From：CTECHI GROUP Limited Release time：2018-11-02
Overview：Lithium-ion batteries have brought revolutionary changes to mobile electronic devices and are making progress in transportation. However, to further improve the service life and power of batteries, new technologies are needed. One option is lithium metal batteries, which have longer service life and faster charging speed, but this technology has problems. Lithium deposits (commonly known as lithium dendrites) tend to grow on the anode, which may lead to short circuit, leading to battery failure, ignition or explosion.
Lithium-ion batteries have brought revolutionary changes to mobile electronic devices and are making progress in transportation. However, to further improve the service life and power of batteries, new technologies are needed. One option is lithium metal batteries, which have longer service life and faster charging speed, but this technology has problems. Lithium deposits (commonly known as lithium dendrites) tend to grow on the anode, which may lead to short circuit, leading to battery failure, ignition or explosion.
Now, researchers from the Institute of Chemistry, Chinese Academy of Sciences, Nnkaai University, Shantou University and China Advanced Research Center for High Pressure Science and Technology have designed a diaphragm based on carbon allotrope (called graphite alkyne), which can be used as a lithium ion filter to prevent dendrite growth. Researchers published this research achievement in the "Materials Today Energy" magazine.
Lithium metal batteries are conceptually similar to commercial lithium ion battery for ebikes, but rely on lithium metal anodes. During discharge, the lithium metal anode provides electrons through the external circuit to the cathode. However, when charging, lithium metal will be deposited on the anode. It is in this process that dendrites can form.
This is where the diaphragm works. The thin diaphragm is made of ultra-thin graphite (10nm), which is a two-dimensional hexagonal monolayer of carbon atoms linked by butadiene bonds, and has some remarkable characteristics. Graphite alkynes not only have flexibility and robustness, but also have a uniform porous grid, allowing only one lithium ion to pass through each pore. This regulates the movement of ions through the thin film, so that the diffusion of ions is highly uniform. It is important for the battery to suppress the growth of lithium dendrite effectively.
"Inhibition of lithium dendrites can stabilize the solid electrolyte mesophase, thereby improving the life and Coulomb efficiency of the device," explained Li Yuliang, of the Institute of Chemistry, Chinese Academy of Sciences. "It can avoid dendritic short crystals of lithium dendrites, thereby improving the safety of batteries."
Researchers believe that graphene films can overcome the long-standing problems faced by lithium and other alkali metal batteries, such as lithium dendrites.
"Graphite alkyne is a perfect material with super conjugated structure, inherent band gap, natural macroporous structure and semiconductor characteristics, which offers great hope for solving major scientific problems in this field." Li said.
This two-dimensional material is also very simple and easy to produce under normal laboratory conditions.
"Although more efforts are needed to improve the quality of large-scale graphyne films, we believe that graphyne may lead to some major breakthroughs in the safety of lithium batteries." Li said.
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