PNNL

Researchers using PNNL’s tiny injectable tags to track fish can now depend on longer lasting micro-batteries to power those tags. The extended life is thanks to a new sealing method developed at PNNL.

PNNL initially released its micro, 3-volt lithium batteries in 2014. The batteries are slightly longer than a grain of rice and are used to power acoustic transmitter tags that are injected into young fish as part of PNNL’s Juvenile Salmon Acoustic Telemetry System, which monitors fish movement at hydroelectric dams and other water structures.

PNNL researchers initially installed the micro-batteries into fish tags immediately after making them by hand. But when demand grew, PNNL turned to an outside manufacturer, revealing a design flaw that affected the longevity of the batteries.

Scientists at PNNL determined the issue was due to the epoxy coating they used to seal their lab-made batteries. The epoxy didn’t fully contain the batteries’ volatile electrolyte. So, they went back to the drawing board and tested out more than ten different sealing methods, discovering the best-performing alternative method is a two-layered seal.

The first layer is made of neoprene rubber, which isn’t affected by volatile electrolytes. A so-called Torr seal, consisting of a gel containing ceramics and polymers, is then painted over the initial rubber layer and the end of the aluminum case. After curing, the gel becomes solid, completely encapsulates the battery and prevents electrolyte leakage.

Lab tests demonstrated the new dual-seal allows micro-batteries to work months after they are made - without having to immediately place the batteries into fish tags. The new sealing method is publicly available and can be used free of charge by any company wanting to manufacture micro-batteries. Companies interested in the new sealing method can contact PNNL’s Jason Zhang.

This work was jointly funded by DOE’s Wind and Water Power Technologies Office and the United States Army Corps of Engineers.

PNNL Research Team: Yuxing Wang, Samuel Cartmel, Qiuyan Li, Jie Xiao (now at University of Arkansas), Zhiqun “Daniel” Deng, and Ji-Guang “Jason” Zhang.