Electrolyte additives in Li-ion batteries: from mechanisms to application

Abstract

This article systematically reviews the mechanisms, classifications, and applications of electrolyte additives for lithium-ion batteries. The addition of trace amounts of additives can significantly enhance battery performance, with common types including film-forming agents, flame retardants, acid scavengers, overcharge protectants, and multifunctional composite additives. They play a key role in building a stable SEI/CEI layer at the electrode/electrolyte interface, removing harmful substances (such as HF), regulating the solvation structure of lithium-ions, enhancing thermal stability, and inhibiting dendrite growth. The article discusses in detail the additives containing elements such as boron, phosphorus, sulfur, fluorine, and nitrogen, as well as their synergistic effects. The article also explores emerging directions such as ionic liquids, multifunctional molecules, nanomaterials, polymers, and bio-based additives, and points out the challenges currently faced by additive technologies, including compatibility, mechanism complexity, and long-term effectiveness. It also looks forward to the development prospects of rational design and collaborative strategies for high-voltage, high-energy-density, and solid-state batteries.