Solid lithium garnet batteries improve safety

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Researchers at ETH Zurich have developed a non-flammable battery that consists of solid chemical compounds. "Solid electrolytes do not catch fire even when heated to high temperatures or exposed to the air," explained Jennifer Rupp, professor of electrochemical materials at ETH Zurich.

One of the challenges in developing solid-state batteries is to connect the electrodes and electrolyte so that the charges can circulate between them with as little resistance as possible.

The ETH researchers have developed an improved electrode-electrolyte interface with a sandwich-like battery featuring a layer of lithium garnet, which acts as a solid electrolyte.

"During production, we made sure that the solid electrolyte layer obtained a porous surface," said researcher Jan van den Broek. The team then applied the material of the negative pole in a viscous form, allowing it to seep into the pores. Finally, the scientists tempered the battery at 100°C. "With a liquid or gel electrolyte, it is not possible to heat a battery to such high temperatures," van den Broek added.

Thanks to the trick with the pores, the researchers enlarged the contact area between the negative pole and the solid electrolyte, which means that the battery could be charged faster.

"We have, for the first time, built a lithium-ion battery with a solid lithium garnet electrolyte and a solid minus pole made of an oxide-based material. Thus, we have shown that it is possible to build whole batteries based on lithium garnet," said Prof Rupp. This will not only allow batteries to operate at higher temperatures, but also be directly placed on silicon chips.