Lithium

Lithium ingots with a thin layer of black nitride tarnish

Like the other alkali metals, lithium has a single valence electron that is easily given up to form a cation.[4] Because of this, lithium is a good conductor of heat and electricity as well as a highly reactive element, though it is the least reactive of the alkali metals. Lithium's low reactivity is due to the proximity of its valence electron to its nucleus (the remaining two electrons are in the 1s orbital, much lower in energy, and do not participate in chemical bonds).[4] However, molten lithium is significantly more reactive than its solid form.[5][6]

Lithium metal is soft enough to be cut with a knife. When cut, it possesses a silvery-white color that quickly changes to gray as it oxidizes to lithium oxide.[4] While it has one of the lowest melting points among all metals (180 °C, 453 K), it has the highest melting and boiling points of the alkali metals.[7]

Lithium has a very low density (0.534 g/cm³), comparable with pine wood.[8] It is the least dense of all elements that are solids at room temperature; the next lightest solid element (potassium, at 0.862 g/cm³) is more than 60% denser. Furthermore, apart from helium and hydrogen, as a solid it is less dense than any other element as a liquid, being only two-thirds as dense as liquid nitrogen (0.808 g/cm³).[9] Lithium can float on the lightest hydrocarbon oils and is one of only three metals that can float on water, the other two being sodium and potassium.

Lithium floating in oil

Lithium's coefficient of thermal expansion is twice that of aluminium and almost four times that of iron.[10] Lithium is superconductive below 400 μK at standard pressure[11] and at higher temperatures (more than 9 K) at very high pressures (>20 GPa).[12] At temperatures below 70 K, lithium, like sodium, undergoes diffusionless phase change transformations. At 4.2 K it has a rhombohedral crystal system (with a nine-layer repeat spacing); at higher temperatures it transforms to face-centered cubic and then body-centered cubic. At liquid-helium temperatures (4 K) the rhombohedral structure is prevalent.[13] Multiple allotropic forms have been identified for lithium at high pressures.[14]

Lithium has a mass specific heat capacity of 3.58 kilojoules per kilogram-kelvin, the highest of all solids.[15][16] Because of this, lithium metal is often used in coolants for heat transfer applications.[15]

Naturally occurring lithium is composed of two stable isotopes, ⁶Li and ⁷Li, the latter being the more abundant (92.5% natural abundance).[4][17][18] Both natural isotopes have anomalously low nuclear binding energy per nucleon (compared to the neighboring elements on the periodic table, helium and beryllium); lithium is the only low numbered element that can produce net energy through nuclear fission. The two lithium nuclei have lower binding energies per nucleon than any other stable nuclides other than deuterium and helium-3.[19] As a result of this, though very light in atomic weight, lithium is less common in the Solar System than 25 of the first 32 chemical elements.[2] Seven radioisotopes have been characterized, the most stable being ⁸Li with a half-life of 838 ms and ⁹Li with a half-life of 178 ms. All of the remaining radioactive isotopes have half-lives that are shorter than 8.6 ms. The shortest-lived isotope of lithium is ⁴Li, which decays through proton emission and has a half-life of 7.6 × 10⁻²³ s.[20]

⁷Li is one of the primordial elements (or, more properly, primordial nuclides) produced in Big Bang nucleosynthesis. A small amount of both ⁶Li and ⁷Li are produced in stars, but are thought to be "burned" as fast as produced.[21] Additional small amounts of lithium of both ⁶Li and ⁷Li may be generated from solar wind, cosmic rays hitting heavier atoms, and from early solar system ⁷Be and ¹⁰Be radioactive decay.[22] While lithium is created in stars during stellar nucleosynthesis, it is further burned. ⁷Li can also be generated in carbon stars.[23]

