Why Do Rechargeable Batteries Go Bad? Mystery Solved!

batteriesAccording to the latest research by the U.S. Department of Energy, the scientists finally figured out why do rechargeable batteries go bad. They successfully solved the mystery, as they now know exactly why this happens and more importantly, how to stop it from happening.

When Lithium-ion battery discharges, the lithium ions carry an electrical charge from the anode to the cathode across a non-aqueous electrolyte and this is what powers the phone. However, it is not a completely repeatable system, because each time that the lithium ions move through the battery, they cause minute changes to the electrodes’ physical structures. And this is why batteries eventually lose on their efficiency. The fact is, that every time people recharge their lithium-ion batteries, their storage capacity decreases just a little bit and this is the reason why people’s mobile gadgets do not stay on as long as they did a year ago.

There are two studies, which were recently published in the Nature Communications journal. One study is from the team at national DoE labs, including Brookhaven, Lawrence Berkeley and SLAC. The other one is from the National Renewable Energy Laboratory. Both studies have looked intensely into this process and they both came up with some surprising discoveries.

Huolin Xin, who is a materials scientist at Brookhaven Lab’s Center for Functional Nanomaterials (CFN), said that they discovered surprising and never before seen evolution. They also came across the degradation patterns in two key battery materials. Xin, who is also a co-author on both studies, said that contrary to large scale observation, the lithium-ion reactions in fact erode the materials unequally, seizing upon intrinsic vulnerabilities in atomic structure in the same way that rust creeps unequally across steel. Batteries are eventually going bad as a result of minute brakes in the materials, which are caused by the movement of lithium ions through the nickel-oxide anode.

Xin said that as the lithium ions travel through the reaction layers, they cause clustering crystallization, which builds up over time and begins limiting performance. The scientists discovered that these structures have a tendency to make a formation along the lithium-ion reaction channels, which they directly observed under the Transmission Electron Microscope (TEM). According to Xin, the effect was even more pronounced at higher voltages, which explains the more rapid deterioration.

Now that the scientists know how and why are these batteries slowly breaking down over the course of their operational lives, the developers should be able to use this data for creating new and more robust battery designs. And hopefully, they will soon create a battery that will last longer.

According to Xin, it could be possible to use atomic deposition to coat the Nickel Manganese Cobalt (NMC) cathodes with elements that are able to resist crystallization and to create nano-scale boundaries within the micron-sized powders, which are needed at the cutting-edge of the industry. Xin revealed that Berkeley Lab battery experts Feng Lin and Marca Doeff are working on that right now and only time will tell how successful they are.

By: Janette Verdnik

Science Codex
Brookhaven National Laboratory

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