A new manufacturing technique developed by materials scientists at the Georgia Institute of Technology could enable solid-state auto lithium-ion batteries to use non-flammable ceramic electrolytes – meaning safer, lighter, and more energy-dense batteries. Their manufacture could use the same production processes as batteries made with traditional liquid electrolytes, saving a lot of time and money.
Melt infiltration technology is a one-step process. Electrolyte materials are used that can be infiltrated into porous, but tightly packed, thermally stable electrodes. The result is “high-density composite materials based on the pressureless, capillary-controlled infiltration of a molten solid electrolyte into porous bodies, including multilayer electrode separator stacks.”
Gleb Yushin, a professor at Georgia Tech’s School of Materials Science and Engineering, stated:
While the melting point of conventional solid-state electrolytes can be between 700 and over 1,000 degrees Celsius, we work in a much lower temperature range of around 200 to 300 degrees Celsius, depending on the composition of the electrolyte. At these lower temperatures, manufacturing is much faster and easier. Materials at low temperatures do not react. The standard electrode assemblies, including the polymeric binder or adhesive, can be stable under these conditions.
Gleb Yushin, a Georgia Tech professor, at an EV charging station on campus. (Photo credit: Allison Carter, Georgia Tech)
The patent-pending manufacturing technology can quickly create high-quality multi-layer cells of any shape or size on a scale using proven possessions and tools optimized for Li-ion over the past three decades. It mimics the inexpensive manufacture of commercial Li-ion cells with liquid electrolytes, but instead uses solid-state electrolytes with low melting points. The breakthrough should facilitate the proliferation of solid-state batteries and enable manufacturers of electric cars to spend less on cooling systems, thereby saving even more material, dimensions and weight.
Yiran Xiao, a Georgia Tech graduate student, stated:
Melt infiltration technology is the crucial advance. The service life and stability of Li-ion batteries depend heavily on the operating conditions, in particular on the temperature. When batteries are overheated for an extended period of time, they usually start to deteriorate prematurely, and overheated batteries can ignite. This has resulted in almost exclusively electric vehicles (EV) containing sophisticated and quite expensive cooling systems.
Kostiantyn Turcheniuk, co-author and scientist at Georgia Tech, said that higher density cells support longer range:
The developed melt infiltration technology is compatible with a large number of material chemistries, including so-called conversion electrodes. Such materials have been shown to increase the energy density of automotive cells by over 20% now and by more than 100% in the future.
When the automotive industry is ready to move to solid-state batteries, the one discovered in Georgia will be the only viable method of production when it comes to simplicity, speed and containment costs.
The team’s technology is not yet commercially ready, but it will be ready soon. Battery cell prices must drop below $ 70 per kilowatt hour before the electric vehicle market can fully open to consumers, and such battery innovations are critical to that. Cell prices are currently at $ 100 per kilowatt hour.
At the moment, Toyota may be the leader in electric vehicles that use solid-state batteries with fluoride ions. This year, a prototype of a car with a rapidly rechargeable solid-state battery is to be presented.
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