Salted Earth – At one Corner of the Lithium Triangle

A photograph showing the great salt lake plain at Uyuni in the Lithium Triangle, in South America.Salar de Uyuni, Bolivia

A crisp and perfectly flat white plain lies like freshly fallen snow, 100 kilometres (60 miles) across and 3,600 metres (12,000 ft) up in the remote Bolivian Andes.  This hauntingly beautiful place, Salar de Uyuni, could be part of the key to tackling climate change, helping to wean the World away from its love of fossil fuels. 

Bolivia’s Salar de Uyuni is at one corner of the “Lithium Triangle”.  Take a look at a satellite image of South America.  Half-way down the west coast is a distinctive white speck.  Up close, that area turns out to be one of the largest, most extraordinary and unspoilt places on Earth – the World’s biggest salt flat.

 

The Lithium Triangle

Two maps showing the location of the Lithium Triangle in South America.The Lithium Triangle is located on the borders where Chile, Bolivia and Argentina meet.  Bounded by the Salar de Atacama, Salar de Uyuni and Salar del Humbre Muerto, the Lithium Triangle also takes in the northern ends of Chile and Argentina.

Over 70% of the World’s economic lithium deposits are found in this one small location on Earth.  As a result, these three countries dominate world lithium supplies thanks to the incredible tectonic forces that shaped the South American continent.

Geological subduction of the Pacific tectonic plate under the Chilean coast, together with the resulting tectonic uplift of South America, created large localised depressions which cause water to collect into lakes, instead of flowing into the sea.  The lithium salts that dissolve out of the surrounding rocks gather in these great lakes.

The Andes squeeze almost every drop of water out of the prevailing winds off the Pacific, making their western slopes some of the most arid spots on Earth.  This dry climate causes the lakes to evaporate, leaving behind crystallised salts seen at the salt flats of the Salar de Uyuni and Salar de Atacama, in the middle of the Atacama desert – the driest place on Earth.

 

The Saltwater Aquifer at Atacama, Chile

A salt lake bed consists of dried out sodium chloride Na+Cl – that’s common salt.  This forms a solid halite deposit, known as rock salt.  Near the surface, this halite is porous and permeable to the flow of water.

Effectively, this creates an aquifer through which lithium-rich brine and other important minerals (boron, magnesium, potassium) can flow.  Further down, millennia of cementation from the precipitation of salts by earlier brine flows and compaction block up the pores and interstices of the halite deposit, turning it into a much more impermeable and resilient material. 

The useful brine is therefore only located in the top 40 metres of dried salt flats.

 

Salar de Atacama

An aerial photograph showing a lithium mine in the Andes, at Atacama, Chile.Not as picturesque as the Salar de Uyuni, the Salar de Atacama is swept by the dust that blows in from the surrounding desert.  Salar de Atacama is the biggest single source of lithium currently being mined.

Seismic surveys of the Atacama deposit showed that the highest porosity extends to a depth of 20 to 25 metres, with additional lower porosity halite down to 35 metres.  Below this depth, salt cores show complete re-crystallisation of the halite into a solid mass, devoid of any pores.

This means there is no lithium to extract below the pumping depth.  Only solid rock salt.

The upper 30-metre has high transmissivity, which means that brine can only flow freely in this region to refill the areas from where it is pumped out.

While the Salar de Atacama has a total surface or 3,500 km2, its central halite nucleus is 1,000-1,400 km2 in area.  The main commercially-important area in the salar is the top 30-metre layer beneath the surface crust of this nucleus.

Below this layer, the nucleus is solid rock salt down to 600 m and 900 m in places.  The contour map shows a inhomogeneous lithium distribution.  The southern half of the lake bed demonstrates a lithium concentration of 1,000-1,500 ppm.

The area of highest lithium concentration, where the production is currently located, lies in a very small area of the southern shore, approximately 100 km2.  Contour lines go up to 4,000 ppm, and concentrations as high as 7,000 ppm have been identified.

 

A photograph showing three glass vials containing different kinds of alkali metal: Lithium, Sodium and Potassium. Lithium is shown to be floating on oil in the first sample.Lithium

Pure lithium Li3 is a soft and shiny silvery-white metal – soft enough in fact to be cut with a knife.  In its purest form, lithium will actually float on the oil it is normally stored in by chemists.  And it must be stored in oil, under the inert gas argon, for a very good reason.

