<s>
A	O
flow	B-Algorithm
battery	I-Algorithm
,	O
or	O
redox	B-Algorithm
flow	I-Algorithm
battery	I-Algorithm
(	O
after	O
reduction	O
–	O
oxidation	O
)	O
,	O
is	O
a	O
type	O
of	O
electrochemical	O
cell	O
where	O
chemical	O
energy	O
is	O
provided	O
by	O
two	O
chemical	O
components	O
dissolved	O
in	O
liquids	O
that	O
are	O
pumped	O
through	O
the	O
system	O
on	O
separate	O
sides	O
of	O
a	O
membrane	O
.	O
</s>
<s>
Various	O
types	O
of	O
flow	B-Algorithm
batteries	I-Algorithm
have	O
been	O
demonstrated	O
,	O
including	O
inorganic	O
flow	B-Algorithm
batteries	I-Algorithm
and	O
organic	O
flow	B-Algorithm
batteries	I-Algorithm
.	O
</s>
<s>
Under	O
each	O
category	O
,	O
flow	B-Algorithm
battery	I-Algorithm
design	O
can	O
be	O
further	O
classified	O
into	O
full	O
flow	B-Algorithm
batteries	I-Algorithm
,	O
semi-flow	O
batteries	O
,	O
and	O
membraneless	O
flow	B-Algorithm
batteries	I-Algorithm
.	O
</s>
<s>
The	O
fundamental	O
difference	O
between	O
conventional	O
and	O
flow	B-Algorithm
batteries	I-Algorithm
is	O
that	O
energy	O
is	O
stored	O
in	O
the	O
electrode	O
material	O
in	O
conventional	O
batteries	O
,	O
while	O
in	O
flow	B-Algorithm
batteries	I-Algorithm
it	O
is	O
stored	O
in	O
the	O
electrolyte	O
.	O
</s>
<s>
Patent	O
Classifications	O
for	O
Flow	B-Algorithm
Batteries	I-Algorithm
have	O
not	O
been	O
fully	O
developed	O
as	O
of	O
2021	O
.	O
</s>
<s>
Cooperative	O
Patent	O
Classification	O
considers	O
RFBs	O
as	O
a	O
subclass	O
of	O
regenerative	O
fuel	O
cell	O
(	O
H01M8/18	O
)	O
,	O
even	O
though	O
it	O
is	O
more	O
appropriate	O
to	O
consider	O
fuel	O
cells	O
as	O
a	O
subclass	O
of	O
flow	B-Algorithm
batteries	I-Algorithm
.	O
</s>
<s>
A	O
flow	B-Algorithm
battery	I-Algorithm
may	O
be	O
used	O
like	O
a	O
fuel	O
cell	O
(	O
where	O
new	O
charged	O
negolyte	O
(	O
a.k.a.	O
</s>
<s>
oxidant	O
)	O
are	O
added	O
to	O
the	O
system	O
)	O
or	O
like	O
a	O
rechargeable	B-Architecture
battery	I-Architecture
(	O
where	O
an	O
electric	O
power	O
source	O
drives	O
regeneration	O
of	O
the	O
reducer	O
and	O
oxidant	O
)	O
.	O
</s>
<s>
While	O
flow	B-Algorithm
batteries	I-Algorithm
have	O
certain	O
technical	O
advantages	O
over	O
conventional	O
rechargeable	B-Architecture
batteries	I-Architecture
with	O
solid	O
electroactive	O
materials	O
,	O
such	O
as	O
independent	O
scaling	O
of	O
power	O
(	O
determined	O
by	O
the	O
size	O
of	O
the	O
stack	O
)	O
and	O
of	O
energy	O
(	O
determined	O
by	O
the	O
size	O
of	O
the	O
tanks	O
)	O
,	O
long	O
cycle	O
and	O
calendar	O
life	O
,	O
potentially	O
lower	O
total	O
cost	O
of	O
ownership	O
,	O
all	O
flow	B-Algorithm
batteries	I-Algorithm
suffer	O
from	O
low	O
cycle	O
