What happens to gadgets when you're done with them? Too often, they explode.

As we enter new gadget-buying season, spare a moment to meet the people who end up handling your old stuff. Isauro Flores-Hernandez, who takes apart used smartphones and tablets for a living, keeps thick gloves, metal tongs and a red fireproof bin by his desk at Cascade Asset Management, an electronics scrap processor in Madison, Wis. He uses them to whisk away devices with batteries that burst into flames when he opens them for recycling.

One corner of his desk is charred from an Apple iPhone that began smoking and then exploded after he opened it in 2016. Last year, his co-worker had to slide away an exploding iPad battery and evacuate the area while it burned itself out.

Around the world, garbage trucks and recycling centers are going up in flames. The root of the problem: volatile lithium-ion batteries sealed inside our favorite electronics from Apple, Samsung, Microsoft and more. They're not only dangerous but also difficult to take apart — making recycling e-waste less profitable and contributing to a growing recycling crisis.

These days, rechargeable lithium-ion batteries are in smartphones, tablets, laptops, earbuds, toys, power tools, scooters, hoverboards and e-cigarettes.

For all their benefits at making our devices slim, powerful and easy to recharge, lithium-ion batteries have some big costs. They contain cobalt, often mined in inhumane circumstances in places such as the Democratic Republic of Congo.