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Molten-salt batteries are a class of
battery
Battery most often refers to:
* Electric battery, a device that provides electrical power
* Battery (crime), a crime involving unlawful physical contact
Battery may also refer to:
Energy source
*Automotive battery, a device to provide power t ...
that uses
molten salt
Molten salt is salt which is solid at standard temperature and pressure but enters the liquid phase due to elevated temperature. Regular table salt has a melting point of 801 °C (1474°F) and a heat of fusion of 520 J/g.[< ...]
s as an
electrolyte
An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon dis ...
and offers both a high
energy density
In physics, energy density is the amount of energy stored in a given system or region of space per unit volume. It is sometimes confused with energy per unit mass which is properly called specific energy or .
Often only the ''useful'' or extract ...
and a high
power density
Power density is the amount of power (time rate of energy transfer) per unit volume.
In energy transformers including batteries, fuel cells, motors, power supply units etc., power density refers to a volume, where it is often called volume p ...
. Traditional non-rechargeable thermal batteries can be stored in their solid state at room temperature for long periods of time before being activated by heating. Rechargeable liquid-metal batteries are used for industrial power backup, special
electric vehicle
An electric vehicle (EV) is a vehicle that uses one or more electric motors for propulsion. It can be powered by a collector system, with electricity from extravehicular sources, or it can be powered autonomously by a battery (sometimes cha ...
s and for
grid energy storage
Grid energy storage (also called large-scale energy storage) is a collection of methods used for energy storage on a large scale within an electrical power grid. Electrical energy is stored during times when electricity is plentiful and inexp ...
, to balance out intermittent
renewable power
Renewable energy is energy that is collected from renewable resources that are naturally replenished on a human timescale. It includes sources such as sunlight, wind, the movement of water, and geothermal heat. Although most renewable energy ...
sources such as
solar panels
A solar cell panel, solar electric panel, photo-voltaic (PV) module, PV panel or solar panel is an assembly of photovoltaic solar cells mounted in a (usually rectangular) frame, and a neatly organised collection of PV panels is called a phot ...
and
wind turbines
A wind turbine is a device that converts the kinetic energy of wind into electrical energy. Hundreds of thousands of large turbines, in installations known as wind farms, now generate over 650 gigawatts of power, with 60 GW added each year. ...
.
History
Thermal batteries originated during
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
when German scientist Georg Otto Erb developed the first practical cells using a salt mixture as an electrolyte. Erb developed batteries for military applications, including the
V-1 flying bomb
The V-1 flying bomb (german: Vergeltungswaffe 1 "Vengeance Weapon 1") was an early cruise missile. Its official Ministry of Aviation (Nazi Germany), Reich Aviation Ministry () designation was Fi 103. It was also known to the Allies as the buz ...
and the
V-2
The V-2 (german: Vergeltungswaffe 2, lit=Retaliation Weapon 2), with the technical name ''Aggregat 4'' (A-4), was the world’s first long-range guided ballistic missile. The missile, powered by a liquid-propellant rocket engine, was develope ...
rocket, and artillery fuzing systems. None of these batteries entered field use during the war. Afterwards, Erb was interrogated by British intelligence. His work was reported in "The Theory and Practice of Thermal Cells". This information was subsequently passed on to the United States Ordnance Development Division of the
National Bureau of Standards
The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical sci ...
. When the technology reached the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
in 1946, it was immediately applied to replacing the troublesome liquid-based systems that had previously been used to power artillery
proximity fuzes. They were used for
ordnance
Ordnance may refer to:
Military and defense
*Materiel in military logistics, including weapons, ammunition, vehicles, and maintenance tools and equipment.
**The military branch responsible for supplying and developing these items, e.g., the Unit ...
applications (e.g., proximity fuzes) since WWII and later in
nuclear weapons
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions (thermonuclear bomb), producing a nuclear explosion. Both bomb ...
. The same technology was studied by
Argonne National Laboratories
Argonne National Laboratory is a science and engineering research national laboratory operated by UChicago Argonne LLC for the United States Department of Energy. The facility is located in Lemont, Illinois, outside of Chicago, and is the larg ...
and other researchers in the 1980s for use in
electric vehicle
An electric vehicle (EV) is a vehicle that uses one or more electric motors for propulsion. It can be powered by a collector system, with electricity from extravehicular sources, or it can be powered autonomously by a battery (sometimes cha ...
s.
