Regulating robust interphase using a functional ionic liquid additive with bi-electrode affinity to stabilize the high-voltage lithium-rich lithium metals batteries

Combining Li-rich layered oxides with Li-metals is a viable proposal for the realization of high-energy density lithium-ion batteries. However, it suffers from the unexpected decomposition of the carbonate electrolytes, dissolution of transition metals (TMs) in Li-rich layered oxides, or growth of lithium dendrites at high voltages, resulting in poor performance. Here, a strategy for robust interphase layer construction via an unsaturated imidazole-based ionic liquid additive (1-ethoxymethyl-3-vinyl imidazolium bis-(trifluoromethylsulfonyl) imide ([Vmim1O2][TFSI])) is shared to stabilize high-voltage Li-rich Li-metal batteries. The structure and components characterizations in combination with the theoretical calculation provide an understanding that the ionic liquid [Vmim1O2][TFSI] with vinyl group possesses a bi-electrode affinity and can preferentially be adsorbed on both the cathode and anode surface to participate in the formulation of the interphase layer, suppressing TMs ion dissolution and effectively mitigating the structural degradation of the electrode. As expected, the Li-metal anode with [Vmim1O2][TFSI]-based electrolyte shows a fairly stable Li plating/stripping over 750 h while the full cells with Li1.170Ni0.265Co0.047Mn0.517O2 cathode also represent long-term cyclicity with a capacity retention of 87.89% after 350 cycles at 4.8 V. This work provides new insight into promoting the application of the future demand of high-energy-density lithium-metal batteries via the ionic liquid electrolyte additive with a bi-electrode affinity.

Automated summary

A strategy for constructing a robust interphase layer using an unsaturated imidazole-based ionic liquid additive ([Vmim1O2][TFSI]) is proposed to stabilize high-voltage Li-rich Li-metal batteries. The ionic liquid with a vinyl group preferentially adsorbs on both the cathode and anode surface, suppressing transition metal ion dissolution and mitigating structural degradation of the electrode. Experimental results show that the Li-metal anode with [Vmim1O2][TFSI]-based electrolyte exhibits stable Li plating/stripping over 750 h, and the full cells with Li1.170Ni0.265Co0.047Mn0.517O2 cathode demonstrate long-term cyclicity with a capacity retention of 87.89% after 350 cycles at 4.8 V.