmaceuticals and food to further investigate the potential of graphene in the field of crystal engineering."

In the report, published in ACS Nano, the team has shown that by tuning the surface properties of graphene, it is possible to change the type of polymorphs produced. Glycine, the simplest amino acid, has been used as reference molecule, while different types of graphene have been used either as additive or as templates.

Matthew Boyes, and Adriana Alieva, PhD students at The University of Manchester, both contributed to this work: “This is a pioneering work on the use of graphene as an additive in crystallisation experiments. We have used different types of graphene with varying oxygen content and looked at their effects on the crystal outcome of glycine. We have observed that by carefully tuning the oxygen content of graphene, it is possible to induce preferential crystallisation.” said Adriana.

Computer modelling, performed by Professor Melle Franco at the University of Aveiro, Portugal, supports the experimental results and attributes the polymorph selectivity to the presence of hydroxyl groups allowing for hydrogen bonding interactions with the glycine molecules, thereby favouring one polymorph over the other, once additional layers of the polymorph are added during crystal growth.

This work has been financially supported by the European Commission in the framework of the European Research Council (ERC Consolidator), which supports the most innovative research ideas in Europe, by placing emphasis on the quality of the idea rather than the research area, and it is a joint collaboration between the Department of Chemistry and the Department of Chemical Engineering, with Dr Thomas Vetter.

Tags:  ACS Nano  Adriana Alieva  Cinzia Casiraghi  European Research Council  Graphene  graphite  Healthcare  Matthew Boyes  Melle Franco  Thomas Vetter  University of Aveiro  University of Manchester 

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Manchester-led research offers advance in superconductors with a ‘twist’

Posted By Graphene Council, Friday, August 14, 2020
An international research team led by The University of Manchester has revealed a nanomaterial that mirrors the “magic angle” effect originally found in a complex man-made structure known as twisted bilayer graphene – a key area of study in physics in recent years.

The new research shows that the special topology of rhombohedral graphite effectively provides an inbuilt “twist” and therefore offers an alternative medium to study potentially game-changing effects like superconductivity. “It is an interesting alternative to highly popular studies of magic-angle graphene” said graphene pioneer Professor Sir Andre Geim, a co-author of the study.

The team, led by Artem Mishchenko, Professor of Condensed Matter Physics at The University of Manchester published its findings today in the journal Nature.

“Rhombohedral graphite can help to better understand materials in which strong electronic correlations are important - such as heavy-fermion compounds and high-temperature superconductors”, said Professor Mishchenko. 

A previous step-forward in two-dimensional materials research was the curious behaviour that stacking one sheet of graphene atop one another and twisting it to a ‘magic angle’ changed the bilayer’s properties, turning it into a superconductor.

Professor Mishchenko and his colleagues have now observed the emergence of strong electron-electron interactions in a weakly stable rhombohedral form of graphite - the form in which graphene layers stack slightly differently compared to stable hexagonal form.

Interactions in twisted bilayer graphene are exceptionally sensitive to the twist angle. Tiny deviations of about 0.1 degree from the exact magic angle strongly supress interactions. It is extremely difficult to make devices with the required accuracy and, especially, find sufficiently uniform ones to study the exciting physics involved. The newly published findings on rhombohedral graphite has now opened an alternative route to accurately making superconductor devices.

Graphite, a carbon material made up of stacked graphene layers, has two stable forms: hexagonal and rhombohedral. The former is more stable, and has thus been extensively studied, while the latter is less so.

To better understand the new result, it is important to note that the graphene layers are stacked in different ways in these two forms of graphite. Hexagonal graphite (the form of carbon found in pencil lead) is composed of graphene layers orderly stacked on top of each other. The metastable rhombohedral form has a slightly different stacking order, and this slight difference leads to a drastic change in its electronic spectrum.

Rhombohedral graphite can help to better understand materials in which strong electronic correlations are important - such as heavy-fermion compounds and high-temperature superconductors, Professor Artem Mishchenko.

Previous theoretical studies have pointed to the existence of all kinds of many-body physics in the surface states of rhombohedral graphite – including high-temperature magnetic ordering and superconductivity. These predictions could not be verified, however, since electron transport measurements on the material were completely lacking until now.

