  Lithium metal batteries (LMBs), when coupled with a localized
high-concentration electrolyte and a high-voltage nickel-rich cathode, offer a
solution to the increasing demand for high energy density and long cycle life.
However, the aggressive electrode chemistry poses safety risks to LMBs at
higher temperatures and cutoff voltages. Here, we decipher the interphase
instability in LHCE-based LMBs with a Ni0.8Co0.1Mn0.1O2 cathode at elevated
temperatures. Our findings reveal that the generation of fluorine radicals in
the electrolyte induces the solvent decomposition and consequent chain
reactions, thereby reconstructing the cathode electrolyte interphase (CEI) and
degrading battery cyclability. As further evidenced, introducing an acid
scavenger of dimethoxydimethylsilane (DODSi) significantly boosts CEI stability
with suppressed microcracking. A Ni0.8Co0.1Mn0.1O2||Li cell with this
DODSi-functionalized LHCE achieves an unprecedented capacity retention of 93.0%
after 100 cycles at 80 {\deg}C. This research provides insights into
electrolyte engineering for practical LMBs with high safety under extreme
temperatures.
