High Capacity Silicon Anodes Enabled by MXene Viscous Aqueous Ink ~ 2D MXene Nanosheets found to be of Fundamental Importance to Electrochemical Energy Storage Field ~ Trinity College, Dublin


Mxene for Silcon anodes 41467_2019_8383_Fig2_HTML

** Contributed from Nature Communications Open Source Article

 

The ever-increasing demands for advanced lithium-ion batteries have greatly stimulated the quest for robust electrodes with a high areal capacity. Producing thick electrodes from a high-performance active material would maximize this parameter. However, above a critical thickness, solution-processed films typically encounter electrical/mechanical problems, limiting the achievable areal capacity and rate performance as a result.

Herein, we show that two-dimensional titanium carbide or carbonitride nano sheets, known as MXenes, can be used as a conductive binder for silicon electrodes produced by a simple and scalable slurry-casting technique without the need of any other additives.

“The nano sheets form a continuous metallic network, enable fast charge transport and provide good mechanical reinforcement for the thick electrode (up to 450μm). Consequently, very high areal capacity anodes (up to 23.3 mAh cm-2) have been demonstrated.” Utilization of Li-ion chemistry to store the energy electro-chemically can address the ever-increasing demands from both portable electronics and hybrid electrical vehicles.

 

Such stringent challenges on the battery safety and lifetime issues require high-performance battery components, with most of the focus being on electrodes or electrolytes with novel nano-structures and chemistries.

However, equally important is the development of electrode additives, which are required to main-tain the electrode’s conductive network and mechanical integrity. Traditionally, electrode additives are made of dual components based on a conductive agent (i.e. carbon black, CB) and a poly-meric binder.

 

While the former ensures the charge transport throughout the electrode, the latter mechanically holds the active materials and CB together during cycling. Although these traditional electrode additives have been widely applied in Li-ion battery technologies, they fail to perform well in high-capacity electrodes, especially those displaying large volume changes.

This is because the polymeric binder is not mechanically robust enough to withstand the stress induced during lithiation/deli-thiation, leading to severe disruption of the conducting networks. This results in rapid capacity fade and poor lifetime.

 

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Conclusion

In summary, the efficient utilization of 2D MXene nanosheets as a new class of conductive binder for high volume-change Si electrodes is of fundamental importance to the electrochemical energy storage field.

The continuous network of MXene nanosheets not only provides sufficient electrical conductivity and free space for accommodating the volume change issue but also well resolves the mechanical instability of Si. Therefore, the combination of viscous MXene ink and high-capacity Si demonstrated here offers a powerful technique to construct advanced nanostructures with exceptional performance.

Of equal importance is that the formation of these high-mass-loading Si/MXene electrodes can be achieved by means of a commercially compatible, slurry-casting technique, which is highly scalable and low cost, allowing for large-area production of high-performance, Si-based electrodes for advanced batteries.

Considering that more than 30 MXenes are already reported, with more predicted to exist, there is certainly much room for further improving the electrochemical performance of such electrodes by tuning the electrical, mechanical and physicochemical properties of this exciting 2D MXene family.

Professor Valeria Nicolosi Trinity UniversityProfessor Valeria Nicolosi 

Professor of Nanomaterials and Advanced Microscopy at Trinity College Dublin

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Researchers make major breakthrough in smart printed electronics


irishresearcProf Jonathan Coleman has fabricated printed transistors consisting entirely of 2-dimensional nanomaterials for the first time. Credit: AMBER, Trinity College Dublin

Researchers in AMBER, the Science Foundation Ireland-funded materials science research centre hosted in Trinity College Dublin, have fabricated printed transistors consisting entirely of 2-dimensional nanomaterials for the first time. These 2D materials combine exciting electronic properties with the potential for low-cost production. This breakthrough could unlock the potential for applications such as food packaging that displays a digital countdown to warn you of spoiling, wine labels that alert you when your white wine is at its optimum temperature, or even a window pane that shows the day’s forecast. The AMBER team’s findings have been published today in the leading journal Science.

