Why Do You Have To Charge A Battery More Frequently As It Ages?

In our increasingly technology-driven world, it seems like nothing can keep us from becoming the masters of the digital domain. From tablets and smartphones to electric cars, humanity is certainly advancing, but one stumbling block remains

We are heavily dependent on batteries to power our machines, and as we continue to move away from fossil fuels towards electric alternatives, the durability and longevity of batteries will come to the forefront of efficiency.

Photo Credit: Sashkin / Fotolia

Unfortunately, as any laptop or smartphone owner will tell you, batteries tend to lose their charge capacity over time, and within a few years, it seems like a battery can hardly hold a charge at all! If we want to keep pushing towards the future we’re promised, we need to answer that fundamental question – why do batteries lose their capacity?

Believe it or not, you should actually blame it on salt crystals, but we’ll get to that shortly….

The Science of Batteries

While batteries have certainly become more efficient and powerful in recent years, particularly the highly popular lithium-ion batteries (which we’ll focus on in this article), some of the old-school basics are the same. Specifically, modern batteries still possess positive and negative electrodes, as well as a chemical substance in between them – an electrolyte. Like all batteries, a chemical reaction is happening constantly to move ions between these positively and negatively charged poles, which produces a current.

In the case of modern lithium-ion batteries, the positive electrode is typically made of lithium iron phosphate, while the negative electrode consists of graphite. When you charge one of these batteries, the lithium ions from the positive electrode move to the negative electrode. That movement produces energy, which the battery can store. In the opposite direction, when the battery is discharging all of that energy, the ions move in the opposite direction.

This process consists of two parts – ions move in one direction and electrons move in the opposite direction. This differential provides the charging power for the battery, and if one of these two things stop moving, so does the other! In other words, once the positive electrode completely discharges, the battery stops powering a device. Similarly, if you switch off a device, the battery stops discharging!

The Battery Breakdown

Those very same ions that flow around the electrolyte mixture in a battery must pass through ion channels at the positive and negative electrodes. While the battery is discharging, those ions moving around the negative electrode change its physical properties at an atomic level. Lithium reacts with the iron phosphate and a crust begins to develop in those ion channels, developing on the small imperfections of the surface as a result of those tiny chemical reactions.

This crust is best compared to salt crystals, which slowly build up over time, similar to the way rust non-uniformly develops on certain types of metal as a result of oxidation. These salt crystals block the movement of ions through the channels, making the flow less efficient, and thus the capacity for holding a charge significantly lower. At the atomic level, there is no way to create an electrode that has absolutely no imperfections, so these crystals will always develop over time.

 

It may take a year or two for enough crystals to build up that a user will notice, but there’s no way to avoid it completely. Eventually, all batteries will undergo this process of degradation, frustrating us to no end. Some studies have sought out ways to reverse or remedy these problems, given that batteries are such a huge part of our daily lives, but the solutions are few and far between.

Atomic deposition of material to eliminate those imperfections (the sites on which crystals can form) could work, but it seems like a very time-intensive and meticulous process. As we learn more about these crystals, there might be a way to neutralize their build-up or break them apart, thus restoring a battery to its original capacity and strength.

However, lithium-ion battery repair strategies haven’t been perfected, so we’re forced to keep buying new ones or dealing with decreased capacity. The interesting thing is that increasing the capacity and longevity of batteries seems like the focus of every innovator in the field, but the problem of crystal formation might be a better area of focus. If that problem is solved, then the constant arms’ race of battery strength wouldn’t be nearly as important.

Fortunately, as we shift to a more “green” global society, batteries are only going to become more important, and if humans have proved anything throughout their history, it’s that “necessity is the mother of invention”!