Image: http://commons.wikimedia.org/wiki/File:Schematic_of_a_Li-ion_battery.jpg
Lithium-ion batteries offer a number of advantages for the renewable energy, electric vehicle, and grid-level storage markets: high energy density, no “memory effect,” low maintenance, and high current capacity. They do have a few disadvantages, not the least of which is that they are somewhat prone to “runaway thermal events.” (That’s the engineering euphemism for “catching on fire.”) Porous Power Technologies (PPT) has an improved battery design that promises to make battery fires a thing of the past.
The key resides in a new separator material. Li-ion batteries have a layer that separates the anode and cathode of the battery. The separator must be microporous to allow ions to transfer from one side to the other. Most Li-ion batteries employ a polyolefin separator, which works well for small batteries that go in cameras and laptop computers. But excessive heat can cause the material to shrink and short circuit the anode and cathode, causing the dreaded “runaway thermal event.” PPT uses an engineering grade polyvinylidene difluoride (PVDF) for its separator. The PVDF is more flexible than polyolefin, making it less prone to heat-related degradation. PPT also claims that the material is more porous, reducing the battery’s internal resistance, which in turn decreases the heat that it generates and improves its efficiency.
Image: Porous Power Technologies
The PVDF material is also fire-proof. It remains stable up to 160C, and then turns into a gel. Its flexibility also reduces degradation caused by repeated charging and discharging cycles, so the battery will have an increased life. And if that’s not enough, Li-ion batteries that use PVDF separators allow greater depth of discharge.
Better storage is the key to renewable energy and electric vehicles. A Li-ion battery that’s safer, more reliable, and longer lasting is just what the doctor ordered!