Darcy, Eric

NASA Technical Reports Server

Li-ion Pouch Cell Designs; 
Are They Ready for Space 
Applications? 
 
by 
Eric Darcy 
NASA-JSC 
 
For the 
Large Li-ion Battery Technology and 
Application Symposium 
of  the 
Advanced Automotive Battery Conference 
8 Feb 2012 
Orlando, FL 
https://ntrs.nasa.gov/search.jsp?R=20120000040 2019-08-30T18:37:01+00:00Z
Outline Li-ion Pouch Cells 
• Various Space Applications 
• Pouch cell design evaluation 
• Cell lot uniformity, why that’s important 
– Soft Short Screening 
• Performance at 4C Discharge Rates 
• Pouch Corrosion 
• Forward plans 
– Cycle life durability 
– Seals 
– Manufacturing quality 
• Conclusions 
Current EVA Batteries 
Rechargeable EVA Battery Assembly (REBA) 
Nickel Metal Hydride (NiMH) 
Pistol Grip Tool (PGT) Battery 
Nickel Metal Hydride (NiMH) 
Helmet Light (EHIP) Battery 
Nickel Metal Hydride (NiMH) 
Simplified Aid For EVA Rescue (SAFER) Battery 
Lithium Manganese Dioxide (Li-MnO2) 
Long Life Battery (LLB) for EMU 
Lithium ion (Li-ion) 
3 
Critical Manned Spacecraft Batteries 
• Spacesuit (Li-ion first flight in 2011) 
– 20V, 35Ah, 50 cycle, 5 yr life 
– Power all life support systems of the spacesuit 
• Robonaut (proposed) 
– 96V, 26Ah, few cycles, 5 yr life 
– Eventually operates side-by-side with 
spacewalkers 
• Orion Crew Exploration Vehicle (201?) 
– 120V, 30Ah, 3000 cycles, 3 yr life 
– 6-man capsule  
• International Space Station (Li-ion 
planned for 2017) 
– 120V, 120 Ah, 38,000 cycles, 6.5 yr life 
– Main power source during LEO eclipses 
• VASIMR (proposed) 
– 425V, 50 kWh discharged in 15 minutes 
– Main power for RF generator firings 
• Safety Requirements 
– Two-fault tolerant to most catastrophic 
hazards 
– Electrolyte leakage and cell internal shorts 
hazards controlled by a defined process that 
applies all reasonable mitigating measures 
Assessment of Cell Designs 
• All 4 are mature cell designs, made in 
high volume production lines 
• All 4 provide a blend of high power and 
energy density capability 
# Vendor P/N Mass 
(g) 
Rated 
Discharge 
Capacity (Ah) 
Standard Charge Regime Max 
Discharge 
1 A123 PHEV 480 20 3.6V at C/2 with C/50 
taper current limit 
80A to 2.0V 
2 Dow 
Kokam 
SLPB75106100 165 8 4.2V at C/2 with C/50 
taper current limit 
32A to 2.7V 
3 EIG C020 425 20 4.15V at C/2 with C/50 
taper current limit 
80A to 2.5V 
4 LG Chem P1 383 15 4.15V at C/2 with C/50 
taper current limit 
60A to 2.8V 
 
Test Plan for Assessment of Cell Designs 
• Acceptance Testing 
– Visual, OCV, AC Impedance, mass, dimensional 
– Pouch isolation resistance 
– Soft short (OCV bounce back after deep discharge) 
• Capacity performance 
– Capacity/Energy vs rate 
• at ambient T, C/5, C/2, C, 2C, 4C with 3 cells per design,  
• all charging at manufacturer recommended rate 
• Cycling performance 
– Capacity/Energy vs cycle number 
• 4C discharge, C/2 charge at ambient T for >100 cycles 
• Evaluate cell design and manufacturing quality 
– Seal leak rate and compare to 18650 crimp seal rates 
• Seal cells in Al laminate bag with dual element impulse heat sealer 
• Then thermally cycling (vs not) for 3 weeks 
• Sample gas trapped in outer bag 
• Measure trace concentrations of electrolyte components via GC/MS to 
calculate leak rate in volume/time 
– Compare leak rates per Wh, seal perimeter 
– Corrosion susceptibility 
– Destructive Physical Analysis (Tear down) 
EIG Cell Discharging at 80A 
4.0
3.8
3.6
3.4
3.2
3.0
2.8
2.6
V
o
lt
a
g
e
, 
V
798796794792790788786784
Elapse Time, min
-80
-60
-40
-20
0
C
u
rre
n
t, A
Cell Voltage, Current vs Time
EIG 20Ah Cell Design p/n C020
s/n 2385, 2386, 2387
4C (80A) discharge at RT
 Voltage 2385
 Current 2385
 Voltage 2386
 Current 2386
 Voltage 2387
 Current 2387
Comparisons of Demonstrated Performance 
• DK has highest specific energy (~160 Wh/kg) at 
the 4C-rate 
– However, also has highest temperature rise (28 C)  
• EIG has highest energy density (~319 Wh/L) at the 
4C-rate 
– 2nd  highest specific energy (~150 Wh/kg) 
Vendor PN
4C rate 
Energy
Average 
mass
Specific 
Energy Length Width Thickness Volume
Energy 
Density
Wh g Wh/kg mm mm mm L Wh/L
A123 PHEV 55.01 509.6 107.9 227 161 7.2 0.26314 209.1
DK SLPB75106100 26.34 165.0 159.6 102 106 7.8 0.08433 312.3
EIG C020 64.48 429.4 150.2 216 130 7.2 0.20218 318.9
LG P1 51.62 382.5 135.0 226 165 5.5 0.2051 251.7
4C specific energy and energy density comparison
Variations in as Received OCVs 
0.00% 
0.50% 
1.00% 
1.50% 
2.00% 
2.50% 
A B C D 
Sdev% 
Range% 
3s Range% 
Vendor 
A 
B 
C 
D 
Variations in as received Mass 
0.00% 
0.50% 
1.00% 
1.50% 
2.00% 
2.50% 
3.00% 
3.50% 
A B C 
Sdev% 
Range% 
3s Range% 
Vendor 
A 
B 
C 
Soft Short (Large Cell Design) 
3.025 
3.03 
3.035 
3.04 
3.045 
3.05 
3.055 
3.06 
0.00 5.00 10.00 15.00 
N2-596-Y-1 
N2-596-Y-2 
N2-596-Y-3 
N2-596-Y-4 
N2-596-Y-5 
N2-596-Y-6 
N2-596-Y-7 
N2-596-Y-8 
N2-596-Y-9 
N2-596-Y-10 
3.025 
3.03 
3.035 
3.04 
3.045 
3.05 
3.055 
3.06 
3.065 
3.07 
0.00 5.00 10.00 15.00 
N2-596-Y-11 
N2-596-Y-12 
N2-596-Y-13 
N2-596-Y-14 
N2-596-Y-15 
N2-596-Y-16 
N2-596-Y-17 
N2-596-Y-18 
N2-596-Y-19 
N2-596-Y-20 
V
o
l
t
s
,
 
