<s>
The	O
lithium	B-Architecture
–	I-Architecture
air	I-Architecture
battery	I-Architecture
(	O
Li	O
–	O
air	O
)	O
is	O
a	O
metal	B-Architecture
–	I-Architecture
air	I-Architecture
electrochemical	I-Architecture
cell	I-Architecture
or	O
battery	O
chemistry	O
that	O
uses	O
oxidation	B-Operating_System
of	O
lithium	B-Language
at	O
the	O
anode	O
and	O
reduction	B-Operating_System
of	O
oxygen	O
at	O
the	O
cathode	O
to	O
induce	O
a	O
current	O
flow	O
.	O
</s>
<s>
Pairing	O
lithium	B-Language
and	O
ambient	O
oxygen	O
can	O
theoretically	O
lead	O
to	O
electrochemical	O
cells	O
with	O
the	O
highest	O
possible	O
specific	O
energy	O
.	O
</s>
<s>
Indeed	O
,	O
the	O
theoretical	O
specific	O
energy	O
of	O
a	O
non-aqueous	O
Li	O
–	O
air	O
battery	O
,	O
in	O
the	O
charged	O
state	O
with	O
Li2O2	O
product	O
and	O
excluding	O
the	O
oxygen	O
mass	O
,	O
is	O
~	O
40.1	O
MJ/kg	O
=	O
11.14	O
kWh/kg	O
of	O
lithium	B-Language
.	O
</s>
<s>
In	O
practice	O
,	O
Li	O
–	O
air	O
batteries	O
with	O
a	O
specific	O
energy	O
of	O
~	O
6.12	O
MJ/kg	O
=	O
1.7	O
kWh/kg	O
of	O
lithium	B-Language
at	O
the	O
cell	O
level	O
have	O
been	O
demonstrated	O
.	O
</s>
<s>
This	O
is	O
about	O
5	O
times	O
greater	O
than	O
that	O
of	O
a	O
commercial	O
lithium-ion	O
battery	O
,	O
and	O
is	O
sufficient	O
to	O
run	O
a	O
2,000	O
kg	O
electric	O
vehicle	O
for	O
~	O
on	O
a	O
single	O
charge	O
using	O
60kg	O
of	O
lithium	B-Language
(	O
i.e.	O
</s>
<s>
Theoretically	O
,	O
lithium	B-Language
–	O
air	O
can	O
achieve	O
12kW·	O
h/kg	O
(	O
43.2MJ/kg	O
)	O
excluding	O
the	O
oxygen	O
mass	O
.	O
</s>
<s>
Accounting	O
for	O
the	O
weight	O
of	O
the	O
full	O
battery	O
pack	O
(	O
casing	O
,	O
air	O
channels	O
,	O
lithium	B-Language
substrate	O
)	O
,	O
while	O
lithium	B-Language
alone	O
is	O
very	O
light	O
,	O
the	O
energy	O
density	O
is	O
considerably	O
lower	O
.	O
</s>
<s>
Although	O
the	O
idea	O
of	O
a	O
lithium	B-Architecture
–	I-Architecture
air	I-Architecture
battery	I-Architecture
was	O
around	O
long	O
before	O
1996	O
,	O
the	O
risk-to-benefit	O
ratio	O
was	O
perceived	O
as	O
too	O
high	O
to	O
pursue	O
.	O
</s>
<s>
Indeed	O
,	O
both	O
the	O
negative	O
(	O
lithium	B-Language
metal	O
)	O
and	O
the	O
positive	O
(	O
air	O
or	O
oxygen	O
)	O
electrodes	O
are	O
the	O
reasons	O
why	O
,	O
respectively	O
,	O
rechargeable	O
lithium-metal	O
batteries	O
failed	O
to	O
reach	O
the	O
market	O
in	O
the	O
1970s	O
(	O
the	O
lithium-ion	O
battery	O
in	O
a	O
mobile	O
device	O
uses	O
a	O
LiC6-graphite	O
compound	O
on	O
the	O
negative	O
electrode	O
,	O
not	O
a	O
lithium	B-Language
metal	O
)	O
.	O
</s>
