This is Geology Bites with Oliver Strumpel.
Electric batteries play a central role in our transition
away from fossil fuels. First, we need shipping
container sized grid scale batteries to even out the peaks
and troughs of renewable energy sources such as solar and wind,
and match the supply of electricity to demand even when
the sun is not shining and the wind is not blowing.
Second, we need batteries for electric vehicles, which we're
now producing at a rate of about 15,000,000 a year.
The batteries that make all this possible are lithium ion
batteries, so-called because they store energy by moving
lithium ions between the batteries electrodes during
charge from the cathode to the anode and during discharge from
the anode back to the cathode. But in addition to lithium, four
other metals are critical ingredients of modern lithium
ion batteries, copper, nickel, cobalt, and manganese.
Where do we find these metals, and what geological processes
concentrate them into economically significant
deposits? Adam Simon studies the chemical
and physical processes that affect the mobility of elements
in geological systems and is especially interested in how
mineral deposits form. He is a professor of economic
geology at the University of Michigan.
Adam Simon, welcome to Geology. Bytes.
Thank you, Oliver. Batteries have 4 main
components, the anode, the cathode, the electrolyte in
which they are must, and a separator to separate the anode
from the cathode. I said that lithium is in the
electrolyte, but where are the other four critical metals
needed? It's the cathode that is
important and that's the focus of our discussion today because
there are different types of cathodes.
Each is composed of different types of metal.
Lithium cobalt oxide cathodes, Lithium manganese oxide
cathodes. The metals that are used to make
the cathodes play a role in how much energy the battery can
store and how quickly the battery can give up that energy
to our devices. So the nickel, cobalt and
manganese are ingredients of the cathode, yes.
OK, let's start by talking about the role that lithium and the
other 4 metals actually play during the battery's operation.
Singly charged lithium Li plus is the ion that travels back and
forth between the electrodes during the charge discharge
cycle. Why do we use lithium ions?
Lithium is the lightest solid metal in nature.
It has three protons and three electrons.
Two of these electrons are held very tightly to the nucleus.
But lithium is happy to give up this third electron and become a
positively charged ion. And we refer to this tendency
for lithium to give up this third electron as saying that it
has a very high electrochemical potential.
That, combined with its lightweight, means that lithium
can store a lot of energy in a very small mass, and that's what
makes it ideal for batteries. And the copper, is it playing
the role of a good conductor on one of the electrodes?
Absolutely. So copper is an excellent
electrical conductor, second only to silver.
And copper is also very resistant to oxidation.
So we refer to the copper foil in the battery as a current
collector. It's fused to the graphite anode
and it provides a highly conductive pathway for electrons
to travel from the graphite anode to the external circuit.
And this is the electricity that flows within the battery during
discharging, that powers our devices.
And then in reverse, it's the electricity that we add to the
battery when we recharge the battery.
And there's a lot of copper in lithium ion batteries.
The average electric vehicle, if we sum all of the copper in the
battery, it's about 20 kilograms of copper.
And that's just the copper in the battery, not the copper in
the motor and the wiring systems, which of course is a
lot. More copper.
OK, let's talk about the other three metals, nickel, cobalt and
manganese. What role do they play when the
battery is being used? Nickel provides a very high
energy density that has to do with the oxidation reduction
processes of nickel within the cathode.
So within the cathode, nickel is bonded with oxygen and when a
battery is discharged and charged, electrons are moving
into and out of the cathode. And that is facilitated by
nickel moving back and forth from 1 oxidation state to
another. And nickel's ability to do that
allows it to store a lot of energy in the form of that
electron transfer. What about cobalt?
So cobalt also provides very high energy density and Cobalt's
electronic structure, meaning its ability to give up and to
receive electrons during discharging and charging, allows
for batteries to be charged very rapidly and for batteries to
have very good thermal stability.
Most batteries today, depending on the ratio of nickel to
cobalt, have somewhere on the order of 8kg of cobalt.
So does the cobalt function in conjunction with the nickel in
the cathode, or are they involved with two separate
processes that coexist? Cobalt, when it is bonded with
nickel and manganese in a battery, what we call an NMCA,
nickel, manganese, cobalt battery, the cobalt atoms as
well as the nickel atoms and the manganese atoms are gaining and
losing electrons during discharge and charge.
And so cobalt, similar to what we described for nickel, its
ability to gain electrons and lose electrons, that allows the
cathode that contains cobalt to store a lot of that energy.
Is there a similar story then with the manganese that you have
in a cathode? Exactly.
So manganese is used because it improves a battery's resistance
to overheating during charging and discharging.
And your listeners may have heard about thermal runaway or
lithium ion batteries that can catch fire.
