An Assistant Professor in mechanical and nuclear engineering at Kansas State University (KSU), Gurpeet Singh, and his student researchers have managed to innovatively demonstrate that a composite 'paper' consisting of interleaved Molybdenum disulfide (MoS2) and Graphene nanosheets can both act as an active material to efficiently store Sodium atoms (Na) as well as act as a flexible current collector
Interestingly the concept is a new structure for Na ion battery technology and represents a discovery of flexible MoS2 electrodes, which could open a new realm on a very promising technology.
Sulfur (S) and Na chemistries are viewed as the most advanced battery technologies in the 21st Century. Their extensive employment is due to their cost-effectiveness, abundance, high cell energy, high cell voltage, durability in recharge cycling, non toxicity, not too heavy, and so suitable for future solid electrolyte optimisation cycles. Na is very attractive, because it can continue to work at ambient temperatures, and for some requirements the cooler the better.
Singh states - "Most negative electrodes for Na ion batteries use materials that undergo an 'alloying' reaction with Na. These materials can swell as much as 400-500% as the battery is charged and discharged, which may result in mechanical damage and loss of electrical contact with the current collector."
Continuing on he stated - "MoS2, the major constituent of the paper electrode, offers a new kind of chemistry with Na ion, which is a combination of intercalation and a conversion type reaction. The paper electrode offers stable charge capacity of 230 mAh.g-1 with respect to total electrode weight. Further, the interleaved the porous structure of the paper electrode offers smooth channels for Na to diffuse in and out as the cell is charged and discharged quickly. This design also eliminates the polymeric binders and Copper (Cu) current collector foil used in a traditional battery electrode."
The study was published in the latest issue of the journal American Chemical Society (ACS) Nano entitled MoS2/Graphene composite paper for Na ion battery electrodes, and the lead author being Lamuel David, a doctoral student in mechanical engineering and Romil Bhandavat, also a recent doctoral graduate.
The research team for the last two years have been developing new methods for quick and cost-effective synthesis of the atomically thin two dimensional (2D) materials of Graphene, Mo and Tungsten (IV) sulfide (WS2), in gram quantities, particularly for rechargeable battery applications.
In their latest research, the engineers have managed to create a large scale composite paper which consisted of acid treated layered MoS2 and chemically modified Graphene in an interleaved structured. Thus, the research marks for the first time that a flexible paper electrode can be used in a Na ion battery as an anode which operates at room temperature (RT). Nowadays most commercial Na-S batteries operate close to 300 degrees Celsius (572 Fahrenheit), as pointed out by Singh.
Singh continues to provide his reasoning on why the research study is important for the effort and affect on to commercialisation. Firstly, by answering that the synthesis of large quantities of single and/or few layer thick 2D materials can be crucial to understanding the true commercial potential of materials, such as transition metal dichalcogenides, TMD and/or Graphene.
Also, the research points out a fundamental requirement for understanding the need for how Na is stored in a layered material through mechanisms other than the conventional intercalation and alloying reaction. Thereafter comes the requirement to workout how employing Graphene as the flexible support and current collector for eliminating the Cu foil and making lighter and bendable rechargeable batteries. Ensuring to have these matters thoroughly explored would set the platform for optimisation and economic investigation.
Singh concludes by stating - "From the synthesis point of view, we have shown that certain transition metal dichalcogenides can be exfoliated in strong acids. This method should allow synthesis of gram quantities of few-layer-think MoS2 sheets, which is very crucial for applications such as flexible batteries, super capacitors and polymer composites. For such applications, TMD flakes that are a few atoms thick are sufficient. Very high quality single layer flakes and not a necessity." Original article available here and Similar article available here
As with similar type USA studies, the future potential of nanomaterials for the battery industry is exponential. As stated previously, DCN Corp strongly believes it can supersede, by providing a dip controlling process which supplements the other attributes of employing S and Na. Going forward, if you and/or your colleagues are interested in making DCN Corp's alternative process reality - please ensure to contact the company as soon as practicably possible.