Engineering news
US researchers have developed a passive, gravity-fed liquid battery shaped similar to an hourglass could that they say offers cost and design advantages.
Liquid flow batteries, in which the positive and negative electrodes are each in liquid form and separated by a membrane, are not a new concept. Earlier prototypes of the hourglass battery also used complex systems of tanks, valves, and pumps, adding to the cost and providing multiple opportunities for possible leaks and failures.
The latest version substitutes a simple gravity feed for the pump system. The rate of energy production is adjusted by changing the angle of the device, speeding up or slowing down the rate of flow.
The two sides of the battery are composed of flowing liquid, while the other side, a sheet of lithium is in solid form. Particles flow through a narrow opening from one tank to another. The flow can then be reversed by turning the device over. In this case, the overall shape looks more like a rectangular window frame, with a narrow slot at the place where two sashes would meet in the middle.
Solid batteries and liquid batteries each have advantages, depending on their specific applications, said Kyocera professor of ceramics at MIT, Yet-Ming Chiang, but “the concept here shows that you don’t need to be confined by these two extremes. This is an example of hybrid devices that fall somewhere in the middle,” he said.
A conventional, all-solid battery requires electrical connectors for each of the cells that make up a large battery system. However, in the flow battery only the small region at the center — the “neck” of the hourglass — requires these contacts, greatly simplifying the mechanical assembly of the system, Chiang said. The components could be made through injection molding or even 3-D printing.
Venkat Viswanathan, a research scientist at Lawrence Berkeley National Laboratory, said the researchers had developed a promising new approach to battery storage: “They have been able to build a bridge between the usually disparate fields of fluid mechanics and electrochemistry,”
“Pumping represents a large part of the cost for flow batteries,” he added, “and this new pumpless design could truly inspire a class of passively driven flow batteries.”
Researchers expect the design to prompt new ideas that will ultimately lead to a real product.