Imidazole-based LiHDI salt for SEI optimization in silicon anodes

To tune lithium transport within the Si-based electrode, lithium 4,5-dicyano-2-(n-heptafluoropropyl)imidazole (LiHDI) was introduced as an additive to a carbonate-based electrolyte, significantly enhancing the electrochemical performance of Si││Li cells. Notably, the addition of 2 wt% LiHDI results in an improved specific capacity of 2250 mAh g −1 at C/10, compared to 2035 mAh g −1 for the baseline electrolyte. XPS analysis shows that LiHDI undergoes minimal decomposition and forms a thicker interphase, whereas the LiPF 6 -containing electrolyte undergoes severe hydrolytic degradation. Electrodes cycled with LiHDI were analyzed by solid-state NMR, SEM, and SAXS, confirming more extensive SEI formation, greater lithiation of the electrode, and more porous SEI morphology, compared to electrodes cycled with LiPF 6 . Such altered interphase morphology improves wettability and ionic transport, thus contributing to improved C-rate performance and cycling stability. • 5-dicyano-2-(n-heptafluoropropyl)imidazole (LiHDI) used as additive for Si anodes. • Addition of 2 wt% LiHDI results in an improved specific capacity. • Addition of LiHDI results in more porous SEI morphology. • This favors Li-ion transport within the Si electrode.