Graphene aerogel may help advance the development of 18650 li ion rechargeable battery

According to foreign media reports, in order to adapt to the needs of the electrified future, new battery technologies need to be developed. One of the options is 18650 li ion rechargeable battery, which theoretically have an energy density five times higher than lithium-ion batteries. Recently, researchers at Chalmers University of Technology in Sweden have made a breakthrough in the development of such batteries with the help of graphene sponges and cathode electrolytes.

The researchers' idea is very novel. They use a porous, sponge-like aerogel made of reduced graphene oxide as an independent electrode of the battery to better utilize sulfur and improve utilization.

Traditional batteries consist of four parts. First, there are two supporting electrodes covering the active material, namely the anode and cathode; between them is the electrolyte, usually a liquid, which allows ions to transfer back and forth; the fourth part is the separator, which acts as a physical barrier to prevent the two electrodes from contacting while allowing ions to transfer.

Previously, researchers have tried to combine the cathode and electrolyte into a "cathode electrolyte." The concept helps reduce the weight of the battery while making it faster to charge and more powerful to supply power. Now, thanks to the development of graphene aerogels, the concept has proven to be viable and promising.

First, the researchers injected a thin layer of porous graphene aerogel into a standard battery box. "The aerogel is a long, thin cylinder that is sliced like a sausage, and then the slices are squeezed and put into the battery," says Carmen Cavallo, lead researcher at the Department of Physics at Chalmers University of Technology and the study's lead researcher. "A sulfur-rich solution, the catholyte, is then added to the battery. The porous aerogel acts as a support and absorbs the solution like a sponge."

"The porous structure of the graphene is key, absorbing a large amount of catholyte to obtain enough sulfur to make the catholyte concept work. Such a semi-liquid catholyte is necessary to not lose any sulfur during the sulfur cycle, as the sulfur is already dissolved in the catholyte, so it will not be lost due to dissolution."

In order for the catholyte to play its role as an electrolyte, part of the catholyte is also added to the separator, which also maximizes the battery's sulfur content.

Currently, most commercial batteries are lithium-ion batteries, but the development of this type of battery is approaching its limits. In order to meet higher requirements, it is becoming more important to find new chemical methods. 18650 li ion rechargeable battery have several advantages, such as higher energy density. Currently, the best lithium-ion batteries on the market have an efficiency of 300 watt-hours per kilogram, and in theory, they can reach a maximum of 350 per kilogram. In theory, the energy density of 18650 li ion rechargeable battery is about 1,000 to 1,500 watt-hours per kilogram.

"In addition, sulfur is cheap, abundant and more environmentally friendly," said Aleksandar Matic, professor at the Department of Physics at Chalmers University of Technology and leader of the study. In addition, lithium-ion batteries generally contain fluorine, which is harmful to the environment, while 18650 li ion rechargeable battery do not."

The problem with 18650 li ion rechargeable battery so far is that they are not stable enough, resulting in a short cycle life. But when researchers at Chalmers University of Technology tested the new battery prototype, they found that the new battery still retained 85% of its capacity after 350 cycles.

The new design avoids the two main problems in the degradation of sulfur-lithium batteries, one is the loss of sulfur dissolving into the electrolyte, and the other is the "shuttle effect" of sulfur molecules migrating from the cathode to the anode. In this design, the impact of such problems is greatly reduced.

However, the researchers pointed out that the technology still has a long way to go to fully realize its market potential. Aleksandar Matic said: "Because the production method of this battery is different from most normal batteries, new production processes need to be developed to realize the commercialization of this battery."

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