Solid-state batteries are becoming the next big thing in energy storage, with the promise of low volatility, high energy density and lower-cost manufacturing.  With academia, industry and government collaborating on the next wave of development, we may see progress in this realm.

Recently, the Department of Energy’s Oak Ridge National Laboratory and Solid Power Inc. of Louisville, Colo., signed an exclusive agreement licensing lithium-sulfur materials for next-generation batteries.

Rather than sloshing around in aqueous electrolyte, anodes and cathodes press against solid electrolyte

Rather than sloshing around in aqueous electrolyte, anodes and cathodes press against solid electrolyte

A team of current and former ORNL researchers including Chengdu Liang, Nancy Dudney, Adam Rondinone, Jong Keum, Jane Howe, Wujun Fu, Ezhiylmurugan Rangasamy, Zhan Lin and Zengcai Liu developed the technology.  This included designing and testing an all-solid lithium-sulfur battery “with approximately four times the energy density of conventional lithium-ion technologies.”  It featured a “new Oak Ridge-designed sulfur-rich cathode and a lithium anode with a solid electrolyte material, also developed at ORNL.”

Oak Ridge has also licensed a method of forming lithium-containing electrolytes using wet chemical synthesis, which may comprise β-Li3PS4 or Li4P2S7.

Reportedly, Solid Power will use this technology to develop solid-state rechargeable batteries with two to three times the energy of conventional lithium-ion technologies, and an absence of lithium-ion volatility.  Such batteries should be less expensive to manufacture since they can dispense with “many of the expensive safety features typically associated with lithium-ion systems.”

Solid Power will leverage industry standard manufacturing processes to bring the battery to market, using a simple battery cell architecture that will rely on a 700-square foot dry room facility with roll-to-roll processing that can scale up to production capabilities.  They hope to be in production by year’s end.

ORNL research and development on the lithium-sulfur materials was supported by DOE’s Office of Science and the Vehicle Technologies Office in DOE’s Office of Energy Efficiency and Renewable Energy. Materials synthesis and characterization were conducted in part at ORNL’s Center for Nanophase Materials Sciences, a DOE Office of Science User Facility.

Solid-state batteries have been running on the streets of Paris for years in Bollore' Blue Cars

Solid-state batteries have been running on the streets of Paris for years in Bollore’ Blue Cars

Perhaps surprisingly, vehicles with solid-state batteries are now plying city streets.  AutoLib, a car-sharing service similar to Car2Go and others, has been running in Paris for several years and now has 3,000 cars and over 20,000 subscribers.  It now operates in London as Bluecars with an initial batch of 100 cars and in Indianapolis, Indiana under the BlueIndy name.  Five cars are currently operating in this country.

The Bollore’ Group, headquartered in Paris, runs their cars on Bollore’ designed battery packs, the first plug-in vehicles to run on solid-state rather than liquid electrolyte batteries.

Early indications are that these batteries are relatively trouble free.  BlueIndy president Hervé Muller says, “We haven’t had an issue in Indianapolis, nor in Paris with the 3,000 cars in service there that have driven more than 10 million miles.”  He points out that the batteries are early models not yet ready for the mass market.  Although they can power a small car for 240 kilometers (148 miles), they need to be warmed up first, taking some of their mileage potential away.

Others working on solid-state batteries, including the recent Seeo-Bosch acquisition and Ann Marie Sastry’s Sakti 3 operation, have not yet achieved vehicle scale systems.

Solid Power, though, “based in the Colorado Technology Center in Louisville and a spin-off from the University of Colorado at Boulder, says it has made lab-scale cells that have reached 400 to 500 watt-hours per kilogram, and up to 500 charging–discharging cycles of durability. Company founder Doug Campbell says that Solid Power is targeting the automotive sector, although its first market may be the armed forces, for use in communications equipment. ‘Troops in the field can carry 60 pounds of batteries, and if we can cut that in half, it’s a strong value proposition for the US military,’ he says.”

Since so many developers are studying the limitations and working to overcome them, these solid-state batteries may have a solid future in transportation.  2X or even 4X energy densities would certainly be welcome in aircraft.


Solar Impulse Down, But Not Out

Following its cliff-hangar five-day flight from Nagoya, Japan to Kalaeloa Airport, Hawaii, Solar Impulse is undergoing an extended period of tender loving care, dedicated rebuilding of its battery packs and insightful reflection on how to avoid future issues.

Landing July 3, 2015, Pilot André Borschberg broke the world records for distance along a course (6,825.4 kilometers – 4,231.5 miles), Straight distance, and Duration for solar aviation, as well as the world record for the longest solo flight ever (80 hours and 5,663 km. – 3,511 miles), according to the Solar Impulse web site.

If all had gone according to plan, Bertrand Piccard would have hopped on board a few days later and headed for the United States on the second leg of the trans-pacific part of the the team’s around-the-world voyage.  Unfortunately, the rigors of a test flight over Nagoya, followed by a climb to 28,000 feet too soon after that test flight, seems to have doomed at least some of the batteries.

