University of Alberta chemists have taken a critical step toward creating a new generation of silicon-based lithium ion batteries with 10 times the charge capacity of current cells.
"We wanted to test how different sizes of silicon nanoparticles could affect fracturing inside these batteries," said Jillian Buriak, a U of A chemist and Canada Research Chair in Nanomaterials for Energy.
Silicon shows promise for building much higher-capacity batteries because it's abundant and can absorb much more lithium than the graphite used in current lithium ion batteries. The problem is that silicon is prone to fracturing and breaking after numerous charge-and-discharge cycles, because it expands and contracts as it absorbs and releases lithium ions.
Existing research shows that shaping silicon into nano-scale particles, wires or tubes helps prevent it from breaking. What Buriak, fellow U of A chemist Jonathan Veinot and their team wanted to know was what size these structures needed to be to maximize the benefits of silicon while minimizing the drawbacks.
The researchers examined silicon nanoparticles of four different sizes, evenly dispersed within highly conductive graphene aerogels, made of carbon with nanoscopic pores, to compensate for silicon's low conductivity. They found that the smallest particles—just three billionths of a metre in diameter—showed the best long-term stability after many charging and discharging cycles.
"As the particles get smaller, we found they are better able to manage the strain that occurs as the silicon 'breathes' upon alloying and dealloying with lithium, upon cycling," explained Buriak.
The research has potential applications in "anything that relies upon energy storage using a battery," said Veinot, who is the director of the ATUMS graduate student training program that partially supported the research.
"Imagine a car having the same size battery as a Tesla that could travel 10 times farther or you charge 10 times less frequently, or the battery is 10 times lighter."
Veinot said the next steps are to develop a faster, less expensive way to create silicon nanoparticles to make them more accessible for industry and technology developers.
The study, "Size and Surface Effects of Silicon Nanocrystals in Graphene Aerogel Composite Anodes for Lithium Ion Batteries," was published in Chemistry of Materials.
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More information:
Maryam Aghajamali et al. Size and Surface Effects of Silicon Nanocrystals in Graphene Aerogel Composite Anodes for Lithium Ion Batteries, Chemistry of Materials (2018). DOI: 10.1021/acs.chemmater.8b03198
Eikka
1 / 5 (1) Jan 15, 2019It won't be 10 times lighter, because batteries contain about 1/3 of the mass in supporting structure, shielding, cooling etc. From today's batteries, the best case scenario would reduce the mass of a Tesla size battery from 450 kg to about 100 kg with the same capacity.
TomSwift45
not rated yet Jan 15, 2019TomSwift45
not rated yet Jan 15, 2019Eikka
1 / 5 (1) Jan 17, 2019In today's electric cars, the batteries are insufficiently shielded from impact. A battery with 10 times the specific energy density is literally explosive, not merely violently combustible, so they need to be very carefully encased and isolated from impacts or other faults. The whole battery needs to be compartmentalized to limit the impact of any one cell failing, and that introduces more mass.
SURFIN85
2 / 5 (2) Jan 21, 2019Thorium Boy
1 / 5 (2) Jan 22, 2019Da Schneib
3 / 5 (2) Jan 22, 2019antialias_physorg
5 / 5 (1) Jan 22, 2019There's more to a car battery than merely the amount of charge you pack in there
- how stable is it against temperature changes?
- how stable is it against physical shocks?
- how quickly can you charge (discharge) it?
...and of course: how much does it cost to manufacture per kWh. Growing of nanotubes seems time intensive (and therefore costly in terms of mass manufacture). Against the roll-to-roll process currently employed that alone can easily offset the factor of 10 in terms of cost
That said: I'm holding out high hopes for the nano-silcon approach ...but at the moment I see this as a race between this and fluoride batteries as the next breakthrough that could actually hit the market.
antialias_physorg
5 / 5 (1) Jan 22, 2019What kind of longevity do you expect/need? Current EV batteries outlast the lifetime of the car. Easily.
https://www.engad...-longer/
E.g. Tesla car batteries are projected to last 800000km before they drop to 80% capacity (which is about the figure where you'd start looking for a new battery pack)
For comparison. The average lifetime of a car is mere 250000km (at which point they'll still have more than 90% capacity).
Also note that a battery with 80% capacity isn't worthless. You could use that as a home power buffer for your PV panels (a vastly oversized one, tho) or sell it at a good price to community grid buffer. Since the capacity loss flattens out a lot past the 90% mark those batteries could service the grid for 20 years or more afterwards.