Lithium air batteries breakthrough technology
bottlenecks or standards will become the next
generation of battery technology
On Thursday, the university of Cambridge researchers published a document showing they have developed a lithium air battery, successfully solve some practical problems in the technology, especially the unstable chemical problems.Before that, because of this chemical is not stable, lithium air batteries will show performance decline rapidly.They developed the lithium air batteries with high energy density, and be able to more than 2000 times a charging circuit.The battery in theory of energy efficiency more than 90%.
Scientists are very hope one day lithium air batteries can replace our current use of lithium ion battery."Lithium ion rechargeable batteries have been used for almost 25 years," Clare p. of chemistry at the university of Cambridge professor Grey said by telephone, "25 years ago, the structure is more compact lithium ion battery, paving the way for the emergence of portable electronic products, enable us to carry the electronic devices become more light and portable. Lithium ion battery technology is more suitable for consumers at the time, now, it is time for lithium air batteries to replace it."
No chemist or engineer will say, lithium ion battery is perfect.With the increasing popularity of electric cars, the researchers began to focus on the study of lithium air batteries.Because lithium air batteries is much lighter than lithium ion battery, lighter cars means more long range.To be sure, lithium air batteries ideally has higher energy density.In theory, only the battery can make electric cars without having to carry large and heavy under the condition of the battery pack, with comparable range of gasoline and diesel car.
Still need to be 10 years to be commercially available
In a press release, scientists at the university of Cambridge, said although their research has successfully overcome the biggest obstacle in the technology of lithium air batteries, lithium air batteries used for commercial purposes but will need at least 10 years.
The basic chemical principle is very simple lithium air batteries.Discharging, starting from the cathode of lithium ion in anode reaction with oxygen in the air, produce a kind of call peroxide lithium solid product, fill in the pore of carbon electrode.Reverse charging, chemical process, peroxide lithium is broken down to release oxygen.
Prototype lithium air batteries is in long before had been successfully made out, the battery storage capacity of the battery are theoretically 10 times of lithium ion batteries on the market at present, due to the lithium metal have very instability in chemistry, there are multiple major defect in practical application.How to reliably make the reaction occur repeatedly in many cycle, is one of the biggest challenges facing the technology.
Lithium battery of peroxide reaction product and the product of the reaction between lithium oxide has high reactivity, decompose the electrolyte, so after a few charge and discharge cycle battery will drop sharply, short battery life.Because lithium conductive performance is poor, peroxide charging is difficult to decompose, need very high charging voltage, and it will cause the decomposition of the electrolyte and carbon electrode and other side effects.
Discharging, peroxide can jam lithium porous carbon electrodes, lead to discharge end ahead of schedule;When charging, lithium metal anode surface will show to the positive dendritic growth, could eventually lead to short circuit, pose a safety hazard.Lithium metal and water vapor in the air, nitrogen, carbon dioxide will react, causing the cathode material consumption, finally make a battery failure.
Chemical stability improved
Researchers at the university of Cambridge to multi-level macroporous graphene as the anode material, the use of water and lithium iodide as the electrolyte additives, eventually produce and decomposition of lithium hydroxide, rather than after the peroxide lithium batteries.Lithium hydroxide is stable than lithium peroxide, greatly reduced the side effects of battery, improve the performance of battery.The iodide lithium hydroxide, lithium in addition to helping decomposition, it seems, are still have played an important role in protection of lithium metal anode, make the battery have some immunity to excess water.Without it, the same amount of water can make
the battery failure directly, completely unable to charge and discharge.Because graphene oxide is porous, the researchers estimate that more than 2000 times this battery cycle.
Researchers said at a news conference, they will be the gap voltage down to 0.2 V lithium air batteries, improve the efficiency of the battery performance and success.They developed a model of lithium air batteries' storage capacity of about 3000 watts/kg, about eight times the current lithium ion battery, recycled charge-discharge thousands of times, for the first time cycle charge-discharge efficiency is as high as 93%, namely filling the 93% of the energy in the battery during discharge can be used.
There are still technical challenges need to overcome
But there are still some current lithium air batteries.The decrease of the gap voltage and large capacity graphene oxide electrodes, which lead to the only large enough to accommodate smaller ratio of charge and discharge, the formation of lithium battery cathode metal sometimes still affect battery performance of dendrites.And, as we mentioned in the former paper, not only the oxygen in the air, the other compounds in the air can also lead to unstable lithium air batteries.
And yet to solve these problems, also means that the lithium air batteries are still not really be commercially available.Research and development of new battery technology is easy, but it really be put into use or need to overcome many technical difficulties.The researchers say they are now cooperating with several companies, seeks to promote the technology as soon as possible.