Rechargeable Lithium Metal Battery

Rice University scientists have created a rechargeable lithium metal battery with three times the capacity of commercial lithium-ion batteries by resolving something that has long stumped researchers: the dendrite problem.

The Rice battery stores lithium in a unique anode, a seamless hybrid of graphene and carbon nanotubes. The material first created at Rice in 2012 is essentially a three-dimensional carbon surface that provides abundant area for lithium to inhabit. Lithium metal coats the hybrid graphene and carbon nanotube anode in a battery created at Rice University. The lithium metal coats the three-dimensional structure of the anode and avoids forming dendrites.

The anode itself approaches the theoretical maximum for storage of lithium metal while resisting the formation of damaging dendrites or “mossy” deposits.

Dendrites have bedeviled attempts to replace lithium-ion with advanced lithium metal batteries that last longer and charge faster. Dendrites are lithium deposits that grow into the battery’s electrolyte. If they bridge the anode and cathode and create a short circuit, the battery may fail, catch fire or even explode.

Rice researchers led by chemist James Tour found that when the new batteries are charged, lithium metal evenly coats the highly conductive carbon hybrid in which nanotubes are covalently bonded to the graphene surface. As reported in the American Chemical Society journal ACS Nano, the hybrid replaces graphite anodes in common lithium-ion batteries that trade capacity for safety.

Lithium-ion batteries have changed the world, no doubt,” Tour said, “but they’re about as good as they’re going to get. Your cellphone’s battery won’t last any longer until new technology comes along.

He said the new anode’s nanotube forest, with its low density and high surface area, has plenty of space for lithium particles to slip in and out as the battery charges and discharges. The lithium is evenly distributed, spreading out the current carried by ions in the electrolyte and suppressing the growth of dendrites.

Source: http://news.rice.edu

Self-Healing Lithium-Ion Batteries

Researchers at the University of Illinois have found a way to apply self-healing technology to lithium-ion batteries to make them more reliable and last longer.

The group developed a battery that uses a silicon nanoparticle composite material on the negatively charged side of the battery and a novel way to hold the composite together – a known problem with batteries that contain silicon.

Materials science and engineering professor Nancy Sottos and aerospace engineering professor Scott White led the study published in the journal Advanced Energy Materials.

“This work is particularly new to self-healing materials research because it is applied to materials that store energy,” White said. “It’s a different type of objective altogether. Instead of recovering structural performance, we’re healing the ability to store energy.”

The negatively charged electrode, or anode, inside the lithium-ion batteries that power our portable devices and electric cars are typically made of a graphite particle composite. These batteries work well, but it takes a long time for them to power up, and over time, the charge does not last as long as it did when the batteries were new.

Silicon has such a high capacity, and with that high capacity, you get more energy out of your battery, except it also undergoes a huge volume expansion as it cycles and self-pulverizes,” Sottos explained.

Past research found that battery anodes made from nanosized silicon particles are less likely to break down, but suffer from other problems.

You go through the charge-discharge cycle once, twice, three times, and eventually you lose capacity because the silicon particles start to break away from the binder,” White said.

To combat this problem, the group further refined the silicon anode by giving it the ability to fix itself on the fly. This self-healing happens through a reversible chemical bond at the interface between the silicon nanoparticles and polymer binder.

Source: https://news.illinois.edu/

Electric Car: Nanofiber Electrodes Boost Fuel Cells By 30 Percent

At the same time Honda and Toyota are introducing fuel cell cars to the U.S. market, a team of researchers from Vanderbilt University, Nissan North America and Georgia Institute of Technology have teamed up to create a new technology designed to give fuel cells more oomph. The project is part of a $13 million Department of Energy program to advance fuel cell performance and durability and hydrogen storage technologies announced last month.

hydrogen fuel cells

Fuel cells were invented back in 1839 but their first real world application wasn’t until the 1960’s when NASA used them to power the Apollo spacecraft. Fuel cells need fuel and air to run, like a gasoline engine, but they produce electricity, like a battery. In hydrogen/air fuel cells, hydrogen flows into one side of the device. Air is pumped into the other side. At the anode, the hydrogen is oxidized into protons. The protons flow to the cathode where the air is channeled, reducing the oxygen to form water. Special catalysts in the anode and cathode allow these reactions to occur spontaneously, producing electricity in the process. Fuel cells convert fuel to electricity with efficiencies ranging from 40 percent to 60 percent. They have no moving parts so they are very quiet. With the only waste product being water, they are environmentally friendly.The $2.5 million collaboration is based on a new nanofiber mat technology developed by Peter Pintauro, Professor of Chemical Engineering at Vanderbilt, that replaces the conventional electrodes used in fuel cells. The nanofiber electrodes boost the power output of fuel cells by 30 percent while being less expensive and more durable than conventional catalyst layers. The technology has been patented by Vanderbilt and licensed to Merck KGaA in Germany, which is working with major auto manufacturers in applying it to the next generation of automotive fuel cells.