Like the other alkali metals, lithium has a single valence electron that is easily given up to form a cation – an ion with fewer electrons than protons, giving it a positive charge.  This particularity makes it a good conductor of heat and electricity, as well as a highly reactive element.

Alkaline elements readily dissolve in water.  Lithium is the first of the alkali metals, and just like its near kin sodium and potassium, it will react spontaneously to water, although not quite as violently as those other two!

Because of its high reactivity, lithium never occurs freely in Nature.  Instead, it only appears in ionic compounds.  Lithium occurs in a number of pegmatitic minerals.  Due to its solubility as an ion, it is also present in ocean water and is commonly retrieved from brines or clays.  On a commercial scale, lithium is isolated electrolytically from a mixture of lithium chloride and potassium chloride.

Since the two stable lithium isotopes found in nature have among the lowest binding energies per nucleon of all stable nuclides, the nuclei of lithium verge on instability.  Because of this relative nuclear instability, lithium is less common in the Solar System than 25 of the first 32 chemical elements, even though the nuclei are very light in atomic weight.  For related reasons, lithium has important links to nuclear physics.

The transmutation of lithium atoms to helium in 1932 was the first fully man-made nuclear reaction, and lithium-6 deuteride serves as a fusion fuel in staged thermonuclear weapons.

Right after the primordial gases hydrogen and helium, lithium is the third element of the periodic table.  Each one of its tiny atoms contain just three protons, making it the lightest of all metals, perfect for lightweight batteries.

 

More than just Watch Batteries

Batteries are not the only things that take advantage of lithium’s unique electrochemical properties.  All living organisms have trace amounts of lithium.  The human body does as well.  The element appears to serve no vital biological function however, since animals and plants can remain healthy without it.  But non-vital functions have not yet been ruled out.

A photograph showing 400mg Lithium Carbonate pharmaceutical tablets.Pills are made of purified lithium carbonate, the very same naturally-occurring substance that is mined in many salt lakes today.

Administered as any of several lithium salts, the lithium ion Li+ has proved a useful mood-stabilising drug in the treatment of bipolar disorder, due to the neurological effects of the ion in the human body.

How they actually work remains something of a mystery.  However, it probably has something to do with the fact that our nerves and brains don’t operate using flows of electrons, but instead rely on a flow of ions – positively charged particles of sodium and potassium.

From the mid-1980s onwards, lithium was mainly used to decrease the melting temperature of glass and improve the melting behaviour of aluminium oxide when using the Hall-Héroult process for smelting aluminium.  Both of these two uses dominated the market until the middle of the 1990s.  After the end of the nuclear arms race, demand for lithium decreased and the sale of Department of Energy stockpiles on the open market further reduced prices.

But in the mid-1990s, several companies started to extract lithium from brine which proved to be a less expensive method than underground or even open-pit mining.

Lithium, a key ingredient in lightweight batteries, is already powering the modern World in more ways than one, and it could also be key to getting the World to reduce its reliance on fossil fuels.

 

A photograph showing a view of the desert with a pile of salt bricks at the forefront.The World’s Biggest Lithium Flats

Under its thick salt crust, Salar de Uyuni is also one the world’s biggest single deposits of lithium, along with Salar de Atacama and Salar del Humbre Muerto, accounting for perhaps a third of the World’s resources of this alkaline metal.  Which is the reason why, as pristine as it may look now, the chances are that 50 years from now, it will all be gone – dredged, crystallised and carted away.

That’s because…

 

Data Comparison of South American Salares in the Lithium Triangle

 BoliviaChileArgentina
Salar NameUyuniAtacamaHombre Muerto
Altitude (km)3.72.34.3
Area (km 2)8,0003,000570
Li Concentration (%/wt)0.03500.15000.0620
Mg/Li Ratio18.66.41.4
Evaporation (mm/year)1,5003,2002,300

Source: US Geological Survey, Stratfor, “An Abundance of Lithium” by Keith Evans, Meridian International

Going back to the 1980s, lithium was one of the more obscure members of the periodic table, much as its next-door neighbour beryllium still remains today.  That all began to change in 1991, when Sony launched the first ever portable gadget powered by a lithium-ion battery and lithium became increasingly ubiquitous.