A 2021 study reported stable operation of a cell operating at over 400 cycles. The cell operated at 3.6 volts. Liquid sodium metal crosses a ceramic separator, reaching a mixture of liquid
sodium iodide
Sodium iodide (chemical formula NaI) is an ionic compound formed from the chemical reaction of sodium metal and iodine. Under standard conditions, it is a white, water-soluble solid comprising a 1:1 mix of sodium cations (Na+) and iodide anions (I ...
and
gallium chloride Gallium chloride may refer to:
* Gallium trichloride
Gallium trichloride is the chemical compound with the formula GaCl3. Solid gallium trichloride exists as a dimer with the formula Ga2Cl6. It is colourless and soluble in virtually all solven ...
, termed a "catholyte". The high price of gallium chloride was expected to keep the design from commercial use.
Rechargeable configurations
Since the mid-1960s much development work has been undertaken on
rechargeable batteries
A rechargeable battery, storage battery, or secondary cell (formally a type of energy accumulator), is a type of electrical battery which can be charged, discharged into a load, and recharged many times, as opposed to a disposable or prima ...
using
sodium
Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable iso ...
(Na) for the negative electrodes. Sodium is attractive because of its high
reduction potential
Redox potential (also known as oxidation / reduction potential, ''ORP'', ''pe'', ''E_'', or E_) is a measure of the tendency of a chemical species to acquire electrons from or lose electrons to an electrode and thereby be reduced or oxidised respe ...
of −2.71 volts, low weight, relative abundance, and low cost. In order to construct practical batteries, the sodium must be in liquid form. The
melting point
The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends ...
of sodium is . This means that sodium-based batteries operate at temperatures between . Research has investigated metal combinations with operating temperatures at and room temperature.
Sodium–sulfur
The
sodium–sulfur battery
A sodium–sulfur battery is a type of molten-salt battery constructed from liquid sodium (Na) and sulfur (S). This type of battery has a high energy density (its energy density is 5 times that of a lead-acid battery), high efficiency of charge/ ...
(NaS battery), along with the related
lithium–sulfur battery
The lithium–sulfur battery (Li–S battery) is a type of rechargeable battery. It is notable for its high specific energy. The low atomic weight of lithium and moderate atomic weight of sulfur means that Li–S batteries are relatively light (a ...
employs cheap and abundant electrode materials. It was the first
alkali-metal commercial battery. It used liquid
sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
for the positive electrode and a
ceramic
A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain ...
tube of
beta-alumina solid electrolyte Beta-alumina solid electrolyte (BASE) is a fast ion conductor material used as a membrane in several types of molten salt electrochemical cell. Currently there is no known substitute available. β-Alumina exhibits an unusual layered crystal structur ...
(BASE). Insulator corrosion was a problem because they gradually became conductive, and the self-discharge rate increased.
Because of their high specific power, NaS batteries have been proposed for space applications. An NaS battery for space use was successfully tested on the
Space Shuttle
The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program na ...
mission
STS-87
STS-87 was a Space Shuttle mission launched from Launch Complex 39B of the Kennedy Space Center on 19 November 1997. It was the 88th flight of the Space Shuttle and the 24th flight of '' Columbia''. The mission goals were to conduct experiments u ...
in 1997,
but the batteries have not been used operationally in space. NaS batteries have been proposed for use in the high-temperature environment of
Venus
Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never fa ...
.
A consortium formed by
Tokyo Electric Power Co. (TEPCO) and NGK Insulators Ltd. declared their interest in researching the NaS battery in 1983, and became the primary drivers behind the development of this type ever since. TEPCO chose the NaS battery because its component elements (sodium, sulfur and ceramics) are abundant in Japan. The first large-scale field testing took place at TEPCO's Tsunashima substation between 1993 and 1996, using 32 MW, 6.6 kV battery banks. Based on the findings from this trial, improved battery modules were developed and were made commercially available in 2000. The commercial NaS battery bank offers:
*Capacity : 25–250 kWh per bank
*Efficiency of 87%
*Lifetime of 2,500 cycles at 100% depth of discharge (DOD), or 4,500 cycles at 80% DOD
Sodium–nickel chloride (Zebra) battery
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A lower-temperature variant of molten-salt batteries was the development of the ZEBRA (originally, "Zeolite Battery Research Africa"; later, the "Zero Emissions Batteries Research Activity") battery in 1985, originally developed for electric vehicle applications. The battery uses with Na
+-beta-alumina ceramic electrolyte.
