鋰離子電池之極限放電速率的模擬研究

Mathematical Modeling of Limiting Discharge Rate in Lithium-Ion Battery

吳光耀(Guang-Yao Wu)

指導教授 ： 顏溪成

國立臺灣大學/工學院/化學工程學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.01434

摘要

中文摘要
在本論文中，主要是利用質傳、電荷平衡以及反應動力學的理論來研究鋰離子電池在放電過程中的極限放電速率。
首先，以平均反應速率的概念提出簡化的模型，並且透過此模型針對 10Ah 的大型鋰離子動力電池進行模擬，並在模擬的過程中，探討造成鋰離子電池極限放電速率的可能原因。經過理論的分析可以得到，電池的中止條件有固相質傳的飽和時間、電解液相的鋰離子濃度等於0時、還有電池的電位等於截止電壓時以及最後所放出的電容量等於極限電容量或者是放電的時間到達所定義的極限時間，然後經由簡化模型的計算以及限制條件的判斷可以得到該電池的極限放電速率。
第二，探討電池在不同內部阻抗下的極限電流，利用簡化的模型以及極限放電速率的定義，計算出不同電池內阻條件下的極限放電電流。結果發現當電池內阻較大時，其極限放電速率會越小；但是當電池內阻越小時，計算所得到的極限放電速率則會較大。
最後，針對電池參數對於極限放電速率的影響進行討論，透過孔隙度以及隔離膜厚度變化的模擬，發現在較高的孔隙度下其極限的放電速率也較大，但是孔隙度的增加卻會大大的降低電池的電容量，因此可以從模擬的數據整理出一個最適化的範圍。至於隔離膜的厚度則是與極限放電速率成反比的變化情形，也就是說當隔離膜的厚度越厚其極限的放電速率會越小。

關鍵字

鋰離子電池 ； 數學模擬 ； 極限放電速率

並列摘要

In this thesis, the limiting discharge rate of lithium-ion battery was studied via fundamental equations which included mass transfer, charge conservation, and reaction kinetics. The general model also developed through these theories.
First of all, the charge transfer reaction was uniform that the general model can be simplified. And the limiting discharge rate for 10Ah lithium-ion battery was investigated. The modeling results showed that the limiting rate occurred for four reasons: (1) the time of solid state diffusion reaches saturated (2) the lithium-ion concentration in the electrolyte is very close to zero (3) the cut off voltage is set at 2.8V (4) the discharge time or capacity reaches the limit values.
Second, the limiting discharge rate for different internal resistance was calculated by simplified model and limitations. And increasing the internal resistance decreases the limiting discharge rate.
Finally, the effects of porosity and separator thickness were studied systematically. The modeling results represented that increasing porosity resulted in increasing limiting rate and decreasing capacity. Moreover, there was an inverse relationship between separator thickness and limiting rate. Therefore, the optima porosity and separator thickness were calculated by simplified model.

並列關鍵字

lithium-ion battery ； mathematical modeling ； limiting discharge rate

參考文獻

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