<s>
Nevertheless	O
,	O
due	O
to	O
a	O
perceived	O
lack	O
of	O
other	O
alternatives	O
to	O
high	O
specific	O
energy	O
rechargeable	O
batteries	O
,	O
and	O
due	O
to	O
some	O
initially	O
promising	O
results	O
from	O
academic	O
labs	O
,	O
both	O
the	O
number	O
of	O
patents	O
and	O
of	O
free-domain	O
publications	O
related	O
to	O
lithium	B-Language
–	O
oxygen	O
(	O
including	O
Li	O
–	O
air	O
)	O
batteries	O
began	O
growing	O
exponentially	O
in	O
2006	O
.	O
</s>
<s>
In	O
general	O
lithium	B-Language
ions	O
move	O
between	O
the	O
anode	O
and	O
the	O
cathode	O
across	O
the	O
electrolyte	O
.	O
</s>
<s>
Under	O
discharge	O
,	O
electrons	O
follow	O
the	O
external	O
circuit	O
to	O
do	O
electric	O
work	O
and	O
the	O
lithium	B-Language
ions	O
migrate	O
to	O
the	O
cathode	O
.	O
</s>
<s>
During	O
charge	O
the	O
lithium	B-Language
metal	O
plates	O
onto	O
the	O
anode	O
,	O
freeing	O
at	O
the	O
cathode	O
.	O
</s>
<s>
Both	O
non-aqueous	O
(	O
with	O
Li2O2	O
or	O
LiO2	O
as	O
the	O
discharge	O
products	O
)	O
and	O
aqueous	O
(	O
LiOH	O
as	O
the	O
discharge	O
product	O
)	O
Li-O2	B-Architecture
batteries	O
have	O
been	O
considered	O
.	O
</s>
<s>
Lithium	B-Language
metal	O
is	O
the	O
typical	O
anode	O
choice	O
.	O
</s>
<s>
At	O
the	O
anode	O
,	O
electrochemical	O
potential	O
forces	O
the	O
lithium	B-Language
metal	O
to	O
release	O
electrons	O
via	O
oxidation	B-Operating_System
(	O
without	O
involving	O
the	O
cathodic	O
oxygen	O
)	O
.	O
</s>
<s>
Lithium	B-Language
has	O
high	O
specific	O
capacity	O
(	O
3840mAh/g	O
)	O
compared	O
with	O
other	O
metal	B-Architecture
–	I-Architecture
air	I-Architecture
battery	I-Architecture
materials	O
(	O
820mAh/g	O
for	O
Zinc	O
,	O
2965mAh/g	O
for	O
aluminium	O
)	O
.	O
</s>
<s>
Lithium	B-Language
anodes	O
risk	O
dendritic	O
lithium	B-Language
deposits	O
,	O
decreasing	O
energy	O
capacity	O
or	O
triggering	O
a	O
short	B-Application
circuit	I-Application
.	O
</s>
<s>
Upon	O
charging/discharging	O
in	O
aprotic	O
cells	O
,	O
layers	O
of	O
lithium	B-Language
salts	O
precipitate	O
onto	O
the	O
anode	O
,	O
eventually	O
covering	O
it	O
and	O
creating	O
a	O
barrier	O
between	O
the	O
lithium	B-Language
and	O
electrolyte	O
.	O
</s>
<s>
The	O
uneven	O
current	O
distribution	O
furthers	O
branching	O
dendrite	O
growth	O
and	O
typically	O
leads	O
to	O
a	O
short	B-Application
circuit	I-Application
between	O
the	O
anode	O
and	O
cathode	O
.	O
</s>
<s>
In	O
aqueous	O
cells	O
problems	O
at	O
the	O
SEI	O
stem	O
from	O
the	O
high	O
reactivity	O
of	O
lithium	B-Language
metal	O
with	O
water	O
.	O
</s>
<s>
According	O
to	O
Seeo	O
,	O
