Sunday, October 23, 2016

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. 


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