Researchers at Dalhousie University, funded by Tesla, have found a surprising reason behind the self-discharge of lithium-ion batteries even when not in use: the use of adhesive tape.
The coiled electrodes in the battery cells are held together with PET adhesive tape, which decomposes at high temperatures and forms dimethyl terephthalate (DMT). DMT acts as a redox molecule that reduces at the cathode of the battery, picking up an electron, and oxidizes at the anode, releasing the electron, resulting in battery discharge.
The researchers have discovered this through tests with NMC batteries and found that the electrolyte became increasingly discolored at higher temperatures. DMT is a component of the commonly used plastic PET, which was present in the studied battery cells only in the form of adhesive tape.
The solution to this problem is to replace the PET tape with a more stable material that does not decompose. The team is already in touch with battery manufacturers to inform them of this simple yet effective change.
Research Link: iopscience.iop.org, iopscience.iop.org
