Researchers at the University of Oxford used advanced imaging to reveal mechanisms that cause lithium metal solid-state batteries (Li-SSBs) to fail.
If these can be overcome, they said, solid-state batteries using lithium metal anodes “could deliver a step-change improvement in EV battery range, safety and performance, and help advance electrically powered aviation.”
As part of the Faraday Institution’s SOLBAT project, researchers from the university’s departments of Materials, Chemistry and Engineering Science, have led a series of in-depth investigations to understand more about how short-circuiting happens when dendrites form.
The group used an advanced imaging technique called X-ray computed tomography at the Diamond Light Source research facility to visualise dendrite failure “in unprecedented detail” during the charging process.
They found that the initiation and propagation of the dendrite cracks are separate processes, driven by distinct underlying mechanisms. Dendrite cracks appear when lithium accumulates in sub-surface pores. When the pores become full, further charging of the battery increases the pressure, leading to the cracking.
Propagation occurs with lithium only partially filling the crack. This is through a wedge-opening mechanism driving the crack open from the rear, they said.
Corresponding author of the study is Sir Peter Bruce, Professor of Materials at the University of Oxford and Chief Scientist of the Faraday Institution. He said: “The process by which a soft metal such as lithium can penetrate a highly dense hard ceramic electrolyte has proved challenging to understand with many important contributions by excellent scientists around the world. We hope the additional insights we have gained will help the progress of solid-state battery research towards a practical device.”
Image: Operando XCT virtual cross-sections during plating of a Li/Li6PS5Cl/ Li cell showing the development of a dendrite crack from initiation through propagation to complete short circuit.
Credit: Nature