Electric
vehicles (EVs) are poised to dominate the next generation
of transportation, but meeting the power requirements of EVs with
lithium ion batteries is challenging because electrolytes containing
LiPF6 and carbonates do not perform well at high temperatures
and voltages. However, lithium benzimidazole salt is a promising electrolyte
additive that can stabilize LiPF6 through a Lewis acid–base
reaction. The imidazole ring is not eligible for high-voltage applications
owing to its resonance structure, but in this research, electron-withdrawing
(−CF3) and electron-donating (−CH3) substitutions on imidazole rings were investigated. According to
the calculation results, the CF3 substitution facilitates
a high electron cloud density on imidazole ring structures to resist
the electron releases from bezimidazole in oxidation reactions. In
addition, through CF3 substitution, electrons are accepted
from the lattice oxygen (O2–) in lithium-rich layer
material and O– is converted by an electron released.
The O– is then adsorbed with the ethylene carbonate
and catalyzed to alkyl carbonate by Ni2+. The −CF3 substituted benzimidazole triggers a further reaction with
alkyl carbonate and forms a new polyionic liquid solid electrolyte
interphase on the cathode’s surface. Furthermore, the cycle
performance tested at 60 °C and 4.8 V showed that the CF3 substitution maintains the battery retention effectively
and exhibits almost no fading compared with both the blank electrolyte
and the CH3 substitution.
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