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Size‐Dependent Electrochemical Performance of Monolithic Anatase TiO 2 Nanotube Anodes for Sodium‐Ion Batteries
Author(s) -
Wei Wei,
Valvo Mario,
Edström Kristina,
Nyholm Leif
Publication year - 2018
Publication title -
chemelectrochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 59
ISSN - 2196-0216
DOI - 10.1002/celc.201701267
Subject(s) - anatase , materials science , nanotube , electrochemistry , anode , chemical engineering , amorphous solid , electrode , ion , nanotechnology , sodium , carbon nanotube , catalysis , chemistry , metallurgy , crystallography , organic chemistry , photocatalysis , engineering
Well‐defined, monolithic TiO 2 nanotube thin films have been used as model anode electrodes to study Na‐ion storage in anatase TiO 2 . It is shown that anatase TiO 2 nanotubes with wall thicknesses up to 50 nm can be transformed into amorphous sodium titanate (e. g. Na 0.2 TiO 2 ) nanotubes via an electrochemical activation process at about 0.2 V vs. Na + /Na. Due to the Na + insertion and extraction reactions at about 0.55 and 0.75 V vs. Na + /Na, respectively, the activated TiO 2 nanotubes exhibit reversible capacities of 170 mAh g −1 . For the first time, it is shown that the nanotube length and wall thickness play critical roles in determining the electrochemical performances of this type of electrodes in Na‐ion cells. An excellent rate performance, yielding capacities of about 33 mAh g −1 at 20 C and 161 mAh g −1 at C/5 rates, as well as a capacity retention of more than 97 % after more than 350 cycles, could be achieved with nanotubes with a wall thickness of up to 20 nm. The cycling rate for the nanotubes with a tube length of 4.5 μm should, however, be limited to 1 C to guarantee a cycle life of about 200 cycles.