energy	O
efficiency	O
(	O
50	O
–	O
80%	O
)	O
.	O
</s>
<s>
This	O
inferior	O
energy	O
efficiency	O
stems	O
from	O
the	O
need	O
to	O
operate	O
flow	B-Algorithm
batteries	I-Algorithm
at	O
high	O
(>=	O
100	O
mA/cm2	O
)	O
current	O
densities	O
to	O
reduce	O
the	O
effect	O
of	O
the	O
internal	O
crossover	O
(	O
through	O
the	O
membrane/separator	O
inside	O
each	O
cell	O
)	O
and	O
to	O
reduce	O
the	O
cost	O
of	O
power	O
(	O
size	O
of	O
stacks	O
)	O
.	O
</s>
<s>
Also	O
,	O
most	O
flow	B-Algorithm
batteries	I-Algorithm
(	O
Zn-Cl2	O
,	O
Zn-Br2	O
and	O
H2-LiBrO3	O
are	O
exceptions	O
)	O
have	O
lower	O
specific	O
energy	O
(	O
heavier	O
weight	O
)	O
compared	O
to	O
lithium-ion	O
batteries	O
.	O
</s>
<s>
The	O
heavier	O
weight	O
results	O
mostly	O
from	O
the	O
need	O
to	O
use	O
a	O
solvent	O
(	O
usually-water	O
)	O
to	O
keep	O
the	O
redox	B-Operating_System
active	O
species	O
in	O
the	O
liquid	O
phase	O
.	O
</s>
<s>
The	O
zinc	B-Algorithm
–	I-Algorithm
bromine	I-Algorithm
flow	I-Algorithm
battery	I-Algorithm
(	O
Zn-Br2	O
)	O
is	O
the	O
oldest	O
flow	B-Algorithm
battery	I-Algorithm
chemistry	O
,	O
with	O
John	O
Doyle	O
’s	O
patent	O
US224404	O
filed	O
on	O
September	O
29	O
,	O
1879	O
.	O
</s>
<s>
Walther	O
Kangro	O
,	O
an	O
Estonian	O
chemist	O
working	O
in	O
Germany	O
,	O
was	O
the	O
first	O
to	O
demonstrate	O
in	O
the	O
1950s	O
flow	B-Algorithm
batteries	I-Algorithm
based	O
fully	O
on	O
dissolved	O
transition	O
metal	O
ions	O
:	O
Ti	O
–	O
Fe	O
and	O
Cr	O
–	O
Fe	O
.	O
</s>
<s>
comprising	O
both	O
chromium	B-Language
and	O
iron	O
species	O
in	O
the	O
negolyte	O
and	O
in	O
the	O
posolyte	O
)	O
were	O
used	O
.	O
</s>
<s>
the	O
equilibrium	O
between	O
electrochemically	O
active	O
Cr3+	O
chloro-complexes	O
and	O
inactive	O
hexa-aqua	O
complex	O
,	O
which	O
can	O
be	O
alleviated	O
by	O
adding	O
chelating	O
amino-ligands	O
)	O
and	O
hydrogen	O
evolution	O
on	O
the	O
negode	O
(	O
which	O
is	O
mitigated	O
by	O
adding	O
Pb	O
salts	O
for	O
increasing	O
the	O
H2	O
overvoltage	O
and	O
Au	O
salts	O
for	O
catalyzing	O
the	O
chromium	B-Language
electrode	O
reaction	O
)	O
.	O
</s>
<s>
In	O
2022	O
,	O
Dalian	O
,	O
China	O
began	O
operating	O
a	O
400	O
MWh	O
,	O
100	O
MW	O
vanadium	O
flow	B-Algorithm
battery	I-Algorithm
,	O
then	O
the	O
largest	O
of	O
its	O
type	O
.	O
</s>
<s>
A	O
flow	B-Algorithm
battery	I-Algorithm
is	O
a	O
rechargeable	B-Architecture
fuel	O
cell	O
in	O
which	O
an	O
electrolyte	O
containing	O
one	O
or	O
more	O
dissolved	O
electroactive	O
elements	O
flows	O
through	O
an	O
electrochemical	O
cell	O
that	O
reversibly	O
converts	O
chemical	O
energy	O
directly	O
to	O
electricity	O
.	O
</s>
