Hexafluoroisopropyl Trifluoromethanesulfonate-Driven Easily Li+ Desolvated Electrolyte to Afford Li||NCM811 Cells with Efficient Anode/Cathode Electrolyte Interphases

X Li and JD Liu and J He and HP Wang and SH Qi and DX Wu and JD Huang and F Li and W Hu and JM Ma, ADVANCED FUNCTIONAL MATERIALS, 31, 2104395 (2021).

DOI: 10.1002/adfm.202104395

Solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI) with optimized components and structures are considered to be crucial for lithium-ion batteries. Here, gradient lithium oxysulfide (Li2SOx, x = 0, 3, 4)/uniform lithium fluoride (LiF)-type SEI is designed in situ by using hexafluoroisopropyl trifluoromethanesulfonate (HFPTf) as electrolyte additive. HFPTf is more likely to be reduced on the surface of Li anode in electrolytes due to its high reduction potential. Moreover, HFPTf can make Li+ desolvated easily, leading to the increase in the flux of Li+ on the surface of Li anode to avoid the growth of Li dendrites. Thus, the cycling stability of Li||Li symmetric cells is improved to be 1000 h at 0.5 mA cm(-2). In addition, HFPTf- contained electrolyte could make Li||NCM811 batteries with a capacity retention of 70% after 150 cycles at 100 mA g(-1), which is attributed to the formation of uniform and stable CEI on the cathode surface for hindering the dissolvation of metal ions from the cathode. This study provides effective insights on the strong ability of additives to adjust electrolytes in "one phase and two interphases" (electrolyte and SEI/CEI).

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