Polymer Electrolytes for Rechargeable Lithium/Sulfur Batteries
Ionic electrolytes for Lithium Batteries
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Transcript of Ionic electrolytes for Lithium Batteries
Characterization of Transport Propertiesof Lithium Electrolytes
Marcelo VideaDepartment of ChemistryITESM Campus monterret
Ciudad de México, 4 de agosto de 2005
Seminarios Alessandro Volta
• Introduction
• Characteristics of an ideal electrolyte
• Classification of lithium electrolytes
• Transport properties of electrolytes
• Concluding remarks
Energy storage devices:Secondary batteries
Mitsubishi Eclipse
Lithium batteries:Chemical thermodynamics
Li metalAnode
Cathode
Carbon
Battery under discharge:voltamperometric characteristic
Electrochemical stability
the electrolyte has to be stable against the presence of strongly oxidizing and reducing agents, i.e., cathode and anode materials, respectively.
Electrochemical window > 4.5V
Characteristics of an ideal electrolyte
Characteristics of an ideal electrolyte
High ionic conductivity (σ)
limiting value > 10-3 Scm-1
1.5x10-3 Scm-1
l=100 µmA=100 cm2
R=17 mΩ
Transfer number (tLi+≈1)
Characteristics of an ideal electrolyte
Classification of lithium electrolytes
Transport properties of electrolytesConductivity measurements
Impedance spectroscopy analysis
Conductivity:LiAlCl4-LiIm
Ionic conductivity vs. Temperature:Vogel-Fulcher-Tamman equation
Conductivity vs. Fluidity
fluidity
Angell’s Decoupling Index, R*τ
Structural relaxation time
Ionic relaxation time
At the glass transition temperature
C.A. Angell (1983) Solid State Ionics 9/10, 3
Índice de desacoplamiento, R*τ y transición vítrea
Phase Diagram for Ionic systemsDTA, DSC
Results
Binary systems:LiAlCl4-LiIm
Binary Ionic Liquid:LiAlCl4-LiImAlCl3
Composition region Non-crystallizingIonic system
Conductivity measurements:LiAlCl4-LiImAlCl3
Decoupling Index:LiAlCl4-LiImAlCl3
Interpretation of the results in terms of ionic percolation in a two phase system
Self-Diffusivity Measurements for
7Li
Measurement of Lithium self-diffusionPulsed Field Gradient - NMR
Chemagnetics (7 Tesla)
Spin Echo program
Study of LiAlCl4-LiAlI4
Low temperature behaviour
Conclusions
• The use of binary and ternary systems proves to be a useful strategy in the preparation of glass-forming ionic liquids.
• Tg y Rτ are parameters that characterize the mechanical properties of an ionic electrolyte.
• In the system LiAlCl4-LiImAlCl3 both the phenomenon of double glass transition as the sudden increase in the Rτ value serve as evidence to argue for the existence of two immiscible liquid phases.
• The ratios σcalc/ σexp are in a first approximation a measure of the number of transfer. However, in LiAlCl4 y and in the eutectic LiAlCl4-LiAlI4 , tLi+ ≈1.
Acknowledgements
Fondo de investigación DOE (DEF9039ER45541 )Moltech Corp. Dr. C. Austen AngellDr. Eduardo SánchezDr. Xu Kang