scholarly journals Phase Transformation in the Charge-Discharge Process and the Structural Analysis by Synchrotron XAFS and XRD for Nickel Hydroxide Electrode

2008 ◽  
Vol 76 (11) ◽  
pp. 802-807 ◽  
Author(s):  
Masanori MORISHITA ◽  
Seijiro OCHIAI ◽  
Tadashi KAKEYA ◽  
Tetsuya OZAKI ◽  
Yoshiteru KAWABE ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Structural Analysis ◽  
Nickel Hydroxide ◽  
Discharge Process ◽  
Charge Discharge

Single atom catalysts supported on N-doped graphene toward fast kinetic Li−S batteries: a theoretical study

2021 ◽  
Author(s):  
Xu Han ◽  
Zeyun Zhang ◽  
Xuefei Xu
Keyword(s):  
Theoretical Study ◽  
Single Atom ◽  
Discharge Process ◽  
Fast Kinetics ◽  
Shuttle Effect ◽  
Sufficient Stability ◽  
Doped Graphene ◽  
Fast Kinetic ◽  
Kinetics Of ◽  
Charge Discharge

To suppress the shuttle effect of lithium polysulfides and promote fast kinetics of charge−discharge process in Li−S batteries, it is essential to search promising catalysts with sufficient stability and high...

A constitutive model for Fe-based shape memory alloy considering martensitic transformation and plastic sliding coupling: Application to a finite element structural analysis

2012 ◽  
Vol 23 (10) ◽  
pp. 1143-1160 ◽  
Author(s):  
Walid Khalil ◽  
Alain Mikolajczak ◽  
Céline Bouby ◽  
Tarak Ben Zineb
Keyword(s):  
Finite Element ◽  
Phase Transformation ◽  
Structural Analysis ◽  
Shape Memory Alloy ◽  
Constitutive Model ◽  
Shape Memory ◽  
Internal Variables ◽  
Thermomechanical Loading ◽  
Proposed Model ◽  
Numerical Tool

In this article, we propose a finite element numerical tool adapted to a Fe-based shape memory alloy structural analysis, based on a developed constitutive model that describes the effect of phase transformation, plastic sliding, and their interactions on the thermomechanical behavior. This model was derived from an assumed expression of the Gibbs free energy taking into account nonlinear interaction quantities related to inter- and intragranular incompatibilities as well as mechanical and chemical quantities. Two scalar internal variables were considered to describe the phase transformation and plastic sliding effects. The hysteretic and specific behavior patterns of Fe-based shape memory alloy during reverse transformation were studied by assuming a dissipation expression. The proposed model effectively describes the complex thermomechanical loading paths. The numerical tool derived from the implicit resolution of the nonlinear partial derivative constitutive equations was implemented into the Abaqus® finite element code via the User MATerial (UMAT) subroutine. After tests to verify the model for homogeneous and heterogeneous thermomechanical loadings, an example of Fe-based shape memory alloy application was studied, which corresponds to a tightening system made up of fishplates for crane rails. The results we obtained were compared to experimental ones.

Pulse Electrodeposition of α-Nickel Hydroxide with Flower-Like Nanostructure for Supercapacitors

2011 ◽  
Vol 230-232 ◽  
pp. 429-434 ◽  
Author(s):  
Zheng You ◽  
Xiao Feng Wang ◽  
Kui Shen ◽  
Xiang Hua Kong
Keyword(s):  
Specific Capacitance ◽  
Discharge Capacity ◽  
Nickel Hydroxide ◽  
Pulse Electrodeposition ◽  
Electrochemical Measurements ◽  
Electrochemical Tests ◽  
Electrodeposition Method ◽  
Off Time ◽  
Maximum Specific Capacitance ◽  
Charge Discharge

