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24M emerges from stealth mode with new semi-solid Li-ion cell; <$100/kWh by 2020

Stealth-mode battery start-up 24M has introduced its new semi-solid lithium-ion cell. Co-founded by MIT’s Dr. Yet-Ming Chiang, 24M’s Chief Scientist, the company is leveraging existing, preferred energy storage chemistry but using a new cell design with semi-solid (a mixture of solid and liquid phases) thick electrodes and manufacturing innovations to deliver what it says will be up to a 50% reduction in current Li-ion costs. (Dr. Chiang was also a co-founder of A123 Systems; 24M originated as an A123 spinout. Earlier post.)

Together, our inventions achieve what lithium-ion has yet to do—meet the ultra-low cost targets of the grid and transportation industries. By 2020 our battery costs will be less than $100 a kilowatt-hour (kWh). We’re emerging at the right time with the right technology,” said Throop Wilder, 24M CEO.

Until now, the energy storage field has had two options to try to drive down costs—high volume production or entirely new chemistries that may never move from the lab to the commercial floor. 24M says it is presenting a third option.

The lithium-ion battery is a brilliant, enabling technology, but its economics are flawed. It’s prohibitively expensive; it’s cumbersome and inefficient to make; and today’s version is approaching the limits of its cost reductions. 24M has fixed the flaws. We’ve made the world’s favorite battery better, fundamentally changing its cost curve by designing a more elegant and simpler cell and then making the batteries the right way—the way they should have been made from day one.

—Dr. Yet-Ming Chiang

Schematic of a 24M cell, from the patent. Click to enlarge.   24M cell compared to conventional Li-ion cell. Click to enlarge.

The semisolid thick electrode is a material science innovation originating in Dr. Chiang’s lab at MIT. Conventional lithium-ion battery cells have a large fraction of inactive, non-charge carrying materials—supporting metals and plastics—that are layered, one-on-top of the other, within a cell’s casing. Those inactive materials are expensive and wasteful.

With the invention of the semisolid thick electrode, 24M eliminates more than 80% of these inactive materials and increases the active layer thickness over traditional lithium-ion by up to 5x. As described in the patent “Semi-solid electrodes having high rate capability”, published 31 March 2015:

Furthermore, known conventional batteries either have high capacity or high rate capability, but not both. A battery having a first charge capacity at first C-rate, for example, 0.5 C generally has a second lower charge capacity when discharged at a second higher C-rate, for example, 2 C. This is due to the higher energy loss that occurs inside a conventional battery due to the high internal resistance of conventional electrodes (e.g. solid electrodes with binders), and a drop in voltage that causes the battery to reach the low-end voltage cut-off sooner. A thicker electrode generally has a higher internal resistance and therefore a lower rate capability. For example, a lead acid battery does not perform well at 1 C C-rate. They are often rated at a 0.2 C C-rate and even at this low C-rate, they cannot attain 100% capacity. In contrast, Ultracapacitors can be discharged at an extremely high C-rate and still maintain 100% capacity, however, they have a much lower capacity then conventional batteries. Accordingly, a need exists for batteries with thicker electrodes, but without the aforementioned limitations. The resulting batteries with superior performance characteristics, for example, superior rate capability and charge capacity, and also are simpler to manufacture.

