鈉離子電池電化學與傳輸現象模擬分析;Numerical Analysis of Electrochemical and Transport Phenomenon in Sodium Ion Battery

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題名:	鈉離子電池電化學與傳輸現象模擬分析;Numerical Analysis of Electrochemical and Transport Phenomenon in Sodium Ion Battery
作者:	羅濬辰;Lo,Chun-chen
貢獻者:	機械工程學系
關鍵詞:	鈉離子電池;一維傳輸現象;二維傳輸現象;熱與電化學耦合;數值模擬;sodium-ion battery;one dimensional transport;two dimensional transport;coupled electrochemistry and heat transfer;numerical analysis
日期:	2014-11-07
上傳時間:	2015-03-16 16:00:43 (UTC+8)
出版者:	國立中央大學
摘要:	本研究利用鈉離子電池與鋰離子電池質傳機制的共通點，建立一維等溫鈉離子電池模型、二維等溫鈉離子電池模型及二維熱與電化學耦合鈉離子電池模型，並從以往文獻的實驗參數範圍做各項物理性質的參數測試，探討各項參數在各模型下對於鈉離子電池定電流放電下的影響性。本文建立的一維模型傳輸機制用來探討鈕扣型電池的傳輸現象，二維模型用來探討圓柱型電池的傳輸現象。本文的模型包含集電板、電極與隔膜，多孔電極模型預測則參考Newman學者所做的假設，利用許多球體結構堆疊排列作為電極多孔結構的模型。鈉離子的傳輸現象以擴散方式傳遞，電化學反應由多孔壁面鈉離子通量模擬嵌入或嵌出電極的濃度值。透過商用軟體COMSOL求解本研究的數值模型問題。研究結果顯示電化學反應愈劇烈，正極還原反應消耗的鈉離子速率愈快，當其速率大於由負極產生並傳遞至正極之鈉離子速率時，正極還原反應將受到影響而不穩定，故達截止電壓所放出的電容量愈低。因此放電速率、電極擴散係數、電解液體積分率及導電率皆對電池電容量及穩定性有很大的關係。定電流放電下，負極參數改變較正極影響來大，由於放電過程中，負極需進行氧化反應產生鈉離子與電子，並傳輸至正極，若負極產生鈉離子速率降低或是傳遞速率降低，正極必定因鈉離子濃度降低導致還原反應受到影響。螺旋纏繞式電池設計不但可節省電池體積，並聯的原理可以大幅提升電池之電容量，亦可承受較大的放電速率。電化學反應所產生的熱源包括焦耳熱與熵變化產生的熱，由於鈉離子電池能承受的放電速率比鋰離子電池低，在各項條件下，除非放電時間較長，否則鈉離子電池的溫度變化都較鋰離子電池小。 ;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.
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