Virus constructed iron phosphate lithium ion batteries in
unmanned aircraft systems
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Citation
Kolesnikov-Lindsey, Rachel, Mark Allen, and Angela Belcher.
Virus Constructed Iron Phosphate Lithium Ion Batteries in
Unmanned Aircraft Systems. In 2010 IEEE Conference on
Innovative Technologies for an Efficient and Reliable Electricity
Supply, 171-176. Institute of Electrical and Electronics
Engineers, 2010. © 2010 IEEE.
As Published
http://dx.doi.org/10.1109/CITRES.2010.5619817
Publisher
Institute of Electrical and Electronics Engineers
Version
Final published version
Accessed
Thu May 26 00:23:29 EDT 2016
Citable Link
http://hdl.handle.net/1721.1/79400
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Detailed Terms
Virus
Constructed
Iron
Phosphate
Lithium
Ion
Batteries
in
Unmanned
Aircraft
Systems
2Lt
Rachel
Kolesnikov‐Lindsey+,
Mark
Allen,
Angela
Belcher
Department
of
Materials
Science,
Massachusetts
Institute
of
Technology
Cambridge,
MA
02139
+Phone:
609‐230‐8967,
email:
RachelKL@alum.mit.edu
available,
unlike
cobalt
oxide
cathodes
[1].
The
potential
difference
between
FePO4
and
the
lithium
metal
cathode
is
3.4
volts.
Abstract
FePO4
lithium
ion
batteries
that
have
cathodes
constructed
by
viruses
are
scaled
up
in
size
to
examine
potential
for
use
as
an
auxiliary
battery
in
the
Raven
to
power
the
payload
equipment.
These
batteries
are
assembled
at
standard
temperature
and
pressure,
yet
are
consistently
able
to
achieve
20nm
FePO4
particle
size,
creating
higher
energy
density.
However,
FePO4
cathodes
do
have
kinetic
limitations
that
can
cause
a
decrease
in
capacity
with
cycling
and
reduced
charge/discharge
rates[3].
To
overcome
this
limitation,
many
scientists
have
tried
to
increase
kinetics
by
decreasing
particle
size
to
the
nano‐scale
to
increase
rate
of
transport
by
increasing
surface
area
relative
to
volume
of
each
small
particle.
However,
manufacturing
nanoparticles
of
FePO4
has
proven
difficult
and
very
expensive,
as
current
techniques
require
a
high
temperature
and
pressure
fabrication
process.
Even
with
this
expensive
process,
the
smallest
manufactured
FePO4
particles
are
between
20‐40
nm[3].
Conductivity
is
increased
in
the
scale
up
of
the
cathodes
by
integrating
a
stainless
steel
mesh
to
the
design.
A
prototype
auxiliary
battery
design
is
created,
tested,
and
refined
to
determine
how
virally
constructed
FePO4
batteries
behave
as
they
are
scaled
up.
1 INTRODUCTION
Instead
of
expensive
machine
processing
to
create
FePO4
cathodes,
the
Belcher
Lab
at
MIT
has
taken
an
entirely
different
approach.
The
Belcher
Lab
has
discovered
a
way
to
genetically
reprogram
a
strain
of
M13
bacteriophage
so
that
the
bacteriophage
itself
constructs
the
iron
phosphate
cathodes
for
rechargeable
lithium
ion
batteries.
Like
standard
batteries,
lithium
ion
batteries
are
driven
by
a
potential
difference
between
a
cathode
and
anode
material.
The
anode
acts
as
the
source
of
lithium
ions
and,
in
many
cases,
is
simply
pure
lithium
metal.
The
cathode
functions
as
a
lithium
ion
sink
that
should
be
optimized
along
several
parameters.
An
ideal
cathode
is
made
of
a
stable,
low‐cost
material
that
readily
reacts
with
lithium.
The
cathode
should
have
a
material
structure
that
can
accommodate
lithium
ions
without
any
significant
strain
or
change
in
conformation.
The
cathode
should
also
have
high
capacity,
high
power
density,
and
high
potential
difference
from
the
anode,
leading
to
a
high
voltage
[1]
Virally
Constructed
Battery
Specifications
The
DNA
of
the
M13
bacteriophage
has
been
reprogrammed
so
that
the
major
surface
protein
coat,
pVIII,
has
a
strong
affinity
for
metals.
