Making the most energy dense battery from the palette of the periodic table

There hasn’t been much progress in batteries the past 200 years, not enough for affordable cars, let alone far more essential freight vehicles.

The very heavy, 4,647 pound Tesla Model S gets most of its mileage from aerodynamics, reduced rolling resistance, light-weight materials, and so on. The Tesla S goes further than other all-electric cars because it has more batteries.  Tesla S battery packs weigh 1,323 pounds (plus 350 lbs for the electric motor and inverter) versus 660 lbs for the Nissan Leaf (also pretty heavy at 3,340 lbs).

Batteries are simply not as energy dense as oil.  Pound for pound, oil is 500 times more energy dense than a lead-acid battery, and 120 times a lithium-ion battery (roughly, since there are many kinds of li-ion batteries).

So let’s start over and design a high-energy battery from scratch. The first step is to look at the periodic table to choose the best elements.

There are only 118 possible elements to work with, and most of them can be ruled out:

  • 39 are radioactive
  • 23 are far too scarce or expensive to scale up commercially such as rare earth and platinum group metals
  • 6 inert noble gases
  • 4+ toxic metals such as cadmium, cobalt,mercury, arsenic
  • and others are too heavy, too valuable (gold), hard to recycle, scarce, have too little reduction, oxidation, and other properties essential to making a battery work

Here is Aidan Stranger’s point of view (taken from a comment below): “Alkali metals (and indeed most other metals) have a greater reducing potential the further down the periodic table you go. So if reactivity were the deciding factor, caesium would be the best choice (francium’s not an option because it’s radioactive, extremely rare and very short lived). If cost is the deciding factor, sodium’s a better choice. But lithium is usually preferable for batteries because it’s lightweight; the higher specific energy more than makes up for the lower energy density.  But there are more factors to consider. Alkali metals only have one electron each. Something with more outer shell electrons could be more effective. Vanadium (with five) is often used in wet cells.  As for fluorine, forget it! Fluorine gas is far too dangerous to have in batteries, and oxygen fluorides are also dangerous and difficult to work with. I’m amazed that anyone’s even contemplated it. Unlike fluorine, cadmium can be contained fairly easily, so has been used for batteries despite its toxicity.”

periodic table reducing and oxidizing elements

 

 

 

 

 

 

Another possibility is looking at what elements could produce the highest voltage from the most reducing and most oxidizing elements.  The highest potential is nearly 6 volts with a  lithium anode (the strongest reducing element) and a fluorine cathode (strongest oxidizing element)  of -3.04 & 2.87 respectively).  Battery researchers know this and have been trying to develop such a battery since the 1960s. Scrosati et al have an excellent history of Li-F battery research and where we stand on different battery types today if you want to know the technical details.

The material electrons swim through between the anode and cathode matters as well.  Cells with aqueous (containing water) electrolytes are limited to less than 2 volts because the oxygen and hydrogen dissociate above this voltage. This is a shame, because water is very inexpensive. Lithium batteries don’t use water but this prevents electrons from flowing as well (high internal impedance) so 2.7 to 3.7 volts are achieved, rather than the maximum 6 volt potential between lithium and fluorine

The laws of physics means that there is no possibility of making a battery that rivals the energy density of oil, ever.  So the question is, if a 6 volt lithium-fluorine battery could be built — and it probably can’t — but if it could, would it be energetically cheap and powerful enough to move heavy-duty class 7 & 8 all-electric tractors, harvesters, road construction, and mining trucks?

If so, then is there enough lithium on the planet, including recycling, to make enough batteries for all electric cars, trucks, and utility-scale energy storage and lithium-battery mining trucks to haul ore to refining plants, and so on?

The main elements that lithium are dating are shown below. The rare earth elements aren’t in the battery, but are being used in the electric motor and generator, so even if lithium is recycled, the limits to EV may come from rare earth metals used other components of electric vehicles, which can NOT always be recycled:

li-ion periodic table other elements in batteries

by Alice Friedemann, www.energyskeptic.com

References

Scrosati, B., et al. 2013. Lithium batteries. Advanced technologies and applications. Wiley.

