Safety of small li-ion rechargeable batteries

5. Safety of small li-ion rechargeable batteries
5-1 Safety settings of small li-ion rechargeable batteries
Lithium titanate is used as the active material in theanodes of small li-ion rechargeable batteries. Selectionof a highly safe active material as the anode results inexcellent safety. For this reason, the SLB exhibits a highdegree of safety and has passed a variety of safety
tests, including external short-circuit, overcharge, forced
discharge, and nail penetration tests.

5-2 Safety testing of small li-ion rechargeable batteries
Table 5-1 indicates the safety tests small li-ion
rechargeable batteries have passed.

Table 5-1. Safety test categories for small li-ion rechargeable batteries
No. Test parameter Reference standard

12

Test details

Judgment
criteria

Proof of safety

Does notexplode or
burst into flame

No explosion
or flames

Crushing

JIS C 8712

After charging fully, a semicircularindenter (10mm) is used to indenta cylindrical battery’s vertical axis,
crushing it to 50% of its height before
the test.

Nailpenetration

Safety assessment
standards andguidelines of theBattery Associationof Japan

After fully charging, a nail of φ3.0mm is
inserted vertically into the center of thebattery at a speed of 5.5mm/s, piercing
through the battery.

Does notexplode or
burst into flame

No explosion
or flames

UL

Pressure is applied to a blunt nailapproaching fully charged battery ata speed of 0.1mm/s. A short circuit isdeemed to occur if battery voltage drops
by 0.5V or more, and the lowering of thenail is halted.

Does notexplode or
burst into flame

No explosion
or flames

JIS C 8712

A battery’s cathode and anode areconnected to an external resistance ofapproximately 1mΩ, causing a shortcircuit.

Does notexplode or
burst into flame

No explosion
or flames

Does notexplode or
burst into flame

No explosion
or flames

Does notexplode or
burst into flame

No explosion
or flames

3

Blunt nail test

4

Exterior
short circuit

5

Overcharge

JIS C 8712

Using a battery that can be used at 10Vor more, charge from a discharged state
at 1C (or 2–10C) to 250% of the battery’s
rated capacity.

6Forceddischarge

JIS C 8712

Conduct a reverse charge of a battery
from its discharged state (SOC of 0%) for
90 minutes at 1C.

Small Li-Ion Rechargeable Batteries Technical Notes CAT. 8601

Safety of small li-ion rechargeable batteries
Crush test

Nail penetration test

Figure 5-1. Safety test examples(left: crush test; right: nail penetration test)

Table 5-2 indicates the safety tests with therecommended United Nations tests for goods to betransported (UN38.3). The SLB has passed all of thesetests, indicating it can be shipped overseas.

Table 5-2. Details of implemented UN standards and results.

Test parameter

Requirements

ResultT1

High-speed simulation

No leaks, valve operation, rupturing, cleavage or fires and, except forbatteries that are fully discharged, the open circuit voltage is 90% ormore than the level just before the test.

Pass

T2

Temperature test

No leaks, valve operation, rupturing, cleavage or fires and, except forbatteries that are fully discharged, the open circuit voltage is 90% ormore than the level just before the test.

PassT3Vibration

No leaks, valve operation, rupturing, cleavage or fires during or after
the test and, except for batteries that are fully discharged, the averagevoltage is 90% or more than the level just before the test.

Pass

T4Impact

No leaks, valve operation, rupturing, cleavage or fires and, except forbatteries that are fully discharged, the open circuit voltage is 90% ormore than the level just before the test.

Pass

T5

External shortening

External temperature does not exceed 170°C, and no rupture, cleavage
or fire occurs during testing or within six (6) hours afterward.

Pass

T6

Crushing

External temperature does not exceed 170°C, and no rupture, cleavage
or fire occurs during testing or within six (6) hours afterward.

Pass

T7Overcharge

Does not apply, as for secondary batteries only

—T8

Forced discharge

No bursting or fires occur during testing or within seven days afterward.

Pass

Small Li-Ion Rechargeable Batteries Technical Notes CAT. 8601