This discovery opens the path for industry, such as ICT and pharmaceutical, to cheaply print a host of electronic devices from solar cells to LEDs with applications from interactive smart food and drug labels to next-generation banknote security and e-passports.

Prof Jonathan Coleman, who is an investigator in AMBER and Trinity’s School of Physics, said, “In the future, printed devices will be incorporated into even the most mundane objects such as labels, posters and packaging. Printed electronic circuitry (constructed from the devices we have created) will allow consumer products to gather, process, display and transmit information: for example, milk cartons could send messages to your phone warning that the milk is about to go out-of-date.

We believe that 2D nanomaterials can compete with the currently used for . Compared to other materials employed in this field, our 2D nanomaterials have the capability to yield more cost effective and higher performance printed devices. However, while the last decade has underlined the potential of 2D materials for a range of electronic applications, only the first steps have been taken to demonstrate their worth in printed electronics. This publication is important because it shows that conducting, semiconducting and insulating 2D nanomaterials can be combined together in complex devices. We felt that it was critically important to focus on printing transistors as they are the electric switches at the heart of modern computing. We believe this work opens the way to print a whole host of devices solely from 2D nanosheets.”

Irish researchers make major breakthrough in smart printed electronics
Prof Jonathan Coleman and team have fabricated printed transistors consisting entirely of 2-dimensional nanomaterials for the first time. Credit: AMBER, Trinity College Dublin

Led by Prof Coleman, in collaboration with the groups of Prof Georg Duesberg (AMBER) and Prof. Laurens Siebbeles (TU Delft, Netherlands), the team used standard printing techniques to combine graphene nanosheets as the electrodes with two other nanomaterials, tungsten diselenide and as the channel and separator (two important parts of a transistor) to form an all-printed, all-nanosheet, working transistor.

Printable electronics have developed over the last thirty years based mainly on printable carbon-based molecules. While these molecules can easily be turned into printable inks, such materials are somewhat unstable and have well-known performance limitations. There have been many attempts to surpass these obstacles using alternative materials, such as carbon nanotubes or inorganic nanoparticles, but these materials have also shown limitations in either performance or in manufacturability. While the performance of printed 2D devices cannot yet compare with advanced transistors, the team believe there is a wide scope to improve performance beyond the current state-of-the-art for printed transistors. Smart_Printed

The ability to print 2D nanomaterials is based on Prof. Coleman’s scalable method of producing 2D nanomaterials, including graphene, boron nitride, and tungsten diselenide nanosheets, in liquids, a method he has licensed to Samsung and Thomas Swan. These nanosheets are flat nanoparticles that are a few nanometres thick but hundreds of nanometres wide. Critically, nanosheets made from different materials have electronic properties that can be conducting, insulating or semiconducting and so include all the building blocks of electronics. Liquid processing is especially advantageous in that it yields large quantities of high quality 2D materials in a form that is easy to process into inks. Prof. Coleman’s publication provides the potential to print circuitry at extremely low cost which will facilitate a range of applications from animated posters to smart labels.

Explore further: Scalable 100 percent yield production of conductive graphene inks

More information: “All-printed thin-film transistors from networks of liquid-exfoliated nanosheets” Science (2017). science.sciencemag.org/cgi/doi/10.1126/science.aal4062

Building a Graphene-Based Future for Europe


MIT-Switchable-Graphene-OlivaresGraphene is the strongest, most impermeable and conductive material known to man. Graphene sheets are just one atom thick, but 200 times stronger than steel. The European Union is investing heavily in the exploitation of graphene’s unique properties through a number of research initiatives such as the SEMANTICS project running at Trinity College Dublin.

                          © Mopic – fotolia

It is no surprise that graphene, a substance with better electrical and thermal conductivity, mechanical strength and optical purity than any other, is being heralded as the ‘wonder material’ of the 21stcentury, as plastics were in the 20thcentury.

Graphene could be used to create ultra-fast electronic transistors, foldable computer displays and light-emitting diodes. It could increase and improve the efficiency of batteries and solar cells, help strengthen aircraft wings and even revolutionise tissue engineering and drug delivery in the health sector.

