I like the way this guy approached the problem and I think his result is a good one.
It has a bit of the “sustainable preachy” in it, but he is lecturing on a collage campus. His general approach to problems is one I agree with, especially his points about NOT getting the experts to tell you what won’t work before you even start…
Then the battery is incredibly basic. Two liquid metals separated by a liquid salt, in contact with solid electrodes. He claims it ends up in a very good price point (and I think it ought to as it will scale very well and the materials are cheap) but I have no idea if that’s good enough.
Toward the end he tosses some well deserved barbs at the California System Operator who put out a graph saying they were looking for “storage” that would work over season and annual cycles. As he points out, who in their right mind would buy a battery and sink that capital cost to use it once a year?
He claims pumped hydro is 70% efficient and this battery is 80%. That still means you lose 20% of the electricity you store, but some times that might be worth it. One hour 4 minutes:
Here’s the M.I.T. web page about the batteries:
Liquid Metal Batteries
The liquid metal battery (LMB) project seeks to develop a low cost and long lifespan battery for grid-scale stationary energy storage. The battery utilizes three liquid layers as the electroactive components, including a liquid metal positive electrode, a fused salt electrolyte, and a liquid metal negative electrode. The three liquid layers float on top of one another due on their density differences and immiscibility, promising low assembly cost with use of inexpensive materials. Furthermore, liquid electrodes avoid common failure mechanisms of solid-state battery components, potentially enabling a long lifespan device. Current research efforts encompass a wide range of scientific topics and engineering challenges, including fundamental thermodynamic measurements of candidate electrode couples, computational thermal modeling, electrochemical studies of molten salt electrolytes, long term corrosion and lifespan testing, testing and characterization of complete single-cell batteries, and scaling up the design to build larger single-cells.
And their news release / story:
Looks like you could DIY on a lab scale. Note these things run very very hot so needs a refractive case in a fireproof place ;-)
Choice of materials
For Sadoway and then-graduate student David Bradwell MEng ’06, PhD ’11, the challenge was to choose the best materials for the new battery, particularly for its electrodes. Methods exist for predicting how solid metals will behave under defined conditions. But those methods “were of no value to us because we wanted to model the liquid state,” says Sadoway — and nobody else was working in this area. So he had to draw on what he calls “informed intuition,” based on his experience working in electrometallurgy and teaching a large freshman chemistry class.
To keep costs down, Sadoway and Bradwell needed to use electrode materials that were earth-abundant, inexpensive, and long-lived. To achieve high voltage, they had to pair a strong electron donor with a strong electron acceptor. The top electrode (the electron donor) had to be low density, and the bottom electrode (the electron acceptor) high density. “Mercifully,” says Sadoway, “the way the periodic table is laid out, the strong electropositive [donor] metals are low density, and the strong electronegative [acceptor] metals are high density” (see Figure 2 in the slideshow above). And finally, all the materials had to be liquid at practical temperatures.
As their first combination, Sadoway and Bradwell chose magnesium for the top electrode, antimony for the bottom electrode, and a salt mixture containing magnesium chloride for the electrolyte. They then built prototypes of their cell — and they worked. The three liquid components self-segregated, and the battery performed as they had predicted. Spurred by their success, in 2010 they, along with Luis Ortiz SB ’96, PhD ’00, also a former member of Sadoway’s research group, founded a company — called initially the Liquid Metal Battery Corporation and later Ambri — to continue developing and scaling up the novel technology.
Supposedly with a good insulative refractive around the cell, one charge / discharge cycle per day keeps it molten.
I don’t know if it is conductive enough when solid to just start it with a current, it might need a preheat burner ;-) Propane powered battery? That would be a hoot ;-)
And a battery with a negative electrode of lithium and a positive electrode of an antimony-lead alloy operated at 450 C.
While working with the last combination, the researchers stumbled on an unexpected electrochemical phenomenon: They found that they could maintain the high cell voltage of their original pure antimony electrode with the new antimony-lead version — even when they made the composition as much as 80 percent lead in order to lower the melting temperature by hundreds of degrees.
“To our pleasant surprise, adding more lead to the antimony didn’t decrease the voltage, and now we understand why,” Sadoway says. “When lithium enters into an alloy of antimony and lead, the lithium preferentially reacts with the antimony because it’s a tighter bond. So when the lithium [from the top electrode] enters the bottom electrode, it ignores the lead and bonds with the antimony.”
That unexpected finding reminded them how little was known in this new field of research — and also suggested new cell chemistries to explore. For example, they recently assembled a proof-of-concept cell using a positive electrode of a lead-bismuth alloy, a negative electrode of sodium metal, and a novel electrolyte of a mixed hydroxide-halide. The cell operated at just 270 C — more than 400 C lower than the initial magnesium-antimony battery while maintaining the same novel cell design of three naturally separating liquid layers.
So yeah, don’t set it on a wooden lab bench…
I can see this helping with peak shaving (where otherwise you have generation capacity run for an hour a day or so) and maybe even help solar last through dinner time and evening TV. Can’t see it helping with week long events like a wind quiet week in winter overcast. Still going to need major generation capacity that’s dispatchable.
There’s this M.I.T. tease about the improved chemistry that’s 200 C lower operating temperature. That’s what gets it down to 450 C:
The original system, using magnesium for one of the battery’s electrodes and antimony for the other, required an operating temperature of 700 C. But with the new formulation, with one electrode made of lithium and the other a mixture of lead and antimony, the battery can operate at temperatures of 450 to 500 C.