The battery operates at and uses molten
sodium tetrachloroaluminate
Sodium tetrachloroaluminate, also known as natrium chloroaluminate, is a chemical compound with the formula . It was discovered in the 20th century. It is the sodium salt of the tetrachloroaluminate anion.
Sodium tetrachloroaluminate can be prepa ...
(), which has a melting point of , as the electrolyte. The negative electrode is molten sodium. The positive electrode is
nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...
in the discharged state and
nickel chloride
Nickel(II) chloride (or just nickel chloride) is the chemical compound NiCl2. The anhydrous salt is yellow, but the more familiar hydrate NiCl2·6H2O is green. Nickel(II) chloride, in various forms, is the most important source of nickel for che ...
in the charged state. Because nickel and nickel chloride are nearly insoluble in neutral and
basic
BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College ...
melts, contact is allowed, providing little resistance to charge transfer. Since both and Na are liquid at the operating temperature, a sodium-conducting
β-alumina ceramic is used to separate the liquid sodium from the molten . The primary elements used in the manufacture of these batteries have much higher worldwide reserves and annual production than lithium.
It was invented in 1985 by the Zeolite Battery Research Africa Project (ZEBRA) group at the
Council for Scientific and Industrial Research (CSIR) in
Pretoria, South Africa
Pretoria () is South Africa's administrative capital, serving as the seat of the executive branch of government, and as the host to all foreign embassies to South Africa.
Pretoria straddles the Apies River and extends eastward into the foothi ...
. It can be assembled in the discharged state, using NaCl, Al, nickel and iron powder. The positive electrode is composed mostly of materials in the solid state, which reduces the likelihood of corrosion, improving safety.
Its specific energy is 100 Wh/kg; specific power is 150 W/kg. The β-alumina solid ceramic is unreactive to sodium metal and sodium aluminum chloride. Lifetimes of over 2,000 cycles and twenty years have been demonstrated with full-sized batteries, and over 4,500 cycles and fifteen years with 10- and 20-cell modules. For comparison,
LiFePO4 lithium iron phosphate batteries store 90–110 Wh/kg, and the more common
LiCoO2 lithium-ion batteries store 150–200 Wh/kg. A nano
lithium-titanate battery
The lithium-titanate or lithium-titanium-oxide (LTO) battery is a type of rechargeable battery which has the advantage of being faster to charge than other lithium-ion batteries but the disadvantage of having a much lower energy density.
Uses
T ...
stores 72 Wh/kg and can provide power of 760 W/kg.
The ZEBRA's liquid electrolyte freezes at , and the normal operating temperature range is . Adding iron to the cell increases its power response.
ZEBRA batteries are currently manufactured by FZSoNick and used as a power backup in the telecommunication industries, Oil&Gas and Railways. It is also used in special electric vehicles used in mining. In the past it was adopted in the
Modec
Modec was an electric vehicle manufacturer in Coventry, in the United Kingdom, specialising in Commercial vehicles in the N2 category. It unveiled its first model in April 2006 and announced its intention to commence series production in Ma ...
Electric Van, the
Iveco Daily
The Iveco Daily is a large light commercial vehicle, light commercial van produced by the Italy, Italian automaker Iveco since 1978; it was also sold as the Fiat Daily by Fiat Automobiles, Fiat until 1983. Unlike the more car-like unibody Fiat D ...
3.5 ton delivery vehicle, the prototype
Smart ED
The Smart EQ Fortwo, formerly Smart Fortwo electric drive, ''smart ed'' or Smart Fortwo EV, is a battery electric vehicle variant of the Smart Fortwo city car made by Smart (marque), Smart.
The Smart EQ Forfour is an electric variant of the large ...
, and the
Th!nk City
The Th!nk City is an electric city car that was produced by Norwegian carmaker Think Global, and production partner Valmet Automotive from 2008 to 2012. It is a small two-seater/2+2-seater highway capable vehicle, with a top speed of , and an all ...
. In 2011 the US Postal Service began testing all-electric delivery vans, one powered by a ZEBRA battery.
