We worry about battery life a lot these days, and while having to top up your phone at work might not deter you from using it, concern over an electric vehicle’s range certainly will. Batteries rule everything around us, which makes breakthroughs a big deal. A research team at Rice says they have produced a nice jump: By using a crushed silicon anode in a lithium-ion battery, they claim to have nearly tripled the energy density of current li-ion designs.
Engineer Sibani Lisa Biswal and research scientist Madhuri Thakur reported in Nature’s Scientific Reports (it has yet to be published online) that by taking porous silicon and crushing it, they were able to dramatically decrease the volume required for anode material. Silicon has long been looked at as an anode material because it holds up to ten times more lithium ions than graphite, which is most commonly used commercially.
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But it’s previously been difficult to create a silicon anode with enough surface area to cycle reliably. Silicon also expands when it’s lithiated, making it harder to produce a dense anode material. After previously testing a porous silicon “sponge,” the duo decided to try crushing the sponges to make them more compact.
“We previously reported on making porous silicon films,” Biswal said in a statement. “We have been looking to move away from the film geometry to something that can be easily transferred into the current battery manufacturing process. Madhuri crushed the porous silicon film to form porous silicon particulates, a powder that can be easily adopted by battery manufacturers.”
The result is a new battery design that holds a charge of 1,000 milliamp hours per gram through 600 tested charge cycles of two hours charging, two hours discharging. According to the team, current graphite anodes can only handle 350 mAh/g.
“The surface area of our material is 46 square meters per gram,” Biswal said. “Crushed silicon is 0.71 square meters per gram. So our particles have more than 50 times the surface area, which gives us a larger surface area for lithiation, with plenty of void space to accommodate expansion.”
The Rice team is currently prepping a test of a complete battery based on their design, and is looking at various options of silicon-friendly cathodes. Should the tech hold up at full scale, it could end up being a nice leap forward for battery tech. Producing the silicon material is theoretically pretty easy to scale up, although there’s no word on cost as of yet. (It does seem like it would require less-rigorous controls than, say, silicon wafers, though.) I’m still a bit skeptical of the claim that the cathode material can hold its charge capacity through 600 cycles — remember the kerfluffle over Apple’s claims that the iPhone battery would lose 20 percent capacity after 400 cycles way back when? — but if that’s the case, it’s the kind of resiliency electric cars need.
And really, that’s where this type of tech is headed. EVs have been hampered by battery technology for ages, and while next-gen tech like lithium-air has incredible potential, no one’s been able to crack the code just yet. And while an improved li-ion battery isn’t exactly a jump into Star Trek tech, a trebling (or even doubling) of battery density would be a big deal. How many people would be a 200-mile, rather than 100-mile, range Leaf? Or better yet, a Model S that can do 500 miles on a charge?
Until crushed silicon batteries go commercial, we all have reason to be skeptical, as battery breakthroughs are few and far between. And getting into the battery game isn’t exactly easy, as A123 System’s bankruptcy shows. But I won’t judge you if you start to dream about what’s possible with triple the battery capacity of what we’ve got now.