After
the
M13
is
amplified
in
solution,
iron
is
then
added
to
the
solution.
This
iron
attaches
securely
to
the
pVIII
protein
on
the
surface
of
the
M13.
The
iron
is
then
reduced
with
a
phosphate
such
that
the
entire
phage
is
encapsulated
with
FePO4,
as
seen
in
Figure
1.
In
1996,
John
Goodenough
of
the
University
of
Texas
was
looking
for
a
transition
metal
material
with
an
open
structure
that
could
easily
accommodate
lithium
ions
into
its
structure
during
discharge
without
high
material
strain
or
structure
change.
He
found
LiFePO4
to
be
a
promising
cathode
material
in
lithium
ion
batteries[2].
As
a
cathode
material,
iron
phosphate
is
lower
in
cost
than
many
other
common
cathodes
because
is
it
composed
of
elements
that
are
readily
978-1-4244-6077-9/10/$26.00 ©2010 IEEE
This
solution
is
then
dehydrated
so
that
only
a
powdery
material
that
is
the
FePO4
coated
phage
remains.
The
171
payload
housed
in
the
nose
of
the
aircraft.
This
payload
can
be
either
a
high
resolution
camera
for
daylight
hours
or
a
thermal
imaging
camera
for
night
missions[4].
The
entire
system
disassembles
to
fit
into
a
backpack
carrying‐unit
that
also
houses
the
support
equipment,
ground
control
unit,
remote
video
terminal,
as
well
as
an
additional
Raven.
The
ease
of
use
and
portability
of
this
system
make
it
ideal
for
soldiers
in
the
combat
environment.
A
two‐
week
training
class
is
all
one
needs
to
learn
the
specifics
of
operating
a
Raven,
as
opposed
to
almost
a
year
of
pilot
training
for
larger
UAS
like
the
Predator.
The
primary
mission
of
the
Raven
is
reconnaissance,
or
the
observation
of
a
region
to
gain
information
on
the
enemy
or
a
specific
region.
It
can
quickly
be
unpacked
and
assembled
on
location
and
then
launched
by
a
soldier.
By
flying
over
and
filming
a
target,
the
Raven
increases
situational
awareness
of
what
is
happening
on
the
other
side
of
a
hill
or
to
collect
location
information
on
a
target[4].
The
data
from
the
Raven
is
broadcast
to
the
ground
control
unit,
and
has
the
option
of
also
being
streamed
elsewhere,
for
example
to
an
armed
helicopter
waiting
around
the
corner
to
attack
a
target
once
it
is
confirmed
by
the
Raven[5].
The
Raven
can
either
fly
a
preplanned
route,
or
be
remote
operated
by
a
soldier
on
the
ground.
Figure
1:
The
modified
DNA
of
the
bacteriophage
gives
its
surface
protein
a
strong
affinity
for
metals,
allowing
FePO4
to
be
attached
to
form
the
cathode
of
the
battery.
phage
is
then
combined
in
a
mixture
that
is
70%
FePO4
coated
phage,
25%
carbon
black
Super
P,
and
5%
poly(tetrafluoroethylene),
or
PTFE.
The
carbon
black
is
added
to
increase
electronic
conductivity
in
the
cathode
and
the
PTFE
serves
as
a
binder
to
help
ensure
the
cathode
sticks
together.
This
mixture
is
hand
ground
with
a
mortar
and
pestle
for
20
minutes
to
ensure
thorough
mixing.
It
is
then
rolled
out
on
a
stainless
steel
mat
into
a
cathode.
In
an
argon
glove
box,
this
cathode,
along
with
a
lithium
metal
anode,
come
together
to
build
a
battery.
Using
several
different
stains
of
the
virus,
the
Belcher
Lab
has
been
able
to
build
Li
ion
batteries
with
capacities
of
140mAh/g
that
is
maintained
for
over
50
charge
cycles
[3].
Raven
Unmanned
Aircraft
System
(UAS)
Figure
2:
The
Raven
UAS
is
3
feet
long
with
a
4.5
feet
wing
span.
Image
from
the
Spanish
Army.
Military
Unmanned
Aircraft
Systems
(UAS)
are
a
market
that
has
grown
significantly
over
the
past
10
years.
The
number
of
UAS
in
use
by
the
United
States
military
and
(to
a
lesser
extent)
militaries
worldwide
continues
to
steadily
increase.
