|Fig. 1: Tesla Model S at charging sStation. (Source: Wikimedia Commons)|
Within the last decade, electric vehicles (EV) have stormed the market in full force. At the front of the pack is Elon Musk and his company, Tesla Motors. While Tesla was founded in 2003, it was not until 2012 when Tesla announced its model S, did the dream of having a completely electric vehicle come to fruition (see Fig. 1). However, while the cars Consumer Reports perfect rating rave about the style and design, it is the battery that is the start of the show.
Lithium-ion batteries are abundant in todays day and age. They are used in Apple products, Tesla vehicles, power tools, etc. These batteries are primarily composed of the anode, cathode, electrolyte, and separator. The Lithium ions intercalate/de- intercalate, or are inserted/extracted, between the layers of the anode and cathode during discharge/charge, respectively. The lithium ions store the charge as they move as they move from the anode to the cathode when being used.  Li-ion batteries have become the technology of choice for many electronic devices because of the high energy density that the batteries contain. 
While Tesla broke out into the mass market with its Model S, it was the Roadster that started their company. The Roadster was one of the first consumer vehicles to offer an all electric option. The Li-ion battery could accelerate the car from 0 to 60 mph in about 4 seconds, while offering a range of over 200 miles. The battery can store approximately 53 kilowatt hours of electric energy and can deliver up to 200 kWs of electric power. The battery pack contains approximately 6800 small form factor battery cells. The cells are called 18650, are about the size of a AA battery, and power the entire vehicle. All in all, the Roadster's battery pack has a mass of about 450 kilograms. 
Each individual cell in the Roadster, and the rest of Teslas vehicle fleet, contain an internal positive temperature coefficient current limiting device. This protects the cells from short circuiting on an individual level.  They also have Current Interrupt Device which electronically disconnects the cell from the battery pack in the event there is a high amount of internal pressure. 
Tesla Motors now has the largest Li-ion battery manufacturing plant in the world. It has been named the Gigafactory and supplies low cost lithium ion battery packs and helps to facilitate the production of the more affordable Model S.  Tesla estimates that this factory can reduce the cost of producing Li-ion batteries by nearly 30%, and will help lead the way to not only an affordable electric vehicle, but also a more reliable electrical grid, reduced energy costs for businesses and residence, among other things. 
© Michael Boden. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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