Researchers have designed a new type of battery, that unlike traditional models containing liquid or gel electrolytes, consists purely of solid chemical compounds and is non-flammable – representing a huge boost for improving battery safety.
Responding to dangers linked to traditional lithium-ion batteries, the team based at the Swiss Federal Institute of Technology in Zurich (ETH), has built a solid alternative which contains only solid-state electrodes and electrolyte.
‘Solid electrolytes do not catch fire even when heated to high temperatures or exposed to the air,’ explained lead researcher and ETH electrochemical materials professor Jennifer Rupp.
Designing solid-state batteries is a challenging process as the electrodes and electrolyte need to be designed in such a way to enable charges to circulate with as little resistance as possible. Now, the ETH team has developed an effective method to achieve this – constructing a battery with a layer of highly conductive lithium garnet, which works as a solid electrolyte between the two electrodes.
‘During production, we made sure that the solid electrolyte layer obtained a porous surface,’ noted co-author Jan van den Broek.
The researchers go on to explain how they applied the material of the negative pole in viscous form, which allowed it to seep through the pores. Finally, they tempered the battery at 100°C. ‘With a liquid or gel electrolyte, it would never be possible to heat a battery to such high temperatures,’ added van den Broek.
Using the porous structure, the team was able to significantly boost the contact area between the negative pole and the solid electrolyte, allowing the battery to be charged at a greater rate.
Professor Semih Afyon also highlighted that while the solid batteries could operate at normal temperatures, at current development state they performed best at 95°C and above as the lithium ions can move more freely.
Afyon suggested that this capability could be applied in battery storage power plants: ‘Today, the waste heat that results from many industrial processes vanishes unused… By coupling battery power plants with industrial facilities, you could use the waste heat to operate the storage power plant at optimal temperatures,’ he said.
Rupp continued: ‘In this work, we have for the first time built a whole 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.’
She hopes that as well as operating batteries at higher temperatures, the technology could also be used to build thin-film batteries, that could be directly placed onto silicon chips. ‘These thin-film batteries could revolutionise the energy supply of portable electronic devices,’ concluded Rupp.