2 BODY
Auxiliary
Battery
Potential
The
Raven
is
the
most
advanced
small
UAS
available
today.
The
Marines,
Army,
and
Air
Force
have
increasingly
adopted
it
since
its
development
in
2004.
Weighing
in
at
a
mere
4.2
pounds,
the
aircraft
is
3
feet
long
and
has
a
wingspan
of
4.5
feet
(Figure
2).
The
system
is
hand
launched
by
a
soldier,
after
which
the
onboard
engine
propels
flight.
It
has
a
fly
time
of
60‐90
minutes
and
can
reach
speeds
of
30‐60
miles
per
hour.
However,
due
to
the
draw
on
the
battery
during
take
off
and
navigation,
the
Raven
has
a
limited
range
of
8‐12
kilometers.
This
low
altitude
system
is
equipped
with
a
172
The
unit
is
currently
powered
by
a
single
lithium‐ion
polymer
battery
that
sits
in
the
right
side
of
the
body
of
the
Raven.
In
addition
to
powering
the
initial
climb
to
altitude,
navigation,
cruise
at
altitude,
and
decent,
the
main
battery
also
feels
the
constant
draw
of
the
payload
equipment.
This
is
what
limits
the
Raven
to
a
flight
time
of
just
over
an
hour
and
range
of
about
10
kilometers.
A
small
range
not
only
limits
how
much
soldiers
are
able
to
see,
but
in
many
cases
means
they
must
be
dangerously
close
to
a
suspected
target
in
order
to
survey
it.
designed
in
a
way
that
it
will
require
minimal
re‐
engineering
of
the
Raven.
This
said,
an
ideal
location
for
an
auxiliary
battery
is
directly
into
the
back
of
the
detachable
nose
of
the
Raven.
This
configuration
would
power
the
payload
of
the
Raven,
which
is
also
housed
in
the
nose,
delivering
power
directly
without
needing
to
redesign
the
existing
configuration
of
the
aircraft.
The
design
seen
in
Figure
3
has
the
exact
dimensions
of
the
back
of
the
nose
cavity
and
would
be
able
to
sit
along
the
inside,
still
allowing
normal
nose
attachment.
Incorporating
a
high
energy
density,
virally
constructed
lithium‐ion
battery
into
the
Raven
could
alleviate
these
problems.
We
propose
the
auxiliary
battery
be
used
entirely
to
power
the
payload
of
the
system.
This
would
remove
strain
from
the
primary
battery,
leaving
its
sole
purpose
to
be
powering
flight
of
the
aircraft.
After
being
launched,
the
initial
climb
to
operating
altitude
is
a
taxing
activity,
as
are
navigational
accelerations
and
turns
in
flight.
By
removing
the
additional
stress
of
also
having
a
constant
draw
of
energy
on
the
main
battery
from
the
payload,
an
auxiliary
battery
would
lengthen
fly
time.
With
an
average
speed
of
just
under
50
miles
per
hour,
every
extra
15
minutes
of
flight
could
add
over
10
extra
miles
(16
kilometers)
of
ground
covered,
which
almost
doubles
the
range.
This
could
further
remove
soldiers
from
areas
of
danger,
allowing
them
to
operate
the
Raven
well
outside
of
the
line
of
fire.
Figure
3a
shows
the
design
for
an
8.5
by
11.5
cm
stainless
steel
plate
casing
for
this
battery
design.
The
casing
could
also
be
made
of
aluminum
to
decrease
weight.
There
are
eight
drill
holes
along
the
outside
of
the
plate
for
nylon
screws
to
hold
the
entire
battery
together.
Figure
3b
shows
a
profile
view
of
the
prototype.
The
electrolyte
in
the
center
of
the
battery
is
surrounded
on
both
sides
with
a
custom
cut
polypropylene
layer.
On
one
side,
there
is
a
large
sheet
of
lithium
metal
to
act
as
the
anode.
On
the
other
side,
the
cathode
material
and
metal
mesh
combination
sit.
Running
along
the
perimeter
of
the
steel
casing,
there
is
a
Silicon
Gasket
to
seal
the
enclosed
battery
components
from
the
outside
environment
and
particularly
to
keep
oxygen
from
reaching
the
lithium
metal.
The
screws
go
through
the
metal
casing,
gasket,
and
polypropylene
layers
to
seal
the
battery.
