You’ve probably seen videos or heard or read about lithium-ion batteries that have exploded or caught fire when overheated. Now a researcher from Tufts University has devised what could be a permanent solution to solve this problem with the invention of a new polymer electrolyte that is neither flammable nor explosive, and paves the way for improvements in next-generation battery design.
Michael Zimmerman, professor of mechanical engineering at Tufts University, is behind the new invention, having spun off a company from his research called Ionic Materials to develop the technology--a solid electrolyte that is among the first to be commercially viable.
“Solid electrolytes are very promising for batteries, but have not been practical until now,” Zimmerman explained to Design News.
Michael Faraday discovered the first solid ion-conductors in 1839, Zimmerman said, but barriers to adoption have historically included the need for high temperatures to function, along with several other properties--including the ability to act as an electrolyte in the cathode and to remain stable against lithium metal.
Researchers have been trying for the last several decades—Zimmerman himself working with polymers for 30 years—to perfect the design for a solid battery electrolyte, he said, to little avail. “Each of the two main classes have issues,” Zimmerman said. “Existing polymers suffer from low conductivity at room temperature, while ceramics are brittle and expensive to manufacture.”
That is, until now. Zimmerman thinks he’s solved the historical problem by focusing on a new polymer material with properties that address all the requirements for a solid electrolyte.
“With this new electrolyte, Ionic Materials has demonstrated solid-state pouch cells with composite LCO (lithium cobalt oxide) and NCM (nickel manganese cobalt) cathodes to become the first large format solid-state battery to function at room temperature, and allow safe battery performance across a broad temperature range,” he said.
The polymer also has the other properties essential to its performance as an electrolyte: High voltage stability, the ability to function as the cathode electrolyte with high active material loadings, and the necessary mechanical properties, Zimmerman added.
|Ionic Materials’ solid polymer eliminates the liquid electrolyte, creating a completely solid battery that still allows lithium ions to pass through it and prevents dendrites from shorting the battery, a common issue with conventional batteries. (Source: Ionic Materials)|
Current batteries are low energy, unsafe, and expensive, which is why researchers have been pursuing the development of different chemistries and technologies, he said. Electrolytes are one area in particular researchers think they can improve battery chemistries, particularly because it’s this material that researchers think has been stunting battery evolution, Zimmerman said.
“Liquid electrolytes are holding them back because of their many problems--they are unstable when the temperature rises, are susceptible to shorts caused by dendrites, and can catch fire and explode under certain circumstances,” he said. “Such drawbacks require expensive safety systems to minimize risk, and they prevent higher-energy-density electrodes and lower-cost electrodes from being used due to instability with the liquid electrolyte.”
The polymer developed by Zimmerman and his company eliminates the liquid electrolyte, creating a completely solid battery that still allows lithium