Carbon nanotubes could revolutionize lithium-ion batteries, the researchers said

Lithium-ion batteries have now become a major energy storage device, from mobile phones to electric vehicles. Now, research shows how to make them more environmentally friendly and empowered. Using carbon nanotubes, a team of Indian scientists from the University of Clemson in the United States eliminated the need for toxic organic solvents in traditional batteries.

"Lithium-ion battery electrodes have traditionally been made using organic solvents called N- Methylpyrrolidone or NMP. NMP is used because it is highly compatible with aluminum foil coated with battery materials, "explained Lakshman Ventragrada, the lead author of ACS Omega. "NMP is expensive and toxic. In fact, each manufacturing unit usually uses a solvent recovery system that costs more than $1 million to recover the NMP. Our goal is to replace NMP with water and achieve better battery performance. "

Although water has been used as a solvent before, its high surface tension often causes the battery electrode to be separated from the bottom aluminum foil when dry. The team used vertically arranged carbon nanotube forests (atomic thick carbon rolled into cylinders) to coat aluminum foil to achieve cavernous capillary action.

Nanotube Forest

"The carbon nanotube forest is only 10-30 microns long and can be arranged vertically on aluminum. We can grow carbon nanotubes directly on aluminum foil at low temperatures using a special curling chemical vapor deposition process, "explains Professor Ramakrishna Podila, an assistant professor of physics at Clemson University, and the authors of the corresponding paper. Nanotubes can also be sprayed on aluminum. These nanotube coated aluminum foil can be directly integrated into existing lithium ion battery manufacturing units because they do not need to make any changes to existing equipment other than replacing solvents with water. "

The team then used a lithium active material called lithium iron phosphate or LFP to mix with the adhesive in water to make a battery electrode on the aluminum foil coated with carbon nanotubes. The adhesive helps the active material adhere firmly to the foil below.

Battery power and power

During charging, lithium-ion batteries transmit lithium ions from lithium active materials on one side and trap them in graphite electrodes on the other side. During discharge, lithium ions leave graphite and return to lithium-ion active material power supply devices such as mobile phones or laptops. The performance of the battery is measured on two things: energy and energy.

The energy is proportional to the total amount of electricity that the battery can withstand, that is, the amount of lithium ions captured, and the power is related to the speed at which lithium ions can be transmitted in the battery. The need for hours is high power and high energy batteries.

High discharge rate

In conventional lithium ion batteries, high power fast charging heats the electrode and destroys the polymer binder, thereby helping the lithium active material adhere to the aluminum foil. This is one of the most common modes of battery failure and cannot achieve high power without damaging the total energy of the battery. But the team's new battery can withstand high energy (600mA/g or 500 times in 15 minutes) and has an energy density of at least 35-50% higher.

"Our scalable approach to nanotubes has greatly reduced costs. In addition, water is used to make it more environmentally friendly. Because carbon is light, it does not increase the quality of the battery, "Podila added." We hope this will lead to cheaper and better lithium-ion batteries in the future. "

The page contains the contents of the machine translation.