Mesopores in nonstoichiometric oxides via oxyexsolution and Kirkendall effects

Li, Ming-Yen; Shen, Pouyan; Hwang, Shyh‐Lung

doi:10.1016/j.jeurceramsoc.2006.10.008

Cited by 4 publications

(5 citation statements)

References 17 publications

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“…Other possible explanations for the presence of nanopores include oxide–oxide solid-state reactions between different precursors during compound formation at elevated temperature. In other multicomponent systems, interdiffusion leads to nanovoid formation through the so-called Kirkendall effect. , Of note, nanopores have already been shown to exist in the NiO–CoO-O 2 system, although the actual mechanism of formation is unclear …”

Section: Resultsmentioning

confidence: 99%

The Role of Intragranular Nanopores in Capacity Fade of Nickel-Rich Layered Li(Ni_1–x–yCo_xMn_y)O₂ Cathode Materials

et al. 2019

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Ni-rich layered LiNi1–x–y Co x Mn y O2 (NCM, x + y ≤ 0.2) is an intensively studied class of cathode active materials for lithium-ion batteries, offering the advantage of high specific capacities. However, their reactivity is also one of the major issues limiting the lifetime of the batteries. NCM degradation, in literature, is mostly explained both by disintegration of secondary particles (large anisotropic volume changes during lithiation/delithiation) and by formation of rock-salt like phases at the grain surfaces at high potential with related oxygen loss. Here, we report the presence of intragranular nanopores in Li1+x (Ni0.85Co0.1Mn0.05)1–x O2 (NCM851005) and track their morphological evolution from pristine to cycled material (200 and 500 cycles) using aberration-corrected scanning transmission electron microscopy (STEM), electron energy loss spectroscopy, energy dispersive X-ray spectroscopy, and time-of-flight secondary ion mass spectrometry. Pores are already found in the primary particles of pristine material. Any potential effect of TEM sample preparation on the formation of nanopores is ruled out by performing thickness series measurements on the lamellae produced by focused ion beam milling. The presence of nanopores in pristine NCM851005 is in sharp contrast to previously observed pore formation during electrochemical cycling or heating. The intragranular pores have a diameter in the range between 10 and 50 nm with a distinct morphology that changes during cycling operation. A rock-salt like region is observed at the pore boundaries even in pristine material, and these regions grow with prolonged cycling. It is suggested that the presence of nanopores strongly affects the degradation of high-Ni NCM, as the pore surfaces apparently increase (i) oxygen loss, (ii) formation of rock-salt regions, and (iii) strain-induced effects within the primary grains. High-resolution STEM demonstrates that nanopores are a source of intragranular cracking during cycling.

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Section: Resultsmentioning

confidence: 99%

The Role of Intragranular Nanopores in Capacity Fade of Nickel-Rich Layered Li(Ni_1–x–yCo_xMn_y)O₂ Cathode Materials

et al. 2019

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“…These two alternatives are explored further below. The cavity formation is a type of Kirkendall porosity, 16,20 in which the vacancies left behind by the faster diffusing species coalesce into pores and in this case larger cavities.…”

Section: Resultsmentioning

confidence: 99%

Microcavity Formation in Alumina Using Ti Templates I: Formation Conditions

Goodshaw

Forrester

Hanson

et al. 2009

Journal of the American Ceramic Society

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It has been found that fully enclosed microcavities can be engineered within Al2O3 ceramics using 125 μm diameter Ti wires as templates. A high‐energy milling pretreatment of the alumina causes diffusion of the Ti into the surrounding alumina leaving all of the Kirkendall porosity consolidated into a central cavity. Control experiments using unmilled alumina confirm the necessity of the milling procedure and experiments with different milling media have excluded incidental doping by milling induced contamination as a primary driver of cavity formation. The internal microcavities produced here may lead to new applications in small scale instrumentation and implantable therapeutic devices.

