Progress in electrochemical engineering of carbon materials and solid electrolyte interphase in lithium and sodium batteries

Lithium and sodium batteries are pivotal for electrochemical energy storage, where the stability of carbon-based anodes and their solid electrolyte interphase (SEI) critically governs battery performance. Carbon materials with high conductivity and tunable microstructure and surface chemistry are widely used as anode materials, whereas the low operating potential inevitably triggers irreversible electrolyte decomposition, forming an SEI that dictates anode passivation and ion transport. As complex (electro)chemical reactions and mass transfer processes converge at the anode/electrolyte interface, an electrochemical engineering understanding of carbon materials and SEI becomes imperative for advancing battery performance. In this review, we first systematically summarize the structural design, energy storage mechanism and scale-up fabrication of graphite, silicon-carbon composites, and hard carbon, elucidating how their inherent surface properties and microstructures govern electrolyte decomposition and SEI formation. Then, we provide an overview of the fundamental properties of the SEI. This is followed by a discussion of the design principles for achieving a stable SEI and a summary of recent advances in its stability regulation. Finally, we offer perspectives on future research directions for carbon materials and the SEI, aiming to accelerate the development of advanced lithium and sodium batteries.