In 2010
General Electric
General Electric Company (GE) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable energ ...
announced a battery that it called a sodium–metal halide battery, with a 20-year lifetime. Its cathode structure consists of a conductive nickel network, molten salt electrolyte, metal current collector, carbon felt electrolyte reservoir and the active sodium–metal halide salts. In 2015, as a result of a global restructuring, the company abandoned the project. In 2017 Chinese battery maker Chilwee Group (also known as Chaowei) created a new company with General Electric (GE) to bring to market a Na-NiCl battery for industrial and energy storage applications.
When not in use, batteries are typically kept molten and ready for use because if allowed to solidify they typically take twelve hours to reheat and charge. This reheating time varies depending on the battery-pack temperature, and power available for reheating. After shutdown a fully charged battery pack loses enough energy to cool and solidify in five-to-seven days.
Sodium metal chloride batteries are very safe; a
thermal runaway
Thermal runaway describes a process that is accelerated by increased temperature, in turn releasing energy that further increases temperature. Thermal runaway occurs in situations where an increase in temperature changes the conditions in a way t ...
can be activated only by piercing the battery and also, in this unlikely event, no fire or explosion will be generated. For this reason and also for the possibility to be installed outdoor without cooling systems, make the sodium metal chloride batteries very suitable for the industrial and commercial energy storage installations.
Sumitomo
The is one of the largest Japanese ''keiretsu'', or business groups, founded by Masatomo Sumitomo (1585-1652) around 1615 during the early Edo period.
History
The Sumitomo Group traces its roots to a bookshop in Kyoto founded circa 1615 by Masa ...
studied a battery using a salt that is molten at , far lower than sodium based batteries, and operational at . It offers energy densities as high as 290 Wh/L and 224 Wh/kg and charge/discharge rates of 1C with a lifetime of 100 - 1000 charge cycles. The battery employs only nonflammable materials and neither ignites on contact with air nor risks thermal runaway. This eliminates waste-heat storage or fire- and explosion-proof equipment, and allows closer cell packing. The company claimed that the battery required half the volume of lithium-ion batteries and one quarter that of sodium–sulfur batteries. The cell used a nickel cathode and a glassy carbon anode.
In 2014 researchers identified a liquid sodium–cesium alloy that operates at and produced 420 milliampere-hours per gram. The new material was able to fully coat, or "wet," the electrolyte. After 100 charge/discharge cycles, a test battery maintained about 97% of its initial storage capacity. The lower operating temperature allowed the use of a less-expensive polymer external casing instead of steel, offsetting some of the increased cost of cesium.
Innovenergy in
Meiringen
Meiringen () is a municipality in the Interlaken-Oberhasli administrative district in the canton of Bern in Switzerland. Besides the village of Meiringen, the municipality includes the settlements of Balm, Brünigen, Eisenbolgen, Hausen, Prasti, ...
,
Switzerland
). Swiss law does not designate a ''capital'' as such, but the federal parliament and government are installed in Bern, while other federal institutions, such as the federal courts, are in other cities (Bellinzona, Lausanne, Luzern, Neuchâtel ...
has further optimised this technology with the use of domestically sourced raw materials, except for the nickel powder component. Despite the reduced capacity compared with
lithium-ion batteries
A lithium-ion or Li-ion battery is a type of rechargeable battery which uses the reversible reduction of lithium ions to store energy. It is the predominant battery type used in portable consumer electronics and electric vehicles. It also se ...
, the ZEBRA technology is applicable for
stationary energy storage from
solar power
Solar power is the conversion of energy from sunlight into electricity, either directly using photovoltaics (PV) or indirectly using concentrated solar power. Photovoltaic cells convert light into an electric current using the photovoltaic e ...
. In 2022, the company operated a 540 kwh storage facility for solar cells on the roof of a shopping center, and currently produces over a million battery units per year from sustainable, non-toxic materials (
table salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...
).
Liquid-metal batteries
Professor
Donald Sadoway
Donald Robert Sadoway (born 7 March 1950) is professor emeritus of materials chemistry at the Massachusetts Institute of Technology. He is a noted expert on batteries and has done significant research on how to improve the performance and longe ...
at the Massachusetts Institute of Technology has pioneered the research of liquid-metal rechargeable batteries, using both magnesium–antimony and more recently
lead–antimony. The electrode and electrolyte layers are heated until they are liquid and self-segregate due to density and
immiscibility. Such batteries 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 the degradation that afflicts conventional battery electrodes.
