Reviewed by Lexie CornerSep 9 2024
A research team at the University of Manchester has made a significant breakthrough in understanding lithium-ion storage within the thinnest possible battery anode, composed of just two layers of carbon atoms. Their findings, published in Nature Communications, reveal an unexpected "in-plane staging" mechanism that occurs when lithium intercalates into bilayer graphene. This discovery could lead to advancements in energy storage technology.
Ion intercalation is the process by which lithium-ion batteries, which power devices from electric vehicles to computers and smartphones, store energy. During charging, lithium ions move between layers of graphite, a common material in battery anodes. The more lithium ions that can be added and then removed, the greater the battery's capacity to store and release energy.
Despite being widely recognized, the details of this process remain unclear. The Manchester research team focused on bilayer graphene, the thinnest material that could serve as a battery anode, consisting of just two atomic layers of carbon. Their research sheds new light on the intricacies of ion intercalation.
In their experiments, the researchers replaced the conventional graphite anode with bilayer graphene and observed how lithium ions behaved during the intercalation process. Surprisingly, they found that lithium ions do not randomly intercalate between the two layers or all at once. Instead, the process occurs in four distinct stages, with lithium ions arranging themselves systematically at each stage, forming increasingly dense hexagonal lithium ion lattices.
The discovery of 'in-plane staging' was completely unexpected. It revealed a much greater level of cooperation between the lattice of lithium ions and the crystal lattice of graphene than previously thought. This understanding of the intercalation process at the atomic level opens up new avenues for optimizing lithium-ion batteries and possibly exploring new materials for enhanced energy storage.
Irina Grigorieva, Professor, University of Manchester
The study also revealed that, compared to conventional graphite, bilayer graphene has a lower capacity for storing lithium, though it offers valuable new insights. This reduced capacity is due to weaker screening of the interactions between positively charged lithium ions, leading to greater repulsion and preventing the ions from getting as close.
While this suggests that bulk graphite may outperform bilayer graphene in terms of storage capacity, the discovery of bilayer graphene's unique intercalation mechanism is a significant advancement. Additionally, this discovery raises the possibility of using atomically thin metals to enhance the screening effect, which could potentially increase the storage capacity of future battery materials.
Journal Reference:
Astles, T., et al. (2024) In-plane staging in lithium-ion intercalation of bilayer graphene. Nature Communications. doi.org/10.1038/s41467-024-51196-x,