Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > New technology improves both energy capacity and charge rate in rechargeable batteries

Harold Kung
Harold Kung

Abstract:
Imagine a cellphone battery that stayed charged for more than a week and recharged in just 15 minutes. That dream battery could be closer to reality thanks to Northwestern University research.

New technology improves both energy capacity and charge rate in rechargeable batteries

Evanston, IL | Posted on November 14th, 2011

A team of engineers has created an electrode for lithium-ion batteries -- rechargeable batteries such as those found in cellphones and iPods -- that allows the batteries to hold a charge up to 10 times greater than current technology. Batteries with the new electrode also can charge 10 times faster than current batteries.

The researchers combined two chemical engineering approaches to address two major battery limitations -- energy capacity and charge rate -- in one fell swoop. In addition to better batteries for cellphones and iPods, the technology could pave the way for more efficient, smaller batteries for electric cars.

The technology could be seen in the marketplace in the next three to five years, the researchers said.

A paper describing the research is published by the journal Advanced Energy Materials.

"We have found a way to extend a new lithium-ion battery's charge life by 10 times," said Harold H. Kung, lead author of the paper. "Even after 150 charges, which would be one year or more of operation, the battery is still five times more effective than lithium-ion batteries on the market today."

Kung is professor of chemical and biological engineering in the McCormick School of Engineering and Applied Science. He also is a Dorothy Ann and Clarence L. Ver Steeg Distinguished Research Fellow.

Lithium-ion batteries charge through a chemical reaction in which lithium ions are sent between two ends of the battery, the anode and the cathode. As energy in the battery is used, the lithium ions travel from the anode, through the electrolyte, and to the cathode; as the battery is recharged, they travel in the reverse direction.

With current technology, the performance of a lithium-ion battery is limited in two ways. Its energy capacity -- how long a battery can maintain its charge -- is limited by the charge density, or how many lithium ions can be packed into the anode or cathode. Meanwhile, a battery's charge rate -- the speed at which it recharges -- is limited by another factor: the speed at which the lithium ions can make their way from the electrolyte into the anode.

In current rechargeable batteries, the anode -- made of layer upon layer of carbon-based graphene sheets -- can only accommodate one lithium atom for every six carbon atoms. To increase energy capacity, scientists have previously experimented with replacing the carbon with silicon, as silicon can accommodate much more lithium: four lithium atoms for every silicon atom. However, silicon expands and contracts dramatically in the charging process, causing fragmentation and losing its charge capacity rapidly.

Currently, the speed of a battery's charge rate is hindered by the shape of the graphene sheets: they are extremely thin -- just one carbon atom thick -- but by comparison, very long. During the charging process, a lithium ion must travel all the way to the outer edges of the graphene sheet before entering and coming to rest between the sheets. And because it takes so long for lithium to travel to the middle of the graphene sheet, a sort of ionic traffic jam occurs around the edges of the material.

Now, Kung's research team has combined two techniques to combat both these problems. First, to stabilize the silicon in order to maintain maximum charge capacity, they sandwiched clusters of silicon between the graphene sheets. This allowed for a greater number of lithium atoms in the electrode while utilizing the flexibility of graphene sheets to accommodate the volume changes of silicon during use.

"Now we almost have the best of both worlds," Kung said. "We have much higher energy density because of the silicon, and the sandwiching reduces the capacity loss caused by the silicon expanding and contracting. Even if the silicon clusters break up, the silicon won't be lost."

Kung's team also used a chemical oxidation process to create miniscule holes (10 to 20 nanometers) in the graphene sheets -- termed "in-plane defects" -- so the lithium ions would have a "shortcut" into the anode and be stored there by reaction with silicon. This reduced the time it takes the battery to recharge by up to 10 times.

This research was all focused on the anode; next, the researchers will begin studying changes in the cathode that could further increase effectiveness of the batteries. They also will look into developing an electrolyte system that will allow the battery to automatically and reversibly shut off at high temperatures -- a safety mechanism that could prove vital in electric car applications.

