Atomic Layer Fluorination of the Li₄Ti₅O₁₂ Surface: A Multiprobing Survey

Abstract

Li4Ti5O12 (LTO) particles are successfully modified by an atomic layer fluorination process using a one-shot solvent-free synthesis performed with a solid-state fluorinating agent, xenon difluoride, at room temperature. LTO is reported as a promising anode material for lithium-ion batteries (LIBs) where high charging rates and long cycle life are required, because of its high potential preventing lithium dendrite deposition. The fluorination leads to the formation of passivating “LiF” environments at the particle surface using the lowest amount of fluorine reported in the literature. Thanks to a multiprobing strategy, the impact of the fluorination on nonmodified, noncoated LTO has been characterized from the bulk to the extreme surface. The XRD patterns as well as the Raman spectra show no structural modification of the bulk while the combination of the XPS and NMR analysis gives insights about the impact of the fluorination on the entirety of the material. Auger fluorine chemical mapping displays the spatial distribution of a fluorinated layer all around the LTO particles.

Stabilization and Improvement of Energy Storage Performance of High Mass Loading Cobalt Hydroxide Electrode by Surface Functionalization

“…Two components are also detected in the F 1s core peaks one at 686.5 eV for the fluorine in the BF4anions, and the other at 684.3 eV due to chemisorbed fluorine on the material surface. 32 The ratio between the fluorine and the boron assigned to the "BF4 -" environment reaches 3.2. The imidazolium N 1s signal of the cation is well detected at 401.9 eV in accordance with the literature.…”

Electrochemical Oscillation during Galvanostatic Charging of LiCrTiO4 in Li-Ion Batteries

“…The Li 1s peak at ca. 54.7 eV was observed for both samples, as shown in Figure 9a [32]. There are four binding energies: 576.4 eV for Cr 3+ 2p 3/2 , 579.6 eV for Cr 6+ 2p 3/2 , 586.3 eV for Cr 3+ 2p 1/2 and 588.9 eV for Cr 6+ 2p 1/2 , as shown in Figure 9b [33][34][35].…”

Solution‐Based, Anion‐Doping of Li4Ti5O12 Nanoflowers for Lithium‐Ion Battery Applications

“…Specifically, surface fluorination of LTO has been explored to passivate the surface of the material with Li-F moieties to effectively prevent reactions with the electrolyte and to enhance electron conductivity at the surface. [15,20,33] This protocol resulted in a ~12-14% higher initial capacity and a ~9-10% higher Coulombic efficiency as compared with pristine LTO. [15] A combination of Al 3+ and Fdoping yielded better electrochemical performance than either dopant on its own, initially delivering 121 mAh/g at 0.15 mA/cm 2 .…”

“…Nevertheless, for anion doping, [11,[13][14][15][16][17][18][19][20] relatively little work has been previously reported in this field as compared with cation doping, [6,12,21,22] possibly due to the limited choices of anion dopants. Even so, this compound can be readily doped with halides, as implied by the increased number of O 2sites (12) as compared with the corresponding Ti + (5 sites) and Li + (4 sites).…”

“…[23] Moreover, as mentioned previously, based upon the band gap between the O p-state and the empty Ti d-states, substituting oxygen with other anions will induce shifts in the molecular orbital energy, thereby potentially leading to a decrease in the band gap energy. Not surprisingly, it has been previously reported that F -, [13,15,16,[24][25][26][27][28] Cl -, [14] Br -, [17,19,29] and N 3-[18, 29-31] have all been successfully incorporated within LTO nanoscale motifs, such as nanosheets, [32] nanoparticles, [19] and nanospheres. [27] These ions were chosen, because of their similar sizes as compared with O 2-, so as to facilitate the substitution process.…”