Yunasko says supercaps sweet spot is at 100ºC

Dr Natalia Stryzhakova, head of Yunasko's research labs: “We are happy to get a low-cost ultracapacitor system capable of reliably working at temperatures as high as 100-110°C.” Pic: Yunasko.

Dr Natalia Stryzhakova, head of Yunasko’s research labs: “We are happy to get a low-cost ultracapacitor system capable of reliably working at temperatures as high as 100-110°C.” Pic: Yunasko.

By Jason Deign

Ukrainian ultracapacitor hopeful Yunasko is looking to set up large-scale manufacturing in China after proving a product that works at up to 100ºC.

“Right now, our company is focused closely on customised solutions,” said project manager Sergii Tychina. “We have limited manufacturing capabilities here in Ukraine [but] we have partners in China.”

The news last month that Yunasko’s technology had passed independent high-temperature tests at JME, a US-based firm owned by ultracapacitor expert Dr John Miller, has sparked a search for strategic partners, Tychina said.

The tests showed Yunasko’s ultracapacitors could last 2,000 hours, or about a million charge-discharge cycles, at 100ºC with an operating voltage of 2.39V.

“This is the highest operating voltage of any solution-based ultracapacitor,” said Yunasko in press materials, “at a fraction of the cost typically seen for ionic liquids.” 

Performance and lifespan issues

Traditional ultracapacitors start to suffer performance and lifespan issues when operating above 65ºC, said Vadim Utkin, CEO.

Yunasko is hoping the tests will lead to interest from automotive manufacturers looking to incorporate ultracapacitors into cars without having to worry about placing the storage device far from the engine.

Integrating traditional ultracapacitors into vehicles has been a problem because the ultracapacitor efficiency drops at high temperatures such as those found near the engine.

Placing an ultracapacitor elsewhere, such as in the boot of the car, uses up valuable space and increases the amount of wiring needed, which bumps up the cost of the vehicle.

Although Yunasko was founded in 2010, its scientists have been working on ultracapacitor technology for more than 20 years, said Utkin. 

Carbon-carbon ultracapacitors

For most of this time the venture capital-financed company has focused on carbon-carbon ultracapacitors.

But for the last couple of years it has been experimenting with lithium-ion chemistries and claims to have hit on a couple of significant advances. The first was to do with energy density.

“We preserved the power density of the supercapacitor, 5kW per kilo,” Utkin explained, “but we managed to increase the energy density from roughly 5Wh per kilo to 40Wh per kilo.”

This still far off the 250 to 300Wh you would get with a lithium-ion battery, said Utkin, “but for many applications this energy density, combined with the high power density in one cell, is good enough.”

The second breakthrough was temperature. The previously leading technology for high-temperature ultracapacitors was based on ionic liquids, but these have high resistances at ambient temperatures and are costly to manufacture. 

High-temperature breakthrough

Utkin said Yunasko achieved its high-temperature breakthrough, using a different chemistry, around six months ago. “We see that we have probably two markets with this technology,” he told Energy Storage Report.

“The first is automotive; they need to put this in a compact space under the hood.”

Putting a Yunasko ultracapacitor in a car might not just save space in the boot, he said, but could also allow carmakers to move energy-giving lithium-ion batteries closer to the engine.

“We can make a thermal shield for the battery,” Utkin said, which will help auto manufacturers using towards 48V systems in cars.

A second market for the company is with hybrid buses in hot-climate countries such as India. 

Hot ambient temperatures

In these countries, said Utkin, the combination of charge-discharge cycles and hot ambient temperatures can raise engine temperatures to around 100ºC.

These temperatures force bus manufacturers to add cooling systems that all but wipe out the energy savings from hybridisation.

In conversations with an Indian company that wants to build rickshaws, said Tychina: “The most important requirement they had was the operating temperature.

“They start at 45ºC and can easily go above 65ºC, which is the maximum operating temperature for other ultracapacitors.”

The Chinese market for hybrid buses is “huge”, Tychina said. The country’s top bus maker, Yutong, sold 21,428 vehicles in 2016 and second-placed BYD shipped 14,903. There are around 18 other manufacturers in China alone.

India represents another major opportunity for Yunasko, but Tychina said the company’s technology could be used around the world. 

Not using ionic liquids

“We are not using ionic liquids so our price is lower [than ionic-liquid chemistries] and our performance at room temperature is the same practically as conventional capacitors,” noted Tychina.

With a decent-looking technology in the bag, Yunasko is now focused on getting its products to market. The company is hoping to find two tranches of up to USD$5m each to scale up its manufacturing capability.

Utkin confirmed: “Our problem is not technology, it’s sales channels. The strategy for Yunasko right now is to find somebody who might help collaborate on the final product, because they have market access.”

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