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Toyota working on all-solid-state batteries as mid-term advanced battery solution; prototype cell with 400 Wh/L

Ragone plot showing various types of secondary batteries. An internal combustion engine and Toyota’s targeted “Sakichi battery” are added for reference. Toyota reports that it has developed prototype cells of all-solid-state batteries and Li-air batteries with energy densities of 400 Wh/L and 1000 Wh/L, respectively. Source: Iba and Yada 2014. Click to enlarge.

Toyota Motor, like many automakers and suppliers, is pursuing the development of Li-air batteries as a very high energy density technology that would enable battery-powered vehicles with a much greater range. In an invited presentation at the 17th International Meeting on Lithium Batteries (IMLB 2014) in Como, Italy, Dr. Hideki Iba from Toyota’s Battery Research Division and Dr. Chihiro Yada from Toyota Motor Europe’s Advanced Technology group noted that Li-air batteries—assuming the attendant issues are resolved—may not be commercialized until FY 2030.

Concurrent with its work on Li-air, Toyota is also pursuing the development of all-solid-state batteries, and has already developed prototype cells with an energy density of 400 Wh/L. These, the Toyota researchers noted (again, assuming development challenges are overcome), could be commercialized by FY 2020 and see subsequent substantial improvement by FY 2025. (Earlier post.)

Toyota has already built a prototype electric kick-board powered by a Toyota all-solid-state battery to confirm the research and demonstrate the major potential of the technology. Source: Yada and Brasse (2014). Click to enlarge.

As reported in a paper in ATZelektronik worldwide, the high energy densities and power ratings of the all-solid state technology offer great potential. With proven discharge rates of 50C, even a deployment to electric motorsports with subsequent technology transfer seems within reach, the authors of that paper noted.

Solid-state lithium-ion batteries, with higher volumetric energy densities than currently available lithium-ion batteries, offer other advantages as well:

  • Improved packaging efficiency, as the cell design can allow in-series stacking and bi-polar structures. High energy densities can be achieved by reducing the dead space between single cells.

  • Improved safety. There is no risk of leakage of a liquid electrolyte, and the inflammable and inorganic solid electrolytes have high thermal stability.

  • Long cycle life.

However, all-solid-state Li-ion batteries have suffered from limited power densities until recently. One of the critical reasons for the limited power density was due to the large lithium-ion transfer resistance at the interface between cathode and solid electrolyte, Yada and Brasse note in their overview paper in ATZ. Thus, one of the major efforts in solid-state development has been boosting the power density (as well as the ever-present quest to increase energy density).

Accordingly, researchers are working in three main areas:

  • Developing better lithium-ion conducting solid electrolytes. These solid electrolytes are oxide-based, sulfide-based, nitride-based, etc. Sulfide-based provide relatively high ionic conductivities; for instance Li10GeP2S12 (LGPS) shows ionic conductivity as high as 1.2 × 10-2 S/cm—comparable to those of organic liquid electrolytes.

    Researchers at Max Planck Institute for Solid State Research in Germany recently reported the development of two new ultrafast solid Li electrolytes which are based exclusively on abundant elements. Both compounds—Li10SnP2S12 and Li11Si2PS12 feature extremely high Li-ion diffusivities, with the Si-based material even surpassing the present record holder LGPS. (Earlier post.)

  • Designing improved electrode/electrolyte interfaces to reduce interfacial resistance. The interfacial modification will become increasingly important in all-solid-state batteries as well as in other next-generation batteries, Yada and Brasse note.

    In a separate paper presented at IMLB 2014, Dr. Yada and colleagues from Helmholtz Institute Ulm and the German Aerospace Centre (DLR) report on their development of a new, mathematically rigorous model for a Li solid electrolyte to gain knowledge about the space charge regions at the boundaries between active particles and the electrolyte.

  • Improving Li-ion conductivity in active materials. Ideally, a battery with high energy density has a thin electrolyte layer and thick electrodes densely packed with active material. To meet the requirements of next-generation batteries, researchers must improve the conductivity of electrode active materials.

All-solid-state lithium-ion battery has been considered as innovative new generation batteries despite their long history. However, there remain many issues to be solved and their practical application seems limited at the present stage. Needless to say, electrode/electrolyte interfaces are very important sites to start and carry out the electrochemical reaction. Using the latest technology including advanced analyses, nano-structural adjustments of the interfaces will become a clue and breakthrough to resolve many issues of innovative new generation batteries.

