# Is there any battery chemistry that can compete with gasoline on energy density? **URL:** \ **Category:** Factual Questions\ **Created:** [February 24, 2015, 6:21pm UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536 "2015-02-24T18:21:18Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [February 25, 2015, 5:53pm UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/21 "2015-02-25T17:53:34Z")
Do hydrogen fuel cells count as batteries? ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [February 25, 2015, 6:01pm UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/22 "2015-02-25T18:01:10Z")
> [@Really\_Not\_All\_That\_Bright](#): > > Do hydrogen fuel cells count as batteries? Not technically. But as \*\*Chronos \*\*says, any kind of box that produces that 'lectric stuff to power car wheels will probably be known as a “battery” to Joe Driver. I think batteries are a stagnant technology and will remain so until some absolutely unforeseen breakthrough occurs. We’ve been working on them too long, with all the brain and money power the project can absorb, to believe some huge leap in efficiency is just around the corner. Fuel cells will be a stopgap technology to leverage the existing fossil-fuel infrastructure into a cleaner, more efficient transportation and grid power system. But I’d give it no more than 25 years as a viable alternative, negligible in 50. Capacitors. Some form of electric storage based on capacitance rather than chemical conversion. That’s absolutely the way to bet, but there are some hurdles to clear before it’s even on a par with today’s Li batteries. I do think those hurdles are identified and surmountable, though - far more so than the problems facing any great leap in battery tech. ---
**Author:** ![drachillix](https://avatars.discourse-cdn.com/v4/letter/d/48db29/32.png) [@drachillix](https://boards.straightdope.com/u/drachillix)\ **Post date:** [February 25, 2015, 6:58pm UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/23 "2015-02-25T18:58:31Z")
> [@Amateur\_Barbarian](#): > > The first is to take all the automotive engineering of the last 25 years that’s put 300-600 HP under the hood of a great many models, and apply it to much smaller powerplants - 150 HP out of 1 liter or so, something that could not be done short of a racing engine just a few years back. These engines will still lack some acceleration zip, but would be adequate for most drivers in most situations. It’s a matter of selling it as thoroughly as Dodge sold the “Hemi.” The Demi Hemi? 😃 ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [February 25, 2015, 7:00pm UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/24 "2015-02-25T19:00:09Z")
> [@drachillix](#): > > The Demi Hemi? 😃 Bulls-eye. Right up there with the Ford (4-cylinder) Turbine™. ---
**Author:** ![Novelty\_Bobble](https://avatars.discourse-cdn.com/v4/letter/n/a3d4f5/32.png) [@Novelty\_Bobble](https://boards.straightdope.com/u/Novelty_Bobble)\ **Post date:** [February 25, 2015, 9:14pm UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/25 "2015-02-25T21:14:12Z")
> [@Amateur\_Barbarian](#): > > We have only two routes for greater overall fuel-based car efficiency. The first is to take all the automotive engineering of the last 25 years that’s put 300-600 HP under the hood of a great many models, and apply it to much smaller powerplants - 150 HP out of 1 liter or so, something that could not be done short of a racing engine just a few years back. These engines will still lack some acceleration zip, but would be adequate for most drivers in most situations. It’s a matter of selling it as thoroughly as Dodge sold the “Hemi.” This, Ford already have a 1.0 litre engine putting out 123bhp on the market. It is very well regarded and it is nippy but still gives 50+mpg. Apparently it’ll be boosted further by an electric supercharger and put out 177bhp (8 sec 0-62) and still be economical. Also the mainstream 1.2 tsi petrol engine from VAG puts out over 100 bhp with plenty of grunt and nearly 60mpg. I’ve driven one in a golf and even on speedy autobahns it never feels like it struggles. Heck, I’m looking at various cars in order to buy a new one at the end of the year and as far as large family cars go, I’m spoiled for choice with powerful turbo-diesels that do sub 10 second 0-62 and more than 60 mpg. My budget doesn’t stretch to it but BMW have a rather epic economical beast > [@](#): > > With a 3-litre single-turbo straight-six developing 254bhp and 413lb ft, it’s a seriously muscular machine. Limited to 155mph and capable of hitting 62mph in 5.6sec, it promises to combine E46 M3 performance with 58mpg economy. That is better economy than a prius and having driven previous M sport diesels I have no reason to doubt it. And all of this will just get better and better. The engines will get more powerful, more economical, more accessible without any sacrifice of real-world performance and all the while battery/hybrid technology stands still the ICE world will increase the gap. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [February 25, 2015, 9:19pm UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/26 "2015-02-25T21:19:33Z")
