High Energy Density Battery Cells Brings Performance Trade-Offs Of Durability And Chargeability

1 year ago by Mark Kane 19

How about ultimate battery pack for electric cars?

How about ultimate battery pack for electric cars?

Masato Origuchi, lithium-ion battery chef of Renault (formerly at Nissan) made an interesting presentation about electric cars and batteries in 2015 that we felt we should re-visit.

In the second part of the video (above – from 16:00), Origuchi describs the trade-offs of increasing energy denisty.

Carmakers and battery manufacturers are working hard to increase the lithium-ion cell energy density in order to store more energy in the same size volume and weight – because that best enables increased range of electric cars without adding further size or mass to the battery pack.

More energy dense batteries are needed to be equally as safe as its predecessors.  Despite batteries that store much more enegy (for example twice more) in the same volume, the power output remains similar.

And here comes the drawbacks – durability and chargeability.

The first drawback durability indicates that higher energy dense lithium-ion cells are needed to be able to charge and discharge a smaller number of times. If we double the range via density but also cut durability at the same time, then there is a disadvantage to higher density in this scenario.  If the durability is too big of an issue, then the further problem is that the longer-range cars (using higher density cells) lend themselves to being driven more than first generation 80-100 miles cars, so the calendar end-of-life point under this type of scenario would be exaggerated further.

In case of chargeability, higher energy dense batteries are not able to be recharged as quick as lower energy dense batteries. Which speaks to the second part of the same problem, that we would need twice the charging power to recharge a car in the future with a double-sized battery.

High energy denisty battery cells brings performance trade-offs of durability and chargeability

High energy denisty battery cells brings performance trade-offs of durability and chargeability

Some controversy comes from one of the next slides on which Origuchi shows that long-range cars (for example Tesla) could be equipped with lithium-ion cells with four times lower durability (2,000 cycles in ZOE vs 500 cycles in long-range car) over 40 MWh energy used.

We are not sure whether we should draw far-reaching conclusions from this slide, as it was only a general presentation about the need for a lower number of cycles using higher energy cells (also an especially important drawback of higher energy dense lithium-sulfur batteries). We believe Masato Origuchi intention was not to center out Tesla in this case, or to suggest a fractional durability compared to today’s more common lower density cells.

High energy denisty battery cells brings performance trade-offs of durability and chargeability

High energy denisty battery cells brings performance trade-offs of durability and chargeability

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19 responses to "High Energy Density Battery Cells Brings Performance Trade-Offs Of Durability And Chargeability"

  1. They aren’t saying less durability, they are saying less charge cycles needed to dispense the energy represented by that curve given the battery capacity. I think the graph isn’t linear because the tesla is a less efficient car than the Zoe (ie more battery capacity to travel the same distance). Looks like the wrong conclusion was drawn in the article.

    1. GasBag says:

      The graph isn’t linear because the number of deep cycles required isn’t linear. This graph is not snout anyone’s chemistry or capability. it is about what the requirements of a battery with a given AER range are. Wat he is saying with this graph is short range EVs have a stringent requirements because they will be deep cycled more frequently.

      1. Pushmi-Pullyu says:

        Now here is someone who clearly has been paying attention.

        Thank you.

      2. deborah oo7.5 and 3/4 says:

        Thank you for the info 🙂

  2. DonC says:

    I think you’ve misinterpreted the presentation. All he was saying is that if you double the range then you need half the number of cycles to go the same distance (which he stated as MWh). This is just arithmetic. If you go 1000 miles, and your battery can deliver 100 miles of range, then you need 10 cycles. If your battery delivers 500 miles of range you only need 2 cycles (Miles Driver/Battery Range).

    His comments about the C-rate weren’t clear to me. He said that doubling the capacity halved the C rate. I wasn’t sure if this was because CHAdeMO involved a maximum charger of if the chemistry limited the kW which could be used. His comment that we needed a better chemistry suggested the latter.

    1. Ambulator says:

      Both Renault and GM have turned to LG Chem for batteries. I suspect the charge rate limitations they are pointing out is what is keeping the Bolt down close to 1C charging.

  3. Anthony says:

    Larger packs make cyclabliltiy less of a concern – 1,000 cycles on an 85 mile pack is 85,000 miles, but 800 cycles on a 250 mile pack is 200,000 miles.

    Same goes for chargability – the same charging rate (0.5C, 1C, 2C – not power/kW) on a larger pack yields more miles per hour of charging. With a nearly 300 mile pack on the new top end Teslas and charging stations only 150 miles apart, it means you can keep the battery in the fast-charging zone from station to station (10% to 80%).

    1. MikeG says:

      This is a great point and why cars that want to match parity with ICE vehicles will need closer to 500 mile range, due to different characteristics of the charging/refueling.

      Since recharging EVs looks like a tapered straw where the inflow of charge is greatest at low state of charge and slowly tapers to nothing at full charge, no one would want to wait to continue their trip for the last 20% of energy to fill.

      Also since vehicle range is reduced in colder weather, 500 miles of charge may be only 300 in cold weather. With current battery sizes, winter travelling with an EV becomes more difficult.

      1. agzand says:

        Does it make sense to carry a 500 mile range battery ALL THE TIME for an once or twice a year trip that is longer than 300 miles? I don’t think so. It is a waste. I don’t think increasing range beyond 250 miles makes much sense because most people take a break after that kind of drive. What we need is more charge points and cheaper batteries.

        1. mr. M says:

          Depends on the hastle & price you gona have with renting a car for your 500 mile trip.

    2. SJC says:

      It may be safe to assume that many charge every night, deep cycles are few.

  4. Djoni says:

    Well of course denisty is pretty close to disentry, so it has negative effect!

    Please correct this mistake.

  5. pjwood1 says:

    VW buying back cars. Can I get a PHEV sales “Hey-Yo!!”

    1. mr. M says:

      PHEV sales HEY-HO!

  6. Alex says:

    Most important, double driving range of Nissan Leaf and Renault Zoe! If you put it together with this press release from 2012:

    “This agreement targets the development of next-generation of batteries for production in early 2017.”

    And with the fact that Nissan Europe import the 30 kWh battery from Japan and is preparing Sunderland for “next gen cell”, than you all will come to conclusion Renault-Nissan will double range 2017 and there will be no competition!

  7. agzand says:

    Well, a Tesla battery doesn’t need to handle the same number of charge cycles as leaf. If they both travel the same distance Tesla will undergo 1/4 of full charge cycles.

  8. Bill Howland says:

    Seeing as Nissan in general has made the worst performing battery of all the popular EV’s, and that their engineers laughed at the Volt’s ‘overdesign’, when the Nissan basically failed and the Volt’s gets flying colors, I wonder why I should pay any more than cursory attention to what this dude says?

  9. mr. M says:

    40MWh is at average consumption 15-25kWh/100km a total range of 266.666-160.000 km (~200.000km average).

  10. Apkungen says:

    Teslas batteries have less durable cells than nissan for example. That’s just facts. But tesla could drive the same distance on say 500 cycles as nissan can do on 1500 cycles since it has a third of teslas range.