The holy grail of battery design

Battery cathodes have long been made of Lithium. Anodes (the part of the battery that discharges the electrons to race around their circuit) are another story.

During charging, the positively charged lithium ions in the electrolyte are attracted to the negatively charged anode, and the lithium accumulates on the anode. Today, the anode in a lithium ion battery is actually made of graphite or silicon.

Engineers would like to use lithium for the anode, but so far they have been unable to do so. That’s because the lithium ions expand as they gather on the anode during charging.

All anode materials, including graphite and silicon, expand somewhat during charging, but not like lithium. Researchers say that lithium’s expansion during charging is “virtually infinite” relative to the other materials. Its expansion is also uneven, causing pits and cracks to form in the outer surface, like paint on the exterior of a balloon that is being inflated.

The resulting fissures on the surface of the anode allow the precious lithium ions to escape, forming hair-like or mossy growths, called dendrites. Dendrites, in turn, short circuit the battery and shorten its life.

Stanford scientists have solved this problem, using carbon nano spheres that sit on top of the lithium anode.

The Stanford team’s nanosphere layer resembles a honeycomb: it creates a flexible, uniform and non-reactive film that protects the unstable lithium from the drawbacks that have made it such a challenge. The carbon nanosphere wall is just 20 nanometers thick. It would take about 5,000 layers stacked one atop another to equal the width of single human hair.

This means batteries that don’t degrade with repeated charge/discharge cycles, and batteries that are an order of magnitude more efficient. This also means a safer battery (no more battery overheating), much longer and more efficient phone batteries, and electric cars that can go 300 miles on a charge.

  • DanielSw

    Let’s hope Tesla/Panasonic can incorporate this into their battery manufacturing some day!

    • Dave

      It will not be soon, this is many years off due to efficiency (still only 99% and needs to be 99.9%). In addition, I believe Lithium is much more rare than the graphite used today. But it is exciting nonetheless.

  • Dave

    Battery cathodes have long been made of Lithium.

    This is not accurate – cathodes are not made up of mostly lithium – usually they are mostly nickel-cobalt, cobalt, iron phosphate, etc. The lithium ions are in the electrolyte solution between the anode and the cathode. I’m not a chemist, but I’ve watched a lot of videos to learn as much as possible about my Model S because I get asked a LOT of questions, especially while “filling up” at the Superchargers. Also, many skeptics will go off on the Tesla battery being bad for the environment and using up rare earth metals, so I need to be equipped to shoot them down with the facts. 🙂 The Model S cells are made of mostly nickel, and there is very little lithium used by percentage.

    • Just curious: What is your success rate in using facts to counter prejudice?

      • Dave

        Well, it’s not that high, but you know what does have a high success rate? A simple test ride. I can’t tell you the number of skeptics I’ve converted after just 1 mile of driving. They get the same grin on their face as everyone else and then start to ask questions of interest like “so HOW long can you go on a charge” and “how much did you say you paid”? Lol. It’s fun.

        • Sounds like so much fun. I’ll just have to make do with my Prius for now.

          • Dave

            That is what I’m coming from – a 2005, i love(d) my Prius and it was good to me.I know it’s unfair to compare the two, but man, now when I get in my Prius it feels like I stepped back in time by about 100 years :). But it’s actually still more comfortable and I still love it, like an old reliable friend.

          • Lee Fyock

            I drove a Prius for 8 years before leasing a Nissan Leaf. It’s so much fun. The acceleration is impressive (compared to the Prius) and there’s zero lag when stomping the accelerator. Never having to visit the gas station for gas, or oil, or radiator fluid, or anything else, is awesome.

            With regard to the Tesla, I couldn’t bring myself to pay that much for a car. I leased the Leaf rather than buying it because the lease is crazy cheap ($300/month) and because I hope and expect battery tech to get better more quickly than an ownership cycle.

            When Tesla comes out with their lower-cost model in a few years, I’ll look at them again. They’re definitely sweet machines.

    • Envy. Pure envy. 🙂

      • Dave

        Sorry, I can’t help it! Not bragging, just excited. I would gladly give any loopers a ride, in the NYC area (this summer) or Orlando area (this fall).

  • has article on metal-air as the next big thing.

    “Honda received a high evaluation for a battery that uses a complex oxide including yttrium (Y) and manganese (Mn) for the positive electrode. Eveready Battery focuses on technologies that prevent the deterioration of battery durability. Toyota owns technologies that prevent the deterioration of battery performance at the time of charge/discharge and realize high-efficiency discharge. Panasonic gives priority to electrodes for oxygen reduction, and Canon focuses on the development of long-life batteries that prevent crystals from generating.

    “Metal-air battery” is a general term for batteries that use oxygen in the air for the reaction material of the positive electrode and a metal for the reaction material of the negative electrode. The energy density of the battery is higher than that of lithium-ion batteries, which are commonly used. Therefore, it is expected to be used as a next-generation battery for electric vehicles (EVs) and plug-in hybrid vehicles (PHVs).”