The Fundamentals and Mechanisms of Electrolytes

Batteries, with their high efficiency, are increasingly recognized because of an indispensable function that is used as sustainable energy storage, and versatility, they can also reduce carbon emissions. While lithium-ion batteries (LIBs) currently dominate commercial applications with high energy density and stable cycling performance, their limitations—including material scarcity, safety risks, and limited voltage ranges—have driven exploration into alternative chemistries. This review highlights the structural and mechanistic differences between different kinds of electrolytes, with particular emphasis on the role of electrolytes as a critical component in determining stability, safety, and performance. Electrolytes are composed of salts, solvents, and additives, each playing a distinct role in ion conduction, interfacial stability, and overall efficiency. We further discuss key requirements for electrolytes, including ionic conductivity, electrochemical stability, electrode compatibility, and thermal resistance. Special focus is given to electrolyte design strategies such as the selection of anion species, development of solvent systems, and the use of additives like fluoroethylene carbonate (FEC) and lithium nitrate (LiNO3), which stabilize interfaces and suppress detrimental side reactions. By comparing inorganic and organic systems, this paper provides insights into the mechanisms of ion transport, challenges in electrolyte engineering, and strategies for enabling next-generation batteries with improved energy density, safety, and long-term cycling stability.