Cobalt blues: The Li-ion supply chain and the shackles it creates.

In recent weeks, two articles in the Washington Post laid bare the sorry state of the supply chain for Li-ion batteries; batteries that have made our phones into a device we use for everything (except calling people!); is changing the way we drive; and promises to change the way we generate and use energy. 

The first one on cobalt mining in Congo describes dangerous conditions, child labor, and exposure to toxic metals.  Cobalt is essential for cathodes for Li-ion batteries.  The second article on graphite, used as an anode in Li-ion batteries, digs into the pollution, environmental destruction, and health effects from mines in China.  Both stories are very well researched; connecting the dots from the mines, to the supply chain, all the way to the companies that use them in smart phones and electric cars.  The articles are also depressing.  They reveal a side of these devices none of us want to see.  It is like watching Food Inc.

One question that I have gotten since these articles came out is:  Can we move away from cobalt and natural graphite for Li-ion batteries?  This blog post delves into this topic. 

Why did we start using cobalt anyway?

Marca Doeff’s blog post does a fantastic job of walking us through the history of Li-ion cathode materials.  Lithium cobalt oxide, which John Goodenough discovered, started the whole Li-ion revolution.  Cobalt oxide was (and is) expensive, so variations have been found that have no cobalt in them. 

Lithium manganese oxide came along soon after, was eventually commercialized, and reached the market for power tools and in plug-in electric cars. Manganese oxide is significantly safer than cobalt oxide, but it also has far less energy density.  And consumer electronics and electric cars need highly energy dense materials, so manganese oxide is not that useful for these applications. 

Another variant is lithium iron phosphate, which has a complicated IP history.  Many of you probably heard of this chemistry when A123 first commercialized this for power tools.  It has since become pretty popular in Asia for transportation applications.  The chemistry is very safe and has fantastic cycle life.  So there is hope that we can use it as the stationary storage market evolves.  But the wonderful safety and cycle life comes at the expensive of energy density, which is pretty low compared to cobalt oxide.  Ergo, limited use for high-energy applications.

In the late 90’s the nickel variant of cobalt oxide, lithium nickel oxide appeared to be gaining traction in the consumer electronics battery world.  But nickel oxide has some safety issues and this was a cause for concern.  Instead, what became more successful were a class of cathodes where the cobalt content was lowered instead of being eliminated.  These include nickel-cobalt-aluminum (NCA) and nickel-manganese-cobalt (NMC).  There was a period in the early/mid-2000’s when these variants seemed poised to displace cobalt oxide completely, partially driven by, what at that time appeared to be, the limit of cobalt oxide. 

And then, cobalt oxide got better. 

It was long thought that cobalt-based cathodes could not be used beyond a cell voltage of 4.2 V because of reactions between the cathode and the electrolyte that lead to degradation.  Today, with surface coatings to isolate the cathode from the electrolyte, combined with larger particles, cells charge to 4.4 V or more.  Coupled with the ability to achieve high tap densities (defining tap density is a blog post in itself!), cobalt oxide has again become the highest energy density battery available.  For smartphones, laptops etc., where the battery cost is relatively small, the energy density advantage is key.  So cobalt has come back to rule the Li-ion world.

But cobalt is still expensive.  So for larger batteries such as in electric cars and for stationary storage, the lower cobalt content materials such as NCA and NMC are used.  And it is not obvious to me that the high-voltage cobalt oxide cells (operating at 4.4 V) are going to be long-life batteries.  These are probably great for the 2-year change cycle for phones; not the 10-year change cycle for cars.

Although, to digress, I have a 2 year old phone that has only lost 7% of its capacity.  How, you ask?  Because I follow these wonderful battery rules.

I summarize all this in the figure below, including the options for the anode and the electrolyte (well... there really aren't many options for electrolytes!)

 Can we move away from cobalt altogether?

Not clear.  As I said before, we do have options that have no cobalt, but these options are not very high in energy density, except for the nickel oxide material.  The nickel oxide material works well, although the synthesis requires some care.  However the safety of the material is questionable.  And as the recent incidents with the Note 7 have highlighted, one should be designing safety into every component in the battery. 

