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Scientists at the University of Manchester have discovered a breakthrough in understanding the use of lithium-ion storage within the thinnest battery anode, composed of only two layers of carbon atoms.
The research, published in Nature Communications, shows an unexpected ‘in-plane staging’ process during lithium intercalation in bilayer graphene, which could lead to advancements in energy storage technologies.
“The ongoing efforts to optimize rechargeable li-ion batteries led to the interest in intercalation of nanoscale layered compounds, including bilayer graphene. Its lithium intercalation has been demonstrated recently,” says the research publication.
Professor of Physics at the University of Manchester, Irina Grigorieva, led the study, which found a much greater level of cooperation between the lattice of lithium ions and the crystal lattice of graphene than previously thought.
Lithium-ion batteries power devices, including smartphones, laptops, and electric vehicles, and store energy, known as ion intercalation. Graphite as an anode material is currently being employed as an essential component. To enhance its performance, the scientists replaced typical graphite anode with bi-layer graphene. They found that lithium-ion intercalation unfolded in four distinct stages, with lithium ions arranging themselves in different orders at each stage.
The study revealed that bi-layer graphene has a lower lithium storage capacity compared to traditional graphite because it less effectively screens interactions between positively charged lithium ions. This leads to stronger repulsion, causing the ions to remain further apart.
While this revelation indicated that bi-layer graphene may not offer higher storage capacity than bulk graphite, the discovery of its unique intercalation process is important for future research.
It also suggests the potential use of atomically thin metals to enhance the screening effect and possibly improve storage capacity in the future.
This pioneering research deepens researchers’ understanding of lithium-ion intercalation and lays the groundwork for developing more efficient and sustainable energy storage solutions.
The superior conductivity, large surface area, and ultrafast Li diffusion in potential ultrathin graphene electrodes would be tempered by a reduced Li storage capacity. This is particularly relevant for dense assemblies of bilayer graphene considered for battery technologies, which could provide a larger storage capacity than the one observed for isolated bilayers.
“We find that bilayer graphene can provide only weaker screening of interionic interactions compared to bulk graphite, so li-ions interact strongly and start repelling each other at longer distances, limiting the storage capacity of bilayer graphene. Another surprising finding is the experimental evidence for highly ordered Li configurations (essentially li-ion superlattices), which is of interest for electronic transport properties,” the report said.
Recently, scientists at the Tokyo Institute of Technology used two lithium-based solid electrolyte chemical compositions to ensure stable ionic movement in millimeter-thick battery electrodes. Solid electrolytes are much stabler than liquid electrolytes. Ryoji Kanno of the institute used argyrodite-type (Li6PS5CI) and Tetragonal Li 10 GeP 2 S 12, abbreviated as LGPS, to increase the complexity of the superionic crystals.
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