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I'm not crazy, the attack has begun.
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Discussion Starter · #1 ·
It seems beholden on me, as (it seems) the only professional engineer here with this sort of background, to explain why lithium ion batteries, in their current technology, are limited and not going to go much further.

On the one side of a battery one has a transition metal oxide electrode. The 'transition' means a transition of oxidation number, such as exhibited by metals like nickel, cobalt, iron, cadmium, manganese. For example, manganese can present oxidation numbers of 2, 3 or 4.

Let's consider the earliest cells using the spinel form of lithium manganese oxide. This structure meant relatively easy flow of lithium ions, there are other formations.

2(LiMnO2) goes to LiMn2O4 plus an +Li ion. It's the manganese atom that 'does the work', changing its oxidation stage from 3 to 2, and back, liberating or capturing the lithium ion.

So, one lithium ion is liberated from a compound with a molar mass of 2 x (6 + 55 + (2 x 16) = 186.

All the transition metals have a similar atomic mass, and all are in that form (except LFP where it is a phosphate instead of an oxide, which makes it heavier).

On the carbon side +Li + 6C goes to LiC6. The C6 is a further 6 x 12 = 72 Dalton units.

So, one mole of electrode material is ALWAYS about 260g (186 + 72). It simply cannot be anything else, there is no 'infinite improvement' possible, it is a physical recipe of materials, you cannot make a large cake with half an egg.

If we take 1kWh to be 3.3Ah of 96 cells at the average electrode potential, which is 11,880C, which in turn is 0.12 moles of material, or 32 grammes of material per cell (at 260g/mol), being in total 32g/cell x 96cells = 3kg/1kWh.

Or 330Wh/kg.

Even if we assume negligible masses for the cell pouch and the electrolyte (such masses would reduce that figure, of course), the absolute limit for a transition metal oxide/graphite system is going to be around 300Wh/kg.

If we are already achieving 300Wh/kg, then there is no further developmental gains on mass, or reductions in electrode materials to be achieved. 300Wh/kg represents a fully optimised system already.
 

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Why graphite?
 

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I'm not crazy, the attack has begun.
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Discussion Starter · #3 ·
Why graphite?
That is what the thread is about. Says it quite clearly in the title.

I am not supposing other battery possibilities are excluded, but we have ONLY seen this technology develop in the last 20~30 years, nothing else has come to market so why talk about it as if it is a present technology?

This is about commerciality; no-one is going to throw away 3 decades of industrial development until something else is already on the market, proving itself in the fiery-furnace of the real world.
 

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So this is just the limit of one type of battery, and other types don't have the same limit.

After the triple expansion steam engine reached it's limits... something came along to replace it. And someone threw away decades of industrial development.

Might happen again.
 
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If we are already achieving 300Wh/kg, then there is no further developmental gains on mass, or reductions in electrode materials to be achieved. 300Wh/kg represents a fully optimised system already.
For stored energy per unit weight, that may be true. I don't think it's the end of the line for battery research, though.
Work progresses on reducing cost, improving safety, enabling faster charging speeds, increasing lifetime and no doubt several things I haven't thought of. These benefits have more to do with manufacturing process than the battery chemistry itself. Solid state batteries, for example, look promising but so far cost too much to make.
 

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Discussion Starter · #7 ·
A quick google "tesla battery kwh per kg" gets me some info.

This website mentions 380 Wh/kg:
Tesla unveils new EV battery design, but Musk downplays vehicle-to-grid application
and this one has Elon hinting at 400 Wh/kg:
Elon Musk: 400 Wh/kg Battery Cells Likely In Just 3-4 Years
... and other links, incl one claiming to have achieved the magic 400.
Discuss :)
No indication if they are Li(MO)x-C

As I mentioned above, this is beyond the limit of that technology.
 

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Discussion Starter · #8 ·
For stored energy per unit weight, that may be true. I don't think it's the end of the line for battery research, though.
Work progresses on reducing cost, improving safety, enabling faster charging speeds, increasing lifetime and no doubt several things I haven't thought of. These benefits have more to do with manufacturing process than the battery chemistry itself. Solid state batteries, for example, look promising but so far cost too much to make.
All correct of course.

The reason for this thread is the casual assumption in other threads that 'this' particular technology can continue indefinitely.

The argument was that ICE had reached the end of their 100 year development without further development possible, but 10 year old Li tech is continuing, whereas it's actually the complete reverse; the battery tech has to change for further progress while ICE still has a way to go, or likewise can change the base tech to improve, like batteries will have to.

Li(MO)x-C is already at the end of its development curve.

To go further, a new tech is now needed.
 

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For passenger cars does this matter though?

Today's battery technology and power densities are good enough for the vast majority of passenger vehicles, with a few exceptions at the heavier/larger end. The issue is now the manufacturing capacity and cost but manufacturing capacity is expanding sharply and cell costs are falling.

And there's the interesting developments with LFP, and the announcement last year of CATL's success developing a sodium ion battery, reducing the need for expensive/rarer metals like cobalt and nickel.

