A new type of lithium-ion conductor could help prevent lithium-ion battery fires.
While easily rechargeable, lithium-ion batteries contain flammable organic solvents that present a risk of fire, as seen in a recall of Apple MacBook Pro replacement batteries or the Boeing 787 Dreamliner aircraft.
Researchers have been trying to develop a battery based on a solid-state material than can conduct lithium ions. Along those lines, a team at Tohoku University in northern Japan used lithium borohydride (LiBH4), an agent used in organic chemistry processes, to create a conductor that could become the basis for a new solid-state battery.
The team focused on the rock salt-type crystal structure of LiBH4 as a potential conductor, but it was only stable under high-temperature, high-pressure conditions.
To make it stable at room temperature, the researchers used a process called doping to add small amounts of LiBH4 to potassium iodide, an inorganic compound used to iodize table salt.
The result, as described in a study, proved to be a pure lithium ion conductor despite its low lithium ion content.
Researchers called it a “Parasitic Conduction Mechanism” because the LiBH4 acts as a kind of “parasite” instead of a host material.
“This parasitic conduction mechanism has a possibility to be applied in any lithium-ion conductors,” said Hitoshi Takamura, an associate professor at Tohoku University who led the study.
“This mechanism can take place if a small amount of lithium ion can be doped to any oxides, sulfides, halides and nitrides to be a host framework.”
The risk of fire in a battery using the mechanism would end up reduced because of the limited amount of LiBH4, he said.
The battery is still in the research phase. While the researchers have not estimated how much such batteries might cost, Takamura said the lower fire risk would enable a simplified and cheaper cell structure.
The team plans to enhance the prototype battery’s lithium-ion conductivity and explore various doping agents that could optimize the lithium-ion pathways.