How To Charge Lithium Batteries 20 Times Faster

A touch of asphalt may be the secret to high-capacity lithium metal batteries that charge 10 to 20 times faster than commercial lithium-ion batteries, according to Rice University scientists. The Rice lab of chemist James Tour developed anodes comprising porous carbon made from asphalt that showed exceptional stability after more than 500 charge-discharge cycles. A high-current density of 20 milliamps per square centimeter demonstrated the material’s promise for use in rapid charge and discharge devices that require high-power density.

Scanning electron microscope images show an anode of asphalt, graphene nanoribbons and lithium at left and the same material without lithium at right. The material was developed at Rice University and shows promise for high-capacity lithium batteries that charge 20 times faster than commercial lithium-ion batteries

The capacity of these batteries is enormous, but what is equally remarkable is that we can bring them from zero charge to full charge in five minutes, rather than the typical two hours or more needed with other batteries,” Tour said.

The Tour lab previously used a derivative of asphalt — specifically, untreated gilsonite, the same type used for the battery — to capture greenhouse gases from natural gas. This time, the researchers mixed asphalt with conductive graphene nanoribbons and coated the composite with lithium metal through electrochemical deposition. The lab combined the anode with a sulfurized-carbon cathode to make full batteries for testing. The batteries showed a high-power density of 1,322 watts per kilogram and high-energy density of 943 watt-hours per kilogram.

Testing revealed another significant benefit: The carbon mitigated the formation of lithium dendrites. These mossy deposits invade a battery’s electrolyte. If they extend far enough, they short-circuit the anode and cathode and can cause the battery to fail, catch fire or explode. But the asphalt-derived carbon prevents any dendrite formation.

The finding is reported in the American Chemical Society journal ACS Nano.


Electric Car: More Silicon To Enhance Batteries

Silicon – the second most abundant element in the earth’s crust – shows great promise in Li-ion batteries, according to new research from the University of Eastern Finland. By replacing graphite anodes with silicon, it is possible to quadruple anode capacity.

In a climate-neutral society, renewable and emission-free sources of energy, such as wind and solar power, will become increasingly widespread. The supply of energy from these sources, however, is intermittent, and technological solutions are needed to safeguard the availability of energy also when it’s not sunny or windy. Furthermore, the transition to emission-free energy forms in transportation requires specific solutions for energy storage, and lithium-ion batteries are considered to have the best potential.

Researchers from the University of Eastern Finland introduced new technology to Li-ion batteries by replacing graphite used in anodes by silicon. The study analysed the suitability of electrochemically produced nanoporous silicon for Li-ion batteries. It is generally understood that in order for silicon to work in batteries, nanoparticles are required, and this brings its own challenges to the production, price and safety of the material. However, one of the main findings of the study was that particles sized between 10 and 20 micrometres and with the right porosity were in fact the most suitable ones to be used in batteries. The discovery is significant, as micrometre-sized particles are easier and safer to process than nanoparticles. This is also important from the viewpoint of battery material recyclability, among other things.

In our research, we were able to combine the best of nano– and micro-technologies: nano-level functionality combined with micro-level processability, and all this without compromising performance,” Researcher Timo Ikonen from the University of Eastern Finland says. “Small amounts of silicon are already used in Tesla’s batteries to increase their energy density, but it’s very challenging to further increase the amount,” he continues.

Next, researchers will combine silicon with small amounts of carbon nanotubes in order to further enhance the electrical conductivity and mechanical durability of the material.

The findings were published in Scientific Reports .


How To Increase By Six Times The Capacity Of Lithium-Ion Batteries

The capacity of lithium-ion batteries might be increased by six times by using anodes made of silicon instead of graphite. A team from the Helmholtz-Zentrum Berlin (HZB) Institute of Soft Matter and Functional Materials has observed for the first time in detail how lithium ions migrate into thin films of silicon. It was shown that extremely thin layers of silicon would be sufficient to achieve the maximal load of lithium.

The team was able to show through neutron measurements made at the Institut Laue-Langevin in Grenoble, France, that lithium ions do not penetrate deeply into the silicon. During the charge cycle, a 20-nm anode layer develops containing an extremely high proportion of lithium. This means extremely thin layers of silicon would be sufficient to achieve the maximal load of lithium.
lithium-ion battery

Lithium-ion batteries provide laptops, smart phones, and tablet computers with reliable energy. However, electric vehicles have not gotten as far along with conventional lithium-ion batteries. This is due to currently utilised electrode materials such as graphite only being able to stably adsorb a limited number of lithium ions, restricting the capacity of these batteries. Semiconductor materials like silicon are therefore receiving attention as alternative electrodes for lithium batteries. Bulk silicon is able to absorb enormous quantities of lithium. However, the migration of the lithium ions destroys the crystal structure of silicon. This can swell the volume by a factor of three, which leads to major mechanical stresses. Now a team from the HZB Institute for Soft Matter and Functional Materials headed by Prof. Matthias Ballauff has directly observed for the first time a lithium-silicon half-cell during its charging and discharge cycles. “We were able to precisely track where the lithium ions adsorb in the silicon electrode using neutron reflectometry methods, and also how fast they were moving”, comments Dr. Beatrix-Kamelia Seidlhofer, who carried out the experiments using the neutron source located at the Institute Laue-Langevin.

She discovered two different zones during her investigations. Near the boundary to the electrolytes, a roughly 20-nm layer formed having extremely high lithium content: 25 lithium atoms were lodged among 10 silicon atoms. A second adjacent layer contained only one lithium atom for ten silicon atoms. Both layers together are less than 100 nm thick after the second charging cycle.

After discharge, about one lithium ion per silicon node in the electrode remained in the silicon boundary layer exposed to the electrolytes. Seidlhofer calculates from this that the theoretical maximum capacity of these types of silicon-lithium batteries lies at about 2300 mAh/g. This is more than six times the theoretical maximum attainable capacity for a lithium-ion battery constructed with graphite (372 mAh/g).

The results ar published in the journal ACSnano (DOI: 10.1021/acsnano.6b02032).


3 times more powerfull Lithium-Ion Batteries, recharge in 10 minutes

Researchers at the University of South California – USC have developed a new lithium-ion battery design that uses porous silicon nanoparticles in place of the traditional graphite anodes to provide superior performance. The new batteries—which could be used in anything from cell phones to hybrid cars—hold three times as much energy as comparable graphite-based designs and recharge within 10 minutes. The design, currently under a provisional patent, could be commercially available within two to three years.

It’s an exciting research. It opens the door for the design of the next generation lithium-ion batteries,” said Chongwu Zhou, professor at the USC Viterbi School of Engineering, who led the team that developed the battery. Zhou worked with USC graduate students Mingyuan Ge, Jipeng Rong, Xin Fang and Anyi Zhang, as well as Yunhao Lu of Zhejiang University in China. Their research was published in Nano Research in January. “The easy method we use may generate real impact on battery applications in the near future,” Zhou said.