Removing battery pack from SI2 gondola

Removing battery pack from SI2 gondola

Andre’ noted the rising temperatures in the battery packs on the first day’s climb, and doubtless had to treat the throttles on the big bird in a gingerly fashion every one of the four days following.  Even will all systems “go,” the airplane would greet the dawn with a minimal charge.  Andre’ had to monitor all systems with extreme care through the Nagoya to Hawaii leg.

Kokam, battery supplier for the flights, has produced the replacement pouch cells and they are now being “encapsulated” in special boxes with silver conductors and “a fail-safe system which should safeguard us from any more temperature-related glitches in case we have to follow a different mission profile than the one foreseen. It can be controlled from the cockpit and includes a cooling and backup system. In case the cooling system breaks down, the backup one steps in and allows the pilot to control the opening so that it doesn’t stay completely open, which would cause freezing, or closed, leading to another overheating scenario. Indeed, this could jeopardize the continuation of the flight which would be critical if the airplane was flying over an ocean.”

Newly designed airflow through nacelles and around battery packs

Airflow through nacelles and around newly designed battery packs and protective casing

Container boxes are being shock tested in Dubendorf, Germany and should be ready for the Kokam cells to be “boxed” by the end of this month, with final assembly and testing taking place in December.

After all has been assembled and tested, the battery boxes will be installed in the motor housing (or gondola), and finally hung on Solar Impulses’ wings.

Revised air inlet on gondolas

Revised air inlet on gondolas

We will all be awaiting the spring and the final legs of Solar Impulse’s epic journey.


In the meantime, Borschberg and Piccard will appear at the upcoming COP21 (Congress of Parties 21) a major event in trying to build global consensus on what to do about global warming.  In their typical fashion, they show positive alternatives to more onerous restrictions.

Dr. Piccard suggests seven ways to solve the problem, all with positive economic, social and environmental benefits for all.

  1. Highlight the solutions instead of the problems:

How can we motivate people against climate change if we continue to focus on the amplitude of the problem? The current discourse is depressing and makes the situation seem insurmountable. Mobilization will only become possible if we emphasize the tangible benefits of existing clean solutions: we can already cut CO2 emissions by half, when replacing old polluting devices in the field of industry, construction, heating, cooling, lighting and mobility with today’s energy-efficient technologies.

  1. Stop threatening human mobility, comfort and economic development in order to protect nature:

Asking people to make sacrifices for no immediate return only creates resistance. Who would renounce driving their car because of sea levels rising in 30 years? On the contrary, let’s demonstrate that everyone can maintain and even improve their standard of living thanks to affordable and accessible clean technology solutions, while at the same time reducing the impact of their lifestyle on the environment.

  1. Speak of profitable investments instead of expensive costs:

Protecting the environment should not be perceived as expensive. Because there is a need for more environmentally friendly products and processes, fighting climate change is opening-up new industrial markets and offering an opportunity for economic development, job creation and profit.

  1. Offer both rich and poor countries a share in the returns on investment:

If fighting against climate change is presented as a financial sacrifice for rich countries and a threat for the economic growth of developing countries, we will face opposition from the entire world. Investing in solutions, for energy efficiency and renewable energies, is profitable for investors and consumers in both rich and emerging markets.

  1. Refrain from setting goals without demonstrating how to reach them:  

When we hear politicians wanting to reduce CO2 emissions by X% or limit temperature increases to 2°C, it comes across as wishful thinking. Nothing will ever happen if they don’t also set out very clear legal framework, procedures and concrete technological solutions to realize these goals.

  1. Combine regulations with private initiative:

The unpredictability of legislations and the risk of competitiveness distorsion too often prevent the industry from spontaneously investing in a cleaner production. Our society has regulations for education, hygiene, health, justice, etc., but not for preventing the waste of energy and natural resources. This must change!

  1. Act in the interest of today’s generation and not only for future generations:

Very few people will change their current behavior in favor of those living in the future. Let’s demonstrate that the changes we need can already deliver a favorable result on today’s economic, industrial and political development.

As much for the success of their flight as for their influence on world leaders, we wish Andre’ Borschberg and Bertrand Piccard the best of luck.


Hybrid Quadrotor Can Stay Aloft 2.5 Hours

Richard Glassock did his graduate work on small hybrid gas-electric systems, and keeps your editor current on that part of the aeronautical power spectrum.  He recently shared one promising example of such technology in the drone market.  Where current quadrotors are limited in size, power, and flight duration, the Quaternium Hybrix 20 is larger, heavier, and can fly for up to 2.5 hours, according to its makers.  The, according to its Spanish maker Quaternium is six times the endurance of current camera-bearing drones.

Quaternium 20, 50, and 100 models showing relative sizes

Quaternium 20, 50, and 100 models showing relative sizes

The 20 weighs 11.3 kilograms (25 pounds) empty and can carry a 7 kilogram (15.4 pounds) payload.  It approaches the current limit on the Small Unmanned Aerial System (SUAS) of 25 kilograms (55 pounds) and does not exceed the 100 mph speed limit for such systems.