So what happens during thermal runaway is there's a short
circuit that occurs within the battery that can result in
melting the battery and possibly causing the battery to catch
fire. And This is why batteries in a
lot of technologies, for example in laptops, have fans that
remove the heat generated during charging and discharging of the
batteries. And is it the manganese then
that is really the determinant of the maximum safe charging
rate for a battery? So the maximum safe charging
rate will vary according to the metals that are used in the
cathode. So in a nickel, manganese,
cobalt battery, manganese plays a role.
But in each battery, even cobalt free batteries, they have their
own charge discharge rate and that's dictated by the metal
composition of the cathode. We should mention that graphite
is also needed for a lithium ion battery.
Correct. Graphite.
It's a crystalline form of carbon.
It has a perfectly ordered layered crystal structure, which
means that all of the carbon atoms are very strongly bonded
to each other within the sheets and weakly bonded between the
sheets. And this allows lithium ions to
easily move into and between the sheets of graphite in a process
that's referred to as intercalation.
And when we charge our battery, lithium ions move in between
these sheets of graphite. They pull an electron from the
circuit. So the electron flows from the
circuit through the copper, through the graphite to lithium
ions, where the lithium ions then are reduced from a lithium
1 plus to lithium metal. And graphite holds those lithium
ions until we open the circuit to use the energy, and then
graphite allows the lithium ions to move out of those sheets.
OK. Let's move on to the mineralogy
and geological origin of the battery critical metals,
starting with lithium. Where does it come from and what
processes concentrate it and bring it to the surface so?
Lithium supply is dominated by production from 2 very different
types of lithium deposits. One we refer to as lithium
pigmatites and the second lithium bronze.
I'll talk about lithium pigmatites first, where lithium
occurs as a mineral called spodumene, and spodumene is a
mineral that contains lithium and aluminum and silicon bonded
to oxygen. Now pegmatites are igneous rocks
of generally granitic composition, and in some of the
pegmatites that we mine, lithium from spodumene crystals can be
on the order of a meter in length or greater.
Pegmatites form at the margins of granitic magma intrusions,
and they appear to be the very last stages of the magma to
crystallize. There's one group of pegmatites
that are really important for lithium and they're called the
Lithium cesium Tantalum group pegmatite.
They represent about 25% of all of the known lithium resources.
Lithium rich pegmatites form from highly fractionated water
rich silicate melts and it's thought that multiple stages of
melting of Earth's crust are required to concentrate lithium
to high enough concentrations for the mineral spodumene to
crystallize during sort of the last gasp of the magma.
In these systems, economic pegmatites contain as much as 2%
lithium and we find them around the world, Australia, China,
Zimbabwe, Portugal, Brazil, Canada, Russia, the United
States and other countries. The largest deposits in the
world are found in Australia. In fact, Australia have five of
the top ten largest producing lithium mines in the world and
all five of these are lithium pegmatites in the greenstone
belts of WA. The second type of lithium
deposit that's important are lithium brines and you can think
of lithium brine deposits as really large volumes of salty
groundwater enriched in lithium. And we find lithium brine
deposits in dry inland lake beds known as playas or solars, and
these formed by the evaporation of freshwater.
So when freshwater in solars and playas evaporates, it tends to
add elements such as lithium to the groundwaters, which is
opposite of what we find in the oceans where the evaporation of
ocean water doesn't lead to the formation of lithium rich
brines. The most economically important
lithium brines in the world form in arid regions in what we call
the Lithium Triangle in Bolivia, Chile and Argentina.
These lithium reserves are just enormous.
They're about 10 times greater than all of the lithium
pigmatites in Australia. There are other lithium brines
around the world. There are lithium brines in the
Clayton Valley in Nevada in the western United States, the
Salton Sea in California, Zabui Lake on the Tibetan Plateau in
China. And then there are some new
lithium resources that are being developed.
Among them there are some clay hosted lithium deposits in
Nevada, where lithium is hosted in sediments in ryolitic
calderas. And after these calderas erupt,
all of the ryolitic material inside the caldera gets
weathered by rain that falls on and percolates down through
these rocks to convert them into clay.
There's a lot of research being done now to try and extract
lithium from geothermal waters and oilfield brines, and this is
commonly talked about in the news as direct lithium
extraction. So pumping groundwater up,
pulling out the lithium, and then pumping the groundwater
down. So there's effectively no impact
on the local environment other than to remove the lithium.
In these lithium brines, what's the origin of the lithium in the
1st place? Is it leached out of deposits
that contain spodumene? That lithium is dissolved from
all of the rock formations that host the salty groundwater.