In the meantime, lowering the cobalt content is probably the logical pathway.  There is a trend in the research stage to minimize the cobalt content, in some cases to as much as 10% of the transition metal content; without scarifying energy density. Some of these materials, referred to as the lithium-rich, manganese-rich materials, show enormous promise.  And they offer the hope of eliminating cobalt.  But they also appear to have some fundamental issues that need to be solved. Work continues, at universities, national labs, and in companies to bring these to market.

In addition, one can also imagine playing the same tricks on the NMC formulation that helped cobalt oxide operate at higher voltages.  This will help increase the energy density of this material, beyond what is possible with cobalt oxide.  But these are all still in the research stage. 

In batteries, the time from lab breakthrough (real ones, not the ones that are alluded to here) to market impact takes a decade or more.  So, we may be stuck with cobalt oxide for a while.  But there is hope that we can move away from it with less cobalt and maybe, one day, with no cobalt.

But, something tells me that even if that happens, we will find out that children can still be exploited and the environment destroyed in the search for the raw materials.  The issue here is probably not cobalt.  It is something far beyond what this blog was meant to address.  

Case in point is the graphite part of the Washington Post story.  Next week I will list our options for moving away from graphite anodes. 

Venkat

Finally, we know why the Note 7 exploded.

The answer, according to the New York Times:  “Samsung seems to have packed it with so much innovation it became uncontrollable”.  Apparently phone components are like 4-year olds; put 3-4 of them in a room and they are ok, but pack 10 of them in a small place they will destroy the room with all the energy feeding off of each other.  Of all the theories, this one takes the cake. 

As much as I think the community should not be speculating on the underlying case of the explosion, I think we can’t help ourselves.  For battery types, this is the most interesting event that happened since the-last-time-there-was-a-fire, so we are all salivating.  What can I say: we don’t get out much. 

For non-battery types, I can see their need to know if more phones are going to be exploding.  Only way to know is to understand what happened with the Note 7. 

I have been getting this question steadily the past few weeks, so I thought I would collect all the speculation in one single place.  I also provide my views on this.  So here goes:

1. The battery was overcharged (BMS failure, too high an upper cut off voltage, aliens, whatever) and hence the fire.  I think the eager ones among us, who do not believe in waiting for more information, speculatively stated this.  I think Samsung’s revelation that there was a manufacturing flaw negates this theory.

2. Samsung used a 6 um separator in the battery and this lead to defects when assembling with a thin separator. This in turn led to shorts and the explosions.  As I explain below, this may be part of the story.

3. The battery had a manufacturing defect where the anode and cathode did not line up correctly, leading to edge effects, lithium plating and shorting.  This seemed very likely until the New York Times article came out. 

While these three issues are obvious ones that most battery types would guess, the New York Times articles makes the point that after initially concluding that it was the battery, Samsung realized that it was not that simple.  The article claims that Samsung could not pinpoint the reason!  Hence the wacky statement about “uncontrolled innovation”.

Let us be clear: Samsung makes great batteries. ATL makes great batteries.  If this were an obvious issue, they would have caught it after the first few weeks.  There is something to be said about the argument that this is a more complicated problem.

Since the Times article came out, we have had three more, system level, theories that have popped up.

4. The battery was being fast charged due to a chip design flaw.  Faster than it was rated for. This lead to overheating, thermal runaway, ending with you-know-what.  I’m not so sure about this.  The Note 7 phones were exploding even when not fast charged so…

5. There was so much being packed in a small volume that the battery was getting squeezed and the edges pinched, unintentionally, leading to shorts.  This theory does seem possible, but I like the theory below (which is a variant) the most. 

6. Samsung used higher content of silicon in the graphite-silicon blended anode.  The silicon expands on charge and swells the pouch.  Because the pouch was unable to swell in the phone due to the lack of space, it shorted and exploded.  I really like this theory.  There have been problems with battery swelling even before silicon came to the scene, but this has only gotten worse with silicon-graphite anodes.  Many consumer electronics companies have been worried about this and have a spec. for how much the battery can expand.  According to Mashable, the Note 7 had a 750 Wh/l battery; which is PRETTY energy dense.  Much more so than previous generations of batteries, suggesting higher silicon content than before. 

