Volume 95 Issue 5 | p. 11 | News of The Week
Issue Date: January 30, 2017 | Web Date: January 24, 2017

Samsung: Flaws led to Note 7 fires

Independent auditors fault suppliers for defective batteries
Department: Business
Keywords: energy storage, batteries, electrolytes, battery separator
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Samsung says the cause of its battery failures was likely short circuits in the electrode assembly, which consists of layers of battery materials wound together.
Credit: Samsung
A diagram of the various layers of electrodes that go into a lithium-ion battery.
 
Samsung says the cause of its battery failures was likely short circuits in the electrode assembly, which consists of layers of battery materials wound together.
Credit: Samsung

Samsung’s investigation into the batteries of its Galaxy Note 7 phones has uncovered several manufacturing defects that likely contributed to the rash of phone fires customers experienced after the phone’s launch last year.

Billions of batteries are used every day without incident, but when batteries do catch fire, common causes include a short circuit across the battery separator, a porous polyethylene film which is supposed to prevent battery electrodes from touching. Batteries can also overcharge or experience a chemical breakdown of their flammable carbonate-based electrolytes.

At a press conference on Monday at its Seoul headquarters, Samsung disclosed results of analysis by two independent investigators: the testing firm Underwriters Laboratories (UL) and the engineering consulting firm Exponent. The firms tested batteries made by two batteries suppliers, dubbed in their presentations as “Company A” and Company B”. The suppliers are believed to be Samsung SDI and Amperex Technology.

UL performed a teardown analysis on damaged Note 7 phones and did a failure analysis on hundreds of pristine batteries. In a presentation, Sajeev Jesudas, president of UL’s consumer business unit, said the damaged Company A batteries showed signs of internal short circuits. In many of the undamaged batteries, UL noticed deformation in the upper right corners. The company says a likely failure mechanism is that the deformation, plus the mechanical stress of charging and discharging, probably damaged the separator, short-circuiting the battery.

For Company B, UL found missing insulation tape in some battery electrodes and welded spots that protruded into the battery structure.

Elaborating further, Kevin White, principal scientist at Exponent, suggested the damage to the Company A battery corners may have been caused by a pouch design that didn’t accommodate the volume of the electrode assembly, leading to short circuits across the separator. He also pointed to the sharp welds as a possible culprit in the Company B batteries.

Samsung says it is implementing new quality-control procedures for its batteries, including an eight-point safety check and has retained outside advisers to consult on battery design and safety.

K. M. Abraham, principal of the battery consulting firm E-KEM Sciences and a professor at Northeastern University, says that battery companies have been making the separator—critical to battery safety—thinner and thinner in order to increase the amount of electrode materials in the battery, thereby increasing energy storage capacity. “A thinner separator, together with a manufacturing flaw, is a calamity waiting to happen,” he says.

New separator chemistry, he adds, may make batteries safer. “Companies are moving to mechanically stronger and higher-temperature-performance separators made out of composites of polyethylene or other polymers and ceramics,” Abraham says. It is unlikely, he adds, that Samsung used these in the Note 7.

 
Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society
Comments
Steve Ross (Thu Jan 26 07:54:51 EST 2017)
This is very common battery technology, isn't it? Haven't other device suppliers experienced this problem?
sumner barenberg (Fri Jan 27 13:36:22 EST 2017)
We have also observed that the ultrastructure morphology of disc shaped batteries contain micro voids that allow for the diffusion of electrolytes which result in exothermic reactions. We have solved this problem by developing a cost effective materials solution that has been applied and can concurrently be applied to all forms of Li ion batteries. This solution will eliminate the potential for fire in case the battery begins to over heat.

Thank you

Sumner Barenberg, Ph.D.
Lee Etnyre (Sat Jan 28 15:00:35 EST 2017)
I suspected this from the moment I heard about the fires. Li Batteries are about the only thing that produce sufficient energy in any cell phone to cause a fire.
It was either a battery or a flaw in a charge control circuit. Rechargeable lithium batteries have a terrible history of fires in the aviation industry. Proper manufacturing QC is essential for these batteries. Whether new separator chemistry will help or not will depend on adequate testing before they are used. We cannot just assume that it will be done.

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