兩種電動車用電池系統之性能比較及其對可靠度分析之影響

Abstract

隨著電動車市場的迅速發展，電池技術的創新成為一個關鍵性議題，它直接影響電動車性能、續航力以及使用成本。電動車電池在歷經數個充放電循環後，電容量會逐漸降低，導致車輛失效風險上升。汽車製造商都致力於研究開發新型電池，以滿足不斷增長的電動車市場需求。電動車電池系統(battery system)是由多顆電池芯(battery cell)根據不同排列方式所組成，它不僅影響車輛動力輸出和續航能力，也影響車輛安全性與可靠度。電動車過去常用18650電池，然而近幾年，4680電池被視為新的亮點。相較於18650電池，4680電池除尺寸更大外，隨著無極耳(tabless)技術、高鎳三元正極材料、高矽負極材料、乾電極(dry battery electrode)工藝、CTC (cell to chassis)集成技術等發展，使其具有更低電阻、更長續航力、更高能量密度及電容量。本研究旨在探討上述兩種電池性能之差異，並依據可靠度工程(reliability engineering)原理，分析並分別比較兩種電池之電池芯與電池系統可靠度，包括比較兩種電池系統之失效率(failure rate)、平均失效時間(mean time to failure, MTTF)及車廠保固期等重要可靠度指標。本論文主要以電池芯健康度(state-of-health, SOH)衰退為基礎，考量各電池芯健康度可能存在之差異，分析獲得電池芯及電池系統隨充放電循環次數增加導致可能發生之衰退及可能發生之失效機率，藉以探討並比較前述可靠度指標。本論文研究結果顯示，在符合臺灣特定使用情況下，4680電池系統之平均失效時間為18650電池系統之1.3倍，多了3.6年的使用時間。

With the rapid growth of the electric vehicle (EV) market, innovation in battery technology has become a critical issue. After several charge-discharge cycles, the capacity of EV batteries gradually decreases, increasing the risk of vehicle failure. An EV battery system is composed of multiple battery cells arranged in various configurations, affecting not only the vehicle's power output and cruise range but also its safety and reliability. In the past, EVs commonly used 18650 batteries. However, in recent years, 4680 batteries have emerged, offering advantages such as larger size, tabless technology, high-nickel ternary cathode, high-silicon anode, dry electrode processes, and cell-to-chassis (CTC) integration. These advancements result in lower resistance, longer cruise range, higher energy density, and greater capacity. This study aims to explore the performance differences between the aforementioned two types of batteries and also analyze and compare, respectively, the reliabilities of the battery cells and battery systems of both types based on the principles of reliability engineering. This includes comparing reliability indicators such as failure rate, mean time to failure (MTTF), and the warranty period provided by automakers. The main basis for the analysis is the state-of-health (SOH) degradation of battery cells. This study considers possible SOH differences of battery cells, and finds through analysis potential degradation and failure probabilities that may occur as the number of charge-discharge cycles increases. The aforementioned reliability indicators are then explored and compared. The result of this study shows that under specific usage conditions in Taiwan, the mean time to failure for the 4680 battery system is 1.3 times that of the 18650 battery system, providing an additional 3.6 years of use.