Nano
Mon Jun 15, 2020 1:41
Batteries: Nanoscale Hollow Structures
TEHRAN (FNA)- An unexpected property of nanometer-scale antimony crystals -- the spontaneous formation of hollow structures -- could help give the next generation of lithium ion batteries higher energy density without reducing battery lifetime. The reversibly hollowing structures could allow lithium ion batteries to hold more energy and therefore provide more power between charges.

Flow of lithium ions into and out of alloy battery anodes has long been a limiting factor in how much energy batteries could hold using conventional materials. Too much ion flow causes anode materials to swell and then shrink during charge-discharge cycles, causing mechanical degradation that shortens battery life. To address that issue, researchers have previously developed hollow "yolk-shell" nanoparticles that accommodate the volume change caused by ion flow, but fabricating them has been complex and costly.

Now, a research team has discovered that particles a thousand times smaller than the width of a human hair spontaneously form hollow structures during the charge-discharge cycle without changing size, allowing more ion flow without damaging the anodes. The research was reported June 1 in the journal Nature Nanotechnology.

"Intentionally engineering hollow nanomaterials has been done for a while now, and it is a promising approach for improving the lifetime and stability of batteries with high energy density," said Matthew McDowell, assistant professor in the George W. Woodruff School of Mechanical Engineering and the School of Materials Science and Engineering at the Georgia Institute of Technology. "The problem has been that directly synthesizing these hollow nanostructures at the large scales needed for commercial applications is challenging and expensive. Our discovery could offer an easier, streamlined process that could lead to improved performance in a way that is similar to the intentionally engineered hollow structures."

The researchers made their discovery using a high-resolution electron microscope that allowed them to directly visualize battery reactions as they occur at the nanoscale. "This is a tricky type of experiment, but if you are patient and do the experiments right, you can learn really important things about how the materials behave in batteries," McDowell said.

The team, which included researchers from ETH Zürich and Oak Ridge National Laboratory, also used modeling to create a theoretical framework for understanding why the nanoparticles spontaneously hollow -- instead of shrinking -- during removal of lithium from the battery.

The ability to form and reversibly fill hollow particles during battery cycling occurs only in oxide-coated antimony nanocrystals that are less than approximately 30 nanometers in diameter. The research team found that the behavior arises from a resilient native oxide layer that allows for initial expansion during lithiation -- flow of ions into the anode -- but mechanically prevents shrinkage as antimony forms voids during the removal of ions, a process known as delithiation.

The finding was a bit of a surprise because earlier work on related materials had been performed on larger particles, which expand and shrink instead of forming hollow structures. "When we first observed the distinctive hollowing behavior, it was very exciting and we immediately knew this could have important implications for battery performance," McDowell said.

Antimony is relatively expensive and not currently used in commercial battery electrodes. But McDowell believes the spontaneous hollowing may also occur in less costly related materials such as tin. Next steps would include testing other materials and mapping a pathway to commercial scale-up.

"It would be interesting to test other materials to see if they transform according to a similar hollowing mechanism," he said. "This could expand the range of materials available for use in batteries. The small test batteries we fabricated showed promising charge-discharge performance, so we would like to evaluate the materials in larger batteries."

Though they may be costly, the self-hollowing antimony nanocrystals have another interesting property: they could also be used in sodium-ion and potassium-ion batteries, emerging systems for which much more research must be done.

"This work advances our understanding of how this type of material evolves inside batteries," McDowell said. "This information will be critical for implementing the material or related materials in the next generation of lithium-ion batteries, which will be able to store more energy and be just as durable as the batteries we have today."

