A group of researchers from Columbia University have created a new technique to make longer-lasting lithium batteries that are safer than our current stock. By combining a solid-state ceramic electrolyte with boron nitrate to separate all the interior components, the research team is opening the door to a new type of lithium-ion battery that could supply 10x the power of today’s current batteries.
Increasing the efficiency of lithium-ion batteries is seen as a key challenge to greater EV adoption, and Columbia University isn’t the only organization going after this major breakthrough.
Replacing caustic liquid electrolytes with solid ceramic
To store electricity, today’s lithium-ion batteries use aluminum and graphite electrodes immersed in an extremely caustic, flammable electrolyte liquid. Positively charged ions move from the positive electrode, through the electrolyte to the negative electrode, where the ions are stored, ready to be used later.
Battery designers and manufacturers must be extremely careful in the design and manufacturing of lithium batteries, as the caustic electrolyte can lead to the batteries going up in smoke, as The Grand Tour’s Richard Hammond found out when he wrecked an electric Rimac supercar.
So why do we continue using such a volatile component in lithium batteries? Well, it’s the best we’ve got right now. Our lithium-ion batteries are miles ahead of lead-acid batteries (the kind most of us have in our gas-powered cars) in both energy density and longevity. Lithium-ion batteries can hold more electricity and last longer. However, today’s lithium batteries could be much, much better than what we have now, say the Columbia researchers.
The research team replaced the typical graphite electrode with lithium metal, which can offer about 10x greater energy density. However, using lithium leads to the formation of dendrites – protrusions that can puncture the separator between the two electrodes, causing a potentially fiery short circuit.
To fix this dendrite issue, Cheng and fellow researchers looked to solid ceramic to replace the dangerous electrolyte fluid. Ceramic actually has two key benefits over fluid electrolytes. First, it’s much more stable, so the battery is less prone to catch fire. Second, ceramics suppress the growth of those dangerous dendrite formations. By using solid ceramic electrolyte, manufacturers can coat electrodes in lithium metal and take advantage of the material’s much higher energy density.
Other researchers and manufacturers have looked to ceramics for a solid-state electrolyte, but unfortunately, lithium metal easily degrades ceramic and other solid-state materials, so until now no manufacturer has actually been able to use the more efficient material in their batteries.
The Columbia team solved the problem by sandwiching a sheet of ultra-thin boron nitride (which doesn’t react with lithium) between the solid ceramic electrolyte and the lithium metal as a protective layer. At just 5 – 10 nanometers thick, the layer is just a small fraction of the width of a human hair (which is about 100,000 nanometers thick).
Report author Qian Cheng said,
“Lithium metal is indispensable for enhancing energy density and so it’s critical that we be able to use it as the anode for solid electrolytes. To adapt these unstable solid electrolytes for real-life applications, we needed to develop a chemically and mechanically stable interface to protect these solid electrolytes against the lithium anode.
It is essential that the interface not only be highly electronically insulating, but also ionically conducting in order to transport lithium ions. Plus, this interface has to be super-thin to avoid lowering the energy density of batteries.”
With their product, the Columbia researchers are potentially killing two birds with one stone. Lithium metal can hold much more electricity than graphite, but the dendrite problem has left manufacturers scratching their heads. With Columbia’s research, the ceramic electrolyte creates a stable battery – much safer than our current technologies – and the boron nitride allowed them to utilize lithium metal for greater energy density. Safer and more energy? It could be the perfect mix.
Better batteries can lead to greater EV adoption
If EVs, which overwhelmingly utilize lithium-ion batteries, are truly to become dominant over gas-powered vehicles, manufacturers need to overcome two of EVs’ key challenges – their higher cost and limited range. Columbia’s research could potentially help with both of these issues.
While the best electric vehicles are now pushing an astonishing 220-mile range, and some manufacturers are even touting 300-mile ranges in the near future, those numbers pale compared to gas-powered cars.
Yes, most drivers in the US only drive an average of 37 miles a day, so all EVs can easily cover most people’s daily commute. Even still, Toyota Camrys can travel almost 600 miles before needing to fill up. Chevy’s massive Surburban SUV can go 700 miles. That’s 3x further than even the best EVs on the market.
Along with range, EV’s higher purchase price is also holding back growth. Sure, once you’ve bought the car, it’s much cheaper and easier to run. Fuel is cheaper, you don’t need oil changes, and there’s less wear-and-tear with electric motors. But that doesn’t take all the sting out of paying an extra $14k for a mid-sized sedan. For example, the Tesla Model 3, Nissan Leaf PLUS, and Chevy Bolt each sits right around $37,000, but you can buy a base Nissan Altima or VW Golf for around $23k.
EVs of course enjoy cleaner emissions and better acceleration, but you’re still paying higher upfront costs for less convenience. It’s a hard sell, even if EVs lower operating costs allow the owner to eventually break even over the lifetime of the vehicle.
More energy dense batteries can help solve both these problems. Greater energy density allows manufacturers to install fewer batteries yet still enjoy the same range, lowering costs and weight (and by extension increasing range). On the flip side, with greater energy density, manufacturers could install the same amount of batteries, but increase the available range.
Solid-state and lithium metal are the next step in batteries
You can see why lithium metal, with its promise of huge gains in energy density, is so alluring.
The research team at Columbia University is by no means the only group trying to figure out how to increase energy density in lithium-ion batteries. Like Columbia, universities and manufacturers around the world are actively designing and testing new solid-state and lithium metal batteries, each with their own focus.
Earlier this year, Rice University reported that adding red phosphorus on the battery separator in lithium metal batteries can detect when dendrites form, then alert the battery management system to stop charging the battery.
The University of Tokyo is trying to work the kinks out of solid-state batteries, using high-vacuum manufacturing techniques to diminish impurities to allow electricity to flow more easily through the batteries.
Both solid-state and lithium metal batteries are widely seen as the next big step in battery technology. Like solar panels, battery efficiency probably won’t jump 10x higher all at once. Instead, it will be a slow increase as researchers across the world build on one another’s progress.
Columbia’s research is still in the testing and design phase, and a lot can happen before this becomes commercially available. It’s still likely years away, but a battery that is both safer and more efficient is certainly something to be excited about.
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