Sunday, September 11, 2016

Why are Note 7 batteries exploding?

Samsung Galaxy Note 7’s are exploding when they are charged.  The tech media is, rightly, trying to get to the bottom of this. 

Much has been said about how this can happen and the focus appears to be on overcharging Li-ion batteries and the resulting heat generation.  The only party that actually knows something about this is Samsung and they have said that there was a “minor flaw in the battery manufacturing process”. 

This does NOT sound like an overcharging problem.  This could be either misalignment of electrodes leading to lithium plating and shorting.  Or something like copper dissolution and subsequent deposition leading to shorts. 

Or something else. 

But more importantly, except for Samsung, we are all guessing.  As long as Samsung does not tell us (and I’ll go on a limb and say that they will not), we can make up anything we want.  But guess what: we are making stuff up!  We should probably stop. 

But where is the fun in that.  So let the speculation continue. 

Interestingly, the Chinese made batteries by ATL are not exploding.  Only the Samsung made ones are. So much for "low quality Chinese manufacturing"…


Monday, February 1, 2016

A Bolt (with a B not a V) from the Blue

From time to time, I have been known to get all excited trying to explain to my 3-year old that he is living in an amazing time.  Self-driving cars, hoverboards, home automation, robot assistants… the list of amazing changes goes on and on.  He, in turn, has been known to give me the “leave me the @$%#$ alone” look while he gets back to being amazed at the number of ABCD songs on YouTube. 

Apparently, both my son and I are wrong to be amazed. Atleast this is what I learnt when I read reviews of a new book titled “The rise and fall of American growth” by Robert Gordon.  His TED talk argues that the pace of technological innovation in the last 50 years is far lower than the period in the first half of the 20th century.  Unlimited ABCD is all nice, but from an economic growth perspective, apparently not as big a deal as indoor plumbing (my 3-year old just asked me to use said indoor plumbing to evict myself from the house when I pointed out to him that he is doing nothing of economic value to society).

I am no economist.  But I do know a little something about batteries.  And I have been known to say stuff like “there is nothing new in batteries” every time a paper comes out claiming a breakthrough.  I was mostly right for a decade.  Over the last 2 years, I have stopped saying that and have gotten to be amazed at the changes in the battery world.

No. No.  I’m not talking about the press releases claiming breakthrough.  Those are still not worth the bytes they are written on.  I’m talking about real changes, like the dropping prices for Li-ion batteries. 

Or the fact that I have stopped counting the number of EVs I see in my (rather long) daily commute.  From Nissan’s to BMW’s to Merc’s to Tesla’s, they are pretty much part of the landscape.  Granted, I do live in a bubble (the Northern CA area is not exactly representative of the world-at-large), but it is fascinating to see the penetration of these cars.

But as a low-paid National Lab scientist with a long commute, I have been unable to make the jump.  Either these cars had very little range (Berkeley, for all its greenness, does not excel at providing charging) or cost too much.  And gushing over a car at the dealership does not lead to a price reduction.  Quite the opposite!

But prepare to be amazed even more. 

Chevy recently announced the 200 mile Chevy Bolt (not the same as the Volt.  They really should start calling the car “Chevy Bolt: with a B not a V”).   Available sometime next year, it will be a small to mid -sized 5 passenger crossover with reasonable trunk space.  And Tesla is said to be ready to announce the Model 3, another 200 mile “less frills” car for the rest of us.

Both the Bolt and the Model 3 are going to be in the mid to high $30k range.  With the tax rebates, we are talking under $30k.  Even I may be able to afford that!  And 200 miles may be enough to remove range anxiety for most of us. 

And, with all the auto companies starting to agree on putting the battery at the bottom, space for passengers and for the Costco runs appears to be in the offing. 

Now, 200 miles is no 350 or 400 miles (typical gasoline car range).  Nor is the price comparable to gas cars (I suspect that a gas equivalent of Bolt is probably a $20k car), and tax incentives are probably not to be depended on in the long run, but these $35k/200 mile EVs are going to be a game changer. 

And more automakers are promising to go after the 200-mile target.  There is a feeling that this is the sweet spot for the next push for electrification.   With falling Li-ion prices, these cars are going to get cheaper year after year.  I do think leasing is probably a better idea considering the rapid pace of changes, not just in batteries, but also in the level of sophistication in the cars.

Granted that there is probably little economic growth in going EV (I suppose you are substituting from one production type to the other. And some of the battery cost reduction is coming from automation), but you have to admit that from a pure technological standpoint it will be good to have something new for a change on the roads after a century of the same kind of drivetrain. 

Combine the EV revolution with ubiquitous connectivity and self-driving technology, we are going to have a LOT of time on our hands to think about doing something of economic value in the silent cone that is our battery-powered Uber.  And nothing like boredom to invent something new to keep ourselves from getting bored.  After all, isn’t necessity the mother of all inventions?  Hopefully what we invent will be of economic value so that we can prove Robert Gordon wrong.

In the meantime, continue to be amazed at the changes you see on the roads.  When my 3 year old went through a (mandatory?) car identification phase he has been known to say stuff like “Too many Toyota’s”.  Before long, if the trend continues, I think he will be saying “Too many Tesla’s”. 


Tuesday, January 12, 2016

Back by Popular Demand-More Intercalation Chemistry, This Time with Sodium!

