Original URL: http://www.theregister.co.uk/2013/05/28/hot_lithium_ion_batts/

Hot new battery technologies need a cooling off period

IBM boffins want to run your car on air - and lithium

By Dave Wilby

Posted in Hardware, 28th May 2013 07:02 GMT

Scientists began buzzing about electrochemical energy cells in the 18th century; consumers bought their first low-density Lithium-ion batteries in the late 1980s, and industry became hooked on the things in the 1990s. Ever since, the comedy electronic-device conflagration has been as much a staple of tech news kibble as the hilarious satnav blunder.

But despite a long gestation period and some significant advances in the state of the art, Lithium-ion cells today still suffer the kind of problems that generate embarrassing headlines.

Heat – or, rather, overheating - has been the problem: Dell recalled more than four million laptops in 2006 after finding that their Li-ion batteries were catching fire. Nokia recalled 46 million phone batteries a year later in 2007, and Lenovo recalled tens of thousands of batteries in 2009, 2011 and 2012.

Laptops and phones are one thing, but this year Boeing was forced to ground a 50-strong fleet of its 787 Dreamliner jets after a charging issue caused a battery fire on a Nippon Airways flight.

The most explosive incidents likely came as a result of iron filings, not lithium, entering batteries during manufacturing, possibly when crimping the batteries shut. Over time, these pieces of metal managed to create shorts between anodes and cathodes, causing rapid heating and thermal runaway – essentially metal particles were short-circuiting the batteries. Manufacturers today are understandably concerned that it’s also possible to grow lithium dendrites across from a lithium metal anode to the cathode, again causing a short and potentially similar results.

But lithium-ion remains the most common and popular rechargeable battery technology that we have. The recent Dreamliner problem proves the problem hasn’t disappeared since the mid 2000s, despite considerable advances. In fact, advances have pushed Li-ion batteries into new areas, meaning that the kind of problems that once cooked laps are now taking commercial airliners out of service.

Rechargeable lithium-ion batteries have evolved to deliver ever higher energy densities, longer life and greater reliability at lower cost. As a result they have been put to work in a wide range of applications from computers to medical devices, consumer electronics to electric cars.

It’s the electric car application that’s now driving research, development, innovation - and some hype - in the lithium world. The battery industry is by nature quite conservative and operates on fairly linear lines. But labs and research hubs all over the world are now working on improved lithium-ion technologies that could prove to be game-changers, transforming multiple industries if they could only surmount overheating and combustion issues while delivering a step-change in efficiency, durability and recharge times.

Lithium-sulphur technology is one area that could be getting closer to becoming commercial, through the efforts of companies like Sion Power and Polyplus in the US. They would likely be lower cost (sulphur is cheap) and have higher energy density (Sion claims 2600 watt hours per litre) than lithium-ion, but there is still work to be done in harnessing these benefits while simultaneously guaranteeing safe charging cycles and assuring commercial reliability.

And there are other possibilities on the horizon. IBM believes that lithium-air batteries could deliver the significant improvements required to transform the weight, cost and reliability of the next generation of rechargeable batteries – potentially delivering the electric cars we had hoped for before we realised that lithium-ion models would only travel about 75 miles, cost £30,000 a pop, and took up to 16 hours to recharge.

IBM’s Battery 500 Project was developed at the Almaden Institute in 2009 to develop lithium-air technology that it still hopes will improve current energy densities tenfold. The proposed technology uses air as a reagent. In theory oxygen reacts with lithium ions to form lithium peroxide on a carbon matrix during discharge, and on recharge releases oxygen back into the environment, while the lithium returns to the anode.

Sounds like a plan: but will it really work, how far away might it be from becoming commercial, and would it be safe?

Professor Clare Grey, professor of chemistry at Stony Brook University and the University of Cambridge tells The Reg:

“The safety issues of next-generation lithium-ion batteries must be resolved first before ever thinking about commercial applications. A really big game-change would require a technology like lithium-sulphur or possibly lithium-air. But any system using Lithium Metal is still regarded as inherently unsafe, and this hasn’t really entered into the game yet in current Lithium-air projects.”

