• Anions critically influence the formation and repair of the solid electrolyte interphase (SEI) and modulate the electric double layer, directly impacting battery stability and lifespan.
• Anion chemistry regulates the solvation structure of Li-ions, enhancing desolvation kinetics and improving the electrolyte's anti-oxidative properties, which reduces side reactions and extends cycle life.
• Certain anions, such as halogens, impart flame-retardant properties, significantly enhancing battery safety without compromising performance.
• Strategic anion design can alter reaction pathways and accelerate reactions, thereby increasing both energy density and power density of lithium batteries.