The Manchester team has been studying hexagonal graphite films for several years and have developed advanced technologies to produce high-quality samples. One of their techniques involves encapsulating the films with an atomically-flat insulator, hexagonal boron nitride (hBN), which serves to preserve the high electronic quality in the resulting hBN/hexagonal graphite/hBN heterostructures. In their new experiments on rhombohedral graphite, the researchers modified their technology to preserve the fragile stacking order of this less stable form of graphite.

The researchers imaged their samples, which contained up to 50 layers of graphene, using Raman spectroscopy to confirm that the stacking order in the material remained intact and that it was of high quality. They then measured electronic transport properties of their samples in the traditional way - by recording the resistance of the material as they changed the temperature and the strength of a magnetic field applied to it.

The energy gap can also be opened in the surface states of rhombohedral graphite by applying an electric field explains Professor Mishchenko: “The surface-state gap opening, which was predicted theoretically, is also an independent confirmation of the rhombohedral nature of the samples, since such a phenomenon is forbidden in hexagonal graphite.”

In rhombohedral graphite thinner than 4nm, a band gap is present even without applying an external electric field. The researchers say they are as yet unsure of the exact nature of this spontaneous gap opening (which occurs at the “charge neutrality”– the point at which densities of electrons and holes are balanced), but the research team are busy working on answering this question.

Further investigation of rhombohedral graphite could shed more light on the origin of many-body phenomena in strongly correlated materials such as heavy-fermion compounds and high-temperature superconductors.

Tags:  Andre Geim  Artem Mishchenko  Graphene  Graphite  superconductor  The University of Manchester 

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Anode Material for Safe Batteries with a Long Cycle Life

Posted By Graphene Council, Monday, August 10, 2020
The demand for electric vehicles is increasing, accompanied by a growing need for smart grids that ensure a sustainable energy supply. These and other mobile and stationary technologies require suitable batteries. Storing as much energy as possible in the smallest possible space with the lowest possible weight – lithium-ion batteries (LIB) still meet this requirement best. The research aims at improving the energy density, power density, safety, and cycle life of these batteries. The electrode material is of major importance here. Anodes of lithium-ion batteries consist of a current collector and an active material applied to it that stores energy in the form of chemical bonds. In most cases, graphite is used as the active material. 

However, negative electrodes made of graphite have a low charging rate. Moreover, they are associated with safety issues. Among the alternative active materials, lithium titanate oxide (LTO) has already been commercialized. Negative electrodes with LTO present a higher charging rate and are considered to be safer than those made of graphite. The drawback is that lithium-ion batteries with lithium titanate oxide tend to have a lower energy density.

The team around Professor Helmut Ehrenberg, head of the Institute for Applied Materials – Energy Storage Systems (IAM-ESS) of KIT, now investigated another highly promising anode material: lithium lanthanum titanate with a perovskite crystal structure (LLTO). According to the study, which was carried out in collaboration with scientists from Jilin University in Changchun (China) and other research institutes in China and Singapore, LLTO anodes have a lower electrode potential compared to commercialized LTO anodes, which allows for a higher cell voltage and a higher capacity. “Cell voltage and storage capacity ultimately determine the energy density of a battery,” explains Ehrenberg. “In the future, LLTO anodes might be used to build particularly safe high-performance cells with a long cycle life.” 

The study contributes to the work of the research platform for electrochemical storage, CELEST (Center for Electrochemical Energy Storage Ulm & Karlsruhe), one of the largest battery research platforms worldwide, which also includes the POLiS excellence cluster.

Besides energy density, power density, safety and cycle life, the charging rate is another determining factor for the suitability of a battery for demanding applications. In principle, the maximum discharge current and the minimum charging time depend on the ion and electron transport both within the solid body and at the interfaces between the electrode and electrolyte materials. To improve the charging rate, it is common practice to reduce the particle size of the electrode material from micro to nano scale. The study, which was published in the Nature Communications journal by KIT researchers and their cooperation partners, shows that even particles of a few micrometers in size in LLTOs with a perovskite structure feature a higher power density and a better charging rate than LTO nanoparticles. The research team attributes this to the so-called pseudocapacitance of LLTO: Not only are individual electrons attached to this anode material, but also charged ions, which are bound by weak forces and can reversibly transfer charges to the anode. “Thanks to the larger particles, LLTO basically enables simpler and more cost-effective electrode manufacturing processes,” explains Ehrenberg.