The video, judging from the size of the vehicle relative to the human starter and pilot, is the 20.  The 50 and 100 are proportional to their designation, based on the scaled drawings.  The largest grosses out at 100 kilograms (220 pounds), something at which the FAA will probably take a long look.

While current drones might be able to tote a GoPro for a short photo-shoot, the largest of the Quaternium machines could probably carry an IMAX camera over the restaging of Waterloo.  From the noise of the gasoline engine, though, camera operators will have a hard time sneaking up on the elusive ibex, and Julie Andrews would have to lip-synch while frolicking around the alpine meadows.

Spidex Pro is more closely related to hobby-type quadrotors, but with sophisticated gimbal mount for cameras

Spidex Pro is more closely related to hobby-type quadrotors, but with sophisticated gimbal mount for cameras.  It is all-electric with much more limited endurance than Hybix models

The company’s smaller Spidex camera vehicle carries a smart-phone-based lens or other small cameras and a limited payload that would preclude anything heavier.  The maker’s description suggests a difference from lesser quadrotors.

“Spidex PRO has a noble and accurate way to be piloted. Its clever design, with the gimbal stabilization device on the front and the center of gravity at the same height of the propeller thrust, avoids the pendulum or inertial effect that other devices suffer. The centered masses give that fast and precise pilotage that allows [it] to take very dynamic scenes, with speed and quick response to avoid obstacles.”

Designer J. L. Cortex is founder of Quaternium Technologies and is noted as “one of the pioneers in the field of multirotor engineering.”  We look forward to seeing more complete specifications and a more detailed description of the hybrid system employed.


Second Sunseeker Duo Calendar Here

Eric Raymond, designer and builder of three solar-powered aircraft, along with his wife Irena, take some pretty astonishing pictures.  They work from a unique aerial platform, the Sunseeker Duo they completed and now fly together.  Their travels and adventures are large-screen worthy, and they share them with their 2016 Calendar.  Eric explains.

Dear Solar Flight and glider fans,

We had the most amazing year ever flying the SUNSEEKER DUO here in Europe and we would love to share the vistas with you!

Just now we are finishing our photo calendar in time for Christmas, and offering it for anyone’s gift to a pilot or themselves.

Since our flight in the SUNSEEKER DUO to the Swiss Alps was very successful and picturesque, most of the images are from that adventure this last August.

(Editor’s Note: the preview here is but a hint of the full glory of the final product.  Your editor receives no freebies, but gladly pays full price for the privilege of hanging one on his wall.)

sunseeker Calendar preview small

This year we are using offset printing for the best possible photo quality.  In addition, the backs of the pages have black and white photos and text, to give some background into the aircraft.

The size is considerably larger than last year, 495 mm – 410 mm (19.5 x 16.2 inches) , but still small enough for a small space on the wall.

Discounts are available for quantity orders.

Please follow the link to order it now and get it before Christmas.


Better, Cheaper, Faster.  That was the mantra when your editor worked in the semiconductor manufacturing world.  Designs, processes and materials were all recalibrated constantly to enable the march toward those three goals.  And to some extent, constant repetition helped us achieve the ideal of Moore’s Law, the dictum that computer chips would double the number of transistors they contained every two years.  Transistor density in computer chips determines the level of performance they can achieve, and this doubling has yet to reach its end.

Unfortunately, batteries haven’t doubled in performance every two years, but seem to follow an annual five-to-eight-percent increase in energy density.  This would mean, at best, that energy densities would double every nine years.  The Tesla Forum notes this progress would not be continuous, but introduced in steps.

Without either party sharing much information on the energy densities of their experimental cells, researchers in America and Switzerland find the “super environmentally friendly” nature of fool’s gold in batteries readily apparent.  One uses nanocrystals of the material, the other quantum dots.

Empa – Swiss Gold

Empa, “the Swiss Federal Laboratories for Materials Science and Technology, is part of ETH Zurich,  one of the world’s leading universities for technology and the natural sciences.  Empa researchers, working from the premise that lithium, the most common basis for high-energy batteries, is in short supply and therefore tending toward being more costly.  To counter scarcity and cost, they’ve devised their “fool’s gold battery,”

Maksym Kovalenko, Marc Walter and their colleagues at Empa’s Laboratory for Thin Films and Photovoltaics have combined a magnesium anode with an electrolyte made of magnesium and sodium ions. The cathode is nanocrystals made of pyrite (fool’s gold).

Empa's fools gold battery

Empa’s fools gold hybrid battery with magnesium anode and iron pyrite cathode.  Illustration: Empa

Because pyrite is crystalline iron sulfide, the electrolyte’s sodium ions flow to the cathode during discharging. During recharging, the pyrite re-releases the sodium ions.

