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Maxwell Technologies delivers first commercial application of Li-ion capacitor technology with CRRC-SRI in China

Maxwell Technologies, Inc., a leading developer and manufacturer of ultracapacitor-based energy storage and power delivery solutions, announced the first commercial application of lithium-ion capacitors, developed in conjunction with China Railway Rolling Stock Corporation (CRRC-SRI), China’s largest rail manufacturer. (Earlier post.)

The technology will be used for rapid energy regeneration in the trolley system in the capital city of Hunan province in China. Following last year’s announcement of Maxwell’s strategic partnership with CRRC-SRI to collaborate on developing next-generation capacitive energy storage solutions, this project is the first to leverage Maxwell’s new lithium-ion technology and validates its unique value proposition for rail applications.

Lithium-ion capacitors have emerged over the past few years as an approach to improve the energy density of ultracapacitors by combining a low potential Li-ion battery electrode (for example, insertion-type, pseudocapactive transition metal oxide and pre-lithiated carbon) and a high potential ultracapacitor electrode (typically commercial activated carbon).

The result is a wide cell potential window; however, operating at a wide cell potential window can be detrimental to cyclic stability—one of the hallmarks of ultracapacitors. Manufacturers thus pay close attention to electrolyte stability.

Maxwell’s lithium-ion capacitors deliver ultracapacitors’ high power density with lithium-ion batteries’ high energy density for onboard energy storage systems. Compared to traditional ultracapacitors, lithium-ion capacitors triple energy density and reduce the total weight of the energy storage system by 50%.

Lithium-ion capacitors can charge light rail vehicles in 30 seconds and keep them going for five to 10 minutes, ensuring the trolley will be able to restart quickly in constant stop-and-go traffic. The technology fulfills China’s rail requirements for energy savings and environmental protection.

CRRC-SRI will leverage lithium-ion capacitors for the Changsha Subway in Changsha, Hunan, as the single source of power for instant charging and discharging to propel the trolley.

As railways continue to be a dominant form of transportation in China, rail infrastructure increasingly needs dependable energy saving technologies. Maxwell Technologies’ lithium-ion capacitors fill that market demand today and ensure our trolleys are constantly moving. We’ve continued to place our trust in Maxwell and its energy storage expertise and look forward to working together to meet the needs of the growing China market.

—Liu Baoming, chairman of CRRC-SRI

The commercial use of lithium-ion capacitors represents a transformation in the energy storage industry and a significant opportunity for Maxwell to revolutionize the way power is distributed in rail applications in China. Maxwell’s lithium-ion capacitors are the perfect solution for the growing rail market. As demand for energy storage solutions increases, we believe there is a large opportunity to use the technology in even more applications, such as grid firming, wind pitch control and robotics, to drive future revenue growth.

—Dr. Franz Fink, president and CEO of Maxwell Technologies


  • Wee Siang Vincent Lee, Erwin Peng, Meng Li, Xiaolei Huang, Jun Min Xue (2016) “Rational design of stable 4 V lithium ion capacitor,” Nano Energy, Volume 27, Pages 202-212 doi: 10.1016/j.nanoen.2016.07.018

  • Taina Rauhala, Jaan Leis, Tanja Kallio, Kai Vuorilehto (2016) “Lithium-ion capacitors using carbide-derived carbon as the positive electrode – A comparison of cells with graphite and Li4Ti5O12 as the negative electrode,” Journal of Power Sources, Volume 331, Pages 156-166, doi: 10.1016/j.jpowsour.2016.09.010



At 3X energy storage for 50% less weight this could be called ultra capacitors breakthrough.

Could work well for garbage trucks, city e-buses, many heavy Shovel machines and other intermittent use vehicles.


If you can get 10 minutes range out of 30 seconds charging you'd think there would be many possible applications. I often wonder if it wouldn't be possible to have on-the-go recharging lanes along highways. Even if it had to be done at lower speeds it would probably be attractive at least for commercial applications.