Today, of course, the words “lithium” and “battery” are almost synonymous – this soft metal is in all our smartphones, tablets and laptops.

 

Inside the Lithium-Ion Battery

A close-up photograph showing a cross section through a Lithium battery.
Inside a Lithium Battery… Source: National Geographic

The secret of lithium’s success is that it is the third element of the periodic table, right after the gases hydrogen and helium.  Its tiny atoms, containing just three protons each, make lithium the lightest of all metals.  All of which makes lithium an ideal material for light-weight batteries.

“We think of batteries as producing an electrical current, sending electrons around a circuit,” explains chemistry professor Andrea Sella of University College London.  “But of course, as a chemist, I am interested in what goes on inside the battery.  And for every electron, a lithium ion also has to move inside the battery.”

In a lithium-ion battery, the two electrodes with an electrically insulating separator sandwiched between them, are often coiled up much like a Swiss roll.  During discharge, electrical current flows from the anode through the device that the battery is powering.  While simultaneously, positively charged lithium ions travel from the anode (carbon) to the cathode (cobalt or manganese oxide) through the separator.  The electrolyte is usually lithium salts in organic solvents.  Upon reaching the cathode, lithium ions embed themselves in its metal oxide structure, which simultaneously accepts electrons from the external circuit.  During charging, the process occurs, but in reverse.

Being so small, the atoms slip easily between the layered materials that make up the battery.  And being so light, lithium is the most energy dense of battery materials, meaning it can store the most energy for a given weight.

This is why lithium is so important for the battle against climate change.

Lithium is the optimum battery material if you need to carry your energy store with you – in the hippest new-fangled gadgets, or in our future cars.

However, if the World is to meet the future demand, other lithium deposits will need to be opened up to exploitation.

 

The Future…

Bolivia and Salar de Uyuni

The Atacama deposit is richer in lithium than Uyuni.  It is also easier to exploit because it is nearer the sea and located on a flat plain, instead of at the top of a mountain range, which makes the roads and infrastructure needed for export much cheaper.  Bolivia is rich in mineral resources.  However, it is crippled by its limited infrastructureApart from the geographical constraints, politics is also a factor challenging the exploitation.

Both these factors will play a role in determining whether Bolivia is able to develop and produce lithium at the rate projected by the government.

Salar de Atacama is controlled by a government in Santiago that has a long happy working relationship with foreign mining companies who have exploited Chile’s largest mineral resource – copperIf the Bolivian government can learn to work with foreign investors who have the necessary expertise and financial resources to bring the mineral to market, the Salar de Uyuni could prove a bonanza for one of the poorest countries in South America.

The Bolivians have just begun a pilot mining project.  Revenue accrued from lithium production will help lift the country out of poverty.

Latin America and China

Latin America and China have a special bond when it comes to lithium.  While China does have reserves of lithium in Qinghai and Tibet, the growth of the hybrid and electrical vehicle markets will dwarf the current global production $ ($an electric automobile uses a quantity of lithium equivalent to 700 cell phones$ )$.  Latin America, especially Chile, Argentina and Bolivia may hold a key.

China is the world’s largest auto market but the country lags the United States and Europe in technology for gas-powered vehicles.  As a result, Chinese leaders are now focusing on electric cars.  They plan to turn China into one of the leading global producers of hybrid and all-electric vehicles in the next few years.

A photograph showing one of BYD China electric car models.A clear winner could be BYD, a firm relatively unknown outside of China.  BYD is the world’s 2nd largest cell phone Li-ion battery manufacturer.  In 2008, it received $230 million for a 10% stake from Warren Buffett’s MidAmerican Energy Holdings.  David Sokol, Chairman of MidAmerican, said he thought that BYD’s technology was a “potential game changer if we’re serious about reducing carbon-dioxide emissions.”

The “road to riches” in the 21st Century may be paved with a different kind of gold – a silvery metal, known as lithium.

 

And as fate would have it, this road to riches may also inexorably bind two regions of the world that have a lot to gain from each other…