Researchers from China and Germany have announced significant advances in lithium-sulfur battery technology, demonstrating improved stability and performance.
Their study, published in the journal Nature, found that new lithium-sulfur batteries use solid electrolytes, which appear to solve most of the solubility problems of intermediate compounds.
Over the past few decades, lithium has proven to be a wonder material in the world of batteries. This is especially true in the growing world of solid-state batteries. However, while silicon has proven very useful in this role, sulfur can store more lithium than silicon, making it a promising alternative, albeit with challenges.
In particular, researchers focused on sulfur. Sulfur has long been attractive for this research because of its abundance and low cost.
Does the secret of solid-state batteries lie in sulfur?
Despite its potential, sulfur tends to be a poor conductor, creating challenges as sulfur expands during lithium storage.
Sulfur also has an unfortunate tendency to react with lithium to form intermediate compounds that dissolve in most liquid electrolytes. This is not ideal as it leads to inefficiencies such as self-discharge and rapid capacity loss.
These issues severely limit the lifespan of lithium-sulfur batteries to a few hundred cycles. To address these issues, two independent research teams in China and Germany believe they may have made a breakthrough.
The first is the use of sulfur in solid-state batteries. Solid electrolytes tend to have porous atomic structures, allowing the diffusion of ions while restricting the movement of more important sulfur-based intermediates. Another benefit is that charging efficiency is dramatically improved.
This was achieved by developing a glassy mixture of boron, sulfur, lithium, phosphorus, and iodine. The latter turned out to be the “secret sauce” that facilitates the transfer of electrons through redox reactions and increases the reaction rate at the electrode.
The resulting battery demonstrated amazing performance. Even under fast charging conditions (122 degrees Fahrenheit/50 degrees Celsius, fully charged in just over 1 minute), the battery maintained half the capacity compared to slower charging speeds.
Impressive results in tests
It maintained more than 80% of its initial capacity even after 25,000 charge/discharge cycles. This far exceeds the durability of lithium-ion batteries, which degrade after about 1,000 cycles.
Despite these achievements, questions remain about the energy density of lithium-sulfur batteries. The test setup used material combinations such as indium-lithium metal foil and a mixture of carbon-sulfur and glass electrolytes.
Only the weight of sulfur is considered in the reported capacity calculations, leaving uncertainty about the weight and volumetric efficiency of the entire battery.
While these batteries may not be suitable for small applications such as smartphones or electric vehicles, their long lifespan and fast charging capabilities make them ideal for stationary energy storage systems.
Lithium-sulfur batteries have the potential to revolutionize industries that rely on durable, high-performance energy storage solutions if they can be produced in large quantities.
The study was published in the journal Nature.