Lithium isotopes fractionate substantially during a wide variety of natural processes,[24] including mineral formation (chemical precipitation), metabolism, and ion exchange. Lithium ions substitute for magnesium and iron in octahedral sites in clay minerals, where ⁶Li is preferred to ⁷Li, resulting in enrichment of the light isotope in processes of hyperfiltration and rock alteration. The exotic ¹¹Li is known to exhibit a nuclear halo. The process known as laser isotope separation can be used to separate lithium isotopes, in particular ⁷Li from ⁶Li.[25]

Nuclear weapons manufacture and other nuclear physics applications are a major source of artificial lithium fractionation, with the light isotope ⁶Li being retained by industry and military stockpiles to such an extent that it has caused slight but measurable change in the ⁶Li to ⁷Li ratios in natural sources, such as rivers. This has led to unusual uncertainty in the standardized atomic weight of lithium, since this quantity depends on the natural abundance ratios of these naturally-occurring stable lithium isotopes, as they are available in commercial lithium mineral sources.[26]

Both stable isotopes of lithium can be laser cooled and were used to produce the first quantum degenerate Bose-Fermi mixture.[27]

Although it was synthesized in the Big Bang, lithium (together with beryllium and boron) is markedly less abundant in the universe than other elements. This is a result of the comparatively low stellar temperatures necessary to destroy lithium, along with a lack of common processes to produce it.[28]

According to modern cosmological theory, lithium—in both stable isotopes (lithium-6 and lithium-7)—was one of the three elements synthesized in the Big Bang.[29] Though the amount of lithium generated in Big Bang nucleosynthesis is dependent upon the number of photons per baryon, for accepted values the lithium abundance can be calculated, and there is a "cosmological lithium discrepancy" in the universe: older stars seem to have less lithium than they should, and some younger stars have much more.[30] The lack of lithium in older stars is apparently caused by the "mixing" of lithium into the interior of stars, where it is destroyed,[31] while lithium is produced in younger stars. Though it transmutes into two atoms of helium due to collision with a proton at temperatures above 2.4 million degrees Celsius (most stars easily attain this temperature in their interiors), lithium is more abundant than current computations would predict in later-generation stars.[17]

Nova Centauri 2013 is the first in which evidence of lithium has been found.[32]

Lithium is also found in brown dwarf substellar objects and certain anomalous orange stars. Because lithium is present in cooler, less-massive brown dwarfs, but is destroyed in hotter red dwarf stars, its presence in the stars' spectra can be used in the "lithium test" to differentiate the two, as both are smaller than the Sun.[17][33][34] Certain orange stars can also contain a high concentration of lithium. Those orange stars found to have a higher than usual concentration of lithium (such as Centaurus X-4) orbit massive objects—neutron stars or black holes—whose gravity evidently pulls heavier lithium to the surface of a hydrogen-helium star, causing more lithium to be observed.[17]

On 27 May 2020, astronomers reported that classical novae explosions are the galactic producers of lithium.[35][36]

Although lithium is widely distributed on Earth, it does not naturally occur in elemental form due to its high reactivity.[4] The total lithium content of seawater is very large and is estimated as 230 billion tonnes, where the element exists at a relatively constant concentration of 0.14 to 0.25 parts per million (ppm),[37][38] or 25 micromolar;[39] higher concentrations approaching 7 ppm are found near hydrothermal vents.[38]

Estimates for the Earth's crustal content range from 20 to 70 ppm by weight.[40] Lithium constitutes about 0.002 percent of Earth's crust.[41] In keeping with its name, lithium forms a minor part of igneous rocks, with the largest concentrations in granites. Granitic pegmatites also provide the greatest abundance of lithium-containing minerals, with spodumene and petalite being the most commercially viable sources.[40] Another significant mineral of lithium is lepidolite which is now an obsolete name for a series formed by polylithionite and trilithionite.[42][43] A newer source for lithium is hectorite clay, the only active development of which is through the Western Lithium Corporation in the United States.[44] At 20 mg lithium per kg of Earth's crust,[45] lithium is the 25th most abundant element.

