Graphene aerogel may help advance the research and development of lithium-sulfur batteries

by:CTECHi     2021-07-27

According to foreign media reports, in order to meet the needs of electrification in the future, it is necessary to develop new battery technologies. One of the options is lithium-sulfur batteries. Compared with lithium-ion batteries, the energy density of such batteries is theoretically 5 times higher. Recently, researchers at Chalmers University of Technology in Sweden, with the help of graphene sponge, used catholyte to make a breakthrough in the research and development of this type of battery.

The researchers’ idea is very novel, using a porous, sponge-like aerogel made of reduced graphene oxide as the independent electrode of the battery, thereby improving Make good use of sulfur and improve utilization.

The traditional battery consists of four parts. First, there are two supporting electrodes covering the active material, namely the anode and the cathode; between them is an electrolyte, usually a liquid, which allows Ions are transferred back and forth; the fourth part is a separator, which acts as a physical barrier to prevent the two electrodes from contacting while allowing ion transfer.

Previously, researchers have tried to combine the cathode and the electrolyte to become a 'catholyte'. This concept helps to reduce the weight of the battery, while at the same time making the charging speed faster and the power supply capacity stronger. Now, thanks to the development of graphene aerogels, the concept has proven to be effective and feasible, and the prospects are very good.

First, the researchers injected a thin layer of porous graphene aerogel into a standard battery box. Carmen Cavallo, the Department of Physics at Chalmers University of Technology and the lead researcher of this research, said: 'The aerogel is a long and thin cylinder. It is sliced u200bu200blike a salami, and then the slice is squeezed into the battery. Then take a sulfur-rich solution, the catholyte, and add it to the battery. The porous aerogel serves as a support and will absorb the solution like a sponge.'

'The porous structure of graphene is the key. It can absorb a large amount of catholyte and obtain enough sulfur to realize the concept of catholyte. This kind of semi-liquid catholyte is very necessary and can be used in the process of sulfur circulation. No sulphur is lost. Since sulphur is already dissolved in the catholyte, it will not be lost due to dissolution.'

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

At present, most commercial batteries are lithium-ion batteries, but the development of such batteries is approaching the limit. In order to meet higher requirements, it is becoming more and more to find new chemical methods. important. The lithium-sulfur battery has many advantages, such as higher energy density. Currently, the best lithium-ion battery on the market has an operating efficiency of 300 watt-hours/kg, and theoretically, the maximum can reach 350/kg. In theory, the energy density of a lithium-sulfur battery is about 1000 to 1500 Wh/kg.

Aleksandar Matic, a professor of physics at Chalmers University of Technology and the leader of the research, said: 'In addition, sulfur is very cheap, rich in reserves, and more environmentally friendly. In addition, lithium ion Batteries generally contain fluorine, which is harmful to the environment, but lithium-sulfur batteries do not.'

So far, the problem with lithium-sulfur batteries is that they are not stable enough, resulting in short cycle life. But when researchers at Chalmers University of Technology tested the prototype of the new battery, they found that the new battery still maintained 85% of its capacity after 350 cycles.

The new design avoids two major problems in the degradation process of lithium-sulfur batteries. One is sulfur dissolved in the electrolyte and lost, and the other is the migration of sulfur molecules from the cathode to the anode. The 'shuttle effect'. In this design, the impact of such problems has been greatly reduced.

However, the researchers pointed out that this technology still has a long way to go before it can fully realize its market potential. Aleksandar Matic said: 'Because the production method of this battery is different from most normal batteries, it is necessary to develop a new production process to realize the commercialization of the battery.'

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