Nav: Home

Stanford-led team reveals nanoscale secrets of rechargeable batteries

August 04, 2016

Better batteries that charge quickly and last a long time are a brass ring for engineers. But despite decades of research and innovation, a fundamental understanding of exactly how batteries work at the smallest of scales has remained elusive.

In a paper published this week in the journal Science, a team led by William Chueh, an assistant professor of materials science and engineering at Stanford and a faculty scientist at the Department of Energy's SLAC National Accelerator Laboratory, has devised a way to peer as never before into the electrochemical reaction that fuels the most common rechargeable cell in use today: the lithium-ion battery.

By visualizing the fundamental building blocks of batteries - small particles typically measuring less than 1/100th of a human hair in size - the team members have illuminated a process that is far more complex than once thought. Both the method they developed to observe the battery in real time and their improved understanding of the electrochemistry could have far-reaching implications for battery design, management and beyond.

"It gives us fundamental insights into how batteries work," said Jongwoo Lim, a co-lead author of the paper and post-doctoral researcher at the Stanford Institute for Materials & Energy Sciences at SLAC. "Previously, most studies investigated the average behavior of the whole battery. Now, we can see and understand how individual battery particles charge and discharge."

The heart of a battery

At the heart of every lithium-ion battery is a simple chemical reaction in which positively charged lithium ions nestle in the lattice-like structure of a crystal electrode as the battery is discharging, receiving negatively charged electrons in the process. In reversing the reaction by removing electrons, the ions are freed and the battery is charged.

These basic processes - known as lithiation (discharge) and delithiation (charge) - are hampered by an electrochemical Achilles heel. Rarely do the ions insert uniformly across the surface of the particles. Instead, certain areas take on more ions, and others fewer. These inconsistencies eventually lead to mechanical stress as areas of the crystal lattice become overburdened with ions and develop tiny fractures, sapping battery performance and shortening battery life.

"Lithiation and delithiation should be homogenous and uniform," said Yiyang Li, a doctoral candidate in Chueh's lab and co-lead author of the paper. "In reality, however, they're very non-uniform. In our better understanding of the process, this paper lays out a path toward suppressing the phenomenon."

For researchers hoping to improve batteries, like Chueh and his team, counteracting these detrimental forces could lead to batteries that charge faster and more fully, lasting much longer than today's models.

This study visualizes the charge/discharge reaction in real-time - something scientists refer to as operando - at fine detail and scale. The team utilized brilliant X-rays and cutting-edge microscopes at Lawrence Berkeley National Laboratory's Advanced Light Source.

"The phenomenon revealed by this technique, I thought would never be visualized in my lifetime. It's quite game-changing in the battery field," said Martin Bazant, a professor of chemical engineering and of mathematics at MIT who led the theoretical aspect of the study.

Chueh and his team fashioned a transparent battery using the same active materials as ones found in smartphones and electric vehicles. It was designed and fabricated in collaboration with Hummingbird Scientific. It consists of two very thin, transparent silicon nitride "windows." The battery electrode, made of a single layer of lithium iron phosphate nanoparticles, sits on the membrane inside the gap between the two windows. A salty fluid, known as an electrolyte, flows in the gap to deliver the lithium ions to the nanoparticles.

"This was a very, very small battery, holding ten billion times less charge than a smartphone battery," Chueh said. "But it allows us a clear view of what's happening at the nanoscale."

Significant advances

In their study, the researchers discovered that the charging process (delithiation) is significantly less uniform than discharge (lithiation). Intriguingly, the researchers also found that faster charging improves uniformity, which could lead to new and better battery designs and power management strategies.

"The improved uniformity lowers the damaging mechanical stress on the electrodes and improves battery cyclability," Chueh said. "Beyond batteries, this work could have far-reaching impact on many other electrochemical materials." He pointed to catalysts, memory devices, and so-called smart glass, which transitions from translucent to transparent when electrically charged.

In addition to the scientific knowledge gained, the other significant advancement from the study is the X-ray microscopy technique itself, which was developed in collaboration with Berkeley Lab Advanced Light Source scientists Young-sang Yu, David Shapiro, and Tolek Tyliszczak. The microscope, which is housed at the Advanced Light Source, could affect energy research across the board by revealing never-before-seen dynamics at the nanoscale.

"What we've learned here is not just how to make a better battery, but offers us a profound new window on the science of electrochemical reactions at the nanoscale," Bazant said.
-end-
Funding for this work was provided in part by the U.S. Department of Energy, Office of Basic Energy Sciences, and by the Ford-Stanford Alliance. Bazant was a visiting professor at Stanford and was supported by the Global Climate and Energy Project.

SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, Calif., SLAC is operated by Stanford University for the U.S. Department of Energy's Office of Science. For more information, please visit slac.stanford.edu.

SLAC National Accelerator Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

DOE/SLAC National Accelerator Laboratory

Related Batteries Articles:

A seaweed derivative could be just what lithium-sulfur batteries need
Lithium-sulfur batteries have great potential as a low-cost, high-energy, energy source for both vehicle and grid applications.
Batteries from scrap metal
Chinese scientists have made good use of waste while finding an innovative solution to a technical problem by transforming rusty stainless steel mesh into electrodes with outstanding electrochemical properties that make them ideal for potassium-ion batteries.
Better cathode materials for lithium-sulphur-batteries
A team at the Helmholtz-Zentrum Berlin (HZB) has for the first time fabricated a nanomaterial made from nanoparticles of a titanium oxide compound (Ti4O7) that is characterized by an extremely large surface area, and tested it as a cathode material in lithium-sulphur batteries.
Bright future for self-charging batteries
Who hasn't lived through the frustrating experience of being without a phone after forgetting to recharge it?
Making batteries from waste glass bottles
Researchers at the University of California, Riverside's Bourns College of Engineering have used waste glass bottles and a low-cost chemical process to create nanosilicon anodes for high-performance lithium-ion batteries.
Batteries -- quick coatings
Scientists at Oak Ridge National Laboratory are using the precision of an electron beam to instantly adhere cathode coatings for lithium-ion batteries -- a leap in efficiency that saves energy, reduces production and capital costs, and eliminates the use of toxic solvents.
Lighter, more efficient, safer lithium-ion batteries
Researchers from Universidad Carlos III de Madrid and the Council for Scientific Research (initialed CSIC in Spanish) have patented a method for making new ceramic electrodes for lithium-ion batteries that are more efficient, cheaper, more resistant and safer than conventional batteries.
Clarifying how lithium ions ferry around in rechargeable batteries
IBS scientists observe the real-time ultrafast bonding of lithium ions with the solvents, in the same process that happens during charging and discharging of lithium batteries, and conclude that a new theory is needed.
A new approach to improving lithium-sulfur batteries
Researchers from the University of Delaware and China's Northwestern Polytechnical University, Shenzhen University and Hong Kong Polytechnic University have demonstrated a new polysulfide entrapping strategy that greatly improves the cycle stability of Li-S batteries.
Looking for the next leap in rechargeable batteries
USC researchers may have just found a solution for one of the biggest stumbling blocks to the next wave of rechargeable batteries -- small enough for cellphones and powerful enough for cars.

Related Batteries Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#530 Why Aren't We Dead Yet?
We only notice our immune systems when they aren't working properly, or when they're under attack. How does our immune system understand what bits of us are us, and what bits are invading germs and viruses? How different are human immune systems from the immune systems of other creatures? And is the immune system so often the target of sketchy medical advice? Those questions and more, this week in our conversation with author Idan Ben-Barak about his book "Why Aren't We Dead Yet?: The Survivor’s Guide to the Immune System".