OXIS Jump-Starts First Commercialization Of Lithium-Sulfur Batteries

More often revolutions start with a big bang but could it be the replacement for lithium-ion batteries is taking off with a relatively small but not insignificant pop?

This appears to be the case for OXIS Energy of the UK, which has plans in motion to put its 30-percent more energy dense polymer lithium-sulfur (Li-S) chemistry into production next year. Plans are also to sell its technology to European niche electric vehicle makers, the military, for solar energy storage systems, and several major auto manufacturers are in discussions with OXIS as well.

OXIS says its batteries are less costly to produce, lighter, safer, potentially more durable, maintenance-free and able to accept 100-percent discharge instead of the only 80-percent or so to which li-ion is limited.

battery_history

While the OXIS batteries do not yet boast headline-exploding four or five times lithium-ion’s energy density – though this is predicted – they do have enough superior about them to equate to a better battery than lithium-ion in several respects.

In so many words, even in its infancy, Li-S is a baby giant of a technology and able to pick up where the comparatively mature potential of li-ion first commercialized in 1991 by Sony is now tapering off.

Getting Started

In 2010 OXIS had just 10 employees, and now has 45. It’s based at the UK Atomic Energy Research Centre in Oxfordshire where lithium-ion batteries were first developed and prototyped. It holds 47 patents on its Li-S technology with over 32 more pending.

At the end of last month OXIS tweeted it had achieved a benchmark 500 charge cycles for its pouch cells, and yesterday it told us this is up to almost 600.

According to Dr. Mark Crittenden, OXIS’ business development manager, the company can reasonably extrapolate this result to say these same cells should be good for 1,700-1,800 charge cycles before they can only hold 80 percent, or “Beginning of Life.”

This was tweeted for OXIS' 200 Wh/kg pouch cells June 27. The line is now just about at 600 and OXIS is seeing 20 percent Wh/kg capacity improvement per year.

This was tweeted for OXIS’ 200 Wh/kg pouch cells June 27. The line is now just about at 600 and OXIS is seeing 20 percent Wh/kg capacity improvement per year.

“Having both high specific energy, excellent safety and good cycle life are key to why OXIS is now putting our cells into production early next year,” said Crittenden.

However, he says it’s yet questionable in the short term how suitable OXIS’ state-of-the-art is for “saloon cars” or passenger vehicles. These, he says would require 2,000-3,500 charge cycles based on commonly quoted European standards, but makers of electric utility vehicles, scooters, e-bikes, and even a small city car are planning to use its products as OEMs eye a technology predicted to be production-car ready not long after.

“With the improvement being made to the OXIS technology,” Crittenden said, “we expect to see our cells in the saloon car market in 3-5 years.”

Given these opportunities and others where Li-S can fill a niche, OXIS signed a contract at the beginning of this year with GP Batteries of Singapore. GP has several facilities in Asia, and is the largest consumer battery manufacturer in China. This will therefore be the first large-scale manufacturer to produce commercially available lithium sulfur cells – and it will save costs because OXIS uses a liquid gel electrolyte.

Since OXIS’ batteries are close enough in design to lithium-ion, GP will be able to use existing assembly line machinery to put the Li-S chemistry into production. This is a major hurdle that other Li-S battery chemistries – particularly solid-state type – will likely not be able to overcome, which effectively gives OXIS a nice head start.

Getting some of the first and best is that most famous of

Getting some of the first and best is that most famous of “early adopters,” the military. OXIS, PolyPlus and Sion are working on bleeding-edge projects. For example, PolyPlus has already demonstrated disposable Li-Air batteries with 800 Wh/kg and all are in process of delivering Li-S.

In a phone interview yesterday with one of only a handful of other companies known to be working on lithium-sulfur, PolyPlus, we were told its solid-state technologies – while just as promising – will require new assembly machinery. Less is known about Sion, another purveyor of Li-S, as possibly are also a few automotive OEMs working behind the scenes, including Toyota and Daimler.

But Crittenden says OXIS and GP are good to go.

“Analysis of the bill of materials for lithium sulfur pouch cells produced in volume, indicates that the total material costs are similar to that of lithium iron phosphate,” said Crittenden in an article he wrote for Batteries International. “The production processing required is about 70 percent of lithium ion, with much of the equipment similar, so that both capital investments costs and processing costs will be lower.”

Meanwhile, OXIS says it has been achieving 20-percent year-over-year improvements for cells that are presently delivering 200 Wh/kg at the pouch cell level, 350 Wh/kg at the coin cell level, and with promise of a doubling or more in the next 2-3 years.

This is not a whole lot better than li-ion, but Li-S offers other benefits not least of which is major upside potential.

The theoretical energy density of lithium-sulfur is actually 2,700 Wh/kg, or five times that of lithium-ion. We’ve seen in recent weeks other promising Li-S developments such as by the Oak Ridge National Laboratory which is working toward U.S. Department of Energy (DoE) goals.

OXIS Energy Ltd.

OXIS Energy Ltd.

