The material on the pencil tip, graphite, has also been a key component of today's lithium-ion batteries. However, as people increasingly rely on such batteries, graphene-based electrodes should be further upgraded. Therefore, scientists have found the core element of the digital revolution-silicon.
(Source: Northwest Pacific National Laboratory)
According to foreign media reports, scientists at the US Department of Energy's Pacific Northwest National Laboratory (PNNL) have found a new method that can take advantage of this promising, but problematic storage Energy ingredients. Silicon is commonly used in computer chips and many other products. Because the charge per gram of silicon is 10 times that of graphite, it has attracted much attention. The problem is that when silicon encounters lithium, it expands sharply, and is too fragile to withstand the pressure when manufacturing the electrode.
To solve this type of problem, PNNL researchers have developed a unique nanostructure that can limit the expansion of silicon while also strengthening it with carbon. The research may provide new electrode material designs for other types of batteries, and ultimately help to increase the energy capacity of lithium-ion batteries in electric vehicles, electronic devices, and other devices.
As a conductive and stable carbon, graphite is very suitable for charging lithium ions into the anode during charging. Compared with graphite, silicon can absorb a lot of lithium, but the volume will also expand three times, causing the anode to rupture. The researchers assembled tiny silicon particles into microspheres with a diameter of about 8 microns (about the size of a red blood cell) to create porous silicon.
The researchers said: "For example, solid materials such as stone will break if the volume expands too much. The structure we create is more like a sponge, and there is space inside to absorb expansion."
The study found that when containing more than twice the charge than ordinary graphite electrodes, the thickness of the porous silicon electrode changes less than 20%. Unlike the previous porous silicon, thanks to the carbon nanotubes that make the microspheres look like yarn balls, the microspheres also show extraordinary mechanical strength.
The researchers created the structure in several steps by coating carbon nanotubes with silicon oxide. Next, the nanotube was put into an emulsion of water and oil, and then heated to boiling. The researchers said: "When the water evaporates, the silicon oxide-coated carbon nanotubes will condense into a spherical shape. Then, using aluminum and higher heat, the silicon oxide is converted into silicon, and then immersed in water and acid to remove Derivatives." This process produces a powder consisting of tiny silicon particles on the surface of carbon nanotubes.
The researchers used an atomic force microscope probe to test the strength of the porous silicon ball, and found that the nano-sized yarn ball would bend slightly under very high compressive force and lose some pores, but it would not break.
This result is a good sign for the commercialization of this material, because the anode material must be able to withstand the high compression force of the roller during the manufacturing process. The researchers said that the next step will be to develop more scalable and economical methods to manufacture silicon microspheres so that a new generation of high-performance lithium-ion batteries can be produced in the future. (Yu Qiuyun)
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