The Energy Frontier Research Center program of the U.S. Department of Energy, Basic Energy Sciences, supported the research.

The paper is titled "In-Plane Vacancy-Enabled High-Power Si-Graphene Composite Electrode for Lithium-Ion Batteries." Other authors of the paper are Xin Zhao, Cary M. Hayner and Mayfair C. Kung, all from Northwestern.

(Source contact: Harold Kung at 847-491-7492 or )

####

For more information, please click here

Contacts:
Harold Kung
847-491-7492


Megan Fellman
(847) 491-3115

Copyright © Northwestern University

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Energy-efficient spin current can be controlled by magnetic field and temperature: SCMR effect simplifies the design of fundamental spintronic components August 20th, 2018

Color effects from transparent 3D printed nanostructures: New design tool automatically creates nanostructure 3D print templates for user-given colors Scientists present work at prestigious SIGGRAPH conference August 18th, 2018

UVA multidisciplinary engineering team designs technology for smart materials: The invention could lead to devices and manufactured goods, such as fabrics, that can dynamically regulate between thermally insulating and cooling August 17th, 2018

Smallest transistor worldwide switches current with a single atom in solid electrolyte: Milestone of energy efficiency in information technology -- Publication in Advanced Materials August 17th, 2018

Graphene/ Graphite

CTI Materials drives nano commercialization with it's patented surfactant free nanoparticle dispersions August 15th, 2018

Flipping the switch on supramolecular electronics August 14th, 2018

Quantum chains in graphene nanoribbons: Breakthrough in nanoresearch August 9th, 2018

Nanotube 'rebar' makes graphene twice as tough: Rice University scientists test material that shows promise for flexible electronics August 3rd, 2018

Chemistry

Flipping the switch on supramolecular electronics August 14th, 2018

Discoveries

Energy-efficient spin current can be controlled by magnetic field and temperature: SCMR effect simplifies the design of fundamental spintronic components August 20th, 2018

Color effects from transparent 3D printed nanostructures: New design tool automatically creates nanostructure 3D print templates for user-given colors Scientists present work at prestigious SIGGRAPH conference August 18th, 2018

UVA multidisciplinary engineering team designs technology for smart materials: The invention could lead to devices and manufactured goods, such as fabrics, that can dynamically regulate between thermally insulating and cooling August 17th, 2018

Smallest transistor worldwide switches current with a single atom in solid electrolyte: Milestone of energy efficiency in information technology -- Publication in Advanced Materials August 17th, 2018

Announcements

Energy-efficient spin current can be controlled by magnetic field and temperature: SCMR effect simplifies the design of fundamental spintronic components August 20th, 2018

Color effects from transparent 3D printed nanostructures: New design tool automatically creates nanostructure 3D print templates for user-given colors Scientists present work at prestigious SIGGRAPH conference August 18th, 2018

UVA multidisciplinary engineering team designs technology for smart materials: The invention could lead to devices and manufactured goods, such as fabrics, that can dynamically regulate between thermally insulating and cooling August 17th, 2018

Smallest transistor worldwide switches current with a single atom in solid electrolyte: Milestone of energy efficiency in information technology -- Publication in Advanced Materials August 17th, 2018

Battery Technology/Capacitors/Generators/Piezoelectrics/Thermoelectrics/Energy storage

Breaking down the Wiedemann-Franz law: In a study exploring the coupling between heat and particle currents in a gas of strongly interacting atoms, physicists at ETH Zurich find puzzling behaviours August 10th, 2018

Carbon is the new black: Researchers use carbon nanotubes to develop clothing that can double as batteries July 10th, 2018

NIST Researchers Simulate Simple Logic for Nanofluidic Computing June 30th, 2018

BNAs improve performance of Li-ion batteries June 27th, 2018

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project