According to the Handbook of Lithium and Natural Calcium, "Lithium is a comparatively rare element, although it is found in many rocks and some brines, but always in very low concentrations. There are a fairly large number of both lithium mineral and brine deposits but only comparatively few of them are of actual or potential commercial value. Many are very small, others are too low in grade."[46]

The US Geological Survey estimates that in 2010, Chile had the largest reserves by far (7.5 million tonnes)[47] and the highest annual production (8,800 tonnes). One of the largest reserve bases[note 1] of lithium is in the Salar de Uyuni area of Bolivia, which has 5.4 million tonnes. Other major suppliers include Australia, Argentina and China.[48][49] As of 2015, the Czech Geological Survey considered the entire Ore Mountains in the Czech Republic as lithium province. Five deposits are registered, one near Cínovec is considered as a potentially economical deposit, with 160 000 tonnes of lithium.[50] In December 2019, Finnish mining company Keliber Oy reported its Rapasaari lithium deposit has estimated proven and probable ore reserves of 5.280 million tonnes.[51]

In June 2010, The New York Times reported that American geologists were conducting ground surveys on dry salt lakes in western Afghanistan believing that large deposits of lithium are located there. "Pentagon officials said that their initial analysis at one location in Ghazni Province showed the potential for lithium deposits as large as those of Bolivia, which now has the world's largest known lithium reserves."[52] These estimates are "based principally on old data, which was gathered mainly by the Soviets during their occupation of Afghanistan from 1979–1989". Stephen Peters, the head of the USGS's Afghanistan Minerals Project, said that he was unaware of USGS involvement in any new surveying for minerals in Afghanistan in the past two years. 'We are not aware of any discoveries of lithium,' he said."[53]

Lithia ("lithium brine") is associated with tin mining areas in Cornwall, England and an evaluation project from 400-meter deep test boreholes is under consideration. If successful the hot brines will also provide geothermal energy to power the lithium extraction and refining process.[54]

Lithium is found in trace amount in numerous plants, plankton, and invertebrates, at concentrations of 69 to 5,760 parts per billion (ppb). In vertebrates the concentration is slightly lower, and nearly all vertebrate tissue and body fluids contain lithium ranging from 21 to 763 ppb.[38] Marine organisms tend to bioaccumulate lithium more than terrestrial organisms.[55] Whether lithium has a physiological role in any of these organisms is unknown.[38]

Organolithium reagents are known in which there is a direct bond between carbon and lithium atoms. These compounds feature covalent metal–carbon bonds that are strongly polarized towards the carbon, allowing them to effectively serve as a metal-stabilized carbanions, although their solution and solid-state structures are more complex than this simplistic view suggests due to the formation of oligomeric clusters.[89] Thus, these are extremely powerful bases and nucleophiles. They have also been applied in asymmetric synthesis in the pharmaceutical industry. For laboratory organic synthesis, many organolithium reagents are commercially available in solution form. These reagents are highly reactive, and are sometimes pyrophoric.

Like its inorganic compounds, almost all organic compounds of lithium formally follow the duet rule (e.g., BuLi, MeLi). However, it is important to note that in the absence of coordinating solvents or ligands, organolithium compounds form dimeric, tetrameric, and hexameric clusters (e.g., BuLi is actually [BuLi]₆ and MeLi is actually [MeLi]₄) which feature multi-center bonding and increase the coordination number around lithium. These cluster are broken down into smaller or monomeric units in the presence of solvents like dimethoxyethane (DME) or ligands like tetramethylethylenediamine (TMEDA).[90] As an exception to the duet rule, a two-coordinate lithate complex with four electrons around lithium, [Li(thf)₄]⁺[((Me₃Si)₃C)₂Li]^–, has been characterized crystallographically.[91]

Worldwide identified reserves in 2017, 2018, 2019 and 2020 were estimated by the US Geological Survey (USGS) to be 14 million, 16 million, 14 million and 17 million tonnes, respectively.[48] An accurate estimate of world lithium reserves is difficult.[93][94] One reason for this is that most lithium classification schemes are developed for solid ore deposits, whereas brine is a fluid that is problematic to treat with the same classification scheme due to varying concentrations and pumping effects.[95]

