Nickel-metal hydride: the battery tech of the future?

NiMH Eneloop Batteries

Conventional wisdom has it that lithium-ion batteries are the state of the art, and that nickel-metal hydride chemistry, which is used in most conventional hybrids (some of the newer Prius models now use Li-ion), is pretty much obsolete.

However, scientists at BASF believe that NiMH technology still has much to offer. According to MIT Technology Review, the company recently developed a NiMH battery with double the storage capacity of the traditional kind, comparable to Li-ion. And they hope to improve that even more, perhaps by a factor of eight. Their goal is to produce a battery with a cost of $146 per kWh, roughly half that of the cheapest Li-ion batteries.

Lithium-ion batteries are lighter and more compact. But nickel-metal hydride batteries are inherently safer. Because they don’t include flammable liquids, they don’t catch fire if they overheat or are overcharged, so they don’t require the complex cooling and safety systems that Li-ion batteries do. Safety systems can add about 25 percent to the cost, and 50 percent to the weight, of a Li-ion battery pack, according to the US Advanced Battery Consortium.

There’s no question that Lithium-ion cells have superior specific energy – as much as 230 Wh/kg. But that advantage can become a moot point when one factors in the added weight of the safety systems, and the fact that much of the energy is held in reserve to maximize battery life. One analysis found that the total usable amount of storage in Li-ion batteries is between 60 and 120 Wh/kg.

 SEE ALSO: How do the inherent challenges of designing lithium-ion battery packs compare to NiMH?

 

Source: MIT Technology Review
Image: NiMH Eneloop Batteries by Dominik Schwind (CC BY 2.0)

  • jstack6

    NiMH have also been very poor in the heat so they will also need cooling. Lithium is lower in cost ,longer lasting and the best of the two.

    • Collin Burnell

      Wasn’t it (early) Lithium based batteries that did poorly in the heat? (Leaf)
      Do you have an example of heat related degradation in NiMH?

  • Benjamin Nead

    Heat is the enemy of just about any current generation battery formula, Collin. Jim and I both live in Arizona and observed first-hand the Leaf battery heat issues in 2012. We were also recently chatting online on a regional EV email group about NiMH cells. One of the other people there advanced the new BASF information in the above article and this prompted some first hand user experiences regarding NiMHs in hot climates.

    All of this was brought up because a member of the Tucson Electric Association (that’s my club) is currently resuscitating the NiMH pack in a late 90’s vintage Ford Ranger pickup truck. This rare stock EV was purchased from a municipality in the San Francisco bay area and sat idle for many years without regular discharging/charging. The vehicle was flatbedded down here, the pack removed from the truck and partially disassembled, so to expose all 250 individual cells. Much of last Saturday found a group of us measuring voltage of these cells and cataloging the results. The research the owner of this vehicle did before launching in on this project confirmed that, while NiMH is stable and the cells can last for many years, heat is something to avoid if possible.

    Perhaps the missing element in the BASF story is that NiMH cells for EV use were essentially banned for a time . . .

    http://en.wikipedia.org/wiki/Patent_encumbrance_of_large_automotive_NiMH_batteries

    So, it appears that BASF purchased the Ovonics/Chevron patents 3 years ago. But one has to wonder how well NiMH will do in the modern EV marketplace. If durability in temperature extremes is an issue and absolute energy density is a secondary importance (but better than NiMH is desired,) we’ve already got lithium titanate . . .

    http://en.wikipedia.org/wiki/Lithium%E2%80%93titanate_battery

    i’m going to assume that batteries with both temperature extreme tolerance and
    high energy density are on the horizon, such the solid state cells from Sakti3 and others.

    The world of batteries doesn’t stay still for very long, especially with all the research dollars being spent over the past 7 years or so.