> [@Amateur\_Barbarian](#): > > Not technically. But as \*\*Chronos \*\*says, any kind of box that produces that 'lectric stuff to power car wheels will probably be known as a “battery” to Joe Driver. > > I think batteries are a stagnant technology and will remain so until some absolutely unforeseen breakthrough occurs. We’ve been working on them too long, with all the brain and money power the project can absorb, to believe some huge leap in efficiency is just around the corner. > > Fuel cells will be a stopgap technology to leverage the existing fossil-fuel infrastructure into a cleaner, more efficient transportation and grid power system. But I’d give it no more than 25 years as a viable alternative, negligible in 50. > > Capacitors. Some form of electric storage based on capacitance rather than chemical conversion. That’s absolutely the way to bet, but there are some hurdles to clear before it’s even on a par with today’s Li batteries. I do think those hurdles are identified and surmountable, though - far more so than the problems facing any great leap in battery tech. Not Capacitors, but Supercapacitors. They can store a lot of energy and discharge it efficiently, and in some ways are better than a rechargeable battery. They can certainly be recharged many more times that a rechargeable bvattery. They already see some limited use in electric vehicles: > [@](#): > > Hybrid electric vehicles[edit] > > Main article: Hybrid electric vehicle > > See also: Hybrid vehicle drivetrain > > Mazda2 (since 2010) > Supercapacitor/battery combinations in electric vehicles (EV) and hybrid electric vehicles (HEV) are well investigated.[113][162][163] A 20 to 60% fuel reduction has been claimed by recovering brake energy in EVs or HEVs. The ability of supercapacitors to charge much faster than batteries, their stable electrical properties, broader temperature range and longer lifetime are suitable, but weight, volume and especially cost mitigate those advantages. > > Supercapacitors lower energy density makes them unsuitable for use as a stand-alone energy source for long distance driving.[164] The fuel economy improvement between a capacitor and a battery solution is about 20% and is available only for shorter trips. For long distance driving the advantage decreases to 6%. Vehicles combining capacitors and batteries run only in experimental vehicles.[165] > > As of 2013 all automotive manufacturers of EV or HEVs have developed prototypes that uses supercapacitors instead of batteries to store braking energy in order to improve driveline efficiency. The Mazda 6 is the only production car that uses supercapacitors to recover braking energy. Branded as i-eloop, the regenerative braking is claimed to reduce fuel consumption by about 10%.[166] > > Russian Yo-cars Ё-mobile series is an ё-concept and ё-crossover hybrid vehicle working with a gas driven Wankel motor and an electric generator for driving. A supercapacitor with relatively low capacitance recovers brake energy to power the electric motor when accelerating from a stop.[167] > > Toyota’s Yaris Hybrid-R concept car uses a supercapacitor to provide quick bursts of power.[149] > > PSA Peugeot Citroën fit supercapacitors to some of its cars as part of its stop-start fuel-saving system, as this permits faster start-ups when the traffic lights turn green.[149] > **[Supercapacitor](https://en.wikipedia.org/wiki/Supercapacitor)** > > A supercapacitor (SC), also called an ultracapacitor, is a high-capacity capacitor, with a capacitance value much higher than solid-state capacitors but with lower voltage limits. It bridges the gap between electrolytic capacitors and rechargeable batteries. It typically stores 10 to 100 times more energy per unit volume or mass than electrolytic capacitors, can accept and deliver charge much faster than batteries, and tolerates many more charge and discharge cycles than rechargeable batteries.\[2... ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [February 25, 2015, 9:54pm UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/27 "2015-02-25T21:54:52Z")
> [@CalMeacham](#): > > Not Capacitors, but Supercapacitors.[URL=“[Supercapacitor - Wikipedia](http://en.wikipedia.org/wiki/Supercapacitor)”] Ever thought about writing sf? 😃 ---
