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Researchers from the Massachusetts Institute of Technology’s Department of Material Sciences and Engineering in collaboration with Technische Universität Darmstadt’s Institute of Material Sciences recently discovered the real reason for the formation of dendrites in lithium batteries with solid electrolytes. This research published in Advanced Energy Materials suggests that formation of dendrites in Lithium ion batteries with solid electrolyte could be minimized or potentially eliminated by creating electrode surfaces that are very smooth and defect free.
Lithium ion batteries with liquid electrolyte are widely used to power a variety of electronic devices from cars to phones. Electrolytes, which is the material between the positive electrode (anode) and negative electrode (cathode) serves as a medium for electrons or charged ions to move from one electrode to the other when the battery gets charged or drained.
Liquid electrolytes could be flammable and pose a great safety concern. However, the idea of rechargeable Lithium ion batteries is a great area of interest due to its potential to double the battery’s capacity by using lithium electrodes.
Dendrites are thin, finger like projections of the metal that starts to build from one electrode and have the potential to extend all the way across the electrolyte material and reach the other electrode. If these dendrites reach the other electrode over time, it could short-circuit the battery and cause permanent damage to the battery and the device equipping it.
Formation of dendrites is a major concern in Lithium ion batteries because the formation of dendrites is responsible for some fires caused by Lithium ion batteries. The risks of short circuit by formation of dendrites is the main reason why the development of rechargeable Lithium ion batteries has not been possible.
Even though using Lithium ion batteries with solid electrolyte such as some ceramics have great advantages over the batteries with liquid electrolytes in terms of safety and energy storage capacity, the development of lithium ion batteries with solid electrolytes has been challenging. Dendrite formation is also a major concern in these batteries with solid electrolyte.
Earlier attempts to prevent dendrite formation in lithium batteries with solid electrolyte were focused on finding the right solid electrolyte material that is stiff and not elastic. Therefore, materials with adequate shear modulus, a property of the material’s firmness or squishiness, were investigated so that the dendrites could not pass through the electrolyte material.
The two main kinds of solid electrolyte materials investigated for this purpose include lithium phosphorous sulfide and metal oxides. However, such attempts by various Researchers to find the right solid electrolyte material led to confusing results as the dendrites formation was not able to be prevented.
In order to find out the reason why stiffer solid electrolyte material could not arrest the dendrite formation, the research team, led by MIT’s Yet-Ming Chiang, in their recent study tested samples of four different varieties of solid electrolyte materials and studied how they performed during the charge and discharge cycles. Their research revealed that dendrite formation in solid electrolyte material follow a completely different process than the dendrites formed in liquid electrolyte material.
The current research revealed that the lithium from one of the electrodes begins to deposit through an electrochemical reaction onto any defects such as pits, cracks or scratches that exist on the electrode surface leading to the initiation of dendrite formation by providing a toehold for the metallic deposits. This deposition continues to build up and extend towards the other electrode over time and extend towards the other electrode, causing catastrophic consequences.
Furthermore, this research revealed that the dendrite extension happens from the tip of the dendrite and not from its base. Therefore, the formation of dendrites can be greatly reduced or even potentially eliminated by focusing on creating electrodes with smoother surfaces. Therefore, this group of Researchers added a new dimension to the research focused on eliminating dendrite formation in Lithium ion batteries.
- “Mechanism of Lithium Metal Penetration through Inorganic Solid Electrolytes” L. Porz, T. Swamy, et al. Advanced Energy Materials. (2017). DOI: 10.1002/aenm.201701003.