In the market today the model Tesla S has the top distance range thanks to 18650 batteries by Panasonic. The battery pack has 85 kW and a bit of simple math tell us that it must contain about thousands of these little batteries, also employed for other applications like laptop batteries, cordless power tools, external USB battery packs for smartphones or tablets, flashlights and so on.
Panasonic also retains as of 2014 the lead for nominal capacity with its NCR18650C model with 3350 mAh with a weight of 47.5 grams, usually carrying a text that says “made in Japan” and a vivid green color.
However, they aren't particularly cheap even in packs of ten. The price of the Tesla S battery pack without adding an extra quantity as insurance for the Tesla S could be actually near $45,000 as some people comment in the forum, and if you consider that there are entire good looking cars for less than this there are who think there's a problem in the price optimization.
A curiosity is: the present price in the street of the NCR18650B battery is about $8 dollars each with luck. The Tesla S has approximately seven thousand of these in the highest capacity battery pack... so multiply it and you get $56,000. Subtracting the reseller price and the discount for large quantities this can lead toward much less as always so make your calculations!
The company has presented the promising project Gigafactory to effectively reduce the cost thanks to the production of 18650 batteries in massive quantities. They published an estimation of about >30% price reduction in 2017. Maybe the price must be much lower to seduce a broader number of users. At the same time, each single battery has two poles and a considerably tiny size in comparison. Thousands and thousands of connections, independent contacts and safety enclosures, with a cylindrical shape so there's also unused space between batteries.
The first optimizations at sight seem to reduce the number of contacts per unit of volume creating a larger rectangular battery with more voltage and a lighter security material for being packed in groups. This way the group can carry a unique safety enclosure reducing overall costs in principle and optimizing the space that the battery needs for the same amperage.
We also continue talking in any place about the necessity of multiple high voltage recharge channels in the same battery pack to achieve the convenient full recharge in mere minutes without the complexity of battery swap mechanisms. The described approach facilitates the creation of compartments in the same battery pack each one with its own recharge channel with high power capability.