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Sodium Storage and Transport Properties in Layered Na 2 Ti 3 O 7 for Room‐Temperature Sodium‐Ion Batteries
Author(s) -
Pan Huilin,
Lu Xia,
Yu Xiqian,
Hu YongSheng,
Li Hong,
Yang XiaoQing,
Chen Liquan
Publication year - 2013
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201300139
Subject(s) - materials science , overpotential , electrolyte , electrochemistry , anode , sodium , ion , sodium ion battery , activation energy , vacancy defect , analytical chemistry (journal) , electrode , chemical engineering , chemistry , crystallography , metallurgy , faraday efficiency , chromatography , engineering , organic chemistry
Layered sodium titanium oxide, Na 2 Ti 3 O 7 , is synthesized by a solid‐state reaction method as a potential anode for sodium‐ion batteries. Through optimization of the electrolyte and binder, the microsized Na 2 Ti 3 O 7 electrode delivers a reversible capacity of 188 mA h g −1 in 1 M NaFSI/PC electrolyte at a current rate of 0.1C in a voltage range of 0.0–3.0 V, with sodium alginate as binder. The average Na storage voltage plateau is found at ca. 0.3 V vs. Na + /Na, in good agreement with a first‐principles prediction of 0.35 V. The Na storage properties in Na 2 Ti 3 O 7 are investigated from thermodynamic and kinetic aspects. By reducing particle size, the nanosized Na 2 Ti 3 O 7 exhibits much higher capacity, but still with unsatisfied cyclic properties. The solid‐state interphase layer on Na 2 Ti 3 O 7 electrode is analyzed. A zero‐current overpotential related to thermodynamic factors is observed for both nano‐ and microsized Na 2 Ti 3 O 7 . The electronic structure, Na + ion transport and conductivity are investigated by the combination of first‐principles calculation and electrochemical characterizations. On the basis of the vacancy‐hopping mechanism, a quasi‐3D energy favorable trajectory is proposed for Na 2 Ti 3 O 7 . The Na + ions diffuse between the TiO 6 octahedron layers with pretty low activation energy of 0.186 eV.