Tags:  Battery  Graphene  Graphite  Helmut Ehrenberg  Karlsruhe Institute of Technology  Li-ion Batteries 

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Independent University Research Confirms and Quantifies Ease of Conversion of ZEN Graphene’s Albany PureTM Graphite to Graphene

Posted By Graphene Council, Monday, August 10, 2020
ZEN Graphene Solutions is pleased to announce that a recent peer reviewed research article clearly demonstrates that ZEN’s Albany Graphite exfoliates more easily than other commercially available flake graphite test samples. Significantly, this article provides quantitative data that ZEN’s Albany PureTM Graphite has the highest exfoliation rate constant of the materials tested, indicating that it exfoliates more easily than the other materials.

This study was recently published in the peer reviewed journal, Carbon and utilizes an interfacial trapping exfoliation process which is spontaneous and driven by the spreading of graphene at a liquid-liquid interface between two immiscible fluids (e.g. oil and water) and thus lowering the free energy of the system. The article reported “the time to reach full emulsion for the Albany PureTM material was much shorter than for other graphite reference material (Figure 1). The paper also concluded that “the source of the graphite plays a role in the exfoliation in addition to the flake size”. This advantage will likely translate into a more efficient and economic exfoliation process as the company advances towards commercialization.  Additional testing was also conducted to compare the purified East Pipe and West Pipe material and confirmed very similar exfoliation rates for the two pipes as shown in Figure 2 below.

Francis Dubé, ZEN CEO commented, “We have known for a long time that our material exfoliated into graphene faster and better than flake graphite but quantifying it so clearly was a significant confirmation. I want to thank Prof. Douglas Adamson at UConn for his excellent research!”

These results provide additional third-party confirmation that Albany PureTM Graphite exfoliates more easily than other commercially available graphite material and supports the results that were published by Dr. Yoshihiko Arao, Assistant Professor in the Department of Chemical Engineering at Tokyo Tech and reported in an October 16, 2018 news release. In this article, it was reported that the particle size was linked to the ease of producing graphene from graphite through exfoliation – the smaller the feed graphite particle, the easier to exfoliate. The researchers further concluded that, due to the size of its flakes, the exfoliation productivity of graphite derived from ZEN’s Albany PureTM Graphite performed up to 1500% better than the researchers’ reference flake graphite materials. Interestingly, in the UConn study, the ZEN samples had a slightly larger flake size than the other graphite samples, yet still showed faster exfoliation. The company surmises that the turbostratic nature along with the slightly larger d-spacing between the layers were the reason why Albany PureTM Graphite performed better in this study.

Tags:  Francis Dubé  Graphene  Graphite  ZEN Graphene Solutions 

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Outstanding detailed feasibility study results support Talga’s anode project

Posted By Graphene Council, Wednesday, August 5, 2020

Talga is pleased to advise the outcomes of feasibility work and studies completed on its Vittangi Anode Project (“Project”) in northern Sweden.

Talga is building an integrated graphite anode facility in Sweden running on 100% renewable electricity, to produce ultra-low emission coated anode for greener lithium-ion (“Li-ion”) batteries. Production of the Company’s flagship fully coated anode product, Talnode®-C, will be based initially on the unique flake graphite of its Nunasvaara South deposit near Vittangi.

Project development has  been  marked  by  operational  impacts  during  the  COVID-19  pandemic. In consideration of these impacts, the development of the Project will now be combined into a single commercial stage, amalgamating the two stages previously outlined in the Project Pre-feasibility Study (“PFS”). The overall economic and financial parameters for the combined stages remain materially unchanged from the PFS.

Since the publication of the PFS in May 2019 Talga has undertaken further studies into the Talnode-C product, anode production, graphite processing and battery market as part of detailed feasibility work on the Project.

