Ultrafast lithium diffusion in bilayer graphene

• Published in: Nature nanotechnology Vol. 12; no. 9; pp. 895 - 900
• Main Authors: Kühne, Matthias, Paolucci, Federico, Popovic, Jelena, Ostrovsky, Pavel M., Maier, Joachim, Smet, Jurgen H.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-09-2017; Nature Publishing Group
• Subjects: 147/135; 147/3; 639/638/161/891; 639/925/918/1052; Batteries; Bilayers; Conductors; Diffusion coefficient; Diffusion rate; Electrochemistry; Graphene; Hall probes; Ion currents; Lithium; Mass transfer; Materials Science; Nanotechnology; Nanotechnology and Microengineering; Probes; Reaction kinetics; Redox reactions; Sodium chloride; Water
• ISSN: 1748-3387; 1748-3395
• DOI: 10.1038/nnano.2017.108

Solids that simultaneously conduct electrons and ions are key elements for the mass transfer and storage required in battery electrodes. Single-phase materials with a high electronic and high ionic conductivity at room temperature are hard to come by, and therefore multiphase systems with separate ion and electron channels have been put forward instead. Here we report on bilayer graphene as a single-phase mixed conductor that demonstrates Li diffusion faster than in graphite and even surpassing the diffusion of sodium chloride in liquid water. To measure Li diffusion, we have developed an on-chip electrochemical cell architecture in which the redox reaction that forces Li intercalation is localized only at a protrusion of the device so that the graphene bilayer remains unperturbed from the electrolyte during operation. We performed time-dependent Hall measurements across spatially displaced Hall probes to monitor the in-plane Li diffusion kinetics within the graphene bilayer and measured a diffusion coefficient as high as 7×10
–5
 cm
2
s
–1
.
Time-dependent Hall measurements show lithium ions diffuse faster inside bilayer graphene than in graphite by an order of magnitude.