<s>
Flow	B-Algorithm
batteries	I-Algorithm
can	O
be	O
rapidly	O
"	O
recharged	O
"	O
by	O
replacing	O
the	O
electrolyte	O
liquid	O
(	O
in	O
a	O
similar	O
way	O
to	O
refilling	O
fuel	O
tanks	O
for	O
internal	O
combustion	O
engines	O
)	O
while	O
simultaneously	O
recovering	O
the	O
spent	O
material	O
for	O
recharging	O
.	O
</s>
<s>
Many	O
flow	B-Algorithm
batteries	I-Algorithm
use	O
carbon	O
felt	O
electrodes	O
due	O
to	O
its	O
low	O
cost	O
and	O
adequate	O
electrical	O
conductivity	O
,	O
although	O
these	O
electrodes	O
somewhat	O
limit	O
power	O
density	O
due	O
to	O
their	O
low	O
inherent	O
activity	O
toward	O
many	O
redox	B-Operating_System
couples	O
.	O
</s>
<s>
In	O
other	O
words	O
,	O
a	O
flow	B-Algorithm
battery	I-Algorithm
is	O
an	O
electrochemical	O
cell	O
,	O
with	O
the	O
property	O
that	O
the	O
ionic	O
solution	O
(	O
electrolyte	O
)	O
is	O
stored	O
outside	O
of	O
the	O
cell	O
(	O
instead	O
of	O
in	O
the	O
cell	O
around	O
the	O
electrodes	O
)	O
and	O
can	O
be	O
fed	O
into	O
the	O
cell	O
in	O
order	O
to	O
generate	O
electricity	O
.	O
</s>
<s>
Flow	B-Algorithm
batteries	I-Algorithm
are	O
governed	O
by	O
the	O
design	O
principles	O
established	O
by	O
electrochemical	O
engineering	O
.	O
</s>
<s>
Redox	B-Algorithm
flow	I-Algorithm
batteries	I-Algorithm
,	O
and	O
to	O
a	O
lesser	O
extent	O
hybrid	O
flow	B-Algorithm
batteries	I-Algorithm
,	O
have	O
the	O
advantages	O
of	O
:	O
</s>
<s>
Flow	B-Algorithm
batteries	I-Algorithm
have	O
a	O
lower	O
energy	O
efficiency	O
,	O
because	O
they	O
operate	O
at	O
higher	O
current	O
densities	O
to	O
minimize	O
the	O
effects	O
of	O
the	O
cross-over	O
(	O
internal	O
self-discharge	O
)	O
and	O
to	O
reduce	O
the	O
cost	O
of	O
power	O
.	O
</s>
<s>
Flow	B-Algorithm
batteries	I-Algorithm
typically	O
have	O
a	O
higher	O
energy	O
efficiency	O
than	O
fuel	O
cells	O
,	O
but	O
lower	O
than	O
lithium-ion	O
batteries	O
.	O
</s>
<s>
The	O
redox	B-Operating_System
(	O
reduction	O
–	O
oxidation	O
)	O
cell	O
is	O
a	O
reversible	B-Architecture
cell	I-Architecture
in	O
which	O
redox-active	O
species	O
are	O
in	O
fluid	O
(	O
liquid	O
or	O
gas	O
)	O
media	O
.	O
</s>
<s>
Redox	B-Algorithm
flow	I-Algorithm
batteries	I-Algorithm
are	O
rechargeable	B-Architecture
(	O
secondary	B-Architecture
)	O
cells	O
.	O
</s>
<s>
Because	O
they	O
employ	O
heterogeneous	O
electron	O
transfer	O
rather	O
than	O
solid-state	O
diffusion	O
or	O
intercalation	O
they	O
are	O
more	O
similar	O
to	O
fuel	O
cells	O
rather	O
than	O
to	O
conventional	O
batteries	O
(	O
such	O
as	O
lead	B-Device
–	I-Device
acid	I-Device
or	O
lithium-ion	O
)	O
.	O
</s>
<s>
Later	O
,	O
particularly	O
in	O
the	O
