Electrolyte additives for Li-ion batteries: classification by elements

Electrolyte solution composition strongly affects the performance of Li-ion batteries in terms of their general electrochemical properties, electrode stability, cycle life, long-term stability (especially at elevated temperatures), and safety. Additives are essential constituents of efficient electrolyte systems for advanced batteries. Their nature and chemical identity are highly diverse, and their modes of action are sometimes not fully understood, seemingly related to "alchemy". Additives play a crucial role in stabilizing interfaces, enhancing cycle life, and significantly improving safety. Here, a wide scope of additives used in rechargeable Li batteries is examined. Various additives are surveyed emphasizing the importance of their functional groups. We examine routes for judicious optimization of electrolyte solutions by selecting suitable additives for improved rechargeable batteries. As there are many types of additives, their judicious classification is very challenging. We suggest herein the classification and specification of important and representative additives by their central elements. A first classification is based on additives with central atoms other than carbon, hydrogen, and oxygen. Then, we mention additives based on unsaturated bonds and/or unstable ring organic molecules. Dual salt systems are also briefly discussed. Finally, we briefly discussed modelling efforts related to additives.