So on geologic time scales, salty groundwater is really
effective at dissolving minerals in the rocks through which it
flows, and lithium is very soluble when there's chlorine in
the water. And then the concentration
happens through evaporation on the surface.
Correct. In the Lithium Triangle in South
America, the lithium brines. They're pumped to the surface
and then put into pools, and as the water evaporates under the
intense sunlight in the Atacama Desert, that concentrates
lithium, which will precipitate out of the brine as either a
lithium hydroxide or a lithium carbonate mineral.
I remember when I flew up from Santiago to Kalama in the north
of Chile and I saw out the window these huge green ponds.
I suppose these must have been lithium evaporation ponds.
Absolutely, Yeah, you see those. That's a great flight.
One of the concerns about the method of evaporation to
concentrate lithium in that area is the amount of groundwater
that is effectively then lost to the atmosphere through
evaporation. And this has stimulated a lot of
research and development in direct lithium extraction.
So if we can imagine putting pipes down into this lithium
rich groundwater and piping that water to the surface and then
just selectively pulling the lithium out, we can pump that
water back down underground and that then reduces the impact on
the environment. OK, let's move on to copper.
We've been mining copper for a very long time, so presumably
the sources of copper are pretty well established.
So there are several important types of copper deposits.
The most important are what we call porphyry copper deposits
that supply about 60% of the world's copper, followed by
sediment hosted copper deposits. And then there are three other
deposits, magmatic sulfide deposits, iron oxide, copper
gold deposits and volcanogenic massive sulfide deposits.
But I'll start by describing porphyry deposits.
So the word porphyry refers to the porphyritic texture of
igneous rocks that host the copper minerals in these
deposits. And a porphyritic rock is a
mixture of large crystals which we call phenocrysts, and small
crystals that we call ground mass.
Is the copper in the big crystals or within the matrix?
In the matrix, in very thin veins within the matrix, the
most important porphyry copper deposits are found at convergent
tectonic margins above active subduction zones.
So places such as the Andes in South America, or the very
volcanically active areas of Indonesia and the Philippines,
Alaska and the western United States, places like Arizona and
Utah, porphyry deposits form from magmas in volcanic systems.
Magmas are composed of a liquid which is a silicate rich melt,
and the silicate rich melt contains copper and every other
metal and element in the periodic table, plus solid
minerals inside the magma and then gases, carbon dioxide and
water that are dissolved in the melt.
And as a magma is moving from deep within Earth's crust
towards the surface, all of these gases are dissolved in the
melt in subduction zones. So imagine the Andes of South
America where we've got the Pacific Ocean plate moving from
West to east and the very large South American plate moving from
east to West. That compression can cause the
crust in South America to get really thick, 30405060
kilometers thick. And in really thick crust in
seduction zone environments, the magmas get progressively more
silica rich and they get more water rich.
We refer to these types of magmas as granitic, the same
types of granites I mentioned earlier that evolved lithium
pigmatites. Now what's important about the
granitic magmas is they have a very high silica content, which
increases the viscosity of the magma.
So think about these magmas as you know, something like frozen
peanut butter. It's really hard for them to
move. But eventually, when these
magmas get close to the surface of the Earth, the melt part of
the magma can no longer keep water dissolved in the melt, and
so that water dissolves from the melt to form bubbles.
And you can picture these bubbles as bubbles in a glass of
champagne. These bubbles are dominantly
water. But elements like copper and
sulfur and chlorine also really prefer to be in these bubbles
versus the melt. So copper and sulfur will
partition or transfer from the melt into the bubbles.
Now in the magma, these bubbles that contain copper and sulphur,
they're really buoyant and they ascend towards the surface of
the magma. And when they get to the surface
of the magma, unlike our glass of champagne where the bubbles
can just pop, in a magma, the bubbles will pond.
And at the top of the magma chamber we get this coalescence
of trillions of bubbles that form this layer of very copper
rich, sulphur rich liquid. And eventually those bubbles can
exert a lot of pressure outward on the magma and they can cause
an eruption. And this is the eruption that
you see if you pop the cork on champagne.
And all of that gas in the liquid immediately wants to get
out to the atmosphere. The same thing happens to form
porphy deposits where these copper and sulfur rich bubbles
erupt from the magma. But they're erupting at a
kilometer, 2 kilometers, 3 kilometers below the surface.
And as soon as they erupt, they wiggle their way towards the
surface, through all of the rock above the magma chamber.
They're cooling off, they're decompressing, and they're also
reacting with all of the rocks through which they flow.
And this results in the almost instantaneous precipitation of
minerals that are enriched in copper.
