Wildcat Discovery Technologies is developing novel electrolyte additives and noncarbonate solvent formulations that yield improved solid electrolyte interphase (SEI) layers on silicon alloy anodes. The large volumetric changes in silicon during charge/discharge cycles result in mechanical disruption of conventional SEI's leading to rapid capacity fade as the cell cycles. Novel additives that could help to form more mechanically robust SEI passivation layers, hence improving cycle life of silicon based materials are identified through the screening in propylene carbonate (PC) based electrolyte since PC is not expected to form an effective SEI layer. The additives are tested with PC to determine their efficacy. Wildcat's high throughput electrolyte formulation, cell assembly, and test capabilities enable the evaluation of hundreds of additives in a very short timeframe.

Once effective SEI additives are identified in a PC-based formulation, other non-SEI forming solvents can be evaluated. Since the additives are effective without solvent participation in SEI formation, solvents that may not be reductively stable on the anode can also be considered, opening the possibility to more oxidatively stable or less flammable solvents. Wildcat has evaluated hundreds of combinations of noncarbonate solvents with its initial silicon anode SEI additives, and identified a few very unique combinations that showed further improved cycle life over the state-of-the-art carbonate based electrolyte.

Finally, with the most promising noncarbonate solvents in hand, new electrolyte additives are screened for further improved cycle life. The new additives selection is based on the earlier additive screening in PC electrolyte. A thorough Structure Activity Relationship (SAR) study for those promising additives is carried out. This presentation will focus on the results of the additive improvement to cycle life in NMC//Si full cells, and illustrate the opportunities for novel solvent combinations. We will demonstrate the power of high throughput development of lithium ion battery advanced electrolytes within this presentation.