Elisa Zaleski M at 286G Final May 26 2010 Battery Basics A chemical reaction produces electrons Electrons travel from the to the electrode Ions travel through the electrolyte ID: 223557
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Slide1
Sodium Sulfur Batteries
Elisa
Zaleski
M
at
286G Final
May 26, 2010Slide2
Battery Basics
A chemical reaction produces electrons
Electrons travel from the (-
) to
the (+) electrode
Ions travel through the electrolyte
“Anode” = from the Greek for “way up”
Current flows through the anode into the device
Discharging? Negative electrode
Charging? Positive electrode
“Cathode” = from the Greek for “way down”
Current flows through the cathode out of the device
Discharging? Positive electrode
Charging? Negative electrodeSlide3
Current: Naming the Anode and Cathode
N
E
S
W
Current
Electrolytic Cell (Recharging)
Anode
(Positive
Electrode)
“Way Up”
Cathode
(Negative
Electrode)
“Way Down”
ElectrolyteSlide4
NaS: The Basics
Liquid
sodium and
liquid
sulfur as the negative and positive electrodes
Solid
ceramic as the Na
+ conducting electrolyte
β-alumina
NaSICON (Na Super Ionic CONductor
)Operating temperature ≅
300oC (to maintain the electrodes in the liquid
state)Potential Applications: Electric vehicles
Ford Ecostar 1991Energy storage
www.greencar.com/articles/ford-ecostar-ev.phpSlide5
NaS: The Basics
Key Features:
High-energy density (~367Wh/l) with a reduction in space required for the battery
EMF ~ 2V
No self-discharge
High cycle life
40,000+ cycles at 20% depth of discharge (DOD)
4,500 cycles to 90% DOD
2,500 cycles to 100% DODSodium and sulfur are relatively abundantSlide6
NaS: The Construction
Solid
electrolyte
separates the
sodium
inner core from the
sulfur
annulus
Protective Fe-75Cr coating is plasma sprayed on the inner wall to avoid corrosion
Configured in series and parallel
Image courtesy of NASA Glenn Research CenterSlide7
NaS: The Chemistry
Discharge
Na (negative electrode) sends electrons through the circuit
Na
+
pass through the electrolyte
Na
+ reacts with S to form sodium polysulfides at the positive electrode
2Na + xS
Na2
Sx
Charge
Sodium polysulfides decompose
Na+
passes back through the electrolyteSlide8
Discharge Cycle
Oshima, Kajita, and Okuno, Int. J. Appl. Ceram. Technol., 1 [3] 269-76 (2004)Slide9
Charge Cycle
Oshima, Kajita, and Okuno, Int. J. Appl. Ceram. Technol., 1 [3] 269-76 (2004)Slide10
Polysulfide versus Voltage
The polysulfide formed changes with state-of-charge
At ~Na
2
S
2
it is at full discharge
Oshima
,
Kajita
, and
Okuno, Int. J. Appl. Ceram. Technol., 1 [3] 269-76 (2004)Slide11
Transporting Na+
:
β
-alumina
Na
2
O(5-
11)
Al2O
3NaAl
11O
17Non-
stoichiometric compound of Na2O and Al
2O3 that includes
β and
β”β
” = Na2O(5-7)Al
2O
3
MgO added to increase the stability at the high sintering temperatures‘
Spinel’ layers separated by conduction planes
Oshima
,
Kajita
, and
Okuno
, Int. J. Appl. Ceram. Technol., 1 [3] 269-76 (2004)Slide12
Transporting Na+
:
NaSICON
Superior Na
+
conductivity compared to
β
-alumina
Na1+xSi
xZr
2P
3-xO
12 (0<x
<3)3D network of
ZrO6
octahedra sharing corners with
PO4 and
SiO4
tetrahedra
Na+ located in interstitial sites
Mainly monoclinic NASICON
Housecroft
and
Sharpe, Inorganic Chemistry, 3rd
Edition 2008Slide13
NaSICON vs
β
-
alumina
Housecroft
and
Sharpe,
Inorganic Chemistry, 3
rd
Edition 2008Slide14
NaS Batteries: Taking us off the grid?Slide15
Batteries: Storing energy
http://
www.npr.org/templates/story/story.php?storyId
=110997398Slide16
NaS Batteries: Taking us off the grid?
Ceramatec
is developing a low temperature (<100
o
C)
solid
NaS
battery using a
NaSICON
electrolyte designed for home energy storage
Prototype due out 2011
Potential Specs
20kWh
Daily charge/discharge cycles over 10 years
$2000 per
refrigerator sized unit
$100/kWh or <$0.03/kWh over the battery’s lifetime
Grid storage market expected to increase from $365 million today to ~$2.5 billion by 2015