—Yada and Brasse (2014)


  • Hideki Iba and Chihiro Yada (2014) “Invited Presentation: Innovative Batteries for Sustainable Mobility,” 17th International Meeting on Lithium Batteries (IMLB 2014)

  • Stefanie Braun, Arnulf Latz, and Chihiro Yada (2014) “A Thermodynamically Consistent Model for Electric Double Layers in Li All-Solid-State Batteries,” 17th International Meeting on Lithium Batteries (IMLB 2014), MA2014-04

  • Chihiro Yada, Claudia Brasse (2014) “Better batteries with Solid-state instead of liquid-based electrolytes,” ATZelektronik worldwide Volume 9, Issue 3, pp 10-15 doi: 10.1365/s38314-014-0244-8

  • Noriaki Kamaya, Kenji Homma, Yuichiro Yamakawa, Masaaki Hirayama, Ryoji Kanno, Masao Yonemura, Takashi Kamiyama, Yuki Kato, Shigenori Hama, Koji Kawamoto and Akio Mitsui (2011) “A lithium superionic conductor,” Nat Mat. 10, 682–686 doi: 10.1038/nmat3066



Numerous high energy density battery technologies may be mass produced by 2020/2025 and many more by 2030/2035.

Electrified vehicles will become very competitive whenever battery technologies reach 400+ kWh/Kg. That may be what Toyota has been waiting for to produce BEVs.

At 800+ kWh/Kg, ICEVs will be on their quick way out.

Account Deleted

Harvey it is wh/l not wh/kg. Panasonic already sell 18650 cells at 730 wh/l so Toyota's prototype might be battery is no big news at all.



Henrik...I prefer Wh/Kg for e-energy storage density.

Not sure why this article mentioned Wh/L?


500 Wh/liter when coupled with 4.0 miles/KWh means:

16 gallons (3.8 liters/gallon) of batteries would yield

0.500 * 3.8 * 4.0 * 16 = 121 miles

ho hum


"Energy density is the amount of energy stored in a given system or region of space per unit volume or mass, though the latter is more accurately termed specific energy."



Wh/l??? LMAO!!!! Why don't you just say it: She's got a great personality! What does she look like? Seriously, she's got a great personality!

Either give the Wh/kg or admit you're not on the right track yet with a viable battery yet. LMAO!!!!

Roger Pham

Quotes from the article: "...the high energy densities and power ratings of the all-solid state technology offer great potential. With proven discharge rates of 50C, even a deployment to electric motorsports with subsequent technology transfer seems within reach,..."

"offer other advantages as well:

Improved packaging efficiency, as the cell design can allow in-series stacking and bi-polar structures. High energy densities can be achieved by reducing the dead space between single cells.

Improved safety. There is no risk of leakage of a liquid electrolyte, and the inflammable and inorganic solid electrolytes have high thermal stability.

Long cycle life."

If the solid-state battery can result in an HEV or PHEV with equal cargo space and curb weight to a comparable ICEV, with not too high a price tag, then that will be all it will take to launch HEV's and PHEV's into the mainstream whereby they can do a lot of GHG reduction.

Image a Camry hybrid or Fusion hybrid with the same trunk space as the non-hybrid version, yet having the ICE downsized to half, perhaps a 1.2-liter 3 cylinder due to having a 50-C battery...let's see, a 1.8 kWh hybrid battery capable of 50-C discharge, which will make the battery capable of 90 kW of power! So, a 50-kW engine coupled with a 90-kW electric drive train will give a total of 140 kW of power, or equal to current power rating, but the car will be a lot lighter, less expensive, and the much-downsized engine will raise the MPG higher still...The fuel tank size can be halved so that the fuel tank will be on one side under the rear seat and the battery will be along side on the other side under the rear seat and the whole trunk space will be available for luggage just as in the non-hybrid. The lightened engine and battery will allow the car to match the curb weight of the non-hybrid version, or even lighter still because the suspension, tires, brakes...can also be lightened up.
The hybrid version might not even cost more than than the non-hybrid due to engine downsizing and one cylinder fewer and lower-cost battery and lightened up structure...

Sometimes a little improvement can pay off big dividends, due to synergy of factors involved.