Inc.	O
,	O
such	O
electrolytes	O
(	O
e.g.	O
,	O
polystyrene	O
with	O
the	O
high	O
Li-ion	O
conductivity	O
of	O
a	O
soft	O
polymer	B-Language
segment	O
,	O
such	O
as	O
a	O
poly( ethylene	O
oxide	O
(	O
PEO	O
)	O
and	O
Li-salt	O
mixture	O
)	O
)	O
combine	O
the	O
mechanical	O
stability	O
of	O
a	O
hard	O
polymer	B-Language
segment	O
with	O
the	O
high	O
ionic	O
conductivity	O
of	O
the	O
soft	O
polymer	B-Language
–	O
lithium-salt	O
mixture	O
.	O
</s>
<s>
Li-ion	O
conducting	O
glass	O
or	O
glass-ceramic	O
materials	O
are	O
(	O
generally	O
)	O
readily	O
reduced	O
by	O
lithium	B-Language
metal	O
,	O
and	O
therefore	O
a	O
thin	O
film	O
of	O
a	O
stable	O
lithium	B-Language
conducting	O
material	O
,	O
such	O
as	O
or	O
,	O
can	O
be	O
inserted	O
between	O
the	O
ceramic	O
and	O
metal	O
.	O
</s>
<s>
This	O
ceramic-based	O
SEI	O
inhibits	O
the	O
formation	O
of	O
dendrites	O
and	O
protects	O
the	O
lithium	B-Language
metal	O
from	O
atmospheric	O
contamination	O
.	O
</s>
<s>
At	O
the	O
cathode	O
during	O
charge	O
,	O
oxygen	O
donates	O
electrons	O
to	O
the	O
lithium	B-Language
via	O
reduction	B-Operating_System
.	O
</s>
<s>
Mesoporous	O
carbon	O
has	O
been	O
used	O
as	O
a	O
cathode	O
substrate	O
with	O
metal	O
catalysts	O
that	O
enhance	O
reduction	B-Operating_System
kinetics	O
and	O
increase	O
the	O
cathode	O
's	O
specific	O
capacity	O
.	O
</s>
<s>
Based	O
on	O
the	O
first	O
pore-scale	O
modeling	O
of	O
lithium	B-Architecture
–	I-Architecture
air	I-Architecture
batteries	I-Architecture
,	O
the	O
micro-structure	O
of	O
the	O
cathode	O
significantly	O
affects	O
battery	O
capacity	O
in	O
both	O
non-pore-blocking	O
and	O
pore-blocking	O
regimes	O
.	O
</s>
<s>
Incomplete	O
discharge	O
due	O
to	O
blockage	O
of	O
the	O
porous	O
carbon	O
cathode	O
with	O
discharge	O
products	O
such	O
as	O
lithium	B-Language
peroxide	O
(	O
in	O
aprotic	O
designs	O
)	O
is	O
the	O
most	O
serious	O
.	O
</s>
<s>
Catalysts	O
have	O
shown	O
promise	O
in	O
creating	O
preferential	O
nucleation	O
of	O
over	O
,	O
which	O
is	O
irreversible	O
with	O
respect	O
to	O
lithium	B-Language
.	O
</s>
<s>
In	O
a	O
cell	O
with	O
an	O
aprotic	O
electrolyte	O
lithium	B-Language
oxides	O
are	O
produced	O
through	O
reduction	B-Operating_System
at	O
the	O
cathode	O
:	O
</s>
<s>
Lithium	B-Language
oxides	O
are	O
insoluble	O
in	O
aprotic	O
electrolytes	O
,	O
which	O
leads	O
to	O
cathode	O
clogging	O
.	O
</s>
<s>
A	O
nanowire	O
array	O
cathode	O
augmented	O
by	O
a	O
genetically	O
modified	O
M13	O
bacteriophage	O
virus	O
offers	O
two	O
to	O
three	O
times	O
the	O
energy	O
density	O
of	O
2015-era	O