A lab-based product so far, the battery has made it through a mere 40 charging-discharging cycles, but still has several potential advantages worth exploring.  The magnesium anode is far safer than highly flammable lithium according to researchers (not that magnesium fires are all that easy to extinguish). The research team thinks the best feature is that “Ingredients for this kind of battery are easily affordable and in plentiful supply: Iron sulfide nanocrystals, for instance, can be produced by grinding dry metallic iron with sulfur in conventional ball-mills. Iron, magnesium, sodium, and sulfur… hold 4th, 6th, 7th and 15th place by the abundance in the Earth’s crust (by mass). One kilogram of magnesium costs at most four Swiss francs, which makes it 15 times cheaper than lithium. There are also savings to be made when it comes to constructing the cheap batteries: Lithium ion batteries require relatively expensive copper foil to collect and conduct away the electricity. For the fool’s gold battery, however, inexpensive aluminum foil is perfectly sufficient.”

Empa scientists don’t see this as an EV battery – its output is too low.  Cost and environmental friendliness make the technology a winner for large, stationary plants, though.  The researchers’ paper in the journal, Chemistry of Materials, suggests using such a battery to temporarily store the annual production from the Swiss nuclear power station in Leibstadt, for instance.  Perhaps a lighter, longer-lasting battery is possible.

Kovalenko suggests, “The battery’s full potential has not been exhausted yet.  If we refine the electrolytes, we’re bound to be able to increase the electric voltage of the sodium-magnesium hybrid cell even further and to extend its cycling life. We also look for investors willing to support research into such post-Li-ion technologies and bring them to the market.”

Vanderbilt University

Starting with an apparent flash in the pan, Vanderbilt researchers added quantum dots to a smartphone battery, enabling it to charge in only 30 seconds.  Unfortunately that only lasted a few charges.  Making iron pyrite quantum dots, nanocrystals 10,000 times smaller than the width of a human hair, and adding millions of those to the same phone battery caused it to charge quickly and last dozens of cycles – still nowhere near the longevity of commercial cells.

The team headed by Assistant Professor of Mechanical Engineering Cary Pint and led by graduate student Anna Douglas reported on this in the November 11 ACS NanoLike the Empa reseachers, they were drawn to the abundance and inexpensive nature of the material.

Cary Pint and Susan Douglas search for fools gold

Professor Cary Pint and graduate student Anna Douglas size up benefits of fools gold.  Photo: John Russell, Vanderbilt University


Sizing the particles was a major problem, though, and lack of longevity also plagues Vanderbilt’s initial effort.  Pint explains, “Researchers have demonstrated that nanoscale materials can significantly improve batteries, but there is a limit. When the particles get very small, generally meaning below 10 nanometers (40 to 50 atoms wide), the nanoparticles begin to chemically react with the electrolytes and so can only charge and discharge a few times. So this size regime is forbidden in commercial lithium-ion batteries.”

Despite all their promise, researchers have had trouble getting nanoparticles to improve battery performance.  They added millions of iron pyrite quantum dots of different sizes to standard lithium button batteries normally used in watches, automobile key remotes and LED flashlights.  Most successful were those about 4.5 nanometers in size, “substantially” improving cycling and rate capabilities.

Distribution of nanoparticle sizes in Vanderbilt battery

Optimum-size quantum dot, about 4.5 nanometers.  Distribution of nanoparticle sizes in Vanderbilt battery

According to Douglas, iron pyrite has a unique way to changing form into an iron and a lithium-sulfur (or sodium-sulfur) compound to store energy.  “This is a different mechanism from how commercial lithium-ion batteries store charge, where lithium inserts into a material during charging and is extracted while discharging — all the while leaving the material that stores the lithium mostly unchanged,” she explained.

Pint has a culinary explanation.  “You can think of it like vanilla cake. Storing lithium or sodium in conventional battery materials is like pushing chocolate chips into the cake and then pulling the intact chips back out. With the interesting materials we’re studying, you put chocolate chips into vanilla cake and it changes into a chocolate cake with vanilla chips.”

Transformations like this don’t readily explain why the size factor for the nanoparticles is so important, “big” nanoparticles not working as well as “very small” nanoparticles.

Eschewing poetry for prose, Douglas explains further.  “Instead of just inserting lithium or sodium ions in or out of the nanoparticles, storage in iron pyrite requires the diffusion of iron atoms as well. Unfortunately, iron diffuses slowly, requiring that the size be smaller than the iron diffusion length — something that is only possible with ultrasmall nanoparticles.”

Bigger particles have a harder time fighting their way to the surface while the sodium or lithium reacts with the sulfurs in the iron pyrite.  That inability of the iron to move through the iron pyrite materials limits their storage capability.  Knowing just how big and small to make nanoparticles will affect how fast battery makers can trend toward Moore’s Law.

Pint concludes, “The batteries of tomorrow that can charge in seconds and discharge in days will not just use nanotechnology, they will benefit from the development of new tools that will allow us to design nanostructures that can stand up to tens of thousands of cycles and possess energy storage capacities rivaling that of gasoline.  Our research is a major step in this direction.”

