OakLeaf
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Re: All "Future" battery technology thread

Mon Jan 16, 2017 8:08 am

LOL, well maybe this will help solve that kind of problem...

Electrospun core-shell microfiber separator with thermal-triggered flame-retardant properties for lithium-ion batteries
http://advances.sciencemag.org/content/3/1/e1601978.full

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RegGuheert
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Re: All "Future" battery technology thread

Tue Feb 14, 2017 9:16 am

Here's another article making grandiose claims about low-cost energy storage: Silicon will blow lithium batteries out of water says Adelaide firm:
Signs of the Times wrote:1414 Degrees had its origins in patented CSIRO research and has built a prototype molten silicon storage device which it is testing at its Tonsley Innovation Precinct site south of Adelaide.

Chairman Kevin Moriarty says 1414 Degrees' process can store 500 kilowatt hours of energy in a 70-centimetre cube of molten silicon - about 36 times as much energy as Tesla's 14KWh Powerwall 2 lithium ion home storage battery in about the same space.
As always, the key to reading this type of claim is to look for the specification which is NOT mentioned and find out how bad things are in that area. In this case, the missing specification is efficiency.

Basically, the technology being put forth is to melt silicon and store heat in the latent heat of fusion of the silicon. In other words, the electrical energy is converted into heat for storage and then converted back into electricity for usage. Conversion of electricity into heat is 100% efficient and you can even achieve a COP above that if you can come up with a high-temperature heat pump (and have something you want to remove heat from at the same time). OTOH, the conversion of heat into electricity is subject to Carnot's limit on efficiency. At such high temperatures, the theoretical limit is not terrible, but in reality, the numbers are lower.

Looking at the company's website, we find out where this efficiency stands today: 31%. That number is lower than what is achieved today using hydrolysis and a fuel cell for H2 storage. Of course the difference is that this technology is MUCH cheaper than H2 fuel cells. OTOH, fuel cells have the dual benefits of offering long-term storage and the ability to store the H2 in existing natural gas pipelines.

To say that this technology "will blow lithium batteries out of water" is a real stretch. Sure, cheap storage is attractive, but ultra-high-efficiency storage is also extremely attractive since electricity is a much more valuable commodity than heat, especially in the summertime. Where do lithium batteries stand today in terms of efficiency?

- Battery round-trip energy efficiency: 98%
- Inverter one-way energy efficiency (3-phase): >98%

Overall Li-ion electrical-energy storage efficiency: >94%

This efficiency number continually approaches unity and the costs of both the battery and the power converter continue to drop. Cost notwithstanding, Li-ion battery storage has come about as close to ideal as can be achieved. As costs come down, the barrier to entry for other technologies will only get higher.
RegGuheert
2011 Leaf SL Demo vehicle
2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 3K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

Durandal
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Re: All "Future" battery technology thread

Tue Feb 14, 2017 9:54 am

When designing for solar powered homes, efficiency is the cheapest way to increase your "capacity" instead of increasing generation or storage. Thus, inefficient storage will not be attractive unless solar generation becomes STUPID cheap.
Pulled the trigger on going EV on 10/2016

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RegGuheert
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Re: All "Future" battery technology thread

Thu Feb 16, 2017 6:34 pm

RegGuheert in February 2016 wrote:BioSolar is developing a novel Super Battery cathode material which uses an advanced, low-cost polymer to replace the intercalation cathode material in a LI-ion battery. Here are their claimed characteristics:

Image

Add to this very high cycle life and you have an extremely attractive battery. Here is some of the verbiage from their site:
<snip>
The only thing I don't see mentioned on the website is efficiency. Since current intercalation chemistries achieves very nearly unity efficiency, it is hard to imagine a redox-based approach achieving similar performance. OTOH, I'm not sure how they could hope to achieve charge rates over 5C if efficiency is significantly lower. We'll see.
Following up a year later, I see that the above image is no longer shown on the website (though the link obviously still works), but the verbiage which I quoted is there and roughly the same.

What is interesting is that they are now highlighting work that they are doing on silicon-metal alloy anodes at the Super Battery link. There is quite a bit of interesting discussion of what is holding back Si-based anodes for Li-ion batteries:
BioSolar wrote:Silicon (Si) is one of the most promising anode materials being considered for next generation, high energy and high power lithium ion batteries (LIBs). Graphite is currently the most widely used anode material, but Si has attracted great attention because of its natural abundance, non-toxicity, and very high theoretical specific capacity of nearly 4200 mAh/g – about 10 times more capacity than conventional graphite anodes.

However, Si anodes suffer from large capacity fading and tremendous volume changes during lithium-ion charge-discharge cycling. The strains due to the huge volume changes actually pulverizes the Si material and eventually lead to electrode shattering and delamination, which adversely affect the battery performance and cycle life. These are the primary challenges to the commercial use of Si for battery anodes, which BioSolar intends to overcome.


Image

Image

They have tested a Si-metal alloy anode recently, and report that while it is inexpensive to manufacture, it is slightly better than what they purport to be the best Si anode product currently on the market:
BioSolar wrote:One of the significant parameters that can project battery performance is the capacity retention after 200 charging and discharging cycles. At identical loading, prototype batteries with BioSolar’s Si-M anode retained 78.1 percent of the original capacity whereas the benchmark silicon anode retained just 76.6 percent of its original capacity.
It is good that they achieved an improvement, but that is far from being an Earth-shattering result.
RegGuheert
2011 Leaf SL Demo vehicle
2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 3K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

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