**Author:** ![Cheesesteak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cheesesteak/32/3694_2.png) [@Cheesesteak](https://boards.straightdope.com/u/Cheesesteak)\ **Post date:** [February 25, 2015, 10:00pm UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/28 "2015-02-25T22:00:31Z")
> [@Amateur\_Barbarian](#): > > Capacitors. Some form of electric storage based on capacitance rather than chemical conversion. That’s absolutely the way to bet, but there are some hurdles to clear before it’s even on a par with today’s Li batteries. I do think those hurdles are identified and surmountable, though - far more so than the problems facing any great leap in battery tech. Capacitors scare the crap out of me. Let’s say you develop a car with capacitors powerful enough to give you 200 miles of range. You have stored the energy equivalent of maybe 3 gallons (or 12L) of gas, accounting for efficiency differences. 12L of gas is maybe 8kg. Gasoline is about 10x as energy dense as TNT, so it’s the equivalent of 80kg of TNT. What scares me isn’t so much the amount of energy, it’s that the energy isn’t stored in a relatively safe chemical form. It’s contained physically. If the integrity of the container is breached, the energy is released, all of it, right away. Batteries and gasoline don’t just release all their energy right away, it has to work its way through the chemical process, an inherent limiter. TNT is designed to release its energy all at once, and we’re rightfully more scared of carrying 175lbs of TNT than we are a few gallons of gas. ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [February 25, 2015, 10:06pm UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/29 "2015-02-25T22:06:16Z")
Any form of concentrated fuel-energy in a practical moving vehicle is potentially dangerous. People burn to death in moderate crashes in modern cars, even. I don’t see capacitors as inherently more dangerous than 20 gallons of highly volatile fuel. This does point out something I’ve noticed, especially in the hot-rod and DIY mechanic worlds. Nothing mechanical scares many wrench guys; they’ll reach past a red-hot revving engine to twiddle something without a second thought… but the simple electrical circuit of the headlights terrifies them so much they get someone else to work on it. (A lot of times, that someone was me… and they’d be in total awe when the lights came on. Jeez.) ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [February 25, 2015, 10:09pm UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/30 "2015-02-25T22:09:15Z")
> [@Amateur\_Barbarian](#): > > Ever thought about writing sf? 😃 Supercapacitors are a reality. I’ve replaced the rechargeable batteries in by hand-crank flashlights because you can let a supercapacitor sit around for years before you recharge it, and it’ll come right back to life. If you do that with a rechargeable battery it probably won’t work – letting all the charge on one of those bleed completely off makes it impossible to recharge. And, you know (I suspect), that I _do_ write SF. ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [February 25, 2015, 10:11pm UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/31 "2015-02-25T22:11:51Z")
Humor alert. Of course I know you write sf, and that the term has been around a bit. It just sounds so… Campbellian. “Batacitor,” now… well, it’s better than “Shipstone,” I guess. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [February 25, 2015, 10:50pm UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/32 "2015-02-25T22:50:09Z")
> [@Amateur\_Barbarian](#): > > We could cut the weight pf almost any vehicle on the road by 1/3 or more - but not while preserving the accepted standard of safety. Sure you can–but then it costs more. A wholesale switch from steel to aluminum would be a huge weight improvement with no sacrifice in safety. It just costs more. Further material improvements to carbon fiber, etc. would do even better but are more expensive. > [@Amateur\_Barbarian](#): > > All I know is that in 150 years or so, with pretty much a maximum amount of motivation and potential rewards, battery efficiency by weight density has remained almost static. I believe that the ratio of gas to the best batteries available today is still greater than the ratio of those batteries to basic liquid lead-acid types from the 1880s. That’s an irrelevant comparison. Battery energy density as compared to gasoline is just one factor in whether an electric car as a _whole system_ performs better than a gasoline car. Electric cars have many other factors working in their favor and to ignore them gives a distorted picture. At any rate, it’s absurd to say that battery tech has remained static. [It’s improved by around 8x](http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/Articleimage/2011/EE/c0ee00777c/c0ee00777c-f2.gif) since 1900. Actually, it’s probably pushing 10x these days (in the 5 years since the chart was made). Battery technology moves slowly. That’s to be expected since it largely relies on bulk material science. But that doesn’t mean it’s static. Small improvements add up over time. Even without any significant breakthrough, we’ll continue to get small improvements in packaging, chemical purity, anode/cathode chemistries and microstructures, etc. I see no reason not to expect around another factor of two from relatively conventional lithium-ion, and not dependent on anything radical. I think that the mainstream press has trained many people to respond only to breakthroughs and to ignore steady, incremental progress. And yet it’s the latter that makes a bigger difference in the real world. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [February 25, 2015, 11:31pm UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/33 "2015-02-25T23:31:05Z")
