
Batteries with 50 per cent more energy with pure silicon anode - Gravityloss
https://www.ecn.nl/news/item/batteries-with-50-per-cent-more-energy-one-step-closer/
======
zeristor
There is a recurrent pite patter of amazing new battery technologies, but of
course the question is it can it be mass produced.

Are there any good websites to gauge battery development progress as opposed
to the vital, but often ephemeral research progress.

~~~
hwillis
They steadily make their way into the mainstream. Silicon has been used in
batteries for several years now, in low amounts. Usually the new "big news"
comes with a significant gotcha. For silicon this has always been the cycle
life. Silicon hasn't seen larger use because it expands by 400% when filled,
compared to graphite's ~12% expansion. This though- this is very cool. If
they've actually demonstrated 100 cycles in a pouch cell, made with reel-to-
reel, that may mean that commercial cells are <5 years away.

Commercial cells have 500-800 cycles in their lifetime (until their capacity
falls to 80%) and are universally made on reel-to-reel machines. There are a
ton of difficulties moving from a coin cell to a prismatic/pouch cell to a
cylindrical cell, but I can't understate how encouraging it is that they got
to 100/400 cycles.

> Are there any good websites to gauge battery development progress as opposed
> to the vital, but often ephemeral research progress.

Not that I know of, sorry.

~~~
csours
What are the critical questions you should ask about battery technology?

Here are some I've thought of, please suggest others:

1\. Cost of raw materials - even if the tech improves, will it still be
expensive?

2\. Charge/Discharge cycle count - thermal and mechanical stresses

3\. Power to weight ratio; power to cost ratio

4\. Manufacturability - does it require novel manufacturing techniques or can
it be integrated into an existing product line

5\. Round trip energy losses

6\. Safety

~~~
hwillis
It helps to have some level of understanding of the chemistry. It can be hard
for anyone but a legitimate chemist to sniff out the bullshit in academic
papers (I've fallen prey to this before; I'm just an electrical engineer).

Raw materials can be important, but only very rarely and it can also be
misleading. By far most of the cost comes from the complexity and time of
manufacture. That makes it tricky. For instance sulfur is far cheaper than
other anode materials, but there will never be a cheap sulfur battery- it's
way too complicated.

It helps to know the basics[1] of battery manufacture: it's a decades old
process and highly optimized. The gist is that you apply coatings to a reel of
tape. If it sounds like it can't be put on a tape very easily, it will
probably fail the sniff test. Solid/ceramic electrolytes and most kinds of
nanotechnology fall into this category. Coating a tape is cheap, but using an
electron microscope or laser on every battery is not.

>2\. Charge/Discharge cycle count - thermal and mechanical stresses >3\. Power
to weight ratio; power to cost ratio

Critical. Any article, paper or press release will stress the interesting part
of the battery; it's up to you to figure out how relevant it is. If the
article emphasizes the current capacity, check the voltage of the chemistry.
If it emphasizes the energy density, check the power density. If it emphasizes
the weight, check the size. If it emphasizes safety, check everything. This is
often nontrivial though. It's possible to tweak your numbers to balance things
out- if you scale back the storage level you can increase cycle count, etc. If
a paper has improved _everything_ , it has a shot at being a next gen
chemistry. Of course it may also be bullshit.

In my experience just remembering to check the other attributes of the battery
will weed out 90%+ of bad articles. Most people are honest, they're just
obligated to play a certain game to keep their funding up. Unfortunately there
still are folks who will publish garbage though.

[1]
[https://www.youtube.com/watch?v=HJrNCjVS0gk](https://www.youtube.com/watch?v=HJrNCjVS0gk)

~~~
csours
Thanks!

------
hwillis
Silicon has been used in batteries for several years now in low amounts. It
hasn't seen larger use because it expands by 400% when filled, compared to
graphite's ~12% expansion. Most attempts to solve this have been extremely
complicated; nanopatterning, nanowires, graphene coatings to literally
compress the silicon metal, etc. It's one of the most promising avenues for
battery tech (silicon anodes alone may be able to increase overall energy
density by 2-3x), but it's been a very difficult problem to nail down. Nobody
has been able to get the trifecta of performant, long-lasting and cheap.