Getting the basics down and making these batteries work as hoped is one thing.  Getting them light and energy dense for EV use is another – one which we hope researchers are able to solve.

Paper co-authors include mechanical engineering graduate students Rachel Carter and Adam Cohn and interdisciplinary materials science graduate students Keith Share and Landon Oakes. The research was funded in part by National Science Foundation grant EPS 1004083 and NSF’s graduate research fellowship program grant 1445197.


Richard Glassock, an Australian now working in Hungary, has been a presenter at an Electric Aircraft Symposium and received worldwide interest for his eight-passenger, open cockpit sailplane design a few years ago.

Single-engine Falco with 180-hp Lycoming

Single-engine Falco with 180-hp Lycoming

He writes today to share news about a twin electric motor conversion for a Falco, the great, high-speed craft by Italian Stelio Frati. Originally designed for four-cylinder, horizontally-opposed engines of up to 300 horsepower, the wood airframe was incredibly complex and required thousands of hours to construct. Signor Aldini reported taking 80 hours just to make the main spar’s jig – with four people needed to complete clamping before the glue set.

With the increasing difficulty of finding aircraft-grade sitka spruce or aircraft-grade wood craftsmen, those who can replace their time with money can purchase an all-carbon-fiber composite kit with qualifies under the FAA’s 51-percent rule – the homebuilder being responsible for 51 percent of the construction.  All kits for the airframe, firewall back, total over $92,000 (U. S. dollars).  This flies with the standard 150 to 180-hp Lycoming engine of the original.

Twin-motored Furio with YASA 150-hp units, contra-rotating propellers.  Note improved visibility, streamlining

Twin-motored Furio with YASA 150-hp units, contra-rotating propellers. Note improved visibility, streamlining

This New Zealand Falcomposite kit, renamed the Furio, is beautiful, a modern adaptation of a classic airplane. A British firm adds a thoroughly modern power system, two YASA motors driving twin contra-rotating propellers on a common axis. Nick Sills, the former technical director for the Electric Lightning P1 single-seat pylon racer, set up Contra Electric Propulsion (CEP) to develop the power system.

Nick told the English publication Flyer, “The CEP development is a bolt-on self-contained twin-engine contra-rotating fixed pitch 300hp system for existing piston engine light aircraft.” .

Nick adds, “The Furio is a carbon fibre monocoque airframe light enough to allow 400kg of battery to be added. We should get an endurance of about 1 hour. It’s a fantastic little aircraft but not at present certified for Europe.

Complete add-on nose cone contains motors in forward portion, batteries in cowling structure which mounts directly on firewall

Complete add-on nose cone contains motors in forward portion, batteries in cowling structure which mounts directly on firewall

“We plan to start ground testing the prototype this December and flight test in a Furio, in the third quarter of next year.”

Potenza Ltd, a Coventry-based company will develop the power system, a test rig, battery pack and ancillaries and instrumentation for ground tests, with delivery due in December.

Hercules Propellers in New Zealand will supply the contra-rotating propellers. They have recent experience with similar drive systems, having supplied the props for the Bugatti 100P project which recently flew in Texas.

Sills identifies several benefits of CRPS, and intends to make it available as a production power unit which can “easily replace a piston engine.

The twin motors allow reclassification of an airplane as a “twin,” although that may be only an English or UK consideration. Since the two motors are inline, there is no engine-out asymmetric flight characteristic to deal with, making for greater safety.

Complete 225-kW/300-hp power system weighs 265 kilograms (583 pounds) including batteries

Complete 225-kW/300-hp power system weighs 265 kilograms (583 pounds) including batteries

The twin motors and fixed-pitch propellers are simple, inexpensive (compared to a Lycoming engine), robust and maintenance free, according to Sills. The motor propeller combination has only two moving parts compared to the hundreds of a conventional four-cylinder engine.

CRPS claims, “Hugely improved performance. No propeller torque, better acceleration, higher speed, reversible thrust, huge range of power settings (a contra rotating fixed pitch propeller pair is more efficient than a single variable pitch propeller with the same horsepower)”

The 30-percent smaller overall propeller diameter gives better ground clearance and shorter undercarriage.

With silent operation, no toxic exhaust, and low vibration, flight should be less taxing than with conventional power plants.

CRPS claims “very low maintenance costs” with almost no maintenance, and 10,000 hours between overhauls.

Direct operating costs should be lower; with an electric recharge about 7 percent of the cost of piston engine fuel, oil and other consumables, mile for mile.

The small size of the propulsion system has a huge effect on the shape/profile of the aircraft nose, improving the aerodynamics. It should lower cooling drag significantly, as

Sills acknowledges “The present downside of pure electric flight is the 20 times greater energy provided by a similar weight of hydrocarbon fuel – however, huge resources are being ploughed into battery technology world-wide and it can be expected the that this energy density gap will rapidly close.”