[ ()]
The technology was proposed in 2009 based on
magnesium
Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
and
antimony
Antimony is a chemical element with the symbol Sb (from la, stibium) and atomic number 51. A lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb2S3). Antimony compounds have been known since ancient time ...
separated by a molten salt.
[Staff (2012]
Ambri Technology
Ambri company web page, Retrieved 6 December 2012. 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/cm
2 is only 44% (and 88% at 0.14 A/cm
2).
Experimental data shows 69% storage efficiency, with good storage capacity (over 1000 mAh/cm
2), low leakage (< 1 mA/cm
2) and high maximal discharge capacity (over 200 mA/cm
2). By October 2014 the MIT team achieved an operational efficiency of approximately 70% at high charge/discharge rates (275 mA/cm
2), similar to that of
pumped-storage hydroelectricity
Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), is a type of hydroelectric energy storage used by electric power systems for load balancing. The method stores energy in the form of gravitational potential ...
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.
A recent innovation is the PbBi alloy which enables lower melting point lithium-based battery. It uses a molten salt electrolyte based on LiCl-LiI and operates at 410 °C.
Ionic liquids have been shown to have prowess for use in rechargeable batteries. The electrolyte is pure molten salt with no added solvent, which is accomplished by using a salt having a room temperature liquid phase. This causes a highly viscous solution, and is typically made with structurally large salts with malleable lattice structures.
Thermal batteries (non-rechargeable)
Technologies
Thermal batteries use an electrolyte that is solid and inactive at ambient temperatures. They can be stored indefinitely (over 50 years) yet provide full power in an instant when required. Once activated, they provide a burst of high power for a short period (a few tens of seconds to 60 minutes or more), with output ranging from
watt
The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Wa ...
s to
kilowatt
The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Wa ...
s. The high power is due to the high
ionic conductivity of the molten salt (resulting in a low internal resistance), which is three orders of magnitude (or more) greater than that of the
sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...
in a
lead–acid car battery.
One design uses a fuze strip (containing
barium chromate
Barium chromate, named barium tetraoxochromate(VI) by the IUPAC, is a yellow sand like powder with the formula BaCrO4. It is a known oxidizing agent and produces a green flame when heated, a result of the barium ions.
History
The first naturally o ...
and powdered
zirconium
Zirconium is a chemical element with the symbol Zr and atomic number 40. The name ''zirconium'' is taken from the name of the mineral zircon, the most important source of zirconium. The word is related to Persian '' zargun'' (zircon; ''zar-gun'', ...
metal in a ceramic paper) along the edge of the heat pellets to initiate the electrochemical reaction. The fuze strip is typically fired by an
electrical igniter or
squib which is activated with an electric current.
Another design uses a central hole in the middle of the battery stack, into which the high-energy electrical igniter fires a mixture of hot gases and
incandescent
Incandescence is the emission of electromagnetic radiation (including visible light) from a hot body as a result of its high temperature. The term derives from the Latin verb ''incandescere,'' to glow white. A common use of incandescence is ...
particles. This allows much shorter activation times (tens of milliseconds) vs. hundreds of milliseconds for the edge-strip design. Battery activation can be accomplished by a
percussion primer, similar to a
shotgun shell
A shotgun shell, shotshell or simply shell is a type of rimmed, cylindrical (straight-walled) cartridges used specifically in shotguns, and is typically loaded with numerous small, pellet-like spherical sub- projectiles called shot, fired thro ...
. The heat source should be gasless. The standard heat source typically consists of mixtures of
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
powder and
potassium perchlorate
Potassium perchlorate is the inorganic salt with the chemical formula K Cl O4. Like other perchlorates, this salt is a strong oxidizer although it usually reacts very slowly with organic substances. This, usually obtained as a colorless, crysta ...
in weight ratios of 88/12, 86/14, or 84/16. The higher the potassium perchlorate level, the higher the heat output (nominally 200, 259, and 297
cal Cal or CAL may refer to:
Arts and entertainment
* ''Cal'' (novel), a 1983 novel by Bernard MacLaverty
* "Cal" (short story), a science fiction short story by Isaac Asimov
* ''Cal'' (1984 film), an Irish drama starring John Lynch and Helen Mir ...