1960s	O
and	O
1990s	O
,	O
rechargeable	B-Architecture
fuel	O
cells	O
(	O
i.e.	O
</s>
<s>
Examples	O
of	O
redox	B-Algorithm
flow	I-Algorithm
batteries	I-Algorithm
are	O
the	O
vanadium	O
redox	B-Algorithm
flow	I-Algorithm
battery	I-Algorithm
,	O
polysulfide	O
–	O
bromide	O
battery	O
(	O
Regenesys	O
)	O
,	O
iron	B-Algorithm
redox	I-Algorithm
flow	I-Algorithm
battery	I-Algorithm
(	O
IRFB	O
)	O
,	O
and	O
uranium	O
redox	B-Algorithm
flow	I-Algorithm
battery	I-Algorithm
.	O
</s>
<s>
Redox	B-Operating_System
fuel	O
cells	O
are	O
less	O
common	O
commercially	O
although	O
many	O
systems	O
have	O
been	O
proposed	O
.	O
</s>
<s>
Vanadium	O
redox	B-Algorithm
flow	I-Algorithm
batteries	I-Algorithm
are	O
the	O
most	O
marketed	O
flow	B-Algorithm
batteries	I-Algorithm
at	O
present	O
,	O
due	O
to	O
the	O
advantages	O
they	O
provide	O
over	O
other	O
chemistries	O
,	O
despite	O
limited	O
energy	O
and	O
power	O
densities	O
.	O
</s>
<s>
More	O
importantly	O
for	O
the	O
commercial	O
success	O
of	O
VRFBs	O
is	O
actually	O
an	O
almost	O
perfect	O
match	O
of	O
the	O
voltage	O
window	O
of	O
carbon/aqueous	O
acid	O
interface	O
with	O
the	O
working	O
voltage	O
range	O
of	O
the	O
vanadium	O
redox-couples	O
.	O
</s>
<s>
The	O
long	O
lifetimes	O
of	O
flow	B-Algorithm
batteries	I-Algorithm
allow	O
for	O
the	O
amortization	O
of	O
their	O
relatively	O
high	O
capital	O
cost	O
(	O
due	O
to	O
vanadium	O
,	O
carbon	O
felts	O
,	O
bipolar	O
plates	O
,	O
membranes	O
)	O
.	O
</s>
<s>
It	O
is	O
the	O
major	O
driving	O
force	O
to	O
develop	O
alternative	O
flow	B-Algorithm
battery	I-Algorithm
technologies	O
.	O
</s>
<s>
Traditional	O
flow	B-Algorithm
battery	I-Algorithm
chemistries	O
have	O
both	O
low	O
specific	O
energy	O
(	O
which	O
makes	O
them	O
too	O
heavy	O
for	O
fully	O
electric	O
vehicles	O
)	O
and	O
low	O
specific	O
power	O
(	O
which	O
makes	O
them	O
too	O
expensive	O
for	O
stationary	O
energy	O
storage	O
)	O
.	O
</s>
<s>
They	O
require	O
no	O
lithium	O
,	O
heavy	B-Operating_System
metals	I-Operating_System
,	O
or	O
rare-earth	O
elements	O
.	O
</s>
<s>
The	O
hybrid	O
flow	B-Algorithm
battery	I-Algorithm
uses	O
one	O
or	O
more	O
electroactive	O
components	O
deposited	O
as	O
a	O
solid	O
layer	O
.	O
</s>
<s>
The	O
major	O
disadvantage	O
is	O
the	O
loss	O
decoupled	O
energy	O
and	O
power	O
as	O
seen	O
in	O
full	O
flow	B-Algorithm
batteries	I-Algorithm
from	O
using	O
a	O
solid	O
state	O
electrode	O
.	O
</s>
<s>
Hybrid	O
flow	B-Algorithm
batteries	I-Algorithm
include	O
the	O
zinc	B-Algorithm
–	I-Algorithm
bromine	I-Algorithm
,	O
zinc	B-Application
–	O
cerium	O
,	O
soluble	O
lead	B-Device
–	I-Device
acid	I-Device
,	O