CRSP’s new motor package may add luster to the sterling international reputation of this classic airframe, and present an inspiration for owners of other high-performance homebuilts to convert to electric flight.


Dr. Seeley Resigns from CAFE Foundation

The CAFE Foundation released this announcement this week.

“Dr. Brien Seeley has tendered his resignation as President and Board Member of CAFE Foundation.

“CAFE Foundation thanks Brien for his 34 years of leadership and wishes him continued success in his new aviation endeavors. We are confident that his boundless energy and inspiration will cause great new projects to take shape and blossom under his stewardship.”

{ 1 comment }

Cambridge University researchers claim to have successfully demonstrated how several of the problems impeding the practical development of the so-called “ultimate” battery, in this case a lithium-oxygen unit, could be overcome.  They make some pretty impressive claims, saying they’ve developed a working laboratory demonstrator with “very high” energy density – comparable to that of gasoline and with greater than 90-percent efficiency, and the ability to be recharged more than 2,000 times, or 5-1/2 years with a complete cycle and recharge every day.

A lithium-oxygen or lithium-air battery of this type would allow an uninterrupted drive between London and Edinburgh on a single charge, about 415 miles, over 100 miles greater than the top mileages promised by Tesla and GM at this point.

Cambridge "Ultimate Battery" under charge and discharge conditions

Cambridge “Ultimate Battery” under charge and discharge conditions

Researchers add the promise of one-fifth the cost and one-fifth the weight of currently available batteries – a touchstone for electric aircraft designers, and close to the goals U. S. Energy Secretary Steven Chu asked for three years ago.

Perhaps some of that weight difference comes from the “fluffy” nature of the electrodes, a frothy combination of graphene and “additives that alter the chemical reactions at work in the battery, making it more stable and more efficient.”

"Fluffy" electrodes, composed of one-atom thin layers of graphene

“Fluffy” electrodes, composed of one-atom thin layers of graphene

At this stage, the good news – that the basic premise seems to work as promised – is countered by the bad news that commercial, “practical” lithium-air battery is still “at least” a decade away.  (Wait a minute, where is the traditional message that the new invention is five years away?)

Professor Clare Grey of Cambridge’s Department of Chemistry explains, “What we’ve achieved is a significant advance for this technology and suggests whole new areas for research – we haven’t solved all the problems inherent to this chemistry, but our results do show routes forward towards a practical device.”  Grey, a Fellow of the Royal Society, uses advanced techniques such as nuclear magnetic resonance imaging to better view and understand the inner workings of lithium batteries, hoping to find ways to make batteries as much a part of electronics progress as other components.  Her group notes, “Many of the technologies we use every day have been getting smaller, faster and cheaper each year – with the notable exception of batteries.”

Dr. Grey’s co-author on their Science paper, Dr. Tao Liu, explains, “In their simplest form, batteries are made of three components: a positive electrode, a negative electrode and an electrolyte.”

In commonly used Li-ion batteries the positive electrode is made of a metal oxide, such as lithium-cobalt oxide, the negative electrode is made of graphite, and the electrolyte is a lithium salt dissolved in organic solvent.  Even though they are light and energy dense, their “relatively low” energy densities require frequent recharging.

In many attempts at developing better batteries over the past decade, researchers have been developing various alternatives to Li-ion batteries, and lithium-air batteries are considered the ultimate in next-generation energy storage, because of their extremely high energy density. However, previous attempts at working demonstrators have had low efficiency, poor rate performance (the ability to charge and discharge quickly), unwanted chemical reactions, and the need to be cycled only in pure oxygen.

Grey and her team use a different chemistry that earlier attempts at a “dry” (non-aqueous) Li-air battery, using lithium hydroxide (LiOH) rather than lithium peroxide (Li2O2).    Using a highly porous form of graphene for one electrode, and adding water and lithium idodide as a “mediator” in the electrolyte, made their battery more stable after multiple charge/discharge cycles.  These approaches reduced the “voltage gap” between charge and discharge to 0.2 Volts, making for a more efficient battery.

That highly porous graphene electrode greatly increases the capacity of the demonstrator, although only at certain rates of charge and discharge.  Researchers need to find how to protect the metal electrode so it doesn’t form dendrites, which can cause batteries to explode if they grow too much and short-circuit the battery.

Maybe one of the biggest stumbling blocks is that so far, test batteries can only be cycled in pure oxygen, something hare to achieve in the polluted atmosphere we breathe daily.  The CO2, nitrogen and moisture we live in would harm the metal electrode.  Additionally, the demonstrator can only be cycled in pure oxygen, while the air around us also contains carbon dioxide, nitrogen and moisture, all of which corrode the metal electrode.

Even though Liu concedes, “There’s still a lot of work to do,” he thinks solutions are possible for all the problems, and “we’ve shown that there are solutions to some of the tough problems associated with this technology.”

The team acknowledges support from the US Department of Energy, the Engineering and Physical Sciences Research Council (EPSRC), Johnson Matthey and the European Union via Marie Curie Actions and the Graphene Flagship. The technology has been patented and is being commercialized through Cambridge Enterprise, the University’s commercialization arm.