It is possible that higher silicon content combined with a thinner separator and less space in the phone for volume expansion all came together to lead to shorts and fires. 

I’m sure I’ve missed a few other theories (aliens?), but I think I got the majority of the ones I have heard.  

Now that we have that out of the way, let us talk a bit about what this all means. 

I think the initial speculation that this was a battery-level issue appears too simplistic.  Clearly, there is more to the story.  Batteries all over are safe, have been safe, and will continue to be safe.  Assuming you know what you are doing.

But what if you have “uncontrolled innovation” happen again? What is a poor battery to do if the overall system does not want to treat it kindly?  Li-ion batteries are energy storage devices.  Meaning, if you release the energy very very fast it is not going to be pretty.  So, some TLC is in order. 

But even if the system screws up how it handles the battery, shouldn’t the storage device itself be made to withstand any abuse?  As we move toward wearable technology with things attached to every part of our body, we need to ensure that the battery remains robust even if there is a system-level failure.

There has been a narrative going around that Li-ion batteries today are similar to where crystalline silicon solar cells where a decade ago: meaning, the prices are dropping and one can get installers and system integrators to come in and start to make them ubiquitous.  The Note 7 incident shows the perils of this thinking. 

Batteries are not plug and play devices where Jane-solarinstaller is going to buy something off of Alibaba and dump it in your garage and get you city permit folks to sign off as if they are inspecting your plumbing.  We better be buying from someone who knows how to make them well.  And we better know how to design the system correctly, install them well, and control them through the life of the device.

But to get the world where we do treat our batteries like we treat our microwave (bang on it to try to get it working?), we need the batteries to be robust inside out.  This requires a separate blog post, hopefully, in the near future.  

In the meantime, with the Note 7 off the streets, time for the battery folks to crawl back to the cave and focus on achieving a few breakthroughs.  Until the next incident… 

Venkat

I'll be back... in 8 hours

Some of my readers have wondered why I have been off the blogosphere in the last few months. The reason is that we brought a house and the move from the apartment to our new place has been a bit of a time sink.

First we went through the four stages of home buying:

Stage 1: What the &%#@ do you mean they accepted our bid? I thought you said we were lowballing?

Stage 2: When you use words like "downpayment", does this involve us giving you a check?

Stage 3: I assume roof's are like batteries? Meaning, when you say it is at the end of its life, there is still 80% left, right?

Stage 4: Keep repeating after me: "Owning is better than renting" and, please, stop asking "why?"!

Then we realized that owning a house also meant owning things like leaf blowers and lawn mowers! So, when I saw that there was a battery-powered lawn mower, I jumped at the chance to push my favorite technology forward.

I was looking forward to using my expertise in batteries to maintain and extend the life of my lawn mower for many years to come.

I was not particularly looking forward to mowing the lawn, but owning a battery-powered mower seemed to make up for that.

Until I realized that the top-rated battery-powered mower uses lead-acid batteries.

Lead-acid!!! really! How old school can one really get.

My first thought: Start a battery company to make Li-ion batteries for lawn mowers.

Then I started thinking about this some more. There must be a catch here. So I started digging into what it was.

Let us do some math: The battery for this lawn mower cost ~$270/kWh. That is one expensive lead-acid battery. Presumably, it is a deep-discharge battery, and so it is better made than a car battery.

And there is probably a significant markup.

Did I mention that the mower was on sale for $300! More like a mark-way-way-up.

Considering a typical Northern California growing cycle, this mower will probably be used ~50 times a year (once a week). These deep-discharge batteries can probably go a few hundred cycles. So I'm thinking 4-5 years easy.

But the bigger problem is going to be the calendar life. Sulfation can kill these cells.

Having said that, the battery is probably going to be at the top-of-charge pretty much through its life (think about it: Mown for 1 hour. Keep it plugged in all week). And remember our rule for lead-acid batteries: Keep them charged. So I think we can expect to get ~3 years from these cells.

