From Achilles to Zinc
By EV World
The decals on the side of the Toyota Prius parked out front of the Tampa Convention Center pretty much says it all:
- 30 % More Mileage
- Smaller, Lighter, Lower Cost
- Safe, Non-Toxic Batteries
Meet the world's first nickel zinc-powered hybrid.
Long a problematic battery chemistry with an excruciatingly short-life cycle due to dendrite formation that would short out the cell, nickel zinc may finally have come into its own. At least, that's the hope driving PowerGenix, the San Diego, CA-based company that is developing it as a potential replacement for toxic chemistries like nickel cadmium and expensive, rare earth-based nickel metal hydride.
EV World's publisher sat down during the PowerGenix's CEO, Dan Squiller during the Advanced Automotive Battery Conference in Tampa, Florida to talk about his company's batteries.
The first question we asked was how PowerGenix had been able to create a rechargeable zinc-based battery, which have been plagued for years by rapid cell failure.
Squiller (pronounced like "Stiller" but with "Sq" sound of "squirrel") explained that PowerGenix has carried on the original pioneering work of Palo Alto chemist Morris Eisenberg who over the years developed a set of additives to the electrolyte that "tricked the zinc electrode into thinking it was not immersed in potassium hydroxide."
"We've built on that original IP... with a more sophisticated version of the electrolyte. We've added ingredients into the negative electrodes.
"Basically, the Achilles heels of nickel zinc has always been dendrites, these little spears that form on zinc electrodes that plug-up and short out the separator and the positive and negative electrodes short. Through our electrolyte and negative electrode, dendrites don't form. So, that failure mode is taken out of the equation.
"The cycle life of our battery is equivalent to nickel metal hydride," Squiller stated.
However, it would appear there is still room for improvement according to the company's web site, which compares NiMH, NiCad and NiZn, listing its cycle life between 100-500 cycles compared to the other two chemistries at 100-800 cycles. Meanwhile, lithium ion battery makers are talking in terms of 2000 to 20,000 cycles.
PowerGenix NiZn battery pack staged on top of conventional Toyota Prius NiMH pack.
PowerGenix's chemistry may not be suitable at the moment for energy-hungry applications like battery electric cars and plug-in hybrids, but it does show promise in light electric vehicle applications from electric bicycles and scooters up to conventional hybrids like the Prius.
Squiller claims that while others have tried to solve the problem of dendrite formation, PowerGenix is the first to do so in a way that doesn't compromise the performance of the cell and that doesn't add cost to it, as well.
But the real story, which you'll learn more about when you listen to the complete 22-minute conversation recorded in the conference center, is that PowerGenix-based batteries can be assembled on the same manufacturing line as both NiCad and NiMH batteries today, which promises a huge cost savings.
"There is no special manufacturing equipment, no special processes. The only difference between us and a nickel metal hydride-type cell is that we have a zinc electrode, we have a special electrolyte, and everything else is kind of the same," Squiller noted.
To listen to the complete interview, use either of the two MP3 players at the top of the page, or feel free to download it to your computer for playback on your favorite MP3 device.
Below are the specifications for the PowerGenix NiZn battery as reported on the company web site.
Nominal Capacity (at c/5 rate)
Nominal Capacity (15 Amp Discharge)
|Nominal Voltage (1C/15 Amp Discharge)||1.6V|
|Specific Energy (15 Amp Discharge)||60Wh/kg|
|Volume Energy Density (15 Amp Discharge)||169Wh/L|
|Specific Power at 30 Amp Discharge||900W/kg|
|Internal Impedance (1,000Hz)||<4.5mOhm|
|Internal Resistance (DC)||7mOhm|
|Charge Time||1.5 hours
80% in 1 hour
|Charge Life at 15 Amp Discharge (100% depth of discharge)||200 cycles|
|Ambient Temperature Range Charge||+5°C to +40°C|
|Ambient Temperature Range Discharge||-20°C to +60°C|
|Ambient Temperature Range Storage||-30°C to +50°C|
|Outer Diameter||22.4mm. Max|
|Cell Height||45 mm. Max|