OXIS, as do other companies working on their own approach to the challenges of uncapping lithium-sulfur’s potential, sees lithium-sulfur as the next most viable energy storage chemistry on the way to lithium-air.

IBM has said lithium-air will be practical some time in the early 2020s – how it can have 2020 vision a decade into the future is a good critical question, but we digress. In any case, OXIS’ statements are of what it has in its hands now. OXIS does concede Li-Air is the next step beyond Li-S, but Crittenden says he doesn’t think Li-Air will be ready until after 2030.

Truth be told, some would say even lithium-sulfur is barely ready, but OXIS is getting started with the lowest hanging fruit. This lets it meet needs now as it also begins to earn revenues and works on its business rather than isolating itself in a lab attempting to develop higher energy density as is currently the case in the U.S.

Not that American researchers are exactly in isolation, but the U.S. DoE-sponsored project, JCESR is one such project that sets much higher benchmarks before it will deem Li-S ready for prime time.

The DoE placed a $120 million bet on this project hosted by Argonne National Laboratory formally known as the Joint Center for Energy Storage Research at the end of 2012. Its goal is to come up with an automotive propulsion battery with five-times the range capacity, costing one-fifth present lithium-ion batteries, and to be completed in the next five years.

This is a simplified overview of the science. Non-techies may skip it if they want.
 

Good Enough For Government Work

Despite the U.S. government demanding more for Li-S before using it for electric car batteries, other government entities – particularly the military – see reason to get started now.

Crittenden says energy storage systems using metallic lithium offer the highest specific energy, and OXIS has also received support for UK Ministry of Defense battery packs to be carried by NATO soldiers. Soldiers must carry 8 kg or so, and if this can be cut in half, that is a huge tactical advantage in the eyes of commanders.

Where the batteries have a leg up for certain transportation needs is in the area of safety. OXIS cites the Boeing Dreamliner incidents and other evidence of fire hazard for those who believe lithium iron phosphate batteries (LiFePO4) and other forms of li-ion are safe enough.

OXIS Li-S electrolytes, says Crittenden, offer a mechanism for the passivation of suspended or “mossy” lithium by instantaneously creating a (Li2S) film on metallic lithium.

A lithium-sulfur cell consists of layers of the following: • An anode of lithium metal, protected by a lithium sulfide passivation layer; •A sulfur-based cathode – the sulfur combines with the lithium as the electrochemical reaction, but as sulfur has a low conductivity, carbon is also added. Polymer is then used to bind the cathode together; and •	Separator and Electrolyte. The choice of electrolyte is critical for ensuring the safety of the cell. For a safe cell, it is important to formulate an electrolyte which has high flash point and thus a low flammability.

A lithium-sulfur cell consists of layers of the following:
• An anode of lithium metal, protected by a lithium sulfide passivation layer;
• A sulfur-based cathode – the sulfur combines with the lithium as the electrochemical reaction, but as sulfur has a low conductivity, carbon is also added. Polymer is then used to bind the cathode together; and
• Separator and Electrolyte. The choice of electrolyte is critical for ensuring the safety of the cell. For a safe cell, it is important to formulate an electrolyte which has high flash point and thus a low flammability.

Passivated lithium that forms during charging is dissolved upon discharge or when the battery is at rest, he said. This protection is supported chemically and is associated with what’s called the “sulfide cycle.” Li2S has a melting point of 938°C and OXIS says it is a perfect insulator.

“The failure mode for OXIS’ Li-metal battery is the loss of capacity due to formation between electrodes of non-conductive and highly stable passivated lithium sulfide,” says a statement from the company. “OXIS’ batteries use ‘heavy’ electrolytes with high flash points. Our prototypes have demonstrated safe performance from room temperatures to 140°C, albeit with reduced capacity at the top end of this range.”

OXIS has also attempted to abuse the batteries to test for failure. Nail penetration tests both on freshly assembled and cycled pouch cells (0.5Ah capacity) resulted in no significant temperature increase.

Examination confirmed that there was no localized temperature increase where the nail penetrated. This is due to the rapid spread of the reaction across the full surface of the lithium electrode producing effective heat dissipation.

In fact, a nail penetrated cell was actually recharged and functioned albeit with less energy because of the missing material where the nail damaged it.

The cells have also been shot through with bullets for military tests, and subjected to short circuiting, all without inducing fire from “thermal runaway.”

Spec-wise, some info is being divulged at this point: Cells’ continuous discharge figures (from fully charged to fully discharged) are typically 2C.

“For voltages, we are not currently openly disclosing our cut-off voltages. However I can say that the nominal voltage is 2.1 volts,” Crittenden said.

As for recharging, Crittenden said larger packs could take seven hours but this is an area the company has not focused nearly as heavily, and is now doing so. OXIS expects charge times to reduce to 5 hours in the next 6 months, to 4 hours in the next year, with the ultimate goal of achieving “fast-charging” technology.

As mentioned, OXIS cells are “maintenance free.” This means unlike today’s li-ion-powered electric cars, no charging is required to prevent damage when left for extended periods.