Worldwide lithium resources identified by USGS started to increase in 2017 owing to continuing exploration. Identified resources in 2016, 2017, 2018, 2019 and 2020 were 41, 47, 54, 62 and 80 million tonnes, respectively.[48]

The world in 2013 was estimated to contain about 15 million tonnes of lithium reserves, while 65 million tonnes of known resources were reasonable. A total of 75% of everything could typically be found in the ten largest deposits of the world.[96] Another study noted that 83% of the geological resources of lithium are located in six brine, two pegmatite, and two sedimentary deposits.[97]

The world's top four lithium-producing countries from 2019, as reported by the US Geological Survey are Australia, Chile, China and Argentina.[48] The intersection of Chile, Bolivia, and Argentina make up the region known as the Lithium Triangle. The Lithium Triangle is known for its high quality salt flats including Bolivia's Salar de Uyuni, Chile's Salar de Atacama, and Argentina's Salar de Arizaro. The Lithium Triangle is believed to contain over 75% of existing known lithium reserves.[98] Deposits are found in South America throughout the Andes mountain chain. Chile is the leading producer, followed by Argentina. Both countries recover lithium from brine pools. According to USGS, Bolivia's Uyuni Desert has 5.4 million tonnes of lithium.[99][100] Half the world's known reserves are located in Bolivia along the central eastern slope of the Andes. In 2009, Bolivia negotiated with Japanese, French, and Korean firms to begin extraction.[99]

In the US, lithium is recovered from brine pools in Nevada.[15] A deposit discovered in 2013 in Wyoming's Rock Springs Uplift is estimated to contain 228,000 tons. Additional deposits in the same formation were estimated to be as much as 18 million tons.[102]

According to a later 2011 study by Lawrence Berkeley National Laboratory and the University of California, Berkeley, the then estimated reserve base of lithium should not be a limiting factor for large-scale battery production for electric vehicles because an estimated 1 billion 40 kWh Li-based batteries could be built with those reserves[103] - about 10 kg of lithium per car.[104] Another 2011 study at the University of Michigan and Ford Motor Company found enough resources to support global demand until 2100, including the lithium required for the potential widespread transportation use. The study estimated global reserves at 39 million tons, and total demand for lithium during the 90-year period annualized at 12–20 million tons, depending on the scenarios regarding economic growth and recycling rates.[105]

In 2014, The Financialist stated that demand for lithium was growing at more than 12% a year. According to Credit Suisse, this rate exceeded projected availability by 25%. The publication compared the 2014 lithium situation with oil, whereby "higher oil prices spurred investment in expensive deepwater and oil sands production techniques"; that is, the price of lithium would continue to rise until more expensive production methods that could boost total output would receive the attention of investors.[106]

On 16 July 2018 2.5 million tonnes of high-grade lithium resources and 124 million pounds of uranium resources were found in the Falchani hard rock deposit in the region Puno, Peru.[107]

In 2019, world production of lithium from spodumene was around 80,000t per annum, primarily from the Greenbushes pegmatite of Western Australia and from some Chinese and Chilean sources. The Talison mine in Greenbushes, Western Australia is reported to be the largest and to have the highest grade of ore at 2.4% Li₂O (2012 figures).[108]

There is estimated to be 230 billion tons of lithium in the oceans,[109] but the concentration is 0.1-0.2ppm, making it more expensive to extract with 2020 technology than from land based brine and rock.

