{"id":10541,"date":"2015-11-12T23:47:39","date_gmt":"2015-11-13T06:47:39","guid":{"rendered":"http:\/\/cafe.foundation\/blog\/?p=10541"},"modified":"2015-12-13T22:19:49","modified_gmt":"2015-12-14T05:19:49","slug":"cambridges-ultimate-battery-wait-10-years-and-see","status":"publish","type":"post","link":"http:\/\/cafe.foundation\/blog\/cambridges-ultimate-battery-wait-10-years-and-see\/","title":{"rendered":"Cambridge\u2019s \u201cUltimate\u201d Battery? Wait 10 Years and See"},"content":{"rendered":"

Cambridge University researchers claim to have successfully demonstrated how several of the problems impeding the practical development of the so-called \u201cultimate\u201d battery<\/a>, in this case a lithium-oxygen unit, could be overcome.\u00a0 They make some pretty impressive claims, saying they\u2019ve developed a working laboratory demonstrator with \u201cvery high\u201d energy density \u2013 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.<\/p>\n

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.<\/p>\n

\"Cambridge<\/a>

Cambridge “Ultimate Battery” under charge and discharge conditions<\/p><\/div>\n

Researchers add the promise of one-fifth the cost and one-fifth the weight of currently available batteries \u2013 a touchstone for electric aircraft designers, and close to the goals U. S. Energy Secretary Steven Chu asked for three years ago.<\/p>\n

Perhaps some of that weight difference comes from the \u201cfluffy\u201d nature of the electrodes, a frothy combination of graphene and \u201cadditives that alter the chemical reactions at work in the battery, making it more stable and more efficient.\u201d<\/p>\n

\""Fluffy"<\/a>

“Fluffy” electrodes, composed of one-atom thin layers of graphene<\/p><\/div>\n

At this stage, the good news \u2013 that the basic premise seems to work as promised \u2013 is countered by the bad news that commercial, \u201cpractical\u201d lithium-air battery is still \u201cat least\u201d a decade away.\u00a0 (Wait a minute, where is the traditional message that the new invention is five years away?)<\/p>\n

Professor Clare Grey of Cambridge\u2019s Department of Chemistry explains, \u201cWhat we\u2019ve achieved is a significant advance for this technology and suggests whole new areas for research \u2013 we haven\u2019t solved all the problems inherent to this chemistry, but our results do show routes forward towards a practical device.\u201d\u00a0 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.\u00a0 Her group notes, \u201cMany of the technologies we use every day have been getting smaller, faster and cheaper each year \u2013 with the notable exception of batteries.\u201d<\/p>\n

Dr. Grey\u2019s co-author on their Science<\/em> paper,<\/a> Dr. Tao Liu, explains, \u201cIn their simplest form, batteries are made of three components: a positive electrode, a negative electrode and an electrolyte.\u201d<\/p>\n

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.\u00a0 Even though they are light and energy dense, their \u201crelatively low\u201d energy densities require frequent recharging.<\/p>\n

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.<\/p>\n

Grey and her team use a different chemistry that earlier attempts at a \u201cdry\u201d (non-aqueous) Li-air battery, using lithium hydroxide (LiOH) rather than lithium peroxide (Li2<\/sub>O2<\/sub>).\u00a0\u00a0\u00a0 Using a highly porous form of graphene for one electrode, and adding water and lithium idodide as a \u201cmediator\u201d in the electrolyte, made their battery more stable after multiple charge\/discharge cycles.\u00a0 These approaches reduced the \u201cvoltage gap\u201d between charge and discharge to 0.2 Volts, making for a more efficient battery.<\/p>\n

https:\/\/www.youtube.com\/watch?v=rmYQDemvdv4<\/p>\n

That highly porous graphene electrode greatly increases the capacity of the demonstrator, although only at certain rates of charge and discharge. \u00a0Researchers need to find how to protect the metal electrode so it doesn\u2019t form dendrites, which can cause batteries to explode if they grow too much and short-circuit the battery.<\/p>\n

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.\u00a0 The CO2, nitrogen and moisture we live in would harm the metal electrode.\u00a0 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.<\/p>\n

Even though Liu concedes, \u201cThere\u2019s still a lot of work to do,\u201d he thinks solutions are possible for all the problems, and \u201cwe\u2019ve shown that there are solutions to some of the tough problems associated with this technology.\u201d<\/p>\n

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\u00a0Cambridge Enterprise<\/a>, the University\u2019s commercialization arm.<\/p>\n