This study succeeded to prepare three pure phases of Mn 2 O 3 , Mn 3 O 4 beside one of the best cathode materials, spinel LiMn 2 O 4 . LiMn 2 O 4 with high phase purity and crystallinity was synthesized by a facile, cost effective and one step synthesis method. The structure and morphology of the powders were studied in detail by means of X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM) and surface area. The X-ray diffraction shows that the post-annealing process reveals the formation of pure crystalline spinel LiMn 2 O 4 with small particle size and lower lattice strain. The thermogravimetric analysis threw the light on the role of the evaporation technique in producing LiMn 2 O 4 by following the different phases on the thermal performance of the precursor. The morphological characterization shows the clear appearance of the octahedral particles of LiMn 2 O 4 calcined at high temperature with microporous nanosized structure. Electrochemical testing of the as prepared spinel at 900 °C showed promising results in terms of high initial capacity and good cycle stability. The as prepared spinel sample shows also good rate performance.
In this work, the properties of silver-modified LiMn2O4 cathode materials are revisited. We study the influence of calcination atmosphere on the properties of the Ag-coated LiMn2O4 (Ag/LMO) and highlight the silver oxidation. The effect of the heat treatment in vacuum is compared with that in air by the characterization of the structure, specific surface area, Li transport properties and electrochemical performance of Ag/LMO composites. Surface analyses (XPS and Raman spectroscopy) show that the nature of the coating (~3 wt.%) differs with the calcination atmosphere: Ag/LMO(v) calcined in vacuum displays Ag nanospheres and minor AgO content on its surface (specific surface area of 4.1 m2 g−1), while Ag/LMO(a) treated in air is mainly covered by the AgO insulating phase (specific surface area of 0.6 m2 g−1). Electrochemical experiments emphasize that ~3 wt.% Ag coating is effective to minimize the drawbacks of the spinel LiMn2O4 (Mn dissolution, cycling instability, etc.). The Ag/LMO(v) electrode shows high capacity retention, good cyclability at C/2 rate and capacity fade of 0.06% per cycle (in 60 cycles).
Surface coating has become an effective approach to improve the electrochemical performance of Ni-rich cathode materials. In this study, we investigated the nature of an Ag coating layer and its effect on electrochemical properties of the LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode material, which was synthesized using 3 mol.% of silver nanoparticles by a facile, cost-effective, scalable and convenient method. We conducted structural analyses using X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy, which revealed that the Ag nanoparticle coating did not affect the layered structure of NCM811. The Ag-coated sample had less cation mixing compared to the pristine NMC811, which could be attributed to the surface protection of Ag coating from air contamination. The Ag-coated NCM811 exhibited better kinetics than the pristine one, which is attributed to the higher electronic conductivity and better layered structure provided by the Ag nanoparticle coating. The Ag-coated NCM811 delivered a discharge capacity of 185 mAh·g−1 at the first cycle and 120 mAh·g−1 at the 100th cycle, respectively, which is better than the pristine NMC811.
Elemental doping for substituting lithium or oxygen sites has become a simple and effective technique to improve the electrochemical performance of layered cathode materials. Compared with single-element doping, this work presents an unprecedented contribution to the study of the effect of Na+/F- co-doping on the structure and electrochemical performance of LiNi1/3Mn1/3Co1/3O2. The co-doped Li1-zNazNi1/3Mn1/3Co1/3O2-zFz (z = 0.025) and pristine LiNi1/3Co1/3Mn1/3O2 materials were synthesized via the sol–gel method using EDTA as a chelating agent. Structural analyses, carried out by X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy, revealed that the Na+ and F- dopants were successfully incorporated into the Li and O sites, respectively. The co-doping resulted in larger Li-slab spacing, a lower degree of cation mixing, and the stabilization of the surface structure, which substantially enhanced the cycling stability and rate capability of the cathode material. The Na/F co-doped LiNi1/3Mn1/3Co1/3O2 electrode delivered an initial specific capacity of 142 mAh g−1 at a 1C rate (178 mAh g−1 at 0.1C), and it maintained 50% of its initial capacity after 1000 charge–discharge cycles at a 1C rate.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.