Lets do some math for a Li-ion battery. I bought one a few weeks ago. This battery will probably last me 3 years and get me ~300 cycles or so. So it has similar specs to the lead-acid battery.

The Li-ion battery, on the other hand, cost me a whooping $2300/kWh!! No... really. This is what it cost me.

Now... knowing Apple, a new word has to be coined for their level of markup. But still this is one expensive battery.

At this price, a Li-ion lawn-mower-battery would have cost me $800!

All you MBA-types are probably cringing because you all know that cost and price are very different from each other and that the price is dictated by what the market is willing to pay (my wife is an MBA and she gave me this spiel).

Granted. So let us do a cost-differential comparison. This comes out to be ~$50/kWh more expensive for a Li-ion cell. Using this, the cost of a Li-ion battery for this mower would be higher than the lead-acid battery by... the price of lunch!

Not at Chez Panisse. But at the LBNL cafeteria (same quality, but at a much lower price?)

So why not use a Li-ion instead. After all it is almost 5x the energy density.

The mower that I have been talking about in this blog is a push mower. So the battery does not need to drag itself. All it has to do is turn the cutting blade. And space is not a big constraint. The mower's size is dictated by the size of the blade anyway.

So why bother using a new type of battery when you don't really see much of a benefit?

Frankly, although I have not looked at the life-cycle, I'll take a bet that it is probably better for the environment to use a lead-acid battery considering how much of this lead is recycled. In comparison, all you recycle in a Li-ion is the high-value metals in the cathode. The rest, literally, goes down the drain.

Maybe the math will change for a self-propelled mower. Or if the weight of the mower is an issue. But I don't see any reason to jump to using a Li-ion battery for the mower I was looking at. This business plan does not appear to have much legs.

So what did I do? I got the corded version of this mower. It cost me $100 less.

I guess the price that I'm willing to pay to push my favorite technology forward is less than $100!

In my guilt I decided to do my part for the technology by buying a Roomba.

I'm not sure if you guys know about this amazing robotic vacuum. It is pretty interesting to watch. It has sensors that make it slow down when it approaches objects, detect dirt, and prevent it from falling off of stairs.

It is not particularly good at vacuuming. But it feels like it is cleaning the floors and isn't that what's important!

But here is the kicker. The one I have has a Ni-MH battery.

I suppose I should be thankful it is not a lead-acid, but Ni-MH? COME ON!

The last time I checked, the cost of Li-ion and Ni-MH batteries were pretty comparable. And the energy density of Li-ion is 2-3x greater. And remember that in this machine (unlike the mower) the vacuum has to drag its battery along. And space is a big deal. The smaller the footprint, the smaller the space it can vacuum.

So why use a 20th century battery for a 21st century machine? Strange.

A web search revealed that Li-ion Roomba's have apparently died prematurely. If this is the case, then iRobot (the company that makes the Roomba) needs to change battery suppliers.

The vacuum I got goes through 2 rooms and then runs out of juice. It could have finished my house in one charge if it had a Li-ion of the same size. Or you could have a better vacuum on it so that it actually picks up dirt instead of moving it around and still only vacuum 2 rooms. You get the point.

When I first saw this machine, I thought that all the things on Terminator (the movie) were coming true. Jokes apart, it really is a pretty decent robotic cleaner which does indeed find its way around. You can, pretty much, set it and forget it.

But then I realized that we had nothing to worry from the machines as long as battery technology evolves the way it has been in the past.

When Arnold Schwarzenegger's character said "I'll be back" on T2, he (it) actually meant "I'm running out of battery and I need to go find an outlet and charge for 8 h. I will then come back to look for you for the 1/2 hour my battery lasts. Wish me luck".

So much for the machines taking over.

If you constantly complain about how batteries are not evolving fast, did you ever consider for the second that maybe we are out to save the world in our own way?

Venkat

Did I say “Pull the Plug”? Meant to say “DO NOT pull the plug”

This could be a mea culpa post. It is rare that I’m wrong; it is even rarer that I admit it! So listen up folks.

In the early days of this blog, one of my dedicated (?) readers had asked me about the urban myth about not keeping the laptop plugged in to extend the life of the battery. In response, I had written a post titled “Pull the plug, your battery will thank you”. This post is the single most popular post on this blog. Almost a year after the post was made, it still gets the most hits.

