Solid
electrolytes (SEs) are central components that enable high-performance,
all-solid-state lithium batteries (ASSLBs). Amorphous SEs hold great
potential for ASSLBs because their grain-boundary-free characteristics
facilitate intact solid–solid contact and uniform Li-ion conduction
for high-performance cathodes. However, amorphous oxide SEs with limited
ionic conductivities and glassy sulfide SEs with narrow electrochemical
windows cannot sustain high-nickel cathodes. Herein, we report a class
of amorphous Li–Ta–Cl-based chloride SEs possessing
high Li-ion conductivity (up to 7.16 mS cm–1) and
low Young’s modulus (approximately 3 GPa) to enable excellent
Li-ion conduction and intact physical contact among rigid components
in ASSLBs. We reveal that the amorphous Li–Ta–Cl matrix
is composed of LiCl43–, LiCl54–, LiCl65– polyhedra,
and TaCl6– octahedra via machine-learning
simulation, solid-state 7Li nuclear magnetic resonance,
and X-ray absorption analysis. Attractively, our amorphous chloride
SEs exhibit excellent compatibility with high-nickel cathodes. We
demonstrate that ASSLBs comprising amorphous chloride SEs and high-nickel
single-crystal cathodes (LiNi0.88Co0.07Mn0.05O2) exhibit ∼99% capacity retention after
800 cycles at ∼3 C under 1 mA h cm–2 and
∼80% capacity retention after 75 cycles at 0.2 C under a high
areal capacity of 5 mA h cm–2. Most importantly,
a stable operation of up to 9800 cycles with a capacity retention
of ∼77% at a high rate of 3.4 C can be achieved in a freezing
environment of −10 °C. Our amorphous chloride SEs will
pave the way to realize high-performance high-nickel cathodes for
high-energy-density ASSLBs.