This
sort
of
a
design
could
be
made
with
primarily
off‐the‐shelf
or
easily
manufactured
parts
for
the
screws,
steel
casing,
gasket
material,
and
polypropylene
separators.
The
anode
is
simply
a
piece
of
lithium
metal,
cut
to
size.
This
auxiliary
battery
could
also
be
used
to
operate
a
more
powerful
payload.
Currently,
there
are
two
different
nosepieces
that
carry
the
two
available
payloads
that
can
be
swapped
out
for
one
another
depending
on
time
of
day
of
the
mission.
With
an
auxiliary
power
source,
Ravens
could
be
outfitted
with
more
advanced
payloads,
such
as
one
that
can
actively
lock
onto
and
follow
a
target,
like
some
larger
UAS
are
able
to
do[5].
These
advanced
payloads
are
not
currently
being
used
on
the
Raven
because
they
consume
more
energy
and
would
decrease
the
range
and
fly
time
to
a
point
that
having
them
aboard
is
no
longer
useful
because
fly
time
is
not
long
enough
to
reach
the
target.
Additional
payloads
could
be
designed
to
fit
in
the
same
housing
of
the
nose
cavity
and
could
easily
be
swapped
in
for
one
another
depending
on
the
mission
of
the
Raven
at
the
time.
This
adaptability
would
give
this
easily
portable
UAS
a
broader
range
of
capabilities,
enabling
resources
to
ground
soldiers
that
are
currently
not
readily
available.
The
market
for
UAS
is
thriving.
The
United
States
Army,
Marines
and
Air
Force
are
both
increasing
use
of
these
systems
as
a
way
of
gathering
surveillance
data
without
risking
the
lives
of
soldiers.
As
of
early
2009,
AeroVironment,
the
California
based
company
that
produces
the
Raven,
had
delivered
over
9000
units
to
customers
world
wide
[6].
In
February
2
010,
the
US
Army
and
Marine
Corps
ordered
$39.7
million
of
Raven
Systems
and
spare
parts
from
AeroVironment
[7].
Furthermore,
Italy,
Denmark,
the
Netherlands,
and
Spain
have
already
purchased
Ravens
[7].
Proposed
Auxiliary
Battery
Design
The
auxiliary
battery
should
be
as
easy
as
possible
to
incorporate.
The
battery
technology
needs
to
be
Figure
3:
Prototype
design
of
a
housing
for
a
battery
that
could
fit
into
the
nose
of
a
Raven,
behind
existing
payload
equipment.
a)
Front
view
of
design
with
exact
dimensions
of
nose
b)
Profile
view
to
show
layering
173
Battery
Scale
Up
With
Metal
Mesh
One
fear
in
scaling
up
the
size
of
the
battery
cathodes
is
a
decrease
in
electronic
conductivity.
As
cathode
size
is
increased
from
the
1‐5mg
size
of
previous
batteries
made
in
the
Belcher
lab
to
10
or
100
times
that,
there
is
concern
that
the
larger
and
thicker
dimensions
of
the
cathodes
will
interfere
with
the
electron’s
ability
to
diffuse.
By
incorporating
a
strong
electronic
conductor,
such
as
metal
into
the
cathode,
electrons
would
have
a
clear
and
easy
path
to
travel
along.
This
prompted
the
idea
of
incorporating
a
metal
mesh
into
the
cathode.
Two
types
of
stainless
steel
mesh
316SS
“super
corrosion
resistant
steel”
were
purchased.
One
was
a
finer
grade
mesh
with
250
holes
per
inch
of
metal.
Each
hole
had
a
diameter
of
0.1016
mm
including
the
wire,
or
0.0610
mm
diameter
area
of
open
space
per
hole.
The
other
mesh
was
of
a
coarser
grade
of
62
holes
per
inch
of
metal.
This
gave
each
hole
a
diameter
of
0.4097
mm
including
the
wire,
or
a
0.2954
mm
diameter
of
open
space
per
hole.
The
difference
in
appearance
of
these
stainless
steel
meshes
can
be
seen
in
Figure
4.
It
is
also
important
to
point
out
that
incorporating
the
metal
mesh
does
not
change
any
of
the
unique
properties
that
make
the
virally
constructed
batteries
desirable.
The
chemistry
of
the
battery
itself
remains
entirely
the
same,
since
the
metal
mesh
just
acts
as
an
added
source
of
electronic
conductivity.