and	O
iron-salt	O
flow	B-Algorithm
batteries	I-Algorithm
.	O
</s>
<s>
reported	O
a	O
vanadium	O
–	O
metal	O
hydride	O
rechargeable	B-Architecture
hybrid	O
flow	B-Algorithm
battery	I-Algorithm
with	O
an	O
experimental	O
OCV	O
of	O
1.93	O
V	O
and	O
operating	O
voltage	O
of	O
1.70	O
V	O
,	O
relatively	O
high	O
values	O
among	O
rechargeable	B-Architecture
flow	B-Algorithm
batteries	I-Algorithm
with	O
aqueous	O
electrolytes	O
.	O
</s>
<s>
They	O
reported	O
further	O
improvements	O
of	O
this	O
redox	B-Operating_System
couple	O
with	O
achievements	O
of	O
increased	O
current	O
density	O
,	O
inclusion	O
of	O
larger	O
100cm2	O
electrodes	O
,	O
and	O
the	O
operation	O
of	O
10	O
large	O
cells	O
in	O
series	O
.	O
</s>
<s>
In	O
2016	O
,	O
a	O
high	O
energy	O
density	O
Mn(VI )	O
/Mn	O
( VII	O
)	O
-Zn	O
hybrid	O
flow	B-Algorithm
battery	I-Algorithm
was	O
proposed	O
.	O
</s>
<s>
A	O
prototype	O
zinc	B-Application
–	O
polyiodide	O
flow	B-Algorithm
battery	I-Algorithm
demonstrated	O
an	O
energy	O
density	O
of	O
167Wh/L	O
(	O
watt-hours	O
per	O
liter	O
)	O
.	O
</s>
<s>
Older	O
zinc	B-Application
–	O
bromide	O
cells	O
reach	O
70Wh/L	O
.	O
</s>
<s>
The	O
zinc	B-Application
–	O
polyiodide	O
battery	O
is	O
claimed	O
to	O
be	O
safer	O
than	O
other	O
flow	B-Algorithm
batteries	I-Algorithm
given	O
its	O
absence	O
of	O
acidic	O
electrolytes	O
,	O
nonflammability	O
and	O
operating	O
range	O
of	O
that	O
does	O
not	O
require	O
extensive	O
cooling	O
circuitry	O
,	O
which	O
would	O
add	O
weight	O
and	O
occupy	O
space	O
.	O
</s>
<s>
One	O
unresolved	O
issue	O
is	O
zinc	B-Application
buildup	O
on	O
the	O
negative	O
electrode	O
that	O
can	O
permeate	O
the	O
membrane	O
,	O
reducing	O
efficiency	O
.	O
</s>
<s>
When	O
the	O
battery	O
is	O
fully	O
discharged	O
,	O
both	O
tanks	O
hold	O
the	O
same	O
electrolyte	O
solution	O
:	O
a	O
mixture	O
of	O
positively	O
charged	O
zinc	B-Application
ions	O
(	O
)	O
and	O
negatively	O
charged	O
iodide	O
ion	O
,	O
(	O
)	O
.	O
</s>
<s>
Inside	O
the	O
stack	O
,	O
zinc	B-Application
ions	O
pass	O
through	O
a	O
selective	O
membrane	O
and	O
change	O
into	O
metallic	O
zinc	B-Application
on	O
the	O
stack	O
's	O
negative	O
side	O
.	O
</s>
<s>
To	O
further	O
increase	O
the	O
energy	O
density	O
of	O
the	O
zinc	B-Application
–	O
iodide	O
flow	B-Algorithm
battery	I-Algorithm
,	O
bromide	O
ions	O
(	O
)	O
are	O
used	O
as	O
the	O
complexing	O
agent	O
to	O
stabilize	O
the	O
free	O
iodine	O
,	O
forming	O
iodine	O
–	O
bromide	O
ions	O
(	O
)	O
as	O
a	O
means	O
to	O
free	O
up	O
iodide	O
ions	O
for	O
charge	O
storage	O
.	O
</s>
<s>
Proton	O
flow	B-Algorithm
batteries	I-Algorithm
(	O
PFB	O
)	O
