Elucidation of the reaction mechanism upon lithiation and delithiation of Cu_0.5TiOPO₄

Abstract

The reaction mechanism of Cu0.5TiOPO4 upon lithiation and delithiation was elucidated by XAS, 31P-NMR, XRD, EDX, and electrochemical methods. The material reacts with a combined insertion and conversion process, forming first LiTiOPO4 + Cu. Afterwards, Ti4+ is reduced reversibly in an insertion reaction followed by a conversion reaction leading to amorphisation while titanium is reduced below 2+.

In situ X-ray diffraction characterisation of Fe0.5TiOPO4 and Cu0.5TiOPO4 as electrode material for sodium-ion batteries

“…In the desodiation and the following cycles this fades to ≈70 mAh/g (Figure 4), which is much lower than the one obtained with a Li counter electrode (230 mAh/g). In contrary to the lithiation behaviour, there is no potential plateau at ≈1.4 V vs. Na + /Na which would correspond to the reduction of Ti 4+ to Ti 3+ observed at ≈1.7 V vs. Li + /Li [9]. A small amount of the material reacted at this potential but not as much as it would be expected for a reaction with 1 Na + per f.u.. At potentials negative to 0.5 V, the cell with FEC delivers a lower practical specific charge than the cell without.…”

“…Prior to in situ measurement, a careful analysis of structure of the synthetized powders (Fe0.5TiOPO4 and Cu0.5TiOPO4) can be found here [2,9]. A summary of those data is reported in the supplementary material.…”

Electrochemical characterizations of Co0.5TiOPO4 as anode material for lithium-ion batteries

“…According to the previous work on this family of materials like Ni 0.5 TiOPO 4 , Fe 0.5 TiOPO 4 and Cu 0.5 TiOPO 4 [18,23,28,29], the first large discharge capacity is related to the Ti 4 þ ions reduction to Ti 3 þ and Ti 2 þ , in parallel with the Co 2 þ reduction to Co°. In addition, the electrolyte decomposition occurring at low voltage and leading to the SEI layer (Solid Electrolyte Interface) formation is another source of the lithium uptake, as confirmed by our group for Ni 0.5 TiOPO 4 /C anode material [23].…”

Single-Shot Multi-keV X-Ray Absorption Spectroscopy Using an Ultrashort Laser-Wakefield Accelerator Source

“…The inset of Fig. 3 depicts the measured absorption profile (solid black curve), our resulting fit (blue dashed curve) with shaded error bars, and the synchrotron reference (red dotted curve) [40]. The error magnitude in the signal region postedge has been reduced by a factor of 2.…”

“…Figure 3 depicts the measured absorption profile for a single shot (solid black curve). It is compared alongside reference data for titanium taken previously at a synchrotron facility [40] (dotted red curve). To facilitate the comparison we have used a standard XANES procedure for normalizing the profile [41].…”