This though- this is very cool. If they've actually demonstrated 100 cycles in
a pouch cell, made with reel-to-reel, that may mean that commercial cells are
<5 years away. More likely 10+ years, as there are any number of things that
could shut this down and the tech may not be compatible with cylindrical
cells. Regardless, this is one of the most promising sounding press releases
I've read in a long time. PVD anodes will be expensive (this is similar to the
process to make mylar), but may be comparable to current processes, which
require a long, temperamental and expensive solvent + drying process. PVD
could even make this process more reliable (fewer failures) and consistent.

Commercial cells have 500-800 cycles in their lifetime (until their capacity
falls to 80%) and are universally made on reel-to-reel machines. If it can't
be done on reel-to-real it can't be done cheaply. There are a ton of
difficulties moving from a coin cell to a prismatic/pouch cell to a
cylindrical cell, but I can't understate how encouraging it is that they got
to 100/400 cycles. It's near unheard-of with fully silicon anodes.

This is also quite promising for future development. When they say 1000-2000
mAh/g they're referring to the anode itself- only the weight of silicon, not
the full battery. Silicon tops out near 4000 mAh/g, so there's a reasonable
headroom there. 50% increase in overall capacity for the entire battery is
fairly conservative. I presume it's because they can only apply very thin
layers of anode silicon. That may mean there's a lot of room for growth
though! They just have to thicken up that layer.

I'm still very skeptical of their long term capacity though. The problem with
anodes like this is the nanoscale features. You basically have a huge tangle
of velcro: that's done to increase the surface area exposed to the
electrolyte, which solves the anode expansion problem. The drawback is that
when that surface area becomes restricted, and it inevitably does, the SEI
affects the distribution of li ions inside the silicon, increasing damage.
They do appear to have found a way around that, but it may still put a long
term limit on capacity. The thicker you try to make the anode (to increase
energy density), the deeper the "velcro" becomes, and the more the SEI blocks
lithium. It may also make these batteries more sensitive to heat and
overcurrent and over/undervoltage- anything that disturbs the SEI may cause
dramatic irreversible effects.

Random related fun fact: Silicon requires the use of copper rather than
aluminum foils in batteries. Aluminum is a semiconductor dopant (the exact one
used in your computer, in fact), and if you deposit silicon onto an aluminum
foil it will form a very weak diode that causes a ton of problems. In
computers an extremely thin silicon oxide film is used between aluminum wires
and the transistors they connect. That layer is extremely resistive and causes
a bunch of headaches, but way smaller ones than tiny diodes would!

~~~
csours
> Commercial cells have 500-800 cycles in their lifetime (until their capacity
> falls to 80%)

What does this mean? I feel like I charge my phone more than 500-800 times.

~~~
hwillis
Under standard test conditions. That means 100% depth of rated discharge at a
set speed (between 1 and .1 C, ie fully charged/discharged in 1-10 hours) and
temperature.

Cycle life increases dramatically at lower depth of discharge, so if you
normally recharge your phone when it gets to 10% it'll last twice as many
cycles. High temperature and fast discharges will reduce that.

Essentially your phone is rated to be driven to 0% once a day for ~2 years,
give or take a bit. Less if it gets hot, which it will, because the battery is
used as a heatsink for the rest of the phone.

------
Bud
This article, and this comment thread, both seem to be ignoring what is
actually in the way of any "50% more energy" battery tech being used in
consumer laptops: FAA regulations limit all such batteries to 100 watt/hrs or
less. It's not Apple, it's not Samsung...they have no choice.

So until we get over our stupid post-9/11 policies, it doesn't matter if Star
Trek batteries magically spring into existence. The tech isn't going anywhere,
other than allowing something like Apple Watch to have a little more capacity.

~~~
ChuckMcM
Sorry but I have to disagree. While the limit is important for appliance
electronics like laptops it doesn't have any impact at all on electric
vehicles which are all mostly LiOn powered. 50% more range or 50% less weight
would be an interesting change to put in the mix at Tesla for example.

If you look at where batteries are going to be in volume in the next 20 years
it will be in grid storage, off-grid house energy storage, vehicles, and
potentially small industrial tools.

Of course if this particular breakthrough actually makes it into batteries we
will all be pleasantly surprised, as battery "breakthroughs" have a success
rate quite a bit lower than 'venture funded startups' :-)

~~~
btilly
If you can store 3/2 times as much with the same battery, you get the same
with 2/3 as much battery.

So that should be 50% more range or 33% less weight. Not 50% less weight.

