Scientists with Institute of Solid State Physics under Hefei Institutes of Physical Science reported ways to detect the migration path of lithium dendrite in solid-state electrolyte, and Au-coating strategy to prevent short-circuit in solid-state battery.
As a battery, especially the lithium battery, the top priority goes to avoiding short-circuit. With the carbonate ester-based solvents as the key component of the electrolyte, it is prone to get fire or even explode for the lithium batteries when the short-circuit happen.
Therefore, it is reasonable to substitute the liquid electrolyte with the nonflammable inorganic solid-state electrolyte for improving the security.
Meanwhile, the prevention of short-circuit is also important. The lithium ions tend to form lithium dendrite when they deposit on the anode electrode. And the sharp lithium dendrite may penetrate the electrolyte and cause the short-circuit.
Accordingly, correctly understanding the deposition process of lithium-ion in the solid-state batteries and its influencing factors is important to inhibit lithium dendrite growth and prevent short-circuit.
This work, researchers found a way to address the problem by designing a solid-state battery with a non-symmetrical structure.
And part of the surface was coated with a thin layer of gold, and the difference of lithium-ion deposition on the area with or without Au-coating was distinguished.
Meanwhile, they approached using two mutually perpendicular Li metal strips as counter electrodes on both sides of the electrolyte which could be helpful to observe the migration path of the lithium-ion.
It was clear (as shown in Fig. 1b and 1c) lithium spherical particles could be found in the Au-coating area, while the lithium metal aggregated in the area without Au-coating.
Moreover, with the observation of the cross-section of the electrolyte, the researchers believed that the migration path of the lithium-ion had a relation with the electron distribution in the counter electrode (Fig. 2a).
And the concentrated lithium-ions on one side would divergently transport in the electrolyte and deposit in different forms according to the counter electrodes, for instance, spherical particles in the Au-coating area and irregular aggregation in the area without Au-coating. And the regional enrichment of the lithium deposition may be the immediate cause of the lithium dendrite.
This work provides a theoretical and experimental basis for the improvement of the interfacial properties and safety of all-solid-state batteries.
This study was sponsored by National Key Research and Development Program of China (2017YFA0402800); National Natural Science Foundation of China (51502300, U1967211); Anhui Provincial Natural Science Foundation (1608085QE88); and Hefei Center of Materials Science and Technology (2014FXZY006).
Link to the paper: Intragranular growth and evenly distribution mechanism of Li metal in Li7La3Zr2O12 electrolyte
(a) Schematic illustration of the cell with a non-symmetrical structure; (b, c) The SEM and EDS images of the surface in the Au-coating area; (d) The SEM and EDS images of the surface in the area without Au-coating. (Image by ZHANG Linchao)
The schematic illustration of (a) Li+ migration in the solid electrolyte and the Li metal particles deposit in the surface of the area with and without Au-coating. (Image by ZHANG Linchao)