I don't agree with you on the engine downsizing if it's not plug-in hybrid. A 50 kW engine going up a highway hill would be very loud and high reeving. Even current Prius engine is not the best choice for going up the mountain, even at slow pace. With only 1.8 kWh battery capacity you can not rely on the long term power from it. In a hybrid battery is used at max power (EV boost) or under a very light load where ICE is not efficient.

Your concept would be great for moderate level road driving and for quick powerful overtaking, but it would be terrible for dynamic terrain on the highway.


The news here is Toyota is researching traction batteries and it would seem they are not just Fool cell people.

Roger Pham

Good point, GasperG.

Perhaps for mountainous roads, a 2-speed automated manual transmission between the HSD (Hybrid Synergy Drive) unit and the differential would be necessary. So, the high gear is straight thru, while the low gear is for extended climb upon an incline in order to avoid overheating of the HSD.

However, even that may not be necessary, since the HSD transmission is an e-CVT that can be designed to work with any engines of lower power, simply has to change the gear ratio to accommodate a smaller engine with lower torque by allowing the engine to rev faster at a given speed uphill. At the lower power output of the smaller engine, the HSD surely won't overheat because it is handling lower output.

However, please consider the fact that the Chevy Volt has a 60-kW engine, and the Chevy Volt weighs in at almost 3,800 lbs empty, while the Camry or Fusion hybrid that I have in mind will weigh barely over 3,000 lbs, or almost 800 lbs lighter. Surely, GM engineers have researched long and hard to come up with the hp of the engine.

Consider further that a 65,000-lb semi truck having a 400-hp engine, or 162 lbs/hp, while a 3,500-lb car with a 67 hp (50kW) has over 3x the power to wt ratio, 52 lbs / hp. They all share the roadway and highways. Slower vehicles will go on the right lane.


This could simply be the typical Toyota press strategy we've come to expect. "We're nowhere... we're nowhere... we're nowhere..." and then all of a sudden "oh by the way our new lithium-air battery will debut in next year's Prius"

Roger Pham

So, while the 65,000-lb semitruck is laboring at low gears to climb uphill at 22 mph, the 67-hp Camry hybrid can zip right by at a nifty 66 mph due to having over 3x the hp/wt ratio...well, may be a little slower due to air friction drag...may be around 50-55 mph...but, hey, the slope must be really steep for a semitruck to climb at 22 mph.


It's not the transmission, it's Atkinson cycle engine. It needs to rev to get to the power. 1.8 Prius engine must rev at 3.000 rpm to produce 34 kW, a normal 1.3 engine is capable of that. This high reving is just very annoying for the driver, nothing else.

A truck has bigger engine with more torque, power rating of the engine does'n reveal that eg. 80% of that power is available at just 2.500 rpm, this makes it a very pleasing experience under constant load up the hill.

Power increase with higher revs in Prius engine is huge compared to a normal car or not to mention turbo charged engine, that can get you almost the same power no mater in what gear you are.


This battery may be able to supply 400 Watts for one hour with a volume of one L (400 Wh/L) and could charge/discharge at 50C rate, but what would be the density of the energy (Wh) stored per Kg of weight?

Since this battery probably weights a lot more (i.e 2X+?)than 1Kg/L, the specific energy density is probably well below 200 Wh/Kg. That would not be the ideal battery for extended range BEVs.


It seems like Toyota is letting everyone else make gradual improvements while they "swing for the fence" so to speak. I wish them well. Lithium polymer batteries use solid electrolyte, but require warmer temperatures to perform. Toyota may run into situations that they do not anticipate.

Roger Pham


Lithium ion batteries typically has specific gravity of around 2.5. So, 400 Wh/L divided by 2.5 will get you around 160 Wh/kg. Not great as battery for BEV, and just adequate for PHEV, but GREAT for HEV battery, at 50 C and ~160Wh/kg, to replace the NiMh battery right now which is capable of only 20 C and 35Wh/kg. This has 2.5x the power and 4x the energy density of existing NiMh batteries in Toyota's HEV's. Along with engine downsizing and wt reduction from lighter battery pack, we can expect future Toyota's HEV's to be hundreds of lbs lighter and will have significantly improved MPG both from engine downsizing AND from lighter weight. We would expect that HEV's market penetration will be much higher and this, along with significantly improved MPG's, will result in significant reduction in GHG of future automobile fleet.


Sorry that the Prius engine sound is annoying to you. My personal experience is that the Prius' engine's sound is barely perceptible and there is no vibration from the engine whatsoever, at all engine rpm's. If the engine is to be downsized to 1.2 liter, perhaps the sound level will be even lower.