/
g respectively). This property of unactivated storage has the double benefit of avoiding deterioration of the active materials during storage and eliminating capacity loss due to
self-discharge
Self-discharge is a phenomenon in batteries in which internal chemical reactions reduce the stored charge of the battery without any connection between the electrodes or any external circuit. Self-discharge decreases the shelf life
Shelf life ...
until the battery is activated.
In the 1980s
lithium
Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid el ...
-alloy anodes replaced
calcium
Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...
or
magnesium
Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
anodes, with cathodes of
calcium chromate
Calcium chromate is an inorganic compound with the formula CaCrO4, ''i.e.'' the chromate salt of calcium. It is a bright yellow solid which is normally found in the dihydrate form CaCrO4·2H2O. A very rare anhydrous mineral form exists in nature, ...
,
vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer ( pas ...
or
tungsten oxides. Lithium–
silicon
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic tab ...
alloys are favored over the earlier lithium–aluminium alloys. The corresponding cathode for use with the lithium-alloy anodes is mainly
iron disulfide
Iron sulfide or Iron sulphide can refer to range of chemical compounds composed of iron and sulfur.
Minerals
By increasing order of stability:
* Iron(II) sulfide, FeS
* Greigite, Fe3S4 (cubic)
* Pyrrhotite, Fe1−xS (where x = 0 to 0.2) (monocli ...
(pyrite) replaced by cobalt disulfide for high-power applications. The electrolyte is normally a
eutectic mixture
A eutectic system or eutectic mixture ( ) is a homogeneous mixture that has a melting point lower than those of the constituents. The lowest possible melting point over all of the mixing ratios of the constituents is called the ''eutectic tempe ...
of
lithium chloride
Lithium chloride is a chemical compound with the formula Li Cl. The salt is a typical ionic compound (with certain covalent characteristics), although the small size of the Li+ ion gives rise to properties not seen for other alkali metal chlor ...
and
potassium chloride
Potassium chloride (KCl, or potassium salt) is a metal halide salt composed of potassium and chlorine. It is odorless and has a white or colorless vitreous crystal appearance. The solid dissolves readily in water, and its solutions have a salt ...
.
More recently, other lower-melting, eutectic electrolytes based on
lithium bromide
Lithium bromide (LiBr) is a chemical compound of lithium and bromine. Its extreme hygroscopic character makes LiBr useful as a desiccant in certain air conditioning systems.Wietelmann, Ulrich and Bauer, Richard J. (2005) "Lithium and Lithium Compo ...
,
potassium bromide
Potassium bromide ( K Br) is a salt, widely used as an anticonvulsant and a sedative in the late 19th and early 20th centuries, with over-the-counter use extending to 1975 in the US. Its action is due to the bromide ion (sodium bromide is equall ...
, and lithium chloride or
lithium fluoride
Lithium fluoride is an inorganic compound with the chemical formula LiF. It is a colorless solid, that transitions to white with decreasing crystal size. Although odorless, lithium fluoride has a bitter-saline taste. Its structure is analogous to ...
have also been used to provide longer operational lifetimes; they are also better conductors. The so-called "all-lithium" electrolyte based on
lithium chloride
Lithium chloride is a chemical compound with the formula Li Cl. The salt is a typical ionic compound (with certain covalent characteristics), although the small size of the Li+ ion gives rise to properties not seen for other alkali metal chlor ...
,
lithium bromide
Lithium bromide (LiBr) is a chemical compound of lithium and bromine. Its extreme hygroscopic character makes LiBr useful as a desiccant in certain air conditioning systems.Wietelmann, Ulrich and Bauer, Richard J. (2005) "Lithium and Lithium Compo ...
, and
lithium fluoride
Lithium fluoride is an inorganic compound with the chemical formula LiF. It is a colorless solid, that transitions to white with decreasing crystal size. Although odorless, lithium fluoride has a bitter-saline taste. Its structure is analogous to ...
(no potassium salts) is also used for high-power applications, because of its high ionic conductivity. A
radioisotope thermal generator
A radioisotope thermoelectric generator (RTG, RITEG), sometimes referred to as a radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioacti ...
, such as in the form of pellets of
90SrTiO
4, can be used for long-term delivery of heat for the battery after activation, keeping it in a molten state.