Semi-solid electrodes described herein can be made: (i) thicker (e.g., greater than 250 μm-up to 2,000 μm or even greater) due to the reduced tortuosity and higher electronic conductivity of the semi-solid electrode, (ii) with higher loadings of active materials, and (iii) with a simplified manufacturing process utilizing less equipment. These relatively thick semi-solid electrodes decrease the volume, mass and cost contributions of inactive components with respect to active components, thereby enhancing the commercial appeal of batteries made with the semi-solid electrodes. In some embodiments, the semi-solid electrodes described herein are binderless and/or do not use binders that are used in conventional battery manufacturing. Instead, the volume of the electrode normally occupied by binders in conventional electrodes, is now occupied by: 1) electrolyte, which has the effect of decreasing tortuosity and increasing the total salt available for ion diffusion, thereby countering the salt depletion effects typical of thick conventional electrodes when used at high rate, 2) active material, which has the effect of increasing the charge capacity of the battery, or 3) conductive additive, which has the effect of increasing the electronic conductivity of the electrode, thereby countering the high internal impedance of thick conventional electrodes. The reduced tortuosity and a higher electronic conductivity of the semi-solid electrodes described herein, results in superior rate capability and charge capacity of electrochemical cells formed from the semi-solid electrodes. Since the semi-solid electrodes described herein, can be made substantially thicker than conventional electrodes, the ratio of active materials (i.e., the semi-solid cathode and/or anode) to inactive materials (i.e. the current collector and separator) can be much higher in a battery formed from electrochemical cell stacks that include semi-solid electrodes relative to a similar battery formed form electrochemical cell stacks that include conventional electrodes. This substantially increases the overall charge capacity and energy density of a battery that includes the semi-solid electrodes described herein.

—“Semi-Solid Lithium Rechargeable Flow Battery”

As described in the patent, the semi-solid electrodes can be a flowable semi-solid or condensed liquid composition. “Semi-solid” refers to a material that is a mixture of liquid and solid phases—e.g., particle suspension, colloidal suspension, emulsion, gel, or micelle. “Condensed liquid” refers to a liquid that is not merely a solvent, as in the case of an aqueous flow cell semi-solid cathode or anode, but rather is itself redox active. Such a liquid form may also be diluted by or mixed with another, non-redox active liquid that is a diluent or solvent, including mixing with such a diluent to form a lower-melting liquid phase, emulsion or micelles including the ion-storing liquid.

Using thick electrodes, the cell also stores more energy, bettering the performance of the battery as well as its cost. The materials design enables up to 5x the area capacity of standard Li-ion.

Manufacturing. The simplicity of 24M’s new cell design likewise begets a simplified advanced manufacturing process. The traditional method for making lithium-ion batteries takes days, is extremely capital-intensive and must run at high-volume to achieve economies of scale. 24M’s novel approach to manufacturing yields significant improvements:

  • Time. Start to finish, 24M’s cell creation takes one-fifth of the time of a conventional battery. Because semisolid lithium-ion doesn’t require binding, drying, solvent recovery or calendaring, it removes entire steps in the manufacturing process.

  • Cost. While the removal of manufacturing steps certainly contributes to lower capex, eliminating the need for entire plants makes semisolid lithium-ion ultra-low cost. A 24M factory requires about one-tenth the investment of a conventional plant.

  • Flexible and modular. Manufacturers can scale in small steps to match supply to demand, making lithium-ion cost effective even at low-volume production.

  • Environmentally friendly. 24M’s solvent-free manufacturing platform creates the most easily recycled lithium-ion cell ever made.

Since its founding in 2010, 24M has raised $50 million in private capital, closing Series A and B rounds, from Charles River Ventures, North Bridge Venture Partners and industrial partners. The company is also the recipient of a $4.5 million grant from the US Department of Energy. 24M’s cells are currently undergoing customer trials with large, global integrators of power systems for the grid. The company now employs more than 50 people and runs a fully automated manufacturing line from its 32,000 square foot facility in Cambridge, Massachusetts.


  • US Patent Nº 8,993,159: Semi-solid electrodes having high rate capability

  • Mihai Duduta, Bryan Ho, Vanessa C. Wood, Pimpa Limthongkul, Victor E. Brunini, W. Craig Carter, and Yet-Ming Chiang (2011) “Semi-Solid Lithium Rechargeable Flow Battery” Advanced Energy Materials doi: 10.1002/aenm.201100152



Lots of big claims. Wake me when the batteries start flowing off the production lines at half the price of Tesla's gigafactory.

Also no word on cycle life - the biggest issue for grid storage systems.

Also no word on energy or power densities the prime driver for automotive batteries.


Higher performance at much lower price is what extended range BEV manufacturers and buyers have been waiting for.

