Fluorinated Thiophene-Based
Electrolyte Additives
Enable a Robust Cathode Electrolyte Interphase with Conformal Homogeneity
for a High-Voltage LiNi0.8Co0.15Al0.05O2 Cathode
posted on 2024-03-15, 16:14authored byXiaoyan Lin, Yili Chen, Yuling Fu, Fanghong Zeng, Yutong Kuai, Jizheng Lin, Jiarong He, Lidan Xing, Weishan Li
In view of the advantageous merits of LiNi0.8Co0.15Al0.05O2 (NCA), i.e., high
voltage
and decent specific capacity, an impressive electrolyte film-forming
additive, methyl-3-fluorothiophene-2-carboxylate (MFC), is put forward
to remarkably improve the cycle performance of NCA cathodes toward
high energy density lithium-ion batteries (LIBs). Theoretical calculation
and experimental investigation both reveal that MFC is more readily
oxidized to construct a cathode electrolyte interphase (CEI) on the
surface of NCA cathode. Spectroscopy and microscopy data display that
a MFC-derived CEI layer is thin, homogeneous, and conformally covers
on the NCA surface, maintains the NCA structural integrity without
visible microcracks, and protects the NCA cathode from electrolyte
corrosion with alleviated dissolution of Ni and Co. Electrochemical
properties show that the NCA/Li half-cell with a 5 wt % MFC-containing
electrolyte delivers a higher discharge capacity with a much superior
capacity retention of 148.6 mA h g–1/85.5% than
that of base electrolyte (121.2 mA h g–1/71.0%)
after 150 cycles at 1 C. This work indicates that MFC can work as
an effective film-forming additive for high-voltage NCA and provides
precious insights and theoretical guidance to the development of advanced
electrolyte additives for high energy density LIBs.