Dielectric Relaxation Studies of the Fast Lithium-Ion Conductor La2/3-xLi3xTiO3 (x=0.06, 0.11)

2012 ◽  
Vol 457-458 ◽  
pp. 1019-1024
Author(s):  
Wei Guo Wang ◽  
Qian Feng Fang ◽  
Gang Ling Hao
Keyword(s):  
Dielectric Relaxation ◽  
Phonon Frequency ◽  
Lithium Ion ◽  
Relaxation Processes ◽  
Ion Diffusion ◽  
Lithium Ions ◽  
Debye Relaxation ◽  
Exponential Factor ◽  
Relaxation Parameters ◽  
Lithium Ion Diffusion

The diffusion processes of lithium ions in La2/3-xLi3xTiO3 (x=0.06, 0.11) compounds were investigated by dielectric relaxation method. Prominent relaxation dielectric loss peaks, peaks P1 and P2 in La0.56Li0.33TiO3 and peaks P3 and P4 in La0.61Li0.18 TiO3, were observed. From the shift of peak position with frequency, the activation energy of 0.36~0.42 eV and the pre-exponential factor of relaxation time in the order of 10-14 ~ 10-13 s were obtained if one assumes Debye relaxation processes. The activation energies of lithium ion diffusion in La2/3-xLi3xTiO3 compounds and the characteristic vibration frequency for the ionic hopping motion are higher than those measured by 7Li nuclear magnetic resonance (NMR) spectroscopy and that of the typical phonon frequency (about 1013Hz). These values of relaxation parameters strongly suggest the existence of interaction between the relaxation species (here lithium ions or vacancies). Basing on the coupling model, the decoupled relaxation parameters of the dielectric relaxation peaks is: P1 (0.14 eV, 2×10-13 s), P2 (0.25 eV, 1.8×10-13 s), P3 (0.17 eV, 4×10-13 s) and P4 (0.3 eV, 2.7×10-13 s). These decoupled parameters are very close to the NMR measurement results and the reciprocal of the typical phonon frequency. Judging from the relaxation parameter of the peaks and combining with the crystallographic characterization, it is suggested that the P1 (P3) and P2 (P4) peaks are associated with the lithium ion diffusion in the ab planes and between the adjacent ab planes, respectively.

Correlation and the mechanism of lithium ion diffusion with the crystal structure of Li7La3Zr2O12 revealed by an internal friction technique

2014 ◽  
Vol 16 (15) ◽  
pp. 7006-7014 ◽  
Author(s):  
X. P. Wang ◽  
Y. X. Gao ◽  
Y. P. Xia ◽  
Z. Zhuang ◽  
T. Zhang ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Impedance Spectroscopy ◽  
Internal Friction ◽  
Transport Mechanism ◽  
Lithium Ion ◽  
Ion Diffusion ◽  
Ac Impedance Spectroscopy ◽  
Lithium Ions ◽  
Ion Conductor ◽  
Lithium Ion Diffusion

The correlation and transport mechanism of lithium ions with the crystal structure of a fast lithium ion conductor Li7La3Zr2O12 are mainly investigated by internal friction (IF) and AC impedance spectroscopy techniques.

Relaxation Model of Lithium Ions in the Garnet-Like Li5La3Bi2O12Lithium-Ion Conductor

2012 ◽  
Vol 184 ◽  
pp. 116-121 ◽  
Author(s):  
Y.X. Gao ◽  
Zhong Zhuang ◽  
H. Lu ◽  
X.P. Wang ◽  
Qian Feng Fang
Keyword(s):  
Relaxation Process ◽  
Point Defect ◽  
Lithium Ion ◽  
Relaxation Mechanism ◽  
Peak Position ◽  
Lithium Ions ◽  
Debye Relaxation ◽  
Exponential Factor ◽  
Ion Conductor ◽  
Defect Relaxation