For passenger cars the technology is pretty much settled, it will be EVs and now its just a case of needing time for the manufacturing capacity to grow and costs to fall to push ICE out of the new car market, then 15 years or so for the existing ICE vehicles to be flushed through the UK car park to scrapping at end of life.
 

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Arguably ICE is pretty limited, if only by the Carnot cycle efficiency theorem. If you want hugely better combustion efficiency, you have to raise the top temperature used in the burning, but this requires even more high-temperature resistant alloys, not to mention the problems of also burning Nitrogen at these v high temps as done by diesel combustion, but not the old-fashioned petrol progressive-burn combustion. Gas turbine engines in cars have been tried, of course...
 

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Discussion Starter · #11 ·
Arguably ICE is pretty limited, if only by the Carnot cycle efficiency theorem.
I intended this thread to scope out the fact that current battery technology has to change for it to make a progressive path in the future. The connection with heat engines is simply that if it is OK to accept battery tech has to change to make it future-relevant then why the reluctance for heat engines?

Using a REx in a car burning fossil fuels can be more efficient than burning that fuel in a power station for electricity.
 

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Using a REx in a car burning fossil fuels can be more efficient than burning that fuel in a power station for electricity.
If a REx can generate electric power more efficiently than a power station... Why do we bother with power stations? Build arrays of REx's
 

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Discussion Starter · #13 ·
If a REx can generate electric power more efficiently than a power station... Why do we bother with power stations? Build arrays of REx's
How do you install a power station in a car?

The reason a REx in a car can be more efficient than a power station is because it can generate power at 40% while sending a further 40% of the calorific energy to the heating system. So, 80% CHP efficiency.

You can't pipe the waste heat from 60% efficient power stations into cars on the move.
 

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If a REx can generate electric power more efficiently than a power station... Why do we bother with power stations? Build arrays of REx's
Low production efficiency only has environmental ramifications w/ CO2 producing fuels and nuclear— not so much an issue with solar/wind/geothermal/ocean thermal/tidal, etc.
 

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How do you install a power station in a car?

The reason a REx in a car can be more efficient than a power station is because it can generate power at 40% while sending a further 40% of the calorific energy to the heating system. So, 80% CHP efficiency.

You can't pipe the waste heat from 60% efficient power stations into cars on the move.
Two words.

Heat pump.
 

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How do you install a power station in a car?

The reason a REx in a car can be more efficient than a power station is because it can generate power at 40% while sending a further 40% of the calorific energy to the heating system. So, 80% CHP efficiency.

You can't pipe the waste heat from 60% efficient power stations into cars on the move.
Assuming that the waste heat is actually useful.

Maybe in a Montana winter most of it is.
 

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The details you've put down there are really interesting thanks Donald, but you've only shown that Li(MO)x-C is reaching it's peak energy density. But equally important are developments in terms of cost to manufacture, minimisation of environmentally sensitive materials, longevity and charge rates? So you're not looking at a "system" in terms of this battery chemistry, but one aspect of the battery.

LFP batteries at half the price or less with even greater lifespans and charge rates would still be massively useful and drive uptake. Much like the main thing driving solar panels has been the rapid reduction in manufacturing costs, not primarily increases in efficiency.

Internal combustion engines as a system (efficiency, cost to manufacture, reliability etc) are surely much closer to being fully optimised.
 

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Discussion Starter · #20 · (Edited)
The details you've put down there are really interesting thanks Donald, but you've only shown that Li(MO)x-C is reaching it's peak energy density. But equally important are developments in terms of cost to manufacture, minimisation of environmentally sensitive materials, longevity and charge rates? So you're not looking at a "system" in terms of this battery chemistry, but one aspect of the battery.
Correct.

The ongoing improvements are in longevity, material availability, cost, manufacturability, reliability, recyclability, etcc..

Yes. And I have no reason to doubt plenty potential gains in those areas.

But not in mass.

So the cells of a 500kWh BEV's battery alone would weight at least 1,500kg. Not practical.

Volume is almost maximised now but some scant gains still to be made there.

This was just to show the limits of mass; Wh/kg for L(MO)x-C, and nothing else.

LFP batteries at half the price or less with even greater lifespans and charge rates would still be massively useful and drive uptake.
100% agree.

Internal combustion engines as a system (efficiency, cost to manufacture, reliability etc) are surely much closer to being fully optimised.
That's my point. ICE, like L(MO)x-C, yes, pretty close but still room for improvement.

The issue is that people want to talk about batteries beyond L(MO)x-C, as well they might and we're all looking forward to that. In which case, why are they so eager to disregard heat engines beyond ICE? Do you see my point?

Seems a bit 'dishonest' to sing loudly about the golden age of BEVs to come by discussing future battery tech, while critiquing heat engines only with reference to current ICE technology. What if we reversed that paradigm; we can only discuss today's battery technology when looking at future radical heat engine developments? That wouldn't seem fair, right?
 
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