Trevor Carlson

I wonder what the limit is for maximizing the charge rate through inductive charging systems.
Obviously trolleys and buses can integrate a pantograph but city cars cannot. Major Metropolitan areas (the people living in them) could benefit from transitioning from city buses with a limited routes to a networked solution moving smaller numbers of people as efficiently as possible from/to specific points.
My concept for the metropolitan transportation future is that autonomous taxis of all sizes (maybe even a few bus sized ones) could run 24/7 if just major intersections had a quick inductive charging rings integrated and every taxi had an energy storage medium such as the above Li-Ion Capacitor banks in parallel with a longer range/slower charging battery.
A networked fleet of such taxis could be used for buffering the grid (when plugged in) and enabling higher adoption rates of distributed renewable power sources and lower "base-load" power generation. (cost savings) The fleet could be deployed all at once for large events specific to the need reducing congestion by helping change people’s behavior (reducing parking near stadiums and infrastructure designed to handle so many vehicles at a time resulting in future cost savings). Smart phone apps with location services enabled would help match groups of people based on their real-time physical location as well as their destination and draw them to a common pick-up point. I'm thinking something like uber but with nearly free rates due to city funding. The solutions are synergistic such that the cost savings of the system pay for itself while simultaneously improving the living experience of people. More and better positive living experiences increases the tax base by drawing people together (towards metro areas instead of repelling them through negative experiences). Such a system/concept could be implemented over the course of a generation or two starting with small autonomous taxis and with minimal investment/tear-up to existing infrastructure.

Trevor Carlson

Changing people's inefficient use of capital (with personally owned automobiles used primarily in cities) is nearly impossible unless the alternative is so much better that the positive experience creates a paradigm shift.

Perhaps city dwellers could use car rentals for the occasionally necessary longer trip. Rentals are nice too because you get what you need, when you need it with no overhead cost-wise. A major metro city may need to sponsor a contract though to increase the available fleet available to the whole city on-demand instead of just the major airport to kick-start that paradigm shift. In this way, even cities like Detroit could be rejuvenated where the inherent high taxes actually become affordable due to the reduced cost of living and increase to quality of life.

Trevor Carlson

1st generation starting here-

Trevor Carlson

This technology would also be useful in enabling smaller planes to use electric motors turning propellers giving them extra power during take-off and then driven off a central Primary power unit similar to the APU during cruise. Assuming of course any risk of fire hazard is mitigated and the system weight still makes sense. This would make solar panels on planes a no-brainer for free additional range/increased payload.

Trevor Carlson

"Wireless re-charging technology to keep drones flying perpetually"

Trevor Carlson

I imagine a 300GHz receiver on the bottom of planes and cars could dump a lot of power into a vehicle using arrays of the proper frequency emitting diodes focused on the target of the receiver. Materials could be engineered/chosen to prevent or manage the heating issues at the interface. With high energy capacity capacitors such as the technology in the above article the charging even itself could happen quickly as the vehicle passes over the array.

Trevor Carlson

Anthony F

You guys are all wrong - you're thinking too big! 30 seconds of charge for 10-30 minutes of activity sound likes a great application for R/C cars and other entertainment devices. ;)


The capacitor only has a power density of 200 W/kg.  This is far lower than even old-design piston aircraft engines, which get on the order of 0.5 HP/lb, or 800+ W/kg.  Light aircraft would be better off switching to a Miller cycle with turbine energy recovery to improve efficiency and cut mission weight.


Top of the line batteries will soon (2025/2030 or so) go from 400W/Kg to close to 1000W/Kg. Combined with 200+W/Kg super caps for takeoff power, they could power small regional passenger planes with acceptable range.

They would also be very useful for large EV/FC trucks and locomotives.


engineer-poet is right, i told you that petroleum is better and cheaper. Stop trying to raise the price and lower the performance of my future car. Im here to shop for a brand new future car and im here to tell in advance what car i want to all manufacturers. I don't want to buy a limp electric car with lithium ion capacitors. I WANT a gasoline air pressure hybrid car where the exhaust pressure and heat are captured and re-use and recirculate many time, easilly over 200 mpg. Electric cars are inneficient because they are mobile and electricity is only good in FIXED situation because you don't have to have exhaust in home and factories and noise. Use electricity only for cleanliness and low noise by a direct connection to the grid and power plants. Use petroleum for all mobile high power application and flush the exhaust into the environment like all electric power plants do. Oppose that a bunch of freaks decide to operate a catastrophic energy transition all over the world backed by dangerously ignorant journalists and bloggers.


gor....the new 133 mpge Toyota Prius PHEV may be the closest unit to meet your specs and replace your k-car; but it will not do 200 pmge.

The same Prius PHEV with a near future more efficient, lighter 2X SS battery pack may probably do 150+ mpge?


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