Navigation Links
Better batteries
Date:11/14/2011

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.

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.


'/>"/>

Contact: Megan Fellman
fellman@northwestern.edu
847-491-3115
Northwestern University
Source:Eurekalert

Related biology news :

1. Army can boost mission success by better managing
2. Efavirenz-based initial therapies associated with better outcomes in HIV-infected adults
3. Caltech scientists engineer supersensitive receptor, gain better understanding of dopamine system
4. Better beer: College team creating anticancer brew
5. Building a better bee
6. Men are better at detecting infidelities
7. Sniffing out a better chemical sensor
8. Sibling study could lead to better treatments for inherited form of colon cancer
9. Soybean grant gives researchers tools to unravel better bean
10. EPA and USDA should create new initiative to better monitor nutrients
11. In the animal world, bigger isnt necessarily better
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:1/22/2016)... Jan. 22, 2016 ... of the "Global Biometrics Market in ... offering. --> http://www.researchandmarkets.com/research/p74whf/global_biometrics ) ... "Global Biometrics Market in Retail Sector 2016-2020" ... --> Research and Markets ( http://www.researchandmarkets.com/research/p74whf/global_biometrics ...
(Date:1/20/2016)... SAN JOSE, Calif. , Jan. 20, 2016 ... leading developer of human interface solutions, today announced ... touch controller solution for wearables and small screen ... appliances such as printers. Supporting round and rectangular ... the S1423 offers excellent performance with moisture on ...
(Date:1/13/2016)... , January 13, 2016 /PRNewswire/ ... announced the addition of the  "India ... Estimation & Forecast (2015-2020)"  report ... http://www.researchandmarkets.com/research/7h6hnn/india_biometrics ) has announced the addition ... Identification Market - Estimation & Forecast ...
Breaking Biology News(10 mins):
(Date:2/9/2016)... DelveInsight,s, "Protein-Tyrosine Phosphatase ... in depth insights on the pipeline drugs ... Phosphatase 1B (PTP1B) Inhibitors. The DelveInsight,s Report ... of development including Discovery, Pre-clinical, IND, Phase ... Report covers the product clinical trials information ...
(Date:2/8/2016)... February 8, 2016 ... Limited, an innovation-driven oncology company developing next generation ... toxic, today announced that chairman emeritus of Tata ... in the company as part of the first ... existing investors Navam Capital and Aarin Capital. ...
(Date:2/8/2016)... ... 08, 2016 , ... Information Management Services ( IMS ) is pleased to ... completely new technical foundation and is so significant it was endowed with a new ... speed for search results, a streamlined layout and a more intuitive format for navigating ...
(Date:2/8/2016)... an active R&D program for the development of future natural ... a unique research and development center in Israel ... products. Stockton has a variety of ... and is active in more than 35 counties worldwide. ... flagship product Timorex Gold ® is used ...
Breaking Biology Technology: