Tailoring the Electric Double Layer for Advanced Rechargeable Batteries: Mechanisms, Strategies, and Outlook.

The structure of the electric double layer (EDL) at the electrode/electrolyte interface functions not only as the physical arena for electrochemical reactions, but also as the fundamental determinant of battery kinetics, interface stability, and cycle life. Although the solid electrolyte interphase (SEI)/cathode electrolyte interphase (CEI) film has been extensively studied, the microstructure and macroscopic performance of the EDL as precursor to interfacial film formation lacks systematical elucidation. This review aims to provide a comprehensive overview of the theoretical evolution of EDL models alongside their pivotal roles and regulation strategies in advanced batteries. We first retrace the development from classical Helmholtz models to modern microscopic theories. Subsequently, we delve into distinct regulation mechanisms and strategies tailoring EDL chemistry across various rechargeable battery systems such as Li-based, Zn-based and other metal-ion batteries. These approaches encompass electrolyte optimization, electrode engineering, interface modification, and external field regulation, intending to suppress side reactions, guide uniform metal deposition, and stabilize electrode interfaces. Furthermore, advanced techniques for simulating and characterizing the microstructure of the EDL are discussed. Finally, the review outlines current challenges and forward-looking perspectives on multidimensional rational design, data-driven screening, operando characterizations, and applications under extreme conditions, providing theoretical guidelines for interface engineering of next-generation batteries.