Additionally,
the
cathode
is
still
flexible
and
can
be
bent
into
any
shape.
While
the
metal
mesh
does
add
some
challenge
of
shaping
without
allowing
the
cathode
material
to
flake
off,
the
same
problem
would
be
encountered
if
trying
to
shape
an
already
made,
metal‐meshless,
brittle
cathode.
Additionally,
the
metal
acts
as
a
backbone
that,
once
shaped,
will
maintain
its
shape
and
add
strength
to
the
structure.
Layering
Cathodes
By
incorporating
the
metal
mesh,
we
determined
a
way
to
create
larger
cathodes
that
maintained
high
electronically
conductivity
to
ensure
first‐rate
performance.
However,
the
large,
flat,
yet
very
thin
shape
of
the
cathode
is
not
inherently
conducive
to
creating
compact
batteries
with
high
energy
density.
However,
by
stacking
layers
of
the
metal
mesh
cathodes
on
top
of
one
another,
it
is
possible
to
increase
the
amount
of
active
material
contained
in
a
small
space
without
sacrificing
electrical
conductivity.
Figure
4:
Metal
Mesh
was
incorporated
into
cathodes
to
increase
electronic
conductivity.
Three
different
cathodes
of
roughly
20
mg
each
were
prepared
from
a
single
60
mg
blend
of
FePO4
coated
phage,
carbon
black
super
P
and
PTFE,
mixed
as
previously
described.
One
cathode
was
rolled
onto
the
fine
metal
mesh,
one
on
the
coarser
grade
metal
mesh,
and
one
prepared
as
previously
done
with
no
metal
mesh.
After
assembling
them
into
coin
cell
batteries,
the
performance
of
each
type
of
cathode
was
directly
compared
using
the
Solartron
Analytical
to
cycle
the
batteries
from
4.3
volts
to
2
volts
at
a
rate
of
C/10.
As
can
be
seen
in
Figure
14
below,
both
types
of
metal
mesh
yielded
a
higher
capacity
than
the
cathode
with
no
mesh
incorporated
into
it,
which
showed
a
maximum
capacity
of
84
mAh/g.
Furthermore,
the
cathode
of
active
material
incorporated
into
fine
grade
mesh
out
performed
the
cathode
with
coarse
mesh,
with
a
maximum
capacity
of
93.7
mAh/g
compared
to
88.7
mAh/g
capacity
of
the
coarse
mesh
cathode.
As
a
result,
the
fine
grade
stainless
steel
mesh
(250
holes
per
inch)
was
incorporated
into
all
future
cathodes.
A
battery
with
one
9mg
cathode
on
metal
mesh
was
prepared
along
side
a
battery
with
three
cathode
layers
with
9mg
of
active
material
in
each
layer.
These
two
batteries
were
directly
compared
in
cycling
between
2
to
4.3
volts.
There
was
no
decrease
in
performance
in
the
three‐layered‐cathode
battery
in
comparison
to
the
single‐cathode‐layer
battery.
Prototype
testing
To
test
this
design,
a
smaller
version
of
the
blueprint
was
made
and
tested.
We
machined
1.5
inch
by
1.5
stainless
steel
plates
to
be
used
for
the
casing.
Red
silicon
gasket
material
(of
thickness
1/16
inch)
was
hand
cut
to
size
with
a
razor.
Using
the
steel
plate
as
a
174
an
airtight
seal
around
them.
Alumina
screws
were
used
to
hold
the
conflat
together
as
they
are
non‐
conducting.
The
design
can
be
seen
in
Figure
5
and
the
fully
assembled
conflat
in
Figure
6.
template,
holes
were
drilled
into
the
silicon
gasket
to
allow
a
place
for
the
screws
to
pass.
Following
this,
a
large
square
was
cut
from
the
center
of
the
gasket
to
allow
a
space
for
the
cathode
or
anode.
Polypropylene
sheets
were
also
hand
cut
to
approximately
1.5
inch
by
1.5
inch
squares.
Fine
metal
mesh
was
cut
to
fit
inside
the
center
opening
of
the
silicon
gasket.
With
a
size
of
0.875
inches
by
0.875
inches,
each
metal
mesh
was
able
to
hold
35mg
of
active
material.
A
stainless
steel
spacer
was
added
between
the
steel
casing
and
the
cathode
to
ensure
full
contact.
