In recent years, many research teams have been working hard to find better solid electrolytes and electrode materials for lithium batteries. A team from MIT has developed a prototype solid-state battery that uses new self-healing materials to overcome some key difficulties in this field, giving it a stable high-capacity storage prospect.
In today’s lithium-ion batteries, as the charge and discharge cycle continues, the liquid electrolyte carries lithium ions back and forth between the positive and negative electrodes. However, as shown in the figure below, the metal electrode (the inner circle with texture) on the gray disk of the solid electrolyte is forming dendrites on its surface, which is a headache for lithium battery researchers. As the dendrites grow, the life and performance of the battery will be greatly affected, and there is even a risk of short circuit failure and fire.
If the electrolyte can be replaced with a solid material, it will not only make the battery safer, but also achieve a higher energy density.
It is reported that the researchers have developed a semi-solid metal electrode made of sodium-potassium alloy and compared it to a dentist’s leak-proof material. While having strong properties, this new material can also flow and form. After adding the right amount of material, it can avoid the formation of tiny cracks (usually present in pure solid but brittle electrode materials) and dendrites when in contact with the solid electrolyte. Then, it is to find an alloy electrode to introduce a liquid phase material that can serve as a self-healing component of the metal electrode. As the battery is cycled, the operating temperature keeps the material in the correct semi-solid state to accommodate up to 20 times the current without forming dendrites.
Currently, researchers have provided two design ideas to avoid dendrite formation, one of which is to directly contact the solid electrolyte with the electrode, and the other is to sandwich the liquid metal alloy between the two. Interestingly, the researchers also proposed a third solution, which can also help prevent the formation of dendrites by integrating a liquid sodium-potassium alloy film into the battery and then sandwiching it between the solid electrode and the solid electrolyte.
If this set of solutions can be transformed, it is expected to be applied to any solid-state lithium-ion battery, and covers a wide range of fields from handheld devices, EV power batteries, and electric aviation.