Fuel cells are a joke, and basically a tax dodge. Their end-to-end efficiency is much worse than pure electric cars. There are just too many intermediate steps with big efficiency losses as compared to pure electrics. There’s basically no infrastructure. There’s like a dozen filling stations in the US. And you _have_ to use a filling station; unlike an electric, you’ll never get a hydrogen generator for your garage. What’s going to drive filling station growth? Only crazily dedicated people are going to buy a vehicle that they can fill at like one place in their city. But no one is going to install a station that serves 15 people. Contrast with electrics, which are useful even with _no_ public stations (never mind that there are plenty of public chargers these days). It’s _way_ more expensive than electric. Tesla as a company isn’t making money, but each individual car they sell is profitable. Even without tax credits. Compare to fuel cell vehicles, of which several are sold for ~$60k but have a manufacturing cost more like $150k (note that these are really low-performance vehicles). Where is the hydrogen supposed to come from? Right now, _all_ of it comes from fossil fuels. Unlike electric where a good portion comes from clean sources like hydroelectric and nuclear (and to a lesser extent, wind+solar). As alternatives come online, maybe we can get hydrogen from electrolysis–but that’s _yet another_ inefficient step in the hydrogen generation process that pure electrics don’t have to deal with. And now the tax dodge. States like California have additional credits for zero-emission vehicles with fast refueling/recharging. Fuel cells meet this criteria. Electrics without battery swapping do not. It’s not that important in the grand scheme of things (since you still have a net time savings in an electric), but it’s distorted the market. Frankly, it’s (IMHO) the only reason why Tesla is bothering with battery swapping. They know it doesn’t actually matter–they have over 50,000 customers happily driving without it–but it’s worth doing for the money. It’s annoying but they’d be stupid not to do it. Maybe in 20 years, many of these problems will be fixed. By that time, batteries will have improved by a factor of two, and gotten cheaper by a factor of 4, and charging will be a non-issue. Automotive fuel cells will be obsolete before they had any traction at all. ---
**Author:** ![iljitsch](https://avatars.discourse-cdn.com/v4/letter/i/77aa72/32.png) [@iljitsch](https://boards.straightdope.com/u/iljitsch)\ **Post date:** [February 25, 2015, 11:46pm UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/34 "2015-02-25T23:46:10Z")
Sure, batteries store much less energy per unit of mass than hydrocarbons, but that’s only part of the story. An internal combustion engine is easily five times as heavy as an equivalent electric motor. I was under the impression that there are various chemistries that use air that could be much more energy dense than the types of batteries we use today. Also, do we really need to store all that electricity onboard? Why not use a third rail or trolleybus like system where cars can tap into the grid while driving? ---
**Author:** ![Terr](https://avatars.discourse-cdn.com/v4/letter/t/839c29/32.png) [@Terr](https://boards.straightdope.com/u/Terr)\ **Post date:** [February 25, 2015, 11:59pm UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/35 "2015-02-25T23:59:35Z")
> [@iljitsch](#): > > Sure, batteries store much less energy per unit of mass than hydrocarbons, but that’s only part of the story. An internal combustion engine is easily five times as heavy as an equivalent electric motor. > > I was under the impression that there are various chemistries that use air that could be much more energy dense than the types of batteries we use today. [http://boards.straightdope.com/sdmb/showpost.php?p=18159875&postcount=5](http://boards.straightdope.com/sdmb/showpost.php?p=18159875&postcount=5) ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [February 26, 2015, 12:04am UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/36 "2015-02-26T00:04:44Z")
You don’t need a hydrogen for your fuel cell. You could use good old octane. And if we’re manufacturing hydrogen for transportation fuel we’d probably use it in an internal combustion engine. The only trouble is, hydrogen is a lousy fuel for several reasons. It’s a gas, it’s lighter than air, it can migrate through all kinds of materials, it’s corrosive, and on and on. If we’re manufacturing transportation fuel out of air and water using surplus electricity we might as well stick a few carbons on there and get a fuel that’s liquid at room temperature. ---
