New liquid alloy electrode improves sodium-beta battery performance
Sun, wind and other renewable energy sources could make up a larger portion of the electricity America consumes if better batteries could be built to store the intermittent energy for cloudy, windless days. Now a new material could allow more utilities to store large amounts of renewable energy and make the nation’s power system more reliable and resilient.
A paper published today in Nature Communications describes an electrode made of a liquid metal alloy that enables sodium-beta batteries to operate at significantly lower temperatures. The new electrode enables sodium-beta batteries to last longer, helps streamline their manufacturing process and reduces the risk of accidental fire.
“Running at lower temperatures can make a big difference for sodium-beta batteries and may enable batteries to store more renewable energy and strengthen the power grid,” said material scientist Xiaochuan Lu of the Department of Energy’s Pacific Northwest National Laboratory.
Need for energy storage, but challenges remain
More than 300 megawatts of large, cargo container-sized sodium-beta batteries are running in the United States, Japan and Europe, according to Dupont Energy Consulting. They often store electricity generated by rows of solar panels and wind turbines.
But their broader use has been limited because of their high operating temperature, which reaches up to 350 degrees Celsius, or more than three times the boiling point of water. Such high operating temperatures requires sodium-beta batteries to use more expensive materials and shortens their operating lifespans. PNNL researchers set out to reduce the battery’s operating temperature, knowing that could make the battery more efficient and last longer.
The traditional design of sodium-beta batteries consists of two electrodes separated by a solid membrane made of the ceramic material beta alumina. There are two main types of sodium-beta batteries, based on the materials used for the positive electrode: those that use sulfur are called sodium-sulfur batteries, while those that use nickel chloride are known as ZEBRA batteries. Electricity is generated when electrons flow between the battery's electrodes.
Lowering the battery’s operating temperature creates several other technical challenges. Key among them is getting the negative sodium electrode to fully coat, or “wet” the ceramic electrolyte. Molten sodium resists covering beta alumina’s surface when it’s below 400 degrees Celsius, causing sodium to curl up like a drop of oil in water, making the battery less efficient. For decades researchers have tried to overcome this by applying different coatings to the membrane.
New electrode offers different take
Lu and his PNNL colleagues took an entirely different approach to the wettability problem: modifying the negative electrode. Instead of using pure sodium, they experimented with sodium alloys, or sodium blended with other metals. The team determined a liquid sodium-cesium alloy spreads out well on the beta alumina membrane.
PNNL’s new electrode material enables the battery to operate at lower temperatures. Instead of the 350 degrees Celsius at which traditional sodium-beta batteries operate, a test battery with the new electrode worked well at 150 degrees – with a power capacity of 420 milliampere-hours per gram, matching the capacity of the traditional design.
Batteries with the new alloy electrode also retain more of their original energy storage capacity. After 100 charge and discharge cycles, a test battery with PNNL’s electrode maintained about 97 percent of its initial storage capacity, while a battery with the traditional, sodium-only electrode maintained 70 percent after 60 cycles.
A battery with a lower operating temperature can also use less expensive materials such as polymers -- which would melt at 350 degrees Celsius -- for its external casing instead of steel. Using less expensive and sensitive materials would also help streamline the battery’s manufacturing process. This offsets some of the increased cost associated with using cesium, which is more expensive than sodium.
The PNNL research team is now building a larger electrode to test with a larger battery to bring the technology closer to the scale needed to store renewable energy.
This research was supported by DOE’s Office of Electricity Delivery and Energy Reliability and internal PNNL funding.
REFERENCE: Xiaochuan Lu, Guosheng Li, Jin Y. Kim, Donghai Mei, John P. Lemmon, Vincent L. Sprenkle, Jun Liu, “Liquid Metal Electrode to Enable Ultra-Low Temperature Sodium0Beta Alumina Batteries for Renewable Energy Storage,” Nature Communications, DOI: 10.1038/ncomms5578, Aug. 1, 2014.
Interdisciplinary teams at Pacific Northwest National Laboratory address many of America's most pressing issues in energy, the environment and national security through advances in basic and applied science. Founded in 1965, PNNL employs 4,300 staff and has an annual budget of about $950 million. It is managed by Battelle for the U.S. Department of Energy’s Office of Science. As the single largest supporter of basic research in the physical sciences in the United States, the Office of Science is working to address some of the most pressing challenges of our time. For more information on PNNL, visit the PNNL News Center, or follow PNNL on Facebook, Google+, LinkedIn and Twitter.
Franny White | newswise
Standard BMI inadequate for tracking obesity during leukemia therapy
29.01.2016 | Children's Hospital Los Angeles
Lipoprotein nanoplatelets shed new light on biological molecules and cells
06.01.2016 | University of Illinois College of Engineering
Today, plants and microorganisms are heavily used for the production of medicinal products. The production of biopharmaceuticals in plants, also referred to as “Molecular Pharming”, represents a continuously growing field of plant biotechnology. Preferred host organisms include yeast and crop plants, such as maize and potato – plants with high demands. With the help of a special algal strain, the research team of Prof. Ralph Bock at the Max Planck Institute of Molecular Plant Physiology in Potsdam strives to develop a more efficient and resource-saving system for the production of medicines and vaccines. They tested its practicality by synthesizing a component of a potential AIDS vaccine.
The use of plants and microorganisms to produce pharmaceuticals is nothing new. In 1982, bacteria were genetically modified to produce human insulin, a drug...
Atomic clock experts from the Physikalisch-Technische Bundesanstalt (PTB) are the first research group in the world to have built an optical single-ion clock which attains an accuracy which had only been predicted theoretically so far. Their optical ytterbium clock achieved a relative systematic measurement uncertainty of 3 E-18. The results have been published in the current issue of the scientific journal "Physical Review Letters".
Atomic clock experts from the Physikalisch-Technische Bundesanstalt (PTB) are the first research group in the world to have built an optical single-ion clock...
The University of Würzburg has two new space projects in the pipeline which are concerned with the observation of planets and autonomous fault correction aboard satellites. The German Federal Ministry of Economic Affairs and Energy funds the projects with around 1.6 million euros.
Detecting tornadoes that sweep across Mars. Discovering meteors that fall to Earth. Investigating strange lightning that flashes from Earth's atmosphere into...
Physicists from Saarland University and the ESPCI in Paris have shown how liquids on solid surfaces can be made to slide over the surface a bit like a bobsleigh on ice. The key is to apply a coating at the boundary between the liquid and the surface that induces the liquid to slip. This results in an increase in the average flow velocity of the liquid and its throughput. This was demonstrated by studying the behaviour of droplets on surfaces with different coatings as they evolved into the equilibrium state. The results could prove useful in optimizing industrial processes, such as the extrusion of plastics.
The study has been published in the respected academic journal PNAS (Proceedings of the National Academy of Sciences of the United States of America).
Exceeding critical temperature limits in the Southern Ocean may cause the collapse of ice sheets and a sharp rise in sea levels
A future warming of the Southern Ocean caused by rising greenhouse gas concentrations in the atmosphere may severely disrupt the stability of the West...
09.02.2016 | Event News
02.02.2016 | Event News
26.01.2016 | Event News
11.02.2016 | Life Sciences
11.02.2016 | Physics and Astronomy
11.02.2016 | Earth Sciences