How batteries grow old

WASHINGTON, D.C., (Oct. 19, 2010) -- In a laboratory at Ohio State University, an ongoing experiment is studying why batteries lose their ability to hold a charge as they age -- specifically lithium-ion batteries, which have generated a lot of buzz for their potential to power the electric cars of the future.

Preliminary results presented today at the AVS 57th International Symposium & Exhibition, taking place this week at the Albuquerque Convention Center in New Mexico, suggest that the irreversible changes inside a dead battery start at the nanoscale.

Yann Guezennec and Giorgio Rizzoni of OSU developed new experimental facilities and procedures to charge and discharge commercially-available Li-ion batteries thousands of times over many months in a variety of conditions designed to mimic how these batteries are actually used by hybrid and all-electric vehicles. Some of the batteries were run in hot temperatures like those in Arizona; others in colder conditions similar to those in Alaska.

To understand the results of this testing, Bharat Bhushan, Suresh Babu, and Lei Raymond Cao studied the materials inside of the batteries to help determine how this aging manifests itself in the structure of the electrode materials.

When the batteries died, the scientists dissected them and used a technique called infrared thermal imaging to search for problem areas in each electrode, a 1.5-meter-long strip of metal tape coated with oxide and rolled up like a jelly roll. They then took a closer look at these problem areas using a variety of techniques with different length scale resolutions (e.g. scanning electron microscopy, atomic force microscope, scanning spreading resistance microscopy, Kelvin probe microscopy, transmission electron microscopy) and discovered that the finely-structured nanomaterials on these electrodes that allow the battery rapidly charge and discharge had coarsened in size.

Additional studies of the aged batteries, using neutron depth profiling, revealed that a fraction of the lithium that is responsible, in ion form, for shuttling electric charge between electrodes during charging and discharging, was no longer available for charge transfer, but was irreversibly lost from the cathode to the anode.

"We can clearly see that an aged sample versus and unaged sample has much lower lithium concentration in the cathode," said Rizzoni, director of the Center for Automotive Research at OSU. "It has essentially combined with anode material in an irreversible way."

This research is being performed by Center for Automotive Research at OSU in collaboration with Oak Ridge National Laboratory and the National Institute of Standards Technology.

The researchers suspect, but cannot yet prove, that the coarsening of the cathode may be behind this loss of lithium. If this theory turns out to be correct, it could point battery manufacturers in the right direction for making durable batteries with longer lifetimes.

The presentation, "Multi-scale Characterization Studies of Li-ion Batteries" is at 6:00 p.m. on Tuesday, October 19, 2010.
ABSTRACT: http://www.avssymposium.org/Open/SearchPapers.aspx?PaperNumber=AS-TuP-9

The AVS 57th International Symposium and Exhibition is being held October 17-22, 2010, at the Albuquerque Convention Center, in Albuquerque, New Mexico. The meeting includes more than 1,200 talks and posters presented in more than 130 technical sessions. All meeting information, including directions to the Convention Center, can be found at: http://www2.avs.org/symposium/

REGISTRATION -- Staff reporters and professional freelance journalists working on assignment are invited to attend the conference free of charge. Journalist registration instructions can be found at: http://www2.avs.org/symposium/AVS57/pdfs/pressinvite.pdf

The AVS press room will be located in East Lobby of the Albuquerque Convention Center. Press room hours are Monday-Thursday, 8:00 a.m. to 5:00 p.m. The phone number there is 408-205-0595. Press Kits containing company product announcements and other news will be available on CD-ROM in the press room. Also access the online press room at: http://www2.avs.org/symposium/AVS57/pages/press57.html

Complete Program: http://www2.avs.org/symposium/AVS57/pages/tech_program.html
Searchable abstracts: http://www.avssymposium.org/Open/SearchPapers.aspx
Topical Conferences: http://www2.avs.org/symposium/AVS57/pages/tech_topconf.html#EN
Meeting Home Page: http://www2.avs.org/symposium/

The plenary talk, "Carbon Nanotubes and Single Sheet Graphene," which will be at noon on Monday, October 18, 2010 in Ballroom B of the Albuquerque Convention Center. See: http://www2.avs.org/symposium/AVS57/pages/sessions_lecturer.html

AVS promotes communication, dissemination of knowledge, recommended practices, research, and education in a broad range of technologically relevant topics. One way that it does this is by offering special tutorials in areas such as:

- Graphene Tutorial (Sunday, October 17, 2010, 1:00-5:00 p.m.)

- Tutorial on Nanoparticle Characterization and Toxicity: Significant Challenges and Critical Needs (Sunday, October 17, 2010, 1:00-5:00 p.m.)

To access the complete descriptions of these special tutorials, see: http://www2.avs.org/symposium/AVS57/pages/special_tutorials.html

As a professional membership organization, AVS fosters networking within the materials, processing, and interfaces community at various local, national or international meetings and exhibits throughout the year. AVS publishes four journals, honors and recognizes members through its prestigious awards program, offers training and other technical resources, as well as career services.