Coupling between cathode and anode in hybrid charge storage

As a promising charge storage method, hybrid charge storage has a high energy density, high power density, and long cycle life due to its combination of the mechanisms of secondary batteries and electrochemical capacitors. However, the difference in the charge storage mechanisms of the cathode and anode and thus the strong coupling makes it impossible to match cathode and anode in all situations. Research has investigated cell configuration, material design, electrolyte composition, etc., for matching the cathode and anode of hybrid charge storage devices, but there is no complete understanding and analysis from an electrochemical perspective. To better guide and promote the development of hybrid charge storage, this study discusses the matching and coupling of the anode and cathode from the following aspects, using hybrid capacitors as a typical example and combining the analysis of mainstream electrochemical systems, strategies, and materials. First, the charge storage mechanism and the major problems involved in matching the cathode and anode, as well as the “self-matching” of potential and zero-voltage potential, are considered as the basis of coupling. Second, from the perspective of electrochemical behavior and potential range of electrodes, we analyze the conflicts and correlations in coupling between each match and discuss the problems and solutions faced in specific matching processes. Third, the problem of matching a practical but complex electrochemical system is analyzed from the perspective of the coupling relationship. Fourth, the design and development of hybrid charge storage, ideas for future research, and the use of machine learning for electrode matching and coupling are proposed.