For a more in-depth look at battery chemistry see: Battery and Energy Technologies. Cell Chemistries – How batteries work. Electropaedia. mpoweruk.com

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7 Responses to Making the most energy dense battery from the palette of the periodic table

  1. Bill Chaffee says:

    An advantage that oil has is that the oxygen for burning it can usually be obtained from air (exceptions include submarines while submerged). However oil is still more energy dense if you count both reactants.

  2. Supposing it is true that oil has 120 times more energy density then lithum batteries, does it *necessarily* follow that lithium batteries will always be more expensive than gasoline cars? Is economic profitability not decided by many more factors? Tesla cars may still be a little bit more expensive, but not dramatically more – not 120 times more expensive as one would expect if energy density were the only factor determining price. I am not a technician, but my best guess is the difference can be explained by the fact that the amount of gasoline a car uses during its entire life is an awful lot larger then the amount of lithium you put in a battery? By the way, electric trucks are already made: http://en.wikipedia.org/wiki/Electric_truck

    • energyskeptic says:

      Yes, if you google “electric truck” you will get hits and that is reassuring enough for 99.999% of people to not delve any further. If you do, here is just a small sampling of what you will find:

      Diesel fuel, ounce for ounce, has over 90 times more energy density than the typical BEV li-ion battery, the LFP (LiFePO4) — 12,700 Wh/kg diesel versus 140 Wh/kg LFP.

      The main problem with low energy density is that an 88,185 pound long haul diesel truck can go 621 miles carrying 59,525 pounds of cargo. But a 2,500 kWh battery having energy density .1 kWh/kg, .14 kWh/liter, 80% depth of discharge (current level of technology) would cost $1.5 to $2 million dollars and weigh 55,116 pounds, almost 93% of the max cargo weight, and take up over 25% of a 40 foot container.

      Clearly money is somewhat related to energy density, because the companies building delivery BEV trucks (battery electric vehicle) have gone out of business (Smith electric late 2013) or dropped their electric truck business (Navistar), and their battery maker, A123, is also out of business, despite hundreds of millions of dollars in overall government grants AND federal and state subsidies to the buyers that made up the difference between a diesel and electric truck.

      This is why ENERGY DENSITY matters more than money! Electric trucks CAN be built – but so can a life-sized white house out of sugar cubes, until the energy to harvest, process, and deliver sugar cubes to your local store declines so much that this stops happening (which in our current system will be manifested as sugar companies going out of business, when the real cause is lack of energy).

    • Interesting link, thanks for sharing. There is only one vehicle that looks sorta like a conventional semi-truck, the Newton at the bottom. The claimed range is 55 miles to 110 miles; claimed top speed is 50mph. The max weight configuration is 12,000 lbs (probably 55 mile range for the heavy model). Compare to this page which says that conventional tractor-trailers range from 12,100 to 80,000 pounds. I also know from experience diesel trailers can sometimes push 70mph and I’m guessing their range is a heck of a lot more than 55 miles (energyskeptic mentioned 621 miles).

      Not sure how the cost of ownership compares, but I thought it was interesting to look at the limitations of an actual electric truck.

      (Apologies if I’ve messed up the formatting, I don’t see a preview button)

      • energyskeptic says:

        Batteries cost $600-$800 per kWh and weigh about 22 kg per kWh – they’re far too expensive and heavy and large even for delivery vans. Because of all the zero emission money and other government grants, delivery e-trucks are getting made that are 2-3 times more expensive than an equivalent diesel truck and have much shorter ranges.

        To charge just one 25 kWh battery pack in 5 minutes requires a power flow rate of 300 kW, equal to the peak power demand of a 100,000 square foot office building — where the hell would the electricity come from if they were scaled up commercially?

