Researchers from Stanford University and the SLAC National Accelerator Laboratory have identified the cause of short circuits and failures in the development of lithium metal batteries with solid electrolytes. Research shows that these problems are predominantly due to mechanical stress, especially during intensive charging. The findings of this research could have a significant impact on the future of electric cars.
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“Even a slight indentation, bending or twisting of the batteries can cause nanoscopic cracks to open in the materials and lithium to penetrate into the solid electrolyte, leading to a short circuit,” explains William Chueh, a lead author of the research the team has already conducted Published in the journal Nature Energy at the beginning of 2023. Dust or other contaminants introduced during manufacturing can also create enough stress to cause failure.
The problem of solid electrolyte failure is well documented, with theories ranging from inadvertent electron flow to various forces at play. Energy-dense, fast-charging, long-life, non-flammable lithium metal batteries have the potential to overcome key barriers to widespread adoption of electric cars.
Real-time observations provide new insights
Many of the currently leading solid electrolytes are ceramic. These materials enable the lithium ions to be transported quickly and reliably separate the two electrodes that store the energy. They are also fireproof.
However, tiny cracks often develop on ceramic electrolytes, which the researchers have demonstrated in over 60 experiments. These cracks widen during fast charging and allow lithium to enter, which can lead to a short circuit.
The research team used an electrical probe to examine the electrolyte and simulated a miniature battery under fast-charging conditions. Using an electron microscope, they were able to observe the processes in real time. Additionally, the team used an ion beam to analyze exactly why lithium collects in certain places and causes further damage.
Pressure as a decisive factor for short circuits
The key to avoiding short circuits is mechanical pressure. The team found that mechanical stresses such as crushing, bending and twisting significantly increase the likelihood of a short circuit.
A real solid-state battery consists of layers of cathode, electrolyte and anode materials stacked on top of each other. The electrolyte separates the cathode from the anode but allows the lithium ions to transport freely. As soon as the cathode and anode touch each other, a short circuit inevitably occurs.
Basis for the batteries of the future
The study shows that even minimal bends, twists, or a dust particle can cause small cracks through which the lithium eventually shorts the cathode and anode, causing the battery to fail. Thanks to these findings, future battery developments can be made more robust, which could also shorten charging times.
Sources: “Mechanical regulation of lithium intrusion probability in garnet solid electrolytes” (Nature Energy, 2023)
By Philipp Rall