In 1998, the price of lithium metal was about 95 USD/kg (or US$43/lb).[110] After the 2007 financial crisis, major suppliers, such as Sociedad Química y Minera (SQM), dropped lithium carbonate pricing by 20%.[111] Prices rose in 2012. A 2012 Business Week article outlined the oligopoly in the lithium space: "SQM, controlled by billionaire Julio Ponce, is the second-largest, followed by Rockwood, which is backed by Henry Kravis’s KKR & Co., and Philadelphia-based FMC", with Talison mentioned as the biggest producer.[112] Global consumption may jump to 300,000 metric tons a year by 2020 from about 150,000 tons in 2012, to match the demand for lithium batteries that has been growing at about 25% a year, outpacing the 4% to 5% overall gain in lithium production.[112]

Analyses of the extraction of lithium from seawater, published in 1975

Lithium and its compounds were historically extracted from hard rock but by the 1990s mineral springs, brine pools, and brine deposits became the dominant source. Most of these were in Chile, Argentina and Bolivia. by 2018 hard rock had once again become a significant contributor, and by 2020 Australia expanded spodumene mining to become the leading lithium producing country in the world (see table above).

Low-cobalt cathodes for lithium batteries are expected to require lithium hydroxide rather than lithium carbonate as a feedstock, and this trend favours rock as a source.[113][114][115]

To make lithium intermediates from brine, the brine is first pumped up from underground pools and concentrated by solar evaporation. When the lithium concentration is sufficient, lithium carbonate and lithium hydroxide are precipitated by addition of sodium carbonate and calcium hydroxide respectively.[116] Each batch takes from 18 to 24 months.[117]

The use of electrodialysis and electrochemical intercalation has been proposed to extract lithium from seawater (which contains lithium at 0.2 parts per million), but it is not yet commercially viable.[118][119][120]

Another potential source of lithium is the leachates of geothermal wells, which are carried to the surface.[121] Recovery of lithium has been demonstrated in the field; the lithium is separated by simple filtration.[122] Reserves are more limited than those of brine reservoirs and hard rock.

It is expected that lithium will be recycled from end-of-life lithium-ion batteries in the future[123] but as of 2020, there are insufficient quantities of batteries to recycle, and the technology is not well developed. In any case, the most valuable component is likely to remain the NCM cathode material, and the recovery of this material is expected to be the driver.

Producers point out that lithium brine is (obviously) not usable for drinking or agriculture. There is a dispute about whether brine extraction causes an influx of fresh water and thus influences the groundwater at the edge of the salt flats. In VW's opinion, this matter is not yet sufficiently researched. Copper mining, tourism, and agriculture also consume significant water, and climate change cannot be dismissed.[124]

The process and environmental costs for geothermal leachates are primarily those of the already-operating well; net environmental impacts may thus be positive.[125]

Currently, there are a number of options available in the marketplace to invest in the metal. While buying physical stock of lithium is hardly possible, investors can buy shares of companies engaged in lithium mining and producing.[126] Also, investors can purchase a dedicated lithium ETF offering exposure to a group of commodity producers.

Lithium oxide is widely used as a flux for processing silica, reducing the melting point and viscosity of the material and leading to glazes with improved physical properties including low coefficients of thermal expansion. Worldwide, this is one of the largest use for lithium compounds.[127][129] Glazes containing lithium oxides are used for ovenware. Lithium carbonate (Li₂CO₃) is generally used in this application because it converts to the oxide upon heating.[130]

Late in the 20th century, lithium became an important component of battery electrolytes and electrodes, because of its high electrode potential. Because of its low atomic mass, it has a high charge- and power-to-weight ratio. A typical lithium-ion battery can generate approximately 3 volts per cell, compared with 2.1 volts for lead-acid and 1.5 volts for zinc-carbon. Lithium-ion batteries, which are rechargeable and have a high energy density, differ from lithium batteries, which are disposable (primary) batteries with lithium or its compounds as the anode.[131][132] Other rechargeable batteries that use lithium include the lithium-ion polymer battery, lithium iron phosphate battery, and the nanowire battery.

