High-Resolution Surface Analysis on Aluminum Oxide-Coated Li_1.2Mn_0.55Ni_0.15Co_0.1O₂ with Improved Capacity Retention

Abstract

Thin alumina coatings on Li-rich nickel cobalt manganese oxide (Li-rich NCM) particles used as cathode material in Li-ion batteries can improve the capacity retention during cycling. However, the underlying mechanisms are still not fully understood. It is crucial to determine the degree of coverage of the particle’s coating on various length scales from micrometer to nanometer and to link it to the electrochemical properties. Alumina coatings applied on Li-rich NCM by atomic layer deposition or by chemical solution deposition were examined. The degree of coverage and the morphology of the particle coatings were investigated by time-of-flight secondary-ion mass spectrometry (ToF-SIMS), scanning electron microscopy, elemental analysis using inductively coupled plasma optical emission spectrometry, and scanning/transmission electron microscopy. ToF-SIMS allows investigating the coverage of a coating on large length scales with high lateral resolution and a surface sensitivity of a few nanometers. Regardless of the chosen coating route, analytical investigations revealed that the powder particles were not covered by a fully closed and homogenous alumina film. This study shows that a fully dense coating layer is not necessary to achieve an improvement in capacity retention. The results indicate that rather the coating process itself likely causes the improvement of the capacity retention and increases the initial capacity.

Enhancing the Stability of LiNi0.5Mn1.5O4 by Coating with LiNbO3 Solid-State Electrolyte: Novel Chemically Activated Coating Process versus Sol-Gel Method

“…Such a material/uncoated sample (in our case LNMO-800), treated at the same conditions as the coated one, is useful for the reflection of the process influences. Unfortunately, such reference compounds are rarely used [43,44] in the published studies and the published results are not very suitable for us to define the real reason of the discrepancies between our own and published impedance data.…”

Chemical, Structural, and Electronic Aspects of Formation and Degradation Behavior on Different Length Scales of Ni‐Rich NCM and Li‐Rich HE‐NCM Cathode Materials in Li‐Ion Batteries

“…Nanosize twinned structures, acting as a precursor for the spinel-like component, would help explain why the spinel-like component forms faster during cycling in "MS55," where anionic charge compensation is enhanced compared to "CP55-2." To achieve high-energy-density HE-NCM CAMs of good cycling stability, irreversible oxygen release from the surface must be avoided or minimized, e.g., by coating the particles with electrochemically inactive materials, such as Al 2 O 3 [195][196][197][198] or AlF 3 [199][200][201] for example. Furthermore, a high anionic redox contribution realized by a fine dispersed nanostructure should be stabilized in a way that gradual increase of the nanosize twin domain interface (and subsequent transition to a spinel-like phase), causing voltage decay, is suppressed.…”

Upcycling Real Waste Mixed Lithium-Ion Batteries by Simultaneous Production of rGO and Lithium-Manganese-Rich Cathode Material

“…C-rate experiments using rGO were carried out increasing the current after every 10 cycles from 100 to 800 mAh g –1 in a potential range between 0.02 and 2.8 V. Cycling performances of LMR material were investigated by galvanostatic cycling in a potential range between 2.5 and 4.7 V and with a constant current value corresponding to 0.1 C (1 C = 240 mAh g –1 ). 28 For rate capability experiments, current values corresponding to 0.1, 0.2, 0.5, 1, and again 0.1 C were adopted. Finally, a three-electrode configuration “T-cell” using the active material as a working electrode and lithium both as a reference electrode and a counter electrode was assembled for cyclic voltammetry experiments.…”