Nanowires could hold the key to safer, less flammable Lithium-ion batteries

Scientists have made Lithium-ion batteries both safer and more powerful with the use of nanowires

25 Apr 2018
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Rechargeable Lithium-ion batteries pretty much power our lives. From our smartphones to our laptops, right up to our electric cars, where would we be without them? Well, in all honesty, somewhere safer and a lot less flammable.

It’s unfortunately easy for Lithium-ion batteries to go up in flames, as evidenced by the numerous fires that the ubiquitous rechargeable battery has caused recently. Whether that’s a Tesla Model S going up in smoke, the recall of HP laptops or the famous Samsung Galaxy Note 7 fire debacle, Lithium-ion batteries are frankly, very flammable. 

However, according to a new study published in Nano Letters, a journal from the American Chemical Society, there could be a way to remove the fire risk from Lithium-ion batteries altogether, and the answer lies in nanowires.

Why are Lithium-ion batteries such firestarter’s?

Lithium is the least dense metallic element, which is why Lithium-ion batteries are so prevalent – they can fit in more power than other types of battery. The problem, though, is that lithium is also highly reactive, containing sodium and potassium. 

As with all batteries, Lithium-ion batteries have two electrodes separated by an electrolyte. Internally, there is an electrolyte solution of lithium salts and solvents, and there’s a finely-tuned balancing act between it and the electrodes. 

When the battery is charged, the Lithium ionic solution will flow from the electrolyte into the carbon anode, and flow back when discharged. Obviously, if this balance is thrown out, it’s the prime place for disaster to strike. If the elements come together, the battery can overheat and burst into flames. 

How could nanowires be used to prevent fires from occurring in Lithium-ion batteries?

Removing the fire hazard from Lithium-ion batteries has already proven possible in the lab, with the use of solid-state electrolytes. Unfortunately, solid-state electrolytes are notoriously difficult to scale up, and certainly not cheaply, so it’s not a feasible solution in the long-term. 

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Another potential option is polymer electrolytes, which are cheaper and much more scalable. Yet they aren’t very conductive and have hardly any mechanical properties. 

That’s why the team from the College of Chemical Engineering and Material Science of Zhejiang University of Technology wanted to see if making the solid-state polymer electrolyte more conductive would cut out the fire hazard that Lithium-ion batteries often provide.

By adding magnesium borate nanowires, which add good mechanical and conductivity properties to the polymer electrolyte, the team was able to observe hugely increased conductivity of the electrolytes without the fire-risk.

“Due to the high-strength and flame-retardant characteristics of the [magnesium borate] nanowire additive, both the mechanical properties and the flame-retardant performance of [solid-state electrolytes] were enhanced,” the researchers wrote in the report. “The results revealed the interaction between [magnesium borate] nanowires and –SO2- […] which could promote the release and transport of lithium ions, thus improving the ionic conductivity.”

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Testing the flammability of the electrolyte, the team found that it barely burned when the electrolyte which had been enhanced with the nanowire was partnered with the typical properties of batteries: a cathode and an anode. Better still, the battery even had better performance and higher cyclic capacity, making it an overall better Lithium-ion battery. 

Nanowires, which are often semi-conductive, are 60,000 times thinner than a fine human hair, making them perfect candidates for any work done on batteries.

The effectiveness of nanowires in batteries has been proven before. In a Stanford University study published in 2009, scientists were able to produce electrodes made of carbon-silicone nanowires. They observed that the nanowires were able to store ten times the charge of ordinary graphite electrodes in lithium-ion batteries. Even though that was in 2009, we haven’t seen nanowire-enhanced batteries come to market, so we can’t say if these hazardless Lithium-ion batteries will be with us anytime soon. In any case, at least we know there’s a feasible way to make the abundant battery less flammable.