The Safety level of Lithium Metal Coin Cells

9th -11th September 2014

1. Structure of the lithium metal coin cell 2. Test outline for external & internal short circuit

(UN T-5 & T-6) 3. The Safety level of Japanese coin cells (Already reported data) 4. The Safety level of coin cells collected worldwide

(A new report)

Coin (Button)：

Large electric current does not flow because of small electrode area.

1. Structure of the lithium metal coin cell

Gasket

Separator

Manganese dioxide

Lithium

Positive terminal

Negative terminal

2-1. Test outline of External short circuit (UN T-5)

■Test Condition ・Unused cell (Fresh) ・Atmosphere: 55±2℃ ・Circuit Resistance：<0.1Ω ■Requirements ・Temp. of cell : <170℃ ・No Explosion , No Rupture , No Fire

This test is based on UN Manual of Tests and Criteria 5th revised edition Amendment 1, PartⅢ subsection 38.3.

Thermostat Chamber

2-2. Test outline of Crush (UN T-6)

■Test Condition ・Unused cell (Fresh) ・Crush Speed:1.5cm/s ・Continue until either; -Pressure：13±0.78kN -Drop of Voltage :>100mV -Compressibility:>50% ■Requirements ・Temp. of cell : <170℃ ・No Explosion, No Fire

This test is based on UN Manual of Tests and Criteria 5th revised edition Amendment 1, PartⅢ subsection 38.3. This test simulates mechanical abuse from a crush that can result in an internal short circuit.

Test

UN-T5 External short circuit

UN-T6 Crush

55±2℃ 20±5℃

CR2032 made by Japanese

manufacturers

Results No Explosion No Fire

No Explosion No Fire

MAX Temp. 58～60℃ (+5℃ increase)

Less than 30 ℃ (+10℃ increase)

3. External ＆ Internal short circuit (Japanese cells)

As large electric current does not flow in a coin battery,

temperature does not increase in most cases, therefore

self-ignition does not happen.

13kN < 0.1Ω

CR2477 CR2450 CR2032 Amount of Li 0.29g 0.18g 0.06g

The number of models made by Japanese manufacturers 2 3 3

The number of models made by other countries’ manufacturers 5 19 28

Total 7 22 31

The most common CR type (Li/MnO2) lithium metal coin cells were collected worldwide to evaluate the safety level. These were purchased through the open market (shop, internet ,etc.) from around the world. CR2477 has the highest capacity, CR2032 is the most popular size.

4-1. Lithium Metal Coin Cells Collected Worldwide

Every cell was assigned a sample number according to the brand and manufacturer.

20

30

40

50

60

70

80

0 10 20 30 40 50 60

Tem

pera

ture

(deg

ree

C)

Time(min)

CR2477(Li 0.29g)_55℃

No.24

No.30

No.31

No.32

No.54

JPN-A

JPN-C

4-2. Test Results of External Short Circuit (Worldwide collected CR2477(Li 0.29g))

Temperature of every cell increased within 10℃ , and below 170℃. Neither explosion, rupture or fire were observed.

4-3. Test Results of External Short Circuit (Worldwide collected CR2477,CR2450,CR2032)

CR2477(Li 0.29g) CR2450(Li 0.18g) CR2032(Li0.06g)

at 55℃ (T-5)

Not evaluated

at RT

Temperature of every cell increased within 10℃ , and below 170℃. Neither explosion, rupture or fire were observed.

20

30

40

50

60

70

80

0 10 20 30 40 50 60

Tem

pera

ture

(deg

ree

C)

Time(min)

CR2450(Li 0.18g)_55℃ No.19No.21No.22No.23No.24No.25No.26No.27No.28No.29No.30No.31No.33No.34No.35No.52No.53No.54JPN-AJPN-B

20

30

40

50

60

70

80

0 10 20 30 40 50 60

Tem

pera

ture

(deg

ree

C)

Time(min)

CR2477(Li 0.29g)_55℃

No.24

No.30

No.31

No.32

No.54

JPN-A

JPN-C

20

30

40

50

60

70

80

0 10 20 30 40 50 60

Tem

pera

ture

(deg

ree

C)

Time(min)

CR2477(Li 0.29g)_RT

No.30

No.31

No.32

No.54

JPN-A

JPN-C

20

30

40

50

60

70

80

0 10 20 30 40 50 60

Tem

pera

ture

(deg

ree

C)

Time(min)

CR2450(Li 0.18g)_RT No.19No.21No.22No.23No.24No.25No.26No.27No.28No.29No.30No.31No.33No.34No.35No.52No.53No.54JPN-AJPN-C

20

30

40

50

60

70

80

0 10 20 30 40 50 60Te

mpe

ratu

re(d

egre

e C

)Time(min)

CR2032(Li 0.06)_RTNo.1No.2No.3No.4No.5No.6No.7No.8No.9No.10No.11No.13No.14No.15No.16No.17No.18No.19No.20No.21No.22No.23No.24No.33No.35No.51No.52No.53JPN-AJPN-B

4-4. Test Results of Crush (Worldwide collected CR2477(Li 0.29g))

Temperature of every cell increased within 10℃ , and below 170℃. Neither explosion or fire were observed.

15

20

25

30

35

-10 0 10 20 30 40 50 60

Tem

pera

ture

(°C

)

Time (min)

CR2477(Li 0.29g) _ Crush

No.24

No.30

No.31

No.32

No.54

JPN-A

Each cell was crushed to 13kN.

CR2450(Li 0.18g) CR2032(Li 0.06g)

4-5. Test Results of Crush (Worldwide collected CR2450,CR2032)

Temperature of every cell increased within 10℃ , and below 170℃. Neither explosion or fire were observed.

Each cell was crushed to 13kN.

15

20

25

30

35

-10 0 10 20 30 40 50 60

Tem

pera

ture

(℃)

Time(min.)

CR2032(Li 0.06g) _ Crush No.1No.2No.3No.4No.5No.6No.7No.8No.9No.10No.11No.13No.14No.15No.16No.17No.18No.19No.20No.21No.22No.23No.24No.33No.35No.51No.52No.53JPN-AJPN-B

15

20

25

30

35

-10 0 10 20 30 40 50 60

Tem

pera

ture

(℃)

Time(min.)

CR2450(Li 0.18g) _ Crush No19No21No22No23No24No25No26No27No28No29No30No31No33No34No35No52No53No54JPN-A

Conclusions

Lithium metal coin cells collected worldwide made by other countries' manufactures showed the same safety level as Japanese coin cells.

A lithium metal coin cell does not create high temperature by itself, and does not reach thermal runaway by itself.