Doped Li-ion battery

A Japanese research group developed a rechargeable battery that has 7x higher energy density than Lithium-ion cells

8/12/14 8:00 pm chumakdenis 1

According to a report in Nikkel Technology, Japanese researchers at the School of Engineering at the University of Tokyo, in conjunction with chemical company  Nippon Shokubai have created a lithium-ion battery with seven times higher energy density of current standard lithium ion batteries.

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A thin-film energy storage device retains its battery- and supercapacitor-like qualities even after being flexed 1,000 times

The more energy dense a battery is, the smaller and lighter the battery can be that powers the objects. This is important for electric vehicles, because lighter vehicles can have a larger battery range, but it’s also important for making cell phones and tablets ever smaller and thinner.

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Tesla’s Model S Battery in the Alpha Build Room, image courtesy of Gigaom.

1584.jpgThe Japanese researchers, led by Professor Noritaka Mizuno, developed the energy dense battery by adding cobalt to the lithium oxide crystal structure, creating a new material for the positive electrode. The material on the positive electrode creates a new type of battery design based on an oxidation-reduction reaction (the loss and gain of electrons) between oxide ions and peroxide ions. Batteries have a positive and negative electrode and an electrolyte that helps shuttle ions back and forth to charge and discharge.

 

Li-ion vs Lead-acid batteries

Lithium-ion batteries have a high energy density compared to basic lead-acid batteries (those are the kind used to start gas-powered cars), but next-generation lithium batteries could have much higher energy densities.Lithium-air batteries that use lithium for the anode, air as the cathode (which is drawn in from the environment) and a liquid electrolyte could have an amazingly high energy density. Other innovations  like the one startup Envia has been working on are supposed to one day make a lithium-ion battery with an energy density of 400 watt-hours per kilogram, which (in theory) could deliver a 300-mile range electric car (compared to the 200-mile range available today).

So how it works?

Well,we're pretty sure that not everyone could understand how these batteries work,that's why we decided to explain it in easier and extended way.

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The new battery uses the oxidation-reduction reaction between oxide ions and peroxide ions at the positive electrode. The group proved that peroxides are generated and dispersed due to charge and discharge reactions by using a material made by adding cobalt (Co) to the crystal structure of lithium oxide (Li2O) for the positive electrode, verifying a battery system based on a new principle.

The oxidation-reduction reaction between Li2O and Li2O2 (lithium peroxide) and oxidation-reduction reaction of metal Li are used at the positive and negative electrodes, respectively, of the new battery. The battery has a theoretical capacity of 897mAh per 1g of the positive/negative electrode active material, voltage of 2.87V and theoretical energy density of 2,570Wh/kg.

At that time, the energy density is 370Wh per 1kg of the positive/negative electrode active material, which is about seven times higher than that of existing Li-ion rechargeable batteries using LiCoO2 positive electrodes and graphite negative electrodes. The theoretical energy density of the new battery is lower than that of lithium-air batteries (3,460Wh/kg). But it has a sealed structure like conventional Li-ion batteries, realizing a high reliability and safety.

This time, as the positive electrode material, the research group used a material made by using a planetary ball mill to add Co to the crystal structure of LiO2. And the group proved that it is possible to realize a battery system in which the oxidation-reduction reaction between oxides and peroxides reversibly proceeds. And it proved that  peroxides are generated in the positive electrode for charge,  the peroxides are dispersed for discharge and those reactions are repeated, by quantitatively analyzing the peroxides.

The group also proved that neither O2 nor CO2 is generated in the range where it is possible to reversibly charge/discharge the battery.

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The positive electrode used in the demonstration test enables to repeatedly charge/discharge the battery with a capacity of 200mAh/g and to quickly charge/discharge the battery with a large current. The positive electrode has a smaller mass ratio of Co than LiCoO2, which is used for existing Li-ion batteries, and possibly lowers costs.

 

Other related researches that're in progress

Researches at Stanford University, led by Professor of Material Science and Engineering Yi Cui, are working on a battery with a pure lithium anode (the negative electrode). A typical lithium-ion battery has a cathode (or positive electrode) made out of a lithium-metal oxide, such as lithium cobalt oxide, and an anode (negative electrode) made of graphite or silicon. The electrolyte shuttles lithium ions back and forth from the positive and negative electrode.

By making the anode out of lithium, a battery could operate more efficiently and with a higher energy density. Prior researchers have tried to make the anode out of lithium but one problem is that lithium ions expand as they gather on the anode during charging, causing hair-like growths called dendrites that short-circuit charging. Another issue is that lithium reacts quickly with the electrolyte.

The Stanford researchers, whose findings were published in Nature Nanotechnology recently, solved these problems by building a nanotech honeycomb of carbon domes on top of their lithium anode. They call it a nanosphere layer.

While boosting the energy density of lithium ion batteries is important, some researchers are also looking closely at the speed at which the batteries can charge. Fast charging could have important implications for electric cars as well as gadget batteries.

Researchers at the University of California, Riverside, led by Professor Wei Wang, are working on a new lithium ion battery design that they say can charge in 10 minutes. They’re using a silicon anode instead of a graphite anode, and they say that such a battery can be 40 percent smaller with 63 percent more capacity.

Will the lithium ion battery be the dominant battery form for many more decades to come? Tesla thinks so, which is why it’s investing billions of dollars into a massive lithium ion battery factory. And thanks to these types of scientific innovations, the lithium ion battery will get even better over the coming decades.

Of course, these innovations are still in the research phase. It’s one thing to have a lab breakthrough and another to get these designs into commercial batteries, but we do hope that that these batteries will go on sale as soon as possible.

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  battery with high energy and power capacity li-ion tesla gigafactory noritaka mizuno japanese researchers at the school of engineering

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