lithium-ion	O
batteries	O
.	O
</s>
<s>
In	O
a	O
cell	O
with	O
an	O
aqueous	O
electrolyte	O
the	O
reduction	B-Operating_System
at	O
the	O
cathode	O
can	O
also	O
produce	O
lithium	B-Language
hydroxide	O
:	O
</s>
<s>
An	O
aqueous	O
Li	O
–	O
air	O
battery	O
consists	O
of	O
a	O
lithium	B-Language
metal	O
anode	O
,	O
an	O
aqueous	O
electrolyte	O
and	O
a	O
porous	O
carbon	O
cathode	O
.	O
</s>
<s>
The	O
aqueous	O
electrolyte	O
combines	O
lithium	B-Language
salts	O
dissolved	O
in	O
water	O
.	O
</s>
<s>
However	O
,	O
lithium	B-Language
metal	O
reacts	O
violently	O
with	O
water	O
and	O
thus	O
the	O
aqueous	O
design	O
requires	O
a	O
solid	O
electrolyte	O
interface	O
between	O
the	O
lithium	B-Language
and	O
electrolyte	O
.	O
</s>
<s>
Commonly	O
,	O
a	O
lithium-conducting	O
ceramic	O
or	O
glass	O
is	O
used	O
,	O
but	O
conductivity	O
are	O
generally	O
low	O
(	O
on	O
the	O
order	O
of	O
10−3	O
S/cm	O
at	O
ambient	O
temperatures	O
)	O
.	O
</s>
<s>
Water	O
molecules	O
are	O
involved	O
in	O
the	O
redox	B-Operating_System
reactions	O
at	O
the	O
air	O
cathode	O
.	O
</s>
<s>
The	O
first	O
pore	O
system	O
serves	O
as	O
an	O
oxidation	B-Operating_System
product	O
store	O
.	O
</s>
<s>
Most	O
effort	O
involved	O
aprotic	O
materials	O
,	O
which	O
consist	O
of	O
a	O
lithium	B-Language
metal	O
anode	O
,	O
a	O
liquid	O
organic	O
electrolyte	O
and	O
a	O
porous	O
carbon	O
cathode	O
.	O
</s>
<s>
The	O
electrolyte	O
can	O
be	O
made	O
of	O
any	O
organic	O
liquid	O
able	O
to	O
solvate	O
lithium	B-Language
salts	O
such	O
as	O
,	O
,	O
,	O
and	O
,	O
but	O
typically	O
consisted	O
of	O
carbonates	O
,	O
ethers	B-Application
and	O
esters	O
.	O
</s>
<s>
A	O
major	O
advantage	O
is	O
the	O
spontaneous	O
formation	O
of	O
a	O
barrier	O
between	O
anode	O
and	O
electrolyte	O
(	O
analogous	O
to	O
the	O
barrier	O
formed	O
between	O
electrolyte	O
and	O
carbon	O
–	O
lithium	B-Language
anodes	O
in	O
conventional	O
Li-ion	O
batteries	O
)	O
that	O
protects	O
the	O
lithium	B-Language
metal	O
from	O
further	O
reaction	O
with	O
the	O
electrolyte	O
.	O
</s>
<s>
Although	O
most	O
studies	O
agree	O
that	O
is	O
the	O
final	O
discharge	O
product	O
of	O
non-aqueous	O
Li-O2	B-Architecture
batteries	O
,	O
considerable	O
evidence	O
that	O
its	O
formation	O
does	O
not	O
proceed	O
as	O
a	O
direct	O
2-electron	O
electroreduction	O
to	O
peroxide	O
O	O
(	O
which	O
is	O
the	O
common	O
pathway	O
for	O
O2	O
reduction	B-Operating_System
in	O
water	O
on	O
carbon	O
)	O
but	O
rather	O
via	O
a	O
one	O
–	O
electron	O
reduction	B-Operating_System
to	O
superoxide	O
O	O
,	O
followed	O
by	O
its	O
