In late July 2008, a British solar plane flew for three days at high altitude, creating an unofficial flight endurance record. Perhaps little is known, lithium-sulfur (Li-S) batteries have become the greatest technological advancement in their components. One, it powers the aircraft at night, and its efficiency is unmatched even at the top of the battery.
Solar aircraft Zephyr S (picture from the network) Ten years later, the world seems to be waiting for the commercialization of Li-S batteries. The breakthrough of researchers at Drexel University has just eliminated the huge obstacles that hinder its survival.
Technology companies have learned the fact that the development of laptops, mobile phones and electric vehicles depends on a steady improvement in battery performance. Technology can only be pushed forward if the battery allows it. Lithium-ion batteries are currently considered Is the best battery on the market - is reaching the limit of improvement.
As battery performance approaches stability, some companies are trying to reduce the size of internal components that do not contribute to energy storage by squeezing, in order to plug the last volt into the storage device. These structural changes can have some unfortunate side effects. For example, a series of explosion accidents occurred in Samsung mobile phones in 2016.
Samsung mobile phone after battery explosion (picture from the network) Researchers and technology companies are investigating how lithium-sulfur (Li-S) batteries will eventually replace lithium-ion batteries, because this new chemical reaction theoretically puts more energy into a single battery - a measure This is called the energy density in battery development. This improvement brings about 5-10 times the capacity of a lithium-ion battery, which is equivalent to a longer battery running time between this charge and the next charge.
The problem is that the Li-S battery cannot continue to maintain its superior capacity after the first few charges have been completed. It turns out that sulfur, as a key component in increasing energy density, will be in the form of an intermediate of 'polysulfide' from the electrode. Migration, resulting in loss of this key component and performance degradation during recharging.
Scientists have been trying to stabilize these polysulfide reactions inside Li-S batteries for years, but most attempts have other complications, such as adding weight to batteries, requiring expensive materials or adding several complicated processing steps. But now a new method has been born. A study by the Drexels School of Engineering in the latest issue of the Journal of Applied Chemistry and Interfaces of the American Chemical Society is titled 'Titanium Dioxide (TiO) Nanofibers as Li Report on polysulfide fixatives in -S batteries: Evidence of Lewis acid-base interactions, suggesting that it can hold polysulfides in place, maintaining the impressive endurance of such cells while reducing overall weight and producing them Time required.
We have created Freestanding porous titanium oxide nanofiber mat As the cathode material in lithium-sulfur batteries, Dr. Vibha Kalra said. He is an assistant professor at the School of Engineering, the main research author. 'This is a major development because we found our titanium-sulfur cathode to have high conductivity. , capable of combining polysulfide through strong chemical interactions, which means it can enhance the specific capacity of the battery while maintaining its impressive performance. We can also prove that this can completely eliminate the binder and set on the cathode side. Electrical appliances, which account for 30-50% of the weight of the electrode - our method takes only a few seconds to form a sulfur cathode. The current standard may take up to half a day.'
Their results show that the nanofiber mat is similar to the nest at the microscopic level and is an excellent sulfur cathode platform because it can attract and capture the polysulfide produced by the battery. Keeping the polysulfide in the cathode structure prevents the shuttle. This is a performance degradation that occurs when they are dissolved in the electrolyte solution in which the cathode and anode are separated from the battery.
According to Kalra, this cathode design not only helps the Li-S battery maintain its energy density, but it also achieves this without adding additional materials that lead to increased weight and production costs.
To achieve these dual goals, the team conducted an in-depth study of this, including reaction mechanisms and polysulfide formation to better understand how electrode host materials help them.
This study shows that there is a strong Lewis acid-base interaction between titanium oxide and sulfur in the cathode, which prevents polysulfide from entering the electrolyte, which is the main reason for the decline in battery performance. One of the authors, Kalras Lab Dr. Arvinder Singh, a postdoctoral researcher, said.
This means that their cathode design can help Li-S cells maintain their energy density - and without additional materials to increase weight and production costs, Kalra. Kalras' previous research on nanofiber electrodes shows that they have multiple advantages Overcurrent battery packs. They have a larger surface area than the current electrode, which means they can accommodate expansion during charging, which increases the storage capacity of the battery. By filling the electrolyte gel, they eliminate flammable components in the device. , minimizing their sensitivity to leaks, fires and explosions.
They are created by an electrospinning process that looks like making marshmallows, which means they have an advantage over standard powder-based electrodes, which require insulation and adhesive chemicals that can degrade performance during production. .
Electrospinning creation process , looks like making marshmallows. (Image from the web) To produce a binder-free, stand-alone cathode platform to improve battery performance, Kalras Labs developed a rapid sulfur deposition technology that adds sulfur to its substrate in just five seconds.
'This program melts sulfur into nanofiber mats in a light pressure environment of 140 degrees Celsius - without time-consuming processing or using mixed toxic chemicals, while improving the effectiveness of the cathode after prolonged use. Our Li- The S electrode provides the correct structure,' Kalra said, 'minimizing capacity degradation during battery cycling, which is one of the main obstacles to the commercialization of Li-S batteries.'
'Our research shows that the continuous effective capacity of these electrodes is four times that of current lithium-ion batteries. Our novel, low-cost method can produce a sulfide cathode in seconds, which eliminates major manufacturing obstacles.'
Whether it's the development of laptops, mobile phones or electric cars, it depends on the steady improvement of battery performance. Technology can only be pushed forward when the battery allows, lithium-ion batteries - currently considered to be the best battery on the market - Reach the limits of improvement. (Image from the web)
Since the record-breaking flight of the Zephyr-6s solar-powered aircraft in 2008, many companies have invested in the development of Li-S batteries, hoping to increase the life of various electric vehicles, enabling mobile devices to last longer during the charging interval, and even help the entire energy source. The network adapts to the intermittent nature of wind and solar energy. Kalras' work now provides a development path for this battery technology that can break through a series of obstacles.
The team will continue to develop its Li-S cathode with the goal of further improving cycle life, reducing polysulfide formation and reducing costs.
