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Carbon Nanotube Film Modification Solid-state Lithium Battery Power Is Increased By 3~5 Times

- Nov 14, 2018 -

The technological development of lithium batteries has not made breakthrough progress for many years. The reason is that it is difficult to ensure the material to be safely, stably, and rapidly recharged and discharged while increasing the capacity density. The culprit responsible for the decay is the lithium crystal branches on the microstructure. These sharp needle-like structures may pierce the diaphragm of the cell, causing a short circuit or even a fire. One way to limit its growth is to control the battery's charging rate. But at a time when the pace of life is accelerating, such compromises are unacceptable.
The good news is that scientists at Rice University have found a good way to double the capacity of currently widely used lithium-ion batteries.
This breakthrough in battery technology has focused on a new type of anode material that is coated with carbon nanofilm. Previously, some laboratories used Kevlar fiber to limit the growth of crystal branches, or to use a new type of electrolyte (a chemical solution carrying a charge). As early as last year, the same research team at Rice University had developed a lithium metal battery made of asphalt. It charges faster and is more resistant to the formation of crystal branches. Now, the research team goes one step further and introduces carbon nanofilms into it. It is used to coat the lithium metal anode of the battery for more efficient immersion of the crystal branches, similar to holding heavy objects on the lawn to suppress weeds.

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This film absorbs lithium ions from the anode and distributes them during charging. But all of this will not affect the battery charging rate. Research co-author Rodrigo Salvatierra said that the role of the carbon nanotube film is to spread the deposited lithium metal to form a smooth layer without crystal branches. Such improvements do not limit the charging rate of such batteries, and even use high rate charge and discharge with confidence. After deploying the new components to last year's asphalt-lithium batteries, the researchers found that they were able to prevent the growth of crystal branches after more than 580 cycles. In addition, the coulombic efficiency of the battery is maintained at 99.8%, and the finished product is also easier to build.

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The left is Rice University chemist James Tour, graduate student Gladys López-Silva, and postdoctoral researcher Rodrigo Salvatierra. But Salvatierra explained that it has some differences compared to earlier asphalt batteries. First, we used a carbon nanotube film to modify the solid lithium metal foil. These two materials have already been prepared for use in batteries. Second, in pitch-derived electrodes, lithium metal must be electrochemically deposited for use in a complete battery unit. In the end, batteries with this new anode can store 3 to 5 times more power than commercially available products. Even if it is left for one month, its charge loss is negligible. In other words, it will be a reliable long-term energy storage solution. Details of the study have been published in the recently published Advanced Materials journal. Original title: "Suppressing Li Metal Dendrites Through a Solid Li‐Ion Backup Layer".