電動車汰役電池之使用與生命週期評估

Abstract

為追求2050年淨零碳排的目標，電動車被視為能有效減少溫室氣體排放的途徑，然而作為動力來源的鋰離子電池仍可能造成其他環境衝擊，除了製造、使用與回收階段，由於電池自電動車退役後仍有80%剩餘容量，近年來各國學者指出可新增電池再利用階段，汰役電池在回收前可作為其他場所的備用電力使用，減少製造新電池的環境衝擊。截至今日，儘管台灣已有電動車電池的製造、使用與回收階段生命週期評估相關研究，但對於電池再利用方面並未有所著墨，因此，本研究針對電動車鋰離子電池進行生命週期評估，考量電池的製造、回收階段，並特別聚焦在汰役電池的再利用階段，計算電池再利用能帶來的環境效益。本研究以生命週期評估作為研究方法，使用SimaPro生命週期評估軟體，並採用ReCiPe 2016與IMPACT World+兩種評估方法試圖找出電池帶來的主要環境衝擊與貢獻來源。在電池製造階段中，鎳與鈷金屬為主要的環境衝擊來源，而錳金屬對人體致癌毒性產生較大威脅。至於在電池回收階段，為回收有價金屬，可採用結晶法或電解法進行回收，結果發現兩種回收方法的衝擊熱點皆為硫酸與電力，特別對人體健康衝擊為最，而電解法的電力衝擊又比結晶法為多。因此，在電池回收階段應試圖減少硫酸與電力的使用，以降低環境衝擊。最後在汰役電池再利用階段，本研究根據鋰離子電池充放電測試數據保守估計汰役後的電動車電池可再利用五年，並以此計算不同再利用情境所能取代的新電池製造生產數量。此外，本研究發現將電池再利用可減少因為六價鉻、鎳、砷、鉛、汞等重金屬之使用與排放對人體致癌毒性的影響，也可以降低銅、鋅、鎳、銀、釩等重金屬對淡水與海洋生態毒性的衝擊。除此之外，汰役電池再利用亦可減少製造新電池所帶來的碳排放。綜合上述，為建構低碳永續循環社會，應朝汰役電池再利用以及將使用至生命終期的鋰離子電池妥善回收處理，取回鎳與鈷等有價金屬再利用，以降低天然礦場的開採，提升資源永續利用，實踐循環經濟。To achieve the goal of net zero carbon emissions by 2050, electric vehicles are seen as an effective way to reduce greenhouse gas emissions. However, lithium-ion batteries as a power source can still cause other environmental impacts. In addition to the manufacturing, use and recycling stages, since batteries still have 80% remaining capacity after electric vehicles are retired, scholars in recent years have pointed out that a new battery repurpose stage can be added. Retired batteries can be used as backup power in other places before recycling to reduce manufacturing environmental impact of new batteries. So far, although there have been life cycle assessment studies on the manufacturing, use and recycling stages of electric vehicle batteries in Taiwan, there has been no focus on battery repurpose. Therefore, this study conducted a life cycle assessment on lithium-ion batteries for electric vehicles, taking into account the battery manufacturing and recycling stages, and ultimately the battery reuse stage, are particularly focused on calculating the environmental benefits of battery repurpose.This study uses life cycle assessment as a research method, using SimaPro software, and using two assessment methods, ReCiPe 2016 and IMPACT World+, try to find out the main environmental impacts and contribution sources caused by batteries. During the battery manufacturing stage, nickel and cobalt metals are the main sources of environmental impact, while manganese metal poses a greater threat to human carcinogenic toxicity. As for the battery recycling stage, in order to recover valuable metals, crystallization method or electrolysis method can be used for recycling. It was found that the environmental impact hot spots of both the crystallization method and the electrolysis method are sulfuric acid and electricity, which have the greatest impact on human health. The electrolysis method has more electric impact than the crystallization method. In other words, the use of sulfuric acid and electricity should be reduced during the battery recycling stage to reduce environmental impact. Finally, in the battery repurpose stage, this study estimates that the battery can be repurposed for five years. With this data, the number of batteries required for different reuse scenarios is calculated. Furthermore, this study also found that the repurposing of batteries can reduce the impact of metals such as hexavalent chromium, nickel, arsenic, lead, and mercury on human carcinogenic toxicity, and can also reduce the impact of metals such as copper, zinc, nickel, silver, and vanadium on freshwater and marine ecotoxicity. After considering metal emissions, battery repurposing can also reduce the carbon emissions associated with manufacturing new batteries. Based on the above content, it is shown that repurposed batteries can reduce the environmental impact of nickel and cobalt metals in the manufacturing of new batteries, and the recovery of nickel and cobalt valuable metals in the recycling stage can also reduce the amount of minerals mined in the manufacturing stage and improve the sustainable use of resources.