| Summary: | 碩士 === 國立中央大學 === 機械工程學系 === 103 === In this work, we consider the transport mechanism of sodium-ion battery, and build one dimensional, two dimensional models. With physical property values obtained from literature, we investigate the effects of various parameters on the electrical characteristics of sodium-ion batteries.
The one dimensional sodium-ion battery model is for the simulation of coin cell. Two dimension sodium-ion battery model is for the simulation of cylinder battery. Computational domain includes current collectors, electrodes and separator. Porous electrode is assumed to be made up of spherical particles. Sodium-ion are transported by diffusion, insertion and de-insertion processes. Numerical calculation are performed using the COMSOL software.
Results show that the more violent of the electrochemical reaction, the more rapidly sodium ion is consumed in the reduction reaction at the positive electrode. When the consumption rate is greater than the rate of sodium ion supply from the negative electrode, the reduction reaction at the positive electrode becomes unstable. Therefore, the discharge rate, electrode diffusion coefficient, the volume fraction of the electrolyte, and conductivity all affect the capacity and stability of a battery. For constant current discharge, properties of negative electrode have greater impact on battery performance than that of positive electrode. This is because sodium ions and electrons are generated at and supplied by the negative electrode.
Spiral wound battery design not only saves battery size, but also significantly enhance the capacity of batteries by the principle of parallel connection. In addition, it can withstand higher discharge rates. Heat released during a chemical reaction comes from the Joule heat and heat transfer associated with entropy change. Because the chemical reaction rate of a sodium ion battery is lower than that of a lithium ion battery, the heat release rate is smaller for the former. Therefore, the temperature change in a sodium-ion battery is smaller than that in a lithium-ion battery for the same discharging time.
|
|---|
