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Structure and Dynamic Behavior of Sodium–Diglyme Complex in the Graphite Anode of Sodium Ion Battery by 2H Nuclear Magnetic Resonance

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journal contribution
posted on 21.11.2016, 00:00 by Kazuma Gotoh, Hisashi Maruyama, Tatsuya Miyatou, Motohiro Mizuno, Koki Urita, Hiroyuki Ishida
Cointercalation systems consisting of graphite, sodium, and some linear glycol ethers (glymes) are anticipated for use as negative electrodes in sodium ion batteries because of their superior properties such as outstanding cycle performance. We synthesized a ternary intercalation compound consisting of sodium, deuterated diglyme (diglyme-d14), and graphite by a solution reaction. Then we investigated the dynamics and coordination structure of diglyme-d14 molecules by 2H solid-state NMR. Two diglyme molecules coordinate to each sodium ion rigidly, except for rotation of the methyl groups at low temperatures below 233 K. At room temperature, diglyme weakly coordinates to a Na ion through one oxygen atom of the ligand and rotates around the O–Na axis. The active motion of sodium–diglyme complexes is favorable for Na diffusion between graphene layers in the graphite intercalation compound.