High-entropy
sodium
vanadium
fluorophosphate
(HE-NVPF)
with
good
structural
stability,
high
electrical
conductivity,
and
rapid
redox
dynamics
has
been
considered
to
be
a
promising
cathode
material
for
sodium-ion
batteries.
However,
the
HE-NVPF
prepared
by
conventional
sol–gel
method
is
usually
challenged
time-consuming
reaction
processes
uncontrollable
particle
sizes
due
slow
mass/heat
transfer
uneven
space,
which
restrict
its
electrochemical
performance.
In
this
study,
we
developed
continuous-flow
synthesis
strategy
via
microreactor
construct
high-entropy
Na3V2–xMx(PO4)2F3
(0
<
x
2,
M
=
Ca,
Mg,
Al,
Cr,
Mn)
(M-HE-NVPF).
Notably,
transfer,
confined
doping
effect
can
realize
efficient
(2
h)
of
M-HE-NVPF
small
size
(∼131
nm),
conductivity
because
introduction
local
disturbances
leading
overlapping
energy
distributions
sites,
distinct
suppressing
detrimental
phase
transitions
in
low
plateau
region.
As
result,
exhibits
rate
capacities
125.3
mAh
g–1
at
0.5
C
110.8
50
C,
marvelous
cycle
stability
90.5%
capacity
retention
95.5%
20
after
400
cycles.
ACS Nano,
Journal Year:
2024,
Volume and Issue:
18(19), P. 12468 - 12476
Published: May 3, 2024
Na
super
ionic
conductor
(NASICON)-type
polyanionic
vanadium
fluorophosphate
Na3V2O2(PO4)2F
(NVOPF)
is
a
promising
cathode
material
for
high-energy
sodium-ion
batteries.
The
dynamic
diffusion
and
exchange
of
sodium
ions
in
the
lattice
NVOPF
are
crucial
its
electrochemical
performance.
However,
standard
characterizations
mostly
focused
on
as-synthesized
without
cycling,
which
different
from
actual
battery
operation
conditions.
In
this
work,
we
investigated
hopping
processes
at
intermediate
charging
state
with
23Na
solid-state
nuclear
magnetic
resonance
(ssNMR)
density
functional
theory
(DFT)
calculations.
Our
experimental
revealed
six
distinct
coordination
sites
structure
determined
rates
among
these
variable
temperatures.
theoretical
calculations
showed
that
correspond
to
ion
transport
pathways
crystalline
lattice.
combined
study
uncovered
underlying
mechanisms
cycled
understandings
may
help
optimization
materials
ACS Sustainable Chemistry & Engineering,
Journal Year:
2023,
Volume and Issue:
11(34), P. 12631 - 12645
Published: Aug. 16, 2023
Low
intrinsic
conductivity
and
poor
structural
stability
limit
the
application
of
Na3V2(PO4)3
(NVP).
Herein,
a
strategy
for
in
situ
synthesis
dandelion-shaped
NVP
based
on
cross-linked
chitosan
quaternary
ammonium
hydrogel
(CHACC)
carbon
nanotubes
(CNTs)
is
proposed.
CHACC
CNTs
provide
steric
hindrance
avoid
agglomeration
precursor
particles.
Notably,
could
be
carbonized
into
thin
N–Cl
codoped
coating,
attaching
to
short
fibers
by
electrostatic
adsorption
construct
dandelion
shape.
The
coating
delivers
superior
electronic
generates
beneficial
defects.
DFT
calculations
are
explored
investigate
influence
codoping
mixed
matrix.
Significantly,
triple
conductive
networks
successfully
constructed
dual-carbon
resources.
attached
connect
with
each
other
forms
first
network.
Large-scale
CNT
network
generated
through
physical
entanglement
bonding.
provides
additional
substrate
after
carbonizations.
unique
supply
stable
skeleton,
alleviating
impact
current
shock
increasing
active
sites.
CHACC–CNTs-NVP
submitted
value
82.5
mAh
g–1
at
80
C
remained
61.9
6000
cycles,
corresponding
low
decay
rate
0.004%
per
cycle.
Even
120
C,
it
still
releases
81.5
g–1.
Small,
Journal Year:
2023,
Volume and Issue:
20(5)
Published: Sept. 26, 2023
Abstract
In
situ
polymerization
to
prepare
quasi‐solid
electrolyte
has
attracted
wide
attentions
for
its
advantage
in
achieving
intimate
electrode–electrolyte
contact
and
the
high
process
compatibility
with
current
liquid
batteries;
however,
gases
can
be
generated
during
remained
final
electrolyte,
severely
impairing
uniformity
electrochemical
performance.
this
work,
an
polymerized
poly(vinylene
carbonate)‐based
high‐voltage
sodium
metal
batteries
(SMBs)
is
demonstrated,
which
contains
a
novel
multifunctional
additive
N
‐methyl‐
‐(trimethylsilyl)trifluoroacetamide
(MSTFA).
MSTFA
as
high‐efficient
plasticizer
diminishes
residual
after
polymerization;
softer
homogeneous
enables
much
faster
ionic
conduction.
The
HF/H
2
O
scavenge
effect
of
mitigates
corrosion
free
acid
cathode
interfacial
passivating
layers,
enhancing
cycle
stability
under
voltage.
As
result,
4.4
V
Na||Na
3
(PO
4
)
F
cell
employing
optimized
possesses
initial
discharge
capacity
112.0
mAh
g
−1
retention
91.3%
100
cycles
at
0.5C,
obviously
better
than
those
counterparts
without
addition.
This
work
gives
pioneering
study
on
gas
residue
phenomenon
electrolytes,
introduces
silane
that
effectively
enhances
performance
SMBs,
showing
practical
application
significance.
