Staying solidConventional lithium-air batteries draw in oxygen from the outside air to drive a chemical reaction with the battery’s lithium during the discharging cycle, and this oxygen is then released again to the atmosphere during the reverse reaction in the charging cycle. In the new variant, the same kind of electrochemical reactions take place between lithium and oxygen during charging and discharging, but they take place without ever letting the oxygen revert to a gaseous form. Instead, the oxygen stays inside the solid and transforms directly between its three redox states, while bound in the form of three different solid chemical compounds, Li2O, Li2O2, and LiO2, which are mixed together in the form of a glass. This reduces the voltage loss by a factor of five, from 1.2 volts to 0.24 volts, so only 8 percent of the electrical energy is turned to heat. This means faster charging for cars, as heat removal from the battery pack is less of a safety concern, as well as energy efficiency benefits.
The new battery is also inherently protected from overcharging, the team says, because the chemical reaction, in this case, is naturally self-limiting — when overcharged, the reaction shifts to a different form that prevents further activity.
In cycling tests, a lab version of the new battery was put through 120 charging-discharging cycles, and showed less than a 2 percent loss of capacity, indicating that such batteries could have a long useful lifetime. And because such batteries could be installed and operated just like conventional solid lithium-ion batteries, without any of the auxiliary components needed for a lithium-air battery, they could be easily adapted to existing installations or conventional battery pack designs for cars, electronics, or even grid-scale power storage.
source - http://www.nanowerk.com, MIT
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