Completed feasibility work on the start-up phase (Stage 1) of the Project show highly positive outcomes which will be refined further in the upcoming commercial Detailed Feasibility Study (“DFS”). Improvements in Project performance identified in the latest feasibility work include:

• Project development to proceed directly to commercial phase with Project commissioning in 2022 and commercial production in 2023, subject to commercial DFS planned for Q1 2021
• Yield of Talnode-C (from graphite concentrate) increased to 99%, up from 88% in PFS
• Total recovery of Talnode-C (from graphite ore) increased to 90%, up from 80% in PFS
• Energy savings of 30% in graphite concentrate production
• Successful piloting of proprietary sustainable purification process producing battery-grade graphite concentrate without use of industry standard hydrofluoric acid (“HF”)
• Ability to produce Talphene graphene products for battery and polymer composite applications from anode refinery stream
• Positive feedback on Talnode-C from major battery manufacturers including high capacity and fast- charge performance during qualification tests
• Refinement of Talnode-C coating treatment based on input from automotive OEM customers
• Pre-production scale Talnode-C pilot plant to satisfy larger automotive OEM qualification process
• Further cost optimisations and growth opportunities identified including resource expansion and underground mining options

The fast track pathway simplifies Project development and enables the Company to progress directly to commercial anode production of 19,000 tonnes per annum (“tpa”) with commencement of construction in 2022 and production in 2023, as outlined in the  PFS.  Talga’s potential Project partners and customers have indicated that they support this plan.

Commenting on the feasibility study results, Talga Managing Director Mark Thompson said: “I credit our staff members and technical partners for their work in realising these significant improvements which span every area of our anode project development. In spite of COVID-19 disruptions our commercial development remains firmly on track thanks to the ingenuity of the Talga team. The great results of the recent feasibility work shows significant benefits to be gained in the short and long term and support the simplified amalgamated development plan.

With increasing demand for Li-ion battery anode sourced from secure and clean supply chains Talga is attracting attention as a potential major anode producer outside China. The range of parties we are engaged with, from product sales to project development partnerships, are truly world-class and well-suited to our project execution strategy. We look forward to sharing more results of these partnerships over the coming months.”

For more information http://www.talgagroup.com/irm/PDF/8e8738bb-527b-4073-9d85-b7db737b468a/Outstandingdetailedfeasibilityresults

Tags:  Battery  Graphene  Graphite  Li-ion Batteries  Mark Thompson  Talga 

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Serendipity broadens the scope for making graphite

Posted By Graphene Council, Monday, July 27, 2020
Described in a research paper published today in Nature’s Communications Materials, the new technique does not require the typical metal catalysts or special raw materials to turn carbon into crystalline graphite. Interestingly it was instead discovered by a research student in a lab, using an Atomic Absorption Spectrometer (AAS) – a piece of equipment, invented in Australia in the 1950s and developed to analyse the composition of liquids.

The Master-level student behind the discovery, Mr Jason Fogg, said that while the exact science behind why this new technique works is still to be confirmed, he believes it relates to the specific way the AAS heats the samples through short fast pulses.

“We used a special furnace that can heat the sample to 3000 degrees Celsius in seconds, something most furnaces cannot achieve,” Mr Fogg said.

“To put the temperature into perspective, 3000 degrees Celsius is equal to about half the surface temperature of the Sun.”

Dr Irene Suarez-Martinez, from Curtin’s School of Electrical Engineering, Computing and Mathematical Sciences, said that while graphite is the most stable form of carbon, most carbon materials stubbornly refuse to turn into graphite, which is why she was absolutely shocked to learn about Mr Fogg’s results.

“When he told me that he created perfect crystalline graphite from a known non-graphitising carbon material, I could not believe it, I was absolutely amazed at the results. It was only when we repeated the results three times that I was convinced,” Dr Suarez-Martinez said.

The most astonishing result involved the polymer polyvinylidene chloride (PVDC), which Dr Suarez-Martinez described as a ‘textbook example’ of a very stubborn material.

As the world’s demand for lithium ion batteries increases, scientists expect the commercial demand for crystalline graphite to also increase, and this research team is now determined to work out the precise details of why this special pulse heating method was so effective.

“Our hypothesis is that atmospheric oxygen soaks into the structure between pulses, and the rapid heating on the next pulses burns away the structures that would usually prevent graphite from forming,” Dr Suarez-Martinez said.

“We’re also interested to see if other complex carbons will also transform. Could this method be able to convert organic carbon material, such as food waste, into crystalline graphite?