Hope that other battery manufacturers will take note and make the needed adjustments.

Anthony F

No specifics on what exactly these Li batteries would be suited for (grid storage, EVs, small devices, etc. - though the image in the linked press release seems to indicate a larger format for grid storage or EVs).

That said, they really don't need to improve on the performance characteristics of batteries of today by that much. The cells in the Tesla battery pack are 250Wh/kg and 700Wh/l, and an 85kWh pack can produce over 500kW of power (691hp in the P85D), and a pack life (to 80%) somewhere around 125,000 miles. Batteries that had those exact same characteristics but cost $100/kWh would still enable the widespread adoption of EVs - a 50kWh/200mi pack for a smaller car would cost $5,000 instead of $10,000+.

But one only needs to look at the curious tale of Envia, which promised us 400Wh/kg batteries by 2014 to know that the battery industry is susceptible to immense hype.


Just a comment out of the blue:
Interesting there has not been an EV battery fire story in the major media for a long time. Have they changed the chemistry or improved the BMS/charger systems?

If the Tesla battery is indeed 250 Wh/Kg; perhaps that's the answer to Nissan's next gen double range Leaf. their current battery is about 140 Wh/Kg and weighs 600 lbs. A half size Tesla battery would weigh about the same at twice the density of the current Leaf battery.


Interesting about vehicle fires. I see stories almost every day about horrific car, truck, or bus accidents where the vehicle is completely engulfed in a raging fire, and nobody seems to bat an eyelash (that there was a fire). The old double standard, I guess. And there are self-sealing fuel bladders used in race cars and fighter jets to prevent fires—no cry from legislators to require those in everyday vehicles. Hmm....


The article refers to this company as a "spinout" of A123. I believe the term is "spin-off", unless the principals are really spinning out of control with their ambitions.

Paste batteries are nothing new. Substantially liquid batteries may leak, corrode, or catch fire, contrary to implicit promises that the liquid will manage heat better than a solid state electrolyte.

For all the improvements over traditional lithium spelled out here, one might think that higher margins of improvement could be available with humbler materials like fluorine, lead, or magnesium.

And what is Tesla pushing on the American consumer with its household energy storage system? Simply this: a lower than automotive grade battery based on rejected materials or less-than-perfect specs. A buydown for sunken capital costs, and we think, a chance to use thousands of households as willing guinea pigs with a chance of a quiet exit ('Who Killed the Electric Car?').

Anthony F

Lad: I was quoting cell-level specifics. I think the 600lbs figure you quote is pack-level. So I don't think it translates over as easy as that.

I do think that the next Leaf will likely be around 250Wh/kg at the cell level (the battery in my iPhone 6 is 250Wh/kg!) but how well they construct their pack and the efficiency will determine how far it can go. I think they'll get somewhere around 150 miles (EPA) on a 42kWh pack.


No, I'm with you on cell specs...didn't mean battery specs. the 600 lbs figure is relative to the battery with assembled cells.

Nissan's goal as I understand it is to double current mileage, i.e., my car gets about 60-70 miles driving it in foothills so anything over 120 at the speed limits is a good improvement in the real world of everyday driving.

I just wish their initial offering had been a true and honest 100 miles at highway limits. I truly think they would have sold a lot more by now. Oh well, "If wishes were horses, all beggars would ride."


Hope it is not too late to halt the building of the gigafactory and redesign the manufacturing process...


Sounds like a great movie, but I think I'll wait and see it on Blu-ray...until I'm sure it's real


Impressive breakthrough. I hope they don't make the same mistake as A123 and restrict sales only to large OEMs. Imagine if Wilbur and Orville had not been able to buy key components and materials.

Require safety certification yes. But make these cells to small scale developers and we may all be surprised at what the next big application is.


If you would like a little more information on the 24M technology google "project ES071 Yet-Ming Chiang". This was DOE funded research that completed last year. There are 2 pdf files that outline 2011 and 2014 progress.


