O2 Positive Electrode Research Articles

Microstructural Changes in LiNi0.8Co0.15Al0.05O2 Positive Electrode Material during the First Cycle

The microstructure of LiNi0.8Co0.15Al0.05O2 positive electrode material before and after the first cycle was investigated by scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS). STEM and EELS analysis shows that, before cycling, there are very thin layers of material at grain boundaries that contain a small amount of transition metal ions (particularly Ni) on Li sites. After the first cycle, the thickness of some grain boundary layers increases significantly, accompanied by formation of microcracks at grain boundaries. Also, from the grain interior to the grain boundary, the structure gradually changes from an ordered layer structure (α-NaFeO2-type) to a partially ordered structure and then to a disordered rock-salt structure. We posit that these microstructural changes are primarily responsible for the irreversible capacity during the first cycle.

Degradation of Lithium-Ion Cells Using LiNi0.8Co0.15Al0.05O2 Positive Electrode for BEV and PHEV Applications

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Investigation of the Origin of High-Capacity in Li1.2Mn0.4Fe0.4O2 Positive Electrode Materials Using STEM-EELS

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Design Strategy for the Dispersion of Nanosized Carbon Black and Its Application of Li(Ni1/3Co1/3Mn1/3)O2 Positive Electrode for Lithium-Ion Rechargeable Batteries

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Characterization of the Cation Distribution of Li1.2Mn0.4Fe0.4O2 Positive Electrode Material Synthesized with Two Different Manganese Sources: An Analytical Transmission Electron Microscopy Study

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The Effects of AlF3 Coating on the Performance of Li [ Li0.2Mn0.54Ni0.13Co0.13 ] O2 Positive Electrode Material for Lithium-Ion Battery

-coated materials have been synthesized as positive electrode materials for lithium-ion batteries. The pristine and -coated materials were characterized by X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, and charge–discharge techniques. The electrochemical studies indicated that the -coated showed initial irreversible capacity loss of only compared to for pristine material. Meanwhile, the coated material also exhibited better rate capability and cyclic performance, which has higher capacity retention of 87.9% after at rate at room temperature in comparison with only 67.8% for the pristine one. The functional mechanism of coating on the performance of was also investigated by electrochemical impedance spectroscopy (EIS) and in situ differential electrochemical mass spectrometry (DEMS). EIS analysis indicated that -coated had stable charge transfer resistance . In situ DEMS results revealed that the activity of extracted oxygen species from layered positive electrode material was greatly reduced and the decomposition of the electrolyte was significantly suppressed for -coated . Therefore, more oxygen molecules rather than carbon dioxide were observed in the coated material system. It is demonstrated again that the coating layer played an important role in the stabilization of the electrode/electrolyte interface for the coated material.

Initial Stage of the Delithiation of Li1.2-xMn0.4Fe0.4O2 Positive Electrode Material for Lithium-Ion Batteries Studied by Electron Energy-Loss Spectroscopy

We have investigated initial stage of the delithiation of Li1.2-<I>x</I>Mn0.4Fe0.4O2 nanoparticles by means of transmission electron microscopy and electron energy-loss spectroscopy. It was found that depletion areas with diameters of less than 10 nm are preferentially formed at Fe-rich regions on the particle surfaces. Correlations between redox reactions of transition metal ions and formation of the depletion areas are discussed.

Electrochemical Behavior of LiMn 0.5Ni0.5O2, LiNi0.33Mn0.33Co0.33O2, and LiNi0.40Mn0.40Co0.20O2 Positive Electrodes (Cathodes) for Advanced Lithium-Ion Batteries

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Synthesis, Structure and Electrochemical Properties of LiNi0.33Mn0.33Co0.33O2 Positive Electrode for Rechargeable Lithium Batteries

The layered LiNi0.33Mn0.33Co0.33O2 materials were prepared by wet chemical method using oxalic acid as a polymeric agent. The positive LiNi0.33Mn0.33Co0.33O2 powders were characterized by means of X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and magnetometry. Electrochemical features of LiNi0.33Mn0.33Co0.33O2 positive electrodes were investigated as a function of synthesis conditions, cutoff voltage limit, and C-rate discharge current. Electrochemical properties are discussed in relation with the local structure and morphology of the layered materials.

Initial Stage of the Delithiation of Li1.2-xMn0.4Fe0.4O2 Positive Electrode Material for Lithium-Ion Batteries Studied by Electron Energy-Loss Spectroscopy

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Fe-rich and Mn-rich nanodomains in Li1.2Mn0.4Fe0.4O2 positive electrode materials for lithium-ion batteries

The authors investigated the distribution and local valence states of transition metal ions in a positive electrode material for lithium-ion batteries, Li1.2Mn0.4Fe0.4O2 nanoparticles, by electron energy-loss spectroscopy combined with scanning transmission electron microscopy. The experiments clarified the coexistence of Mn-rich and Fe-rich nanodomains in each single particle, and it is found that Fe-rich nanodomains contain Mn3+ ions which should be active in a redox reaction in spite of previous views of inactive Mn4+ ions in this material. The authors discuss a redox mechanism associated with the nanodomains.

LiNi0.33Mn0.33Co0.33O2 Positive Electrode for Rechargeable Lithium Batteries

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Synthesis and Electrochemical Properties of Layered Li0.9Ni0.45Ti0.55O2

New Li0.9Ni0.45Ti0.55O2 positive electrode materials were synthesized by means of ion exchange from Na0.9Ni0.45Ti0.55O2. Powder X-ray diffraction (XRD) patterns for these materials indicate that they are isostructural with α-NaFeO2. The degree of cation disordering in the material depends critically on the synthesis conditions. Higher temperatures and longer ion-exchange times induce more cation disordering. Surprisingly, the partially disordered phase shows better capacity retention than the least disordered phase. First-principles calculations indicated the poor capacity retention in the least disordered phase could be attributed to the migration of Ti4+ into the Li layer during the electrochemical testing. The Ti4+ migration seems to depend sensitively on the Ni2+−Ti4+ configuration in the transition metal layer. Density of states (DOS) obtained from first-principles calculations indicate that only Ni participates in the electronic conductivity and that the poor conductivity of this material could be a...