EAS IX: Short Circuiting Batteries on Purpose

Recent news from the world of insurance claims adjustors brings us back to ways inspired battery designers might reduce or eliminate certain types of claims, and make electric flight safer. Even when international agreements don’t make progress along those lines.

Insurance Claims and international Agreements

With recent news of Federal Aviation Administration interest in lithium-ion batteries arising from fires caused by thermal runaways, shipments of large numbers of batteries may be banned.  Claims Journal, an insurance industry news line, quotes Angela Stubblefied, an FAA hazardous materials safety official, as saying, “’We believe the risk is immediate and urgent.’ She cited research showing the batteries can cause explosions and fires capable of destroying a plane.

“FAA tests show that even a small number of overheating batteries emit gases that can cause explosions and fires that can’t be prevented by current fire suppression systems. Airlines flying to and from the U.S. that accept lithium battery shipments carry 26 million passengers a year, Stubblefield said.”

This led to the U. S. to craft rules to be implemented in 2016 that will restrict shipments of lithium batteries, especially on passenger craft.   The International Civil Aviation Organization (ICAO) held a Dangerous Goods Panel meeting in Montreal from October 19 through October 30, with much consideration of shipping lithium batteries. Several organizations with different agendas meant only preliminary rulings were possible, with the majority of the panel recommending Li-ion batteries be shipped at no more than a 30-percent state of charge and limiting shipments of batteries to one specially-prepared package per aircraft.

Based on FAA tests that indication that Halon, the fire suppression agent used in passenger aircraft cargo compartments “may not be capable of suppressing a fire involving large quantities of lithium-ion cells,” Boeing and Airbus have recommended not hauling such batteries as cargo “until safer methods of transport are established.”

Citing safety concerns, United Airlines on Monday, March, 2, 2015, became the second major U.S. airline to announce it will no longer accept bulk shipments of rechargeable batteries of the kind that power everything from smartphones to laptops to power tools. (AP Photo/FAA, File)

Citing safety concerns, United Airlines on Monday, March, 2, 2015, became the second major U.S. airline to announce it will no longer accept bulk shipments of rechargeable batteries of the kind that power everything from smartphones to laptops to power tools. (AP Photo/FAA, File)

This recommendation may be moot, however, since “Congress has prohibited the FAA from acting on its own to bar the shipments to the U. S.  A 2012 law says the government can’t issue regulations related to lithium-ion battery shipments that are more stringent than ICAO regulations unless accident investigators can show that a plane was destroyed by a fire started by the batteries.”  Hard to do when the evidence is destroyed by the fire batteries might have started.  Although the IATA and ICAO support continued shipments, the International Federation of Air Line Pilots Association advocated a ban “until better packaging or other measures can be developed to reduce the risk.”

Since gaining international and organizational agreement on rules and safe handling practices seems to have some impediments, an engineering approach may help resolve at least some concerns.

An Engineering Solution?

Eric Darcy, NASA’s battery expert, has spoken at several Electric Aircraft Symposiums, detailing steps he developed in making and evaluating batteries that will be as intrinsically safe as possible.   His work with NASA has established his reputation as a battery guru, with work on spaceship and spacesuit battery packs, where failure is definitely not an option.

Extra-vehicular mobility unit battery, where failure is not an option

Extra-vehicular mobility unit battery, where failure is not an option

Eric’s presentation at this year’s Electric Aircraft Symposium gave an overview on how he developed means of preventing internal short circuits and spreading of overheating condition from one cell to others.  He’s been sharing these insights with Matthew Keyser and Ahmad Pesaran, researchers at the National Renewable Energy Laboratory as they worked on a means to test cells for internal short circuits, deliberately triggering them to find out how to avoid such hazards.

Eric Darcy’s driving driving factors, and those of co-researchers at NREL, Matthew Keyser and Ahmad Pesaran, are pointed toward testing “one of the most challenging failure mechanisms of lithium-ion (Li-ion) batteries—a battery internal short circuit (ISC).  The team found they could heat cells to induce internal shorts, running nichrome wires into nine cells in parallel and by heating the wires in the cells, heating the cells to induce an internal short.

They found that they could devise means to prevent internal or cell-to-cell propagation.  The latter can lead to thermal runaways that affect the entire battery pack, so need to be avoided at all costs.  Darcy found there is a need to space out cells to prevent such propagation, venting gases as quickly as possible and using mica sleeves in their setup to isolate gases.  He used another machinable glass ceramic, Macor®, which can be machined like plastics.  Such separators seem to insulate even in high temperatures.

Aluminum heat spreaders can diffuse heat to larger, and thus cooler, areas through control of the conduction path.  To help fire off things in controlled experiments, multiple triggers may be used to create an overcharge and explosive type failure, another reason to contain such events, whether intended or not, in structural foam to prevent side-wall blowouts.  That might lead to a 10 to 15 percent battery volume in the complete package, but good use of the precautionary principle, nonetheless.

