Rapid Charging/Draining Of Lithium-Ion Batteries Less Damaging Than Previously Thought

3 years ago by Mark Kane 9

We divide the ​LFP electrode into 10 representative volumes, each containing 10 ​LFP particles immersed in a liquid electrolyte and connected electronically through the carbon network. A one-dimensional Cahn–Hilliard equation (equation (2)) governs the Li diffusional chemical potential along the a axis of each particle. A Butler–Volmer equation (equation (3)) governs the insertion and removal of Li.

“We divide the ​LFP electrode into 10 representative volumes, each containing 10 ​LFP particles immersed in a liquid electrolyte and connected electronically through the carbon network. A one-dimensional Cahn–Hilliard equation (equation (2)) governs the Li diffusional chemical potential along the a axis of each particle. A Butler–Volmer equation (equation (3)) governs the insertion and removal of Li.”

Nissan Is The Largest Purveyor Of Fast Charging Stations, And Has Recently Donated 400 Units To Be Installed Across Europe

Fast charging of Nissan LEAF

According to an article published in Nature Materials by researchers from Stanford University and the Stanford Institute for Materials & Energy Sciences (SIMES) at the Department of Energy’s SLAC National Accelerator Laboratory, and colleagues from Sandia National Laboratories, Samsung Advanced Institute of Technology America and Lawrence Berkeley National Laboratory, quick charging isn’t as damaging to lithium-ion batteries as previously thought.

The key thing is however in the “as previously thought.”  William Chueh of SIMES, senior author of the article, states:

 “The results challenge the prevailing view that “supercharging” batteries is always harder on battery electrodes than charging at slower rates. The results also suggest that scientists may be able to modify electrodes or change the way batteries are charged to promote more uniform charging and discharging and extend battery life.”

“The fine detail of what happens in an electrode during charging and discharging is just one of many factors that determine battery life, but it’s one that, until this study, was not adequately understood. We have found a new way to think about battery degradation.”

Battery wear and tear occurs from the swelling and shrinking of the negative and positive electrodes during charging and discharging, which on the chemical level means absorbing and releasing ions from the electrolyte.

Per Yiyang Li, lead author of the report:

“For this study scientists looked at a lithium iron phosphate cathode material. If most or all of the nanoparticles in the material actively participate in charging and discharging, they’ll absorb and release ions more gently and uniformly. However, if only a small percentage of particles take in the ions, they’re more likely to crack and get ruined, degrading the battery’s performance.”

“Previous studies produced conflicting views of how the nanoparticles in the cathode material behaved. To probe further, researchers made small coin cell batteries, charged them with different levels of current for various periods of time, quickly took them apart and rinsed the components to stop the charge/discharge process. Then they cut the electrode into extremely thin slices and took them to Berkeley Lab for examination with intense X-rays from the Advanced Light Source synchrotron, a DOE Office of Science User Facility.”

We were able to look at thousands of electrode nanoparticles at a time and get snapshots of them at different stages during charging and discharging. This study is the first to do that comprehensively, under many charging and discharging conditions.

“The results indicating that up to some certain level of charging rate only a small percentage of nanoparticles absorbed and released ions. Then number of nanoparticles absorbing ions start increasing, which limits cell degradation.”

“Analyzing the data using a model developed at MIT, the researchers discovered that only a small percentage of nanoparticles absorbed and released ions during charging, even when it was done very rapidly. However, when the discharge rate increased above a certain threshold, more and more particles started to absorb ions simultaneously, switching to a more uniform and less damaging mode. This suggests that scientists may be able to tweak the electrode material or the process to get faster rates of charging and discharging while maintaining long battery life.”

The project will continue because more experiments are needed, but to our knowledge it seems that high power charging is not much worse for batteries than slow or medium charging. Non-linearity and temperature dependence however requires caution before issuing the final verdict.

Green Car Congress

Tags: , ,

9 responses to "Rapid Charging/Draining Of Lithium-Ion Batteries Less Damaging Than Previously Thought"

  1. Stimpacker says:

    L3 Quick Charging for EV batteries aren’t that bad. Take Tesla’s SuperChargers – those put out about 280A peak (only for a short period of time depending on battery SOC and then rapidly declines). A 85kWh battery pack has 74 cells in parallel. So that’s 3.8A per cell or less than 1.3C charging for less than 20 minutes.

    Bjorn Nyland has a nice video of 0% to 100% SuperCharging on YouTube.

    Real “Quick Charging” to me is something like a charge rate of 2C to 3C, e.g. what the RC guys use. That would be bad for the batteries.

    1. Dr. Kenneth Noisewater says:

      Indeed, which is why Tesla got it right all those years ago, and everyone else flailing around with small batteries and expecting to ‘quick charge’ at rates that normal people would consider acceptable are a bit deluded. A 20kWh battery charging at a useful 100kW would charge at 5C, which causes many if not most LiIon chemistries to spontaneously combust.

      Tesla’s philosophy on EV battery design is inarguably the right answer for current technologies and those out to at least the 2020s: lots of cells, lots of active cooling and advanced management controls.

      1. DaveMart says:

        Nope.

        Here is the 27kwh NMC battery in the Kia Soul:

        ‘Together, the low electrical resistance battery cell, proper battery system thermal control and accurate state-of-charge calculation improve the charging performance, achieving an outstanding ‘fast charge’ time of 25 minutes (100 kW DC) or 33 minutes (50 kW DC). Full recharge time, depending on power source, takes up to five hours (6.6 kW AC).’

        http://www.kia.com/worldwide/about-kia/company/corporate-news-view.aspx?idx=718

        So Kia reckon it will be happy with a 4C charge rate.

        The NMC battery pack with high density projected for the 200 mile GM BEV and others may well be capable of similar performance.

        1. Phr3d says:

          ‘capable’ vs lifespan are the key points. I hesitate to trust Kia’s due diligence in making certain that a 200% C did Not degrade the lifespan of the battery, and further hesiate to trust them to fully support their product if it Does degrade substantially and prematurely. (other companies come readily to mind, regarding design parameters well outside of the norm and apparently substandard research and testing).

          1. DaveMart says:

            It is likely very closely related to the lithium polymer battery they use in the Hyundai Sonata hybrid:
            http://www.greencarcongress.com/2010/03/sonata-hybrid-20100331.html#more

            It looks to be a very tough chemistry.
            Chemistries vary enormously in their ability to handle fast charge, with the Toshiba lithium titanate used in the Honda Fit the champion, but this looks like a close second.

            I did have more details on lithium polymer, but can’t spot the spec sheet off hand.

            Anyway, perhaps the Kia engineers have screwed up big time, but it does not seem likely to me.

            The only ones who have managed that in the present era of electric cars are the guys at Nissan in high temperatures.

    2. GeorgeS says:

      Exactly stimpacker,

      People need to understand the concept of C rate.

      It’s simple for those that don’t know.

      1C means the battery can be recharged in an hour.

      If you are charging the pack at 3 C then it is 1/3 of an hour etc.

      at 6 C it is .1 hour which is 6 minutes

      That’s the C rate you need to target.

      RC batteries can charge at these kind of rates a piece of cake.

      Then it is a current game. you need BIG conductors.

      The S has a fairly easy C rate of 1.4

      So this article really doesn’t apply to the S battery.

      1. Djoni says:

        6 C would make 10 minutes.
        Don’t they?

  2. David Murray says:

    I thought heat buildup was the worst issue.. With proper thermal management, it shouldn’t be a big deal.

  3. Spec9 says:

    This is very encouraging. I’ve been a bit wary of fast charging. But I guess as long as you have a good thermal management system and don’t use it too much, it can work fine.