本論文對鋰離子電池進行循環壽命實驗，共設計六種不同的循環區間進行360次等效循環，於實驗過程中，每18次等效循環便紀錄電池的當前容量、內阻、端電壓等特性。由容量衰退的情形得知，當放電深度20%時，電池容量衰退較放電深度40%與60%慢，由此驗證，較低的放電深度可以提升電池的循環壽命。在等效循環250次以前，僅有電量狀態0~20%的電池內阻有增加，而在等效循環250次以後，放電深度40%與60%的電池內阻會增加，而放電深度20%的電池內阻不變，此現象說明不同的循環區間會影響電池內阻變化。另外，也觀察到相近當前容量的電池內阻初始值會不同，且會根據放電深度有不同變化，但與當前容量多寡的關係並不明顯。而於放電截止後，電池的電壓會回升且與當前容量相關，但其受到放電開始前的電量狀態影響不大，比電池內阻適合用於檢定當前容量。

In this thesis, the cycle life experiment of lithium-ion batteries is carried out. Six different cycle intervals are designed for 360 full equivalent cycles, and the capacity, internal resistance and terminal voltage of the battery are recorded every 18 full equivalent cycles in the process. It is known from the case that capacity decline slower when the depth of discharge (DOD) is 20%, than the battery capacity decline when the discharge depth is 40% or 60%, which proves that the lower discharge depth can improve the cycle life of the battery. Before the full equivalent cycle of 250 times, the internal resistance of the battery increased only in the SOC is 0~20%, while the internal resistance of the battery increased in the SOC are 30~70% and 20~80% after the equivalent cycle of 250 times, and the other internal resistance didn’t change in the case which DOD is 20%. That means different cycle intervals would cause different change for the internal resistance. The initial values of the internal resistance of the batteries which have similar capacities are different, and will vary according to the depth of discharge, and the relationship with the capacity is not obvious. After the discharge is cut off, the battery voltage rises, which is related to the capacity, and is not affected by the SOC before the start of discharge. The method to estimate the capacity by measuring the terminal voltage of batteries after cutting off the discharge is more suitable than estimating the capacity by the internal resistance.

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