Conventional fuel cells use thin sheets of catalyst particles mixed with a polymer binder for the electrodes. The catalyst is typically platinum on carbon powder. The Vanderbilt approach replaces these solid sheets with mats made from a tangle of polymer fibers that are each a fraction of the thickness of a human hair made by a process called electrospinning. Particles of catalyst are bonded to the fibers. The very small diameter of the fibers means that there is a larger surface area of catalyst available for hydrogen and oxygen gas reactions during fuel cell operation. The pores between fibers in the mat electrode also facilitate the removal of the waste water. The unique fiber electrode structure results in higher fuel cell power, with less expensive platinum.
Source: http://news.vanderbilt.edu/

How To Store 10 Times More Energy In A Li-ion Battery

Scientists have been trying for years to make a practical lithium-ion battery anode out of silicon, which could store 10 times more energy per charge than today’s commercial anodes and make high-performance batteries a lot smaller and lighter. But two major problems have stood in the way: Silicon particles swell, crack and shatter during battery charging, and they react with the battery electrolyte to form a coating that saps their performance. Now, a team from Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory has come up with a possible solution: Wrap each and every silicon anode particle in a custom-fit cage made of graphene, a pure form of carbon that is the thinnest and strongest material known and a great conductor of electricity.

In a report published Jan. 25 in Nature Energy, they describe a simple, three-step method for building microscopic graphene cages of just the right size: roomy enough to let the silicon particle expand as the battery charges, yet tight enough to hold all the pieces together when the particle falls apart, so it can continue to function at high capacity. The strong, flexible cages also block destructive chemical reactions with the electrolyte.

graphene_cageThis time-lapse movie from an electron microscope shows the new battery material in action: a silicon particle expanding and cracking inside a graphene cage while being charged. The cage holds the pieces of the particle together and preserves its electrical conductivity and performance

In testing, the graphene cages actually enhanced the electrical conductivity of the particles and provided high charge capacity, chemical stability and efficiency,” said Yi Cui, an associate professor at SLAC and Stanford who led the research. “The method can be applied to other electrode materials, too, making energy-dense, low-cost battery materials a realistic possibility.

This new method allows us to use much larger silicon particles that are one to three microns, or millionths of a meter, in diameter, which are cheap and widely available,” Cui adds. “In fact, the particles we used are very similar to the waste created by milling silicon ingots to make semiconductor chips; they’re like bits of sawdust of all shapes and sizes. Particles this big have never performed well in battery anodes before, so this is a very exciting new achievement, and we think it offers a practical solution.

Source: https://www6.slac.stanford.edu/

Candle Soot Powers Lithium Ion Battery

A new study reveals that carbon from candle soot could be used to power the kind of lithium ion battery in plug-in hybrid electric cars. Researchers from the Indian Institute of Technology in Hyderabad, India claim that their findings could open up possibilities for using carbon in more powerful batteries, which could drive down the costs of portable power.

Lithium ion batteries are used to power a wide range of devices, including smartphones, digital cameras, electric cars and even aircraft. The batteries produce current through two electrically charged materials suspended in a liquid. Carbon, while used as one of the materials in smaller batteries, is considered unsuitable for bigger and more powerful batteries because of its structure, which cannot produce the required current density.

In the new study, published in the journal Electrochimica Acta, the researchers found that because of the shape and configuration of the tiny carbon nanoparticles, the carbon in candle soot could be used in bigger batteries. The team also said that their research introduces a more scalable approach to making batteries because the soot could be produced quickly and easily.

soot

If you put water droplet on candle soot it rolls off – that’s an observation that’s been made in the last few years. The material candle soot is made of, carbon, also has electric potential. So why not use it as an electrode? We looked into it and saw it also shows some exceptional electrochemical properties, so we decided to test it further,” said Dr Chandra Sharma, one of the study’s authors.

