My flashlight is powered by the 18650 battery.
I have been told that the Tesla is powered by the very same battery, but several hundred of them.
Not the same, but similar.
Tesla: thousands of cells
In contrast to every other automaker, which use specialized large format Li-Ion cells, Tesla’s battery pack is made up of thousands of inexpensive commodity cells similar to those found in laptops.
Unlike automotive cells, these cells are produced in the billions, subject to the fierce competitive pressures that are a signature characteristic of the computer and consumer electronics industries.
Even including the overhead of the pack enclosure, connections between cells in modules (and modules in the pack), sensors, and circuitry, Tesla likely has lower pack costs than any other maker of plug-in electric cars.
Simplifying a cheap cell
But for the Model S, Tesla redesigned what was already a relatively simple cell to be much less complex, and to have a much lower manufacturing cost—largely by removing expensive safety systems built into each individual cell.
When used as a laptop battery, each cells requires a safety mechanisms to prevent fires. But in a large, electronically-controlled, liquid-cooled battery pack like the one used in the Tesla Model S, having certain safety features on each cell would be redundant.
In this case, the company’s cell design eliminates the relatively complicated battery cap of the commercial cell, and replaces it with a simple aluminum disk.
Intumescent goo
Having radically simplified the cells, Tesla then designed simple and inexpensive fireproofing systems into its battery pack. Among many innovations, Tesla appears to have incorporated a form of intumescent goo that it sprays onto the interior of the pack to aid in fireproofing.
When exposed to heat, a chemical reaction occurs in the goo that helps cool the heat source, while simultaneously forming a fireproof barrier to protect the rest of the pack.