Uses
Thermal batteries are used almost exclusively for military applications, notably for nuclear weapons and
guided missiles
In military terminology, a missile is a guided airborne ranged weapon capable of self-propelled flight usually by a jet engine or rocket motor. Missiles are thus also called guided missiles or guided rockets (when a previously unguided rocket i ...
.
They are the primary power source for many missiles such as the
AIM-9 Sidewinder
The AIM-9 Sidewinder (where "AIM" stands for "Air Intercept Missile") is a short-range air-to-air missile which entered service with the US Navy in 1956 and subsequently was adopted by the US Air Force in 1964. Since then the Sidewinder has prov ...
,
AIM-54 Phoenix
The AIM-54 Phoenix is an American radar-guided, long-range air-to-air missile (AAM), carried in clusters of up to six missiles on the Grumman F-14 Tomcat, its only operational launch platform.
The Phoenix was the United States' only long-range ...
,
MIM-104 Patriot
The MIM-104 Patriot is a surface-to-air missile (SAM) system, the primary of its kind used by the United States Army and several allied states. It is manufactured by the U.S. defense contractor Raytheon and derives its name from the radar compon ...
,
BGM-71 TOW
The BGM-71 TOW ("Tube-launched, Optically tracked, Wire-guided") is an American anti-tank missile. TOW replaced much smaller missiles like the SS.10 and ENTAC, offering roughly twice the effective range, a more powerful warhead, and a greatly ...
,
BGM-109 Tomahawk
The Tomahawk () Land Attack Missile (TLAM) is a long-range, all-weather, jet-powered, subsonic cruise missile that is primarily used by the United States Navy and Royal Navy in ship and submarine-based land-attack operations.
Under contract f ...
and others. In these batteries the electrolyte is immobilized when molten by a special grade of
magnesium oxide
Magnesium oxide ( Mg O), or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium (see also oxide). It has an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2− ions ...
that holds it in place by
capillary action
Capillary action (sometimes called capillarity, capillary motion, capillary rise, capillary effect, or wicking) is the process of a liquid flowing in a narrow space without the assistance of, or even in opposition to, any external forces li ...
. This powdered mixture is pressed into
pellets to form a separator between the
anode
An anode is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, an electrode of the device through which conventional current leaves the device. A common mnemonic is ...
and
cathode
A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in whi ...
of each cell in the battery stack. As long as the electrolyte (salt) is solid, the battery is inert and remains inactive. Each cell also contains a
pyrotechnic heat source
A pyrotechnic heat source, also called heat pellet, is a pyrotechnic device based on a pyrotechnic composition with a suitable igniter. Its role is to produce controlled amount of heat. Pyrotechnic heat sources are usually based on thermite-like (o ...
, which is used to heat the cell to the typical operating temperature of 400–550 °C.
See also
*
Primary cell
A primary battery or primary cell is a battery (a galvanic cell) that is designed to be used once and discarded, and not recharged with electricity and reused like a secondary cell (rechargeable battery). In general, the electrochemical reaction ...
*
Secondary cell
A rechargeable battery, storage battery, or secondary cell (formally a type of energy accumulator), is a type of electrical battery which can be charged, discharged into a load, and recharged many times, as opposed to a disposable or prima ...
*
Smart grid
A smart grid is an electrical grid which includes a variety of operation and energy measures including:
*Advanced metering infrastructure (of which smart meters are a generic name for any utility side device even if it is more capable e.g. a f ...
*
Flow battery
A flow battery, or redox flow battery (after reduction–oxidation), is a type of electrochemical cell where chemical energy is provided by two chemical components dissolved in liquids that are pumped through the system on separate sides of a ...
*
Carnot battery
A Carnot battery is a type of energy storage system that stores electricity in thermal energy storage. During the charging process, electricity is converted into heat and kept in heat storage. During the discharging process, the stored heat is co ...
*
List of battery types
This list is a summary of notable electric battery types composed of one or more electrochemical cells. Three lists are provided in the table. The primary (non-rechargeable) and secondary (rechargeable) cell lists are lists of battery chemistry ...
References
External links
Sadoway Group - Liquid Metal BatteriesAmbri, Inc. - Batteries for clean energyHome battery storage
{{emerging technologies, energy=yes
Rechargeable batteries
Battery types
Energy storage
Grid energy storage