• Oct 29th 2010 at 7:53PM
  • 14
lithium ion battery pack

In a lab at Ohio State University (OSU), scientists, engineers and experts in the chemical field are studying the effects that time has on lithium-ion batteries. The goal: to discover the "hows" and "whys" behind battery aging. Specifically, why do lithium-ion batteries degrade from repeated use and how come this aging process can't be prevented. Preliminary results from the ongoing study suggest that external conditions such as temperature variations and charging rates play only a minor role in battery life. Aging, it seems, begins on the nanoscale level and once the process starts, it is irreversible.

The researchers ripped apart dead batteries to study the materials within and discovered that the finely-structured nanomaterials on the battery's electrode had coarsened. The study further revealed that a fraction of the lithium (which, in its ion form, shuttles charge between the battery's electrodes) was irreversibly lost from the cathode to the anode. Giorgio Rizzoni, director of the Center for Automotive Research at OSU sums up the preliminary findings like this:
We can clearly see that an aged sample versus and unaged sample has much lower lithium concentration in the cathode. It has essentially combined with anode material in an irreversible way.
The researchers suspect that the initial coarsening of the nanomaterials on the battery's electrode eventually leads to its demise. Further testing is underway, but if the initial findings prove to be true, then battery makers will be armed with vital info that could allow them to design future batteries with longer lifetimes. That's something we'd like to see before we get too much older.

[Source: American Institute of Physics]


How Batteries Grow Old

WASHINGTON, D.C. -- 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.

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    • 1 Second Ago
      • 4 Years Ago
      the definition of a battery is that it is electrochemical - while you are right that all produced batteries to date slowly loose material (typ. of the Anode) or lose "ion separation" over time - there is no guarantee that this is forever true.

      Graphene's "fantastic" property is that it is THIN.
      Second, almost ANY form of ultracapacitor has a major leg up on any battery built today in terms of life/longevity - not just Graphene.
      Third, no one to date is promising energy densities out of a graphene based ultracap or any other kind of ultracap (cite an actual reference if you know otherwise) anywhere near advanced Lithium ion or alternative battery ... except for [the famous startup that promised a miracle ultracap last year and... poof, nothing... *crickets*].
      At best, perhaps matching a Lead Acid battery is the current wish/target.

      Is this bad? Yes, in that: there is no way, unless a true miracle happens, that ultracaps will replace batteries in 5-10 years.... in a car.
      Is this good? Yes, in that: that density is enough to create hybrid EV's (meaning: all electric, but part ultracap, part battery: use the ultracap, and beat the hell out of it, for short drives, and braking, and quick "electric station" stops ... and use the battery for extended range and long term storage)
      They could be used today, in fact, in the latter form...

      • 4 Years Ago
      Do you know that a fuelcell last longer then that, cost less then that and is more powerful and cost lest to fuel and pollute less and is lighther and less polluting.

      I said to start producing or at least to give me one fuelcell car with a home hydrogen maker and a solar panel and a windmill.
        • 4 Years Ago
        Double less polluting 4tw!!!

      • 4 Years Ago
      Does the same degradation occur in the newer nano-tubule Lithium Ion batteries?
        • 4 Years Ago
        At smaller scale things can only get worse. The problem with solid-electrode batteries is that their electrodes perform two functions - carry electrons around and serve as "fuel", changing their structure as they charge/discharge. Finer design is likely to be more sensitive to to his process and larger power and energy density won't help either.

        The real challenge will be to develop higher power and energy density batteries that don't sacrifice reliability and safety. Although reliability is not a big concern (you can just come up with a reasonably priced recycling scheme), there is no substitute for safety, other than simply not putting a bomb in a car (same concern applies to capacitors, assuming they'll ever grow to the adequate capacity).
        • 4 Years Ago
        Batteries have an inherent problem that enables them to function but also to age and die. No matter what type of rechargeable battery is considered, they all work with an electrolyte and that is also their problem. The only alternative that I can envision is an ultra super capacitor that would exceed the energy - and power density of present batteries. The only material that I'm familiar with which could accomplish such a task is GRAPHENE. Graphene's electric properties are absolutely fantastic and a capacitor built on graphene would have little to none life impeding attributes. Electrical - and heat conductivity of graphene is more than 100 times better than that of copper. No energy density and no power density anxieties to be envisioned. Ultra capacitors of this wonder material would be the "ultimo ratio". O course there is a problem associated with such an electric storage device as well; it will take at least another five to ten years of R&D until such a device is available on the market. In the mean time, we'll just have to accept batteries with all their pros and cons.
      • 4 Years Ago
      It's nice that a public entity like OSU is investigating this issue, and I hope will publish results that accurately delineate the reasons for battery performance decay. However, battery companies have known for a long time some of the reasons for performance decay. As it turns out, they typically make the batteries only as good as the application requires, or perhaps as good as the consumer will accept. In some cases the added cost of producing a long lasting rechargeable battery make the consumer shy away from the added capability. We live in a throw away society. Why would a person need a battery that lasts five years in their laptop, when they know they will get a new laptop at about the same time?
      • 4 Years Ago
      Man, that is one ugly ass battery pack. What is that from....some car from like the 1950s?
      • 4 Years Ago
      You can start by naming a battery that DOESN'T age.
        • 4 Years Ago
        At what point do they enter the designed failure mode. After all we don't want these batteries lasting to long, it hurts future sales.

        • 4 Years Ago
        It may take 30 years before it starts to show... but it will still age. But kudos to it.
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