Discovering new electrolyte additives for specific purposes has been a long-run demand for lithium batteries. With the help of the current understanding of failure mechanisms of lithium batteries, it is no longer impossible to have a rational design, instead of random trials, of electrolyte additives for lithium batteries. More excitingly, we have successfully discovered several new electrolyte additives based on chemistry knowledge. Standard characterization tools, such as NMR, MS, SEM, and XPS, are enough to verify the proposed design rules for these electrolyte additives.

Phosphorus pentoxide (P2O5) is investigated as an acid scavenger to remove the acidic impurities in a commercial organic carbonate electrolyte for lithium batteries. We revealed that commercial electrolytes can be significantly improved for Li metal batteries via a simple modification with P2O5. The results indicate that adding P2O5 removes HF from the electrolyte and generates POxFy species which form a favorable SEI. The new electrolyte is also capable of eliminating transition metal leaching and particle cracking of a Li-ion cathode.

Acrylonitrile (AN) is another effective additive in carbonate-based electrolytes. It is verified as a solid electrolyte interphase (SEI) enabler resulting in a uniform and dense lithium (Li) deposition. Our electrochemical and spectroscopic study reveals that AN is cathodically electropolymerized on the Li surface prior to the electrochemical decomposition of the electrolyte during Li deposition. The resultant polyacrylonitrile artificial solid electrolyte interphase enables uniform nucleation and growth of Li deposition with significantly reduced side reactions.

Several oxygen scavengers will also be introduced in this poster. Based on NMR and MS results, these oxygen scavengers undergo sacrificial oxidation during the cycling of lithium batteries. The resultant electrolytes improve long-term cycling and rate performance significantly.