By comparing these features to the Li, it is likely that the oxidation/reduction couple around 3.65/3.4 V is related to Ru redox, but the shape of the curves suggests that Ni2 and Ru4 oxidation might be superimposed.
The structural and electrochemical characterization of LNMO and LNRO compounds reveal three interesting observations: (1) the compounds possess a similar crystal structure, (2) they allow a similar amount of Li removal on the initial charge, but (3) they have remarkably different charge profiles (voltage plateau at 4.55 V for LNMO vs. Given these unique features, LNMO and LNRO might be suitable model compounds to investigate the underlying oxygen activation mechanisms in the high-voltage region.
The above mentioned models consider different transition metals (i.e., 3d, 4d, and 5d) that have different preference for TM-O hybridization might make the complex anionic oxygen redox even more elusive.
Fundamental understanding of anionic oxygen redox is of critical importance to propose effective material design strategy to develop novel materials that harness active oxygen redox.
This difference was even more pronounced in the differential capacity (d Q/d V) plots (Fig. The charge profile of LNMO was characterized by a strong anodic peak at 4.55 V, corresponding to the extended voltage plateau, as well as two weak anodic peaks around 3.8 and 4.1 V.
In comparison, the strong anodic peak in the high-voltage region was absent in the charge profile of LNRO (Fig.
Both LNMO and LNRO exhibit similar X-ray diffraction (XRD) patterns (Fig. Most of the characteristic XRD peaks can be indexed based on R Such structural distortion could be resulted by a small lattice energy difference.
Trace amounts (Gas evolution of LNMO and LNRO by operando DEMS.
Therefore, a similar crystal structure and morphology between the two samples was confirmed using combined synchrotron XRD, TEM, and SEM techniques. Of note, the last 0.2 Li was not removed from both compounds in this study, additional studies regarding the reversible extraction of the final 0.2 Li are needed to understand the origin of this limitation (outside the scope of this study).
First charge–discharge characteristics of LNMO and LNRO.
We first used operando DEMS to monitor any oxygen evolution stemming from the 2 O compensation reaction and quantify the irreversible loss of lattice oxygen as gaseous products, thus probe the extent of irreversibility of any oxygen participation in the charging process. 3) were collected at a current density of 10 m A g.
The higher loading and larger current density accounted for a larger overpotential observed at the beginning of charge for LNRO and LNMO.