Researchers in Australia claim to have paved the way for the new generation of the batteries that might enable an electric car to travel from the Melbourne City to Sydney City on a single charge. A tablespoon of sugar was the most crucial element.
Lithium-ion batteries, which were first commercialized in the 1990s, are often used in mobile phones, electric vehicles (EVs), and other consumer devices. They’re created with hazardous and rare materials like manganese, cobalt, and nickel which are in low supply all around the planet.
On the other hand, lithium-sulfur batteries use less expensive, more abundant ingredients and can store 2 to 5 times more energy for every kilogram than the lithium-ion batteries. However, there is a catch: they degrade quickly while being recharged. Monash University researchers claim to have discovered a way to ensure lithium-sulfur batteries that can be recharged 1,000 times.
Their findings were published in journal Nature Communications this week. Furthermore, they claim that the batteries are substantially less expensive to manufacture than their lithium-ion counterparts. This is how they function.
The issue of the ‘polysulfide shuttle.’
When the positively charged lithium ions get absorbed by a sulfur-particle electrode in the lithium-sulfur battery, energy is then stored. When completely charged, the electrode swells to approximately double its original size, then diminishes when it is discharged. The electrode weakens and distorts due to expansion and contraction generated by the charging and recharging cycle; this is the first explanation why the battery’s efficiency degrades so quickly. The second cause is the difficulty of the “polysulfide shuttle.”
When lithium ions get absorbed by the sulfur electrodes, they react to generate polysulfides, which are lithium-containing sulfur compounds. The cathode (which is the positive terminal whenever the battery is discharging) gradually degrades as sulfur is removed. According to the Monash researchers, the polysulfides subsequently create a “mossy growth” on the anode (that is, the negative terminal whenever it is discharging). This insulates the anode, causing the battery’s performance to deteriorate. Whereas most lithium-ion batteries are rated to last between 500 – 1,500 charge loops, lithium-sulfur batteries are only rated to last about 50.
In a 30-year-old geochemical paper, a solution
The Monash results clearly demonstrated a partial answer to the cathode problem last year. They increased the battery’s longevity to 200 charge cycles by constructing a springy matrix of sulfur and carbon compounds that could contract and expand without deformation or fracture.
However, the polysulfide shuttle issue remained; as per Mainak Majumder, a co-author of the study, the answer was suggested by an unusual source. Yingyi Huang, a Ph.D. student of Professor Majumder, discovered a geochemistry paper from the late 1980s that described how sugar might assist soil to retain sulfur molecules.
He said adding a “glucose-based additive” to the springy cathode matrix “stabilized” the sulfur, preventing it from spreading and coating the lithium electrode. It also improved the cathode’s web-like structure, “opening up” the matrix so that more lithium ions could interact with the sulfur.