Amorphous Vanadium Titanates as a Negative Electrode for Lithium-ion Batteries

Abstract

Amorphous vanadium titanates (aVTOs) are examined for use as a negative electrode in lithium-ion batteries. These amorphous mixed oxides are synthesized in nanosized particles (<100 nm) and flocculated to form secondary particles. The V 5 + ions in aVTO are found to occupy tetrahedral sites, whereas the Ti 4 + ions show fivefold coordination. Both are uniformly dispersed at the atomic scale in the amorphous oxide matrix, which has abundant structural defects. The first reversible capacity of an aVTO electrode (295 mA h g-1) is larger than that observed for a physically mixed electrode (1:2 aV 2 O 5 | aTiO 2 , 245 mA h g-1). The discrepancy seems to be due to the unique four-coordinated V 5 + ions in aVTO, which either are more electron-accepting or generate more structural defects that serve as Li + storage sites. Coin-type Li/aVTO cells show a large irreversible capacity in the first cycle. When they are prepared under nitrogen (aVTO-N), the population of surface hydroxyl groups is greatly reduced. These groups irreversibly produce highly resistive inorganic compounds (LiOH and Li 2 O), leading to increased irreversible capacity and electrode resistance. As a result, the material prepared under nitrogen shows higher Coulombic efficiency and rate capability.

Particle formation mechanisms supported by in situ synchrotron XAFS and SAXS studies: a review of metal, metal-oxide, semiconductor and selected other nanoparticle formation reactions

“…[119][120][121][122][123][124][125][126][127] Amorphous nanoparticles are of interest due to their applications in catalysis, optics, magnetism, bioactivity, electrochemistry, and nanocomposites. [128][129][130][131][132][133][134] In particular, there are cases within the water oxidation catalysis literature where the amorphous materials have produced superior catalytic activity to their crystalline counterparts. 135,136 For the formation of amorphous nanoparticles, there are a limited number of studies that use synchrotron XAFS or SAXS techniques to investigate the local structural changes of what are typically amorphous nanoparticles at least initially.…”

Amorphous anion-rich titanium polysulfides for aluminum-ion batteries

“…However, merely increasing the ion-storage sites is not sufficient to increase the capacity. An adequate number of electrons are also required to attain local neutrality during cycling ( 25 ). It is equally important to improve the local electron-transfer ability of active sites to quickly achieve charge balance, especially for the storage of high–charge density multivalent ions.…”

Atomistic Insights into Lithium Storage Mechanisms in Anatase, Rutile, and Amorphous TiO2 Electrodes

“…Faster lithiation in bronze TiO 2 compared with anatase originates from the presence of open and freely accessible parallel channels on the surface. 19,28 Amorphous metal oxide, including TiO 2 , has recently received increasing attention due to its open structure to accommodate Li + , 29,30 and higher capacities and rate capabilities have been reported for amorphous TiO 2 compared to crystalline TiO 2 . 31,32 Broad lithiation and de-lithiation peaks, resembling more capacitive storage, are observed in cyclic voltammetry (CV) measurements involving amorphous TiO 2 electrodes.…”

“…Crystal structure also determines the rate of Li + migration in TiO 2 . Faster lithiation in bronze TiO 2 compared with anatase originates from the presence of open and freely accessible parallel channels on the surface. , Amorphous metal oxide, including TiO 2 , has recently received increasing attention due to its open structure to accommodate Li + , , and higher capacities and rate capabilities have been reported for amorphous TiO 2 compared to crystalline TiO 2 . , Broad lithiation and de-lithiation peaks, resembling more capacitive storage, are observed in cyclic voltammetry (CV) measurements involving amorphous TiO 2 electrodes. These broader peaks are more evident with amorphous TiO 2 nano-sized structures, which possess more free space on the surface in addition to the open spatial channels in the bulk. , Jiang et al reported that Li + diffusion in amorphous TiO 2 nanotubes is 2 orders of magnitude faster than that in anatase TiO 2 nanotubes .…”