And all of this happens in a really small volume of the
Earth's crust and results in the formation of porphyry copper
deposits. OK, let's move on and talk about
nickel. What's its geological origin and
the context in which we find it? We get nickel from 2 main types
of deposit laterites and sulfide deposits.
Laterites today supply about half of the world's nickel, and
they're forecasted to supply about 80% of nickel within the
next decade. Most of our nickel from
laterites comes from Indonesia, New Caledonia and the
Philippines. These are areas that contain
huge amounts of ultra mafic rocks like perititite and donite
that are really rich in magnesium in the mineral
olivine. These ultra mafic rocks can
contain as much as several thousand parts per million
nickel in olivine where nickel substitutes for magnesium.
Olivine in these rocks on the surface of the earth is really
thermodynamically unhappy. As warm rainwater percolates
down through the ultra mafic rock, it reacts with and breaks
down olivine and this releases the magnesium and the nickel and
the iron in the olivine to the groundwater.
And as soon as this happens, if the groundwater contains
dissolved oxygen, iron immediately precipitates as an
iron oxide that adsorbs nickel from the water and it results in
the concentration of nickel in very thin zones within these
ultra mafic rocks. If the groundwater is reduced,
then nickel can remain dissolved in the groundwater and it will
percolate down to the bottom of the weathered zone where it can
precipitate as minerals like garnierite, which is a really
complex nickel silicate mineral and again precipitates in a very
thin layer from which we can mine the nickel.
OK. We hear a lot about cobalt
because it mainly comes from the Democratic Republic of Congo,
which is problematic because of child labor and other issues.
What is the geological origin of the cobalt?
So in the Democratic Republic of Congo and other areas, cobalt is
associated with copper and these deposits are referred to as
sediment hosted copper, cobalt deposits.
And they contain copper and cobalt in the form of copper
oxides and cobalt oxides and copper and cobalt sulfide
minerals. And they're found concentrated
in layers in sedimentary rocks. We find them in the African
Copper Belt, which extends from Angola across the Democratic
Republic of the Congo into Zambia, and also in the Cooper
Schieffer in Germany and Poland. In fact, the word Cooper
Schieffer means copper shale and people have been mining copper
in this area for at least 1000 years.
Do we know what the geological origin of that very large
African copper belt is and how it came to be enriched in copper
and other metals? So that area in the geologic
past contained really expansive shallow continental and marine
sedimentary basins, if we think about the Gulf of Mexico or the
Mediterranean Sea as a modern analog.
So we've got the deposition of muds and silts and sands to form
really thick sequences of mud stones and sand stones and silt
stones. And it's within those sand
stones that the salty groundwater is first birthed,
probably from the dissolution of evaporites after all of the
water has evaporated and precipitated salts at the bottom
of these basins. So the general model for how
these deposits form in the African copper belt involves the
movement of oxidized copper bearing salty hydrothermal
fluids. So think salty groundwater
similar to what we talked about for lithium, but in this case
the salty groundwater is able to dissolve high concentrations of
copper and cobalt. And as long as the groundwater
is percolating through rocks that are oxidized, so think
oxidized sandstones or red beds, then the copper and cobalt are
perfectly happy to be dissolved in that salty groundwater.
But if that salty groundwater encounters rocks that are very
reduced, so rocks such as shales or mud stones, silt stones that
contain high concentrations of carbon and sulphur, then the
sulphur in these reduced rocks will reduce the cobalt and
copper groundwater flowing through the oxidized rocks.
And at the interface between the reduced and oxidized rocks, the
sulphur in the reduced rocks will react with copper and
cobalt in the oxidized groundwater to precipitate
sulphides that are enriched in copper and cobalt.
And this happens in relatively localized volumes of sheet like
or lens like ore bodies that forms very high concentrations
of copper and cobalt in small volumes of rock in the African
copper belt over geologic time, the upper few 10s of meters to
maybe 100 meters of these deposits.
As rainwater has percolated from the surface down through these
rocks, it oxidized the cobalt sulphide minerals to cobalt
oxide minerals. And that makes the cobalt much
more attractive economically to mine because it's easier to
process and produce cobalt from an oxide mineral than it is a
sulphide mineral. The 2nd place we get cobalt are
from the nickel rich laterites that we talked about.
So these nickel rich laterites also contain relatively high
concentration of cobalt on the order of a few 100 to a few
thousand parts per million cobalt and cobalt is produced as
a byproduct of nickel mining from these regions.
The last critical metal is manganese.
Can you tell us about the origin of the manganese deposits?
Most of our manganese comes from sedimentary deposits that
precipitated from sea water during sea water evaporation.