------
dzhiurgis
Does moving on silicon reduce the need for nickel/cobalt?

~~~
hwillis
No, it shouldn't. There's the anode and the cathode- anodes are invariably
graphite currently, and cathodes are where the cobalt is (if there is cobalt).

This is about entirely replacing the anode graphite with silicon.

------
Gravityloss
[http://www.greencarcongress.com/2017/10/20171031-ecn.html](http://www.greencarcongress.com/2017/10/20171031-ecn.html)

Green Car Congress provides good context. This is also a potential
manufacturing revolution.

But it's a hard problem because of the massive swelling of silicon during the
lithiation, I think during discharge.

~~~
vorotato
<joke> Oh, Solution. Phones with stretchy backs and a balloon battery. </joke>

~~~
juliesulti
You laugh, but a pouch cell as mentioned in this article is in fact a cell
that is permitted to swell and shrink. That's probably why these researchers
started there.

As regards the article, Lithium-Silicon batteries have the potential to add
much more than 50% to the charge density of Lithium-ion batteries. More like
400% in theory. But nobody has demonstrated a cheap, production-ready process
for such a thing, because a charged silicon anode occupies much more space
than a discharged one, and the associated mechanical stress is a severe
problem. There has been an endless parade of press releases from universities
and national laboratories over the past 10 years on this topic.

~~~
altcognito
In cases where space and portability aren't a concern (utility energy
storage), this would be a great fit.

------
googletazer
Very thought provoking read. Speaking of batteries does anybody know what's
happening with LiFePO4?

~~~
hwillis
As far as I know, not too much. It's got pretty bad energy density and
nowadays it's very common to just skip it entirely. It's real claim to fame is
safety- it's not any cheaper despite the materials (half the cost per kg *
half the capacity per kg = the same cost), and I haven't heard much about
improving the performance.

Meanwhile other chemistries have shown much greater improvements in safety,
energy and power, and price is understood to be more about the scale than the
chemistry.

~~~
googletazer
thank you

------
tmaly
Does this still need lithium?

~~~
hwillis
Of course. Lithium is the third lightest element and nearly the most
electronegative (ie it has a high voltage). It's the best battery material you
could possibly pick! Not to mention, it's absurdly cheap and incredibly
common. Lithium makes up <1% of the cost of a battery.

~~~
davesque
Is it really that common? I was under the impression that it's somewhat scarce
and, furthermore, a large amount of Lithium deposits reside in regions of
relative political instability:

[https://www.economist.com/blogs/graphicdetail/2017/06/daily-...](https://www.economist.com/blogs/graphicdetail/2017/06/daily-
chart-12)

~~~
hwillis
It's more common in the crust than lead, the second most common battery type,
and uses ~100x less per kWh than lead acid batteries do.

Lithium is very poorly mapped. The last time the USGS surveyed it was in the
50s IIRC. For instance, that article is wildly inaccurate. It lists 6.9
million tonnes in the US. A single site, 45 miles to a side, in wyoming is
estimated at up to 18 million tonnes of lithium[1]. Then again America may
also count as a region of relative political instability.

I'll point out though that if you're gonna bring up political instability,
around 20x (up to 60x in cellphones) as much cobalt is used in batteries as
lithium, and virtually all of that comes from a single country: Congo. _That
's_ political instability. Lithium is a cakewalk by comparison, and fears
about it are just manufactured and overblown.

[1] [https://oilprice.com/Energy/Energy-General/New-Wyoming-
Lithi...](https://oilprice.com/Energy/Energy-General/New-Wyoming-Lithium-
Deposit-could-Meet-all-U.S.-Demand.html)

~~~
woodandsteel
From what I have read, lithium is poorly mapped because until recemt;u the
global demand was low so there was no motivation to go out and look for it.
Now that demand is skyrocketing, I bet a lot of companies are putting in a
real search effort.

~~~
hwillis
Yep, it wasn't until... 2013, I think(?), that batteries became the #1
consumer of lithium, driven entirely by Tesla. In 2009, only 21% of lithium
was used for batteries, while 30% was used to in glass and ceramics. Glazes
and such, as far as I understand.

[1]
[https://pubs.usgs.gov/circ/1371/pdf/circ1371_508.pdf](https://pubs.usgs.gov/circ/1371/pdf/circ1371_508.pdf)

