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It is a phenomenon that has frustrated industry and users alike -- a laptop is fully charged yet loses some of its charge despite sitting idle and unused.

The issue -- known as self-discharge -- has puzzled manufacturers trying to determine why the charge in lithium-ion battery cells slowly diminishes over time.

Now, a researcher at Dalhousie University has identified a surprisingly common culprit that could address the problem.

Michael Metzger, an assistant professor and the Herzberg-Dahn chair and in the Department of Physics and Atmospheric Science, found that a tape used to hold the battery cell electrodes together decomposes, which creates a molecule that leads to the self-discharge.

Dr. Metzger and his colleagues exposed lithium-ion battery cells to different temperatures and were stunned to find that the electrolyte solution in the cell was bright red, something they had never seen before.

They discovered that the polyethylene terephthalate (PET) -- a resin used in everything from pop bottles to clothing -- in the tape decomposes and creates a molecule that shuttles back and forth between positive and negative electrodes. The problem is that the shuttle molecule does it all the time in the background and does not switch off, causing the self-discharge.

The researchers outlined their findings in two new papers and are catching the attention of manufacturers seeking ways to improve their batteries' performance.

Dr. Metzger is available to discuss the discovery and how it could lead to a fix that might involve replacing the PET tape with a more stable material that won't degrade.

Research papers: https://iopscience.iop.org/article/10.1149/1945-7111/acb10c; https://iopscience.iop.org/article/10.1149/1945-7111/acaf44

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Media contact:

Alison Auld
Senior Research Reporter
Communications, Marketing and Creative Services
Dalhousie University
Cell: 1-902-220-0491
Email: alison.auld@dal.ca