Extensive testing has shown that even after 10 years of daily charging and discharging, the system should retain about 85 percent of its initial capacity — a key factor in making such a technology an attractive investment for electric utilities.
Currently, the only widely used system for utility-scale storage of electricity is pumped hydro, in which water is pumped uphill to a storage reservoir when excess power is available, and then flows back down through a turbine to generate power when it is needed. Such systems can be used to match the intermittent production of power from irregular sources, such as wind and solar power, with variations in demand. Because of inevitable losses from the friction in pumps and turbines, such systems return about 70 percent of the power that is put into them (which is called the “round-trip efficiency”).
Sadoway says his team’s new liquid-battery system can already deliver the same 70 percent efficiency, and with further refinements may be able to do better. And unlike pumped hydro systems — which are only feasible in locations with sufficient water and an available hillside — the liquid batteries could be built virtually anywhere, and at virtually any size. “The fact that we don’t need a mountain, and we don’t need lots of water, could give us a decisive advantage,” Sadoway says.
So yeah, I could see this as a pumped hydro alternative and maybe for peak shaving / fast surge buffering.
And there’s a wiki on it:
Professor Donald Sadoway at the Massachusetts Institute of Technology has pioneered the research of liquid-metal rechargeable batteries. Both Magnesium–antimony and more recently lead–antimony were used in experiments at MIT. The electrode and electrolyte layers are heated until they are liquid and self-segregate due to density and immiscibility. They may have longer lifetimes than conventional batteries, as the electrodes go through a cycle of creation and destruction during the charge–discharge cycle, which makes them immune to degradation affecting conventional battery electrodes.
The technology was proposed in 2009 based on magnesium and antimony separated by a molten salt. Magnesium was chosen as the negative electrode for its low cost and low solubility in the molten-salt electrolyte. Antimony was selected as the positive electrode due to its low cost and higher anticipated discharge voltage.
In 2011, the researchers demonstrated a cell with a lithium anode and a lead–antimony cathode, which had higher ionic conductivity and lower melting points (350–430 °C). The drawback of the Li chemistry is higher cost. A Li/LiF + LiCl + LiI/Pb-Sb cell with about 0.9 V open-circuit potential operating at 450 °C had electroactive material costs of US$100/kWh and US$100/kW and a projected 25-year lifetime. Its discharge power at 1.1 A/cm2 is only 44% (and 88% at 0.14 A/cm2).
Experimental data shows 69% storage efficiency, with good storage capacity (over 1000 mAh/cm2), low leakage (< 1 mA/cm2) and high maximal discharge capacity (over 200 mA/cm2). By October 2014 the MIT team achieved an operational efficiency of approximately 70% at high charge/discharge rates (275 mA/cm2), similar to that of pumped-storage hydroelectricity and higher efficiencies at lower currents. Tests showed that after 10 years of regular use, the system would retain about 85% of its initial capacity. In September 2014, a study described an arrangement using a molten alloy of lead and antimony for the positive electrode, liquid lithium for the negative electrode; and a molten mixture of lithium salts as the electrolyte.
In 2010, the Liquid Metal Battery Corporation (LMBC) was formed to commercialize the liquid-metal battery technology invented at MIT. LMBC was renamed Ambri in 2012; the name "Ambri" is derived from "cAMBRIdge" Massachusetts, where the company is headquartered and where MIT is located. In 2012 and 2014, Ambri received $40 million in funding from Bill Gates, Khosla Ventures, Total S.A., and GVB.
In September 2015, Ambri announced a layoff, pushing back commercial sales. but announced a return to the battery business with a redesigned battery in 2016.
A recent innovation is the PbBi alloy which enables a very low melting point lithium based battery. It uses a molten salt electrolyte based on LiCl-LiI and operates at 410 °C.
I wonder if sodium or potassium could be used in a DIY version that didn’t need to meet industrial requirements? “Typemetal” is not that common anymore, but it was a lead antimony alloy and may still be around. Back in the ’60s my home town newspaper still used cast type and a regular press. It was quite an operation. In the ’70s they went to photo offset (tin like metal plates) and the old linotype machine was stuck out for junk. Oh Well. Along with a great many pounds of type metal…
It does look like they are chasing the economies of scale that Lion cells already are forcing, so will need to start shipping product soon and fast to get ahead of it. There are also a lot of very low temperature alloys (like Woods Metal) and it might be interesting to try some of them. Just for a low temperature demonstrator even if the volts / amps were not all that great…
From the wiki:
Wood’s metal, also known as Lipowitz’s alloy or by the commercial names Cerrobend, Bendalloy, Pewtalloy and MCP 158, is a eutectic, fusible alloy with a melting point of approximately 70 °C (158 °F). It is a eutectic alloy of 50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium by weight. The alloy is named for Barnabas Wood.
There are others without the nasties like cadmium…
Alloy Melting point Eutectic? Bismuth Lead Tin Rose's metal 98 °C (208 °F) no 50% 25% 25%
So bismuth, lead, and tin are easy to get.
but I don’t know of any salt that melts that low. Absorb moisture and liquefy, yeah CaCl does that. But melt? Hmmm….
Salts characteristically have high melting points. For example, sodium chloride melts at 801 °C. Some salts with low lattice energies are liquid at or near room temperature. These include molten salts, which are usually mixtures of salts, and ionic liquids, which usually contain organic cations. These liquids exhibit unusual properties as solvents.
So it might be possible… So maybe something like a sodium / sodium acetate /Rose’s Metal battery running at boiling water temperature… Maybe not the greatest battery but as a demonstration it would be fun ;-)