Hardly a day goes by without a news article about Lithium batteries exploding. This makes many people wonder if they are safe. The answer is more complicated because lithium batteries are complicated.
First, there are many different kinds of lithium batteries. The actual chemistry can change between batteries. For a review of lithium batteries, take a look to “Battery University”, and the different chemistries. Some “flavors” of Lithium battery are less likely to cause issues, even with poorer quality or abuse. It is all about the proper design and implementation. Here is a chart reprinted from Battery University of the Pros and Cons:
Reviewing those advantages and disadvantages, we have high capacity batteries that require special circuits to be safe. The lithium battery voltage requires the battery use an electrolyte other than water. Typically, organic solvents are used. If the cells break, they release flammable liquids. Finally, battery charging is different than a constant voltage systems typical of other batteries.
There are three sources of failure: 1) Poor quality cells. 2) Poor or missing battery management / protection circuits. 3) Poor quality charging system. ANY battery, lithium or not, will suffer from the same issues. The difference is the flammable solvent.
In many cases, it is a stack up of multiple issues. Knock off devices, like the look-a-like “Hoverboard” devices, have lower quality components and are almost never tested to US or international safety standards. Samsung tried squeezing a larger capacity battery, that one in one-hundred thousand didn’t fit quite right, causing failure when over charged.
So are they safe? When built by quality companies, used in quality equipment with quality chargers and tested, they usually are.