Things look bad for Samsung right now. The company recalled the new Galaxy Note 7 last month because some of them were exploding. It sent out replacements. But now, their replacement phones, the ones they said were safe have exploded too. Now, the company has decided to halt production of the Galaxy note 7 entirely. The problem isn’t the phone, it’s the battery.

Most electronics use a lithium-ion battery. Lithium is used because it’s light, but can store a lot of energy. But because lithium can store a lot of energy, it’s in its nature to be unstable. We’ve already achieved almost 90 percent of the maximum battery life even possible from lithium-ion batteries. But that doesn’t stop people from wanting batteries that charge faster and last longer. This creates an “arms race” as manufacturers push the limits for really small gains. And the more you push the battery, the more likely it is to explode. We’re carrying around little bombs of energy and we’re pushing them too far.

Lithium ion batteries are actually pretty simple. There are two electrodes on opposite sides, this is just like a standard battery. One electrode is positively charged and called the cathode. The opposite electrode is called anode and its negatively charged. During charging, lithium ions move from one side to the other. When you use the battery, the lithium moves in the other direction. In between are these chemicals called electrolytes that help ions move more easily between the two sides. Electrolytes are crucial, but they’re also pretty volatile.

Lithium ions need to move from one side to the other. So, the ions have to go back and forth, but the anode and the cathode on the sides should never touch because they’ll redirect energy to the electrolytes in the middle. To keep this from happening, battery makers insert separators in between. In Samsung’s case, the original problem was that the separators were flawed and let the two electrodes touch. Then, all the energy being pumped into the battery goes directly to the electrolytes in the middle. It catches fire and explodes. 

There are other things that cause battery explosion. One way is overcharging. Overcharging happens when too much lithium goes into one side. Luckily, most batteries are designed to automatically prevent overcharging. Then there’s charging too much or too fast. This leads to something called “plating.” This forms needle-like structures called dendrites that can internally short out the battery. But this can be avoided by making sure the charger and the battery are compatible and supposed to be together.

Finally, sometimes companies try to make batteries store more power by increasing voltage, which is a way of measuring force. The higher the voltage, the more power there is. So they try to pump this up by adding elements like nickel to the lithium. But again, the higher the voltage is, the more likely the electrolytes are to combine in a way that makes them catch fire. 

Some scientists are trying to develop a kind of electrolyte that won’t burst into flames as easily. These electrolyte are called “ionic liquids” and need a lot more heat to form flammable gas. So it is a good idea, they are often much safer, but there can be challenges with battery life and they tend to be more expensive. So, lithium-ion batteries are the best we have for now. Honestly, they’re a good solution and they really do get the job done as long as we don’t demand more than they can safely offer.