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


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

[1] Advances in Physics, 2002, Vol. 51, No. 1, 1-186

Tuesday, December 8, 2015

A Brief History of Cathodes or, Thinking Positively about Li-ion Batteries

Guest post by Marca Doeff

While Venkat is off trekking the Himalayas, fighting space aliens, solving world hunger, fixing his Roomba, on a well-deserved vacation, he has asked me, (moi, Marca Doeff, world famous battery scientist, lowly lab rat), to whip up a light and fluffy something to feed the blog. “Fine”, I said, “should I talk about my cats or the movie I saw last week?” Judging from his response, that’s not what he had in mind (wow, I didn’t know there were so many cuss words in Tamil!). Instead I concocted this little history of cathodes for lithium-ion batteries, complete with pictures (if you want cat stories, you’re going to have to look elsewhere on the internets).
            It all started around the mid 70’s or so, when Stan Whittingham at Exxon announced his newly discovered phenomenon of lithium ion intercalation into TiS2, in a letter to the journal Science. It turns out that TiS2, which has the layered structure shown below, could be reduced electrochemically while simultaneously inserting lithium ions between the layers. Better yet, this process was entirely reversible! Everyone in those days was interested in making a secondary battery with a lithium metal anode work. That announcement set off a race in research labs everywhere to look for other intercalation compounds.

The layered structure of TiS2.

In 1980, John Goodenough, who was then at Oxford, wrote a paper in the Materials Research Bulletin describing another layered compound, LiCoO2 or LCO. This one was made with lithium already in the structure, so it had to be charged up before you could use it in a battery. The battery companies at the time didn’t like this, so they said “Goodenough, it’s not good enough!” (haha, be kind to me, it’s lonely in the lab.) LCO also was pretty oxidizing once you started taking the lithium ions out, and the electrolytes of the day just couldn’t handle it. The last laugh was on the battery companies that dissed John Goodenough, though, because just a few years later, someone figured out how to make a graphite anode work, and the lithium-ion battery was born, and then commercialized by Sony in 1991. Having lithium in the cathode structure for that configuration turned out to be just what was needed, so that you could assemble the cell in the discharged state and then charge it up. Moreover, by that time, there were better electrolytes that didn’t fall apart so readily. The higher potential at which LCO operated compared to TiS2 was an asset, not a liability, since it meant higher energy densities in cells. Batteries with TiS2 and the problematic lithium anode were out, and Li-ion batteries with LiCoO2 cathodes and graphite anodes were in!
             The layered structure of LCO.  The yellow spheres represent lithium ions.

            End of story? No, that was really just the beginning. Cobalt is awfully expensive and somewhat scarce. Everyone wanted a cathode that was cheaper with more abundant elements in it, like iron or manganese or nickel. People like Jeff Dahn in Canada, Claude Delmas in France, and Tom Ohzuku in Japan started looking at other layered compounds with various combinations of nickel and cobalt and manganese in them and sometimes a soupçon of aluminum or magnesium. They and many other scientists around the world fiddled around with the formulas to get the best energy density, safety, and performance. These layered compounds are often called by their initials, like NCA (nickel cobalt aluminum) and NMC (nickel manganese cobalt) and are among the most technologically important cathodes we have today.
But let’s backtrack a bit. A few years after LiCoO2 was discovered, Mike Thackeray, who was living in South Africa at the time, visited John Goodenough’s lab and started fooling around with manganese oxides. Only problem was that the compounds he was looking at weren’t layered but had spinel structures instead. Strictly speaking, they weren’t intercalation compounds, because “intercalation” really refers to the insertion of ions between layers, like leaves of a calendar (“inter”=between and “calation” is related to the word “calendar” from the Latin word “calends” for the first day of the month). Nevertheless, lithium ions could be removed from lithium manganese oxide (LiMn2O4, LMO) and inserted back in again through three-dimensional diffusional pathways in the structure. Nowadays, the use of the term “intercalation” has expanded to mean insertion of ions not only into layered structures (the original meaning) but other types of structures as well. I guess if you are a grammar prescriptivist, this shift of the language is an offense against all that is good and holy, but if you are a grammar descriptivist like I am, it’s simply a useful word to use to describe the general phenomenon of ion insertion into all kinds of structures.
 Another surprise was the olivine-structured LiFePO4 or LFP (Goodenough, again). It wasn’t even electronically conducting! Most intercalation compounds are mixed conductors; that is, both ions and electrons can move through the structure, which is necessary for them to function. A few of them start out nearly electronically insulating, but become more conductive as they undergo redox (notably, the spinel anode material Li4Ti5O12). All you have to do is get the reaction started (say, on particle surfaces) and then it can propagate. In contrast, what you get when you oxidize LiFePO4 is another nearly insulating compound, FePO4. To this day, it is somewhat of a mystery of how and why it works, and scientists spend lots of time dreaming up exotic experiments to explain its behavior and arguing over what is really happening. Hey, we have to remain employed somehow!
On the left, the spinel structure of LMO and on the right, that of the olivine LFP. The yellow spheres represent Li ions in the structures.

It turns out that lots of structures with transition metals in them can insert lithium ions, even some that are completely disordered. Of course, the majority of these materials fail on some metric or other; some of them don’t have high enough capacity or energy density, some have rare or toxic metals in them, or they do something weird like dissolve or change their voltage characteristics when they are cycled. Of the hundreds of compounds that have been studied over the past forty years, only a few have passed muster. A modified version of LCO is used in consumer electronic batteries, and, depending on manufacturer, hybrid electric, plug-in hybrid, and electric vehicle batteries contain LFP, NCA, NMC, LMO, or mixtures of the last two.

Will something better come along? It’s hard to beat what we have now, but researchers are still trying. To quote the immortal Yogi Berra, it’s tough to make predictions, especially about the future!

Marca Doeff