Researchers at the University of California San Diego developed an ultrasound emitter that can be used in a high energy lithium metal batteries to make it charge quickly and safely. The device can be used in any battery, regardless of chemistry and has been licensed to Matter Labs, a technology development firm based in Ventura, California on a non-exclusive basis.
The device emits ultrasound waves inside the battery to create a circulating current in the electrolyte liquid found between the anode and cathode. This prevents the formation of the lithium metal dendrites that lead to short circuits and fires and allows faster charging safely.
The emitter is made from off-the-shelf surface acoustic wave (SAW) components used in mobile phones that generate sound waves at 100MHz. In phones, these devices are used mainly to filter the wireless cellular signal and identify and filter voice calls and data. By propagating ultrasound waves through the battery, the device causes the electrolyte to flow, replenishing the lithium in the electrolyte and making it more likely that the lithium will form uniform, dense deposits on the anode during charging.
“Advances in smartphone technology are truly what allowed us to use ultrasound to improve battery technology,” said James Friend, professor of mechanical and aerospace engineering at the Jacobs School of Engineering at UC San Diego.
The SAW emables lithium cells to operate at higher currents up to 6 mA/cm2 in a commercial carbonate‐based electrolyte, compared to a standard cell that sees short circuits occuring at 2 mA/cm2. The SAW filter itself consumes 10 mWh/cm2, and is only used during the charging cycles. As a result, the researchers showed that a lithium metal battery equipped with the ultrasound emitter could be charged and discharged for 250 cycles and a lithium ion battery for more than 2000 cycles. The batteries were charged from zero to 100 percent in 10 minutes for each cycle. “This work allows for fast-charging and high energy batteries all in one,” said Ping Liu, professor of nanoengineering at the Jacobs School. “It is exciting and effective.”
The most difficult part of the process was designing the device, said An Huang, a Ph.D. student in materials science at UC San Diego. The challenge was working at extremely small scales, understanding the physical phenomena involved and finding an effective way to integrate the device inside the battery.
“Our next step will be to integrate this technology into commercial lithium ion batteries,” said Haodong Liu, nanoengineering postdoctoral researcher at the Jacobs School.