As is well known, there are two promising approaches to developing next-generation energy storage technologies, involving the use of high-density lithium metal and solid-state electrolytes. Recently, a new study has combined these two directions, achieving an exciting new breakthrough. Reportedly, US scientists have demonstrated how, with the help of electrochemical pulses, stability issues associated with these architectures can be addressed, paving the way for electric vehicles and smartphones with longer runtimes per charge.
This research has been published in ACS Energy Letters, the energy journal of the American Chemical Society.
Some research in this field focuses on the anode, which, as one of the two electrodes in a device, helps facilitate the transport of lithium ions through the liquid electrolyte.
Today's anodes are made from a mixture of graphite and copper, but pure lithium metal is an attractive alternative because it offers the highest energy density of any solid material.
However, integrating lithium metal into batteries has been difficult so far because scientists have encountered a variety of safety issues that have quickly led to their failures.
One approach suggests that replacing liquid electrolytes with solid electrolytes would create batteries better suited for lithium metal. This material crossover is a new focus of work for scientists at Oak Ridge National Laboratory (ORNL), who believe they have found a way to combine them in a stable and durable manner without compromising performance.
In solid-state batteries, fusing materials together is often a tricky task because continuous charge-discharge cycles can cause the joints to become unstable and lead to the formation of voids, which is known as contact resistance.
Applying pressure is one way to solve this problem, but this technique needs to be used periodically while the battery is running and may also cause a short circuit in the battery.
Scientists at ORNL have discovered that when a lithium metal anode is combined with a solid electrolyte, they can eliminate these voids by applying a short, high-voltage electrochemical pulse. These pulses act like a current flowing around the voids, causing them to dissipate and creating wider contact at the material interface.
Since this has no adverse effects on the battery, and the pulse technology can restore the battery to almost its original capacity, scientists envision that one day this technology will provide a feasible way to manage the operation of solid-state lithium metal batteries.
They say this system can provide twice the energy density of current solutions, and is much smaller, meaning electric vehicles can travel farther on a single charge, or smartphones can run for longer periods.
"This approach will enable an all-solid-state architecture without applying external forces that could damage the battery, which is impractical to deploy during battery use," said Ilias Belharouak, co-leader of the project. "During our development, the battery can be manufactured normally, and if the battery becomes fatigued, pulses can be applied to revitalize it and refresh the interface."
Scientists are now continuing to develop this technology by experimenting with more advanced electrolyte materials and exploring how to scale it up to working-scale solid-state battery systems.
