There is a growing litany of research efforts aimed at improving the ubiquitous lithium-ion (Li-ion) battery with nanomaterials, and graphene is increasingly taking up the Li-ion’s share of those efforts.
However, one of the issues with exotic nanomaterials trying to take the place of graphite as the storage material for these batteries’ electrodes is cost. Whatever benefit may be derived from using nanomaterials seems to be offset by their rather steep comparative cost.
Now researchers at Lawrence Livermore National Laboratory (LLNL) have discovered that if they use a graphene produced in a low-temperature process that is full of defects, they can still make it a highly effective electrode material simply by treating it with hydrogen.
In research published in the journal Nature Scientific Reports, the LLNL researchers found that the hydrogen interacts with defects in the graphene in a way that opens up gaps that make it easier for the lithium to penetrate the material and thereby improves its transport. Further, the hydrogen goes to the edges of the electrodes; this improves the lithium binding in these areas and ends up boosting storage capacity.
The positive role of hydrogen in this research is a bit unusual since it usually is regarded as an unwanted byproduct of the chemical production of graphene.
“We found a drastically improved rate capacity in graphene nanofoam electrodes after hydrogen treatment,” said LLNL scientist Brandon Wood, one of the co-authors of the paper, in a press release. “By combining the experimental results with detailed simulations, we were able to trace the improvements to subtle interactions between defects and dissociated hydrogen. This results in some small changes to the graphene chemistry and morphology that turn out to have a surprisingly huge effect on performance.”
The researchers believe this research shows that controlled hydrogen treatment could be a way forward to optimize lithium transport as well as improve the storage capacity in other graphene-based anode materials.
“The performance improvement we’ve seen in the electrodes is a breakthrough that has real world applications,” said Jianchao Ye, the lead author of the paper, in the press release.
Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.