Computational design strategy extends battery life

Batteries 4 (c) CHARGED

Batteries are wonderful inventions, but like so many things in life, they don’t last. With every charge and discharge cycle, a battery’s capacity is reduced, until eventually it becomes inadequate for its application.

“Why does this degradation occur?” muses Northwestern University’s Christopher Wolverton. “In many cases, something probably happened to the cathode.”

Wolverton has developed a new computational design strategy that can pinpoint optimal materials with which to coat the cathode of a lithium-ion battery, protecting it from degradation and extending the battery’s life.

In “High-throughput computational design of cathode coatings for Li-ion batteries,” published in Nature Communications, Wolverton, Muratahan Aykol and colleagues explain that a cathode is typically composed of a compound containing lithium and oxygen. When the battery’s electrolyte decomposes, it can release hydrofluoric acid, a highly reactive substance that can attack the cathode. This could be one reason why the battery loses capacity over time.

“A coating could serve multiple functions: it could provide a barrier around the cathode, preventing attack from hydrofluoric acid,” Wolverton said. “Or a coating could preferentially react with the hydrofluoric acid, so there’s none left to react with the cathode.”

Earlier in his career, Wolverton developed the Open Quantum Materials Database, which contains information on more than 470,000 compounds. Wolverton’s group scoured the database in search of materials that could be potential barriers to or scavengers of hydrofluoric acid, and ultimately identified 30 top candidates.

“Having a massive database at hand allowed us to find the products of very complex, previously unexplored chemical reactions that determine the coating’s effectiveness,” said Aykol. “Not only can we unveil a list of promising functional coatings, but we are helping our experimental colleagues target their resources to the best candidates.”

Current methods of searching for cathode coatings are slow and limited. Exploring every combination of materials can result in millions, or even billions, of possibilities, far too many to test experimentally.

“There has never really been a design strategy for these coating materials,” Wolverton said. “Computationally, we can quickly screen the vast landscape of possible material combinations to pinpoint 25 compounds that are potentially very promising. Now, 25 is a more manageable number that you could test experimentally.”

 

Source: Northwestern University

  • Eco Logical

    Dr Jeff Dahn of Dalhousie University in Nova Scotia, Canada was recently interviewed on CBC TV. He’s been working on improving Li-ion batteries since 1978 and in June 2016 started working with Tesla in a joint facility that was setup in Nova Scotia. In the interview he said he has been focusing on eliminating “unwanted parasitic reactions” that degrade the electrodes. The results of his research will be included in the Tesla Model 3’s 2170 batteries resulting in lower cost, higher energy density, and cycle life of several decades (20 ~ 30 years).

    • Brian

      Neither the CBC article, or an electrek.co article that quoted it, confirms that Dr. Dahn’s work will be incorporated into the 2170 cell to be used in Model 3. Electrek’s article, published on Feb. 7, states they will attempt to confirm this with Tesla and will update the article if they can, but this hasn’t happened to date (8 days later). As a day 1 Model 3 reservation holder, I’m hopeful that this is the case and would love to see it confirmed. Do you have another source that confirms this?

      • Michael B

        The results of his research […] resulting in lower cost, higher energy density, and cycle life of several decades (20 ~ 30 years).

        I don’t think these are so much the results of his research so much as the aims of it. And I believe they do have priority: 1.) lower cost, 2.) longer life span, and then 3.) higher energy density.

        He mentioned that they were “making good headway, already”, but did not say anything about the results of it being incorporated into 2170s or Model 3. So yes, while I hope so too, I’d like to see the source for such an assertion!

      • Eco Logical

        Jeff Dahl was recently on a CBC TV show called “On The Money” (I couldn’t find a video) where he was asked if his research was in the new 2170 cells … he said “No, not the current 2170 cells for energy storage”. But, the host asked him when his research would be used in Tesla products and his answer was admittedly vague but nevertheless promising, he said the research is going well and “should” make it into the Model 3 but emphasized that determining cycle life is time consuming since they are trying make projections for decades of use.

        • Brian

          Eco Logical, thanks for the update!

  • Robert Cattle

    Great to see entropy being reduced, especially in an 8000 + cell battery of “individuals”
    In my days cells/ batteries were an art with proven life cycles tested over real lifetimes.
    It’s not just the cycle life on freeways but the rugged uneven roads over that wide temperature range.
    Do hope the Arizonan batteries are fit for off road vibrations in some Alaska + locations.
    IE real life tests.

  • EVman88

    They also charge to 3.55 instead of 3.65 to help lengthen battery life.