Prevent the next generation of lithium battery from short-circuit research team to develop semi-solid electrode

In order to break through the boundaries of battery design and accommodate more and more electricity and energy in a given space or weight, researchers are exploring a more promising technology to use a solid electrolyte material between the two electrodes of a lithium-ion battery. instead of electrolyte.

However, there has always been a problem with this kind of battery, that is, metal dendrites will be formed on one of the electrodes, which will eventually connect the electrolyte and short-circuit the battery. According to foreign media reports, researchers at (MIT) and other institutions at the Massachusetts Institute of Technology have found a way to prevent the formation of dendrites, which is expected to enhance the potential of this new type of high-power battery.

MIT's participants in the study included graduate students Richard Park, professors Yet-Ming Chiang and Craig Carter, while the rest of the researchers were from Texas Agrim University, Brown University (Brown University) and Carnegie Mellon University (Carnegie Mellon University).

Solid-state battery has both safety and energy density, so this technology has attracted much attention. But researcher Yet-Ming Chiang said: "the only way to achieve energy density is to use metal electrodes." A good energy density can be obtained by coupling the metal electrode with the liquid electrolyte, but the same safety advantage can not be obtained compared with the solid electrolyte. Solid-state batteries make sense only by using metal electrodes, but the development of such batteries is hindered by the growth of dendrites, which will eventually fill the gap between the two electrode plates, resulting in a short circuit of the battery. It is well known that in the case of fast charging, the greater the current, the faster the dendrite is formed. At present, the current density of experimental solid-state batteries is much lower than the demand of commercial rechargeable batteries. But the researchers believe that its development prospects are good, because the experimental version of the battery can store almost twice as much energy as traditional lithium-ion batteries.

The team took a compromise between solid and liquid to solve the dendrite problem. The researchers make semi-solid electrodes that come into contact with solid electrolyte materials. Semi-solid electrodes can provide a self-repairing surface at the interface rather than a solid brittle surface, which may cause tiny cracks and lay the groundwork for the formation of dendrites.

The inspiration comes from experimental high-temperature batteries, in which one or two electrodes are made of molten metal. According to reports, this kind of molten metal battery can reach a temperature of hundreds of degrees Celsius and cannot be used in portable devices. However, through this work, it can be seen that the liquid interface can achieve high current density without the formation of dendrites. "the starting point is to develop electrodes based on carefully selected alloys to introduce a liquid phase that can be used as a self-repairing component of metal electrodes," said researcher Richard Park.

The material is not so much a liquid as a solid, but similar to the amalgam solid metal that dentists use to fill cavities, it can still flow and form. In this case, it is made of a mixture of sodium and potassium and is in a state of both solid and liquid phase at normal battery operating temperature. The research team proved that the operating current of the system could be 20 times larger than that of solid-state lithium without the formation of any dendrites. The next step is to replicate this performance with actual lithium-containing electrodes.

In the second version of the solid-state battery, the team introduced a very thin layer of liquid sodium jia alloy between the solid lithium electrode and the solid electrolyte. The results show that this method can also overcome the dendrite problem and provides another way for further research.

The researchers say the new method is suitable for many different versions of solid-state lithium batteries. The team's next step will demonstrate the applicability of the system to a variety of battery architectures.