Page 23

THE TECH of the heat generated. There is a micro-hammering effect on the surface of the separators because they repeatedly contact the electrodes. After a few hundred of these events, the surface of a rigid polyolefin separator will change. In other words, the porosity you start with is not the porosity you end up with because of the physical effects of the hammering. Because our material is very spongelike, it flexes with each of these charge and discharge events. It’s like a mattress. The surface porosity does not change very much even after 1000 cycles. Another of the more interesting aspects of our PVDF material is that we feel the battery separator of the future is going to have to operate in a higher voltage environment. 4.2 V is great for these smaller cells, but in order to improve EV batteries, you’re going to have to improve all the different components. For cells to work at high voltages - the 4.7 V, 4.9 V, 5 V range - you need electrolytes and electrodes that are specifically designed for those voltages, and a separator that is not going to oxidize. This

oxidation is a change in the polymer chemistry, initially on the surface, and eventually all the way through - kind of like rust. Polyolefin separators oxidize very quickly at high voltages. PVDF separators exhibit much less of a change over time. If you open up a battery with a Polyolefin separator that’s been cycled 100 times at high voltage, the separator is going to be discolored. The PVDF separator is going to look brand new - it’s very stable at high voltage. Charged: How does the cost of your products compare to those currently on the market? BP: We’re very cost-competitive with the high-end ceramic separators that are offered by the top-of-theline manufacturers. Our new ceramic-grade product comes out at the beginning of 2014, and it’s priced to be competitive. We’re still pre-revenue, but expect our first over-the-hump sales will be early next year.

Module and pack level testing CAN, I2C SMBus capable Drive cycle simulation Import drive cycle from table of values Battery power is recycled to AC grid in discharge Utilizes Maccor’s standard battery test software suite No system power limit, up to 900KW

CHARGED Electric Vehicles Magazine - Iss 11 DEC 2013  

CHARGED Electric Vehicles Magazine - Iss 11 DEC 2013