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“…Regarding to the Kirkendall effect on solute expulsion, cation interdiffusion in close-packed oxides was known to cause microcavities such as in the alumina−Ti diffusion couples , and mesopores such as in nonstoichiometric nickel−cobalt oxide via the oxyexsolution and Kirkendall effects . It is not clear whether the { hkl }-specific etch pits have anything to do with Kirkendall pores due to Ti−Al interdiffusion through a close-packed oxygen sublattice.…”

Section: Discussionmentioning

confidence: 99%

“…Regarding to the Kirkendall effect on solute expulsion, cation interdiffusion in close-packed oxides was known to cause microcavities such as in the alumina-Ti diffusion couples 27,28 and mesopores such as in nonstoichiometric nickel-cobalt oxide via the oxyexsolution and Kirkendall effects. 29 It is not clear whether the {hkl}-specific etch pits have anything to do with Kirkendall pores due to Ti-Al interdiffusion through a closepacked oxygen sublattice. In any case, diffusion-induced amorphization as proved experimentally for metal alloys and ceramic composites upon interdiffusion, 30,31 and dislocation avalanche as indicated by abundant dislocations (Figure 6) may account for the amorphization process of the present nanocondensates.…”

Section: Discussionmentioning

confidence: 99%

On the Enhanced Solute Content, Shape, Defect Microstructures, and Optical Properties of Ti-Doped γ-Al₂O₃ Nanocondensates

et al. 2009

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The γ-Al2O3 condensates with increased solid solubility (up to ca. 4 atomic %) of Ti, mainly Ti3+ and minor Ti2+/Ti4+ according to X-ray photoelectron spectroscopy, were synthesized by laser ablation condensation in air. Transmission electron microscopy indicated that the nearly spherical condensates were nano- to submicrometer in size having {111} facets for mutual coalescence to form twin or single crystals. The Ti-doped γ-Al2O3 condensates are vulnerable to electron irradiation by forming pits bound by {111}, {110}, and {001} faces with 0, 1, and 2 periodic bond chain in terms of the edge-shared octahedral, respectively, followed by a polygonization or amorphization/recrystallization process. The incorporation of a higher concentration of dopant and the internal stress, as expected via a dynamic process, account for the Raman shift and UV−visible absorbance of Ti-doped γ-Al2O3 for potential optoelectronic applications.

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Mesopores in nonstoichiometric oxides via oxyexsolution and Kirkendall effects

Cited by 4 publications

References 17 publications

The Role of Intragranular Nanopores in Capacity Fade of Nickel-Rich Layered Li(Ni_1–x–yCo_xMn_y)O₂ Cathode Materials

The Role of Intragranular Nanopores in Capacity Fade of Nickel-Rich Layered Li(Ni_1–x–yCo_xMn_y)O₂ Cathode Materials

Microcavity Formation in Alumina Using Ti Templates I: Formation Conditions

On the Enhanced Solute Content, Shape, Defect Microstructures, and Optical Properties of Ti-Doped γ-Al₂O₃ Nanocondensates

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Mesopores in nonstoichiometric oxides via oxyexsolution and Kirkendall effects

Cited by 4 publications

References 17 publications

The Role of Intragranular Nanopores in Capacity Fade of Nickel-Rich Layered Li(Ni1–x–yCoxMny)O2 Cathode Materials

The Role of Intragranular Nanopores in Capacity Fade of Nickel-Rich Layered Li(Ni1–x–yCoxMny)O2 Cathode Materials

Microcavity Formation in Alumina Using Ti Templates I: Formation Conditions

On the Enhanced Solute Content, Shape, Defect Microstructures, and Optical Properties of Ti-Doped γ-Al2O3 Nanocondensates

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The Role of Intragranular Nanopores in Capacity Fade of Nickel-Rich Layered Li(Ni_1–x–yCo_xMn_y)O₂ Cathode Materials

The Role of Intragranular Nanopores in Capacity Fade of Nickel-Rich Layered Li(Ni_1–x–yCo_xMn_y)O₂ Cathode Materials

On the Enhanced Solute Content, Shape, Defect Microstructures, and Optical Properties of Ti-Doped γ-Al₂O₃ Nanocondensates