The Effects of Trace Yb Doping on the Electrochemical Performance of Li‐Rich Layered Oxides

Abstract

Layered lithium‐rich cathode materials are one of the most promising cathode materials owing to their higher mass energy density than the commercial counterparts. A series of trace Yb‐doped lithium‐rich cathode materials Li1.2Mn0.54Ni0.13Co0.13−xYbxO2 (0≤x≤0.050) were synthesized and the effects were investigated by XRD, X‐ray photoelectron spectroscopy, and high‐resolution TEM. The participation of Yb ions in electrochemical reactions and the larger binding energy of Yb−O than M−O (M=Mn, Ni, Co), which expands the lithium layer spacing and stabilizes the oxygen stacking, resulted in excellent performance of materials doped with a limited Yb content (x≤0.005). However, higher doping amounts (x>0.005) significantly increased the charge‐transfer impedance and led to a sharp deterioration in electrochemical performance. The reason lies in the large difference in ionic radius between the transition metals (Mn, Co, and Ni) and Yb. There is an upper limit to the amount of Yb ions in the lattice. If the amount of Yb is higher than the limit, excess Yb ions enter the Li layers instead of staying in the transition‐metal layers or even segregate on the surface and form electrochemically inert oxides.

Advanced Oxygen‐Vacancy Ce‐Doped MoO3 Ultrathin Nanoflakes Anode Materials Used as Asymmetric Supercapacitors with Ultrahigh Energy Density

“…The rare earth (RE) doping engineering is an effective approach to achieve the uniform distribution of oxygen vacancies from the interior of MoO 3 to the exterior surface, modify the electronic structure, and enlarge layer spacing as well as build Mo‐◌‐RE asymmetric sites as highly active redox sites, [ 23 ] which will significantly enhance conductivity, ion transport channel, and electrochemical activity. [ 24–26 ] Different from the transition metal elements, the RE element has a special outer layer 4f electronic structure, large ion radius, low electronegativity, etc. Therefore, RE doping can greatly affect the electronic structure of the material and endow materials with new properties.…”

Modulating Anion Redox Activity of Li1.2Mn0.54Ni0.13Co0.13O2 through Strong Sr–O Bonds toward Achieving Stable Li-Ion Half-/Full-Cell Performance

“…In another strategy, cation doping (Al, Mg, Zr, La, Cr, etc.) was explored to stabilize the bulk lattice structure and increase the Li + kinetics, thereby reducing the voltage fading. − Meanwhile, particle size reduction was also investigated to enhance the rate capability, which could improve the electronic and ionic conductivity. , …”

Dual Substitution Strategy in Co-Free Layered Cathode Materials for Superior Lithium Ion Batteries

“…Regarding substitution with ions of a large radius, some studies have shown that an impurity phase may occur when the substitution concentration is too high . For example, substitution elements aggregate on the surface of the material to form oxides . In XRD results, the (003) peak does not show a significant left shift when the substitution amount is x = 0.047 in comparison with x = 0.029 (Figure (c)), indicating that there may be impurities, such as sodium oxide, when the substitution amount is too large.…”

“…Some researchers believe that the oxidation of anions in the charging process will lead to generation of O 2 and defects. Once the oxygen evolution occurs, the process is irreversible . However, some studies believe that the redox of anions in some materials is reversible.…”