Lad: safety was never a real issue, or more precisely it was never much of an issue. In this world the average person can be made to fear nearly anything through media manipulation. The people with enough money can buy the message that comes through most media outlets. Car makers were worried about liability though since judges are also ignorant of technology and that whole system of justice as they call it is really a fear mongers paradise. But think about it, a battery has less energy than a tank of gas. All of the gasoline is flammable/explosive. Only part of the battery is flammable. The down side to batteries is that they can act as their own ignition source, but also have less energy. The gas tank needs an external ignition source, but once lite off is far more potentially dangerous. Labs that do safety testing for batteries are fear mongers because they want more work. Other industries fear the electrification of energy. So, here in the nation of fear mongers and the fearful, fear gets used to manipulate public opinion away from new tech to maintain business as usual.


Here is a informative article on the new production process for LIB.

Bob Wallace

The GigaFactory was designed from the ground up so that it could quickly/inexpensively move to a new type of battery if/when one proves out.

If Tesla/Panasonic moves away from wrapped cells to pouches/whatever it would mean scrapping some of their old tooling and bringing in new machines.

Tesla recently bought a factory that manufacturers industrial machines.


@ Gryf,

One of those PDF's says an objective was to "• Develop in-situ measurements of electronic and ionic transport vs. Li concentration using binder-free sintered electrode design" which is worrisome, because sintering does not lend itself to high-throughput production as the recent article claims. Maybe they moved on from that to their "wet" process. Laszlo's article says Lithium Iron Phosphate chemistry for stationary storage markets...which I guess makes sense, since Iron Phosphate was always about faster charge and recharge but sacrificing energy, make that cheap and yep, you get stationary storage. I guess other chemistries could be suitable for cars, but the stationary market is less demanding.


24M will initially use this process for standard Lithium Ion Chemistry, e.g. LiNMC or LiFePO4 - as HealthyBreeze illustrates. Since this is a process, as other chemistries are ready for production they can be adapted also. The process also works for Lithium metal anodes as well - ref: 24M patents. Note: Yet-Ming Chiang and Yi Cui (Stanford) recently published work on protecting the anode (see "Researchers find synergy between lithium polysulfide and lithium nitrate as electrolyte additives prevent dendrite growth on Li metal anodes" on this site).
Also, the best solution for a BEV may be a Sulphur-impregnated flow cathode using the 24M process once this chemistry gets to production ready status probably around 2020. It would be this configuration that would allow for production costs <$100/kWh and energy densities of >400 kW/kg.


Regarding cycle life

"outstanding cycle life and calendar life for grid or EV applications"

Not specific but very likely to be at least as good as current cells in use, probably better.


gryf...if a 400+ Wh/Kg battery can be produced under $100/kWh by 2020, competitive extended range BEVs would quickly push most ICEVs and HEVs out of the market place.

By 2025 or so, 600+ Wh/Kg batteries could spell the end of ICEVs, HEVs and PHEVs.

Bob Wallace

Harvey, your price point it too low. EVs grab the market away from hybrids and PHEVs at about $275/kWh. Tesla is already below that price.

At $130/kWh ICEVs would need <$2/gallon gas to stay in the game.

If Tesla and GM can put 200+ mile range EVs with 50 kWh packs on the road next year then we've got enough capacity. (More is always welcome.)


BW...your battery price point may be too high to compete against lattest 50 mpg ICEVs, specially in USA where gas is very cheap.

In EU, where gas cost a lot more, the break even price point may be anything under $200.


BW...your battery price point may be too high to compete against lattest 50 mpg ICEVs, specially in USA where gas is very cheap.

In EU, where gas cost a lot more, the break even price point may be anything under $200.

Bob Wallace

No, Harvey. Gas in the US, depending on the state, is running $2.41 to $3.46 per gallon.

"At $130/kWh ICEVs would need <$2/gallon gas to stay in the game."


BE....We all hope that your claims will become reality by 2020 or shortly thereafter.

More may have to be done to design and install quicker charging facilities, specially for near future 100 to 150 kWh extended range BEV battery packs.

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