The search for solid state batteries continues in laboratories around the world. The goal is cheaper, longer lasting batteries with higher energy density that don’t come with the risk of fire or explosion that bedevils conventional lithium-ion batteries. If that risk can be reduced or eliminated, the total cost of batteries can be reduced because there will be no need for expensive (and heavy) fire and explosion proof containers to surround the battery cells. Solid state batteries may also require less aggressive cooling systems, which would also save weight and lower costs.
Researchers at the Department of Energy’s Oak Ridge National Laboratory have published a new study in which they report a breakthrough that could bring lithium metal batteries closer to commercial reality. They say they have created a 3D thin film solid state electrolyte made of polymer and a ceramic based composite that is highly conductive.
Typically, solid polymer electrolytes are flexible and cost little to manufacture. That’s good. But they also have poor conductivity. That’s bad. Ceramic electrolytes have high conductivity but are too brittle to be practical. An ORNL research team led by Xi Chen says it has succeeded in making a new type of electrolyte for lithium metal batteries that combines the best features of both polymers and ceramics.
“We combined the advantages of both materials to form a thin composite film,” Xi says. “The film was formed by partially sintering a three-dimensionally interconnected ceramic structure and the polymer filled the pores to make a robust membrane.” The newly created electrolyte is both mechanically robust and has high lithium ionic conductivity at room temperature.
In the abstract to their report, the researchers say, “The main ion transport pathway is through the ceramic network, predicted by modelling and verified by experiments. Owing to the interconnected structure of the ceramic, the composite electrolyte exhibits much improved mechanical strength.”
Solid state batteries are the Holy Grail of battery research. The ORNL discovery may bring them one step closer to being practical for use in the real world.