V
 
V
o
l
t
s
,
 
V
 
Days Days 
4 cells out of 20 had declining OCV between days 10 and 14 
14-day OCV bounce back after deep discharge (constant voltage to 3.0V) 
Vendor A OCV Bounce Back 
3.0
2.9
2.8
2.7
O
C
V
, 
V
14121086420
Days
OCV recovery vs days after deep CV discharge at minimum 
operating voltage to a taper current limit of C/50, while at 23 degC.
Cells with declining OCVs have soft (high impedance) short
Vendor C OCV Bounce Back 
3.04
3.02
3.00
2.98
2.96
2.94
2.92
2.90
O
C
V
, 
V
2520151050
Days
OCV recovery vs days after deep CV discharge at minimum 
operating voltage to a taper current limit of C/50, while at 23 degC.
Cells with declining OCVs have soft (high impedance) short.
DPA Results of Failing Cells  
• Cells failing the OCV bounce back test were from lots 
made on consecutive days 
– Cells made on other dates passed all acceptance tests 
• OCV bounce back test after deep discharge (soft short 
test) was effective at non-destructively identifying cells 
with defects (in case of worst performing cell, defect was 
confirmed by DPA) 
– 2 large halos detected on one anode,  
• one with a crystalline piece of FOD consisting of Fe, Mg, Si, Al 
• And with a small piece of Al NOD 
SEM/EDS 
1 2 3 4 5 6 7 8 9 10
 
keV
0
10
20
30
40
50
60
70
80
90
 cps/eV
 C 
 O 
 F 
 Mg 
 Al 
 Si  P 
 S  K 
 Fe 
 Fe 
 Cu 
 Cu 
Crystalline FOD consists of Fe, Mg, Al, and Si 
SEM/EDS of NOD 
• Piece of Al debris on 
anode 
• Found near the 
bigger FOD 
1 2 3 4 5 6 7 8 9 10
 
keV
0
10
20
30
40
50
60
70
80
 cps/eV
 C 
 N 
 O 
 F 
 Al 
 Si 
 Cl 
 Cl 
 Ca 
 Ca 
 Cu  Cu 
 Zr 
 Zr 
 Zr 
 S 
 S 
 K 
 K 
 Na 
Pouch Corrosion 
• Procedure 
– Polarize Al layer of pouch 
to the negative potential 
of the cell 
– All four cell designs 
tested for up to 2 months 
• Results 
– Within 2 weeks, the 
pouch corrosion sites on 
Vendor D cell developed 
several wide, black 
blisters 
– The cell pouch no longer 
appeared tightly fitted 
around the cell electrode 
stack  
Pouch Corrosion (cont) 
• Vendor C Results 
– Within 4 weeks, the pouch 
corrosion sites on cell 
developed, one black and 
one small, gray blister, both 
on the corners  
– The cell pouch no longer 
appeared tightly fitted 
around the cell electrode 
stack  
• Results on the other 2 
designs 
– No evidence of pouch 
corrosion after 2 months 
• What cell design attributes 
do pouch corrosion resistant 
cells have that the others 
don’t? 
Other Examples of Pouch Corrosion 
• Defective inner isolation layer of 
the laminate pouch results in 
corrosion of the Al layer 
• Polarizing the Al layer to the (-) 
terminal is a quick test method 
Nylon layer 
Melt extrusion 
Corrosion site 
Butter-Cup Side 
Flat side 
Polyethylene layers 
Corrosion spots 
Cross section of corrosion spot 
Photo courtesy of NREL 
Conclusions To Date 
• Current Li-ion pouch cells designs for electric vehicle market are 
offering 
– Over 150 Wh/kg and 300 Wh/L at 15 minute (4C) discharge rates 
• Verified by test with 2 cell designs 
• Soft short test (or OCV bounce back test) is an excellent 
discriminator of manufacturing quality 
– Preventing battery assembly with cells with charge retention issues 
– Help precluding battery assembly with cells with latent defects 
• DPA’s are also an excellent way to assess manufacturing quality 
• Two cell designs were resistance to our pouch corrosion test 
• Planned testing will determine their readiness for the demands of 
crewed spacecraft 
– Manufacturing quality 
– Effectiveness of the seals 
– Durability of performance 


Li-Ion Pouch Cell Designs; Are They Ready for Space Applications?

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