Would you heat your earbuds’ lithium-ion batteries to over 300F / 150C to make ‘em charge like new? Research suggests there might be some benefit to doing so – but also, please don’t do it.
Why shouldn’t you take matters into your own hands and pop your flagging buds in the oven? Because while new research suggests that extreme heat could completely restore your tech’s onboard (and decidedly planet-unfriendly) lithium-ion batteries, it could also make them burst into flames in a state called thermal runaway.
Researchers at China’s Ningbo Institute of Materials Technology and Engineering have found a way to restore the energy density of old lithium-Ion batteries (LIBs), by heating them to over 300F / 150C.
I’m TechRadar’s audio editor; I test earbuds day in, day out, and every single set that crosses my palm has tiny and very-hard-to-recycle batteries stuffed into them. It’s hard to see this as sustainable in any way – so research breakthroughs like this one matter.
The heat’s on for a sustainable future
I’ve penned odes to Apple for researching removable batteries for iOS devices that might revive our expensive (and still not old) AirPods and iPhones, rather than seeing thousands of the things end up in landfill. But replaceable batteries have yet to arrive in Apple products – and I’m worried they never will.
I’ve since been disappointed in the Cupertino giant for seemingly changing its mission, suggesting that it’s focusing on iPhones that ‘never fail’ rather than being ‘super-easy to repair’ – spoiler alert: as sure as eggs is eggs, your portable tech’s batteries will fail after around three years, depending on usage.
Back to the team in China, which published a paper in Nature titled ‘Negative thermal expansion and oxygen-redox electrochemistry’. The missive explains how heating batteries to between 300 and 480F / 150 and 250C can cause them to shrink rather than expand (thermal expansion is an indicator that your battery has lost capacity – it’s even visible to the naked eye) thus reversing the capacity-reducing effects of past use.
As The Register also notes, rechargeable LIBs are of course a huge deal in 2025, powering everything from earbuds to smartphones, and Bluetooth speakers to electric cars. But all of these batteries (big or small, budget or flagship), lose capacity over time.
I’ve mentioned this before, but right now you cannot curtail your earbuds’ ultimate demise any more than you can reverse the sands of time. A layer of crystalline buildup will slowly coat the tiny LIB’s inside walls, the result being a reduction in the amount of charge said batteries can hold, even at 100% capacity. The moment you realize your phone no longer lasts the day on a full charge? That.
We didn’t start the fire…
There’s method to the (seeming) madness of this latest research; it’s not actually about becoming a fire-starter.
The team’s hypothesis is that the structural disorder developing inside LIBs may become a “tunable parameter” that, if tweaked using chargers at precise voltages to alter said battery composition, could be used to rejuvenate the batteries in our tech without fires.
And that’s good, firstly because batteries inside headphones and earbuds aren’t easy to replace, although Cambridge Audio says its Melomania P100 headphone batteries are replaceable, and Fairphone basically leads the charge here – if you care about more sustainable and eco-friendly brands, check that company out.
Secondly, in the run-up to Christmas last year, I’ve never seen such a bumper crop of audio tech being recalled due to its batteries overheating and becoming a fire hazard, from children’s Bluetooth speakers to inexpensive earbuds that ‘produce smoke’ and Belkin power banks; so, you know, the further we can keep intense heat away from our electronics, the better.
The researchers behind the paper don’t say how close their discovery is to commercial implementation, but the research does raise the possibility of fixable, revivable portable audio devices. Imagine if your phone’s battery needn’t even be replaced – because it could be revived.
Having seen the sheer volume of earbuds in production in 2025 (did you know that the manufacture of open earbuds is up 600%? Well, it is), this has the potential to be one of the biggest breakthroughs yet in the race for more sustainable tech.
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