**Author:** ![boffking](https://avatars.discourse-cdn.com/v4/letter/b/858c86/32.png) [@boffking](https://boards.straightdope.com/u/boffking)\ **Post date:** [February 26, 2015, 12:19am UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/37 "2015-02-26T00:19:11Z")
Whats wrong with using a gas as fuel? We managed to make stoves, generators, and forklifts run on propane. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [February 26, 2015, 12:35am UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/38 "2015-02-26T00:35:10Z")
> [@Lemur866](#): > > You don’t need a hydrogen for your fuel cell. You could use good old octane. Then it’s no longer zero-emission at the tailpipe. As a full system that might be genuinely better–but no one’s going to give tax subsidies for vehicles emitting CO2. > [@boffking](#): > > Whats wrong with using a gas as fuel? We managed to make stoves, generators, and forklifts run on propane. There are zillions of buses and other commercial vehicles that use compressed natural gas. It’s ok. It’s pretty cheap, has fewer carbon emissions than gasoline, and has at least a modest infrastructure. There’s also the political advantage of greater domestic production. But it seems like it’s met its limits for installed base. It works well for commercial vehicles since they are not so dependent on fueling stations. As far as consumers are concerned, though, CNG cars seem worse than gasoline in basically every way (again, contrast with electrics, which have some serious upsides compared to gas, and may win out for particular consumers). ---
**Author:** ![PastTense](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pasttense/32/14550_2.png) [@PastTense](https://boards.straightdope.com/u/PastTense)\ **Post date:** [February 26, 2015, 12:57am UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/39 "2015-02-26T00:57:14Z")
> [@Dr.Strangelove](#): > > As far as consumers are concerned, though, CNG cars seem worse than gasoline in basically every way If the price of gasoline massively increases while the price of natural gas only has limited increases this makes CNG cars attractive. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [February 26, 2015, 3:21am UTC](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536/40 "2015-02-26T03:21:05Z")
> [@Chronos](#): > > Battery technology has probably nearly reached the limit of what’s possible, but do note that batteries aren’t the only option for fueling electric cars. You could also make an electric car that used fuel cells or capacitors. The technology for maximal energy density in electrochemical batteries isn’t quite a the limit of what is possible, but it is almost certainly within an order of magnitude. There are theoretical means to increase the energy density, e.g. chemical excimers. However, chemical excimers have very short lifetimes, on the order of nanoseconds. There are theoretical states of matter (Ryberg matter) in which excimers can be more stable, but we can’t produce them except in very small quantities for a few seconds. > [@Really\_Not\_All\_That\_Bright](#): > > Do hydrogen fuel cells count as batteries? Hydrogen fuel cells are not a viable technology for transportation energy, notwithstanding the fact that hydrogen still has to be produced from some source which is generally less efficient and has a larger carbon footprint than just burning gasoline. Hydrogen is difficult to store, reacts with many common metallic materials to embrittle them, has high detonability, and worst of all, very low energy density even in liquid cryogenic form. Hydrogen as a transportation fuel, and the so-called “hydrogen economy” in general is a sham. > [@Cheesesteak](#): > > What scares me isn’t so much the amount of energy, it’s that the energy isn’t stored in a relatively safe chemical form. It’s contained physically. If the integrity of the container is breached, the energy is released, all of it, right away. Batteries and gasoline don’t just release all their energy right away, it has to work its way through the chemical process, an inherent limiter. TNT is designed to release its energy all at once, and we’re rightfully more scared of carrying 175lbs of TNT than we are a few gallons of gas. Batteries can also explode or combust highly energetically. One of the major problem with lithium-sulfur batteries (the most promising near term improvement over lithium ion) is that they can undergo “violent cell rupture”, burn energetically and release very caustic and toxic fumes. Supercapacitors can potentially discharge very rapidly, but the more difficult problem in using them is controlling the voltage across the range of power output as they want to transfer charge naturally on an exponential curve. Supercapacitors will probably be great for rapidly accumulating and discharging energy very rapidly (e.g. for brake regeneration or as a charge accumulator for managing loads across electric motors to improve efficiency) but I am highly doubtful that they’ll serve as a replacement for batteries. Stranger [Previous page](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536.md?page=1) [Next page](https://boards.straightdope.com/t/is-there-any-battery-chemistry-that-can-compete-with-gasoline-on-energy-density/713536.md?page=3)