Nickel hydroxide electrodes with flower-like structure were prepared by pulse electrodeposition method. The samples were characterized by XRD, SEM and electrochemical measurements. XRD results show a typical characteristics of α-Ni(OH)2. SEM results show the morphology can be controlled by the ratio between on-time (Ton) and off-time (Toff). If Ton is constant to 10s, a flower-like structure will be obtained when Toff is bigger than 20s. Electrochemical tests revealed that the Nickel hydroxide electrodes prepared atTon=10 s and Toff = 30s not only has higher discharge capacity but also exhibits superior stability of capacity during charge-discharge cycling. The maximum specific capacitance in the first cycle is 737.74 F/g and their specific capacitance become stable after cycling 20 times.

scholarly journals Two-Electron Reaction without Structural Phase Transition in Nanoporous Cathode Material

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Tomoyuki Matsuda ◽  
Yutaka Moritomo
Keyword(s):  
Phase Transition ◽  
Cathode Material ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Discharge Process ◽  
Charge Capacity ◽  
High Charge ◽  
Valence States ◽  
X Ray Absorption ◽  
Charge Discharge

We investigated the charge/discharge properties, valence states, and structural properties of a nanoporous cathode materialLixMn[Fe(CN)6]0.83·3.5H2O. The film-type electrode ofLixMn[Fe(CN)6]0.83·3.5H2Oexhibited a high charge capacity(=128 mAh g-1)and a good cyclability (87% of the initial value after 100 cycles) and is one of the promising candidates for Li-ion battery cathode. X-ray absorption spectra near the Fe and Mn K-edges revealed that the charge/discharge process is a two-electron reaction; that is,MnII–NC–FeII,MnII–NC–FeIII, andMnIII–NC–FeIII. We further found that the crystal structure remains cubic throughout the charge/discharge process. The lattice constant slightly increased during the[FeII(CN)6]4-/[FeIII(CN)6]3-oxidization reaction while decreased during theMnII/MnIIIoxidization reaction. The two-electron reaction without structural phase transition is responsible for the high charge capacity and the good cyclability.

scholarly journals Lithium-Rich Cobalt-Free Manganese-Based Layered Cathode Materials for Li-Ion Batteries: Suppressing the Voltage Fading

Energies ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3487
Author(s):  
Ashraf Abdel-Ghany ◽  
Ahmed M. Hashem ◽  
Alain Mauger ◽  
Christian M. Julien
Keyword(s):  
Layered Structure ◽  
Performance Enhancement ◽  
Electrochemical Impedance ◽  
Discharge Process ◽  
High Porosity ◽  
Li Ion Batteries ◽  
Hydrothermal Route ◽  
Li Ion ◽  
Fading Rate ◽  
Charge Discharge

Lithium-rich layered oxides are recognized as promising materials for Li-ion batteries, owing to higher capacity than the currently available commercialized cathode, for their lower cost. However, their voltage decay and cycling instability during the charge/discharge process are problems that need to be solved before their practical application can be envisioned. These problems are mainly associated with a phase transition of the surface layer from the layered structure to the spinel structure. In this paper, we report the AlF3-coating of the Li-rich Co-free layered Li1.2Ni0.2Mn0.6O2 (LLNMO) oxide as an effective strategy to solve these problems. The samples were synthesized via the hydrothermal route that insures a very good crystallization in the layered structure, probed by XRD, energy-dispersive X-ray (EDX) spectroscopy, and Raman spectroscopy. The hydrothermally synthesized samples before and after AlF3 coating are well crystallized in the layered structure with particle sizes of about 180 nm (crystallites of ~65 nm), with high porosity (pore size 5 nm) determined by Brunauer–Emmett–Teller (BET) specific surface area method. Subsequent improvements in discharge capacity are obtained with a ~5-nm thick coating layer. AlF3-coated Li1.2Ni0.2Mn0.6O2 delivers a capacity of 248 mAh g−1 stable over the 100 cycles, and it exhibits a voltage fading rate of 1.40 mV per cycle. According to the analysis from galvanostatic charge-discharge and electrochemical impedance spectroscopy, the electrochemical performance enhancement is discussed and compared with literature data. Post-mortem analysis confirms that the AlF3 coating is a very efficient surface modification to improve the stability of the layered phase of the Li-rich material, at the origin of the significant improvement of the electrochemical properties.

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