integrate	O
a	O
metal	O
hydride	O
storage	O
electrode	O
into	O
a	O
reversible	O
proton	O
exchange	O
membrane	O
(	O
PEM	O
)	O
fuel	O
cell	O
.	O
</s>
<s>
Compared	O
to	O
redox	B-Algorithm
flow	I-Algorithm
batteries	I-Algorithm
that	O
are	O
inorganic	O
,	O
such	O
as	O
vanadium	O
redox	B-Algorithm
flow	I-Algorithm
batteries	I-Algorithm
and	O
Zn-Br2	O
batteries	O
,	O
which	O
have	O
been	O
developed	O
for	O
decades	O
,	O
organic	O
redox	B-Algorithm
flow	I-Algorithm
batteries	I-Algorithm
emerged	O
in	O
2009	O
.	O
</s>
<s>
The	O
primary	O
appeal	O
of	O
organic	O
redox	B-Algorithm
flow	I-Algorithm
batteries	I-Algorithm
lies	O
in	O
the	O
tunable	O
redox	B-Operating_System
properties	O
of	O
the	O
active	O
components	O
.	O
</s>
<s>
Organic	O
redox	B-Algorithm
flow	I-Algorithm
batteries	I-Algorithm
can	O
be	O
further	O
classified	O
into	O
aqueous	O
(	O
AORFBs	O
)	O
and	O
non-aqueous	O
(	O
NAORFBs	O
)	O
.	O
</s>
<s>
Viologen-based	O
flow	B-Algorithm
batteries	I-Algorithm
have	O
been	O
mainly	O
developed	O
by	O
Liu	O
’s	O
group	O
at	O
Utah	O
State	O
University	O
.	O
</s>
<s>
Quinones	O
and	O
their	O
derivatives	O
are	O
the	O
basis	O
of	O
many	O
organic	O
redox	B-Operating_System
systems	O
.	O
</s>
<s>
An	O
aqueous	O
flow	B-Algorithm
battery	I-Algorithm
with	O
inexpensive	O
carbon	O
electrodes	O
,	O
combining	O
the	O
quinone/hydroquinone	O
couple	O
with	O
the	O
/	O
redox	B-Operating_System
couple	O
,	O
yields	O
a	O
peak	O
galvanic	O
power	O
density	O
exceeding	O
6,000	O
W/m2	O
at	O
13,000	O
A/m2	O
.	O
</s>
<s>
The	O
higher	O
pH	O
is	O
less	O
corrosive	O
,	O
allowing	O
the	O
use	O
of	O
inexpensive	O
polymer	B-Language
tanks	O
.	O
</s>
<s>
Thus	O
,	O
quinone	O
diaminoanthraquinone	O
and	O
indigo-based	O
molecules	O
as	O
well	O
as	O
TEMPO/phenazine	O
combining	O
molecules	O
are	O
potential	O
electrolytes	O
for	O
the	O
development	O
of	O
symmetric	O
redox-flow	O
batteries	O
(	O
SRFB	O
)	O
.	O
</s>
<s>
Metal-organic	O
flow	B-Algorithm
batteries	I-Algorithm
use	O
organic	O
ligands	O
to	O
improve	O
the	O
properties	O
of	O
redox-active	O
metals	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
use	O
of	O
chromium	B-Language
coordinated	O
to	O
1	O
,	O
3-propanediaminetetraacetate	O
(	O
PDTA	O
)	O
,	O
gave	O
cell	O
potentials	O
of	O
1.62	O
V	O
vs.	O
ferrocyanide	O
and	O
a	O
record	O
2.13	O
V	O
vs.	O
bromine	O
.	O
</s>
<s>
Metal-organic	O
flow	B-Algorithm
batteries	I-Algorithm
may	O
be	O
known	O
as	O
coordination	O
chemistry	O
flow	B-Algorithm
batteries	I-Algorithm
,	O
which	O
represents	O
the	O
technology	O
behind	O
Lockheed	O
Martin	O
's	O
Gridstar	O
Flow	O
technology	O
.	O
</s>
<s>
Oligomer	O
