Typical lithium batteries being used right now to power the first generation of electric vehicles have limitations based upon their technologies in how far one can go on a daily basis. A number of promising start ups, such as PolyPlus, are trying to address this issue through the development of next generation EV battery technology.
PolyPlus is developing what are known as lithium-oxygen batteries that reportedly offer up to ten times the energy density of current battery technologies, meaning down the road electric cars might be able to go farther longer on one charge. To learn more about its technology, we recently interviewed the company.
EarthTechling (ET): What exactly does PolyPlus develop?
PolyPlus (PP): PolyPlus is developing lithium-oxygen batteries; oxygen can be scavenged from water or air, and thus we are developing both lithium-water and lithium-air batteries. These types of batteries are potential game-changers in their respective industries because they have unprecedented energy densities: from two to ten times the energy density of competing batteries.
ET: How do the batteries PolyPlus make differ from other types of lithium batteries?
PP: PolyPlus lithium-oxygen batteries use a fundamentally different chemistry based on a breakthrough discovery at PolyPlus, which led to the invention of water-stable lithium metal electrodes. We call these protected lithium electrodes or PLEs. The invention of the PLE enables the development of lithium-water and lithium-air batteries with unprecedented energy densities leading to vastly improved performance and safety.
There are two types of lithium batteries with which most people are familiar: lithium metal primary (single-use) batteries that go into wrist watches and cameras, and lithium-ion secondary (rechargeable) batteries that go into cell phones, laptops, and many other devices. Li-ion batteries are based on the use of lithiated carbon which is heavy compared to lithium metal, 375 milliamp hours per gram for LiC6 compared to 3785 milliamp hours per gram for lithium metal. So, using a lithium metal negative electrode rather than a lithiated carbon electrode represents a significant improvement in the weight of the battery.
Li-ion batteries also use relatively heavy positive electrode materials such as cobalt, nickel, and/or manganese oxides. Lithium-air and lithium-water batteries are effectively the Holy Grails of the battery field since the positive electrode is essentially weightless (you do not carry the air or water positive electrode in the cell, it is provided for “free” from the environment).