        The money would be much better spent on basic battery research, though I seriously doubt that the laws of physics and thermodynamics could ever make a powerful enough battery. Nearly all e-truck makers are using lithium-ion batteries, which have temperature issues that can shorten battery lifespan. Li-ion batteries degrade at temperatures over 95 °F and if recharged below 32 °F. Cold temperatures reduce braking energy recovery, acceleration, and limit the driving range. A truck that can go 80 miles at 77 °F goes 70 miles at 32 °F, 60 miles at 14 °F, and 40 miles at -4 °F. Subtract another 20 miles each if the cabin is heated 4 hours. AAA found the average EV battery range was 105 miles at 75°F, but dropped 59% percent to 43 miles at 20°F, and dropped 34% to 69 miles at 95°F

  3. Alice (energyskeptic), your knowledge of chemistry seems to be a bit limited. Alkali metals (and indeed most other metals) have a greater reducing potential the further down the periodic table you go. So if reactivity were the deciding factor, caesium would be the best choice (francium’s not an option because it’s radioactive, extremely rare and very short lived). If cost is the deciding factor, sodium’s a better choice. But lithium is usually preferable for batteries because it’s lightweight; the higher specific energy more than makes up for the lower energy density.

    But there are more factors to consider. Alkali metals only have one electron each. Something with more outer shell electrons could be more effective. Vanadium (with five) is often used in wet cells.

    As for fluorine, forget it! Fluorine gas is far too dangerous to have in batteries, and oxygen fluorides are also dangerous and difficult to work with. I’m amazed that anyone’s even contemplated it.

    Unlike fluorine, cadmium can be contained fairly easily, so has been used for batteries despite its toxicity.

    Before going any further, consider the reason that oil is so much more energy dense: there’s a lot of energy stored in oxygen molecules in the air. Batteries built to take advantage of this have been used in transport applications: see http://en.wikipedia.org/wiki/Zinc–air_battery

    Ultimately you’re asking the wrong question, focussing on the inability not the ability. There are some transport applications for which batteries are not suited and will never be ideal. If you need a 621 mile range then you’re better off sticking with an engine and fuel. Likewise for tractors and harvesters. But if the truck’s only used for drayage or local deliveries then a lower range isn’t a big problem and the benefits of regenerative braking and quiet operation could be significant. And if it’s just used for transporting large objects to work sites, range requirements would be even lower.

    • energyskeptic says:

      Thank you, I admit that I find battery chemistry confusing, but I was convinced about the volt differential as the most important factor, but from your point of view, apparently not? I would argue strongly that cadmium and other toxic metals, and rare earth or metals limited long-term should be avoided if anyone is serious about batteries long-term. Lithium is questionable on that score. Certainly for utility scale energy storage.

      The Port of LA and Long Beach drayage ZE project haven’t found an alternative kind of drayage truck that has a good business case. Truckers only get $100 a trip and can only make 3 to 5 trips a day, and use $3,000 old trucks to make it pay off – BEV trucks cost $307,890 dollars now (a new diesel $104,000) and can only go 100 miles and need to be recharged every 2 hours or less. Fast-charging in 30 minutes might shorten battery lifespan, whereas diesel trucks go 621 miles and only need to be refilled every 2 to 4 DAYS..

      Many of the companies making more suitable delivery class 3-6 trucks went out of business despite massive government grants and subsidies to buyers to make up the high cost difference between the diesel and battery truck. I don’t know why they’re even bothering to make trucks before there’s a decent battery that would make a viable business case.

      With ten year development time to improve a battery slightly, and peak conventional oil having happened in 2005-6 and USA fracked oil not compensating for much longer, we’re running out of time for a REVOLUTIONARY 5 to 10 times more energy dense battery that lasts 10 years. The research money is all going to CAR batteries, and any improvements there don’t easily or quickly translate to trucks. Cars are toys, the money should be going to essential freight vehicles, because once gas is rationed there won’t be many cars on the road.