Electrochemical pulses bring solid-state electrolytes together

Scientists at the US Department of Energy’s Oak Ridge National Laboratory (ORNL) have developed a scalable, low-cost method for improving the joining of materials in solid-state batteries, resolving one of the big challenges in the commercial development of safe, long-lived energy storage systems.

Solid-state batteries incorporate a safer, fast-charging architecture that features a solid-state electrolyte rather than the liquid electrolytes used in today’s lithium-ion batteries. A successful solid-state commercial battery system could provide at least two times the energy density of lithium-ion batteries in a much smaller footprint, vastly improving the driving range of electric vehicles, for instance.

One of the challenges of manufacturing solid-state batteries is the difficulty in getting materials to properly join and remain stable during repeated cycles of charging and discharging. Scientists studying methods in the lab to overcome this challenge, called contact impedance, have so far focused on applying high pressures. But that can lead to shorting, and the pressure would need to be re-applied periodically to extend the battery’s life, adding expense.

So the ORNL scientists instead tried using an electrochemical pulse, finding that it can eliminate the voids that form when joining layers of lithium metal anode material with a solid electrolyte material – in this case the ceramic garnet-type electrolyte LALZO (Li_6.25Al_0.25La₃Zr₂O₁₂). Applying short, high-voltage pulses led to increased contact at the interface of the materials while resulting in no detrimental effects, as the scientists report in a paper in ACS Energy Letters.

The non-destructive, low-cost pulsing method results in a local heat-generating current that surrounds the lithium metal-encased voids and causes them to dissipate. The team repeated the experiments and performed advanced characterization of the materials, which revealed that the battery components did not degrade after applying the pulsing method. This approach could be scaled to allow the solid-state battery to be removed and refreshed, bringing it back to nearly the original capacity.

“This method will enable an all-solid-state architecture without applying an extrinsic force that can damage the cell and is not practical to deploy during the battery’s usage,” said Ilias Belharouak, co-lead on the project and head of the Electrification Section at ORNL. “In the process we’ve developed, the battery can be manufactured as normal and then a pulse can be applied to rejuvenate and refresh the interface if the battery becomes fatigued.”

The idea for the method came from previous work where ORNL battery researchers used electrochemical pulses to heal the damaging dendrites that can form in solid electrolytes.

This research is ongoing, including experiments with more advanced electrolyte materials. ORNL’s multidisciplinary energy storage team is also working to scale up its breakthroughs by developing a working-scale solid-state battery system.

“Sometimes the things you see developed at the laboratory scale don’t end up working well together when you put them into cell architecture,” Belharouak said. “At ORNL, we try to build practicality into our work, using our deep bench of scientists and engineers to address the science gaps across scales for an approach that can be readily adopted by industry.”

This story is adapted from material from ORNL, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.