Oct
20
A Battery’s Shape Matters A Lot
October 20, 2010 | 7 Comments
Researchers at the Department of Energy’s Pacific Northwest National Laboratory (PNNL) redesign of sodium-nickel chloride batteries (a molten salt battery very similar to Sodium-sulfur battery or NaS) promises to overcome some of the obstacles long associated with very large rechargeable batteries. Replacing their typical cylindrical shape with a flat disc design allows the battery to deliver 30% more power at lower temperatures. Close observation over experimentation can payoff well, 30% on a pretty good storage medium is a huge improvement.
Flat Disk Sodium Nickel Chloride Battery Design. Click image for more info.
The work was published in the October 8 issue of ECS Transactions, a trade journal.
The PNNL team said the ‘sodium-beta’ batteries could eventually be used in electricity substations to balance the generation and delivery of wind and solar power on to the grid.
Sodium-nickel chloride batteries are interesting because the battery’s main components include abundant materials such as alumina, sodium chloride and nickel, they are less expensive to manufacture than lithium-ion batteries, and could still offer the performance necessary to compete for the consumers’ interest. This type of battery has a high energy density, high efficiency of charge/discharge (89–92%) and long cycle life. In addition, compared to other battery systems, sodium-beta batteries are safer and can help incorporate renewable energy sources into the electrical system easier.
Carl Imhoff, electricity infrastructure sector manager at PNNL said, “This planar sodium battery technology shows potential as an option for integrating more solar and wind power into our electric grid.” Perhaps at large battery manufacturing volume the productivity of solar and wind can get more cost competitive.
The history of sodium beta is short. Sodium-beta alumina batteries have been around since the 1960s but their tubular, cylindrical shape does not allow efficient discharge of stored electrochemical energy. This inefficiency causes technical issues associated with operating at high temperatures and raises concern about the cost-effectiveness of the tubular batteries.
Lithium-ion batteries surpassed sodium-beta batteries because they perform better. However, materials for lithium batteries are limited, making them more expensive to produce. Safety also has been a concern for rechargeable lithium batteries because they can be prone to thermal runaway, a condition where the battery continually heats up until it catches fire.
PNNL Scientist Xiaochuan Lu, co-author of the paper said, “The PNNL planar battery’s flat and thin design has many advantages over traditional, tubular sodium nickel chloride batteries.”
To take advantage of inexpensive materials, the PNNL researchers thought a redesign of the sodium-beta batteries might overcome the technical and cost issues: the cylindrical sodium beta batteries contain a thick, solid electrolyte and cathode that creates considerable resistance when the sodium ion travels back and forth between the anode and the cathode while the battery is in use. This resistance reduces the amount of power produced. To lower the resistance, temperature must be elevated. But increasing operation temperature will shorten the battery’s lifespan.
The researchers then tested the performance of their redesigned sodium-nickel chloride planar batteries, which look like wafers or large buttons.
The researchers found that a planar design allows for a thinner cathode and a larger surface area for a given cell volume. Because the ions can flow in a larger area and shorter pathway, they experience lower resistance. Next, the battery’s design incorporates a thin layer of solid electrolytes, which also lowers the resistance. Because of the decrease of resistance, the battery can afford to be operated at a lower temperature while maintaining a power output 30% more than a similar-sized battery with a cylindrical design.
Another attribute is the battery’s flat components can easily be stacked in a way that produces a much more compact battery, making it an attractive option for large-scale energy storage, such as on the electrical grid.
Lu continues, “Our goal is to get a safer, more affordable battery into the market for energy storage. This development in battery technology gets us one step closer.”
Working with Lu on the project are Greg Coffey, Kerry Meinhardt, Vincent Sprenkle, Zhenguo Yang, and John P. Lemmon.
Its not likely that sodium beta is going into your laptop or EV. They run hot and are costly to build and pose some performance and safety issues. But at scale the new design could dramatically impact these concerns, which might open a much bigger market for large installations. Getting the heat down is crucial for lifetime and operating costs.
Something needs done that’s economical for getting wind and solar more competitive with the conventional fueled generation. Batteries seem expensive, but big breakthroughs can change that and if or when the economics get to scale the renewable sources could have a very satisfying effect on power production and consumer expenses.
There are a few NaS grid battery sets installed now, and the new work could prove very beneficial for utilities and their customers.
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very good post..
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