This
will
be
unnecessary
when
there
is
more
than
one
layer
in
the
cathode.
Before
entering
the
glove
box,
the
stainless
steel
casing
was
hand
sanded
with
sandpaper
to
remove
any
slight
oxidation
layer
that
may
have
been
on
the
surface.
Additionally,
the
gasket
and
spacer
were
attached
to
the
steel
casing
using
an
adhesive.
This
was
done
in
order
to
hold
everything
together
and
align
the
screw
holes
to
make
assembly
in
the
glove
box
with
the
large,
bulky
gloves
easier.
However
during
initial
testing,
a
lower
than
anticipated
capacity
was
seen,
and
batteries
failed
to
perform
after
several
cycles.
It
is
thought
that
this
failure
occurred
because
of
the
diffusion
of
air
into
the
battery
via
the
screw
holes
or
a
less
than
airtight
seal
between
the
gaskets.
In
the
next
iteration,
silicon
vacuum
grease
and
parafilm
were
used
as
a
crude
way
to
try
to
slow
the
rate
of
diffusion
into
the
battery.
As
soon
as
the
battery
was
removed
from
the
glove
box,
the
silicon
vacuum
grease
was
applied
around
the
outside
of
the
outside
gasket
edge.
This
outside
edge
was
then
wrapped
in
parafilm.
Figure
5:
Expanded
drawing
of
conflat
design,
intended
to
show
layering.
Note
the
knife­edges
into
PTFE
create
an
airtight
seal.
As
a
result,
there
was
a
dramatic
increase
in
capacity
seen
during
the
first
cycling
to
107.7
mAh/g.
This
capacity
did
drop
off
significantly
in
further
cycling
that
took
place
hours
later
during
the
second
cycle
and
even
more
so
the
following
day
during
a
third
cycle.
Three
days
after
being
made,
the
battery
failed,
yielding
the
same
“exceeds
safety
limits”
errors
as
previous
batteries.
While
an
increase
in
performance
was
seen,
the
degradation
of
the
battery
indicated
that
air
was
still
able
to
leak
into
the
design
and
a
more
air
tight
design
was
needed.
Figure
6:
Fully
assembled
Conflat
cased
battery
with
wire
leads
coming
off
for
testing.
In
the
first
cycle,
the
battery
performed
with
a
capacity
of
134.6
mAh/g.
However,
in
subsequent
runs
the
capacity
drops
just
below
120
mAh/g
and
stays
relatively
consistent
in
subsequent
runs.
The
Solartron
crashed
in
the
middle
of
this
testing
and
the
abnormal
data
point
in
Figure
26
is
from
the
discharge
immediately
following
this
crash
and
thought
to
be
a
result
of
it.
Conflat
Battery
Casing
Another
type
of
battery
casing
was
designed
that
eliminated
the
original
prototype
casing
completely
for
a
conflat‐encased
battery
in
hopes
of
creating
a
more
airtight
seal.
This
design
maintained
the
same
cathode,
separator,
electrolyte,
separator,
anode
configuration,
but
instead
encased
battery
components
inside
of
a
conflat
container
where
a
knife‐edge
into
Teflon
creates
175
incorporated
into
a
Raven
UAS,
these
preliminary
results
are
encouraging.
3 CONCLUSIONS
There
is
a
definite
potential
to
scale
up
virally
constructed
batteries
to
a
size
that
could
power
small
electronics.
There
is
evidence
here
that
the
batteries
will
maintain
high
capacity
when
scaled
up,
though
work
is
still
needed
to
improve
the
airtight
seal
on
the
battery.
4 REFERENCES
Bibliography
1.
Whittingham,
M.S.,
Lithium
Batteries
and
Cathode
Materials.
Chemical
Reviews,
2004.
104(10):
p.
4271‐
4301.
It
is
important
to
point
out
that
all
testing
was
done
with
E3
bacteria,
which
has
strong
affinity
for
FePO4
and
does
not
attach
to
carbon
nanotubes
as
does
the
EC2
strain
described
in
the
2009
Science
paper
[8].
EC2
was
not
used
in
part
because
carbon
nanotubes
are
expensive
and
it
is
significantly
cheaper
to
create
a
proof
of
concept
using
a
version
of
the
battery
that
does
not
require
carbon
nanotubes.
