Developed by researchers at the University of Texas, Austin, the new membrane-free semi-liquid battery, consisting of a liquid ferrocene electrolyte, a liquid cathode and a solid lithium anode, exhibited encouraging early results, encompassing many of the features desired in a state-of-the-art energy storage device.
Findings of the study were published in a recent issue of the science journal Nano Letters.
“The greatest significance of our work is that we have designed a semi-liquid battery based on a new chemistry,” said lead author and Assistant Professor Guihua Yu. “The battery shows excellent rate capability that can be fully charged or discharged almost within one minute while maintaining good energy efficiency and reasonable energy density, representing a promising prototype liquid redox battery with both high energy density and power density for energy storage.”
Combining the best elements of lithium ion batteries – the most common power sources in consumer electronics – with supercapacitators (a relatively new type of battery valued for its capacity to discharge energy in large bursts) has been one of the focal point of much recent work on energy storage devices.
A successful technology of this type would not only make things significantly more powerful, but also much smaller and lighter, too, allowing them to be charged in mere minutes, rather than several hours, as is customary today.
The new battery’s high power density (1400 W/L) and good energy density (40 Wh/L) put it in the uniquely favorable position of combining a power density that is as high as that of current supercapacitors with an energy density on par with those of state-of-the-art redox flow batteries and lead-acid batteries, though slightly lower than that of lithium-ion batteries.
This combination is a real winner considering that the battery is designed mostly for use in hybrid electric vehicles and energy storage for renewable energy sources.
Yu and his team attribute the battery’s stellar performance in large part to its liquid electrode design. “The ions can move through the liquid battery very rapidly compared to in a solid battery, and the redox reactions in which the electrons are transferred between electrodes also occur at very high rates in this particular battery. For comparison, the values used to measure these rates (the diffusion coefficient and the reaction constant) are orders of magnitude greater in the new battery than in most conventional flow batteries,” explained Lisa Zyga, reporting on the discovery for Phys.org.
Before the new battery hits the shelves, researchers still have a lot of work ahead of them considering the lithium anode, which has to be made much safer than it currently is.
As long as the electrolyte compatibility is resolved, the team is also considering the use of other metals, such as zinc and magnesium that could serve as the anode in a battery of this type. “We also expect that other organometallic compounds with multi-valence-state metal centers (redox centers) may also function as the anode, which eventually would make the battery fully liquid.”