redox-species	O
RFB	O
have	O
been	O
proposed	O
to	O
reduce	O
the	O
crossover	O
of	O
the	O
electroactive	O
species	O
,	O
while	O
using	O
low	O
cost	O
membranes	O
.	O
</s>
<s>
Such	O
redox-active	O
oligomers	O
are	O
known	O
as	O
redoxymers	O
.	O
</s>
<s>
One	O
system	O
uses	O
organic	O
polymers	B-Language
and	O
a	O
saline	O
solution	O
with	O
a	O
cellulose	O
membrane	O
.	O
</s>
<s>
It	O
retains	O
the	O
big	O
"	O
spaghetti	O
"	O
-like	O
polymer	B-Language
molecules	O
,	O
while	O
allowing	O
small	O
counterions	O
to	O
pass	O
.	O
</s>
<s>
The	O
concept	O
may	O
solve	O
the	O
high	O
cost	O
of	O
traditional	O
Nafion	O
membrane	O
,	O
but	O
the	O
design	O
and	O
synthesis	O
of	O
redox	B-Operating_System
active	O
polymer	B-Language
with	O
high	O
water	O
solubility	O
is	O
not	O
trivial	O
.	O
</s>
<s>
So	O
far	O
,	O
RFBs	O
with	O
oligomer	O
redox-species	O
have	O
not	O
demonstrated	O
competitive	O
area-specific	O
power	O
.	O
</s>
<s>
It	O
is	O
not	O
clear	O
whether	O
low	O
operating	O
current	O
density	O
is	O
an	O
intrinsic	O
feature	O
of	O
large	O
redox-molecules	O
or	O
not	O
.	O
</s>
<s>
Other	O
flow-type	O
batteries	O
include	O
the	O
zinc	B-Algorithm
–	I-Algorithm
cerium	I-Algorithm
battery	I-Algorithm
,	O
the	O
zinc	B-Algorithm
–	I-Algorithm
bromine	I-Algorithm
battery	I-Algorithm
,	O
and	O
the	O
hydrogen	O
–	O
bromine	O
battery	O
.	O
</s>
<s>
The	O
chemical	O
reaction	O
can	O
be	O
reversed	O
to	O
recharge	B-Architecture
the	O
battery	O
–	O
a	O
first	O
for	O
any	O
membraneless	O
design	O
.	O
</s>
<s>
One	O
such	O
membraneless	O
flow	B-Algorithm
battery	I-Algorithm
published	O
in	O
August	O
2013	O
produced	O
a	O
maximum	O
power	O
density	O
of	O
0.795mW/cm2	O
,	O
three	O
times	O
as	O
much	O
power	O
as	O
other	O
membraneless	O
systems	O
—	O
and	O
an	O
order	O
of	O
magnitude	O
higher	O
than	O
lithium-ion	O
batteries	O
.	O
</s>
<s>
In	O
2018	O
,	O
a	O
macroscale	O
membraneless	O
redox	B-Algorithm
flow	I-Algorithm
battery	I-Algorithm
capable	O
of	O
recharging	O
and	O
recirculation	O
of	O
the	O
same	O
electrolyte	O
streams	O
for	O
multiple	O
cycles	O
has	O
been	O
demonstrated	O
.	O
</s>
<s>
In	O
a	O
Semi-solid	B-Algorithm
flow	I-Algorithm
battery	I-Algorithm
,	O
the	O
positive	O
and	O
negative	O
electrodes	O
are	O
composed	O
of	O
particles	O
suspended	O
in	O
a	O
carrier	O
liquid	O
.	O
</s>
<s>
The	O
carbon	O
free	O
semi-solid	O
redox	B-Algorithm
flow	I-Algorithm
battery	I-Algorithm
is	O
also	O
sometimes	O
referred	O
to	O
as	O
Solid	B-Algorithm
Dispersion	I-Algorithm
Redox	I-Algorithm
Flow	I-Algorithm
Battery	I-Algorithm
.	O
</s>
<s>
Flow	B-Algorithm
batteries	I-Algorithm
with	O
redox-targeted	O
