@article{e2fde8ffad6544bfaf43372d050b4109,
title = "Sodium-Ion Intercalation Mechanism in MXene Nanosheets",
abstract = "MXene, a family of layered compounds consisting of nanosheets, is emerging as an electrode material for various electrochemical energy storage devices including supercapacitors, lithium-ion batteries, and sodium-ion batteries. However, the mechanism of its electrochemical reaction is not yet fully understood. Herein, using solid-state 23Na magic angle spinning NMR and density functional theory calculation, we reveal that MXene Ti3C2Tx in a nonaqueous Na+ electrolyte exhibits reversible Na+ intercalation/deintercalation into the interlayer space. Detailed analyses demonstrate that Ti3C2Tx undergoes expansion of the interlayer distance during the first sodiation, whereby desolvated Na+ is intercalated/deintercalated reversibly. The interlayer distance is maintained during the whole sodiation/desodiation process due to the pillaring effect of trapped Na+ and the swelling effect of penetrated solvent molecules between the Ti3C2Tx sheets. Since Na+ intercalation/deintercalation during the electrochemical reaction is not accompanied by any substantial structural change, Ti3C2Tx shows good capacity retention over 100 cycles as well as excellent rate capability.",
keywords = "MXene, Na NMR, intercalation, negative electrode, sodium-ion battery",
author = "Satoshi Kajiyama and Lucie Szabova and Keitaro Sodeyama and Hiroki Iinuma and Ryohei Morita and Kazuma Gotoh and Yoshitaka Tateyama and Masashi Okubo and Atsuo Yamada",
note = "Funding Information: This work was financially supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan, Grant-in-Aid for Specially Promoted Research No. 15H05701. This work was also supported by MEXT, Japan, under the {"}Elements Strategy Initiative for Catalysts and Batteries (ESICB){"}. M.O. was financially supported by the Ministry of Education, Culture, Science and Technology of Japan, Grant-in-Aid for Scientific Research (B) No. 15H03873. M.O. was also supported by the Murata Science Foundation. The X-ray absorption spectroscopy was carried out under the approval of the Photon Factory Program Advisory Committee (Proposal No. 2014G044). The calculations were carried out on the supercomputers in ISSP, The University of Tokyo and Kyushu University through the HPCI Systems Research Project (Proposal No. hp150068). Publisher Copyright: {\textcopyright} 2016 American Chemical Society.",
year = "2016",
month = mar,
day = "22",
doi = "10.1021/acsnano.5b06958",
language = "English",
volume = "10",
pages = "3334--3341",
journal = "ACS Nano",
issn = "1936-0851",
publisher = "American Chemical Society",
number = "3",
}