Electrolyte treatment

IBM is already making claims that lithium-air technology could allow vehicles to travel up to 500 miles on a single charge. Big Blue's plan would see ‘Lithium Metal’ at the bottom of a composite structure below ‘Electrolyte 2’, a ‘Lithium-ion Transport Membrane’, ‘Electrolyte 1’ and a carbon structure on top. The membrane is there to stop the air from going through and attacking the lithium-metal - possibly solving the problem of lithium-dendrites - but there remain many outstanding issues with the very flammable and reactive Lithium Metal that are yet to be properly identified.

Professor Grey explains:

“Firstly, any membrane must entirely remove all water and carbon dioxide so that only completely dry air enters the battery system. Then there are problems of reversible cycling and reducing over-potential, or the difference in voltage between charge and discharge. Next a stable electrolyte needs to be identified that allows cycles over many years in an application such as a car battery. And that’s on top of any problems with the anode. So for me the technology is still a long way away.”

One intrinsic problem is that any material has weight, and with most materials it is only practically possible to get one, or in some cases two, electrons out of each atom. So there are fundamental limits as to how good a battery can be. In theory, because lithium is so light and oxygen arrives with common air, lithium-air technology proposes the lightest combination available. So if IBM or another team can react lithium and oxygen (or even sodium and oxygen which is a similar concept) then that almost represents the end of the game.

Air technology is already proving useful in other applications. Zinc-air batteries, for example, have had success in hearing aid technology, despite not being rechargeable. But can lithium-air really power a car over anything like a 500-mile range? A Nissan Leaf can currently travel an absolute maximum of 100 miles on an expensive battery. If it could go 100 miles on a cheap battery, that would also be game changing, in a different way. So perhaps getting costs down, using inherently more recyclable materials and managing expectations, is a more realistic approach right now?

Although it might not sound like such an exciting goal, taking a proven technology and achieving just a little higher energy density and making it a little bit cheaper is more attractive to manufacturers that survive on real-world commercial success. Firms like Nissan and Toyota are relatively happy investing in small progressive changes in systems that work, even if they are too expensive and the batteries don’t live as long as desirable. Major brands understandably need to plan their car roadmaps around technologies that already exist.

IBM of course is not a car company, and portable electronics will also be a driver. Batteries are not going to go away and we will only get more reliant on them. Our world will increasingly be controlled by things that need batteries. This progress will hopefully be coupled with more efficient electronics. But more efficient batteries that last ever longer will always be required. And then there’s also a push for more batteries on the electric grid. More renewables will require more efficient methods for short-term storage, and we will need more and better batteries, all of which will also drive research. And maybe somewhere in that mix is where Lithium Air will play its first role.

So perhaps what we really have is a more basic quandary affecting battery technology innovation. Should you over-hype projects that are nearer to concept than commercial reality in order to create as much interest and funding as possible? Or should you be realistic and not over-predict anything that may backfire further down the road?

We’re at a tipping point, explains Professor Grey:

“Lithium-air and lithium-sulphur are both fields that we should definitely be seeing more work in, because they are technologies that offer huge potential. But they also present some familiar challenges of battery and fuel cell development. How can you buy-in to a timeline when there are still a number of obvious technological showstoppers? How do you put a timeline on discovery? Certainly you accelerate the probability of discovery if you dedicate more clever people to working on the problems and combine academia with industry, but in most new systems there is generally a 15-year traditional timeframe until inventions become products.”

If battery project teams stop putting a positive spin on cutting-edge research, then they will never attract the levels of VC interest and funding that they so badly need to make vital breakthroughs. But on the other hand, we don’t want to see technologies pushed too enthusiastically down the road to becoming marketable products before sufficient tests and demonstrations of safety and reliability.

In the meantime, we will have to pick our way though the research hype while putting up with singed laps, grounded flights and electric cars whose performance is generally rather sub-par. ®