Altair Nanotechnologies Inc., a leading provider of advanced nanomaterials and alternative energy solutions detailed why its NanoSafe™ rechargeable, nano titanate battery technology provides technical fundamentals preventing thermal runaway and fires inherent in existing, traditional lithium ion battery designs.

Future news releases will explain other features of Altairnano NanoSafe batteries that may prove advantageous in the power rechargeable battery market including long life, high speed recharge rates and high power capacity. The combination of these features has the potential to make Altairnano’s NanoSafe batteries ideal for power applications such as electric vehicles and hybrid electric vehicles.

How Does a Rechargeable Battery Work?
A battery consists of a positive electrode, a negative electrode, a porous separator that keeps the electrodes from touching and an ionic electrolyte, which is the conducting medium for ions (charged particles) between the positive and the negative electrodes. When the battery is being charged ions transfer from the positive to the negative electrodes via the electrolyte. On discharge these ions return to the positive electrode releasing energy in the process.

Existing Lithium Ion Batteries
Rechargeable lithium ion batteries currently use graphite for the negative electrode and typically lithium cobalt oxide for the positive electrode. The electrolyte is a lithium salt dissolved in an organic solvent which is flammable. When a lithium ion battery is first charged a protective layer (called the Solid Electrolyte Interface or SEI) is formed on the surface of the highly reactive negative electrode.

This SEI layer, under normal operating temperatures, maintains a safety barrier between the reactive negative electrode and the electrolyte. However, if the temperature of the battery rises above about 120°C the SEI breaks down. In this situation the negative electrode has a high tendency to chemically react vigorously with the electrolyte in a heat generating reaction that accelerates exponentially as the breakdown of the SEI occurs. This uncontrollable reaction is called a thermal runaway and ultimately leads to the destruction of the battery, and a resulting fire which could ignite the device to which the battery is connected such as an electric vehicle, laptop or cellphone.

The initial increase in temperature could be caused by a number of problems including external shorting of the battery, internal shorting of the electrodes resulting from mechanical damage to the battery or a manufacturing defect, overcharging of the battery, electronic control unit failure or external heat. Impurities in the battery could be introduced during the manufacturing process ultimately leading to an internal shorting of the battery.

The Altairnano NanoSafe^TM Battery
Using an innovative approach to rechargeable battery chemistry Altairnano uses a patented nano-titanate material as the negative electrode in its NanoSafe batteries. By making this novel change to traditional battery design it has achieved a high powered battery that is thermally stable, and therefore can not exhibit thermal runaway. By removing the highly reactive graphite from the battery design, and instead using nano-titanate materials as the negative electrode material no interaction takes place with the electrolyte in the Altairnano batteries. This results in an inherently safe battery.

This key feature of the Altairnano NanoSafe battery means that it is well suited for hostile environments where physical movement, corrosion, high and/or low temperature extremes, electrical circuit complexity could cause shorting or battery malfunction resulting in thermal runaway of traditional lithium ion batteries. Such environments can be found in electric vehicles and hybrid electric vehicles.

Altairnano is delivering its first NanoSafe battery in September to Phoenix Motorcars for incorporation into an electric sedan. Phoenix Motorcars, based in Ojai, California, is an early leader in the effort to mass produce full function, freeway ready electric automobiles.

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