disproportionation	O
:	O
</s>
<s>
Superoxide	O
(	O
O	O
)	O
has	O
traditionally	O
been	O
considered	O
as	O
a	O
dangerous	O
intermediate	O
in	O
aprotic	O
oxygen	O
batteries	O
due	O
to	O
its	O
high	O
nucleophilicity	O
,	O
basicity	O
and	O
redox	B-Operating_System
potential	O
However	O
,	O
reports	O
suggest	O
that	O
LiO2	O
is	O
both	O
an	O
intermediate	O
during	O
the	O
discharge	O
to	O
peroxide	O
(	O
)	O
and	O
can	O
be	O
used	O
as	O
the	O
final	O
discharge	O
product	O
,	O
potentially	O
with	O
an	O
improved	O
cycle	O
life	O
albeit	O
with	O
a	O
lower	O
specific	O
energy	O
(	O
a	O
little	O
heavier	O
battery	O
weight	O
)	O
.	O
</s>
<s>
Pt/C	O
seems	O
to	O
be	O
the	O
best	O
electrocatalyst	O
for	O
O2	O
evolution	O
and	O
Au/C	O
for	O
O2	O
reduction	B-Operating_System
when	O
is	O
the	O
product	O
.	O
</s>
<s>
Nevertheless	O
,	O
"	O
the	O
performance	O
of	O
rechargeable	O
lithium	B-Architecture
–	I-Architecture
air	I-Architecture
batteries	I-Architecture
with	O
non-aqueous	O
electrolytes	O
is	O
limited	O
by	O
the	O
reactions	O
on	O
the	O
oxygen	O
electrode	O
,	O
especially	O
by	O
O2	O
evolution	O
.	O
</s>
<s>
The	O
capacity	O
(	O
in	O
mAh/cm2	O
)	O
and	O
the	O
cycle	O
life	O
of	O
non-aqueous	O
Li-O2	B-Architecture
batteries	O
is	O
limited	O
by	O
the	O
deposition	O
of	O
insoluble	O
and	O
poorly	O
electronically	O
conducting	O
LiOx	O
phases	O
upon	O
discharge	O
.	O
</s>
<s>
This	O
makes	O
the	O
practical	O
specific	O
energy	O
of	O
Li-O2	B-Architecture
batteries	O
significantly	O
smaller	O
than	O
the	O
reagent-level	O
calculation	O
predicts	O
.	O
</s>
<s>
The	O
common	O
feature	O
of	O
hybrid	O
designs	O
is	O
a	O
two-part	O
(	O
one	O
part	O
aqueous	O
and	O
one	O
part	O
aprotic	O
)	O
electrolyte	O
connected	O
by	O
a	O
lithium-conducting	O
membrane	O
.	O
</s>
<s>
A	O
lithium-conducting	O
ceramic	O
is	O
typically	O
employed	O
as	O
the	O
membrane	O
joining	O
the	O
two	O
electrolytes	O
.	O
</s>
<s>
3	O
)	O
is	O
one	O
such	O
alternative	O
approaches	O
that	O
allows	O
for	O
a	O
combination	O
of	O
a	O
lithium	B-Language
metal	O
anode	O
with	O
an	O
aqueous	O
cathode	O
.	O
</s>
<s>
In	O
contrast	O
,	O
solid	O
polymer	B-Language
electrolytes	O
(	O
SPEs	O
)	O
can	O
provide	O
a	O
higher	O
conductivity	O
at	O
the	O
expense	O
of	O
a	O
faster	O
crossover	O
of	O
water	O
and	O
of	O
other	O
small	O
molecules	O
that	O
are	O
reactive	O
toward	O
metallic	O
Li	O
.	O
</s>
<s>
Among	O
the	O
more	O
exotic	O
membranes	O
considered	O
for	O
Li-O2	B-Architecture
batteries	O
is	O
single-crystal	O
silicon	O
.	O
</s>
<s>
In	O
2015	O
researchers	O
announced	O
a	O