Yes RP, the high power handling capacity of this battery make it well suited for HEVs. Yes, Toyota's HEVs would gain a lot when the current outated NiMH batteries were replaced with this unit.

Roger Pham

Another thought comes to mind: For the Camry hybrid's 1.8 kWh battery pack using the new solid state at 400Wh/liter, the total volume is about equal to that of a lead-acid car battery. This means that the 1.8-kWh solid-state battery pack can be placed under the hood in the same location of the lead-acid battery, with an insulation layer to keep the engine's heat out, and cooling air flow in and out to keep it cool using an electric fan. With the downsized engine, the engine bay will have plenty of space for the weekend mechanics to tinker with the engine.

With a downsized fuel tank have 1/2 capacity of the non-hybrid version, under the rear seat bench, the seat can be designed to fold forward and downward, while the back rest can be folded backward to provide a very generous, deep and wide contiguous space behind the front seats in the hatch-back version. This will exceed the cargo space of any comparable-size vehicle, including the trunk space of the non-hybrid version, and will accelerate sales further.

Indeed, Toyota and Ford should make a hatch-back version of the Camry and Fusion hybrids, respectively, using the new solid state battery pack and downsized engine to 1.2 liter 3 cylinder, while stop making the Prius V and Prius C as well as stop making the Ford C-Max hybrid, altogether! The potential hatch-back version of either Camry or Fusion hybrids will have roomier seating and more comfortable suspension while offering more cargo space behind the rear seats AND much better aerodynamics and looks a lot better to improve both MPG and sale volume and profit!

The hatch-back version will share almost all components with the sedan version, thus reduce inventory cost when other models such as the ungainly C-Max and Prius V are dropped from the list.


Is Toyota (and Ford +++)mmtaking note?

Roger Pham

Perhaps Toyota already have all these planned, thus explaining their enthusiasm about a 400Wh/liter battery that does not seem at first to be a major advancement. The potentially much higher safety of the solid-state battery is another essential requirement before Toyota's mass adoption of Lithium battery.


@Roger Pham

I like Prius, I own it for 3 years now, but you can't deny that there is no room for improvement ;)

Roger Pham

Well, the Prius can and will be much improved. Let's see, SiC inverter, Solid State battery, 42%-efficient engine using higher compression ratio permitted by extra-cooled exhaust valve area, more weight reduction from more composites, more aluminum and high-strength components, etc...all these are in the work and to be delivered.

Roger Pham

I was just suggesting to drop the Prius V and substitute with the Camry hatchback instead, while keeping the regular Prius as an all-time hybrid icon.


I have to agree with GasperG on this one. I like the Prius and it's a great car. But the power is lacking and the poor engine sounds like it's dying when you really have to gun it or go up a steep hill.
We took a trip in my mom's Prius this weekend to a family reunion and my brother and I thought the transmission was slipping or something. But my mother assured us that it always sounds/feels like that if you're on the highway and gun it to pass another vehicle at high speeds and you have to allow plenty of room. So there is essentially NO PASSING cars on a 2 lane highway on those South Alabama "freeways".

You're essentially stuck behind some old farmer in his 1970 pickup until he turns somewhere in the next 20 miles. Oh, you can pull out and TRY...but by the time you get up to speed, you're coming up to the next blind curve and have to jump back in line. LOL

Roger Pham


What version is your mom's Prius?
For the Prius Gen 3, the acceleration time from 0-60 is around 9 seconds. Check out this video on the following link, in which the acceleration starts at 7 second into the movie, and got to 60 mph at 16 second into the movie, so around 9 seconds net time.

By comparison, my Chevrolet Caprice 1978 felt to be pretty fast w/ 0-60 times around 12 seconds, and was able to do a pass easily on 2-lane rural hwys. The Honda Civic 1980 was pretty fast at 12 seconds from 0-60, and the Nissan 280Zx sport car got around 10.5 seconds from 0-60. The 1988 Camry V6 was really sporty with a 155-hp engine and can do 0-60 in 9 seconds!

Try to take a video of your mom's Prius 0-60 times like in the video to see how fast it would take. For the Prius Gen 2, it should be around 10.6 seconds 0-60. Any slower, and perhaps the car needs a tuneup, perhaps spark plug change, perhaps check the OBDII to see any fault code. Perhaps change the air filter, check tire inflation,...etc

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