Measurement of battery electrolyte transport properties: a review

As demand for safer, longer lasting, and more affordable batteries accelerates worldwide, breakthroughs in electrolyte design are central to powering the next generation of battery technologies. Electrolyte transport properties determine the performance, safety, and longevity of rechargeable batteries. Key parameters, such as e.g. diffusion coefficients, describe how ions move through electrolytes and shape interfacial processes that control cell efficiency and stability. A wide array of methods has been developed to measure these properties, each probing transport from different perspectives. Electrochemical techniques such as impedance spectroscopy and pulsed concentration cells provide accessible techniques for fundamental property values. Spectroscopic approaches, including Raman and nuclear magnetic resonance, offer species specific insight into solvation and transport, while emerging spatially resolved optical methods enable direct visualisation of gradients and interfacial dynamics. This review examines the advantages and limitations of the techniques currently advancing the field of transport property measurements in battery electrolytes, and highlights the role of theoretical frameworks such as concentrated solution theory. By integrating diverse measurements with modelling and electrolyte design strategies, transport studies provide a foundation for developing next-generation lithium, sodium, and multivalent batteries.