TiO₂(B)/Anatase Composites Synthesized by Spray Drying as High Performance Negative Electrode Material in Li‐Ion Batteries

Abstract

The successful commercialization of batteries containing Li 4 Ti 5 O 12 [1,2] is a clear indication that the smaller energy density of titanate-based negative electrodes caused by their high potential of Li-ion storage (1.5-1.8 V vs. Li/Li + ) can be compensated for, at least for certain applications, by their high safety, stability, and rate capability. The theoretical Li-ion storage capacity of TiO 2 (335 mAh g À1 ) is twice that of Li 4 Ti 5 O 12 (175 mAh g À1 ), thus shifting TiO 2 into the spotlight of research interest. The practical capacity of TiO 2 , however, does not reach the theoretical value, which prevents its commercialization. The electrochemical performance of TiO 2 is limited due to i) sluggish Li-ion diffusivity and ii) poor electrical conductivity. Several approaches to enhance the electrical conductivity of TiO 2 through, for example, carbon [3] or RuO 2[4] coatings, foreign doping, [5,6] frozen native defects, [7] or wiring by means of carbon nanotube networks, [8] and attempts to improve Li-ion diffusion by nanostructuring [9] or mesoporosity [10] were reported. The crystal phase of TiO 2 strongly influences Li-ion diffusivity. [11] The b-phase of TiO 2 [TiO 2 (B)] has shown extremely fast Liion diffusion, [11,12] exhibiting the highest rate capability reported to date. [13,14] The synthesis methods of TiO 2 (B), usually more tedious than those of anatase phase, can be considered as a holdback for its commercial use in Li-ion batteries.In this communication, we report on the excellent Li-ion storage performance of TiO 2 (B)/anatase composites synthesized by a simple and scalable continuous spray-drying process. To the best of our knowledge, the performance of spraydried TiO 2 as negative electrode in Li-ion batteries has not been reported before. Due to the presence of the b-phase in the spray-dried TiO 2 , its electrochemical performance is above state-of-the-art [3][4][5][6][7][8] and only slightly below the best performances of pure and high surface area TiO 2 (B). [13,14] Additionally, Nbdoping of TiO 2 , which has been shown to enhance its electrical conductivity [15] and to improve its Li-ion storage performance, [16] was combined with spray-drying synthesis to further improve the performance of TiO 2 (B)/anatase. Figure 4. Capacity of intercalation (open symbols) and deintercalation (filled symbols) upon cycling (a) at 50C (first 100 cycles) for 1.3 mg cm À2 and (b) at 40C (first 100 cycles) for 4.0 mg cm À2 . Blue squares represent Nb0_600 and red circles Nb1_600. Note that both figures have the same scale: 100 mAh g À1 100 cycles.

Facile Aluminum Reduction Synthesis of Blue TiO2 with Oxygen Deficiency for Lithium‐Ion Batteries

“…9 These strategies are used to shorten the Li + insertion/extraction pathway 10. 11 On the other hand, the electronic conductivity of TiO 2 particles can be substantially enhanced by coating certain conductive components12–14 (e.g., amorphous carbon, silver, and graphene networks) and by doping TiO 2 with foreign elements or defects 15. 16 Recently, the introduction of oxygen deficiencies or Ti 3+ species into TiO 2 has attracted enormous attention.…”

“…[10,11] On the other hand, the electronic conductivityo fT iO 2 particles can be substantially enhanced by coating certain conductive components [12][13][14] (e.g.,a morphous carbon,s ilver,a nd graphene networks) and by dopingT iO 2 with foreign elements or defects. [15,16] Recently,t he introduction of oxygen deficiencies or Ti 3 + speciesinto TiO 2 has attracted enormousa ttention. Oxygen-deficiency/Ti 3 + defects that functiona se lectron capture agentsi nT iO 2 were reported to cause trapped states in the forbidden bandgap, that is, 0.75-1.18 eV away from the conduction band [17,18] and, thus, can improve the electronic conductivity of TiO 2 .S uch am ethod can effectively elude inactiveL i-storage constituents introduced by the complex synthesis route, which is of advantage in the realization of high Li-storage performance with low production costs.H igh-pressure or ambient-pressure hydrogenation methods have been successfully developed as an efficient way to create oxygen deficiencies/Ti 3 + species.…”

Is TiO2(B) the Future of Titanium‐Based Battery Materials?

“…3) Doping of TiO 2 with aliovalent elements, such as niobium, [47][48][49] tin, [50] iron, [51] and nitrogen, [52,53] changesi ts electronic structure leading to the enhancement of the C-rate capability of TiO 2 .4 )TiO 2 can also be doped with native defects (oxygen deficiencies), which leads to highere lectrical conductivity and, thus, improved performance. [52,[54][55][56] Maier and co-workers demonstrated that the Li-ion mobility decreases with increased levels of oxygen deficiency.…”

“…[57][58][59] Specific charge capacities above 160 mA hg À1 have been widely achieved following this strategy. [48,54,[58][59][60][61][62] The C-rate capabilities have also been improved significantly,u pt ov alues of 110mAhg À1 at 10 C. [48,54,60] However,t he strategy of nanostructuring is not flawless since decreasing the particle size leads to low tap densities. As ac onsequence, the volumetric capacity is strongly reduced.…”

Effect of the specific surface area on thermodynamic and kinetic properties of nanoparticle anatase TiO2 in lithium-ion batteries

“…However, it leads to a lower specific energy of the battery. The main drawback of titania materials, which is limiting its electrochemical performance, is the low electrical conductivity, which has been addressed by using carbon additives [4,5] or doping [6,7].…”