Therefore you won’t likely “brick” them if you leave them unplugged for a duration – a problem Tesla had with its Roadster, had to take steps to mitigate with its Model S, and still a potential concern for any car with li-ion batteries.

Crittenden also says Li-S is more environmentally friendly than li-ion because sulfur is used instead of heavy metals such as nickel and cobalt.

As an added bonus, the sulfur is a recycled by-product from petroleum processing, so in effect, the oil industry is providing a raw ingredient that could one day lead to its demise.

 

Actual Applications

To start with, automotive or nearly automotive projects OXIS is known to be working with are those with the innovative French company, INDUCT. While Crittenden said talks are ongoing with European and other OEMs, the company’s CEO, Huw W. Hampson-Jones who joined OXIS in 2010 in part to help grow the transportation business, has said major manufacturers are sometimes reluctant to run with new ideas.

“The automotive industry is very slow; and although I understand their reticence in accepting a new technology, what is frustrating is their lethargy in grasping the movement of ideas and science that has enabled the breakthrough OXIS’ technological development has made on many levels,” said Hampson Jones. “Working with smaller, less well established automotive manufacturers is, at present, far more rewarding for us as their hierarchy and decision making skills are far more effective in the adoption of new ideas and execution.”

To wit, the first cars to receive Li-S batteries appear to be the INDUCT Modulgo Urban Car (top photo) and driverless Navia (in video).

These and two wheelers by other companies that will use Li-S will not require a liquid thermal management system. Li-S operates safely at higher temperatures, and Crittenden said he is unsure whether larger scale packs would require a liquid TMS either.

A smartphone serves as instrumentation and the means to start the Modulgo car.

A smartphone serves as instrumentation and the means to start the Modulgo car.

The Modulgo is designed from telematics technology and intended to offer advanced car sharing solutions as a low-cost urban EV.

It seats three in a single row, tops out at 68 mph (110 kph), and has a maximum range in the city of 87 miles (140 km). A mobile phone is used as the dashboard and ignition key. The car offers multimedia for the driver and passengers, recharges inductively, and its body is 100-percent recyclable.

The Modulgo was revealed at Geneva in 2011 and OXIS says its batteries will be in it next year.

phone_Modulgo

The Navia – also called the Cybergo – is equipped with laser range finders, cameras and a software package that allows it to move autonomously and safely in any environment.

Here safety is critical with no human actively monitoring it. Crittenden said the safer than li-ion aspect of LI-S was a big selling point. This vehicle will get an approximately 10-kilowatt-hour Li-S pack in 2014.

Two wheelers to receive OXIS batteries will be the WESP scooter, which is made by QWIC of the Netherlands, and to be distributed to around 350 shops in the Netherlands, Belgium, Germany and France.

Crittenden would not disclose specs, but range will be impressive, he said, and it will be user friendly and safe as a scooter can be.

The same goes for Wisper e-bikes being developed in Germany for European markets and OXIS says it will be launched in 2014 year. Present customers include the City of London Police and Dominoes Pizza.

Wisper e-bike.

Wisper e-bike.

We asked the company if it could project a dollar per kwh cost for a Li-S pack. Presently in U.S. it’s around $700 with projections that it could drop to as low as $150-200, but we got only a around-a-bout reply.

“Our first priority is to develop a world class Li-S technology that can deliver the features and services which we have defined in conjunction with our partners and customers,” answered Hampson-Jones. “That price is important, I don’t deny, but safety, the elimination of distance anxiety, the lightness of weight a premier features, and our customers are very much ready to pay for those. In achieving those features and being competitive is our objective.”

Left unsaid, but it should be evident by now is that the company is a forerunner in a niche market with an ostensibly viable product that must begin to supplant li-ion, so that could be a further hint about pricing for now.

Like Goldilocks’ porridge, it will have to be not too hot, not too cold, but just what the market will bear.

Primed and Ready

While the U.S. attempts to perfect lithium-sulfur to a far greater degree of its inherent potential, OXIS has lined up its initial supply chain and distribution channels and is pushing ahead of all.

The company has also signed Joint Development Agreements with France’s leading chemicals producer, Arkema, as well as with one of the world’s largest polymer companies, Bayer MaterialScience of Germany.

These are hoped to helps expedite development of new polymer binders, carbon materials, electrode substrates and lithium salts to continually improve the technology going forward.

WESP

OXIS also has links with St Andrew University, Imperial College London, Oxford University and Cranfield University, as well as with Material Science Departments of both Oxford and Cambridge Universities.

It also received an investment of £15 million ($23 million) from the giant South African energy and chemical company Sasol, and has accepted further grants as well.

The company also recently signed with Canadian defense contractor Panacis which caters to U.S. and NATO military. OXIS says it is well positioned therefore to grow, even as it reaches ahead of all others to be, in the words of Crittenden, “the world-leading company in the development of lithium sulfur, seen by many as the next Generation Battery technology.”

We also asked Hampson-Jones why no info on work with U.S. companies is to be found on its Web site, but he said this would change soon.

“We are collaborating with US companies, watch this space for an announcement in the fall,” said Hampson-Jones. “We aim to enter the U.S. market in 2014.”