In past work for NASA, Dr. Darcy has tested ways to instigate and prevent internal short circuits, working to make extra-vehicular assemblies (space suits) from having thermal runaways, nothing the average space-man or –woman would want to experience.  Part of Darcy’s approach is controlling manufacturing defects to a level beyond six sigma.  The 54 batteries in the EVA are made to incredibly tight specifications, then tested and matched to nearly identical characteristics.  The battery pack, according to what Darcy shared at lunch two years ago, is that the EVA pack does not rely on a battery management system for control.  Such processes are incredibly expensive and would make Nissan’s Leaf a luxury car.

NREL Senior Engineer Mathew Keyser holds a sheet of copper discs, one of the metal components that comprise the NREL Internal Short Circuit(ISC) device, capable of emulating latent defects that can cause escalating temperatures in lithium ion batteries and lead to thermal runaway. Industry can use the NREL ISC device to evaluate solutions intended to address this issue.   Photo by Ellen Jaskol, NREL

NREL Senior Engineer Mathew Keyser holds a sheet of copper discs, one of the metal components that comprise the NREL Internal Short Circuit(ISC) device, capable of emulating latent defects that can cause escalating temperatures in lithium ion batteries and lead to thermal runaway. Industry can use the NREL ISC device to evaluate solutions intended to address this issue. Photo by Ellen Jaskol, NREL

According to NREL, their emulation tool will help manufacturers ensure the safety and reliability of electric vehicle batteries and avoid unexpected failure mechanisms.  Dormant flaws in these batteries present cause for concern, since many failures after batteries have gone one for weeks or months with no apparent concerns.

A key result, according to NREL, is their “internal short device can be used to determine how specific changes to battery materials and design will affect safety and evaluate how a battery will react to a latent defect…  An emulation method was sorely needed to definitively pinpoint the cause of internal short circuits, prevent failures, mitigate their effects, ensure consumer safety—and, ultimately, put more electrified vehicles on the road.”  And, presumably, more electric aircraft in the air.


Biggest, Fastest 3D Printed Airplane So Far

Unveiled at the Dubai Air Show this week, the collaborative effort between Stratasys and Aurora Flight Sciences is the largest and fastest 3D-printed aircraft so far.  With a 9-foot wingspan and weighing 30 pounds, the unmanned aerial vehicle is also the first jet aircraft to be made through additive manufacturing.

Scott Sevcik with Aurora/Stratasys 3D-printed jet plane at Dubai Air Show

Scott Sevcik with Aurora/Stratasys 3D-printed jet plane at Dubai Air Show

80 percent by weight was made through the advanced process, the rest consisting of the engine, electronics and tires.  Because the airplane was designed in a collaborative computer aided design process, the parts could be printed in Stratasys’ facilities even though they were designed primarily in Aurora’s Virginia headquarters.

Besides saving weight, the process saves time, the complete aircraft going from initial idea to first flight in under nine months.

Scott Sevcik, aerospace and defense business development manager at Stratasys, and a recent presenter at the ninth annual Electric Aircraft Symposium, says, “Aurora wanted to look at the feasibility of producing a vehicle tailored to unique mission requirements.  They identified a set of performance parameters, then designed the outer mold line of a vehicle that would be ideal for meeting those mission parameters.”

Scott explained, “We looked at that outer mold line and asked, what is the optimum structure internally.  Instead of the ribs and spars of a more conventional structure, “a more organic structure” allowed light weight, stiffness and uncompromised outer geometry.

The 22 pounds-thrust King Tech turbine pushes the craft to 150 mph, but only for about five minutes – the endurance allowed by the small fuel tank.   Since the thrust vectoring metal exhaust nozzle had to withstand high temperature blasts, direct metal laser sintering (DMLS).  Laser sintering was used for the highly complicated fuel tank.  “It is conformal to the engine, so the turbine actually slides right through the fuel tank,” Sevcik explained. “It’s fully sealed, with complex pathways printed through the tank for wire routing.”

Aurora Dan Campbell with UAV in Utah desert

Aurora’s Dan Campbell with UAV in Utah desert. Stratasys used FDM, fused deposition modeling, to make the wings and fuselage, and three other techniques to make the remaining parts.

Sevcik sees the future possibilities of “tightly coupled” design and manufacturing, including larger scales of aircraft, optimum interior shapes and improved speed in making complex parts. “So vehicles can be tailored to mission requirements and be of ideal performance, rather than having a basic performance applicable to multiple missions.”

Sevcik and Dr. John Langford, CEO of Aurora, didn’t mention this latest breakthrough at EAS IX in May, but then the rapid pace of design and creation would barely have begun then.  At that point, Sevcik talked about making one-piece, light passenger seats for Airbus, barely a hint of what the companies would accomplish in the next several months.

Up to this point Southampton University in England had printed and flown an electrically-powered two-meter wingspan craft with much lower weight and performance.  This development is a great leap forward.