Photo of graphene layers

It is this huge potential which has convinced the European Commission to commit €1 billion to the Future and Emerging Technologies (FET) Graphene Flagship project, the largest-ever research initiative funded in the history of the EU. It has a guaranteed €54 million in funding for the first two years with much more expected over the next decade.

Sustained funding for the full duration of the Graphene Flagship project comes from the EU’s Research Framework Programmes, principally from Horizon 2020 (2014-2020).

The aim of the Graphene Flagship project, likened in scale to NASA’s mission to put a man on the moon in the 1960s, or the Human Genome project in the 1990s, is to take graphene and related two-dimensional materials such as silicene (a single layer of silicon atoms) from a state of raw potential to a point where they can revolutionise multiple industries and create economic growth and new jobs in Europe.

The research effort will cover the entire value chain, from materials production to components and system integration. It will help to develop the strong position Europe already has in the field and provide an opportunity for European initiatives to lead in global efforts to fully exploit graphene’s miraculous properties.

Under the EU plan, 126 academics and industry groups from 17 countries will work on 15 individual but connected projects.

Feeding industry’s hunger for graphene

But this is not the only support being provided by the EU for research into the phenomenal potential of graphene. The SEMANTICS research project, led by Professor Jonathan Coleman at Trinity College Dublin, is funded by the European Research Council (ERC) and has already achieved some promising results.

The ERC does not assign funding to particular challenges or objectives, but selects the best scientists with the best ideas on the sole criterion of excellence. By providing complementary types of funding, both to individual scientists to work on their own ideas, and to large-scale consortia to coordinate top-down programmes, the EU is helping to progress towards a better knowledge and exploitation of graphene.

“It is no overestimation to state that graphene is one of the most exciting materials of our lifetime,” Prof. Coleman says. “It has the potential to provide answers to the questions that have so far eluded us. Technology, energy and aviation companies worldwide are racing to discover the full potential of graphene. Our research will be an important element in helping to realise that potential.”

With the help of European Research Council (ERC) Starting and Proof of Concept Grants, Prof. Coleman and his team are researching methods for obtaining single-atom layers of graphene and other layered compounds through exfoliation (peeling off) from the multilayers, followed by deposition on a range of surfaces to prepare films displaying specific behaviour.

“We’re working towards making graphene and other single-atom layers available on an economically viable industrial scale, and making it cheaply,” Prof. Coleman continues.

“At CRANN, we are developing nanosheets of graphene and other single-atom materials which can be made in very large quantities,” he adds. “When you put these sheets in plastic, for example, you make the plastic stronger. Not only that – you can massively increase its electrical properties, you can improve its thermal properties and you can make it less permeable to gases. The applications for industry could be endless.”

Prof. Coleman admits that scientists are regularly taken aback by the potential of graphene. “We are continually amazed at what graphene and other single-atom layers can do,” he reveals. “Recently it has been discovered that, when added to glue, graphene can make it more adhesive. Who would have thought that? It’s becoming clear that graphene just makes things a whole lot better,” he concludes.

So far, the project has developed a practical method for producing two-dimensional nanosheets in large quantities. Crucially, these nanosheets are already being used for a range of applications, including the production of reinforced plastics and metals, building super-capacitors and batteries which store energy, making cheap light detectors, and enabling ultra-sensitive position and motion sensors. As the number of application grows, increased demand for these materials is anticipated. In response, the SEMANTICS team has scaled up the production process and is now producing 2D nanosheets at a rate more than 1000 times faster than was possible just a year ago.

Read an article in Horizon magazine: ‘Kitchen blender’ graphene could enable printable circuits and sensors – Prof. Jonathan Coleman

Project details

  • Project acronym: SEMANTICS
  • Participants: Ireland (Coordinator)
  • Project reference 258616
  • Total cost: € 1 405 632
  • EU contribution: € 1 405 632
  • Duration: October 2010 – September 2015