Symmetric Cells as an Analytical Tool for Battery Research: Assembly, Operation, and Data Analysis Strategies

The demand for a better battery in the aspect of performance, cost, and scalability has significantly driven the development of new electrode chemistries. The electrochemical properties of the electrodes are essential to be acquired, in order to validate their potential in practical batteries and to provide useful feedback for further modifications. As one of three basic cell configurations, symmetric cells (a cell format with two identical working electrodes) hold superior advantages in evaluating some key electrode properties, such as reversibility and ionic/electronic transport kinetics. This review highlights the progress in cell assembly, cell operation, and data analysis, which aims to produce highly reliable and valuable results. Although the symmetric cell technique is largely summarized from Li battery research, the general considerations and conclusions are widely applicable to other battery systems, such as Na, K, Mg, and Ca batteries.