The lithium air battery has long been over hyped — now add a pot of gold to the end of that rainbow. Scientific American reports that scientists at the University of Saint Andrews in Scotland have been using gold to make a prototype of a lithium air battery that has high energy density and lasts for a long time.
In a typical lithium ion battery, lithium ions travel from the cathode to the anode when you charge it (through the electrolyte), and the anode holds onto the lithium ions to store the energy. When you use a battery, the lithium ions move from the anode to the cathode and a resulting chemical reaction leads to the harvesting of the electrons. The anode and cathode are called the electrodes.
The scientists at Saint Andrews have been using gold to make a porous electrode that they say can create a lithium air battery that maintains almost all of its ability to hold a charge after 100 charging cycles. The battery also has high energy density, or amount of energy that the battery can hold for its size.
The problem with the life of batteries is that after a certain amount of charges — when ions are removed, sent over to the anode and then inserted back into the cathode — the structure of the battery starts to degrade. The crystal structure that holds the ions actually starts to change, as an ion from one spot doesn’t necessarily come back to that spot but could instead be inserted into another spot. In addition, traditional lithium ion batteries have a slurry made from an active material like lithium cobalt oxide held together with a glue-like binder. If the binder fails, the coating can peel off the current collector, and if the metal corrodes, it can’t move electrons as efficiently.
Lithium air batteries use air as the cathode and lithium metal as the anode. The scientists at University of Saint Andrews say using gold for part of the electrode provides a more stable substrate for the reaction between the air and the lithium. Their gold electrode also has tiny holes all over it — nano-porous — that provides room for the ions from the solid lithium peroxide. The electrolyte is made of an organic solvent called dimethyl sulfoxide.
The more energy dense a battery is, the less volume and weight is needed. For electric cars it is particularly important to have a high energy dense battery because electric cars need to be as lightweight as possible (any extra weight just drains the battery faster), and batteries that are smaller and use less materials can also be lower in cost.
The scientists at Saint Andrews say more work needs to be done to figure out why the experimental battery is providing such a high level of capacity and density. But they’re excited about the battery because it could provide a longer lasting electric car battery that has a bigger range than what’s currently available. In an electric car, air that passes over the battery as the car drives, could be used for the cathode.
Clearly using lots of gold in a battery would be prohibitively expensive. One way to get around this would be to coat carbon with a gold plating. Other companies are working on the lithium air battery including IBM, and PolyPlus.