It is the obvious advantages operating characteristics of the lithium ion battery that is continuing to attract research and development of this technology. When you compare the specific energy of this type of cell which is typically 150 Wh/ kg and an energy density of 400Wh/L it becomes apparent why this has become the such a popular battery technology for everything from cell phones to electric vehicles. Long cycle life ( > 1000 cycles) and a broad operating temperature range ( charge at -20 to 60 deg C, and discharge at -40 to 65 deg C enable them to be applied to a wide range of applications. Single cells typically operate in the range of 2.5 to 4.2 volts which is approximately 3 times that of NiCd or NiMH cells. There are now a variety of manufacturers offering endless shapes and sizes.

The overall reversible chemical reaction is

LiMO2 + C = LixC + Li1-xMO2

At the positive electrode

C + xLi+ + xe- = LixC

At the negative electrode

LiMO2 + C = LixC + Li1-xMO2

A major disadvantage of Li-ion batteries is that they do not have a chemical mechanism to manage overcharge conditions which may result in thermal runaway conditions. This of course is the last thing you need with your hybrid or electric plug-in vehicle (or you cell phone for that mater.) In the recent past one major computer manufacturer recalled millions of Li-ion battery packs for their laptops because they may have a thermal runaway condition resulting in fire. This technology typically is accompanied by a management circuit or mechanical disconnect to provide protection from over-discharge, overcharge or over temperature conditions. Another perhaps less serious disadvantage is that these batteries tend to degrade when discharged below 2 volts and may vent when overcharged. Additionally Li-ion cells permanently lose capacity at elevated temperatures (65 deg C and above).

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