Scientists use

In recent years, the technological advancement of computers and mobile phones is not small, but the ever-increasing screen and dazzling software have made their battery life shorter and shorter. No matter how high the number of pixels or mobile phones, the only unsatisfactory one is the battery. However, a team of researchers at Northwestern University announced that they can improve the performance of lithium-ion batteries through technology. Not only do they have faster charging speeds, they also have longer battery life, and they have more power.

It is reported that the group has published the title "Plane Cavity Made of High-Power Silicon-Graphene Composite Electrode for Lithium-Ion Batteries" in an international journal entitled "Advanced Energy Materials" that focuses on energy-related materials (In-Plane Vacancy-Enabled). Paper on High-Power Si-Graphene Composite Electrode for Lithium-Ion Batteries.

The team confidently stated that using this technology to charge mobile phones, computers, and other batteries, the charging speed is 10 times faster than other current batteries, and it only takes 15 minutes, but the battery power can last for about a week. "Even after 150 recharges or more than 1 year of use or even longer, the battery efficiency is still five times higher than that of lithium-ion batteries on the market today." The team leader, Professor of Northwestern University McCormick School of Engineering and Applied Science Dr. Harold said.

Harold said that the density and activity of lithium ions is the key to this technology, and we have found a way to accommodate more ions and speed up their activities in order to change the overall efficiency of the battery.

In fact, the lithium ion battery is mainly charged between the two ends of the battery, that is, between the positive and negative electrodes. In the current Lithium Battery, the positive electrode preparation mainly uses multilayer carbon-based graphene flakes, and can contain only one lithium atom for every six carbon atoms. As a result, the team tried to use silicon instead of carbon, because each silicon atom can hold 4 lithium atoms, but during the charging process, silicon expands and shrinks violently, causing cracks and rapid loss of charge capacity.

In order to stabilize the silicon, the team sandwiched the clusters of silicon between the flexible graphene sheets, which indirectly held a greater number of lithium atoms on the electrodes, and then used the characteristics of the flexible graphene sheets to accommodate the volume changes of the silicon during charging. . Even if the final silicon cluster breaks, these flexible graphene sheets greatly reduce the capacity loss caused by silicon expansion and contraction.

In addition, charging current speed is the main reason for controlling battery charging time. However, since the graphene sheet is very thin, lithium ions are relatively "crowded" during the movement from the positive electrode to the negative electrode, the speed is limited, and the charging time is naturally long. In response, the team used chemical oxidation processes to pour tens of thousands of 10-20 nanometer pores on the graphene sheet, allowing lithium ions to quickly reach the negative electrode. This shortens the charging time.

Harold estimated that the technology will broaden the road for lithium battery development in the future, from small cell phones to large electric vehicles. "I am convinced that this technology will appear on the market in the next 3-5 years," said Harold.