A proven and affordable solid state battery is widely seen as the electric mobility breakthrough that will finally put the nail in fossil fuel’s coffin. While solid state batteries have many advantages over the lithium-ion batteries in use today, there are also a lot of things that need to be worked out before they are ‘ready for prime time’.
Now researchers at Samsung, one of the world’s largest EV battery manufacturers, have published a paper detailing a type of solid state battery that could have double the storage capacity of lithium-ion batteries, and therefore give double the range to electric cars – and electric boats.
There are three basic parts of a battery: two electrodes – the positive cathode, the negative anode – and the electrolyte, a medium that lets electrons flow from one electrode to the other.
In a lithium-ion EV or boat battery the electrolyte is liquid – a lithium salt in a solvent – and the electrodes are made out of different solid substances. Some form of carbon is usually used for the anode and some kind of metal or metal oxide for the cathode.
Solid state battery provides more energy density
A solid state battery is called that because the electrolyte is solid. Since solids are more dense than liquids, it means the battery can have a higher energy density – more energy can be stored in the same volume of material.
The way energy density is measured is kilowatt hours per litre, and it’s not just batteries that have energy densities, all fuels do. For instance gasoline/petrol has a density of roughly 9,500 watt hours per litre while the best li-ion batteries have a density of about 700 watt hours per litre (Wikipedia).
What higher energy density means when it comes to powering an electrical car is you can have a lighter, smaller battery that gives the car the same range – or the same size battery that gives the car more range. For an electric boat that has to float on the water instead of rolling along the ground, this idea of lighter, more energy dense batteries is even more important.
Overcoming the dendrite problem
There are lots of good things about using lithium in a battery, but for many solid state technologies being developed it is used in the anode, not as the electrolyte. Unfortunately, when lithium is used in the anode it can cause dendrites, microscopic crystal needles that grow on the lithium anode each charge. That limits the lifespan of the battery, because after a few hundred cycles the dendrites start to build into sharp stalactite-type formations that decrease battery efficiency and cause all kinds of other problems.
So the quest for the ideal solid state battery means research teams all over the world are trying to figure out what the solid electrolyte should be in what combination with what different metals and oxides in the electrodes and then figuring out how to overcome any problem that crops up. It might be dendrites, it might be some other problem if other chemicals are used.
Samsung’s solid state battery breakthrough
This is where Samsung’s advance comes in. Researchers at the Samsung Advanced Institute of Technology started looking into using a silver carbon (Ag-C) composite layer as the anode. For further explanation it’s time to turn it over to an exact quote from the Samsung Institute:
The team found that incorporating an Ag-C layer into a prototype pouch cell enabled the battery to support a larger capacity, a longer cycle life, and enhanced its overall safety. Measuring just 5µm (micrometers) thick (Ed Note: about 1/1600th the thickness of a human hair), the ultrathin Ag-C nanocomposite layer allowed the team to reduce anode thickness and increase energy density up to 900Wh/L. It also enabled them to make their prototype approximately 50 percent smaller by volume than a conventional lithium-ion battery.
To be clear, this is research in a laboratory and difficult to translate into real life use at this stage of its development. But the announcement of the research does go on to say “The prototype pouch cell that the team developed would enable an EV to travel up to 800km on a single charge, and features a cycle life of over 1,000 charges.”
The solid state sweepstakes
The rewards are almost limitless for the team or company that comes up with the solid state battery chemistry (or maybe not solid state) that combines energy density, charging speed and cycling longevity along with ease of manufacture and affordability. Consequently there is a lot of competition.
What is most striking in this race is the variety of solutions being pursued. Plugboats has covered some of them that you may want to find out more about:
- The glass battery developed by John Goodenough, one of the winners of the 2019 Nobel Prize for the invention of the lithium ion battery
- The lithium-sulfur battery from Oxis technologies that has its eye on being used in electric aviation
- The Edison Award-winning Prologium battery that is built with something called 3D Multi Axis BiPolar+ technology
Who knows where the battery breakthrough will come from? (We’ll be reporting next week on another intriguing possibility.) And who even knows if there will be one giant leap forward or a large number of incremental improvements. Colin McKerracher of Bloomberg New Energy Finance pointed out at their 2020 conference that energy density for batteries has almost tripled since 2010 and prices for li-ion have gone down (per kWh) by almost tenfold in the same period.
What we do know is that all of this bodes well for quiet, clean electric boating. Stay tuned!!