solids	O
(	O
ROTS	O
)	O
,	O
also	O
known	O
as	O
solid	O
energy	O
boosters	O
(	O
SEBs	O
)	O
,	O
is	O
another	O
recent	O
development	O
.	O
</s>
<s>
redox	B-Operating_System
fluids	O
)	O
,	O
come	O
in	O
contact	O
with	O
a	O
one	O
or	O
more	O
solid	O
electroactive	O
materials	O
,	O
stored	O
in	O
tanks	O
outside	O
the	O
power	O
stack	O
.	O
</s>
<s>
The	O
redox	B-Operating_System
fluids	O
comprise	O
one	O
or	O
more	O
redox	B-Operating_System
couples	O
,	O
with	O
redox	B-Operating_System
potentials	O
flanking	O
the	O
redox	B-Operating_System
potential	O
of	O
the	O
solid	O
electroactive	O
material	O
.	O
</s>
<s>
Such	O
RFBs	O
with	O
Solid	O
Energy	O
Boosters	O
(	O
SEBs	O
)	O
combine	O
the	O
high	O
specific	O
energy	O
advantage	O
of	O
conventional	O
batteries	O
(	O
such	O
as	O
lithium-ion	O
)	O
with	O
the	O
decoupled	O
energy-power	O
advantage	O
of	O
flow	B-Algorithm
batteries	I-Algorithm
.	O
</s>
<s>
+	O
Comparison	O
of	O
flow	B-Algorithm
battery	I-Algorithm
compositions	O
Couple	O
Max	O
.	O
</s>
<s>
The	O
technical	O
merits	O
make	O
redox	B-Algorithm
flow	I-Algorithm
batteries	I-Algorithm
a	O
well-suited	O
option	O
for	O
large-scale	O
energy	O
storage	O
.	O
</s>
<s>
Flow	B-Algorithm
batteries	I-Algorithm
are	O
normally	O
considered	O
for	O
relatively	O
large	O
(	O
1kWh	O
–	O
10MWh	O
)	O
stationary	O
applications	O
with	O
multi-hour	O
charge-discharge	O
cycles	O
.	O
</s>
<s>
Flow	B-Algorithm
batteries	I-Algorithm
are	O
not	O
cost-efficient	O
for	O
shorter	O
charge/discharge	O
times	O
.	O
</s>
<s>
Some	O
examples	O
of	O
flow	B-Algorithm
battery	I-Algorithm
market	O
niches	O
are	O
:	O
</s>
<s>
Load	B-Algorithm
balancing	I-Algorithm
–	O
where	O
the	O
battery	O
is	O
attached	O
to	O
an	O
electrical	O
grid	O
to	O
store	O
excess	O
electrical	O
power	O
during	O
off-peak	O
hours	O
and	O
release	O
electrical	O
power	O
during	O
peak	O
demand	O
periods	O
.	O
</s>
<s>
The	O
common	O
problem	O
limiting	O
the	O
use	O
of	O
most	O
flow	B-Algorithm
battery	I-Algorithm
chemistries	O
in	O
this	O
application	O
is	O
their	O
low	O
areal	O
power	O
(	O
operating	O
current	O
density	O
)	O
which	O
translates	O
into	O
a	O
high	O
cost	O
of	O
power	O
.	O
</s>
<s>
Electric	O
vehicles	O
–	O
Because	O
flow	B-Algorithm
batteries	I-Algorithm
can	O
be	O
rapidly	O
"	O
recharged	O
"	O
by	O
replacing	O
the	O
electrolyte	O
,	O
they	O
can	O
be	O
used	O
for	O
applications	O
where	O
the	O
vehicle	O
needs	O
to	O
take	O
on	O
energy	O
as	O
fast	O
as	O
a	O
combustion	O
engined	O
vehicle	O
.	O
</s>
<s>
Zinc-chlorine	O
batteries	O
and	O
batteries	O
with	O
highly	O
soluble	O
halates	O
are	O
a	O
notable	O
exception	O
.	O
</s>