“Right now we’re only able to create very small amounts of crystalline graphite, so we are far from being able to reproduce this process on a commercial-level. But we plan to explore our method and hypotheses further.”

The work was performed in collaboration with scientists Professor Peter Harris from the University of Reading in the United Kingdom and Professor Mauricio Terrones from the Pennsylvania State University in the USA, both helping the Curtin University research team confirm their results.

Tags:  Curtin University  Graphene  Graphite  Irene Suarez-Martinez 

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Battery Breakthrough Gives Boost to Electric Flight and Long-Range Electric Cars

Posted By Graphene Council, Wednesday, July 22, 2020
In the pursuit of a rechargeable battery that can power electric vehicles (EVs) for hundreds of miles on a single charge, scientists have endeavored to replace the graphite anodes currently used in EV batteries with lithium metal anodes.

But while lithium metal extends an EV’s driving range by 30–50%, it also shortens the battery’s useful life due to lithium dendrites, tiny treelike defects that form on the lithium anode over the course of many charge and discharge cycles. What’s worse, dendrites short-circuit the cells in the battery if they make contact with the cathode.

For decades, researchers assumed that hard, solid electrolytes, such as those made from ceramics, would work best to prevent dendrites from working their way through the cell. But the problem with that approach, many found, is that it didn’t stop dendrites from forming or “nucleating” in the first place, like tiny cracks in a car windshield that eventually spread.

Now, researchers at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), in collaboration with Carnegie Mellon University, have reported in the journal Nature Materials a new class of soft, solid electrolytes – made from both polymers and ceramics – that suppress dendrites in that early nucleation stage, before they can propagate and cause the battery to fail.

The technology is an example of Berkeley Lab’s multidisciplinary collaborations across its user facilities to develop new ideas to assemble, characterize, and develop materials and devices for solid state batteries.

Solid-state energy storage technologies such as solid-state lithium metal batteries, which use a solid electrode and a solid electrolyte, can provide high energy density combined with excellent safety, but the technology must overcome diverse materials and processing challenges.

“Our dendrite-suppressing technology has exciting implications for the battery industry,” said co-author Brett Helms, a staff scientist in Berkeley Lab’s Molecular Foundry. “With it, battery manufacturers can produce safer lithium metal batteries with both high energy density and a long cycle life.”

Helms added that lithium metal batteries manufactured with the new electrolyte could also be used to power electric aircraft.

A soft approach to dendrite suppression
Key to the design of these new soft, solid-electrolytes was the use of soft polymers of intrinsic microporosity, or PIMs, whose pores were filled with nanosized ceramic particles. Because the electrolyte remains a flexible, soft, solid material, battery manufacturers will be able to manufacture rolls of lithium foils with the electrolyte as a laminate between the anode and the battery separator. These lithium-electrode sub-assemblies, or LESAs, are attractive drop-in replacements for the conventional graphite anode, allowing battery manufacturers to use their existing assembly lines, Helms said.

To demonstrate the dendrite-suppressing features of the new PIM composite electrolyte, the Helms team used X-rays at Berkeley Lab’s Advanced Light Source to create 3D images of the interface between lithium metal and the electrolyte, and to visualize lithium plating and stripping for up to 16 hours at high current. Continuously smooth growth of lithium was observed when the new PIM composite electrolyte was present, while in its absence the interface showed telltale signs of the early stages of dendritic growth.

These and other data confirmed predictions from a new physical model for electrodeposition of lithium metal, which takes into account both chemical and mechanical characteristics of the solid electrolytes.

“In 2017, when the conventional wisdom was that you need a hard electrolyte, we proposed that a new dendrite suppression mechanism is possible with a soft solid electrolyte,” said co-author Venkat Viswanathan, an associate professor of mechanical engineering and faculty fellow at Scott Institute for Energy Innovation at Carnegie Mellon University who led the theoretical studies for the work. “It is amazing to find a material realization of this approach with PIM composites.”

An awardee under the Advanced Research Projects Agency-Energy’s (ARPA-E) IONICS program, 24M Technologies, has integrated these materials into larger format batteries for both EVs and electric vertical takeoff and landing aircraft, or eVTOL.

