In search of a safer lithium-ion battery, a team of engineers at the University of Illinois (UI) proposed a polymer-based solid electrolyte that can not only repair itself, but also be recycled without the need for high temperatures. By using a special cross-linked polymer, the new electrolyte will become harder under heating rather than decomposing.
Lithium batteries are one of the successful models of modern electrical technology. Without them, devices from smartphones to electric cars would be impractical-but they are far from perfect. When a lithium battery with poor quality or inadequate assembly undergoes a regular charge and discharge cycle, needle-shaped or dendritic lithium dendrites are easily formed and grow in the structure of the battery. This will cause this part of the undesirable lithium battery to shorten the service life or electrical short circuit. In extreme cases, it can also damage the battery itself, causing fire and explosion.
Part of the reason for these explosive failures is that lithium-ion batteries use liquid electrolytes – if the battery is severely damaged, it will chemically react with the electrodes. Brian Jing, a materials science and engineering graduate student at the University of Illinois, said that solid polymer or ceramic electrolytes have been considered alternatives, but they tend to melt at the high temperatures generated inside the battery. One way to solve this problem is to use cross-linked polymer strands to produce rubber-like lithium conductors. It has a longer service life than a harder solid electrolyte, but it cannot repair itself and is difficult to recycle.
The UI team developed a method to make crosslinks so that they can exchange reactions and exchange polymer chains between them. This means that the polymer will harden when heated and will self-heal, resulting in a decrease in the growth of dendritic lithium dendrites. In addition, no strong acid or high temperature is required to decompose the polymer. Instead, it dissolves in water at room temperature. However, this technique is not yet practical.
Team leader Christopher Evans said: “I think this work provides an interesting test platform for others. We have used very special chemical properties and very special dynamic bonds in polymers, but we think we can use this platform Reconfigured for use with many other chemical properties to adjust electrical conductivity and mechanical properties.
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