Over the years opinions have been differing about potential growth. A 2008 study concluded that "realistically achievable lithium carbonate production would be sufficient for only a small fraction of future PHEV and EV global market requirements", that "demand from the portable electronics sector will absorb much of the planned production increases in the next decade", and that "mass production of lithium carbonate is not environmentally sound, it will cause irreparable ecological damage to ecosystems that should be protected and that LiIon propulsion is incompatible with the notion of the 'Green Car'".[49]

The third most common use of lithium is in greases. Lithium hydroxide is a strong base and, when heated with a fat, produces a soap made of lithium stearate. Lithium soap has the ability to thicken oils, and it is used to manufacture all-purpose, high-temperature lubricating greases.[15][133][134]

Lithium (e.g. as lithium carbonate) is used as an additive to continuous casting mould flux slags where it increases fluidity,[135][136] a use which accounts for 5% of global lithium use (2011).[48] Lithium compounds are also used as additives (fluxes) to foundry sand for iron casting to reduce veining.[137]

Lithium (as lithium fluoride) is used as an additive to aluminium smelters (Hall–Héroult process), reducing melting temperature and increasing electrical resistance,[138] a use which accounts for 3% of production (2011).[48]

When used as a flux for welding or soldering, metallic lithium promotes the fusing of metals during the process[139] and eliminates the forming of oxides by absorbing impurities.[140] Alloys of the metal with aluminium, cadmium, copper and manganese are used to make high-performance aircraft parts (see also Lithium-aluminium alloys).[141]

Lithium has been found effective in assisting the perfection of silicon nano-welds in electronic components for electric batteries and other devices.[142]

Lithium compounds are used as pyrotechnic colorants and oxidizers in red fireworks and flares.[15][144]

Lithium chloride and lithium bromide are hygroscopic and are used as desiccants for gas streams.[15] Lithium hydroxide and lithium peroxide are the salts most used in confined areas, such as aboard spacecraft and submarines, for carbon dioxide removal and air purification. Lithium hydroxide absorbs carbon dioxide from the air by forming lithium carbonate, and is preferred over other alkaline hydroxides for its low weight.

Lithium peroxide (Li₂O₂) in presence of moisture not only reacts with carbon dioxide to form lithium carbonate, but also releases oxygen.[145][146] The reaction is as follows:

2 Li₂O₂ + 2 CO₂ → 2 Li₂CO₃ + O₂.

Some of the aforementioned compounds, as well as lithium perchlorate, are used in oxygen candles that supply submarines with oxygen. These can also include small amounts of boron, magnesium, aluminum, silicon, titanium, manganese, and iron.[147]

Lithium fluoride, artificially grown as crystal, is clear and transparent and often used in specialist optics for IR, UV and VUV (vacuum UV) applications. It has one of the lowest refractive indexes and the furthest transmission range in the deep UV of most common materials.[148] Finely divided lithium fluoride powder has been used for thermoluminescent radiation dosimetry (TLD): when a sample of such is exposed to radiation, it accumulates crystal defects which, when heated, resolve via a release of bluish light whose intensity is proportional to the absorbed dose, thus allowing this to be quantified.[149] Lithium fluoride is sometimes used in focal lenses of telescopes.[15][150]

The high non-linearity of lithium niobate also makes it useful in non-linear optics applications. It is used extensively in telecommunication products such as mobile phones and optical modulators, for such components as resonant crystals. Lithium applications are used in more than 60% of mobile phones.[151]

Organolithium compounds are widely used in the production of polymer and fine-chemicals. In the polymer industry, which is the dominant consumer of these reagents, alkyl lithium compounds are catalysts/initiators.[152] in anionic polymerization of unfunctionalized olefins.[153][154][155] For the production of fine chemicals, organolithium compounds function as strong bases and as reagents for the formation of carbon-carbon bonds. Organolithium compounds are prepared from lithium metal and alkyl halides.[156]

Many other lithium compounds are used as reagents to prepare organic compounds. Some popular compounds include lithium aluminium hydride (LiAlH₄), lithium triethylborohydride, n-butyllithium and tert-butyllithium.

