The climate crisis is one of the most important and urgent challenges we face today. Electrochemical technologies such as batteries, powered by abundant and cheap renewable electricity, will play an important role in the clean energy transition. The electrolyte is an indispensable component of any electrochemical system, impacting the electrochemical stability, reaction kinetics and transport properties. However, most efforts in electrochemical research thus far has focused on the electrodes, and there are underexplored opportunities to understand the structure-property-performance of electrolytes. In this seminar, I will discuss my research on electrolytes and electrochemical devices for energy and sustainability. First, I will introduce the high entropy electrolyte, whereby increasing the molecular diversity leads to improved ion transport properties and fast charging capabilities of lithium metal batteries. Second, I will discuss data-driven methods for understanding and designing electrolytes for lithium metal batteries. Lastly, I will introduce the pH-independent redox chemistry, which presents a fundamentally different method for electrochemical pH swing to enable energy-efficient CO2 capture. I will also discuss future opportunities in understanding and designing electrolytes for energy and sustainability applications.