Progress and perspectives on reference electrodes for Li-ion batteries

Electrochemical energy storage has become a cornerstone of modern technology, highlighting the need for precise tools to monitor and evaluate cell states in order to design batteries that combine safety with high performance. In lithium-ion batteries (LIBs), reference electrodes (REs) serve as diagnostic probes that enable the measurement of key electrochemical parameters during operation. They make it possible to monitor potential variations of each cell component over cycling and to study the electrode-specific reaction mechanisms that govern battery performance. Despite their value, developing a RE that remains stable, reversible, and minimally polarizable over extended operation continues to be a major challenge for both research and industrial use. This review summarizes the main considerations in RE design, ranging from material composition and structural configuration to activation procedures, and discusses their respective strengths, drawbacks, and prospects for future development in lithium-ion battery systems. • Reference electrodes allow real-time monitoring of electrode potentials. • Key electrochemical mechanisms can be tracked, assisted by reference electrodes. • Designing reliable reference electrodes may help achieve battery-cell longevity. • Systematic validation and modelling are key to assess reference electrode design.