Furthermore,
the
EC2
can
prove
difficult
to
grow
in
large
quantities,
and
two
attempts
to
grow
one‐liter
batches
both
failed.
2.
A.K.
Padhi,
K.S.N.,
J.B.
Goodenough,
Phospho­olivines
as
Positive­Electrode
Materials
for
Rechargable
Lithium
Batteries.
Journal
of
the
Electrochemical
Society,
1997.
144(4):
p.
1188‐1194.
3.
Nam,
K.T.,
et
al.,
Virus­Enabled
Synthesis
and
Assembly
of
Nanowires
for
Lithium
Ion
Battery
Electrodes.
Science,
2006.
312(5775):
p.
885‐888.
4.
Command,
A.F.S.O.,
Raven
Fact
Sheet,
in
http://www.avinc.com/downloads/USAF_Raven_FactShe
et.pdf,
U.A.
Force,
Editor.
2009:
Hurlburt
Field,
Fl.
Additionally,
other
lab
members
are
working
to
create
batteries
with
cathode
materials
that
have
substantially
higher
capacities
than
iron
phosphate,
but
that
are
all
constructed
in
the
same
manner
as
described
in
this
thesis.
If
this
technology
does
go
into
large‐scale
production,
it
will
certainly
be
with
a
cathode
with
higher
capacity
than
simple
iron
phosphate.
This
said,
all
of
the
designs
and
prototypes
described
here
can
be
fit
to
any
cathode
material.
This
said,
if
there
is
a
breakthrough
with
a
super
high
capacity
battery
material
in
the
lab,
this
work
should
parallel
expected
material
behavior
with
scale
up.
Switching
to
other
cathode
materials
being
tested
in
the
Belcher
lab
will
only
continue
to
increase
capacity
and
performance.
5.
John
Barry,
E.T.,
Up
in
the
Sky,
An
Unblinking
Eye,
in
Newsweek.
2008:
New
York,
NY.
6.
Army,
U.
Army­Technology:
RQ­11
Raven
Unmanned
Aircraft
System,
USA.
Industry
Projects
2009
[cited
2010
30
April].
7.
Gitlin,
S.,
AeroVironment
Receives
$37.9
Million
in
Orders
For
Digital
Raven
UAS,
Digital
Retrofit
Kits.
2010,
AeroVironment
Press
Release.
In
continued
work,
it
may
prove
worthwhile
to
look
into
comparing
different
metal
meshes
available.
The
stainless
steel
performs
well,
but
it
may
be
possible
to
obtain
a
metal
mesh
that
is
lighter
weight,
has
higher
electronic
conductivity,
or
a
lower
internal
resistance.
Additionally,
a
different
shape
of
hole
in
the
mesh
may
allow
more
active
material
to
be
packed
into
the
same
surface
area.
Nylon
screws
should
be
avoided
in
future
prototype
designs,
as
there
is
fear
that
the
polymer
stretches
with
time
and
may
cause
the
battery
to
loose
its
tight
seal.
Furthermore,
it
may
also
be
possible
to
work
with
a
different
type
of
metal
for
the
casing
design
that
is
lighter
weight,
such
as
aluminum.
The
current
stainless
steel
sheets
are
thick
and
heavy,
adding
significant
weight.
In
conclusion,
the
virally
constructed
FePO4
lithium
ion
battery
shows
promise
as
it
is
scaled
up.
It
performs
at
80%
capacity
and
shows
promise
of
more
effective
housing
leading
to
better
results.
While
more
research
is
undoubtedly
needed
before
this
battery
is
ready
to
be
8.
Lee,
Y.J.,
et
al.,
Fabricating
Genetically
Engineered
High­Power
Lithium­Ion
Batteries
Using
Multiple
Virus
Genes.
Science,
2009.
324(5930):
p.
1051‐1055.
Acknowledgements:
Dr.
Mordechai
Rothschild,
of
Lincoln
Laboratories,
if
the
mastermind
behind
setting
up
this
whole
project
between
Lincoln
Labs
and
MIT.
Without
him,
none
of
the
above
would
have
been
possible.
Dr.
Ted
Bloomstein,
of
Lincoln
Laboratory,
helped
significantly
in
the
conflat
casing
designs
and
the
work
could
not
have
been
done
without
his
innovative
ideas.
George
Middleton,
also
of
Lincoln
Laboratory,
contributed
significantly
to
the
machining
of
the
initial
prototype.
176