“While there are unique power requirements for EVs and eVTOLs, the PIM composite solid electrolyte technology appears to be versatile and enabling at high power,” said Helms.

Researchers from Berkeley Lab and Carnegie Mellon University participated in the study.

The Molecular Foundry and Advanced Light Source are DOE Office of Science user facilities co-located at Berkeley Lab.

This work was supported by the Advanced Research Projects Agency–Energy (ARPA-E) and the DOE Office of Science. Additional funding was provided by the DOE Office of Workforce Development for Teachers and Scientists, which enabled undergraduate students to participate in the research through the Science Undergraduate Laboratory Internships program.

Tags:  Battery  Brett Helms  Graphene  graphite  Lawrence Berkeley National Laboratory 

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NETL EXPLORES COAL-BASED CONCRETE ENHANCEMENTS

Posted By Graphene Council, Wednesday, July 22, 2020
Ongoing NETL research into advanced concrete additives could one day revolutionize the construction of bridges and other infrastructure, saving communities money and time while also spurring economic demand for one of the nation’s most abundant and historic resources: coal.

Due to its low cost, versatility, and malleability concrete remains the most popular construction material in the world. However, concrete, at least in its conventional cement paste composition, has several limitations.

These include susceptibility to chemical corrosion from the salts used for deicing roads and deterioration from the freeze-thaw cycles that occur when water penetrates cracks during winter months. Traditional concrete also suffers from lower tensile strength, which is the maximum stress that a material can withstand while being stretched or pulled before breaking. These drawbacks lead to lengthy and costly inspection periods and repairs, often disrupting the flow of traffic and public life in general in the process.

However, a concrete additive containing a carbon nanomaterial called graphene can counter some of these drawbacks due to its excellent mechanical and physical properties. For example, graphene nanomaterials could fill the smallest of cracks within the cement structure as it hardens, increasing the durability and longevity of the structure by preventing salt and water from penetrating the concrete and causing damage.

Over the past three years, NETL has developed the idea of producing graphene materials from coal, marking a significant development because graphene is traditionally sourced from graphite, which is a far more expensive feedstock.

Graphene is an allotrope of the element carbon. This means it possesses the same atoms, but arranged in a different way, giving the material different properties like how diamonds and graphite are both made of carbon but with very different properties. Lightweight, flexible, and thinner than human hair while being several times stronger than steel, graphene possesses tremendous potential for replacing certain materials while enhancing others already in common use such as concrete.

“We have found that coal-based nanomaterials could improve the mechanical properties of cement composite by 20-25 percent and increase resistance to water damage by two orders of magnitude,” explained Yuan Gao, a research scientist leading NETL’s work on graphene enhanced concrete. “We can reach similar levels of improvement regarding concrete’s strength and durability via graphene, but at reduced expense.”

The cost of making graphene concrete additives sourced from graphite remains one of the biggest impediments to widespread commercial use of the material. However, if it could become a mainstay, Gao said this could create more economic activity downstream because coal is more abundant and cheaper to extract.

“Concrete is the most widely used construction material, with 10 billion tons of it produced every year around the world,” she said. “Large-scale application of coal-based carbon nanomaterials in concrete could greatly promote the consumption of domestic coal.”

NETL’s work in graphene-enhanced concrete material is currently at lab scale. NETL’s Christopher Matranga, with the Lab’s Functional Materials Team, said the next step in this leading-edge research is seeking out industry partners for collaboration that can put these materials to the test on a large scale.

“All research we do at NETL is to discover and innovate and then transfer that knowledge and technology to the public by partnering with industrial partners who can develop the technology further and commercialize it,” he said. “Right now, we’re trying to find external partners that would be interested in developing this technology or licensing it. Those are the first big steps in moving toward commercialization.”

Going further into the future, Gao said the Lab also plans to examine the electrical and thermal properties of its composite materials, such as self-sensing and heat management capabilities, which could not only lengthen the lifespan of concrete infrastructure but help engineers more accurately detect damages and stresses. She said NETL plans to explore the use of graphene in other constructional materials, such as asphalt.

Tags:  carbon nanomaterial  Christopher Matranga  Graphene  graphite  National Energy Technology Laboratory  Yuan Gao 

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