“Yolks” and “shells” improve rechargeable batteries
https://newsoffice.mit.edu/2015/yolks-and-shells-improve-rechargeable-batteries-0805[font face=Serif][font size=5]Yolks and shells improve rechargeable batteries[/font]
[font size=4]Aluminum could give a big boost to capacity and power of lithium-ion batteries.[/font]
David L. Chandler | MIT News Office
August 5, 2015
[font size=1]A new "yolk-and-shell" nanoparticle could boost the capacity and power of lithium-ion batteries. The gray sphere at center represents an aluminum nanoparticle, forming the "yolk." The outer light-blue layer represents a solid shell of titanium dioxide, and the space in between the yolk and shell allows the yolk to expand and contract without damaging the shell. In the background is an actual scanning electron microscope image of a collection of these yolk-shell nanoparticles.
Image: Christine Daniloff/MIT[/font]
[font size=3]One big problem faced by electrodes in rechargeable batteries, as they go through repeated cycles of charging and discharging, is that they must expand and shrink during each cycle sometimes doubling in volume, and then shrinking back. This can lead to repeated shedding and reformation of its skin layer that consumes lithium irreversibly, degrading the batterys performance over time.
Now a team of researchers at MIT and Tsinghua University in China has found a novel way around that problem: creating an electrode made of nanoparticles with a solid shell, and a yolk inside that can change size again and again without affecting the shell. The innovation could drastically improve cycle life, the team says, and provide a dramatic boost in the batterys capacity and power.
The new findings, which use aluminum as the key material for the lithium-ion batterys negative electrode, or anode, are reported in the journal Nature Communications, in a paper by MIT professor Ju Li and six others. The use of nanoparticles with an aluminum yolk and a titanium dioxide shell has proven to be the high-rate champion among high-capacity anodes, the team reports.
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