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SAN FRANCISCO， Aug. 5 (Xinhua) -- A team of researchers has devised a way to peer into the electrochemical reaction that fuels lithium-ion battery， the most common rechargeable cell in use today.

The team， led by William Chueh， an assistant professor of materials science and engineering at Stanford University and a faculty scientist at the U.S. Department of Energy's SLAC National Accelerator Laboratory， reported their work a paper published this week in the journal Science.

By visualizing the fundamental building blocks of batteries， namely small particles typically measuring less than 1100th of a human hair in size， the researchers have illuminated a process that is far more complex than once thought.

"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."

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 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 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."

And counteracting the detrimental forces could lead to batteries that charge faster and more fully， lasting much longer than today's models.

The study visualizes the chargedischarge reaction in real-time -- something scientists refer to as operando -- at fine detail and scale， according to a news release from Stanford. 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 Massachusetts Institute of Technology (MIT) who led the theoretical aspect of the study.

The team fashioned a transparent battery using the same active materials as ones found in smartphones and electric vehicles. 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 was quoted as saying. "But it allows us a clear view of what's happening at the nanoscale."

The researchers discovered that the charging process is significantly less uniform than discharge. Intriguingly， they also found that faster charging improves uniformity， which could lead to better battery designs and power management strategies.

"The improved uniformity lowers the damaging mechanical stress on the electrodes and improves battery cyclability，" Chueh said.

Both the method developed by the researchers 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.

"What we've learned here is not just how to make a better battery，" Bazant said， "but offers us a profound new window on the science of electrochemical reactions at the nanoscale."

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