 

 

 

 

Bottom top
Iran Western Province Kordestan, Amazing Uramanat Village

TEHRAN (FNA)- Uramanat village is located in Kordistan Province of Iran. The village owns a unique rural texture, architecture, lifestyle, and agriculture. And as a prominent example of the integration of man into nature, the inhabitants integrated themselves into the nature through utilization of sharp slopes in agriculture. The surrounding area of Uramanat village boasts magnificent scenery as well as excellent weather, especially in summer. [PHOTOS]
Long Queues in UK as Public Vent Frustration over Coronavirus Testing

TEHRAN (FNA)- Long queues at test center in Edmonton, North London, as public vent frustration over testing. [VIDEO]
California: Drone Footage of Berry Creek after Fire

TEHRAN (FNA)- Aerial images show the devastation in Berry Creek after the North Complex Fire destroyed most of the little town in Northern California on September 9. [VIDEO]
US: Anti-Police Protests Resume in Portland, Police Clash with Demonstrator

TEHRAN (FNA)- Protesters returned to the streets of Portland, following a pause largely due to poor air quality from wildfires on the West Coast. [PHOTOS]
Moria Camp Migrants Pour into Temporary Shelters

TEHRAN (FNA)- Greek police moved hundreds of migrants stranded on the island of Lesbos into a new temporary tent camp more than a week after a fire razed the country's biggest migrant camp. [PHOTOS]
Netherlands: Police Arrest Extinction Rebellion Activists at Amsterdam Protest

TEHRAN (FNA)- Dozens of Extinction Rebellion activists were arrested after staging a protest calling on the Dutch government to take more action to combat climate change, in Amsterdam. [VIDEO]
Spain: Thousands Protest Against Newly-Imposed COVID Restrictions in Madrid Region

TEHRAN (FNA)- Thousands protested in Madrid's Puerta del Sol against the recent announcement made by President of the Community of Madrid, Isabel Diaz Ayuso, of new restrictions on the mobility of people in 37 areas of the city and its metropolitan areas. [VIDEO]
US Flag Burns Outside of Portland Police Bureau during Protests

TEHRAN (FNA)- Protesters in Portland, Oregon, burned an American flag outside police bureau in Portland, Oregon, as anti-racism demonstrations in the city returned to the streets following 10 days of quiet. [PHOTO]
Iranian President: Any US Move to Revive UN Sanctions to Receive Iran’s Firm Response

TEHRAN (FNA)- Iranian President Hassan Rouhani warned of his state's firm response to any US effort to reinstate the UN Security Council sanctions against Tehran.
Iran, Brazil Vow to Broaden Agricultural Cooperation

TEHRAN (FNA)- Iranian Ambassador to Brazil Hossein Qaribi and Governor of the Mato Grosso State of Brazil Mauro Mendes in a meeting in Brasilia underlined the need to develop bilateral relations in the fields of agriculture, extraterrestrial agriculture, and agricultural products.
Millions of Children May Miss Pandemic Food Aid as States Scramble to Meet New Trump Administration Mandate

TEHRAN (FNA)- Millions of low-income children are likely to miss out on special benefits that help their families buy groceries this month because the administration of President Donald Trump has imposed eligibility requirements that prevent some states from getting the payments out before the money expires.
Leader's Aide Describes US Hostility towards Iran As Fruitless Policy

TEHRAN (FNA)- Iranian Supreme Leader’s top advisor for international affairs Ali Akbar Velayati said that the US will not succeed in making other countries follow its hostile policy of reimposing UN sanctions against Iran through the trigger mechanism.
Health Secretary Admits UK at ‘Tipping Point’ as Labour Says PM Must Apologize over COVID-19 Testing Chaos

TEHRAN (FNA)- Health Secretary Matt Hancock warned the UK is at a “tipping point” with coronavirus as he indicated tougher restrictions would be introduced if people do not follow the existing rules.
Majority of Americans Trust Biden over Trump to Choose Next Supreme Court Justice

TEHRAN (FNA)- Just before news broke that Supreme Court Justice Ruth Bader Ginsburg had died, new polls were released that showed a majority of Americans in battleground states trusted Joe Biden over President Donald Trump to choose the next nominee to the nation's highest court.
22 Industrial, Mineral Productions Surge in 5 Months

TEHRAN (FNA)- A sum of 22 major industrial and mineral productions registered growth in the first five months of the current Iranian calendar year (from March 20 to August 21) in comparison with the same period last year, an official with Iran’s ministry of industry said.