So again, thinking about modern day basins like the
Mediterranean Sea, if we imagine the Mediterranean Sea
evaporating on geologic time scales under the right
conditions within the water, manganese will precipitate out
of that water to form manganese minerals.
These sedimentary manganese deposits supply most of the
world production and they consist of layers of manganese
carbonates and oxides that were precipitated as these chemical
sediments. We find manganese deposits on
Earth that formed both before the great oxidation event, so
about 2 1/2 billion years ago when the Earth's atmosphere went
from having very low concentration of oxygen to
gradually the much higher concentration of oxygen we have
today. And manganese deposits that
formed before the great oxidation event, they're
dominated by manganese 2 plus minerals.
So manganese bearing carbonates and manganese deposits that
formed after the great oxidation event tend to be dominated by
manganese 3 plus and four plus in oxides and hydroxides.
And we very commonly find these oxidized manganese deposits
associated with banded iron formations where iron in the
world's oceans precipitated as iron 2 plus and three plus in
minerals like hematite and magnetite.
So it sounds like when you think about it globally, that we have
a pretty abundant supply of all these critical metals, albeit
some of them beset by geopolitical problems, but it
doesn't sound like we'll be running out of any of them soon.
No, we have more than enough of each of these metals to build
the batteries that the energy transition requires.
It's the batteries for the energy transition from
combustion engines to battery electric vehicles.
It's also the energy transition for a majority of people around
the world to transition from very low energy to what we think
of as normal amounts of energy consumption in the European
Union, the United States and other countries.
So we know we have enough of these metals around the world.
The challenge is the rate at which mining companies can
extract them to make them available for manufacturing the
batteries and other technologies.
All the five metals we've talked about likely to remain critical
for batteries, or do you think new technologies will reduce our
need for them or create a demand for other elements?
I think the general consensus is that these metals will be the
most important for electrification and energy
storage for at least the next few decades.
Research and development now is focused on increasing energy
density, which is really important for battery electric
vehicles. Increasing power density.
So how much energy can a battery provide per instant of time?
Increasing the charging rate so allowing batteries to be
recharged much faster than they are today.
Lots of research and development on increasing battery lifespan
and increasing the cycle life of a battery.
So when we buy a phone today, it's designed for us to charge
and discharge it somewhere on the order of 506 hundred times.
Well, why can't we have phones where we can discharge and
recharge the battery 1000 * 5000 times?
Also trying to continue to reduce battery costs.
Battery costs have dropped 99% in the last 30 years.
But can we continue to make batteries cheaper while also
making them better and making them safer?
There's a lot of research being done on solid-state batteries.
So instead of having a liquid electrolyte, having a solid
electrolyte, they could be a ceramic and also replacing the
graphite anode with other anodes, graphite combined with
silicon, possibly silicon anodes, and even using lithium
metal as an anode. So I think over the next few
decades, the metals that we've talked about here will continue
to dominate batteries. But over the next few decades,
we'll see the composition of the cathodes will change.
We'll see. All of the positive factors of
batteries just continue to get better.
So what are you working on at the moment in your research?
So among all the metals in the periodic table, my favorite has
always been copper. Copper is the metal that is most
fundamental to all technologies. So we can play around with the
ratio of nickel to cobalt in batteries.
We can reduce just a bit the amount of copper that we need,
but we need copper to generate electricity, to move
electricity, to store electricity.
And the amount of copper that society will need over the next
few decades for the energy transition is more than the
amount of copper we have mined since the end of the Stone Age.
So where is all this copper going to come from?
Mining companies are discovering less and less new copper.
So I focus on trying to understand how do we search for
and discover new copper deposits?
And how do you do that? So with a couple of partners, we
looked at waters that move through natural copper deposits,
groundwater and surface water, and we started analyzing the
composition of waters from around the areas of known copper
deposits all over the world. And when we analyze water
samples, we measure everything from lithium to uranium, so
every metal in the periodic table and we measure all of the
metal abundances, plus we measure the isotopic abundances.
And then we use those data to figure out what is the metal
isotopic signature of groundwater and surface water
that is a fingerprint for that water having interacted with
copper minerals in the subsurface.
And we figured out what that fingerprint is.
So we're applying our technology to help mining companies screen
areas around the world for the presence or absence of copper
minerals. So all we need is a few 100
milliliters of water. And that water can come from any
natural source, from a spring, from a seep, from a small lake
or pond. We've even sampled water from
the Zambezi River, and we can tell you whether or not it
fingerprints the presence of copper minerals.
Adam Simon, thank you very much. Well, thank you, Oliver.
I really appreciated this opportunity to chat with you
about batteries and the metals that we need to make them.
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