Folks: Happy New Year to all.
As I was off on my merry vacation, I noticed that the popularity of this blog had doubled! And everyone seemed to be reading the post by Marca Doeff, our guest blogger. After a few weeks of soothing by battered ego, I decided that one data point does not a trend make. So we are trying to get another data point today with Marca's next post. enjoy
Venkat
It’s Marca again, enjoying her highly lucrative new career as substitute blogger for TWIB! What should I do with all the money I rake in from this gig? Buy a Tesla? Hmmm, maybe a new BMW i8-they sure are pretty, aren’t they? Should I get a blue one or a silver one? Decisions, decisions! [Editor: Dream on. Get to the point, will you?]
As I was off on my merry vacation, I noticed that the popularity of this blog had doubled! And everyone seemed to be reading the post by Marca Doeff, our guest blogger. After a few weeks of soothing by battered ego, I decided that one data point does not a trend make. So we are trying to get another data point today with Marca's next post. enjoy
Venkat
It’s Marca again, enjoying her highly lucrative new career as substitute blogger for TWIB! What should I do with all the money I rake in from this gig? Buy a Tesla? Hmmm, maybe a new BMW i8-they sure are pretty, aren’t they? Should I get a blue one or a silver one? Decisions, decisions! [Editor: Dream on. Get to the point, will you?]
Ahem, well, okay. When last we left off, I was describing the
concept of intercalation as it applies to batteries; i.e., when lithium ions insert
into electrode materials. What I didn’t get around to saying is that lots of
other things beside lithium ions can be intercalated into host structures-not
only cations but also neutral species like molecules or polymer chains, and
even sometimes anions (although, as far as I know, oxidative intercalation of
anions only happens with graphite or disordered carbons with graphitic domains).
Even before the lithium-ion battery was officially A Thing, people were having
all sorts of fun sticking stuff between the layers of clays or graphite to make
new materials with interesting properties (I even tried my hand at it Back In The Day). For
the nerds among you (you know who you are!), there’s a classic paper by Mildred
Dresselhaus (The
Queen of Carbon Science!) called Intercalation Compounds of Graphite[1],
which will tell you just about everything you need to know.
But I digress! At this point, you,
my faithful readers (both of you), are probably tapping your feet impatiently
saying something like “Well, if intercalation isn’t just limited to lithium
ions, couldn’t we base a dual-intercalation battery on something else, like
maybe SODIUM?” Very good! You all get gold stars, my nerdy blog-reading
friends!
The sodium-ion battery or NIB, is a
subject near and dear to my heart. You see, back when dinosaurs roamed the
earth, in the early 90’s, when lithium-ion batteries were just getting
started, I was playing around with this concept in the lab. Stan
Whittingham had described not only reversible lithium insertion, but sodium
insertion as well in his early papers on TiS2. Scientists like Keld
West in Copenhagen, and T. Richard Jow at the U.S. Army Research Lab were also
publishing work describing some intercalation compounds as possible cathodes
for sodium-based batteries. So, I wasn’t necessarily the very first person to work
on sodium intercalation, but I was definitely an early adopter.
The mad rush by the research
community towards lithium-ion batteries at that time left me practically all by
my lonesome to work on NIBs instead. (What can I say? Either I’ve always been
ahead of my time or I’m hopelessly out of touch, I still haven’t figured out
which). While NIBs, in principle, operate much like lithium-ion batteries, there
are some differences. One is that sodium doesn’t really insert into graphite
(the favorite anode material for lithium-ion batteries), for reasons that are
too complicated to go into here (read Millie’s paper if you want to find out
why!). There is some reversible redox activity with disordered carbons, though,
and I published an early paper on that. I also had a lot of fun working on some
cathode materials, and even patented one with the nominal composition Na0.44MnO2.
It has a very robust and cool-looking tunnel structure, which cycles sodium
ions in and out very well-and lithium ions, too, if you ion exchange it and put
it in a lithium cell.
Tunnel structure of
Na0.44MnO2, a cathode material for sodium-ion batteries.
The excitement around lithium-ion
batteries soon swallowed me up along with practically everyone else in the
battery world. Almost nothing happened for more than twenty years in NIB
research. Then, starting a few years ago, the field started heating up again.
Web of Science search
for papers containing the words “sodium ion battery”.
What happened around 2012? Well, for one thing, lithium-ion batteries
had matured and material scientists were looking around for something new to
do. The battery community was talking a lot about “Beyond Lithium Ion” (which
really meant taking a new look at some old chemistries!) And there were
screaming headlines like this one:
New York Times,
Monday February 2, 2009.
Now, are we really going to run out
of lithium? Not likely, at least not in the long run. But when you read that
the Tesla
Gigafactory is projected to need almost half the world’s current annual
production of lithium hydroxide, you gotta wonder if there might be problems
with the supply chain, at least temporarily. It takes time to ramp up
production, after all. It might be wise to have a “Plan B” battery-wise, and
there’s tons more sodium in the world than lithium, TONS. It’s a lot cheaper,
too, plus there are some other cost-saving benefits to sodium systems, like the
fact that you can replace copper current collectors on the anode side with
aluminum because sodium doesn’t alloy with aluminum, whereas lithium does.
Because NIBs are so close
conceptually to lithium-ion batteries, the development time should be shorter
than that of other “Beyond Lithium Ion” systems. We can simply leverage all the
engineering knowledge from the past twenty-five years work on lithium-ion
batteries. All these considerations got some people excited enough to start
companies based on NIBs, like Jerry Barker at Faradion. He’s targeting e-bikes. Then
there is Jay Whitacre, founder of Aquion.
Now there’s a unique concept-a sodium ion battery using an aqueous electrolyte,
for grid storage! That system is potentially incredibly cheap, which is especially
important for that application. One of the cathode materials that Aquion uses
is my old friend, Na0.44MnO2.
All this new NIB activity means that my old sodium-ion
battery papers, which languished for many years, have started heaping up
citations, sort of like Sleeping
Beauty. Sadly, I have to be contented with fame, not fortune, because the
patents expired some time ago. But that’s okay, since I’m raking in the big
bucks here at TWIB instead!
Marca Doeff
