We’ve had phones catch fire, laptops melt and funky new skateboards explode in flames – but only with vaping does it seem to be that the battery powering the device is considered to be part of the ‘e-cig menace’. Person after other person fails to listen to advice or read the instruction booklet, then appears in a local media interview stating: “this is the last time I’ll be using my vape pen, I’m done with smoking these things”.
The problem with Lithium-ion cells is that they store a huge amount of energy compared to their size. Then, when a short circuit occurs or the temperature builds up, the cells grow internal dendrites that rupture the structural integrity resulting in thermal runaway. As the cell gets hotter more dendrites form, causing a further rise in temperature, the battery vents – and if the gases can’t escape fast enough then a device can explode. The problem isn’t one for the vape industry; it’s a problem besetting the lithium-ion battery industry.
Researchers have been looking at ways to get around this problem and looked to see what could be achieved using zinc. Zinc features as an electrode in standard batteries, but they can’t be recharged. These batteries use a water-based electrolyte to ferry charge around the cells whereas lithium-ion cells utilise an incendiary one.
Initial findings released earlier this year indicated that a phosphorous-based flame retardant could work with lithium-ion cells to extinguish the chances of a dangerous thermal runaway. Unfortunately this would also come at a cost to the user in the form of reduced power – which wouldn’t be useful to vapers.
Chemists at the US Naval Research Laboratory have been looking at constructing rechargeable batteries made from zinc and nickel. Pleasingly, initial results appear to indicate that zinc-based cells can store large amounts of energy and release it in ways similar to lithium-ion structures, and run through a hundred recharge cycles more safely.
The improved safety comes about from the lack of dendrite formation on the zinc electrode due to its sponge-like structure. The preparation of the zinc sponge electrodes includes being heated in a tube furnace under flowing Argon, and has cost implications at this stage. Lead researcher Deborah Rolison compared the sponge-like design to salad dressing because it is made up from a mix of oil and water: “At the end of the day, we have something you can hold in your hand, it’s free-standing, ready to go in the battery as the anode.”
To look at the feasibility of mass-producing cells using the safer zinc build, the team has licenced their tech design to EnZinc Inc., an independent start-up company in California that specialises in wearable tech and e-bikes.
EnZinc’s President Michael Burz said: “This breakthrough in rechargeable battery technology means that zinc has the potential to displace lithium because it is a safer, more affordable, and more readily available material. Large battery-powered electronics from electric vehicles to home energy storage will be able to be powered by cleaner, fully recyclable zinc-based batteries—and they’ll carry none of the fire risk of lithium-based batteries.”