design	O
that	O
used	O
highly	O
porous	O
graphene	O
for	O
the	O
anode	O
,	O
an	O
electrolyte	O
of	O
lithium	B-Language
bis(trifluoromethyl )	O
sulfonylimide/dimethoxyethane	O
with	O
added	O
water	O
and	O
lithium	B-Language
iodide	O
for	O
use	O
as	O
a	O
"	O
mediator	O
"	O
.	O
</s>
<s>
The	O
electrolyte	O
produces	O
lithium	B-Language
hydroxide	O
(	O
LiOH	O
)	O
at	O
the	O
cathode	O
instead	O
of	O
lithium	B-Language
peroxide	O
(	O
)	O
.	O
</s>
<s>
Current	O
solid-state	O
Li	O
–	O
air	O
batteries	O
use	O
a	O
lithium	B-Language
anode	O
,	O
a	O
ceramic	O
,	O
glass	O
,	O
or	O
glass-ceramic	O
electrolyte	O
,	O
and	O
a	O
porous	O
carbon	O
cathode	O
.	O
</s>
<s>
The	O
anode	O
and	O
cathode	O
are	O
typically	O
separated	O
from	O
the	O
electrolyte	O
by	O
polymer	B-Language
–	O
ceramic	O
composites	O
that	O
enhance	O
charge	O
transfer	O
at	O
the	O
anode	O
and	O
electrochemically	O
couple	O
the	O
cathode	O
to	O
the	O
electrolyte	O
.	O
</s>
<s>
The	O
polymer	B-Language
–	O
ceramic	O
composites	O
reduce	O
overall	O
impedance	O
.	O
</s>
<s>
The	O
ionic	O
conductivity	O
of	O
current	O
lithium	B-Language
fast	O
ion	O
conductors	O
is	O
lower	O
than	O
liquid	O
electrolyte	O
alternatives	O
.	O
</s>
<s>
Incomplete	O
discharge	O
due	O
to	O
blockage	O
of	O
the	O
porous	O
carbon	O
cathode	O
with	O
discharge	O
products	O
such	O
as	O
lithium	B-Language
peroxide	O
(	O
in	O
aprotic	O
designs	O
)	O
is	O
the	O
most	O
serious	O
.	O
</s>
<s>
Catalysts	O
have	O
shown	O
promise	O
in	O
creating	O
preferential	O
nucleation	O
of	O
over	O
,	O
which	O
is	O
irreversible	O
with	O
respect	O
to	O
lithium	B-Language
.	O
</s>
<s>
Several	O
catalysts	O
improve	O
cathode	O
performance	O
,	O
notably	O
,	O
and	O
the	O
mechanism	O
of	O
improvement	O
is	O
known	O
as	O
surface	O
oxygen	O
redox	B-Operating_System
providing	O
abundant	O
initial	O
growth	O
sites	O
for	O
lithium	B-Language
peroxide	O
.	O
</s>
<s>
Current	O
cell	O
designs	O
show	O
poor	O
resistance	O
to	O
oxidation	B-Operating_System
by	O
reaction	O
products	O
and	O
intermediates	O
.	O
</s>
<s>
One	O
version	O
of	O
the	O
hybrid	O
used	O
a	O
potassium-ion	B-Algorithm
battery	I-Algorithm
using	O
potassium	O
–	O
air	O
.	O
</s>
<s>
The	O
latest	O
device	O
essentially	O
substituted	O
lithium	B-Language
for	O
potassium	O
.	O
</s>
<s>
Captured	O
sunlight	O
produced	O
electrons	O
that	O
decompose	O
lithium	B-Language
peroxide	O
into	O
lithium	B-Language
ions	O
,	O
thereby	O
charging	O
the	O
battery	O
.	O
</s>
<s>
During	O
discharge	O
,	O
oxygen	O
from	O
air	O
replenished	O
the	O
lithium	B-Language
peroxide	O
.	O
</s>
