Nanocrystalline TiO₂(B) as Anode Material for Sodium-Ion Batteries

Abstract

High surface area, nanostructured, and phase-pure TiO 2 (B) noodles-like secondary particles were successfully synthesized by a facile one-pot synthesis, based on the hydrolysis of TiCl 3 using a mixture of ethylene glycol and water at moderate temperature. The primary nanoparticles have a uniform size and are about 15 nm in diameter as determined by TEM analysis and exhibit an increased exposure of the (010) facet as indicated by XRD analysis. Unlike the electrochemical reaction with lithium, the application as sodiumion electrode material reveals substantial differences, including the initial amorphization of the TiO 2 (B) particles, accompanied by a partial irreversibility of the sodium storage, presumably related to sodium trapping inside the active material particles and the absence of a stable solid electrolyte interphase, as indicated by galvanostatic cycling and electrochemical impedance spectroscopy, respectively. Besides, TiO 2 (B)-based electrodes show a stabilized reversible capacity of about 100 mAh g −1 and a very good C rate capability. While sodium-ion batteries were initially considered only as lowcost alternative for lithium-ion batteries with a particular focus on their application as stationary energy storage devices, 1-3 recent developments indicated that such devices might provide even similar energy densities in case suitable cathode and anode active materials are combined. [4][5][6] However, particularly regarding the anode side, the identification of long-term stable, environmentally friendly, and abundant active materials, providing high specific capacities and operating at a reasonably low potential, is still considered to be one of the major challenges for this technology. 4,6,7 47 Among these, the best results in terms of specific capacity, long-term cycling stability, and high rate capability were certainly reported for anatase TiO 2 . [40][41][42][43] However, the reversible sodium storage mechanism is obviously different from the classic (de-)insertion mechanism known for lithium, [48][49][50][51][52][53] as an initial reduction of TiO 2 to metallic titanium and an amorphous sodium titanate occurs. 42 TiO 2 (B) is a very well performing anode material for lithium-ion applications, 54-60 but so far -to the best of our knowledge -only one study reported its application as sodium-ion active material. The electrochemical performance, which might be best described by a rather rapid initial capacity fading and a low reversible capacity of about 50 mAh g −1 , is certainly not that promising, 47 although this might be also related to the cut-off potentials of 3.0 and 0.8 V vs. Na/Na + . Besides, the authors observed a rather huge expansion of the (001) 3+ and Ti 4+ at the nanotubes surface, while the general morphology of the tubes remained after sodiation. Consequently, a solid solution mechanism for the reversible sodium ion (de-)insertion comparable to the lithium ion storage mechanism was proposed.Herein, however, we show that TiO 2 (B) -similarly to anatase TiO 2 -presents a rath...

Nitrogen-doped TiO2(B) nanorods as high-performance anode materials for rechargeable sodium-ion batteries

“…9 This phenomenon is obviously different from anatase TiO 2 and hollandite-type TiO 2 , 24,25 however, similar with rutile TiO 2 .…”

“…And then, Wu et al reported a noodle-like nanocrystalline TiO 2 (B) fabricated through hydrolysis of TiCl 3 using a mixture of ethylene glycol and water at moderate temperature for anode materials of SIBs. 9 The reversible capacity of this nanocrystalline TiO 2 (B) can reach to about 100 mA h g À1 at 33.5 mA g À1 over 70…”

“…During the rst cycle, two wide peaks at 0.8 and 0.4 V are observed in the cathodic sweep, and disappeared in the subsequent cycles, which might be associated with the irreversible cathodic decomposition and irreversible side reactions of the electrolyte at the surface of bronze TiO 2 . [8][9][10]23 In the subsequent cycles, only broad and weak redox peaks can be observed during the cathodic and anodic scan, respectively, which are probably related to the reduction of Ti 4+ to Ti 3+ and the subsequent oxidation back to Ti…”

“…The rst coulombic efficiency is calculated to be 45.1%, indicating huge irreversible capacity loss, which is in accordance with most of the TiO 2 anode materials for sodium ion batteries. 13,16,24,25,27,29,31,36 The origin of the initial huge irreversibility of TiO 2 (B) anode materials, recently discussed by Wu et al, 9 may be related to electrolyte decomposition and reorganization of TiO 2 during the initial sodiation. Nevertheless, further studies will have to be carried out in future to dene the detailed reasons for this huge irreversible capacity loss in case of TiO 2 (B).…”

Exploring the Low Voltage Behavior of V2O5Aerogel as Intercalation Host for Sodium Ion Battery

“…22,23 However, their working potential is close to that of metallic sodium, raising serious safety concerns due to the risk of sodium plating, in analogy to graphite in LIBs. Titanium oxides, like Na 2 Ti 3 O 7 24-26 or TiO 2 polymorphs, 27,28 are receiving particular attentions due to their good rate capability and long-term cycle ability. Alloying materials, [29][30][31] or intermetallic compounds 32 offer high delivered capacities (about 400-500 mAh g −1 ).…”