Exploring
new solid electrolytes (SEs) for lithium-ion conduction
is significant for the development of rechargeable all-solid-state
lithium batteries. Here, a lead-free organic–inorganic halide
perovskite, MASr0.8Li0.4Cl3 (MA =
methylammonium, CH3NH3 in formula), is reported
as a new SE for Li-ion conduction due to its highly symmetric crystal
structure, inherent soft lattice, and good tolerance for composition
tunability. Via density functional theory calculations, we demonstrate
that the hybrid perovskite framework can allow fast Li-ion migration
without the collapse of the crystal structure. The influence of the
lithium content in MASr1–x
Li2x
Cl3 (x = 0.1,
0.2, 0.3, or 0.4) on Li+ migration is systematically investigated.
At the lithium content of x = 0.2, the MASr0.8Li0.4Cl3 achieves the room-temperature lithium
ionic conductivity of 7.0 × 10–6 S cm–1 with a migration energy barrier of ∼0.47 eV. The lithium–tin
alloy (Li–Sn) symmetric cell exhibits stable electrochemical
lithium plating/stripping for nearly 100 cycles, indicating the alloy
anode compatibility of the MASr0.8Li0.4Cl3 SE. This lead-free organic–inorganic halide perovskite
SE will open a new avenue for exploring new SEs.
Using the newly developed positron annihilation lifetime
spectroscopy
(PALS) facility with a high count rate up to 3000 cps, in
situ PALS experiments were performed for the first time on
the continuous stretching process of polymers to quantitatively analyze
the minute-scale evolution of free-volume holes. According to the
stress–strain relationship and PALS results of four types of
polyethylenes with different crystallinities, the tensile process
could be divided into four distinct stages: elastic, initial nonlinear
(until yield point), postyield, and strain hardening stages. The increase
of o-Ps (orthopositronium) lifetime in the first three stages exhibits
an enlargement of free-volume hole size with increasing strain. The
decrease of the o-Ps lifetime in the last stage is most probably due
to the increasing anisotropy of free-volume holes. The relative fractional
free volume FFVr (derived from hole radius R (calculated from the Tao–Eldrup model) and o-Ps intensity)
generally increases in the first two stages but remains nearly unchanged
in the other two stages. This work demonstrates a new feasibility
to disclose minute-scale evolution of microstructure of materials
through in situ PALS experiments in the future.
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