The launch of a torpedo using lithium as fuel

Metallic lithium and its complex hydrides, such as Li[AlH₄], are used as high-energy additives to rocket propellants.[17] Lithium aluminum hydride can also be used by itself as a solid fuel.[157]

The Mark 50 torpedo stored chemical energy propulsion system (SCEPS) uses a small tank of sulfur hexafluoride gas, which is sprayed over a block of solid lithium. The reaction generates heat, creating steam to propel the torpedo in a closed Rankine cycle.[158]

Lithium hydride containing lithium-6 is used in thermonuclear weapons, where it serves as fuel for the fusion stage of the bomb.[159]

Lithium-6 is valued as a source material for tritium production and as a neutron absorber in nuclear fusion. Natural lithium contains about 7.5% lithium-6 from which large amounts of lithium-6 have been produced by isotope separation for use in nuclear weapons.[160] Lithium-7 gained interest for use in nuclear reactor coolants.[161]

Lithium deuteride was used as fuel in the Castle Bravo nuclear device.

Lithium deuteride was the fusion fuel of choice in early versions of the hydrogen bomb. When bombarded by neutrons, both ⁶Li and ⁷Li produce tritium — this reaction, which was not fully understood when hydrogen bombs were first tested, was responsible for the runaway yield of the Castle Bravo nuclear test. Tritium fuses with deuterium in a fusion reaction that is relatively easy to achieve. Although details remain secret, lithium-6 deuteride apparently still plays a role in modern nuclear weapons as a fusion material.[162]

Lithium fluoride, when highly enriched in the lithium-7 isotope, forms the basic constituent of the fluoride salt mixture LiF-BeF₂ used in liquid fluoride nuclear reactors. Lithium fluoride is exceptionally chemically stable and LiF-BeF₂ mixtures have low melting points. In addition, ⁷Li, Be, and F are among the few nuclides with low enough thermal neutron capture cross-sections not to poison the fission reactions inside a nuclear fission reactor.[note 3][163]

In conceptualized (hypothetical) nuclear fusion power plants, lithium will be used to produce tritium in magnetically confined reactors using deuterium and tritium as the fuel. Naturally occurring tritium is extremely rare, and must be synthetically produced by surrounding the reacting plasma with a 'blanket' containing lithium where neutrons from the deuterium-tritium reaction in the plasma will fission the lithium to produce more tritium:

⁶Li + n → ⁴He + ³H.

Lithium is also used as a source for alpha particles, or helium nuclei. When ⁷Li is bombarded by accelerated protons ⁸Be is formed, which undergoes fission to form two alpha particles. This feat, called "splitting the atom" at the time, was the first fully man-made nuclear reaction. It was produced by Cockroft and Walton in 1932.[164][165]

In 2013, the US Government Accountability Office said a shortage of lithium-7 critical to the operation of 65 out of 100 American nuclear reactors "places their ability to continue to provide electricity at some risk". Castle Bravo first used lithium-7, in the Shrimp, its first device, which weighed only 10 tons, and generated massive nuclear atmospheric contamination of Bikini Atoll. This perhaps accounts for the decline of US nuclear infrastructure.[166] The equipment needed to separate lithium-6 from lithium-7 is mostly a cold war leftover. The US shut down most of this machinery in 1963, when it had a huge surplus of separated lithium, mostly consumed during the twentieth century. The report said it would take five years and $10 million to $12 million to reestablish the ability to separate lithium-6 from lithium-7.[167]

Reactors that use lithium-7 heat water under high pressure and transfer heat through heat exchangers that are prone to corrosion. The reactors use lithium to counteract the corrosive effects of boric acid, which is added to the water to absorb excess neutrons.[167]

Lithium is useful in the treatment of bipolar disorder.[168] Lithium salts may also be helpful for related diagnoses, such as schizoaffective disorder and cyclic major depression. The active part of these salts is the lithium ion Li⁺.[168] They may increase the risk of developing Ebstein's cardiac anomaly in infants born to women who take lithium during the first trimester of pregnancy.[169]

Lithium has also been researched as a possible treatment for cluster headaches.[170]