Researchers at Stanford and the SLAC National Accelerator Laboratory have developed a lithium-ion battery electrode that can “heal”…
One of the major limitations in tech today is the storage capacity of batteries. Electric cars, solar generators, your cell phone – the performance of all of them is ultimately limited on how much charge a battery can hold. One of the most promising materials for use with lithium-ion batteries is just plain old silicon. Silicon is capable of holding a lot of energy while the battery is charging, lengthening its life.
Unfortunately, lithium-ion batteries with silicon electrodes don’t last very long – that’s because the process of charging them causes them to expand to be larger than their original size, then shrink down again as the electrons are released. Over time, cracks develop in the silicon and it eventually becomes so cracked that it can’t store electrons anymore.
That process led the research team to consider how things happen in nature. In biological organisms, cells suffer damage but are capable of healing themselves.
“The ability to repair damage spontaneously, which is termed self-healing, is an important survival feature in nature because it increases the lifetime of most living creatures,” the team wrote in their paper. “This feature is highly desirable for rechargeable batteries because the lifetime of high-capacity electrodes, such as silicon anodes, is shortened by mechanical fractures generated during the cycling process.”
To achieve the same kind of “healing” in a silicon electrode, the research team developed a polymer coating for the electrode that’s based on the same kinds of research being used to develop artificial “skin” for robots. The polymers have weaker bonds than ordinary polymers, so that they break when the silicon electrode expands. However, the broken bonds of the polymer attract each other. So as the silicon shrinks, the polymer re-forms and pulls it back into shape.
You can see the process here under an electron microscope in the photograph below. On the left, the silicon electrode has developed cracks. But just a few hours later, several of the cracks healed.
The team still has work to do. Using their self-healing polymer, the research team got the electrodes to survive through 100 charge-discharge cycles without losing its ability to store electricity. That’s promising, but still not close to their overall goal.
“That’s still quite a way from the goal of about 500 cycles for cell phones and 3,000 cycles for an electric vehicle,” researcher Yi Cui said in a press release, “but the promise is there, and from all our data it looks like it’s working.”
Image Credits: First image – (Brad Plummer/SLAC); Second image – (C. Wang et al, Nature Chemistry)
- Scientists Develop A Battery Electrode That Heals Itself (forbes.com)
- Scientists invent self-healing battery electrode (phys.org)
- Scientists invent self-healing battery electrode (sciencedaily.com)
- Tomorrow’s Rechargeable Batteries Might Never Wear Out (gizmodo.com)