The logic behind doing this is very sound. As you can read from that post, it has to do with side reactions that occur in the battery at the top of charge. Letting the battery discharge a bit is good for life because the rate of these side reactions decreases with decrease in the voltage. Suffice to say that I recommended you wait for the battery to charge and then you pull the plug and let it self discharge. This way you can extend its life.

I follow this rule pretty diligently. And I thought it had worked well for me. I have one laptop that is 2 years old, has had 297 cycles and has lost 4% of its initial capacity. Not bad. This is my workhorse. I use it every day and although I pull the plug diligently, my usage is such that I keep it pretty close to fully charged. So over the last 2 years, it has spent its time at close to, say, 4 V.

I have another laptop which is 3 years old. It is my personal laptop which we (my wife and I) use typically only over the weekend. We pull the plug diligently, but then the computer sleeps all week; self discharges; and by the end of the week is pretty much discharged. This battery, as of last week, had not lost any appreciable capacity even after 350 cycles.

These two data points tell you something about batteries. The cell with more cycles and with more time is cycling better! No magic. Just a simple fact that the battery was sitting at a lower state of charge and so the side reactions were not as worse. Ergo, better life.

Did I mention that both these are Macs? I have a third laptop given to me by a startup where I spend some of my time. This is a PC assembled by a company whose name starts with a D and ends with an L and has 4 letters to it. That computer is on its 4th battery in 2.5 years. After I lost my first battery I spent significant time trying to understand why my rules were not working and trying to tweak the rules. Soon, I came to the conclusion that with some batteries there really is no point trying to find ways to extend life. They are beyond help.

Actually, these rules have been helping this battery also. But different battery companies make batteries with different quality (achieving tightly-bound quality metrics has been a challenge in the manufacturing of batteries). So when you start with a battery with bad quality, there is only so much you can do.

But let us get back to my Mac.

Well... last weekend, my 3 year old Mac with no capacity fade suddenly appeared to have a dead battery. Not a battery with some loss in capacity; or one with 20% loss in capacity (which is considered dead). It was just plain dead. No charge; pull the plug and it would shutdown. It was on life support, literally!

The only way this battery would have a second life was if it were a Hindu and had not attained enlightenment and so was eligible (I suppose doomed is a better word) to be reborn. Somehow it seemed like even with the 1000 (or is it 10,000) Hindu gods there was no way to get this battery back up.

My first reaction was one of disbelief. There was no way a battery can go from no fade to completely dead in a matter of 1 week of self discharge. It had to be a software glitch that was not allowing the battery to be used.

Two hours, a bit of heartburn, and a detailed scouring of the world wide web later, I found various tricks to reset the battery management software and a software to measure the voltage of the battery and came to the conclusion that it was indeed dead. The (average) individual cell potential appeared to be close to 1.5 V! The typical cutoff potential of these cells is around 2.5 V.

So I pulled the plug and my battery died!!

A call to Apple confirmed that I was out of warranty and was told to go to the Apple store for a “detailed diagnostics”.

So I dragged myself to see the “genius” at the store (I’m not being condescending here; they really call the tech support guys genius’. Apparently if Einstein were alive today he would be working at the Palo Alto Apple store!).

Albert plugged a USB stick into my laptop; my screen turned into a series of numbers. Albert then turned and says that my battery is dead. Clearly he was on his way to writing a paper on the unified field theory.

I apologetically told him something like “I understand a bit about batteries and I don’t expect them to fail like this” and he said “I would not expect them to do that early on, but after 3 years I fully expect this”. Not “its possible”, but “fully expect”!!!

I debated giving up versus trying to argue on the finer points of battery chemistry but it seemed like a lost cause. I’ve been very reluctant using my celebrity status as the author of TWiB, and I have to say that it is intimidating arguing with a “genius”!

So I shelled out $130 for a new battery; thanked the guy for his help; and left.

