Fraunhofer develops a dry anode coating process


A conventional lithium-ion battery cell looks a lot like a jelly roll. A strip of metal is coated with a slurry containing solvents and the materials that actually store electrical charge. Then it needs to be dried before the whole thing is rolled up tighter than seven sisters in a size six swimsuit and stuffed into a metal outer shell. This drying process takes time and consumes a lot of energy. Good but not great, in other words.

The Fraunhofer Institute says it has developed a better way. In a press release Benjamin Schumm from Frauhofer states in normal battery production: “Extremely large machines with very long drying tracks are needed to ensure that the solvent then evaporates. With DRYtraec, we can design this process more efficiently. [Note: we first wrote about this in 2019. Getting from the lab to commercial production is a slow, torturous process.]

The new coating process uses raw materials similar to those used in the traditional suspension process, except that the dry coating technology works without solvents, using a special binder instead. Together, according to Green Car Congress, the materials form a dry mixture which is fed into a calender space – a space between two rollers rotating in opposite directions. The crucial detail is that one of the reels must spin faster than the other. This induces a shear force which ensures that the binder forms threadlike networks called fibrils. “Imagine it as a spider web that mechanically incorporates the particles,” says Schumm.

Pressure and movement combine to form a thin film on the faster rotating roller. The film is then transferred to a second calender space on a current collector sheet which enables both sides to be coated simultaneously without significant additional work. In the final step, the resulting coil is cut to the required size and the individual pieces are stacked as needed to produce the finished battery cell.

DRYtraec has obvious ecological and economic advantages over existing battery electrode coating processes, explains Fraunhofer. Removing toxic solvents and long, energy-consuming dryers from the process benefits the environment. The new process also speeds up production and requires only a third of the space of a conventional solution. The result is lower manufacturing costs.

The range of possible uses for the new technology is not limited to any particular cell chemistry. It can be used on lithium-ion batteries as well as lithium-sulfur or sodium-ion batteries. Frauhofer is even considering solid state batteries, which will be increasingly important in the future. The materials used in solid-state batteries do not tolerate wet chemical processing, making the DRYtraec process ideal for fabricating them as well.

Frauhofer says he’s already in talks with several auto and battery cell manufacturers who plan to build pilot systems. Further research is underway to determine if the DRYtraec process can be used to reduce energy costs and production times for the entire battery cell manufacturing process.

Sometimes you can learn more from the comments on an article than from the article itself. Here is one posted on the Green Car Congress story by someone with username gryf. “Tesla may also be involved in this. Saueressig Engineering is said to have developed this together with Fraunhofer IWS (their specialty is roller equipment). Saueressig Engineering plans to establish a facility in San Antonio, approximately 80 miles from Gigafactory Texas. Combined with the design of the 4680 cell, this process would significantly reduce the cost of the battery. Additionally, Samsung SDI has completed the creation of the first samples of Tesla’s 4680 battery (Samsung is another partner in this research).

We do not know the source of by gryf information, but it is very interesting. The march of progress towards cheaper battery cells is accelerating and fascinating to watch. They say there are three kinds of people in the world: those who make things happen, those who watch things happen, and those who wonder what happened. Very soon, the anti-EVs will find themselves in this last group and will be shocked – SHOCKED! – to see that there are so many electric cars on the road.

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