The relaxation mechanism of lithium ions in Li5La3Bi2O12 electrolyte was investigated by internal friction (IF) method. A prominent relaxation-type IF peak was observed. From the shift of peak position with frequency, the activation energy of E=1.0-1.1 eV and the pre-exponential factor of relaxation time in the order of τ0 =10-25 ~10-18 s were obtained if one assumes a distributed Debye relaxation process. These values of relaxation parameters strongly suggest the existence of interaction between the relaxation species (here lithium ions or vacancies). Basing on the coupling model, the values of E and τ0 were determined as 0.5-0.6 eV and 10-17 ~ 10-15 s, which still deviated from the typical values for point defect relaxation. A new phenomenological model was used to describe the relaxation process, and the values of E and τ0 were determined as 0.46 eV and 3.6×10-14 s, which is in agreement with the typical values for point defect relaxation.

Lithium Ion Diffusion Through Glassy Carbon Plate

1997 ◽  
Vol 496 ◽  
Author(s):  
M. Inaba ◽  
S. Nohmi ◽  
A. Funabiki ◽  
T. Abe ◽  
Z. Ogumi
Keyword(s):  
Diffusion Coefficient ◽  
Glassy Carbon ◽  
Lithium Ion ◽  
Ion Diffusion ◽  
Irreversible Capacity ◽  
Oxidation Current ◽  
Current Curve ◽  
Carbon Plate ◽  
Lithium Ion Diffusion

ABSTRACTThe electrochemical permeation method was applied to the determination of the diffusion coefficient of Li+ion (DLi+) in a glassy carbon (GC) plate. The cell was composed of two compartments, which were separated by the GC plate. Li+ions were inserted electrochemically from one face, and extracted from the other. The flux of the permeated Li+ions was monitored as an oxidation current at the latter face. The diffusion coefficient was determined by fitting the transient current curve with a theoretical one derived from Fick's law. When the potential was stepped between two potentials in the range of 0 to 0.5 V, transient curves were well fitted with the theoretical one, which gaveDLi+ values on the order of 10−8cm2s−1. In contrast, when the potential was stepped between two potentials across 0.5 V, significant deviation was observed. The deviation indicated the presence of trap sites as well as diffusion sites for Li+ions, the former of which is the origin of the irreversible capacity of GC.

scholarly journals The impact of carbon additives on lithium ion diffusion kinetic of LiFePO4/C composites

2019 ◽  
Vol 22 (1) ◽  
pp. 173-179
Author(s):  
Thanh Dinh Duc ◽  
Anh My-Thi Nguyen ◽  
Tru Nhi Nguyen ◽  
Hang Thi La ◽  
Phung My Loan Le
Keyword(s):  
Electrochemical Performance ◽  
Lithium Ion ◽  
Second Phase ◽  
Potential Candidate ◽  
Scale Production ◽  
X Rays ◽  
Ion Diffusion ◽  
Diffusion Kinetic ◽  
The Impact ◽  
Lithium Ion Diffusion

Introduction: LiFePO4/C composites were synthesized via physical mixing assisted solvothermal process. Different kinds of carbon materials were investigated including 0D (carbon Ketjen black), 1D (carbon nanotubes) and 2D (graphene) materials. X-rays diffraction patterns of carbon coated LiFePO4 synthesized by solvothermal was indexed to pure crystalline phase without the emergence of second phase. LiFePO4 platelets and rods were in range size of 80-200 nm and dispersed well in carbon matrix. The lithium ion diffusion kinetics was evaluated through the calculated diffusion coefficients to explore the impact of carbon mixing. Methods: In this work, we studied the structure, morphologies and the lithium ion diffusion kinetic of LiFePO4/C composites for Li-ion batteries. Different characterization methods were used including powder X-rays (for crystalline structure); Transmission Electron Microscopy (for particle and morphologies observation) and Cyclic voltammetry (for electrochemical kinetic study). Results: The study indicated LiFePO4/C composites were successfully obtained by mixing process and the electrochemical performance throughout the calculated diffusion coefficient was significantly improved by adding the carbon types. Conclusion: The excellent ion diffusion was obtained for composites LiFePO4/Ketjen black (KB) and LiFePO4/CNT compared to LiFePO4/Graphene. KB could be a potential candidate for large-scale production due to low-cost, stable and high electrochemical performance.  

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