I drove back re-examining my whole life and everything I know. I always thought there was some merit to the George Costanza (of Seinfeld fame) principle of doing the opposite of what our instincts tell us. Maybe I had it all wrong. Maybe you should not be pulling the plug. Maybe my jingle on battery rules needed to be rewritten.

A couple of days later my confidence started to return. I decided to do what anyone looking for credible information does: perform a google search to see if plugging in your laptop battery is bad. I came across my original blog post on this topic.  I sounded so convincing in the post that I started to get re-convinced that I was right about my rules.

So what is going on? How can a battery die when it is self discharging on sleep?

Here is my take.

All you PC folks are familiar with the hibernation mode that you can either force your computer to enter, or set it such that the power management utility moves the computer to hibernation after a while of being at sleep.

In sleep the computer stops many of the processes from running and thereby decreases the processing needs and hence drains the battery slowly. In hibernation, the computer (presumably) stops pretty much everything; stores the state in memory; and basically shuts down. This means there is very little drain on the battery.

In a Mac there is a sleep option, but there is no hibernation option. However, if you are in sleep and if your battery drains down to some small state of charge (say 5%), then it automatically moves into a “hibernation” mode; freezes the state and stops all the processes.

One thing we had noticed in the dead Mac (before it died) was that when we opened it over the weekend it was pretty much in hibernation with little juice left in the battery.

Ideally hibernation in a low state of charge is a good thing. Remember the rule “don't charge them too high”? Higher the voltage of the battery, worse will be its capacity fade. So storing it at a low state of charge (or low voltage) is actually good for the battery.

Did I mention that keeping the voltage way too low (i.e., over-discharging) is a bad thing?

This is because many cathode materials can get irreversibly damaged on over-discharge. More importantly, if an anode is over-discharged you can start dissolving the current collector (copper).

When you discharge the battery and it reaches its end of discharge voltage, depending on the battery chemistry (i.e., the anode and cathode that it uses) and on the design of the cell, the battery is limited by either the anode not having any lithium left, or the cathode not being able to accept any more lithium.

As you cycle this battery there are side reactions in both the electrodes. The extent of these side reactions depends on the design of the cell, the chemistry of the electrodes, the composition of the electrolyte, the level of impurities in the manufacturing, the way the battery is formed etc.

In other words, the side reactions are pretty complicated.

However, what we need to understand is that these side reactions can actually change the way the electrode reaches the end of discharge. They can even change which electrode limits the end of discharge.

So here is my take on what happened to the Mac battery.

The battery management system had a methodology of estimating the state of the battery and deciding if its needs to jump from sleep (the usual mode) to hibernation. This estimation was probably pretty accurate at the beginning of the life of the battery.

But years pass (3 in my case); the side reactions chug along; and they start changing the shape of the voltage curves, especially at the end of the discharge. Slowly, but surely, the management system was making errors in its estimation on the remaining charge.

The battery was not fading appreciably. Instead it was becoming harder to predict the time it would take to go from, say, 5% SOC to being fully-discharged.

I think that as my battery kept fading, the transition from sleep to hibernation was not getting triggered correctly, the battery over-discharged.

This is why when I checked the battery voltage it was sitting at 1.5 V.

I have a sneaking suspicion that my battery may actually come back to life if charged but that the power management software is not allowing any charge to reach the battery because the battery voltage is so low. I should have asked for my old,dead battery to try to resuscitate it myself!

If this sounds like an easy explanation considering how complicated all this is, its because it is the only plausible explanation I can come up with. If Steve Jobs would like to disagree, I’m listening.

So I still believe that if you “pull the plug, your battery will thank you”. I am glad I don’t have to go back and change 7 of my posts and apologize to my regular readers (all 7 of them!)

So what can one do about all this? Download the desktop hibernation widget at http://deepsleep.free.fr/ This gives you a way to move your Mac directly into hibernation instead of to sleep. This is probably a good thing anyway to conserve battery on long trips etc.

Or you could buy one of the new Macbook air computers which comes standard with hibernation.

In the meantime, my rule stands: Pull the plug, and your battery WILL thank you.

When Albert at the Apple store told me he “fully expected” my battery to behave this way, maybe, just maybe, he actually knew all this. After all, he is a “genius”.

Venkat