Ionic Liquid Mixtures for Supercapacitor Applications: Synergy of Electrochemistry, NMR, and Simulations

不断增长的全球能源需求要求开发新的能源储存技术，以增加可再生能源的能源生产，并从碳氢化合物燃料过渡到电力驱动。纳米多孔电极超级电容器是一种重要的储能技术，具有较高的功率密度和良好的循环性能。然而，与传统电池相比，它们只能提供中等的能量密度，并且在低温下的电化学性能有限。纯净的离子液体(ILS)作为电解液允许较高的工作电压(&gt；3.5V)并提高储能能力，但离子迁移率的降低降低了功率密度，在不影响功率密度的情况下增加储能能力将使这些生态友好型储能系统得到更广泛的应用。最近，很少有研究表明，混合不同的离子液体可以通过扩大电化学窗口和温度范围来改善超级电容器的性能。虽然这些报告令人鼓舞，但对潜在的物理机制还没有深入的了解。许多关键问题仍未得到解答：混合物中的离子属性如何影响离子的整体扩散系数和孔内扩散系数，并最终影响电荷动力学？电化学性能随温度的变化情况如何？如何匹配混合物中的孔大小和离子大小，以最大限度地利用存储的能量？充电过程中碳结构/孔大小与离子动力学之间的关系是什么？这些只是这一领域进一步发展所必需的一些关键问题。我们的项目通过结合电化学、原位核磁共振(核磁共振)测量和分子模拟来解决这些问题。我们将仔细研究电化学性能与性能之间的关系

The ever-growing global energy demand requires developing novel energy-storage technologies to increase energy production from renewable sources and the transition from hydrocarbon-based fuel to electrical drive. Supercapacitors with nanoporous electrodes have emerged as a critical energy-storage technology, offering high power densities and remarkable cyclability. However, they provide only moderate energy densities compared with conventional batteries and limited electrochemical performances at low temperatures. Neat ionic liquids (ILs) as an electrolyte allow high operating voltages (>3.5 V) and boost the energy storage, but the reduced ion mobility lowers the power density.Increasing the energy storage without compromising the power density would make these ecologically-friendly energy storage systems more broadly applicable. Recently, few studies showed that mixing different ILs improves supercapacitor performance by extending the electrochemical window and temperature range. While these reports are encouraging, there is no deep understanding of the underlying physical mechanisms. Many critical questions remain unanswered: How do ion properties in a mixture affect the bulk and in-pore diffusivity of ions and ultimately the charging dynamics? How does the electrochemical performance vary with the temperature? How to match the pore size and ion sizes in a mixture to maximize the stored energy? What is the relationship between the carbon structure/pore sizes and ion kinetics during charging? These are just some of the key issues essential for further development in this field. Our project addresses these questions by combining electrochemistry, in-situ nuclear magnetic resonance (NMR) measurements, and molecular simulations. We will scrutinize how the electrochemical performance is correlated with the properties