Imprint Energy is aiming to disrupt the world of batteries with its next generation of printed zinc-based battery technology.
The company has dramatically increased the power delivery capability of the zinc cell by a factor of 10 at temperatures down to -35 ºC for a wide range of applications, from cold chain monitoring of vaccines to smart label in the Internet of Things (IoT).
The flexible batteries are produced with a printing process and can be 1mm thick to power IoT sensors and 5G cellular wireless nodes, Christine Ho, CEO of Imprint in California tells eeNews Power. The company is setting up a pilot line to produce the batteries and working with contract manufacturers on high volume production.
“The zinc battery that we have been commercializing is rechargeable and we have focussed on the electrolyte and the compatibility with the zinc electrode, rather than water based electrolytes in primary cells that are very hard to recharge,” she said.
“The leap from generation 1 to gen 2 was a major electrolyte change,” she said. “The zinc anode and MnO2 cathode are very similar and even the packaging and the current collectors are similar. The electrolyte came from a customer that wanted to push the power density for cellular with higher drain and making sure that ions can move really quickly. It’s a polymer electrolyte with additives.”
The first generation technology came from Ho’s PhD research at the University of California, Berkeley, for Bluetooth and LoRa LPWAN wireless systems that have a lower power requirement than cellular.
“With gen 2 we had more clarity on where to focus our development time,” said Ho. “We worked with a salt system that we thought would work well at low temperatures that suggested it would provide higher power at room temperature. We were able to make that in to a solid electrolyte and pattern that in our system. What we care about is that the battery is purpose built for smart labels,” she said. “If you cut the battery nothing oozes out or leaks out so it operates like a solid state battery. That also changes the manufacturing as we don’t have to back seal the units and we can process to over 100 ºC, and it starts to soften at 120 ºC.”
The low temperature operation down to -35 ºC is also key, an area where other battery chemistries such as lithium ion struggle. “At -35 ºC we have substantial run times and -30 ºC is a key number for frozen goods such as seafood and for vaccines,” she said. “We have customers that work with the Pfizer vaccine and we have been approached by customers to go to lower temperatures, it’s pretty unusual and we just haven’t tested it, our customers can test it themselves.”
Next: Flexible battery production for the IoT
The production process for the flexible battery for applications such as smart labels and IoT tags is key as these are proiduced in high volume.
“We are focused on high volume processing with screen and stencil printing as a sheet fed or roll to roll with layers tens of microns thick,” said Ho. “Once you are able to process with 100 percent yield then a roll to roll process makes a lot of sense and we work with EMS companies that assemble PCBs on various assembly methods. We have printed our battery alongside a piezo sensor and antenna and we have customers that want to combine process flows and take advantage of the integration.”
“One of our partners is a major label company and the 5G chips are small and thin enough to run the cellular chips through a roll to roll process as there’s enough flexibility in the flexible hybrids,” she said.
“A lot of our smart labels go about ballot boxes, food, vaccines and what we find is that flexing is still an advantage. We spent a lot of time on the flexing when we started but with the use cases we didn’t need to go to that extreme and its more about bending than flexing,” she said.
At the moment the flexible battery is not used in a solder reflow process, using mechanical connections such as eyelets or crimps.
“A lot of our customers aren’t using solder reflow as they also have flexible screens so we work with other interconnect methods. We haven’t tested it in reflow but my experience with reflow is that it is short so it should be survivable.
The company is building a pilot plant but also licenses the technology. “We are building a pilot line in Almeda and that will have a million unit capacity to understand the process and we do have multiple manufacturing partners and we have worked with partners in Europe,” said Ho. “Right now we are working with contract manufacturing as we validate scale but over time I anticipate our partners may want to take more ownership for their own customers.”
Ho says Imprint will retain the ownership of the inks and ink mixing. “The production is scalable and we have capacity in our pilot for production so we don’t plan to build the print manufacturing systems,” she said.
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