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　　Scientists develop new polymer that may be used in self-repairing batteries

　　In the quest for safer lithium-ion batteries, a team of engineers at the University of Illinois (UI) has proposed a polymer-based solid electrolyte that not only repairs itself but is also recyclable without the need for high temperatures. By using special cross-linked polymers, the new electrolyte becomes harder when heated, rather than breaking down.

　　Lithium-ion batteries are one of the success stories of modern electrical technology. Without them, devices from smartphones to electric cars would be impractical - but they're far from perfect. When they go through regular charge and discharge cycles, needle-like or dendritic lithium dendrites tend to form and grow in the structure of the battery. This can result in reduced service life or electrical short circuits. In extreme cases, it can also damage the battery itself, causing fires and explosions.

　　Part of the reason for these explosive failures is that lithium-ion batteries use a liquid electrolyte – which can react chemically with the electrodes if the battery is severely damaged. Brian Jing, a materials science and engineering graduate student at the University of Illinois, said 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 rubbery lithium conductors. It has a longer lifespan than harder solid electrolytes, but it cannot repair itself and is difficult to recycle.

　　The UI team developed a way to make cross-links so that they create exchange reactions and exchange polymer chains between them. This means that the polymer hardens and repairs itself when heated, resulting in less growth of dendritic lithium dendrites. Additionally, strong acids or high temperatures are not required to break down the polymer. Instead, it dissolves in water at room temperature. However, this technology is not yet practical.

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