Using a technique called cyclic charge-discharge, or CCD, the researchers analysed the effectiveness of soot as a conducting material to use in a battery. The technique shows how powerful the battery is based on the rate of charge or discharge: the higher the rate, the more powerful the battery. According to the study’s results, the candle soot carbon performed better at higher rates.

Sharma said the technology is not only efficient and cost-effective but also scalable, which could make battery production cheaper. One hybrid car would need approximately 10 kilograms of carbon soot, which would be deposited in about an hour using candles, Sharma explained.

Source: http://www.sciencedirect.com/
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http://www.ibtimes.com.au/

EV: A Thin Film That Produces Oxygen and Hydrogen

A cobalt-based thin film serves double duty as a new catalyst that produces both hydrogen and oxygen from water to feed fuel cells, according to scientists at Rice University. This discovery may lower the cost of future hydrogen electric car.  The inexpensive, highly porous material invented by the Rice lab of chemist James Tour may have advantages as a catalyst for the production of hydrogen via water electrolysis. A single film far thinner than a hair can be used as both the anode and cathode in an electrolysis device.

The researchers led by Rice postdoctoral researcher Yang Yang reported their discovery  in Advanced Materials.

They determined their cobalt film is much better at producing hydrogen than most state-of-the-art materials and is competitive with (and much cheaper than) commercial platinum catalysts. They reported the catalyst also produced an oxygen evolution reaction comparable to current materials.

CATALYST

A side view of a porous cobalt phosphide/phosphate thin film created at Rice University. The robust film could replace expensive metals like platinum in water-electrolysis devices that produce hydrogen and oxygen for fuel cells. The scale bar equals 500 nanometers.

It is amazing that in water-splitting, the same material can make both hydrogen and oxygen,” Tour said. “Usually materials make one or the other, but not both.”

The researchers suggested applying alternating current from wind or solar energy sources to cobalt-based electrolysis could be an environmentally friendly source of hydrogen and oxygen.

Source: http://news.rice.edu/

Defect-Free Graphene For Electric Car Batteries

Researchers at from Korea’s KAIST institute developed a new method to fabricate defect-free graphene. Using this graphene, they developed a promising high-performance anode for Li-Ion batteries. Graphene has already been demonstrated to be useful in Li-ion batteries, despite the fact that the graphene used often contains defects. Large-scale fabrication of graphene that is chemically pure, structurally uniform, and size-tunable for battery applications has so far remained elusive. Now in a new study, scientists have developed a method to fabricate defect-free graphene (df-G) without any trace of structural damage. Wrapping a large sheet of negatively charged df-G around a positively charged Co3O4 creates a very promising anode for high-performance Li-ion batteries.
electric car

The research groups of Professor Junk-Ki Park and Professor Hee-Tak Kim from Korea Advanced Institute of Science and Technology (KAIST) and Professor Yong-Min Lee’s research group from Hanbat National University, all in Daejeon, South Korea, have published their paper on the new fabrication method in a recent issue of Nano Letters.

Source: http://phys.org/

Sand-based Lithium Ion Batteries That Outperform Standard by 3 times

Researchers at the University of California, Riverside’s Bourns College of Engineering have created a lithium ion battery that outperforms the current industry standard by three times. The key material: sand. Yes, sand.

This is the holy grail – a low cost, non-toxic, environmentally friendly way to produce high performance lithium ion battery anodes,” said Zachary Favors, a graduate student working with Cengiz and Mihri Ozkan, both engineering professors at UC Riverside.
The idea came to Favors six months ago. He was relaxing on the beach after surfing in San Clemente, Calif. when he picked up some sand, took a close look at it and saw it was made up primarily of quartz, or silicon dioxide.

His research is centered on building better lithium ion batteries, primarily for personal electronics and electric vehicles. He is focused on the anode, or negative side of the battery. Graphite is the current standard material for the anode, but as electronics have become more powerful graphite’s ability to be improved has been virtually tapped out.
Researchers are now focused on using silicon at the nanoscale, or billionths of a meter, level as a replacement for graphite. The problem with nanoscale silicon is that it degrades quickly and is hard to produce in large quantities.
Findings have been published in in the journal Nature Scientific Reports.
Source: http://ucrtoday.ucr.edu/