應用聚合物電解質之準固態鎂氧氣電池與其相關研究

Abstract

溫室氣體之排放控制為眾人所關注之熱門議題，為減少運輸業造成之廢氣汙染，電動車、無人機等使用電能之新型載具成為近年眾人積極研究開發之項目。當中具高能量密度與高理論開路電壓優勢之可充電鎂氧氣(Mg–O2)電池作為有望替代鋰離子電池以運用於電動載具之新穎技術。 本研究首先合成可運用於Mg–O2電池之聚合物固態電解質並進行分析。藉添加丁二腈(succinonitrile; SN)可達最佳3.9 × 10–5 S cm–1之室溫離子電導率，並藉各式分析儀器揭示SN於聚合物電解質特性之影響，以探討SN與離子電導率之關聯性。其次將合成之聚合物電解質延伸組裝為鈕扣型準固態Mg–O2電池，其可具25000 mAh g–1之最大放電電容量、50圈穩定充放電循環壽命及0.99 V電池過電位等優異之電性表現。若將其組裝為軟包型準固態Mg–O2電池，則可具4.1 mAh cm–2之最大放電電容量，並藉點亮紅光LED展示其應用性。隨後藉各式分析儀器進行陰極界面之成分鑑定，探討準固態Mg–O2電池之反應機制，可得知氧化鎂(MgO)與過氧化鎂(MgO2)皆為主要之放電產物。同時藉各式分析儀器鑑定陽極界面之穩定性，可得知陽極表面不僅無副產物生成，更減少裂縫等缺陷發生，證明聚合物電解質具陽極保護之效果。 本研究之新穎性為使用SN提升聚合物固態電解質之離子電導率，並藉此電解質延伸配製為準固態聚合物型電解質以組裝出可充電Mg–O2電池，使其可具50圈穩定充放電循環壽命表現，並將其組裝為軟包型電池，測試其於環境大氣下運作之電性表現，改善過往鈕扣型金屬空氣電池之缺點以提升其商業實用性。

The control of greenhouse gas emissions grabbed worldwide attention due to global warming. To reduce the exhaust pollution caused by transportation, electric vehicles and drones have been the focus in recent years. Rechargeable batteries with high energy density, such as magnesium–oxygen (Mg–O2) batteries are being explored as an alternative to lithium-ion batteries for electric vehicles. This study synthesized a polymer electrolyte suitable for Mg–O2 batteries. By adding succinonitrile (SN), the ionic conductivity could be optimally enhanced to 3.9 × 10–5 S cm–1 under room temperature. The effect of SN on the properties of the polymer electrolyte was characterized. Subsequently, the polymer electrolyte was assembled into a coin-type quasi-solid-state Mg–O2 battery, exhibiting a maximum discharge capacity of 25000 mAh g–1, stable cycle life of 50 cycles, and an overpotential of 0.99 V. When assembled into a pouch-type Mg–O2 battery, its applicability was demonstrated by lighting up a red LED. Moreover, the cathode interface was characterized to explore the reaction mechanism, revealing that magnesium oxide (MgO) and magnesium peroxide (MgO2) are the main discharge products. Simultaneously, the stability of the anode interface was confirmed, which demonstrated the anode protection effect of the polymer electrolyte. The novelty of this study is the introduction of SN to enhance the ion conductivity of polymer electrolytes, which enables the quasi-solid-state Mg–O2 battery to have a stable cycle life of 50 cycles. Additionally, the pouch-type Mg–O2 batteries were assembled and tested in ambient atmospheric conditions, which provide the possibility for large-scale commercial production.