UNIST Develops Sensor Technology to Detect Early Signs of Short Circuits in 'Game-Changer' All-Solid-State Batteries

Pressure and Displacement Asymmetry During Vertical Lithium Growth
Published in ACS Energy Letters

A new technology has been developed that allows for the early detection of precursor symptoms of short circuits in all-solid-state batteries by attaching sensors to the batteries.

The research team led by Professor Hyunwook Lee from the Department of Energy and Chemical Engineering at UNIST announced on July 15 that they have developed a technology to detect the formation of lithium dendrites in advance by attaching a pressure sensor and a displacement sensor to the exterior of all-solid-state batteries.

Researchers, Professor Hyunwook Lee (left) and Researcher Sunjae Jeong (first author). Provided by UNIST

All-solid-state batteries are next-generation batteries that replace volatile liquid electrolytes with solid ones. While the risk of explosion and fire is significantly reduced, the possibility of short circuits that can render the battery inoperable still exists.

A short circuit occurs when needle-shaped lithium dendrites penetrate the electrolyte. All-solid-state batteries that use lithium metal as the anode material are more prone to dendrite growth.

These dendrites form during the charging process when lithium metal accumulates in the 'vertical' direction on the electrode. In a normal charging process, lithium metal is evenly plated in the 'horizontal' direction on the electrode surface.

The research team developed a technology to detect dendrites early by attaching a pressure sensor and two displacement sensors to the battery cell. The principle is to detect minute volume changes occurring inside the battery cell when dendrites form. When vertical growth occurs, pressure changes sharply, and the difference in cell thickness measured by the displacement sensors attached to both sides of the cell is significant.

This analysis method also helped identify conditions that can suppress dendrite formation. Finished batteries are structured by stacking cells, and increasing the stack pressure from above is one approach. Additionally, coating the anode surface with silver or magnesium, which mix well with lithium, also suppressed dendrite formation.

The method of increasing pressure was effective not only for lithium anodes but also for silicon composite anodes used in commercial batteries. When a pressure of more than 20 MPa (megapascals) was applied, lithium was uniformly inserted into the anode, achieving a coulombic efficiency of 99.7 percent. This indicates minimal lithium loss, resulting in high charge-discharge efficiency and a long lifespan.

A section precursor symptom diagnosis method that reads pressure and displacement changes in all-solid-state batteries.

Professor Hyunwook Lee explained, "All-solid-state batteries have a low risk of explosion because they do not contain volatile electrolytes. However, if lithium dendrites penetrate the solid electrolyte, an internal electrical short circuit can occur." He added, "This study provides a quantitative standard for diagnosing such risks in advance. The ability to monitor the directionality and uniformity of plating in real time can serve as a crucial foundation for improving the safety and commercialization of all-solid-state batteries."

The research findings were published online in the international journal ACS Energy Letters on June 10, and the paper was selected as the most viewed article over the past month.

The research was supported by Hyundai Motor Company and the National Research Foundation of Korea under the Ministry of Science and ICT, among others.

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